DESIGN STANDARD DS 40-09

Information and Technology Group Operational Technology

DESIGN STANDARD DS 40-09

Field Instrumentation

VERSION 1 REVISION 2

JUNE 2021

Design Standard No. DS40-09 Field Instrumentation

Uncontrolled if Printed Page 2 of 75 Ver 1 Rev 2

© Copyright Water Corporation 2021

FORWARD

Electrical Design Standards are prepared to ensure that the Water Corporation’s staff, consultants and contractors are informed as to the Water Corporation’s design standards and recommended practices. Design standards are intended to promote uniformity so as to simplify design and drafting practice and have as their ultimate objective the provision of safe and functional plant at minimum whole of life cost.

The Water Corporation design standards and recommended practices described in this design standard have evolved over a number of years as a result of design and field experience and these have been investigated and documented.

Users are invited to forward submissions for continuous improvement to the Principal SCADA Engineer who will consider these for incorporation into future revisions.

Manager, Operational Technology

This document is prepared without the assumption of a duty of care by the Water Corporation. The document is not intended to be nor should it be relied on as a substitute for professional engineering design expertise or any other professional advice.

Users should use and reference the current version of this document.

© Copyright – Water Corporation: This standard and software is copyright. With the exception of use permitted by the Copyright Act 1968, no part may be reproduced without the written permission of the Water Corporation




REVISION STATUS

The revision status of this standard is shown section by section below. It is important to note that the latest revisions including additions, deletions and changes to this version of the standard are also identified by the use of a vertical line in the left hand margin, adjacent to the revised section.

REVISION STATUS SECT. VER./

REV. DATE PAGES

REVISED REVISION DESCRIPTION (Section, Clause, Sub-Clause)

RVWD. APRV.

1 1/0 14/05/18 All New standard (replaces DS25-01)

JB RP

1/2 4/3/21 9 Section 3.1.1 Drawing References added

LR

1/2 4/3/21 10-13 Other references updated LR 2 1/0 14/05/18 All New standard (replaces DS25-

01) JB RP

2.5.1 1/1 10/09/18 17 Added requirement for FL display on OIPs

JGB RJ

2.14.1 1/1 10/09/18 32 Added requirements for bi-directional flowmeters

JGB RJ

2 1/2 4/3/21 All All sections updated. This section now contains overall requirements for instrumentation, including the Intrinsic barrier requirements

LR JGB

3 1/0 14/05/18 All New standard (replaces DS25-

01) JB RP

3 1/2 4/3/21 All References to general requirements moved to section 2. References to Preferred Equipment List changed to Approved Equipment List

LR JGB

3.1 1/2 4/3/21 All Preferred Instrument table updated

LR JGB

3.2 1/2 4/3/21 All Loop drawing examples added LR JGB 3.4 1/2 4/3/21 All Flow meter pipe length

requirements updated. Drawing references updated. Trailing Wire flow switch requirements added

LR JGB

3.10 1/2 4/3/21 All Anaylser information added LR JGB 4 1/2 4/3/21 All Minor update on references LR JGB




DESIGN STANDARD DS 40-09 Field Instrumentation

CONTENTS Section Page

1 INTRODUCTION ........................................................................................................... 9

1.1 Purpose .......................................................................................................................................... 9

1.2 Scope .............................................................................................................................................. 9

1.3 Standard Instrumentation and Corporation Standard Designs .............................................. 9

1.4 Drawing References: .................................................................................................................... 9

1.5 References ................................................................................................................................... 10

1.6 Definitions ................................................................................................................................... 11

1.7 Standards .................................................................................................................................... 12 1.7.1 Australian and IEC Standards ................................................................................................. 12 1.7.2 ANSI/ISA Standards ............................................................................................................... 13 1.7.3 Water Corporation Drafting Standards ................................................................................... 13

1.8 Units of Measurement ................................................................................................................ 13

1.9 Mandatory Requirements ......................................................................................................... 13

1.10 Acceptance Tests ........................................................................................................................ 13

2 GENERAL DESIGN PRINCIPLES ............................................................................ 14

2.1 Environment ............................................................................................................................... 14 2.1.1 Ambient Conditions ................................................................................................................ 14 2.1.2 Requirements .......................................................................................................................... 14 2.1.3 Hazardous Areas ..................................................................................................................... 15

2.2 Location, Positioning and Accessibility .................................................................................... 15

2.3 Process Connections and Wetted Parts .................................................................................... 16

2.4 Transmitter Requirements ........................................................................................................ 16

2.5 Signal Characteristics ................................................................................................................ 16 2.5.1 Analog Signals ........................................................................................................................ 16 2.5.2 On-Off Signals ........................................................................................................................ 17 2.5.3 Fieldbus Signals ...................................................................................................................... 17

2.6 Display Facilities ........................................................................................................................ 17 2.6.1 General Requirements ............................................................................................................. 17 2.6.2 Analog Displays ...................................................................................................................... 18 2.6.3 Digital Displays ...................................................................................................................... 18 2.6.4 Totalisers ................................................................................................................................. 19 2.6.5 Screen-Based Displays ............................................................................................................ 19

2.7 Instrument Cubicles ................................................................................................................... 19

2.8 Earthing, Noise and Surge Suppression ................................................................................... 19 2.8.1 Earthing ................................................................................................................................... 19 2.8.2 Electrical Noise ....................................................................................................................... 20 2.8.3 Surge Suppression ................................................................................................................... 20




2.8.3.1 General Requirements ....................................................................................................... 20 2.8.3.2 Suppressor characteristics ................................................................................................. 20 2.8.3.3 Analog signals requiring surge suppression...................................................................... 20 2.8.3.4 Digital signals requiring surge suppression ...................................................................... 20 2.8.3.5 Communications cables requiring surge suppression ....................................................... 21

2.9 Instrumentation Supplies .......................................................................................................... 21 2.9.1 Power ...................................................................................................................................... 21 2.9.2 Air ........................................................................................................................................... 21

2.10 Intra-Plant Data Communication Networks ........................................................................... 22

2.11 Instrument Cabling .................................................................................................................... 22 2.11.1 Copper Cables ......................................................................................................................... 22

2.11.1.1 Screening ........................................................................................................................... 22 2.11.1.2 Construction ...................................................................................................................... 22 2.11.1.3 Installation ......................................................................................................................... 22

2.11.2 Optical Fibre Cables ............................................................................................................... 23

2.12 Instrument System Functional Requirements ......................................................................... 23 2.12.1 Application .............................................................................................................................. 23 2.12.2 Analog Signal Integrity ........................................................................................................... 24 2.12.3 Protection ................................................................................................................................ 24 2.12.4 Control Range ......................................................................................................................... 24 2.12.5 Fieldbus Data Integrity ........................................................................................................... 24

2.13 Intrinsic Safety Barriers ............................................................................................................ 24 2.13.1 General .................................................................................................................................... 24 2.13.2 Standards ................................................................................................................................. 25 2.13.3 Categories and Types of Barriers ............................................................................................ 25

2.13.3.1 Categories .......................................................................................................................... 25 2.13.3.2 Types .................................................................................................................................. 25 2.13.3.3 Associated Apparatus ........................................................................................................ 26

2.13.4 IS Loop Equipment ................................................................................................................. 26 2.13.4.1 Simple Apparatus ............................................................................................................... 26 2.13.4.2 Non-Simple Apparatus ....................................................................................................... 26 2.13.4.3 Cables ................................................................................................................................ 26

2.13.5 IS Loop Design ....................................................................................................................... 26 2.13.6 Installation .............................................................................................................................. 27

3 SPECIFIC INSTRUMENTS ........................................................................................ 28

3.1 Preferred Types of Instrument ................................................................................................. 28

3.2 Loop Drawing Examples ........................................................................................................... 33

3.3 Level Instruments ...................................................................................................................... 33 3.3.1 General Requirements ............................................................................................................. 33 3.3.2 Hydrostatic and Differential Pressure Instruments ................................................................. 33 3.3.3 Ultrasonic Level Instruments .................................................................................................. 34 3.3.4 Radar Level Instruments ......................................................................................................... 35 3.3.5 Guided Radar Level Instruments ............................................................................................ 35 3.3.6 Float-Type Level Switches ..................................................................................................... 36 3.3.7 Pressure-Type Level Switches ................................................................................................ 36 3.3.8 Setting of Level Datum ........................................................................................................... 36

3.4 Flow Meters ................................................................................................................................ 36 3.4.1 General Requirements ............................................................................................................. 36

3.4.1.1 Positioning of Flowmeters in Pipes ................................................................................... 36




3.4.1.2 Reducers ............................................................................................................................ 37 3.4.1.3 Positioning of Flumes in Open Channels .......................................................................... 38

3.4.2 Magnetic Flowmeters .............................................................................................................. 38 3.4.2.1 Design and Selection ......................................................................................................... 38 3.4.2.2 Installation ......................................................................................................................... 39

3.4.3 Ultrasonic Flowmeters ............................................................................................................ 40 3.4.4 Head Loss Flowmeters ............................................................................................................ 41

3.4.4.1 Orifice Plate Flowmeter .................................................................................................... 41 3.4.4.2 Venturi Flowmeter ............................................................................................................. 42

3.4.5 Open Channel Flowmeters ...................................................................................................... 42 3.4.5.1 Flume ................................................................................................................................. 42 3.4.5.2 Flow Meter ......................................................................................................................... 42

3.4.6 Thermal Mass Flowmeters ...................................................................................................... 43 3.4.7 Flow Switches ......................................................................................................................... 43

3.4.7.1 Paddle Type and Trailing Wire Flowswitches ................................................................... 43 3.4.7.2 Thermal Type Flowswitches .............................................................................................. 44

3.5 Pressure Instruments ................................................................................................................. 45 3.5.1 General Requirements ............................................................................................................. 45 3.5.2 Pressure Transmitters .............................................................................................................. 45

3.5.2.1 General Requirements ....................................................................................................... 45 3.5.2.2 Pressure Ratings ................................................................................................................ 45 3.5.2.3 Accuracy ............................................................................................................................ 46 3.5.2.4 Stability .............................................................................................................................. 46 3.5.2.5 Response Time ................................................................................................................... 46 3.5.2.6 Construction Materials ...................................................................................................... 46 3.5.2.7 Process Connection ........................................................................................................... 46

3.5.3 Pressure Switches.................................................................................................................... 47 3.5.4 Pressure Gauges ...................................................................................................................... 47

3.6 Temperature Instruments ......................................................................................................... 48 3.6.1 Temperature Transmitters ....................................................................................................... 48

3.6.1.1 Sensing Element ................................................................................................................. 48 3.6.1.2 Transmitter ........................................................................................................................ 48 3.6.1.3 Accuracy ............................................................................................................................ 48 3.6.1.4 Stability .............................................................................................................................. 48 3.6.1.5 Thermowells ....................................................................................................................... 48

3.6.2 Temperature Switches ............................................................................................................. 48 3.6.3 Temperature Gauges ............................................................................................................... 49

3.6.3.1 Dial-Type Thermometers ................................................................................................... 49

3.7 Density Gauges ........................................................................................................................... 49 3.7.1 General .................................................................................................................................... 49 3.7.2 Nuclear Density Gauges ......................................................................................................... 50

3.7.2.1 Technical requirements ...................................................................................................... 50 3.7.2.2 Installation ......................................................................................................................... 50

3.7.3 Microwave Density Gauges .................................................................................................... 51 3.7.3.1 Technical requirements ...................................................................................................... 51 3.7.3.2 Installation ......................................................................................................................... 51

3.8 Condition Monitoring Instrumentation ................................................................................... 51 3.8.1 General Requirements ............................................................................................................. 51 3.8.2 Application .............................................................................................................................. 52 3.8.3 Sensors .................................................................................................................................... 52

3.8.3.1 Permanently Installed Vibration Sensors .......................................................................... 52 3.8.3.2 Provision for Portable Vibration Sensors .......................................................................... 53




3.8.3.3 Position Sensors ................................................................................................................. 53 3.8.3.4 Bearing Temperature Sensors ........................................................................................... 53 3.8.3.5 Sensor installation ............................................................................................................. 53

3.8.4 Monitoring equipment ............................................................................................................ 53

3.9 Position Instruments .................................................................................................................. 54 3.9.1 Position Sensors ...................................................................................................................... 54

3.9.1.1 General .............................................................................................................................. 54 3.9.1.2 Binary Sensors ................................................................................................................... 54 3.9.1.3 Analog Sensors .................................................................................................................. 54 3.9.1.4 Installation ......................................................................................................................... 54

3.10 Analytical Instruments .............................................................................................................. 55 3.10.1 General .................................................................................................................................... 55 3.10.2 Ammonia Analysers ................................................................................................................ 55

3.10.2.1 Application ......................................................................................................................... 55 3.10.2.2 Requirements ..................................................................................................................... 56 3.10.2.3 Installation ......................................................................................................................... 57

3.10.3 Chlorine Analysers.................................................................................................................. 57 3.10.3.1 Application ......................................................................................................................... 57 3.10.3.2 Requirements ..................................................................................................................... 58 3.10.3.3 Installation ......................................................................................................................... 58

3.10.4 Chlorine Gas Detectors ........................................................................................................... 59 3.10.5 Conductivity Analysers ........................................................................................................... 59

3.10.5.1 Application ......................................................................................................................... 59 3.10.5.2 Requirements ..................................................................................................................... 59 3.10.5.3 Installation ......................................................................................................................... 60

3.10.6 Dissolved Oxygen Analysers .................................................................................................. 60 3.10.6.1 Application ......................................................................................................................... 60 3.10.6.2 Requirements ..................................................................................................................... 61 3.10.6.3 Installation ......................................................................................................................... 61

3.10.7 Flammable Gas Detectors ....................................................................................................... 61 3.10.7.1 Application ......................................................................................................................... 61 3.10.7.2 Requirements ..................................................................................................................... 62 3.10.7.3 Installation ......................................................................................................................... 62

3.10.8 Fluoride Analysers .................................................................................................................. 63 3.10.8.1 Application ......................................................................................................................... 63 3.10.8.2 Requirements ..................................................................................................................... 63 3.10.8.3 Installation ......................................................................................................................... 64

3.10.9 Hydrogen Sulphide Gas Detectors .......................................................................................... 64 3.10.9.1 Application ......................................................................................................................... 64 3.10.9.2 Requirements ..................................................................................................................... 65 3.10.9.3 Installation ......................................................................................................................... 65

3.10.10 Monochloramine Analysers .................................................................................................... 66 3.10.10.1 Application ......................................................................................................................... 66 3.10.10.2 Requirements ..................................................................................................................... 66 3.10.10.3 Installation ......................................................................................................................... 67

3.10.11 pH/ORP Analysers .................................................................................................................. 67 3.10.11.1 Application ......................................................................................................................... 67 3.10.11.2 Requirements ..................................................................................................................... 68 3.10.11.3 Installation ......................................................................................................................... 68

3.10.12 Turbidity / Suspended Solids Analysers ................................................................................. 68 3.10.12.1 Application ......................................................................................................................... 68 3.10.12.2 Requirements ..................................................................................................................... 69 3.10.12.3 Installation ......................................................................................................................... 70




3.11 Control Valves ............................................................................................................................ 70

3.12 Modulating Valves ..................................................................................................................... 70

3.13 Solenoid Valves ........................................................................................................................... 70 3.13.1 Applications ............................................................................................................................ 70 3.13.2 General Requirements ............................................................................................................. 70 3.13.3 Operation ................................................................................................................................ 70 3.13.4 Electrical ................................................................................................................................. 71

3.14 Valve Actuators .......................................................................................................................... 71

3.15 Proportional/Integral/Differential (PID) Controllers ............................................................. 71 3.15.1 Application .............................................................................................................................. 71 3.15.2 General Requirements ............................................................................................................. 71 3.15.3 Specifications .......................................................................................................................... 71

4 DESIGN DOCUMENTATION .................................................................................... 73

4.1 Design Process ............................................................................................................................ 73

4.2 Drawings ..................................................................................................................................... 73

4.3 Schedules ..................................................................................................................................... 73

4.4 Instrument Data Sheets ............................................................................................................. 74




1 INTRODUCTION

1.1 Purpose This document (Design Standard DS 40-09) sets out design standards and engineering practice which shall be followed in respect to the design and specification of instrumentation systems being considered by the Designer in respect to a particular instrumentation system. It does not address all of the issues that will need to be addressed in accordance with the Corporation's operational needs and standard practices. This document shall be read in conjunction with the typical instrument data sheets in T40-03.

It is a Water Corporation objective that its assets will be designed for minimum long-term cost, meet the required standard of quality and are convenient to operate and maintain. In respect to matters not covered specifically in this standard, the Designer shall aim their designs and specifications at achieving this objective.

This design standard is not intended as a type specification for equipment or installation work and shall not be quoted in specifications for the purpose of purchasing instrumentation equipment or systems except as part of the contract specification.

1.2 Scope This design standard covers key aspects of design and equipment selection associated with electronic measurement and control systems including the primary sensing elements, signal transmitters, displays, controllers and control valves.

The design of SCADA systems and control systems for pump stations and treatment plants are covered in other Water Corporation Design Standards.

1.3 Standard Instrumentation and Corporation Standard Designs Instrumentation shall be selected from the OT Approved Equipment List (AEL). Where an instrument is required that is not on the AEL the instrument specification shall be submitted to the Principal SCADA Engineer for approval. The approval process will be conducted by OT Business Unit Strategy and Planning Section.

The Design Standard “DS 60 – Water Supply Distribution - Pipelines Other than Reticulation” shall be referenced for installation of instruments in Distribution Pipelines.

1.4 Drawing References: The following example drawings shall be referenced

Drawing No Description Reference

EG20-004-002 Magnetic Flow Meter Installation – Example Drawing DS-60

EG20-004-004 Magnetic Flow Meter Aluminium Sunshade DN40 to DN300 DS-60

EG20-009-001 Pitometer Point Installation Details DS-60

JZ39-091-010 Flange Isolation Joints DS38-02




Drawing No Description Reference

FQ09-051-001 Tank Level Transmitter Cubicle Layout

DS40-09

FQ09-051-002 Tank Level Transmitter Cubicle Material and Label Schedules and Earthing Diagram

DS40-09

FQ09-051-003 Tank Level Inst. Cubicle Post Mount Details

DS40-09

FQ09-051-004 Tank Level Transmitter with Sensor Cubicle Layout

DS40-09

FQ09-051-005 Tank Level Transmitter with Sensor Cubicle Material and Label Schedules and Earthing Diagram

DS40-09

FQ09-052-001 Tank Level Settings Ground Tank

DS40-09

FQ09-052-002 Tank Level Settings Elevated Tank

DS40-09

FQ09-059-001 Analyser Example Loop Drawing

DS40-09

FQ09-059-002 Flow Modbus Example Loop Drawing

DS40-09

FQ09-059-003 Flow Hart Example Loop Drawing

DS40-09

FQ09-059-004 Water Conveyance Tank Level Example Loop Drawing

DS40-09

FQ09-059-005 Bore Level Example Loop Drawing

DS40-09

FQ09-059-006 Wastewater Wet Well Level Example Loop Drawing

DS40-09

1.5 References Reference should also be made to the following associated design standards and documents:

DS 20 Design Process for Electrical Works

DS 21 Major Pump Stations - Electrical

DS 22 Ancillary Plant and Small Pump Stations - Electrical

https://nexus.watercorporation.com.au/otcs/cs.exe/app/nodes/58556628






DS 24 Electrical Drafting

DS 26 Type Specifications – Electrical

DS 28 Water and Wastewater Treatment Plants - Electrical

DS 40 Design Process for SCADA Works

T40-03 Typical Instrument Data Sheets

DS 41 SCADA Master

DS 42 Communications System

DS 43 SCADA Protocols

SCADA Technical Bulletins

DS 60 Water Supply Distribution - Pipelines Other than Reticulation

Water Corporation Approved Equipment List

DS31-02 Valves and Appurtenances – Mechanical

DS 32 Pump Stations – Mechanical

DS38-02 Flanged Connections

DS70-02 Chlorine Leak Detection Standard

DS80 WCX CAD Standard

DS81 Process Engineering

OT Approved Equipment List

Specification for the Selection of Appropriate Turbidity Analysers

1.6 Definitions Controller - Equipment with inputs and outputs used to automate a process, includes

“PLCs” and “RTUs”

Asset Manager - the Corporation officer responsible for the operation of the asset being acquired.

Corporation - The Water Corporation (of Western Australia)

Designer - the engineer carrying out the particular part of the design.

Design Manager - the Corporation officer appointed to manage the project design process

Principal SCADA Engineer - Principal SCADA Engineer, Operational Technology, Water Corporation



http://aqua/link/?doc=5465593






http://aqua/link/?doc=16977329





1.7 Standards All field instrumentation shall comply with the following standards as applicable or as specified in this Design Standard. In the absence of relevant Australian Standards, other relevant national, international or industry standards shall be followed.

1.7.1 Australian and IEC Standards

Electrical installations associated with instrumentation systems shall be designed in accordance with the relevant sections of AS/NZS 3000, “Wiring Rules”.

All instrumentation equipment shall be specified to conform to the following Australian and IEC Standards:

a) AS 2625.1 "Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts - General guidelines"

b) AS4020 Testing of products for use in contact with drinking water

c) AS 4087 "Metallic Flanges for Waterworks Purposes"

d) AS/NZS 61000.6.4 “Electromagnetic compatibility (EMC) - Generic standards – Emission standard for Industrial environments”

e) AS/NZS 61000.6.2 “Electromagnetic compatibility (EMC) - General standards - Immunity for industrial environments”

f) IEC 60654-1, “Industrial-process measurement and control equipment - Operating conditions - Part 1: Climatic conditions”

g) IEC 60654-4, “Operating conditions for industrial-process measurement and control equipment. Part 4: Corrosive and erosive influences”

h) IEC 60751 “Industrial Platinum Resistance Thermometer Sensors”

i) BS 1041-2.2 Code for temperature measurement. Expansion thermometers. Guide to selection and use of dial-type expansion thermometers

All instrumentation equipment which incorporates electronic switching shall be specified to comply with the Australian Communications and Media Authority (ACMA) Standard AS/NZS 4778:2001 Electromagnetic compatibility for radiocommunications equipment (EN 300 339:1998, MOD) and to be approved by ACMA in this regard.

The following standards are also referred to in this Design Standard:

e) AS/NZS 2312, "Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings"

f) AS 60529, "Degrees of protection provided by enclosures (IP Code)"




1.7.2 ANSI/ISA Standards

Except where specified otherwise in this Design Standard, instrumentation systems shall be designed in accordance with the following ANSI/ISA Standards:

a) ISA-5.1 “Instrumentation Symbols and Identification”

b) ISA-5.3 “Graphic Symbols for Distributed Control/Shared Display Instrumentation, Logic, and Computer Systems”

c) ISA-5.4 “Instrument Loop Diagrams”

d) ANSI/ISA-51.1 “Process Instrumentation Terminology”

1.7.3 Water Corporation Drafting Standards

Drawings documenting the electronic design shall be prepared in accordance with the requirements of DS80 - WCX CAD Standard, DS24 – Electrical Drafting and DS81 – Process Engineering.

1.8 Units of Measurement All physical quantities shall be measured and displayed using the international system of units (SI) in accordance with AS ISO 1000-1998.

1.9 Mandatory Requirements In general, the requirements of this standard are mandatory. If there are special circumstances that would justify deviation from this standard, the matter shall be referred to the Principal SCADA Engineer for consideration. No deviation from the requirements of this standard shall be made without the written approval of the Principal SCADA Engineer.

1.10 Acceptance Tests In tender documents where instrument acceptance tests are specified, the cost of providing a Factory Acceptance Test (FAT) (including associated test certificates) where it is not included in the quotation shall be shown as separate items in the Bill of Quantities so that it can be verified that sufficient funds have been allowed to carry out such testing.




2 GENERAL DESIGN PRINCIPLES

2.1 Environment 2.1.1 Ambient Conditions

As a minimum the instrumentation system design shall be based on environmental conditions determined as follows for each site:

1. Maximum ambient temperature - the maximum average daily temperature as published by the Commonwealth Bureau of Meteorology,

2. Minimum ambient temperature - the minimum average daily temperature as published by the Commonwealth Bureau of Meteorology,

3. Maximum humidity - the maximum monthly average index of humidity as published by the Commonwealth Bureau of Meteorology,

4. Lightning Flash Density - as shown on the Average Annual Lightning Ground Flash Density Map published by the Australian Government Bureau of Meteorology,

5. Corrosion Environment - the ISO environmental corrosion category for the site as defined in AS/NZS 2312,

6. Airborne dust pollution level - severe, moderate, or low as determined for the site bearing in mind proposed operations and future developments,

7. Altitude - site mean height above sea level.

Site environmental conditions will generally be more severe than the values determined above and shall be estimated on the basis of the above values depending on the particular location.

Equipment which is to be installed outdoors shall be suitable for operation in the actual environment without additional protection other than the provision of sunshades. It shall not be necessary to create special environments (e.g. air conditioned or force-cooled enclosures) for field equipment.

In some areas of bore fields, groundwater treatment plants, wastewater pump stations and wastewater treatment plants, traces of hydrogen sulphide (H2S) gas may be present in the atmosphere. Equipment to be located in such areas shall be resistant to attack by airborne H2S.

2.1.2 Requirements

Equipment which is to be located in direct sunlight shall have an operating temperature rating of not less than 10oC above the expected maximum ambient shade temperature.

Equipment which is to be installed in locations subject to flooding shall have an enclosure with degree of protection IP66/68 capable of withstanding a strong jet of water and submersion to a depth of 3 m for a period of up to 24 hours.

Equipment which is to be installed in outdoor locations which are not subject to flooding shall have an enclosure with degree of protection IP66D as a minimum.

Any exposed non-metallic materials used in the construction of outdoor instrumentation equipment and enclosures shall be UV stabilised.




Where instrumentation equipment is located within cubicles having degree of protection IP53 or higher and which allow operator access, the equipment shall have a degree of protection of not less than IP52.

Where instrumentation equipment is located within cubicles having degree of protection IP53 or higher and which do not allow operator access, the equipment shall have a degree of protection of not less than IP2X.

2.1.3 Hazardous Areas

Equipment installed in, or used in conjunction with, hazardous areas shall meet the specifications outlined in Water Corporation standard HA-ST-03 ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS (EEHA) SELECTION AND INSTALLATION STANDARD.

This Standard specifies the general requirements for the selection and installation of electrical equipment for the Water Corporation’s facilities to ensure safe use in hazardous areas. The intention of this Standard is to expand upon the requirements of the AS/NZS2381 and AS1076 series, and to specify additional Water Corporation requirements.

2.2 Location, Positioning and Accessibility Instrumentation equipment shall be located so as to minimise harmful effects of;

• solar radiation

• heat from adjacent equipment

• atmospheric corrosion

• condensation

• spillage

• rain and wash water

• vibration

• mechanical damage

• collision

Instrumentation equipment shall be located so that access way minimum clearances are maintained and so as to avoid damage during mechanical procedures.

Instrumentation equipment shall be located so as to facilitate inspection, testing, calibration and maintenance. Location of instrumentation equipment in confined spaces shall be avoided.

Locally mounted indicators shall be mounted at a height of between 1.4 metres and 1.6 metres above ground or associated permanent platform level.

Instrumentation and any associated equipment valves should preferably be mounted not more than 1.8 m above grade, in cases where this cannot be met, an approved mix of asset-based controls, fall injury prevention systems and administrative controls shall provide an acceptable level of risk. These requirements are elaborated further in the “Prevention of Fall” (Design Standard S151).




Each item of instrumentation shall be spaced at least 100 mm from other items and from any power equipment, except where such items are from the same manufacturer and the manufacturer certifies that closer spacing is permissible.

2.3 Process Connections and Wetted Parts Process connections to instruments shall be NPT based. This is except where process equipment necessitates the use of flanged connections. Where flanged connections are used, they shall conform to the relevant piping specification.

Process connections for pressure transmitters shall also be supplied with a manifold for equalisation and calibration.

Wetted parts and seals of instruments shall be compatible with the fluid and the piping class to which they are connected. Unless there are specific compatibility problems, metallic application shall be 316 stainless steel as a minimum.

Wetted parts in contact with potable water must comply to AS4020.

2.4 Transmitter Requirements Instruments shall be selected such that the output is linear, local indication is in engineering units and normal operating value is within the middle third of the instrument’s range.

Flow instruments shall be able to measure the maximum operating flow.

Pressure instruments shall be able to withstand at least 150% of maximum operating pressure, without damage and shall be capable of continuously withstanding maximum operating pressure without losing calibration.

Transmitters shall be supplied pre-configured, avoiding the need for configuration at site.

2.5 Signal Characteristics 2.5.1 Analog Signals

Analog signals shall be 4 - 20 mA with the negative at earth potential, grounded at one point only. If it is necessary to interconnect grounded 4 - 20 mA signals from separate devices, the connection shall be made via a signal isolator.

Analog signals shall incorporate the HART protocol.

Two-wire signal transmitters shall be rated for operation from a 24 VDC supply. Four-wire signal transmitters shall preferably be rated for operation from a 24V DC supply. Use of 240V 50Hz supply shall need to be approved by the Principal SCADA Engineer.

Analog signal transmitters shall be capable of driving a load of at least 600 ohms. The Designer shall include all devices and cable resistances when calculating total signal loop resistance.

Digitised analog signals for Dam instrumentation shall have accuracy as determined by AMSI (Asset Monitoring and Systems Investigations). All other digitised analog signals shall be minimum equivalent to 12-bit resolution. Preference shall be given to digital data communications signal interfaces which are in accordance with international standards.




Signals from inherently non-linear primary elements such as orifice plates and weirs shall be linearised at the instrument transmitter prior to transmission.

2.5.2 On-Off Signals

Contact outputs on instrumentation equipment shall be rated for the particular duty. Contacts switching shall be less than 200 mA and not more than 24 V. They shall be of the bifurcated gold-plated type. Contact outputs shall be isolated, preferably with each side of each contact brought out separately. Commoning should be avoided.

Reed relays shall not be used in applications where the contacts will remain closed and carrying current for long periods of time.

Repetitive pulse outputs shall be of the solid-state open collector type with facilities for an external wetting supply.

Alarm contacts shall be setup to fail in the alarm or trip condition.

2.5.3 Fieldbus Signals

Modern instrumentation is available with fieldbus connection options which provide access to a range of data and diagnostic information from a single instrument. A fieldbus interface shall be used wherever possible

Fieldbus signals may be required to integrate into a new or an existing plant wide system and should be compatible with the system protocol that is being used. Alternatively on simple sites where single instruments require interfacing, or the plant does not have an existing fieldbus system, a common supported protocol that can be integrated into the control system without the need for redesign or addition of complex components may be utilised.

Examples of approved selections are:

• Plant wide fieldbus – Profibus or Profinet

• Instrumentation fieldbus – Profibus, Profinet, Modbus or HART

Profibus signals shall utilise the standard as defined in the IEC 61158 series of standards.

Refer to DS43-04 for Profinet, Profibus-DP and Profibus-PA Network Design and Installation.

2.6 Display Facilities 2.6.1 General Requirements

Transmitters and converters shall incorporate digital or analog indicators scaled in engineering units. Indicators shall be linear.

The recommended arrangements for full scale values (d) are as follows,

d = x×10n

Where: d = full scale value




x = 1, 2 or 5

n = any positive integer or zero

The base “x” shall be chosen such that the normal process value is between 50 to 80% of full-scale value (d) and d is greater than the maximum process value.

The full-scale value shall apply to the range settings for physical display units as well as ranges set in the Controller and HMI coding.

The possible full-scale values (d) are shown below for n = 0 to 5.

Multiplier (n) Base

(x = 1) Base (x = 2)

Base (x = 5)

0 1 2 5

1 10 20 50

2 100 200 500

3 1000 2000 5000

4 10000 20000 50000

5 100000 200000 500000

Table 1 Scaling values

Thus, if you had a process value, such as flow, where the normal value is 136 L/s and the maximum process value is 150 L/s then the full scale value shall be chosen as “200 L/s” as this is one of the available full scale values as shown in the table above, and the normal value is 68% of the full scale value, thus satisfying the 50% to 80% rule.

Displays shall be clearly readable in the prevailing ambient light conditions. Suitable backlighting or shading shall be provided as necessary to ensure this. HMIs that are mounted outside shall be sunlight readable.

Unless there is a specific need to do so, local instrument displays shall not be duplicated in field-located instrumentation cabinets or switchboards.

2.6.2 Analog Displays

Analog displays and indicators, including bar graph indicators, shall have a resolution of better than 1% of full scale and an accuracy of better than ± 2% of full scale.

Analog indicator dials shall be arranged so that in normal operation the pointer reads at approximately two-thirds full scale. HMI instrument display ranges shall be such that under normal operation the instrument value is approximately two-thirds of the full range of the display.

2.6.3 Digital Displays

Digital displays and indicators shall be minimum the 3.5 digit type, shall have a resolution of better than 1 digit and an accuracy of better than ± 0.1% of reading.




Digital displays and indicators to be installed outdoors shall be of the liquid crystal display (LCD) type and shall be capable of continuous operation in direct sunlight without fading or loss of readability.

Digital displays and indicators to be installed indoors shall be of a luminous display type, e.g. light emitting diode (LED or OLED) or back-lit liquid crystal display (LCD).

2.6.4 Totalisers

Totalisers shall display a minimum of 8 digits, shall retain totals indefinitely during power-off periods and shall not be fitted with mechanical reset.

HMI totaliser values shall be calculated internally within the instrument and the value shall be read by the Controller using fieldbus communications protocols such as: HART, Modbus, Profinet or Profibus.

2.6.5 Screen-Based Displays

All assets on HMI screens shall have the point tag displayed as a tool-tip (pop up when the cursor hovers over the item) or permanently alongside the displayed item if the HMI does not have tool-tip capability.

2.7 Instrument Cubicles Outdoor instrumentation cubicles shall be constructed of either marine grade aluminium or 316 stainless steel and shall be painted, or otherwise coated, gloss white externally. They shall have a degree of protection of not less than IP56.

Spaces within instrumentation cubicles which are accessible to operators shall not include exposed electrical conductors. All other spaces within instrumentation equipment cubicles shall be finger protected.

Except where specified otherwise in this Design Standard, general construction and wiring of instrumentation cubicles shall comply with the Corporation’s Type Specifications parts DS 26-09.

2.8 Earthing, Noise and Surge Suppression 2.8.1 Earthing

A separate instrumentation earth bar shall be provided and shall be bonded directly to the power system protective earth at the main earth bar.

The instrumentation earth shall be connected to the power system protective earth via transient earth clamps with a rated clamping voltage of 90 V ± 20%, an impulse clamping voltage not exceeding 600V at 1kV/µs and a surge current withstand of 20kA (8/20 µs impulse).

Earthing and equipotential bonding shall be provided for metal pipe work and structural metal in the vicinity of instrumentation equipment generally as described in Design Standard DS 21.

Transducers mounted on pipework shall be electrically isolated from the associated pipework and shall be earthed separately to the instrument earth bar.

A separate high integrity earth shall be provided for earthing of all intrinsically safe cable screens, barriers and the like in accordance with AS/NZS 60079.11.




2.8.2 Electrical Noise

All instrumentation equipment shall be specified to comply with the noise emission requirements of AS/NZS 61000.6.4. The design of the installation shall aim to eliminate or suppress electrical noise at the source.

All inductive loads such as solenoids, relay coils and the like that are switched by instrumentation equipment shall be fitted with suitably rated inductive surge suppression diodes.

2.8.3 Surge Suppression

2.8.3.1 General Requirements

Field instruments with integral surge suppressors that comply with the requirements of this section shall be specified in preference to separately fitted suppressors.

Field instrument surge suppressors shall be earthed to the instrument case.

Instrument and communication cables need not be fitted with surge suppression provided that:

(a) The cable is run entirely within the building and the items to which the cables are connected are bonded to the instrument earth;

(b) The cable is run entirely within the building and the equipment manufacturer states that surge suppression is not required.

(c) Optical Fibre cable is used.

2.8.3.2 Suppressor characteristics

Where surge suppressors are required to be fitted to instruments or instrument signal cables, they shall have the following characteristics:

(a) rated operating current not less than 125% of maximum signal current,

(b) rated surge current not less than 5 kA (8/20 µs impulse).

(c) rated voltage for 5 µA leakage not greater than 150% and not less than 110% of the maximum working voltage of the protected device,

(d) residual voltage for a 5 kA 8/20 µs impulse not greater than 130% of suppressor working voltage.

2.8.3.3 Analog signals requiring surge suppression

Analog signal cables with route lengths exceeding 15 metres shall be fitted with surge suppressors at both ends.

Analog signal cables with route lengths not exceeding 15 metres shall be fitted with surge suppressors at the receiving end Controller only.

2.8.3.4 Digital signals requiring surge suppression

Digital signal cables shall be optically isolated at the controlling device.




Surge suppression shall be fitted at the controlling device when the signal cable route length exceeds 15 metres and the isolation rating of the optical isolator is less than 1500 VDC.

Surge suppression is not required for devices having galvanically-isolated output contacts.

Field-mounted surge suppression shall be provided as necessary to protect sensitive devices such as those with open-collector or similar solid-state outputs.

2.8.3.5 Communications cables requiring surge suppression

For copper cables run from a cubicle to the device, surge suppression is required when the signal cable route length exceeds 15 meters.

Profibus surge suppression cabling shall be as specified in DS 43-04 Profibus Standard.

2.9 Instrumentation Supplies 2.9.1 Power

In general, all instrumentation power supplies shall be regulated 24 VDC rated to provide not less than 200% of the initial design load so as to allow for future expansion. Other voltages may only be used if suitable 24 VDC instruments are not available.

Instrumentation supplied from back-up batteries should operate at the battery voltage, suitably rated inverters may be used to supply AC powered equipment only if appropriate DC powered equipment is not available.

In installations supplied from back-up batteries and where more than one DC supply voltage is required (e.g. for electronic equipment or special types of instruments) the battery voltage shall match the highest required voltage and all other DC supplies shall be provided by means of adequately rated DC/DC converters.

Mains power supplies to instrumentation equipment shall be connected via suitably rated three-pole surge filters with a surge current rating of not less than 5 kA (8/20 µs impulse). The surge filters shall be protected by upstream high-power surge diverters in accordance with Design Standard DS 21.

Mains power supplies to large or critical instrumentation systems shall be via a screened isolating transformer, which shall be connected after the UPS if the latter is provided. The transformer case and screen shall be connected directly to the power system earth bar and the secondary neutral shall be connected directly to the instrumentation earth bar. Note that UPSs do not provide noise screening.

For Solar power supply for small sites (e.g. single tank site) please refer to Work Instruction WI 42-03 “Solar Power Design Standalone Photo - Voltaic Panels with Batteries”. For larger sites please refer to DS25 – Solar Energy Systems

Instruments shall be individually fused.

2.9.2 Air

Instrument air supply for process instrumentation, actuated valves and the like shall be at a nominal pressure of 700 kPa, filtered, dried and fitted with a condensate drain..




The instrument air system shall incorporate air receivers with sufficient capacity to allow limited operation and safe shutdown of the plant in the event of plant air system failure.

As a general rule instrument air shall be obtained from the plant air system.

2.10 Intra-Plant Data Communication Networks Intra-plant data communication networks shall be as specified in DS40.

2.11 Instrument Cabling 2.11.1 Copper Cables

2.11.1.1 Screening

All copper analog and high-speed digital signal cables shall be individually and overall screened. Cable screens shall be earthed at the receiving (Controller or IS barrier) end and insulated at the field instrument end.

Analog cables with more than one twisted pair shall have each pair individually screened in addition to the overall screen. The individual screens shall be earthed at the same point as the overall screen.

Cable screening between modules of a particular instrument shall be in accordance with the manufacturer’s recommendations

Cable armouring of non-IS cables shall be bonded to equipment frames at both ends of the cable.

2.11.1.2 Construction

All signal cables other than coaxial shall be individual twisted pairs. Common return wires shall not be used.

Multi-pair cables shall include not less than 20% of spare pairs.

2.11.1.3 Installation

Cabling between the transducer head and the converter/transmitter shall be well separated from variable-speed drive and high voltage power cables, or else shall be enclosed in metallic conduit.

As far as is practical, the minimum separation between power cables and signal cables shall be as stated below:

Example Separation (mm)

Class of Signal

1 Sensitive

2 Slightly sensitive

3 Slightly

interfering

4 Interfering

1 Sensitive

Low level, analog, sensors/probes, measuring, Profibus, Ethernet

-

100

500

1000




Example Separation (mm)

Class of Signal

1 Sensitive


3 Slightly

interfering

4 Interfering


Low level digital, low level DC power supplies, control circuits to resistive loads

100

-

200

500

3 Slightly interfering

Control circuits with inductive loads, clean AC power supplies, main power supplies 0.6/1kV, ≤400A

500

200

-

200

4 Interfering

Switching power supplies, VSD circuits, major LV power circuits,>400A

1000

500

200

-

5 HV Cable

HV cable,(≤33kV),

1000

1000

1000

1000

Table 2 Cable separation requirements

These separation distances may be reduced if separate metallic conduits or metallic (preferably magnetic material) cable trays/ducts are provided for power and/or signal cables. Such separation distances shall be in accordance with the recommendations of IEC 61000-5-2, BS 6739, HB29-2007, AS3080 and reputable company product installation guides.

A minimum separation of 1 m shall be maintained between HV cables and any power or signal cable, no matter what barrier is provided.

Cabling shall be installed in accordance with the Corporation’s Type Specification for Electrical Installations, part DS 26-07.

2.11.2 Optical Fibre Cables

Fibre optic cabling shall be used for communications cables, including Profibus DP cabling, run from cubicle to cubicle, where the cable route is outdoors. Surge suppression is not required for optic fibre cables.

Indoor low-speed communications over route lengths exceeding 150 m and high-speed communications over route lengths exceeding 50 m shall utilise optical fibre cables where possible.

Optical fibre cables shall be installed as specified in Design Standard DS 43-06 Fibre optic network design and installation.

2.12 Instrument System Functional Requirements 2.12.1 Application

This section describes the general functional requirements of instrumentation systems.




The requirements apply particularly to stand-alone systems (e.g. those associated with metering stations, dosing or chemical injection stations and the like). Instrumentation systems that are part of a treatment plant shall conform to Design Standard “DS 40-08 Standard for the Control of Chemical Dosing” in addition to the requirements of this section.

2.12.2 Analog Signal Integrity

Instrument signals shall be checked for integrity by the receiving-end Controller. Any signals that are outside the normal range shall initiate an alarm. In the case of 4 -20 mA analog signals the alarms shall be set to less than 3.5 mA or greater than 20.5 mA.

2.12.3 Protection

Analog input and output circuits shall be protected against reverse polarity connection.

Protective interlocks shall be designed to act on the final actuator as directly as possible.

Where continuity of operation is important, protection circuits shall be designed to provide a warning prior to the associated trip condition being reached, to enable the operator to take corrective action. Operation of protective devices shall be indicated individually.

Unless suitable backup systems are provided, protection circuits and sequence control systems shall be designed to fail to a safe condition in the event of power failure or equipment malfunction.

If failure of instrumentation equipment is considered likely to impair the safety or economic operation of the associated process, the reliability of the equipment shall be assessed to determine if redundancy techniques need to be employed.

2.12.4 Control Range

For on-off control, the deadband between control ranges shall avoid nuisance or high frequency switching; typically it will not be less than 10% of the associated measuring instrument’s full scale measuring range.

2.12.5 Fieldbus Data Integrity

Fieldbus status information, when available, shall be displayed on the HMI system. The status shall be fully expanded for maintenance personnel and use clear English explanations of the different states. This information shall be available via popup or engineering page and not shown directly to the operator.

2.13 Intrinsic Safety Barriers 2.13.1 General

The function of an intrinsic safety (IS) barrier is to limit the available energy in a hazardous area instrument loop to a value less than that capable of igniting the flammable atmosphere while allowing transmission of measurement and control signals. The minimum ignition energy depends on the gas group and is specified in AS/NZS 60079.14 and AS/NZS 60079.11.

An IS system typically comprises the following components:

1. An IS barrier mounted in a non-hazardous area or in a protected enclosure.

2. An instrument or control device installed in the hazardous area.




3. Interconnecting cabling between the barrier and hazardous area device.

The advantage of the Intrinsic Safety technique is that it enables non-certified equipment to be used in the hazardous area, with protection being provided by the IS barrier. This may significantly reduce capital costs.

2.13.2 Standards

Intrinsically Safe (IS) system requirements are defined in the following standards:

• AS/NZS 60079.14 “Explosive atmospheres – Electrical installations design, selection and initial inspection”

• AS/NZS 60079.11, “Explosive atmospheres – Equipment protection by intrinsic safety ‘i’ ”

2.13.3 Categories and Types of Barriers

2.13.3.1 Categories

There are two categories of IS barriers: ‘ia’ and ‘ib’.

Category ‘ia’ barriers are incapable of causing ignition in normal operation with either a single fault or with any combination of two faults applied. Loops protected by ‘ia’ barriers may be used with all gas groups and in all zones.

Category ‘ib’ barriers are incapable of causing ignition in normal operation with a single fault applied. Loops protected by ‘ib’ barriers may only be used in zones 1 and 2.

Since there is generally little or no cost difference between category ‘ia’ and category ‘ib’ barriers, and since category ‘ia’ barriers may be used in all hazardous areas, only category ‘ia’ barriers shall be specified.

2.13.3.2 Types

There are two types of IS barriers: Zener barriers and isolating barriers.

Zener barriers utilise shunt Zener diodes and series resistors to limit the voltage and current that can be applied to the hazardous area circuit. They do not provide galvanic isolation between the safe and the hazardous areas. The common connection must be connected to a high-integrity earth.

Isolating barriers utilise magnetic and/or optical coupling between safe area and hazardous area circuits so that the two sides are galvanically isolated. They do not require a high-integrity earth connection.

Both types of barriers provide a similar degree of safety. The main difference is in the method used to limit the electrical energy that can be applied to the hazardous area. Isolating barriers are generally larger and more expensive than Zener barriers; the choice between them will depend on the application.




2.13.3.3 Associated Apparatus

Barriers are referred to as associated apparatus and are identified by the use of brackets, e.g. Ex [ia] or [Ex ia]. The function of the barrier is to provide protection to equipment installed in the hazardous area. It is important to note that the barrier itself is not protected and must be installed in a safe area.

2.13.4 IS Loop Equipment

Other than the barrier itself, the following types of equipment may be included in an IS instrument loop:

2.13.4.1 Simple Apparatus

Apparatus incapable of generating, storing, or releasing energy in excess of limits defined in the Standards. Examples are switches, pushbuttons, and thermocouples.

Simple apparatus is not required to be certified. However, the Standards apply restrictions to the use of simple apparatus, including restrictions on the use of multiple devices per loop.

2.13.4.2 Non-Simple Apparatus

Non-simple apparatus such as apparatus capable of storing or releasing energy, such as inductors, capacitors, batteries and the like may not be used in IS loops unless it has been appropriately certified.

2.13.4.3 Cables

Due to their inductance and capacitance and depending on their length, cables can store sufficient energy to ignite a flammable atmosphere. Therefore, an IS loop calculation shall be performed to confirm that the stored energy is within safe limits. Calculations shall be carried out in accordance with the relevant Standards.

2.13.5 IS Loop Design

The issues to be considered in the design of IS loops include:

• selection of equipment appropriate to the zone, gas group and temperature class of the hazardous area,

• selection of a barrier that will deliver enough voltage and current to operate the hazardous area device reliably without exceeding its certified maximum limits,

• voltage drop in long loops, which may necessitate the use of appropriately certified loop isolators to re-power the loop,

• energy storage within cabling,

• provision of a high integrity earth,

• segregation of IS and non-IS cabling,

• loop integrity. Some barriers are fitted with inbuilt fuse protection. To ensure that the barrier’s certification is not voided this fuse may only be replaced by the manufacturer. It may be cheaper in the long run to provide a separate external fuse of lower rating than the inbuilt fuse.




2.13.6 Installation

The issues to be considered in the installation of IS loops include:

• earthing shall be in accordance with the relevant Australian standards,

• cable screens shall be earthed to the intrinsically safe earth,

• armoured cable is not mandatory but may be used to provide mechanical segregation from non-IS circuits where required,

• IS and non-IS circuits may not be mixed in the same cable,

• a permanent label shall be fixed adjacent to each IS barrier to identify the correct type of replacement barrier.




3 SPECIFIC INSTRUMENTS

3.1 Preferred Types of Instrument The selection of instruments for specific applications shall be guided by the following general principles:

Instruments shall be selected from the Water Corporation’s OT Approved Equipment List (AEL) as applicable.

If it is proposed to use instruments that are swnot included in the AEL the Designer shall refer the matter to the Principal SCADA Engineer for approval to use, giving reasons for the choice.

Instruments shall be of a recognised brand or the product of a recognised manufacturer.

Instruments shall have a history of successful use in similar applications in the Water Corporation or in the water industry generally.

There shall be good local technical and maintenance support, preferably based in Western Australia or, as a minimum, in Australia.

Electrical cable entries shall be 20 mm ISO female as a minimum.

Instruments shall be suitable for the application, considering such factors as:

• accuracy and repeatability

• compatibility with existing instruments and systems

• ability to withstand service and environmental conditions

• resistance to blocking or fouling

• hazardous area classification

• ease of installation and maintenance

• whole-of-life cost

• intelligence of the device

Specific pump station condition monitoring requirements are detailed in mechanical design standard DS 32.

Table 3 lists the preferred types of instruments for applications commonly encountered in Water Corporation projects. The list is not exhaustive, and the Designer may encounter situations which call for novel solutions. Such situations shall be discussed with and approved by, the Principal SCADA Engineer.




Table 3: Preferred Instrument Types

Measured quantity Application Preferred instrument

types

Alternatives (subject to approval)

Notes

Level

Bore hole Hydrostatic

Reservoir Hydrostatic;

GP/DP transmitter on a static line;

Large dam

Float with shaft encoder located within a stilling basin;

Dry bubble unit measuring back pressure (high accuracy) for dams without a stilling basin;

Clearwater or treated effluent in open pump wells or tanks

GP/DP transmitter on a static line;

Ultrasonic;

Radar;

Pressure switch;

Float switch; (discrete applications only)

Selection to include considerations for compliance to Prevention of Falls.

Wastewater in channels, pump wells or tanks

Ultrasonic;

Radar;

Water or wastewater in closed vessels

Ultrasonic;

Radar;

DP transmitter;

Bar screen differential Ultrasonic:

Radar;

Sludge interface in sedimentation tanks and clarifiers

Optical;

Ultrasonic (heavy sludge’s only)

Has to comply to hazardous area requirement

Sludge in open digesters or storage tanks

Ultrasonic;

Radar;

Sludge in anaerobic digesters

Hydrostatic (water-purged or filled system);

Gas bubbler tube;

Dewatered sludge or other semi-dry materials in hoppers

Ultrasonic;

Load cells;

Chemical Tanks

GP/DP transmitter;

Ultrasonic;

Radar;

Magnetic Level Gauge;





types


Notes

Granules or dry powder

Guided radar; Load cells;

Ultrasonic;

Vibrating sensor (discrete applications only);

Flow

Water or wastewater in open channels (flume or weir)

Ultrasonic open-channel flowmeter Radar flowmeter

Water or wastewater in open channels with backpressure (no free fall)

Magnetic area velocity flowmeter;

Ultrasonic area velocity flowmeter;

Radar area velocity flowmeter;

Water, Wastewater or Sludge in closed pipes Magnetic Flowmeter

Ultrasonic;

DP Transmitter (in combination with DP device e.g. orifice plate, venturi or pitot tube);

Turbine;

Vortex;

Air in closed pipes, low pressure, high volume

Thermal mass flowmeter Orifice plate

Air in closed pipes, high pressure, low volume

Orifice plate Thermal mass flowmeter

Flammable gas Thermal mass flowmeter Ultrasonic transit-time

Must be certified for Class 1 Zone 0

Wet digester gas with free condensate

Should be avoided as measurement is difficult and expensive

Wet digester gas with no free condensate

Critical applications: Venturi flow meter with wet gas flow computer

Non Critical: Thermal mass flow meters (eg FCI ST80)

Ultrasonic transit-time





types


Notes

Dry digester gas Thermal mass flowmeter

DP Transmitter (in combination with DP device e.g. orifice plate, venturi or pitot tube);

Chemical solution lines Magnetic flowmeter

Coriolis (for high-accuracy applications)

Small seepage weirs Ultrasonic level measuring height over the vee-notch (derived flow)

Pressure

All normal applications

GP/DP transmitter

Pressure Switch (discrete applications only);

For applications requiring fast response times, specification of transmitter shall be considered.

Local indication only

Bourdon Tube Pressure Gauge (clean fluids only);

Diaphragm Pressure Gauge (contaminated fluids);

Contaminated fluids include aggressive, contaminated and viscous.

Temperature

Fluids (remote measurement) RTD in thermowell

Fluids (local indication only)

Dial thermometer in thermowell;

Electronic thermometer;

Ambient air RTD

Exhaust gases Thermocouple

Bearings RTD

Motor windings Thermistor;

RTD

Density Sludge density Microwave Nuclear

Nuclear meter installation to be certified by an authorised person

Vibration Rotating machinery Accelerometer

Preferably supplied as part of a complete condition monitoring system





types


Notes

Position

Linear

Magnetostrictive transducer;

Linear variable differential transformer (LVDT);

Linear potentiometer;

Angular Shaft encoder; Potentiometer;

Sensor Magnetic proximity;

Inductive proximity switch;

Mechanically-actuated limit switch; Photoelectric;

Analytical

Ammonia Analyser

Refer to OT Approved Equipment List

Chlorine Analyser

Chlorine gas detector

Conductivity analyser

Dissolved oxygen analyser

Flammable gas detector

Fluoride analyser

H2S gas detector

Monochloramine analyser

pH/ORP analyser

Turbidity and suspended solids

Table 4 lists the preferred types of control devices for Treatment Plant applications. With regard to valve controllers and actuators reference should also be made to design standard DS 40-07 and design standard DS 22. Again, the list is not exhaustive and unusual situations shall be discussed with the Principal SCADA Engineer.

Requirements for valves are covered in design standard DS 31-02.

Table 4: Preferred Control Devices

Device Application

Type

Notes Preferred


Valve actuators

Modulating duty Electric (infrequent operation); Pneumatic (frequent operation)

Control system design should seek to minimise hunting

On-off valves Electric Hydraulic

Pneumatic




Multi-turn (e.g. penstocks) Electric

3.2 Loop Drawing Examples Example loop drawings are below:

Installation Example Drawing

Analyser FQ09-059-001

Flow meter - Modbus Connection FQ09-059-002

Flow meter Hart Signal FQ09-059-003

Level – Water Conveyance Tank FQ09-059-004

Level – Bore FQ09-059-005

Level – Wastewater Pump Station FQ09-059-006

3.3 Level Instruments 3.3.1 General Requirements

Level instruments shall be selected and located so as to provide resistance to mechanical damage, fouling, blockage and chemical attack. Primary elements and transmitters shall be installed so as to facilitate maintenance, cleaning, removal and replacement with minimal disturbance to the process, e.g. mounted where accessible from the ground.

Instrument configuration shall be fully adjustable to suit the application. Transmitter output shall be linear, and transmitters shall incorporate local indication of level in engineering units.

Where continuous level measuring instruments are used for control of critical items such as wet wells, pumps and tanks, separate backup level instruments or switches shall also be provided and shall be arranged to initiate appropriate control actions and alarms.

3.3.2 Hydrostatic and Differential Pressure Instruments

Level instruments based on hydrostatic or differential pressure may be appropriate in many situations where the use of other instruments would be precluded due to access restrictions, explosion hazards, prevention of falls, or the like. Such situations include:

• Boreholes

• Bulk water storage tanks

• Anaerobic digesters

• Chemical storage tanks

• Closed vessels

• Elevated tanks




Hydrostatic pressure systems used for measurement of level shall consist of either a compact flange mounted gauge pressure transmitter or a remote gauge pressure sensor installed at a suitable point and connected to the transmitter. The remote sensor shall preferably be connected electrically to the transmitter.

Alternatively, a remote diaphragm seal, silicone oil filled and connected by armoured impulse tubing to a gauge pressure transmitter shall be used, and shall incorporate a means of compensating for any errors introduced by the hydrostatic pressure or thermal expansion of the filling fluid

Differential pressure systems used for measurement of liquid level in closed vessels (i.e. vessels not vented to atmosphere) shall consist of a flange-mounted differential pressure transmitter with a second flange mounted remote pressure sensor installed at a suitable point and connected electrically to the differential pressure transmitter, or two flange mounted remote pressure sensors installed at suitable points and connected electrically to a single differential pressure transmitter unit.

Alternatively two flange-mounted silicone oil filled remote diaphragm seals installed at suitable points and connected by armoured impulse tubing to a differential pressure transmitter shall be used and shall incorporate a means of compensating for any errors introduced by the hydrostatic pressure or thermal expansion of the filling fluid. The impulse tubing between the vessel and the differential pressure transmitter shall be run taped together in the same enclosure to minimise temperature differential effects.

In special cases where clean fluid is being measured, the use of impulse tubing connected to a gauge pressure or a differential pressure transmitter may be authorised by the Principal SCADA Engineer. The Designer shall in these cases consider the effects of air or contamination in the impulse lines, the position of the measuring cell in relation to the tapping points, and provision of the facility to isolate and purge the impulse tubing.

When used for measurement of sludge level in digesters, chemical storage tanks and other similar applications where fouling or blockage is likely, the diaphragm seal mounting arrangement shall incorporate a means of isolating and a means of flushing (e.g. continuous water purge), on-line cleaning or other means of eliminating, reducing or removing blockages.

For measurement of borehole levels, a self-contained submersible pressure transducer, vented to atmosphere by means of an integral vent tube, may be used.

The preferred installation for ground level tanks is shown in drawing: LP12-091-001(for general tanks) and LP12-091-003 (tanks subject to flooding) . For Elevated tanks the preferred installation is shown in drawing LP12-091-003. Installation using impulse tubing (non-preferred option) is shown in drawing LP12-091-005.

Pressure and differential pressure transmitters used for level measurement shall be in accordance with section 3.5 but with the local indicator scaled in appropriate units of level.

3.3.3 Ultrasonic Level Instruments

Level instruments based on ultrasonic sound wave time-of-flight may be appropriate in many applications. The technology is well proven, reliable, robust, cost effective and does not need to be in contact with the medium being measured.

Ultrasonic level instruments shall comprise of a transducer head with factory-fitted cable and a separate converter/transmitter. Alternatively, a single compact transducer with converter/transmitter can be used if appropriate for the installation.

The transducer head, including the cable seal, shall have a degree of ingress protection of IP66/68- versatile, and shall incorporate integral temperature compensation.




Digital outputs may additionally be provided if required for the application and shall preferably be voltage free contacts.

The instrument shall have an error specification of not more than ±0.25% of span. It shall incorporate filters that can be implemented or adapted to minimise the effect of surface turbulence, wave action, foam and fixed objects should they be encountered.

In liquid level applications subject to extreme turbulence it may be necessary to provide a stilling chamber, however stilling chambers have a tendency to block and should be avoided if at all possible.

The transducer shall be mounted so that its beam is perpendicular to the surface being measured. Under all normal conditions the minimum distance between the transducer head and the measured surface shall not be less than that recommended by the manufacturer, although occasional submersion of the head shall have no lasting effect on the performance of the system. Care shall be taken in the placement of the transducer and selection of the beam width to avoid false echoes from other objects.

3.3.4 Radar Level Instruments

Level instruments based on microwave time-of-flight may be appropriate in many applications. The technology is well proven, reliable, robust, and does not need to come into contact with the medium being measured. It has become more cost effective over recent years and can provide advantages over Ultrasonic measurements where there are effects on air characteristics such as temperature, pressure, dust, foam or turbulence.

Radar level instruments shall comprise of a transducer head with factory-fitted cable and a separate converter/transmitter. Alternatively, a single compact transducer with converter/transmitter can be used if appropriate for the installation.

The transducer head, including the cable seal, shall have a degree of ingress protection of IP66/68- versatile.

The instrument shall have an error specification of not more than ±0.25% of span. It shall incorporate filters that can be implemented or adapted to minimise the effect of surface turbulence, wave action, and fixed objects should they be encountered.

The transducer shall be mounted so that its beam is perpendicular to the surface being measured. Under all normal conditions the minimum distance between the transducer head and the measured surface shall not be less than that recommended by the manufacturer, although occasional submersion of the head shall have no lasting effect on the performance of the system. Care shall be taken in the placement of the transducer and selection of the beam width to avoid false echoes from other objects.

3.3.5 Guided Radar Level Instruments Guided radar level instruments may be appropriate in particularly difficult applications; the Designer would need to select this technology with knowledge that it will overcome the application difficulties and with approval from the Principal SCADA Engineer.

The technology is accurate, proven, reliable, and robust; it has become more cost effective over recent years and can provide an effective solution in selected applications. The concentrated microwave time-of-flight signal travels around a rod or rope type probe which is required to be in contact with the medium.

The Designer is required to carefully select and specify the probe type and length to ensure it correctly fits the application both from a dimensional and a material compatibility perspective.

Turbulent, viscous or solids containing processes may additionally require consideration for anchoring of the probe within the tank to avoid probe movement, damage and false measurements.




3.3.6 Float-Type Level Switches

Float-type level switches shall be used primarily as alarm or back-up level sensors. They shall consist of a mechanical tilt switch enclosed in a weighted float of inert plastic moulded to a flexible connecting cable. The complete assembly shall be capable of withstanding permanent immersion in water or raw sewage.

Where used with other fluids (e.g. chemicals, hydrocarbons) the level switches shall be specified to resist attack by the relevant fluid.

The float switch assembly shall not contain mercury or lead. The switch shall provide a normally-open and a normally-closed contact with a making and breaking capacity of not less than 5A at a voltage of 24V DC.

Where multiple float switches are to be installed the separation distance shall be a minimum of 300mm to avoid interference or cable entanglement. For turbulent processes increased separation distances or suitability of equipment may need to be considered.

3.3.7 Pressure-Type Level Switches

Pressure-type level switches shall be used primarily as alarm or back-up level sensors where Float-type level switches are unsuitable for use.

Pressure switches shall comply with section 2.15 of this Standard.

3.3.8 Setting of Level Datum

In bulk water applications the Principal SCADA Engineer will, where necessary, advise the reference height datum to be used for level measurements.

3.4 Flow Meters 3.4.1 General Requirements

Flow instruments shall be selected and located so as to provide resistance to mechanical damage, fouling, blockage and chemical attack. Primary elements and transmitters shall be installed so as to facilitate maintenance, cleaning, removal and replacement with minimal disturbance to the process.

Flow instruments shall comprise of a flowmeter head with a separate flow converter/transmitter and interconnecting cable. Alternatively, a single compact flowmeter with head/converter and panel mounted flow converters can be used if specified and appropriate for the installation.

Instrument configuration shall be fully adjustable to suit the application. Transmitter output shall be linear and shall incorporate local indication of flow rate and totalized flow readings in engineering units.

Flow instruments that are used for regulatory compliance or custody transfer must be able to verify their level of accuracy.

3.4.1.1 Positioning of Flowmeters in Pipes

The performance of flowmeters in pipes is critically dependent on the location of the meter within the pipe work system. Bends, tees, reducers and other fittings create flow disturbances and can significantly degrade meter accuracy if they are too close to the meter, either upstream or downstream.




Accurate flow measurement requires a minimum length of straight uninterrupted pipe both upstream and downstream of the flowmeter. To maintain accuracy, meters shall be installed with upstream and downstream straight pipe lengths in accordance with the manufacturer’s recommendations. If the flowmeter is intended to measure flow in both directions the upstream lengths shall apply on both sides of the flowmeter. In the absence of the manufacturer’s recommendations, or if the manufacturer has not been assigned, the minimum lengths are specified below in pipe diameters (D) for various types of meter:

• Magnetic flowmeter – full bore: at least 5D upstream and 3D downstream,

• Magnetic flowmeter – insertion type: as per ISO 7145 (normally at least 25D upstream and downstream),

• Single beam ultrasonic: at least 20D upstream and downstream, depending on the type of upstream and downstream fittings,

• Dual beam ultrasonic: at least 10D upstream and downstream, depending on the type of upstream and downstream fittings,

• Orifice plate: as per the relevant parts of AS 2360.1. (The orifice plate flowmeter is not a preferred type of instrument. Its use is subject to the Principal SCADA Engineer’s approval).

Where possible, flowmeter locations shall be determined early in the design. Locations shall be coordinated with other disciplines so that the recommended straight lengths can be incorporated in the pipe work design. In particular, flowmeters shall be located as far as possible downstream from the following:

• Two right-angle bends in different planes (introduces swirl, which leads to unpredictable errors),

• Valves, particularly valves that may be only partly open (introduces turbulence).

Positioning of flowmeters in close proximity downstream of chemical dosing points should be avoided, where possible the flowmeter shall be installed upstream of the dosing points, else the dosing methods, additional distance or mixing device shall be considered to ensure complete mixing of the process.

In some cases (existing sites, sites with restricted space and the like) it may not be possible to provide the recommended minimum lengths. In these cases, the flowmeter manufacturer should be consulted as to the best method of installation and the likely error.

3.4.1.2 Reducers

Reducers may be fitted upstream of flowmeters in order to increase the velocity through the meter provided that:

• The reduction angle does not exceed 8 degrees,

• Symmetrical reducers can be placed directly at the flow meter. Non=symmetrical reducers shall be treated as per valves etc.

• The velocity through cement-lined pipe work does not exceed 3 m/s, and

• Capitalised cost of head loss across reducers is taken into account when determining the amount of bore reduction.




3.4.1.3 Positioning of Flumes in Open Channels

The design, positioning and installation of flumes in open channels shall be in accordance with AS 3778.4.7 1991, “Measurement of water flow in open channels - Measurement using flow gauging structures - Rectangular, trapezoidal and U-shaped flumes”. (This standard is identical to ISO 4359:1983).

Performance of flume installations is strongly dependent on the location of the flume structure. To ensure that the approach velocity profile is substantially uniform the approach channel should be straight and uniform for a minimum of 5 channel widths upstream of the measuring point. Sharp bends in the approach channel should be avoided, but if this is not possible the length of straight channel downstream of the bend should be at least 10 channel widths.

Downstream of the flume the design of the installation must ensure that the flume cannot be submerged, i.e. that it always operates under free flow conditions. If this is done, the performance of the flume is substantially unaffected by downstream conditions.

Where possible, flume locations shall be determined early in the design. Locations shall be coordinated with other disciplines so that the recommended straight channel length can be incorporated in the hydraulic design.

Section 6 of AS 3778.4.7 provides guidelines for the selection, design and installation of flumes and these shall be followed.

3.4.2 Magnetic Flowmeters

3.4.2.1 Design and Selection

The flowmeter head shall consist of a circular tube with an insulating liner, two measuring electrodes and connecting flanges at each end.

Flowmeter heads for measuring potable wastewater and water shall be fitted at each end with flanges, of the specified class, in accordance with AS 4087 "Metallic Flanges for Waterworks Purposes" or to EN1092 – Flanges and their joints. Flanges to ANSI, DIN or other standards are not acceptable.

Flowmeters for chemical dosing applications (generally less than 50mm diameter) may be sandwich type, suitable for clamping between suitable pipe flanges.

The pressure rating of the flowmeter tube shall be not less than that of the flanges. Flange rating shall match the adjoining pipework.

Electrodes shall be flush with the lining of the flowmeter head.

Where the standard model is not suitable for direct burial installation, a suitable model shall be available as a purchasing option.

Where meters are to be direct buried, the cables shall be pre-fitted and rated as IP68.

Meters shall be sized so that under normal conditions the flow velocity through the meter tube is not less than 0.6 m/s. and not more than 10 m/s (if possible, not more than 5 m/s). Meter error in the above velocity range and with recommended installation conditions shall not exceed ±0.5% of flow rate, but may increase to ±5% at 0.06 m/s.




For applications involving a wide range of flows (e.g. gravity flow) the Designer shall submit details of the proposed design and supporting calculations to the Principal SCADA Engineer for approval. The design shall consider:

• the use of an unlined 316 stainless-steel reducer so as to utilise the full available flow range of the flowmeter, and;

• the practical significance of the increased error at low flow rates.

Flowmeters for use in clear water lines shall be specified with PTFE (Teflon) or hard rubber (ebonite) linings and 316 stainless steel or Hastelloy C electrodes. For flow meters DN600 or greater, hard ebonite shall be used.

Flowmeters for use in wastewater lines shall be specified with hard rubber (ebonite) linings and 316 stainless steel or Hastelloy C electrodes.

Flow detecting heads weighing more than 100 kg shall be supplied fitted with lifting rings or eye bolts, rated in accordance with AS 3776 “Lifting components for Grade T chain slings" or AS 2317 "Collared Eyebolts".

Flowmeter testing and verification to the manufacture’s specification shall be possible infield and the procedure fully documented. For flow meters DN600 or greater a fully internally lined flowmeter shall be subject to a certified hydrostatic test in the factory to a pressure rating as specified in the datasheet, or higher.


Flowmeters shall be installed in accordance with the Corporation’s standard flowmeter installation drawings and the manufacturer’s recommendations. All such recommendations shall be included in the relevant installation contract documents. Flow meters installed in conveyance pipelines shall adhere to DS 60 – Water Supply Distribution and DS 38-1 – Installation – Mechanical. Drawings referenced in these standards that are applicable to flow meter installations include:

• EG20-004-002 (DS 60) Magnetic Flow Meter Installation – Example Drawing

• EG20-004-004 (DS 60) Magnetic Flow Meter Aluminium Sunshade

• JZ39-091-010 (DS38-02) Flange Isolation Joints

Installation design shall consider the following:

• The flowmeter head shall be located so that it is always full. In the case of partially filled pipes the head shall be installed in a U-section of pipe.

• The flowmeter shall be installed with the measuring electrode axis horizontal.

• Earthing rings shall be fitted on both sides of all flowmeters, not having integral earthing electrodes and to all flowmeters installed in long steel pipelines regardless of whether they have integral earthing electrodes. Earthing electrodes shall be 316 stainless steel, resistant to deforming and machined with a gramophone finish.




• Where the pipe is cathodically protected, isolation shall be provided in accordance with Design Standard DS 21.

• Buried meters shall not be installed under roads or other heavy traffic areas

The designer shall assess the electromagnetic interference at the particular site and adopt one of the two following approaches to determine the allowed route length of cable between the flow transmitter and the flow meter head:

• If the site is assessed as being exposed to electromagnetic interference or electromagnetic interference level is unknown, then:

o Either the flow transmitter shall be located adjacent to the flowmeter head in a dedicated flowmeter cubicle as detailed in FQ09-059-002

o Or the allowed route length of vendor supplied cable between the transmitter and the flowmeter head shall be no more than 50 m with appropriate magnetic screening. The most appropriate method of magnetic screening shall be advised as a note on the loop diagram by the Designer. If a longer distance is required, approval shall be sort from the Principal SCADA Engineer.

• If the site is assessed as having minimal or no electromagnetic interference then the allowed route length of vendor supplied cable between the transmitter and the flowmeter head shall be no more than 30 m and there is no need for magnetic screening in this case. The flow transmitter shall be located in a dedicated cubicle as detailed in FQ09-059-002

A Pitot tube insertion point shall be provided for testing purposes within 20D of water meters in the following cases:

• Critical Meter Sites;

• All water distribution and zone meters;

• Direct buried meters;

• Revenue meters;

• Meters that cannot conveniently be removed for workshop calibration.

The arrangement of the Pitot tube insertion point for buried meters shall be as shown on drawing EG20-9-1.

3.4.3 Ultrasonic Flowmeters

Ultrasonic flowmeters are not preferred but can be effectively used as an alternative flow measurement where process conditions are suited, and the accuracy of the measurement is acceptable. However, they shall not be used on MSCL pipes.

They measure homogeneous fluids independently of pressure, temperature, conductivity, and viscosity.

Flowmeters can vary in installation methods from a pre-constructed flow tube, insertion sensors for pipelines, or externally mounted non-intrusive clamp on types. Accuracy of the measurement generally follows the installation method.




The non-intrusive type although least accurate offer the benefits of being able to be retrofitted to existing pipes, be used for a wide range of pipe sizes, require no process interruptions, have a portable format that can be moved from site to site, be used for flow comparisons.

Externally mounted sensors shall be secured using the manufacturers approved mounting system and method for installation.

Insertion sensor mounting sockets shall be installed in accordance with the Corporation’s piping standards and the manufacturer’s recommendations.

Externally mounted or insertion sensors shall be installed at distances as calculated from the manufacturer data and based upon accurate information required for the installation such as fluid type, pipe material and pipe dimensions.

Ultrasonic flowmeters shall not be used if the process has low flow velocity (<0.2m/s), variable gas or solids content, or if the accuracy requirement is better than ±0.5% of the operating range for constructed installations or better than ±2% of the operating range for clamp on types.

Flowmeters that are part of a constructed fixed installation shall meet the general Flow Instrument requirements.

Flowmeters that are a temporary or portable installation need not meet all of the general Flow Instrument requirements if agreed with the Principal SCADA Engineer, but shall still conform to General Design Principles of the corporation for instruments as specified in section 2. The installation shall be deemed temporary and not be used as a substitute for a permanent installation.

3.4.4 Head Loss Flowmeters

Flowmeters such as orifice plates and venturi tubes which operate on the head loss principle are not preferred. The performance of head loss meters is relatively poor, and the capitalised cost of the head loss energy often exceeds the additional cost of one of the preferred types of flowmeter.

Nevertheless, such instruments may provide the most cost effective solution in some applications such as compressed air and high-pressure gas lines where the range of flows is relatively small (typically less than 3:1) and the head loss is not significant. In such situations head loss flowmeters may be used subject to the approval of the Principal SCADA Engineer.

The two most common types of head loss meter are described below.

3.4.4.1 Orifice Plate Flowmeter

The cheapest and most robust head loss flowmeter consists of an orifice plate and a differential pressure transmitter. Orifice plates shall be used only in clear water or clean gas applications where the following conditions are fulfilled:

• there are at least 25D of straight pipe upstream and 10D downstream of the orifice plate (assuming a diameter ratio of not more than 0.6);

• the capitalised cost of the head loss does not justify the use of a preferred flowmeter type;

• the maximum-to-minimum flow range to be measured is not more than 3:1;

• and an accuracy of typically ±3% of upper range value can be tolerated.




3.4.4.2 Venturi Flowmeter

The venturi flowmeter results in less head loss and can tolerate a higher level of turbulence but produces a smaller pressure differential and is more expensive than an orifice plate. It also tends to be significantly longer. Otherwise its performance is similar to the orifice plate flowmeter and similar restrictions on its use apply.

Venturi flowmeters shall not be used unless approved by the Principal SCADA Engineer for the particular application.

3.4.5 Open Channel Flowmeters

3.4.5.1 Flume

Flumes used for open-channel flow measurement shall preferably be rectangular-throated due to their simpler construction. Trapezoidal or U-shaped flumes are not preferred but may be used subject to the approval of the Principal SCADA Engineer if the Designer considers that they will provide better performance in a particular situation.

Flumes shall be lined with a 316 stainless steel or GRP liner manufactured to the tolerances required by AS 3778.4.7. During transport and installation, the liner shall be adequately braced to maintain dimensional stability. Following installation, the dimensions shall be carefully checked and recorded to enable the flowmeter to be accurately calibrated.

3.4.5.2 Flow Meter

The flow meter shall comprise an ultrasonic transducer head with factory-fitted cable and a separate converter/transmitter. It shall continuously measure the head upstream of the flume and convert the head measurement to a flow signal using a pre-programmed algorithm which can be selected and configured to suit the actual characteristics and dimensions of the flume.

The transducer and cable seal shall have a degree of protection of IP68. The head measurement shall be automatically compensated for variations in air temperature in the vicinity of the transducer.

The head measuring point shall be selected in accordance with the recommendations of AS 3778.4.7 (e.g. for a rectangular-throated flume, a distance upstream of the flume entry section of typically 3 to 4 times the maximum head). The head shall be measured over the channel itself; unless there are compelling reasons (e.g. extreme turbulence or wave action), the use of stilling chambers shall be avoided due to their tendency to block. The converter/transmitter shall incorporate adjustable damping to average out variations due to turbulence and wave action.

The transducer shall be rigidly mounted so that its beam is perpendicular to the water surface. The minimum distance between the transducer head and the measured surface shall not be less than that recommended by the manufacturer. Care shall be taken in the placement of the transducer and selection of the beam width to avoid false echoes from other objects.

Where required the converter/transmitter shall also incorporate data logging facilities capable of storing time-stamped flow measurements at intervals adjustable from 1 minute to 1 hour. The data logger shall have sufficient memory to store at least 6 months of readings at 15 minute intervals. An inbuilt battery shall ensure the retention of configuration and log data during loss of power.

The complete installation (flume, transducer and converter/transmitter) shall have a measurement error of not more than ±5% of flow. It shall incorporate damping to minimise the effect of surface turbulence or foam.




3.4.6 Thermal Mass Flowmeters

Thermal mass flowmeters consist of a heating probe and a temperature probe mounted adjacent to each other in a common assembly. The instrument measures either the temperature change in the gas stream resulting from a constant power input to the heater or the power required to maintain the heater at a constant temperature. The instrument uses this information together with the properties of the fluid to compute mass flow.

Typical accuracy of a thermal mass flow meter under ideal conditions is ±1%.

Thermal mass flowmeters have very low head loss and are therefore the preferred method for measuring high volume, low to medium pressure air flows, where the cost of head loss may be significant. Typical applications include aeration air supply pipe work and odour extraction ductwork.

Thermal mass flowmeters may also be used for measuring digester gas flow providing the gas is reasonably clean, free from entrained droplets and reasonably constant in composition.

Probes shall be constructed of 316 stainless steel (for clean air) or Hastelloy C (for other gases). Insertion type probes are preferred, since they can be easily withdrawn for cleaning and maintenance. However, note that insertion probes require a minimum of 20D of straight pipe upstream and 10D downstream for best accuracy.

Where it is not possible to provide the optimum lengths of upstream and downstream straight pipe, flow straightening vanes may be installed upstream of the probe or an in-line instrument incorporating a flow conditioner may be used. However, both of these options increase the cost of installation and the difficulty of maintenance and may not provide the same degree of accuracy.

Instruments used for measuring digester gas flow shall be of the insertion type to facilitate inspection and cleaning. Note that variations in the composition and moisture content of the gas will affect instrument accuracy and entrained droplets may cause erratic readings. Therefore, careful attention needs to be paid to the location of the meter (e.g. preferably downstream of scrubbers or dryers).

Correct insertion depth of the probe assembly is important; when used in large-diameter lines, the use of two or more probe assemblies with an averaging converter may be necessary.

3.4.7 Flow Switches

Accurate flow measurement requires a minimum length of straight uninterrupted pipe both upstream and downstream of the flowswitch. The recommended minimum lengths are specified below in pipe diameters (D) for flowswitches:

• Paddle Type Flowswitches: at least 10D upstream and 5D downstream depending on the type of upstream and downstream fittings;

• Thermal Type Flow Switches: at least 10D upstream and 5D downstream depending on the type of upstream and downstream fittings;

3.4.7.1 Paddle Type and Trailing Wire Flowswitches Paddle type flow switches are an electromechanical device with no intelligence, paddle selection is a high consideration to suit the installed application. For example, in environments where abrasive material is present (ie grit systems) a trailing wire should be selected. They should be used for switching at flow rates within 20% to 80% of flow range where low repeatability and hysteresis values are not required.




Process connections on switches shall be direct mount with a minimum 1" NPT (male) thread, connection. Sensing element shall be of 316 stainless steel except where stainless steel is incompatible with the process fluid. The switch housing, paddle and wetted parts shall be of non-corrodible materials selected to suit the application.

Paddle type flow switches shall be installed in a horizontal pipe in an upright position.

The length of the connection adapter to the wall of the pipe with flow being measured shall be a maximum of 25mm.

Pressure rating shall generally be in accordance with the piping specification but in any case, not less than Class 14 on piping and Class 21 on vessels.

Process connection position shall be selected to minimise risks of either turbulence or accumulation of gas or solids which could impair the measurement.

Paddle type flow switches shall have adjustable sensitivity; adjustments shall be internal and shall not be accessible with the cover in place. A set of changeover contacts rated not less than 5A, 24 V DC shall be provided for each output.

Switches shall be capable of continuously withstanding maximum line flow without losing calibration.

The maximum error of flow switches shall be 20% of actual flow with 10% repeatability.

3.4.7.2 Thermal Type Flowswitches Thermal type flow switches are an electronic device with some intelligence, as a result they are more suited to switching at low flow rates or where a higher accuracy is required than a mechanical flow switch can provide.

Process connections on switches shall be direct mount with a minimum 1/2" NPT (male) thread, connection. Sensing element shall be of 316 stainless steel except where stainless steel is incompatible with the process fluid. The switch housing and wetted parts shall be of non-corrodible materials selected to suit the application.

Thermal type flow switches shall be installed in a horizontal pipe in a horizontal position to the side of the pipe.

The length of the connection adapter to the wall of the pipe with flow being measured shall be a maximum of 25mm. The length of the sensing element will provide full immersion into the flow stream with clearance from the pipe wall.

Pressure rating shall generally be in accordance with the piping specification but in any case, not less than Class 14 on piping and Class 21 on vessels.

Process connection position shall be selected to minimise risks of either turbulence or accumulation of gas or solids which could impair the measurement.

Thermal Flow switches shall have an adjustable switch point and provide a set of changeover contacts rated not less than 2A, 24 V DC for each output. Alternatively, a switched 24V DC output with current rating >200mA may be provided to signal interface relay or Controller input.

Switches shall be capable of continuously withstanding maximum line flow without losing calibration.

The maximum error of flow switches shall be 10% of actual flow with 5% repeatability.




3.5 Pressure Instruments 3.5.1 General Requirements

Pulsation dampers shall be fitted to instruments subject to unwanted pressure pulsations, such as the delivery lines of pumps or compressors. Partially closed isolation valves are not acceptable as a means of damping.

To ensure fast response and reduce problems due to vibration of impulse lines, pressure instruments shall be located as close to the process connection as possible. Impulse lines shall be kept as short as possible without high or low points to reduce the possibility of gas or liquid becoming trapped in the line. For liquids, the lines shall slope downwards from the process connection to the instrument; for gases, the lines shall slope upwards from the process connection to the instrument.

Impulse lines shall be adequately sized to minimise the effects of friction error and the likelihood of blockage.

When dual impulse lines are used, the two lines shall be enclosed or taped together to minimise temperature differences.

3.5.2 Pressure Transmitters

3.5.2.1 General Requirements

Pressure instruments shall be selected and located so as to provide resistance to mechanical damage, fouling, blockage and chemical attack. Primary elements and transmitters shall be installed so as to facilitate maintenance, cleaning, removal and replacement with minimal disturbance to the process.

Instrument configuration shall be fully adjustable to suit the application. Transmitter output shall be linear, and transmitters shall incorporate local indication of pressure in engineering units.

Each pressure transmitter shall be provided with a 316 stainless steel block and bleed valve manifold to enable venting of entrapped air or liquid and to facilitate removal of the transmitter. Manifolds shall be two-valve for gauge pressure transmitters and three-valve for differential pressure transmitters and shall incorporate a calibration connection.

The Designer shall specify the required configuration (span, zero, damping etc.) for each transmitter. Transmitters shall be supplied pre-configured, avoiding the need for configuration at site.

3.5.2.2 Pressure Ratings

Gauge pressure transmitters shall be capable of withstanding at least 150% of maximum operating pressure without damage.

The maximum static line pressure of differential pressure transmitters shall be specified. Transmitters shall be capable of withstanding maximum line pressure on either side with the other side vented to atmosphere, without damage and without affecting calibration.

Transmitters shall be specified to withstand without damage any vacuum that may be applied under normal or abnormal process conditions.




3.5.2.3 Accuracy

Pressure transmitters shall be specified with accuracy appropriate to the application, but in any case, the measurement error shall be no more than ±0.25% of span. Since error increases with turn-down ratio, this will generally require the designer to select an instrument upper range limit (URL) such that the turn-down ratio does not exceed 10:1.

3.5.2.4 Stability

Long-term drift of pressure transmitter output shall not be more than ±0.125% of URL per year under the actual operating conditions at site.

3.5.2.5 Response Time

Transmitters for general applications shall have a response time to a step pressure change (time to reach 63% of final value) of not more than 200ms.

Where the output of the pressure transmitter is to be used for detection of fast impulses or transients (for example in pipe burst or leak detection schemes) a faster response time shall be specified to suit the application.

3.5.2.6 Construction Materials

Pressure transmitters for use in clear water or wastewater lines shall be specified to be made of the following materials:

(a) body: aluminium or 316 stainless steel

(b) isolating diaphragms: 316 stainless steel

(c) flanges, adapters, plugs and drain/vent valves: 316 stainless steel

(d) sealing gaskets and O-rings: PTFE

Wetted parts of pressure transmitters to be installed near chlorine injection points shall be specified to be made of the following materials:

(a) isolating diaphragms, flanges, adaptors, plugs and drain/vent valves: Hastelloy C

(b) sealing gaskets and O-rings: PTFE

Pressure transmitter materials for use with fluids other than clear water and wastewater shall be in accordance with the manufacturer’s recommendations. The Designer shall ensure that the full process fluid description is included in the transmitter specification or data sheet.

3.5.2.7 Process Connection

Each pressure transmitter shall be provided with a two-valve (block and bleed) valve manifold to enable venting of entrapped air or liquid and to facilitate removal of the transmitter.

Valve manifolds shall also be two-valve for gauge pressure transmitters and pressure switches.




Valve manifold shall be three-valve (block, bleed and equalise) for differential pressure transmitters and also incorporate venting/calibration connections.

The material of construction of the valve manifold shall be compatible with the process fluid – refer to above section 3.5.2.6.

3.5.3 Pressure Switches

Pressure switches shall be continuously adjustable over their full range with adjustable dead band. Adjustments shall be internal and shall not be accessible with the cover in place. A set of changeover contacts rated not less than 5A, 24 V DC shall be provided for each separate set point.

Electronic type pressure switches may alternatively provide a switched 24V DC output with current rating >200mA to signal interface relay or Controller input.

Proof pressure shall be a minimum of 150% of maximum line pressure. Switches shall be capable of continuously withstanding maximum line pressure without losing calibration.

The maximum error of pressure switches shall be 2% of actual pressure with a 1% repeatability.

The process connection and sensing element shall be of 316 stainless steel except where stainless steel is incompatible with the process fluid. The switch housing, diaphragm and wetted parts shall be of non-corrodible materials selected suit the application. Pressure switches mounted on surge vessels shall incorporate a liquid filled remote diaphragm system.

3.5.4 Pressure Gauges

Local pressure gauges shall be of the Bourdon tube type. Instruments shall comply with the requirements of AS 1349 "Bourdon Tube Pressure and Vacuum Gauges".

Maximum error shall be ±2% of actual pressure with ±1% repeatability.

Pressure gauges shall have a minimum 100 mm diameter dial with black numerals on a white background and markings to minimise parallax error. Scales shall be calibrated in engineering units. Ranges shall be chosen such that normal operating pressures are within the middle third of the gauge range. Scale range shall be large enough to handle surge pressure.

Process connections on gauges, other than gauges required to have diaphragm seals shall be direct mount with a ½" NPT (male) connection, with 316 stainless steel case and bezels, and toughened glass window.

Pressure rating shall generally be in accordance with the piping specification but in any case, not less than Class 14 on piping and Class 21 on vessels. All direct process connections shall be provided with isolating valves.

The process connection and all wetted parts shall be of non-corrodible materials selected to be compatible with the process fluid, all movement parts shall be non-ferrous.

Process connection position shall be selected to minimise risks of either accumulation of gas or solids which could impair the measurement signal.

For applications with high dynamic pressure loads or vibrations a glycerin liquid filled case shall be used.

For applications that have material compatibility constraints, aggressive, contaminated or viscous media a diaphragm pressure gauge shall be used.




3.6 Temperature Instruments

3.6.1 Temperature Transmitters

3.6.1.1 Sensing Element

Temperature transmitters shall utilise three-wire Pt100 resistance temperature detector (RTD) elements conforming to IEC 60751, “Industrial Platinum Resistance Thermometer Sensors”. RTD elements shall be Class B accuracy unless the application calls for higher accuracy.

Except for surface temperature measurement, RTD elements shall be installed in thermowells as specified in this section.

3.6.1.2 Transmitter

Transmitters shall incorporate a "burn-out" feature which shall initiate an alarm (or shall drive the output to the alarm or trip condition) in the event that the RTD element fails.

In normal applications temperature transmitters shall have bodies of aluminium or 316 stainless steel. Where transmitters are to be installed in particularly aggressive environments, materials shall be as recommended by the manufacturer for the specific environment.

3.6.1.3 Accuracy

Overall accuracy of the transmitter and RTD element shall be appropriate to the application, but in any case, the absolute measurement error shall be no more than ±1oC from 0- 100oC and ±2oC from 100o-200oC.

3.6.1.4 Stability

Long-term output drift of the transmitter and RTD element combined shall not exceed ±0.2oC per year under the actual operating conditions at site.

3.6.1.5 Thermowells

Thermowells shall be manufactured from solid bar stock. The material of construction shall be 316 stainless steel unless process conditions require otherwise. Galvanic effects shall be considered where the thermowell is of different material from the pipe.

In designing, selecting and installing thermowells it is important to ensure that the heat-sensitive part of the RTD element is located in the middle third of the fluid stream. Where fluid filling is required, thermowells shall be installed above the horizontal.

In high-velocity or turbulent fluid streams the possibility of thermowell damage due to vibration induced by vortex shedding shall be considered.

3.6.2 Temperature Switches

Temperature switches shall be calibrated in degrees Celsius and shall be continuously adjustable over their full range with adjustable dead band. Adjustments shall be internal and shall not be accessible with the cover in place. A set of changeover contacts rated not less than 5A, 24 V DC shall be provided for each separate set point.




Electronic type temperature switches may alternatively provide a switched 24 V DC output with current rating >200mA to signal interface relay or Controller input.

The maximum setting error of temperature switches shall be ±2.5oC of dial setting with a ±1oC repeatability.

The process connection shall be either direct or bulb and capillary, depending on the application. Stems, bulbs and capillaries shall be of 316 stainless steel unless process conditions require otherwise. The switch housing shall be of non-corrodible materials selected suit the application.

3.6.3 Temperature Gauges

Temperature gauges used for local temperature indication shall be rigid stem dial-type thermometers in accordance with BS 1041-2.2, “Code for temperature measurement. Expansion thermometers. Guide to selection and use of dial-type expansion thermometers”. Bimetallic thermometers are preferred.

Maximum error shall be ±2oC with ±1oC repeatability.

The process connection shall be either direct or bulb and capillary, depending on the application. Stems, bulbs and capillaries shall be of 316 stainless steel unless process conditions require otherwise.

3.6.3.1 Dial-Type Thermometers

Dial-Type Temperature gauges used for local temperature indication shall be rigid stem dial-type thermometers in accordance with BS 1041-2.2, “Code for temperature measurement. Expansion thermometers. Guide to selection and use of dial-type expansion thermometers”. Bimetallic thermometers are preferred.

Temperature gauges shall have a minimum 100 mm diameter dial with black numerals on a white background and markings to minimise parallax error. Scales shall be calibrated in degrees Celsius. Ranges shall be chosen such that normal operating temperatures are within the middle third of the gauge range.

Maximum error shall be ±2oC with ±1oC repeatability.

The process connection shall be either direct or bulb and capillary, depending on the application. Stems, bulbs and capillaries shall be of 316 stainless steel unless process conditions require otherwise.

3.7 Density Gauges 3.7.1 General

The main application of density gauges within the corporation is for continuous measurement of sludge density in wastewater treatment. Density measurements are typically used for:

• - control of sludge withdrawal from sedimentation tanks;

• - estimating the amount of solids transferred (e.g. for mass balances or digester control purposes).

Most density instruments work by measuring the absorption or reflection of some form of radiation (sound, microwave, optical or nuclear). This measurement is then used to calculate density.




Instruments that measure the absolute density of the fluid stream (e.g. nuclear) are generally less affected by the nature or composition of the sludge. However, estimation of solids content requires accurate calibration, as the specific gravity of most wastewater sludge’s is close to that of water.

On the other hand, the accuracy of instruments that measure absorption or reflection by suspended particles (e.g. ultrasonic, optical) tends to be dependent on the nature and size of the particles, so that changes in sludge composition may lead to significant measurement errors.

True mass flow instruments such as Coriolis mass flow meters can also be used to calculate density but are limited in pipeline size capabilities and tend to be much more expensive for pipelines >DN50.

Experience has shown that nuclear density gauges produce the most reliable results with wastewater sludge’s, and they are preferred for such applications. However due to the requirements for managing Radioactive Sources at installations there is always a quest for viable alternative measurements, one that has been used with some success is based upon Microwave measurement.

This Microwave measurement is based upon the phase shift of microwaves that are passed through the process media, the magnitude of the phase shift is related to the density of the media, and it overcomes many of the difficulties that reflection type measurements encounter.

3.7.2 Nuclear Density Gauges

3.7.2.1 Technical requirements

Gauges shall consist of a low-activity radioisotope source (generally caesium-137), a scintillation detector and a converter unit.

The source shall be shielded, fully enclosed and provided with a lockable shutter in accordance with the requirements of the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). The degree of protection of the source, detector and converter unit shall be IP66 as a minimum.

The detector and converter unit shall incorporate temperature compensation, gain stabilisation, dead time correction and compensation for decay in source activity. The source-decay clock shall continue to operate with converter power off.

The gauge shall have a repeatability of better than ±0.0005 units of specific gravity and shall not require recalibration more often than once a year.


Gauges shall be of the “clamp-on” type, suitable for external mounting on either new or existing pipes. Since the radiation path includes two wall thicknesses, pipes should preferably be of lower density material such as FRP or thin-walled steel rather than MSCL, to reduce attenuation of the beam.

Gauges require a minimum fluid path length for accurate results. Therefore, when used with small-diameter pipes it may be necessary to mount the instrument on a “Z-bend” in the pipe with the beam path axial rather than radial.

Bubbles or entrained air in the fluid will produce significant measurement errors. Therefore, the gauge should, where possible, be mounted in a vertical pipe section. If it is necessary to mount the gauge on a horizontal pipe section, the beam path should be horizontal rather than vertical to minimise errors due to solids deposition or gas pockets. The pipe should be protected from heat or direct sunlight to minimise gas generation due to septicity.




Due to the shielding requirements, nuclear density gauges tend to be large and heavy. This needs to be taken into account when considering access and lifting arrangements.

3.7.3 Microwave Density Gauges

3.7.3.1 Technical requirements Gauges shall consist of a microwave emitter/receiver unit either in the form of a flow through tube or an insertion sensor.

Flow through tubes shall be fitted at each end with flanges, of the specified class, in accordance with AS 4087 "Metallic Flanges for Waterworks Purposes".

Flanges to DIN or ANSI, are acceptable if there is no availability of AS standard gauges.

The pressure rating of the flow tube shall be not less than that of the flanges.

The gauge shall have a repeatability of better than ±0.05 units of total solids and shall not require recalibration more often than once a year.

3.7.3.2 Installation The gauge shall be located in a position so that it is always full, vertical rising pipes are preferred, horizontal pipes are acceptable if they remain full. In the case of partially filled pipes the tube shall be installed in a U-section of pipe.

The flow tube shall be installed with the measuring electrode axis horizontal.

Install the gauge in a pipeline without bubbles or entrapped air, avoid places where sediment collects at the bottom of the pipe, well mixed laminar flow will provide best results.

A process sample tap shall be installed a close to the gauge as possible to enable calibration samples to be collected and the gauge to be verified against laboratory results.

Provision shall be allowed for clean potable water to be connected upstream of the gauge in order to flush and fill the flow tube or measuring area with clean water. This will allow the zero point of the gauge to be set and or checked on a periodic basis as necessary.

3.8 Condition Monitoring Instrumentation 3.8.1 General Requirements

Condition monitoring refers to the use of instrumentation to monitor the condition of mechanical equipment. Its main purposes are to provide early warning and diagnosis of abnormal operation, to assist in maintenance planning and to assist in predicting failure. The technologies available for condition monitoring include vibration and displacement measurement, temperature measurement, motor current analysis and oil analysis.

This section deals with vibration and displacement instrumentation. Temperature instrumentation is covered in section 3.6. Motor current analysis and oil analysis are outside the scope of this Design Standard.

The most suitable type of instrumentation in a particular situation will depend on a number of factors, such as:

• The type and importance of the equipment to be monitored;

• The type of bearings (sleeve or rolling element);




• Whether the instrumentation is to be used for condition analysis or is simply required to provide alarm and trip functions.

This section describes typical requirements; the requirements in particular situations shall be specified in consultation with the Mechanical Designer.

In general vibration monitoring systems shall conform to AS 2625.1 "Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts - General guidelines".

3.8.2 Application

For each item of equipment, the need for condition monitoring shall be assessed based on the importance of the item and the consequences of failure. The table below lists the type of condition monitoring that shall typically be provided for particular classes of equipment:

Table 5: Condition Monitoring

Equipment Class Rating Parameters to be monitored Pumps and motors Rated ≥ 180 kW Bearing temperature

Rated ≥ 500 kW Bearing temperature and vibration Low speed fans and blowers

Rated ≥ 100 kW Bearing temperature and vibration

High speed fans, blowers and centrifugal compressors

Rated ≥ 50 kW Bearing temperature and vibration Rated ≥ 400 kW Bearing temperature and vibration;

Lube oil pressure; Shaft displacement

Reciprocating compressors Rated ≥ 22 kW Lube oil temperature Gearboxes Rated ≥ 100 kW Bearing temperature and vibration;

Lube oil pressure Rated > 400 kW

Bearing temperature and vibration; Lube oil pressure; Shaft displacement

3.8.3 Sensors

3.8.3.1 Permanently Installed Vibration Sensors

Vibration sensors are primarily used to measure vibration of bearings, gearboxes and the like. Either piezoelectric accelerometers or “Smart Vib” sensors shall be used.

The vibration sensors shall be electrically isolated. The housing shall be constructed from type 316 stainless steel and shall be hermetically sealed.

Accelerometers shall typically be installed in the following locations:

• For normal rolling element or journal bearings, at each bearing position, radially with respect to the shaft axis and in the horizontal plane;

• For large rolling element bearings, through the bearing housing to directly monitor the bearing outer ring;

• Additionally, for thrust bearings, in the axial plane with respect to the shaft axis;




For gearboxes, in an axis parallel to the pressure angle of the gearing.

Where the monitoring system is to be used for vibration analysis, a rotational speed sensor is normally required as well, to supply a reference signal.

Specifications shall require the condition monitoring equipment supplier to supervise and certify the installation of all vibration sensors and associated signal converters.

3.8.3.2 Provision for Portable Vibration Sensors

Where required, rigidly fixed vibration studs shall be provided for use with portable vibration measuring equipment. The studs shall be located in readily and safely accessible positions directly in contact with bearing housings.

3.8.3.3 Position Sensors

In general eddy current probes shall be used for position sensing. Eddy current probes are non-contact devices which provide an output proportional to position. They are commonly mounted in bearing assemblies to detect excessive axial or radial movement.

Eddy current probes shall be electrically isolated and shall consist of an enclosed sensor fitted with connecting cable and connector. The probe housing shall be constructed from type 316 stainless steel and shall be hermetically sealed.

The surface to be observed by the probe shall not be metallised or plated and shall be free from surface irregularities, oil holes, keyways and the like. It shall be demagnetised or otherwise treated so the combined total mechanical and electrical runout does not exceed 25 per cent of the maximum allowed peak-to-peak vibration amplitude or 6 micrometres, whichever is greater.

The probe gap shall be set at the centre of the sensor's linear range and the mounting arrangement shall ensure that the probe is not affected by any metal other than the intended target.

3.8.3.4 Bearing Temperature Sensors

Bearing temperature sensors shall consist of Pt100 resistance temperature detector (RTD) elements as described in Section 3.6.

3.8.3.5 Sensor installation

All machinery-mounted sensor and instrument cabling shall be run in earthed 316 stainless steel conduit or copper tubing terminating in purpose-designed conduit entries. Cables subject to flexing or vibration shall be enclosed in flexible stainless steel conduit. Conduit and conduit connections shall be oil tight.

3.8.4 Monitoring equipment

All monitoring equipment (vibration, displacement, temperature and the like) for a given machinery item shall be housed in a common monitoring rack together with the associated displays, alarms, shutdown functions and power supplies. The monitoring rack shall provide for data communications with the plant control system via an approved data bus system. It shall be possible to set warning, alarm and trip points for each sensor independently and to individually access each sensor signal via the data bus




3.9 Position Instruments 3.9.1 Position Sensors

3.9.1.1 General

As far as possible, sensors shall be arranged to detect the position of the final device directly rather than the position of the actuating mechanism. Sensors shall be mounted to fixed (stationary) equipment.

3.9.1.2 Binary Sensors

Position sensors used for detecting specific positions of moving machinery such as valves, penstocks, doors, gates and the like shall be of the non-contact proximity type. The use of mechanical limit switches or other contact sensors shall be avoided due to their susceptibility to damage and their tendency to fall out of adjustment.

When a limit switch is an integral part of a mechanism such as an actuator, and is a well proven reliable design, then mechanical limit switches would be acceptable.

For normal applications, sealed inductive or magnetic proximity sensors are preferred. Capacitive, photoelectric or other sensors may be used if considered more suitable in particular situations and subject to the approval of the Principal SCADA Engineer. Sensing range shall be selected to provide adequate separation between moving and stationary parts whilst ensuring that only the intended target is detected.

Binary sensors shall be suitable for 24V DC two-wire operation.

3.9.1.3 Analog Sensors

Position sensors used for measuring the position of moving machinery such as valves, penstocks, doors, gates and the like over the full range of movement shall be of the non-contact Magnetic Coded or Linear Variable Differential Transformer (LVDT) types. Contact sensors shall be avoided due to their susceptibility to damage and their tendency to fall out of adjustment.

Where radial position measurements are required, rotary absolute or incremental encoder systems shall also be considered as a valid choice. When used, consideration must be given for provision of a reference or home position that facilitates manual and/or automatic checking that the measurement is valid.


Sensors shall be mounted so as to minimise the risk of damage from contact with moving parts.

Mountings shall be adjustable, with target distance set at approximately the mid-point of the sensing range of binary devices, and the ability to adjust analog devices to measure across the full working range.

Where shaft encoders are used, the mechanical connection of the shaft shall be through an approved coupling device that provides adequate protection and flexibility to provide long term reliability of the measurement.




3.10 Analytical Instruments 3.10.1 General

The following sections outline general requirements for the types of analytical instruments most commonly encountered in water and wastewater applications. Where applicable, instruments shall be designed in accordance with these requirements and selected from the Corporation’s Approved Equipment List.

Instruments not covered in this section or in the Approved Equipment List shall be selected by the Designer at the Engineering Design Stage depending on the particular requirements. The Designer shall justify the instrument selection as part of the Engineering Design Report.

Analytical measurements fall into 3 broad categories:

1. In-Line – where the analyser sensor is directly immersed into or in contact with the process media to be measured.

This type of installation can offer some advantages such as fast response, However, it is important to remember that analytical measurements can be affected by changes of flow, pressure and temperature, therefore In-Line analysers should only be considered if these parameters will remain stable.

Safe removal or retraction of the analyser from the process to facilitate maintenance and/or calibration is a required consideration as part of the installation design.

2. On- Line – where the analyser is mounted in a bypass or take offline from the main process. Speed of response is almost the same as In-Line, however, it provides the advantage of process media undergoing some simple conditioning such as flow control or de-gassing

This choice of analyser provides simple conditioning which can improve the measurement. It provides location of the instrument away from the process, which may be preferred to provide ease of access, a controlled environment or availability of other services. In this case both delivery and return or disposal of the sample will need to be considered as part of the system design.

3. At Line – where the analyser requires a sampling system that can perform more complex conditioning of the sample such as batching fixed volumes or mixing with reagents

These types of analysers tend to be expensive in terms of both installation and operating costs. For this reason they are not preferred but for certain measurements they still remain the best choice for providing accurate measurements that are reliable as long as the analyser is maintained as per the manufacturer’s recommendations.

Designers specifying these analysers shall consider sample points, sample delivery, analyser location, analyser footprint, services required, control and data interfacing, sample disposal and maintenance provisions.

3.10.2 Ammonia Analysers

3.10.2.1 Application Ammonia concentrations in both water supply and wastewater treatment can be a useful measurement in order to determine how effective water treatment processes are working. In drinking water ammonia can compromise disinfection efficiency and cause taste and odour problems. In wastewater the treatment




processes can be monitored and controlled to ensure compliance with local discharge consent limits and current legislation to control what is a significant pollutant.

There are two main methods of ammonia measurement: ion-selective sensors or colorimetric sensors.

Ion-selective analysers generally comprise of one or a number of sensor electrodes which are immersed into the process water. There are types that are directly immersed into the process, otherwise the process water is sampled from the process stream and can either be a continuous controlled flow or a sampled volume, in the case of a sampled volume this allows the sample to be pre-treated with a chemical reagent.

Colorimetric analysers generally comprise of a sampling system that is able to deliver a sample of the process fluid at a fixed volume, this sample is prepared and pre-treated with reagents in order to provide a fluid suitable for measurement. The measurement is then carried out by optical analysis of the sample, absorption of UV/visible radiation is proportional to concentration as set down by the Beer Lambert law.

In general, ion-selective analysers offer relatively simple installation whereas colorimetric analysers can be quite complex systems which offer greater accuracy at the expense of a high investment in both capital and operational costs.

3.10.2.2 Requirements Ammonia analysers shall consist of a sensor and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 10m length. Alternatively, the analyser shall be a complete self-contained unit that carries out sample handling, pre-treatment, sample disposal, measurement, display, control and output functions, when provided with the necessary external supply and output connectivity.

Sensor, converter/transmitter or analyser shall be suitable for the environmental conditions specified in Section 2 with a degree of protection not less than IP56. Converter/transmitters shall be suitable for mounting out of doors to suit the application.

Design of the sensor shall minimise fouling. Manual cleaning shall not be required more often than every 1 month. Mechanical cleaning systems shall not be used unless considered to be part of the analyser design.

The sensor, converter/transmitter or analyser shall incorporate compensation for temperature and optional provision for pH measurement. Temperature compensation shall be by means of an inbuilt RTD element. If optioned the analyser system shall be capable of accurately measuring pH between 0 and 14. It shall include digital displays of Ammonia concentration in mg/l, fluid temperature in degC, and where required pH.

Measurement accuracy shall reproduce an Ammonia measurement of ±0.25mg/l, with a measurement drift of <5% per month.

The analyser shall incorporate the following features:

• Configuration shall be fully adjustable to suit the application;

• Analyser output shall be linear;

• Analysers shall incorporate local indication of process variables in engineering units;

• Analysers shall provide an isolated 4-20 mA analogue output for each process variable as required. Alternatively, a Profibus interface may be used, depending on requirements;

• Calibration adjustments shall have a simple operator interface;

• Self-monitoring and diagnostic functions;




3.10.2.3 Installation For continuous measurement the sensor shall be immersed in the process, or the process shall be sampled via a pipeline which provides control of the process flow rate. If required the manufacturer’s sensor assembly shall be integrated into the sample line to provide the recommended measuring conditions.

For batch sample measurement the analyser shall be mounted in an analyser building/enclosure within 10m of a suitable process connection. The analyser shall be configured to safely dispose of any treated process sample fluid.

The analyser selection shall include considerations for the application such as process conditions, contamination, operability and maintainability.

Analysers shall be installed strictly in accordance with the manufacturer’s recommendations.

Analysers shall be installed so that they can easily undergo inspection, cleaning and maintenance procedures.

3.10.3 Chlorine Analysers

3.10.3.1 Application Chlorine is a widely used disinfection agent used in a variety of water treatment processes, it is therefore useful in many situations to provide a measurement of Chlorine concentration for monitoring and control of these processes.

Two variations on the Chlorine measurement can be used in differing circumstances, Free Chlorine for simple water disinfection applications and Total Chlorine when there needs to be consideration of the bound chlorine components (chloramines) in addition to the free chlorine components.

There are two main methods of continuous chlorine measurement: amperometric membrane covered sensor and polarographic sensor.

Amperometry has the sensors protected behind a permeable membrane which is in direct contact with the water to be measured. The sensors consist of electrodes contained in an electrolyte filled housing which is separated from the water by a permeable membrane. The chlorine compounds contained in the medium diffuse through the membrane and cause an electrochemical reaction between the electrodes; the resulting current is measured as a primary signal. Amperometric sensors are a well proven principle, by the nature of their construction they require periodic maintenance such as electrolyte replenishment and membrane replacement in order to retain accuracy and reliability. Accuracy of amperometric analysers is dependant upon the pH of the water. The membrane is sensitive only to HClO which is present when the sample is below pH 5.5. As potable water is above pH 5.5, where a combination of HClO and ClO are present, it is advisable to ensure a working pH analyser is utilised for compensation of the measurement.

Polarographic sensors are in direct contact with the water to be measured and consist of a rotating indicator electrode and a fixed counter electrode. These electrodes are used to measure the diffusion current which flows when the chlorine is subjected to electrolytic reduction. The rotating parts required for these types of sensors prevent the ability to measure a pressurised sample, therefore they must be installed In-Line to enable pressure and flow control. The benefit of rotating electrodes is that the sensor becomes self-cleaning, thus significantly reducing maintenance. Cleanliness is essential for good chlorine measurement.

In general, amperometric sensors offer simple installation whereas polarographic sensors offer higher reliability and lower maintenance, faster response time and a quick post-maintenance measurement recovery.

There are also methods of non-continuous chlorine measurement based upon the colorimetric measurement principle. These types of instruments are available in the form of laboratory, portable, handheld or batch sample analysis, and utilize the addition of reagents to a sample of the process water




in order to provide a colour change that can be analysed to determine chlorine concentration. This method is best suited as a reference measurement rather than an online measurement due to the requirements of sampling preparation, reagent addition, sample disposal, cleaning and maintenance. Discoloration of the sample cell caused by mineral content will adversely affect the measurement.

3.10.3.2 Requirements Chlorine analysers shall consist of a sensor and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 10m length.

Sensor and converter/transmitter shall be suitable for the environmental conditions specified in Section 2 with a degree of protection not less than IP56. Converter/transmitters shall be suitable for mounting out of doors to suit the application.

When utilising amperometric types, design of the sensor shall minimise fouling of the membrane. Manual cleaning shall not be required more often than every 1 month. Mechanical cleaning systems shall not be used unless considered to be part of the analyser design (e.g. glass beads on rotating electrode).

The sensor and converter/transmitter shall incorporate compensation for temperature and optional provision for pH measurement. Temperature compensation shall be by means of an inbuilt RTD element. If optioned the analyser system shall be capable of accurately measuring pH between 0 and 14. It shall include digital displays of Chlorine concentration in mg/l, fluid temperature in degC, and where required pH.

Measurement accuracy shall reproduce a Chlorine measurement of ±0.15mg/l, with a measurement drift of <2.5% per month.





• Analysers shall provide an isolated analog output for each process variable as required;



3.10.3.3 Installation The sensor shall be immersed in the process via a sample line which provides control of the process flow rate. If required, the manufacturer’s sensor assembly shall be integrated into the sample line to provide the recommended measuring conditions.

The sensor selection shall include considerations for the application such as measuring range and contamination.

Sensors shall be installed strictly in accordance with the manufacturer’s recommendations.

Sensors shall be installed so that they can be easily withdrawn for inspection, cleaning and maintenance.




3.10.4 Chlorine Gas Detectors

Refer to DS 70-02 Chlorine Leak Detection Standard (N#58549245)

3.10.5 Conductivity Analysers

3.10.5.1 Application

The main application of conductivity analysers is in water treatment, where they may be used:

• To monitor the conductivity or total dissolved solids (TDS) in raw water or treated water;

• To monitor the performance of reverse osmosis (RO) units.

There are two main methods of continuous conductivity measurement: direct electrode measurement and inductive(toroidal) measurement.

Direct electrode-type analysers measure the resistance between electrodes in direct contact with the water. Both two-electrode and four-electrode analysers are available. Two-electrode analysers measure the resistance between electrodes with a known geometry. They are useful for very low conductivity applications (e.g. ultra-high purity water) but are less robust and more susceptible to fouling. Four-electrode analysers operate by passing a controlled current between the outer electrode pair and measuring the resultant potential difference between the inner electrode pair. They are less susceptible to fouling and are suited to medium to high conductivity applications.

Inductive-type analysers consist of two parallel coils immersed in the water. An alternating current is applied to one coil, inducing a weak current into the surrounding water. The induced current, in turn, induces a voltage into the other coil which is related to the water’s conductivity. Because there are no electrodes in contact with the water, inductive instruments are much more robust and less susceptible to fouling. However, they are less sensitive than electrode types and are best suited to medium and high conductivity applications.

In general, inductive analysers shall be used for raw water and treated water with conductivities of 100μS/cm (micro Siemens per centimetre) or above and two- or four-electrode analysers shall be used where conductivities are likely to be less than 100μS/cm, e.g. demineralised water and output of RO units. However, this is not an absolute rule and each case shall be considered on its merits.

3.10.5.2 Requirements

Conductivity analysers shall consist of a sensor and a transmitter unit. Sensors shall be suitable for connection to the transmitter by a cable of up to 30m length for electrode types or 15m for inductive types.

Sensor and transmitter shall be suitable for the environmental conditions specified in Section 2 with a degree of protection not less than IP56. Transmitters shall be suitable for either surface or in-panel mounting to suit the application.

Conductivity is strongly temperature dependent. Therefore, the sensor shall incorporate temperature compensation by means of an inbuilt RTD element and the transmitter shall provide for display of both conductivity and water temperature.





The analyser system shall be capable of accurately measuring conductivity over a range appropriate to the application. Where required it shall also be able to be calibrated in, and to display, TDS concentration in parts per million. Measurement accuracy, after calibration, shall be ±0.5% of range.

The transmitter shall incorporate the following features:

• Digital displays of conductivity in Siemens, TDS concentration in ppm and/or water temperature in degC as required;

• An isolated analog output proportional to conductivity in Siemens or TDS concentration in ppm as required;

• Where required, a second analog output proportional to water temperature;

• Self-monitoring and diagnostic facilities;


Sensors shall be installed strictly in accordance with the manufacturer’s recommendations, in particular with regard to spacing from pipe walls and surfaces and separation from other fittings to ensure that the cell constant is maintained at its design value. Where high accuracy is required, in situ calibration with a conductivity standard or grab sample may be necessary.


3.10.6 Dissolved Oxygen Analysers


Dissolved oxygen analysers play an important role in the secondary treatment process of wastewater treatment plants. They are used to monitor and control the dissolved oxygen concentration in the mixed liquor, ensuring that it is high enough to provide satisfactory treatment without wasting energy through over-aeration. Secondary treatment typically consumes about half of the total energy used in wastewater treatment plants, so accurate control of dissolved oxygen levels has a significant effect on plant operating costs.

There are two main methods of continuous dissolved oxygen measurement: amperometric membrane covered sensors and optical sensors.

Amperometric membrane covered sensors are in direct contact with the water to be measured and consist of electrodes contained in an electrolyte filled housing which is separated from the water by a permeable membrane. The process water is therefore able to penetrate the membrane and cause an electrochemical reaction between the electrodes, the number and type of electrodes may vary depending on the sensor construction. Amperometric sensors are a well proven principle. By the nature of their construction they require periodic maintenance such as electrolyte replenishment and membrane replacement in order to retain accuracy and reliability.

Optical sensors are in direct contact with the water to be measured and consist of a light emitting and measuring probe working on the fluorescence principal. These sensors can take the form of a special covering cap or a membrane/electrolyte arrangement, each of these methods forms a junction that contains oxygen molecules from the process. The fluorescence characteristics of the oxygen molecules are directly related to the oxygen concentration, this can be measured using fluorescence quenching measurements.




In general, amperometric sensors offer higher accuracy, whereas optical sensors offer faster response times and longer-term stability with lower maintenance.


Dissolved oxygen analysers shall consist of a probe which is immersed in the mixed liquor and a separately mounted converter/transmitter. Sensors shall be suitable for connection to the converter/transmitter by a cable of up to 10m length.

The sensor shall utilise a replaceable cartridge with a service life of not less than two years. The complete analyser system shall include provision for automatic calibration against air with a recommended recalibration interval of not less than 3 months.

Design of the sensor shall minimise fouling of the membrane. Manual cleaning shall not be required more often than every 3 months. Mechanical cleaning systems shall not be used.

The sensor and converter/transmitter shall incorporate compensation for temperature, barometric pressure and salinity. Temperature compensation shall be by means of an inbuilt RTD element. The analyser system shall be capable of accurately measuring dissolved oxygen concentrations of between 0 and 20 mg/L. It shall include digital displays of dissolved oxygen concentration in mg/L and, where required, fluid temperature in degC. Measurement accuracies shall be ±0.1 mg/L and ±0.5 degC or better.


• Dissolved oxygen span adjustable from 2 to 20 mg/L;

• Digital displays of dissolved oxygen concentration in mg/L and, where required, fluid temperature in degC;

• An isolated 4-20mA output proportional to dissolved oxygen concentration in mg/L;

• Where required, a second isolated 4-20mA output proportional to fluid temperature. Alternatively, a Profibus interface may be used, depending on requirements;

• Self-monitoring and diagnostic facilities.


Sensors shall be installed strictly in accordance with the manufacturer’s recommendations. When used in aeration tanks or similar situations, they shall be of the floating type mounted on a suitable swing arm or tether and designed to float just beneath the water surface.

Sensors shall be installed so that they can be easily withdrawn for inspection, cleaning and maintenance. When installed through the covers of covered tanks, the penetrations shall be provided with an effective odour seal which still allows the sensor to be withdrawn.

3.10.7 Flammable Gas Detectors


The main application of flammable gas detectors is in wastewater treatment where they are used to detect potentially dangerous releases of biogas (consisting mainly of methane) from digesters, storage vessels, gas compressors, engine rooms, pipe work and other areas where gas is generated, stored or used.




Gas detectors may also be required for monitoring other types of hazards such as heaters, boilers, paint stores, laboratories, electro-chlorinators and the like where flammable gases or vapours such as natural gas, hydrogen, LPG or solvent vapours may be released.

Both fixed and portable gas detectors are available, however this section deals only with fixed detectors.


In wastewater applications including sewage pump stations, infra-red (IR) detectors shall be used in preference to catalytic detectors (e.g. SnO2 thin films) since the latter are susceptible to poisoning by the traces of H2S commonly associated with wastewater. However, in other applications without traces of H2S such as H2 gas that does not absorb IR energy, catalytic detectors shall be used. The catalytic detectors shall have a useable life of greater than 2 years. Infra-Red detectors shall have a useable life of greater than 5 years.

Generally, detectors shall rely on natural diffusion of the gas from the point of release to the detector. Aspirated detectors, in which a pump is used to draw an air sample through the detector, shall not be used unless there are particular reasons for doing so (e.g. requirement for an unusually fast response time).

Detectors shall be calibrated against gas of similar composition to that expected in service. Detectors shall be capable of accurately measuring flammable gas concentrations of up to 100% of the lower explosive limit (LEL). Concentrations greater than 100% of LEL shall cause the instrument to read full-scale. Measurement accuracy shall be ±2% LEL or better over the measuring range with a zero drift not exceeding ±1% of LEL per year.

The detector shall incorporate the following features:

• Certified intrinsically safe, category Ex ia, with current AUS Ex, ANZEx or IECEx certification;

• Warning and emergency alarm set points, each adjustable over the range from 5% to 50% of LEL;

• Audible and visible warning and emergency alarms at the detector itself, which can only be reset manually;

• An analog output proportional to gas concentration as a percentage of LEL;

• Remote alarm contacts for warning and emergency alarms;

• Fail-safe self-monitoring and diagnostics to ensure that a faulty detector cannot indicate a safe condition.

In mission critical processes where there is a high risk of gas explosion, a redundant detector shall be incorporated into the design and installation.


Sensors shall be located in areas where there is a likelihood of release and particularly in closed or confined areas where ventilation may be limited. Numbers and locations of sensors shall be determined after taking into account:

• The locations of potential leakage points;




• The type and adequacy of ventilation in the area;

• The density and dispersion characteristics of the flammable gas (e.g. methane is lighter than air and will tend to rise while LPG is heavier than air and will tend to fall or accumulate at low points);

• The need to detect any accumulation of gas in poorly ventilated areas before it creates a serious hazard;

• The occupancy of the building or facility (e.g. a continuously occupied building or an unattended pump station that is visited only occasionally);

• The effect that failure or temporary removal of a sensor would have on area protection.

Sensors require regular testing and inspection. They shall be located so as to facilitate maintenance access.

3.10.8 Fluoride Analysers

3.10.8.1 Application Water fluoridation is the adjustment of fluoride in drinking water to a level that provides health benefits to consumers. It is included within the Australian Drinking Water Guidelines framework and is therefore widely adopted across public drinking water supplies. Adjustment requires chemical addition to the water; a measurement of fluoride is required in order to control this adjustment to safe and effective levels.

Fluoride measurement analysers use ion selective technology to measure the fluoride concentration in the water. The analysers generally comprise of one or a number of sensor electrodes which are immersed into the process water. The process water is sampled from the process stream and can either be a continuous controlled flow or a sampled volume, in the case of a sampled volume this allows the sample to be pre-treated with a chemical reagent.

Continuous measurement sensors offer the benefits of being lower cost, reagent free, fast response, lower maintenance, easy and efficient to maintain. The limitation of these sensors is however that certain frame conditions must be observed, consideration shall be given to the pH, conductivity and chemical compounds that can bind or mask the fluoride ion, e.g. Aluminium, Iron and Calcium.

Analysers with sensors that are subjected to a controlled volume of sampled water, use a Total Ionic Strength Adjustment Buffer (TISAB) pre-treatment method, this provides some assurance that the analyser can provide an accurate measurement on processes that are outside the limitations of a continuous measurement analyser.

3.10.8.2 Requirements Fluoride analysers shall consist of a sensor and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 10m length. Alternatively, the analyser shall be a complete self-contained unit that carries out sample handling, pre-treatment, sample disposal, measurement, display, control and output functions, when provided with the necessary external supply and output connectivity.


The sensor, converter/transmitter or analyser shall incorporate compensation for temperature and optional provision for pH measurement. Temperature compensation shall be by means of an inbuilt RTD element. If optioned the analyser system shall be capable of accurately measuring pH between 0 and 14.




It shall include digital displays of Fluoride concentration in mg/l, fluid temperature in degC, and where required pH.

Measurement accuracy shall reproduce a Fluoride measurement of ±0.15mg/l, with a measurement drift of <2.5% per month.





• Analysers shall provide an isolated analog output for each process variable as required.;



3.10.8.3 Installation For continuous measurement the sensor shall be immersed in the process via a sample line which provides control of the process flow rate. If required, the manufacturer’s sensor assembly shall be integrated into the sample line to provide the recommended measuring conditions.





3.10.9 Hydrogen Sulphide Gas Detectors


Hydrogen sulphide (H2S) is a flammable and highly toxic gas that can cause injury at concentrations as low as 10 parts per million (ppm). It is produced by the decomposition of organic material and may be found in dangerous concentrations in sewers, sewage pump stations and certain areas of wastewater treatment plants. The biogas produced by sludge digestion usually contains H2S, often in potentially lethal concentrations of 1,000ppm or more.

Raw groundwater may also contain small amounts of dissolved hydrogen sulphide which is released when the groundwater is exposed to air.

In low concentrations H2S is usually easy to detect due to its characteristic “rotten egg” smell. However, in higher concentrations it can paralyse the sense of smell, making it even more dangerous.

Although H2S is also flammable, the concentrations encountered in water and wastewater treatment are usually far below the lower explosive limit (LEL). The main risk with H2S is due to its toxicity.




Hydrogen sulphide gas detectors shall be used to detect accumulation, leaks or accidental release of hydrogen sulphide gas from sewers, vessels and pipe work.


Hydrogen sulphide gas detectors shall consist of a monitor unit and gas sensor. Depending on the application the sensor may be either remote-mounted or integral with the monitor unit. Remote-mounted sensors shall be suitable for connection to the monitor unit by a single-pair cable of up to 30m length.

Sensor and monitor shall be suitable for the environmental conditions specified in Section 2 with a degree of protection not less than IP56. Sensor and monitor electronics shall be resistant to attack by H2S. Monitors shall be suitable for either surface or in-panel mounting to suit the application.

The sensor shall incorporate temperature compensation and shall not require replacement more often than every two years in normal service.

The detector shall be capable of accurately measuring hydrogen sulphide concentrations of up to 50ppm and shall include a digital display of concentration in ppm. Concentrations greater than 50ppm shall cause the instrument to read full-scale. Measurement accuracy shall be ±1ppm or better over the measuring range with a zero drift not exceeding ±1ppm per year.

The detector system shall incorporate the following features:

• 2-wire instrument;

• Isolated analog output proportional to hydrogen sulphide concentration in ppm;

• Detector fault monitoring;

• Intrinsically safe (Ex ia) with current ANZEx, IECEx or AUS Ex certification.


Sensors shall be located in areas where there is a likelihood of release or accumulation, and particularly in closed or confined areas where ventilation may be limited. Numbers and locations of sensors shall be determined after taking into account:

The locations of potential accumulation, release or leakage points;

The type and adequacy of ventilation in the area;

The density and dispersion characteristics of hydrogen sulphide gas, which is heavier than air and will tend to accumulate at low points;

The need to detect any accumulation of gas in poorly ventilated areas before it creates a serious hazard;

The effect that failure or temporary removal of a sensor would have on area protection.

Sensors require regular testing and inspection. They shall be located so as to facilitate maintenance access.




3.10.10 Monochloramine Analysers


Monochloramine measurements are useful in the process of chloramination, which is the practice of using a combination of chlorine and ammonia for disinfection of drinking water supplies. Chloramination is most likely to be used when transport or storage times before use are longer than chlorine disinfection alone can remain effective. The measurement is valuable due to the complex chemical reactions, it is important to maximize the production of monochloramine without producing other types of chloramines. This will minimize the presence of free ammonia and prevent the overdosing of chlorine; the Chlorine Breakpoint Curve should be referenced for best illustration of the phenomena.

There are two main methods of monochloramine measurement: ion-selective sensors or colorimetric sensors.

Ion-selective analysers generally comprise of an amperometric sensor electrode which are immersed into the process water. The process water is sampled from the process stream and can either be a continuous controlled flow or a sampled volume, in the case of a sampled volume this allows the sample to be pre-treated with a chemical reagent.

Colorimetric analysers generally comprise of a sampling system that is able to deliver a sample of the process fluid at a fixed volume, this sample is prepared and pre-treated with reagents in order to provide a fluid suitable for measurement. The measurement is then carried out by optical analysis of the sample, absorption of UV/visible radiation is proportional to concentration as set down by the Beer Lambert law.

In general, ion-selective analysers offer relatively simple installation whereas colorimetric analysers can be quite complex systems which offer greater accuracy at the expense of a high investment in both capital and operational costs.


Monochloramine analysers shall consist of a sensor and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 10m length. Alternatively, the analyser shall be a complete self-contained unit that carries out sample handling, pre-treatment, sample disposal, measurement, display, control and output functions, when provided with the necessary external supply and output connectivity.

Sensor, converter/transmitter, or analyser shall be suitable for the environmental conditions specified in Section 2 with a degree of protection not less than IP56. Converter/transmitters shall be suitable for mounting out of doors to suit the application.


The sensor, converter/transmitter or analyser shall incorporate compensation for temperature and optional provision for pH measurement. Temperature compensation shall be by means of an inbuilt RTD element. If optioned the analyser system shall be capable of accurately measuring pH between 0 and 14. It shall include digital displays of Monochloramine concentration in mg/l, fluid temperature in degC, and where required pH.

Measurement accuracy shall reproduce a Monochloramine measurement of ±0.25mg/l, with a measurement drift of <5% per month.








• Analysers shall provide an isolated analog output for each process variable as required.;




The process shall be sampled via a pipeline from a suitable process connection within 10m of the analyser location. Control of the sample flow rate shall be included and if required the manufacturer’s sensor assembly shall be integrated into the sample line to provide the recommended measuring conditions.





3.10.11 pH/ORP Analysers

3.10.11.1 Application pH and ORP are different variables, the principle of measurement however are the same such that most manufacturers offer analysers that can measure either pH or ORP, or even both measurements depending upon probe selection.

The principle of measurement is based upon the measurement of potential difference between a reference half-cell and a measuring half-cell. The reference half-cell potential is independent from the pH/ORP value of the process, whereas the measuring half-cell is dependent on the pH/ORP value of the process. Therefore, the difference in these half-cell potentials is directly related to the pH/ORP of the process and can be measured in mV. The pH/ORP transmitter is then able to convert the raw mV readings into calibrated pH/ORP ranges.

pH and ORP measuring probes differ in their construction, glass pH probes acting as a membrane for the measuring half-cell, whereas glass ORP probes have a noble metal in direct contact with the process for the measuring half-cell.

There are a number of different types of pH/ORP probe - Ion-sensitive, Field Effect Transistor (ISFET) and pH sensitive ceramic are all available technologies . The most common and cost-effective being glass. Glass electrodes offer fast response, full measuring of pH range (0 to 14), they are suitable for




use in a wide range of temperatures and process medium, have low cost consumable replacements and are simple to maintain.

Manufacturers offer a wide range of housings and mounting arrangements to suit a variety of processes and applications.

3.10.11.2 Requirements pH/ORP analysers shall consist of a sensor and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 30m length.

Design of the sensor shall minimise fouling of the membrane to maximise time between maintenance.. Mechanical cleaning systems shall not be used.

The sensor and converter/transmitter shall incorporate compensation for temperature. Temperature compensation shall be by means of an inbuilt RTD element. The analyser system shall be capable of accurately measuring pH between 0 and 14 or ORP between -1500 and +1500 mV. It shall include digital displays of pH/ORP and, where required, fluid temperature in degC. Measurement accuracies shall be ±0.5% pH/ORP range and ±0.5 degC or better.



• Transmitter output shall be linear;

• Transmitters shall incorporate local indication of process variables in engineering units;

• Transmitters shall provide an isolated analog output for each process variable as required;

• Calibration functions shall follow a simple menu structure with selectable or programmable buffer solution values, Temperature Compensation selection, and diagnostic messages in case of calibration failure;


3.10.11.3 Installation The sensor shall be immersed in the process either directly, via a bypass sample line or through a retractable immersion mounting arrangement.

The sensor selection shall include considerations for the application such as stability, temperature, contamination, poisoning and risk of abrasion. This will influence the type selection of both the sensor and the sensor holder assembly, manufacturer recommendations or advice may need to be sought to ensure correct selection.



3.10.12 Turbidity / Suspended Solids Analysers

For water treatment plant analysers also refer to “Specification for the Selection of Appropriate Turbidity Analysers (Nexus #107885466)

3.10.12.1 Application Turbidity / Suspended Solids measurement is important for monitoring the particulates contained within water at a number of different stages of water lifecycle. The measurement provides valuable information





to report changes in source water quality or can be utilized to determine effects or requirements of water and wastewater treatment processes.

Turbidity / Suspended Solids is an optical impression of particles in a transparent suspension, so a light source is used as the basis for measurement. There are a number of different manufacturers who in turn have employed various methods of utilizing optical analysis of a process fluid.

The differentiation between Turbidity and Suspended Solids is:

• Turbidity seeks to determine the effect suspended particles have on light passing through a liquid (reflected light scattered at 90o), with results reported in NTU (Nephelometric Turgidity Units)

• Suspended Solids seeks to quantify the number of particles in suspension in a liquid, with results reported in mg/l or ppm.

Turbidity units of measure are NTU values, most commonly used in water treatment industry primarily because of the nephelometric reference standards that allow for very quick calibration checks and laboratory measurements. Suspended Solids units of measure are mg/l and would more commonly be used in wastewater treatment primarily because of correlation to the total weight of particles in suspension. There is however no reference standards as it is calibrated to individual processes, laboratory measurements can take from 6 to 24hours.

Sensor variations include process inline or immersion, process sample bypass line and process piped to flow through sensor. In all cases the optical sensors are in direct contact with the water to be measured and consist of a light emitting and measuring probe working on the reflected or backscatter light principle.

The reflection of the light is a function of the size and shape of the particles which can present challenges if measuring a process where the particulate types are changing. The measurement is also greatly influenced with the presence of bubbles, so it is important that the process or sample has no gas content.

3.10.12.2 Requirements Turbidity / Suspended Solids analysers shall consist of a sensor/detector and a separately mounted converter/transmitter which shall be suitable for connection to the sensor by a cable of up to 10m length. Alternatively, the analyser shall be a complete self-contained flow through unit that handles the sample, measurement, display and output functions within a single unit.

Design of the sensor shall minimise fouling, an integrated wiper mechanism for keeping the optics clean and free from bubbles may be employed. Mechanical cleaning systems shall not be used unless considered to be part of the analyser design.

Measurement accuracy shall reproduce a Turbidity measurement of ±0.15NTU or Suspended Solids measurement of <5% of the measured value.





• Analysers shall provide an isolated analog output for each process variable as required;






3.10.12.3 Installation The sensor shall be immersed in the process either directly, via a bypass sample line, sample line piped to a flow through sensor or through a retractable insertion mounting arrangement.

The sensor selection shall include considerations for the application such as measuring range, contamination, process conditions and gas entrapment. This will influence the type selection of both the sensor and the sensor holder assembly, manufacturer recommendations or advice may need to be sought to ensure correct selection.



Meters need to be installed so they are not exposed to excessive temperature, which causes readings to drift. Temperature should always be between 0-40˚C with an optimal range being 15-30˚C.

3.11 Control Valves Refer to Design Standards DS 40-07 and DS 31-02.

3.12 Modulating Valves Refer to Design Standards DS 40.07 and DS 31-02.

3.13 Solenoid Valves 3.13.1 Applications

Solenoid valves may be used in such applications as pilot valves for pneumatic and hydraulic valves and actuators, control of pump gland water supplies, control of lube oil supplies, control of flushing and spray water supplies and the like.

3.13.2 General Requirements

Solenoid valves shall be suitable for installation outdoors without additional weather protection, with a minimum degree of protection of IP65. A higher degree of protection shall be specified if required by the application.

Valve materials shall be selected to suit the fluid and the application. As a minimum, valves shall be of 316 stainless steel construction with nitrile rubber or similar hydrocarbon-resistant diaphragm and seals.

Valves shall be suitable for mounting in any position.

Pressure ratings shall be as required by the application, with an overpressure tolerance of not less than 125% of the normal maximum operating line pressure.

3.13.3 Operation

Valve operation shall be such that failure of the solenoid supply shall not lead to an unsafe condition. In general, this implies that valve action shall be energise-to-open, spring-to-close unless process conditions require otherwise.




Manual operators shall be provided only where required for process reasons.

3.13.4 Electrical

Coils shall be of the encapsulated type. It shall be possible to replace the coil with the valve in place and without the need to disturb process connections.

Solenoid operating voltage shall be 24V DC with a minimum voltage tolerance of ±10%. Coil insulation shall be Class F as a minimum. Coils shall be suitable for switching directly from Controller outputs.

Coils shall be rated for continuous energisation at maximum ambient temperature and shall be provided with surge suppression to limit voltage spikes.

The terminal compartment shall be integral with the solenoid valve and shall include an earthing connection. It shall be water-tight and shall accept an ISO M20 male threaded conduit or cable gland.

3.14 Valve Actuators Refer to Design Standards DS 21, DS 40.07 and DS 31-02.

3.15 Proportional/Integral/Differential (PID) Controllers 3.15.1 Application

PID control is commonly used in a wide variety of processes for automatic control of such things as level, flow, pressure, temperature, position, dosing rate and the like.

For treatment plants with a PLC-based plant control system, PID control shall be performed by the appropriate plant area control system PLC rather than by dedicated controllers. Reference should be made to Design Standard DS 40-01.

However, there are some situations (e.g. small or isolated metering, dosing or control stations) where the installation of a full-scale plant control system is not warranted. In such cases the use of dedicated or small PLC-based PID controllers may be justified.

3.15.2 General Requirements

A PID controller (also called a “three-term” controller) compares the measured value of a process variable (the process value or PV) with the desired value (the set point or SP). The result of this comparison (the controller output) is used to control an actuating device or similar in such a way as to minimise the difference between the SP and the PV.

The proportional, integral and differential controller terms must be adjusted or “tuned” to minimise the controller’s steady-state error and to optimise its dynamic response.

3.15.3 Specifications

PID controllers shall be digital and may be either stand-alone or incorporated as PID algorithms in a PLC which may also perform other control and monitoring functions.

PID controllers shall be specified to have the following characteristics.

Set point accuracy: +/- 0.5% of scale range.




Proportional action: 2% - 300% range.

Integral action time: adjustable in the range of 0.1 min. to 50 minutes with integral action de-saturation and facilities to bypass integral action altogether.

Derivative action: facilities to bypass derivative action altogether.

Output Control Signal: 4-20 mA or pulse width modulated DC depending on the requirements of the final control device.

Other features: a) operator accessible bumpless auto/manual change over with set points indicated continuously;

b) outputs indicated continuously;

c) for controllers on manual, restoration to previous output within 1% after power restoration.




4 DESIGN DOCUMENTATION

4.1 Design Process The design of instrumentation systems shall follow the process set out in the Corporation’s Design Standard DS 40.

4.2 Drawings Drawings shall be prepared in accordance with the requirements of DS 40 and DS 80.

The drawings to be prepared are those listed in DS40 with the inclusion of the following information:

For major instrumentation systems, signalling block diagrams showing signal types, levels and characteristics, scaling factors, protocols, bandwidths, losses, signal screening etc;

For major process control systems, control block diagrams showing process gains, dead times, process capacity, PID settings, etc.

Where fieldbus (eg HART, Modbus, Profinet or Profibus) is used as an alternative to 4-20mA instruments, a loop drawing shall be prepared that shows:

• the fieldbus network it is attached to

• the fieldbus address

• the Controller, rack, slot and channel the fieldbus is connected to

• any intervening repeaters or couplers

• the first address within the Controller that the fieldbus value and status bytes are written to. E.g. Siemens DByy.DBDyyy, GE Ryyyy, Koyo Vyyyy

The purpose is to replicate the functionality and information used by fault finding personnel that was previously found in the 4-20 mA loop drawings.

This is in addition to the Profibus drawings specified on DS43-04 which do not include the destination within the Controller of the smart instrument data.

4.3 Schedules Schedules (lists) shall be prepared in accordance with the requirements of DS40 and the Corporation’s Design Standard DS 28.

The schedules to be prepared are those described in Section 2.4 of DS 28 with the inclusion of the following information:

• Instrument calibration and range details;

• Coding and configuration records (including computer programs if applicable) for all control devices.




4.4 Instrument Data Sheets The Designer shall prepare, complete, check and sign off instrument data sheets for each instrument type. Instrument data sheets shall be in accordance with TS40-03.

The Designer shall produce and finalise the instrument data sheets during the Detail Design stage of the project. This stage shall be as described in DS40.

The Designer or Constructor shall verify the Instrument Vendor information for each instrument type prior to purchasing.

The Datasheets, along with the Instrument Schedule, shall be used for procurement, construction, installation, and commissioning of plants. The final, as constructed, instrument data sheets after commissioning shall be submitted to the Water Corporation as part of the site Operations and Maintenance Manuals.

If there is no typical data sheet that is applicable the Designer shall prepare a suitable data sheet in a similar format to that in T40-03 and shall submit a copy to the Principal SCADA Engineer for review.




END OF DOCUMENT

Documents

DESIGN STANDARD DS 40-09