Hipps - Azade to Ceo

HIPPS• Introduction• Configuration • Specification • Codes & Standards

•Flaring of hydrocarbons causes damage to theenvironment and the CO2 production is not inline with the Kyoto Protocol

•HIPPS prevent over-pressurization by shutting down the source of the high pressure.

A mechanical and electrical safety instrumented system (SIS)

designed to prevent over-pressurization of a plant

with isolating downstream (Piping & Pressure Vessels)

from over pressure

HIPPS closes the source of over-pressure as fast as

possible (within 2 seconds) with at least the same reliability as a safety relief valve

When extremely high pressure and/or flow rate are involved

When Sizing of relief device is difficult to define or inadequate due to chemical reactions or multiphase fluids

On existing systems in order to avoid replacement of flare system when adding new units

Reduces relief load by reducing frequency of overpressure events

Reduces frequency that multiple relief devices will operate simultaneously

Provide protection when a pressure relief device is ineffective

HIPPS are more complex, requiring many components to work as designed

Redundancy, inspection and proof test requirements increase long term operation and maintenance costs

Pressure Range 1480-15000 psi Temperature Ambient Valve sizes 2-52 inches

The HIPPS system is based on

Three pressure transmitters (Initiators) A logic solver Two shutdown valves (Final Elements)

Initiators

Logic Solver

Final Elements

Logic solver

To providing the safety assurance of a pressure-sensitive environment

• Noise reduction• Velocity management

An overall HIPPS loop requirement

Transmitters Manifolds Logic Solver HIPPS Ball Valves Actuators Solenoid valves Communication and sequence of

event registration Plant Resource Manager

Communication Sequence of event Matrix interface

TEXT 1TEXT 2TEXT 3TEXT 4




INPUTS OUTPUTS INPUTS OUTPUTS

















Logic solver

Fail safe outputs

S

SS

S

Process ResourceManagement

DCS

Analog inputsvoting

PV2PV1 PV3

Digital inputsResets

Manifolds for the transmitters have to provide the necessary double block and bleed interlocking 2oo3 arrangement specially for HIPPS

Pressure Measurement Component

To meet over pressure at least in a single instrument in SIL2 loop or two transmitters in SIL3 Loop

Used to detect high pressure

The pressure sensing initiators should be electronic pressure transmitters

Two wire 4-20 mA

Mounted on an Interlock Manifold Wired to separate card in the logic

solver

Most HIPPS applications require 1oo2, 2oo2 or 2oo3 voting transmitters on all field inputs

The 2oo3 voting logic is generally implemented in the logic solver

Reduces the probability to fail on demand (PFD) for the field inputs

Decrease common cause faults, such as plugged process taps

Two methods of process measurement:

Tradition method After evolution method

Traditionally, variables were monitored using discrete switches as the input sensor to the

safety instrumented systems (SIS)

Switches used for three reasons:

Relay systems and early PLCs processed discrete signal much easier than analog signals

Switches were usually less expensive than analog transmitters

The evolution has made it easy to use analog PV inputs

Transmitters can be continuously monitored

A single transmitter providing multiple levels of trip/alarm functions (i.e., low, high and high-high level) can replace multiple switches

Determines the proper steps to make changes to

the final element

The logic solver hardware must be designed to meet the assigned SIL3 as provided in IEC 61508 and

IEC 61511

It can be Relays or PLC

The system consist of a Central Processing Unit (CPU) and fail-safe redundant I/O

IEC 61511 covers the application of electrical, electronic and programmable electronic equip

This standard defines the functional safety requirements established by IEC 61508 in process industry sector

Defines functional safety as: part of the overall safety relating to the

EUC (Equipment Under Control)

The EUC control system which depends on the correct functioning of the E/E/PE safety-related systems

Other technology safety-related systems and external risk reduction facilities

All safety communication between the control unit and the associated I/O cards must be redundant

Control Cabinet can be supplied suitable for hazardous area installation in EEx-d enclosure IP-66 or for safe area installation in standard 19” rack cabinet IP-54

SIL 4 or 3 certification Inherently Fail-Safe Zone2 applications Very high mechanical and electrical robustness High temperature range Very low power consumption Very long technical life span (>30y) Test intervals many years Event Recorder (1ms resolution)

Based on the ANSI/ISA S84.01, IEC 61508, and IEC 61511 the safety logic must be independent from the basic process control system logic

Independence of the safety logic reduces the probability of loss of the basic control

system hardware functioning Independence also reduces the possibility of inadvertent changes to the HIPPS safety functionality occured during modification

of basic process control functions

Performs the necessary steps to bring the process back to a safe state of being

Includes the valve, actuator and solenoids

Generally have a quick quarter-turn on/off ability

Generally have a soft seating

Generally have blow-out proof stems with radial operation

Should be two components, because the single component will not support the safety requirements (series and parallel components)

Designed to be opened against full differential pressure, so that there is no need for a bypass arrangement for pressurization and start-up as typically the case with ball valves

Safety Integrity Level (SIL) (in many HIPPS Systems SIL3)

Process Safety Time (PST) Probability of Failure on Demand

(PFD) Safe Failure Fraction (SFF) Hardware Fault Tolerance (HFT) Risk Reduction Factor (RRF)

The metric for measuring the performance of a safety function is called the average Probability of failure on demand (or PFDavg) and this correlates to the SIL level as follows

PFD=1/2 ( T ) T= Test Interval = Failur Rate

The relationship between the SIL, RRF and PFD

IEC 61508: Functional Safety of Electrical/Electronic/Programmable Electronic Safety Related System

IEC 61511: Functional Safety: safety instrumented systems for the process

industry sector

ANSI/ISA S84.01, Application of Safety Instrumented Systems for the Process Industries

ASME Code Case 2211

API 521

provide alternatives in the design of overpressure protection systems. These alternatives revolve around the use of an instrumented system that exceeds the protection provided by a pressure relief valve and flare system

If you need a pressure relief device for any scenario, it must be sized for the worst case

If no pressure relief device is installed, the MAWP (Maximum Allowable Working Pressure) of the vessel must be greater than the highest pressure reasonably expected

Applies to flare load and header sizing

requires evaluation of relief loads based on credible overpressure scenarios

requires sizing the main flare header for the worst case relieving scenario (involving the simultaneous venting of all affected vessels)

Recommends use of HIPPS only when the use of pressure relief device is impractical

A guide for plant engineers in the design, installation, and operation of pressure-relieving and depressuring systems

Suggests solutions to the immediate design and economic and safety problems involved in pressure relieving discharge systems

Includes a new section on flare gas recovery

General description of the process to be protected

General description of how HIPPS is integrated into the process and other safety systems

The required SIL level of the loop

Specification of the system response time

Detailed specification of the final element (shut-off valve) describing materials, design standards, actuator sizing/integration, details of the instrumentation such as solenoids and actuator

Detailed specification of the pressure transmitters and their safety aspects

Detailed specification of the controller including the required logging, test buttons, and communication to other controllers like the DCS

Components tests and integrated factory acceptance test (FAT) requirements for the complete system

Documentation requirements that may include procedures and checklists for the site acceptance test (SAT) and proof testing of the system

Don’t go shopping for bargains when you want to realize a HIPPS solution.

Go for the balanced solution for both functional and safety requirements.

Be sure there is sole responsibility for your total loop and be sure this is a competent person or company.

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Hipps - Azade to Ceo