Calibration of emission

measurement instruments

Hanna-Mari Kaarre, 33240

Processindustriell mätteknik

Institutionen för kemiteknik

Åbo Akademi

Maj 2013

1

Table of Contents

Foreword ............................................................................................................................... 2

Introduction ......................................................................................................................... 2

General information of calibration .............................................................................. 2

Calibration of instruments .............................................................................................. 3

Gases used in calibration ................................................................................................. 6 Pure gases, including zero check gases ............................................................................... 6 Calibration and span gases ...................................................................................................... 7

Emission measurement instruments .......................................................................... 8 Horiba PG-250 .............................................................................................................................. 8 Horiba EXSA-240CL ..................................................................................................................... 9

References .......................................................................................................................... 11

2

Foreword

This report is part of the course “Processindustriell mätteknik”, and the aim of

this report is to enhance students’ knowledge of calibration of exhaust devices

that are used for ship engines. The report will for example contain general

information of calibration, requirements for calibration set up by The Marine

Environment Protection Committee and descriptions of special measuring

devices.

Introduction

The International Maritime Organization (IMO) works on preventing air

pollutions from ships and has been doing it for over 30 years. [3] Depending on

the location there are today different kinds of certificates and standards that

companies are aiming for. These certificates and standards have different

criteria that the engines have to fulfil. In order to check these criteria, test runs

including different measurements are organized. Calibrations are a critical step

of the measurements, since wrongly calibrated instruments will give false

results. Therefore the calibrations must be done correctly and by professionals.

The employees performing the calibration do not need to have a certificate

according to the “Revised Marpol Annex VI, Regulations for the prevention of air

pollution from ships and Technical Code” written by IMO. The employees

are though skilled since the manufacturer provides internal training.

General information of calibration

Decisions made in technical contexts are often based on some measurements,

therefore it is important to be able to show that the measurements are

trustworthy. Without correct measurements, which mean traceable calibrations

with a presented uncertainty, the company risks lower quality, loosing

competitiveness and in the end poor profitability. [4] The definition of

calibration is “the act of checking or adjusting (by comparison with a standard)

the accuracy of measuring instrument”. [6] Calibration is therefore a comparison

between measurements. In calibration for an instrument measuring gas

composition the standard is a specific gas. The composition of the standard gas is

known and will be compared with the measured gas.

3

Calibration of instruments

Every instrument that is used for measuring an engine’s parameters must be

calibrated accordingly to the requirements of the technical code, published

by the international maritime organization. [3] The calibration validity period

varies among the different measurement instruments. The validity period can for

example be between three to twelve months; as for an engine speed

measurement instrument the valid period is three months when it is six months

for a measurement instrument for exhaust gas flow. The calibration validity

period also differs depending on if the measurements are made before achieving

a certificate or if the measurements are made when the engine already is pre-

certified. [3] A pre-certified engine means that the engine already has been

tested and received a certificate for one configuration. The configuration of the

engine can change after this. The new test with the pre-certified engine will often

be done on board of the ship. [3] The certificate type is an “Engine International

Air Pollution Prevention” (EIAPP) certificate, and will be approved by the flag

state marine authority (flag state; “the state under whose laws the vessel is

registered or licensed”)[9]. The requirements of the EIAAP certificate varies on

the location, examples of areas where the requirements are stricter are Baltic Sea

and North Sea. [7] The validity periods between the calibrations will be

presented in the tables below. One calibration can last up to two or three hours.

[5]

It must be possible to track the data from the calibration of the measuring

instruments to standards that are accepted by the administration. A proposal

must be submitted when the calibration procedure or period differs from those

given in the technical code. The proposal must also be submitted and approved

by the administration before the test. [3]

4

NO. Measurement

instrument

Permissible deviation Calibration

validity period

(months)

1 Engine speed ±2% of reading or ±1%

of engine’s maximum

value, whichever is

larger

3

2 Torque ±2% of reading or ±1%

of engine’s maximum

value, whichever is

larger

3

3 Power (where measured

directly)

±2% of reading or ±1%

of engine’s maximum

value, whichever is

larger

3

4 Fuel consumption ±2% of engine’s

maximum value

6

5 Air consumption ±2% of reading or ±1%

of engine’s maximum

value, whichever is

larger

6

6 Exhaust gas flow ±2,5% of reading or

±1,5% of engine’s

maximum value,

whichever is larger

6

“Permissible deviations and calibration validity periods of instruments for

engine-related parameters for measurements on a test bed” [3]

5

NO. Measurement

instrument

Permissible deviation Calibration

validity period

(months)

1 Engine speed ±2% of engine’s

maximum value

12

2 Torque ±5% of engine’s

maximum value

12

3 Power (where measured

directly)

±5% of engine’s

maximum value

12

4 Fuel consumption ±4% of engine’s

maximum value

12

5 Air consumption ±5% of engine’s

maximum value

12

6 Exhaust gas flow ±5% of engine’s

maximum value

12

“Permissible deviations and calibration validity periods of instruments for

engine-related parameters for measurements on board a ship when the engine is

already pre-certified” [3]

6

Gases used in calibration

When using calibration gases and span and zero check gases it is important to

take into account the shelf life of the gases. The person doing the calibration

must document the expiration date of the gases. The manufacturer has defined

the expiration date. [3]

Pure gases, including zero check gases

Pure gases can be used as zero check gases. The zero check gas is used for setting

the lower end of the range. “The calibration range is defined as the region

between the limits within which a quantity is measured, received or transmitted,

expressed by stating the lower and upper range values.” [2]

Gases that should be obtainable are purified nitrogen, purified oxygen and

hydrogen-helium mixture. In the table below the required contamination limits

for these gases will be given. [3]

Pure gas (zero

check gas)

Contamination limits/purity %

Purified nitrogen

Contamination ≤ 1 ppmC,

≤ 1 ppm CO,

≤ 400 ppm ,

≤ 0.1 ppm NO

Purified oxygen Purity > 99.5% volume

Hydrogen-helium

mixture

40 ± 2% , balance He

Contamination ≤ 1 ppmC,

≤ 400 ppm

Purified synthetic

air

Contamination ≤ 1 ppmC,

≤ 1 ppm CO,

≤ 400 ppm ,

≤ 0.1 ppm NO

Oxygen content 18% - 21% volume

[3]

7

Calibration and span gases

The span gases are used for setting up the top end of the calibration range.

Mixtures of gases that should be obtainable are:

- CO and purified nitrogen

- and purified nitrogen ( should not be more than 5% of the NO

content)

- and purified nitrogen

- and purified nitrogen

- and purified synthetic air, or and purified synthetic air. [3]

In addition to these mixtures other gas mixtures can also be used. The only

requirement in that case is that the gases do not react with each other. The

concentration of calibration and span gases should be specified in volume per

cent or volume ppm. The concentration must be comparable with national or

international gas standards. Furthermore, the real concentration of the

calibration must not vary more than 2% compared with the nominal value. This

means that the primary gases have to be known to an accurate rate of ±1%. In

order to obtain the correct concentration of the calibration gases, purified or

purified synthetic air can be used to dilute the gases. The dilution process will be

done by using precision blending devices and for each calibration done using a

blending device, the verification must be made between 15 and 50 % of full scale.

An alternative way of testing the blending device is using an instrument that is

linear by nature. Examples of this kind of instruments are instruments using NO

gas with a Chemiluminescence Detector (CLD). [3]

It is essential that the span gases are directly connected to the instruments when

putting up the span values for the instrument. The blending devices must be

checked at the used settings, so if the settings are being changed the device

should be checked again. The measured concentration of the device must also be

compared to the nominal value. Additionally the difference in each point of he

measurement must not be more or less than 1% of the nominal value. A gas

analyser cannot be linearized with the same gas divider twice. [3]

8

Gases that are used to check the interference of oxygen contain propane or

methane. The amount of hydrocarbons in these gasses should be 350 ppmC ± 75

ppmC. The concentration can for example be checked by chromatographic

analysis of total hydrocarbons and impurities. The dominant diluent should be

nitrogen and the rest will consist of oxygen. [3]

A system leakage test should always be done during a test run. That can be done

with a flow meter or with zero and span gases. In the leakage test done with zero

and span gases concentrations will be compared. At the beginning of the

sampling line there will be a concentration step change when zero gas will be

changed to span gas. After a while the current concentration will be compared to

the concentration at the beginning. If the concentration now is lower than the

concentration at the beginning it means that there is a leakage or calibration

problem. [3]

Emission measurement instruments

Horiba PG-250

Horiba PG-250 is a portable instrument used for measuring , NO, and

. The measurement methods used are for example chemiluminescence for

measuring and a galvanic cell or an optional zirconium oxide sensor for

measuring . [8]

The Horiba PG-250 meets the ISO 8178 standard, which is “an international

standard designed for a number of non-road engine applications.” [1] The ISO

8178 is used in many countries in the European Union, USA and Japan “for

emission certification and/or type approval.” [1]. Horiba PG-250 meets also the

IMO code measurement standards. [5] FINAS Accredited Laboratory, which

follows the EN ISO/IEC 17025 standard guarantee the quality of the Horiba PG-

250.

9

Horiba PG-250. [5]

Horiba EXSA-240CL

Horiba EXSA-240CL is a portable emission measurement system of , NO and

. As the Horiba PG-250 this instrument also meets the ISO 8178 and IMO

code measurement standards. The quality of this device is also guaranteed by

FINAS. The Horiba EXSA-240CL measures with a chemiluminescent

detector and an electro-chemical sensor measures . Both and are

measured on a wet basis. [5]

Horiba EXSA-240CL

10

For all these measurement instruments the calibration requirements set by IMO

are valid. The calibration must in other words be done according to these

requirements and be done by a certified organization.

11

References

[1] DieselNet; Emission Test Cycles ISO 8178,

http://www.dieselnet.com/standards/cycles/iso8178.php, (26.5.2013)

[2] Calibration Principles,

http://www.isa.org/Template.cfm?Section=Find_Books1&template=Ecommerce

/FileDisplay.cfm&ProductID=7577&file=ACFBA59.pdf, (26.5.2013)

[3] International Maritime Organization (2009); Revised Marpol Annex VI,

Regulations for the prevention of air pollution from ships and Technical Code

2008, (26.5.2013)

[4] Swedac; Kalibrering, http://www.swedac.se/sv/Omraden/Kalibrering/,

(20.5.2013)

[5] T. Sundell 19.1.2011; WFI Technical service emission measurement systems,

(21.5.2013)

[6] The free dictionary by farlex, http://www.thefreedictionary.com, (20.5.2013)

[7] DieselNet; Emission standard, International IMO Marine Engine Regulations;

http://www.dieselnet.com/standards/inter/imo.php (30.5.2013)

[8] Horiba Process & Environmental Automotive Test Systems; PG-250 Portable

Multi-Gas Analyzer

http://www.horiba.com/process-

environmental/products/combustion/details/pg-250-portable-multi-gas-

analyzer-264/ (30.5.2013)

[9] Wikipedia; Flag state, https://en.wikipedia.org/wiki/Flag_state (30.5.2013)