ISO 18888:2017
(Main)Gas turbine combined cycle power plants — Thermal performance tests
Gas turbine combined cycle power plants — Thermal performance tests
ISO 18888:2017 specifies standard rules for preparing, conducting, evaluating and reporting thermal performance tests on combined cycle and cogeneration power plants driven by gas turbines for base and part load operation with or without supplementary firing. ISO 18888:2017 is applicable to - thermal performance tests for general information, - thermal acceptance tests for determining the performance of the combined cycle plant in relation to a contractual guarantee, and - comparative tests designed to check the performance differentials of the combined cycle and cogeneration power plants, for testing before and after modifications, upgrades or overhauls. It can be used to determine the following thermal performance test goals and expected values, under specific operating and reference conditions within defined test boundaries: - electrical power output; - heat rate or thermal efficiency; - process steam and/or district heat w/o generation of electrical power output by means of a steam turbine. ISO 18888:2017 does not apply to individual equipment component testing, which is covered by corresponding standards. It is not intended to be applied to the following test goals: - environmental testing for example emissions, noise; - vibration testing; - operational testing; - absolute or comparative performance of specific components of the combined cycle covered by dedicated standards (e.g. gas turbines).
Turbines à gaz — Centrales à cycle combiné — Essais de performance thermique
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18888
First edition
2017-10
Gas turbine combined cycle power
plants — Thermal performance tests
Turbines à gaz — Centrales à cycle combiné — Essais de performance
thermique
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and units . 6
5 Test boundary . 7
6 Preparation for test .11
6.1 General .11
6.2 Performance degradation .12
6.3 Measurement classification .12
6.4 Design and construction phase recommendations .12
6.5 Test procedure .13
6.6 Field preparations for the performance test .14
6.7 Instruments and measuring methods .16
6.7.1 General.16
6.7.2 Electrical power measurement .16
6.7.3 Flow measurements . .17
6.7.4 Temperature measurements .18
6.7.5 Relative humidity measurements .22
6.7.6 Pressure measurements .23
6.7.7 Data acquisition system .25
6.7.8 Wind velocity .25
6.7.9 Storage vessel levels .25
6.7.10 Data sampling .26
6.8 Determination of fuel properties .26
6.8.1 General.26
6.8.2 Tests on fuel gas .27
6.8.3 Tests on liquid fuel .27
6.9 Determination of cooling water flow into the condenser .28
6.9.1 General.28
6.9.2 Energy balance method .28
6.9.3 Cooling water pump performance curves .31
6.9.4 Direct flow measurement .32
6.10 Measurement uncertainties .32
6.11 Maximum allowable uncertainties .34
6.12 Calibration .35
7 Execution of test .36
7.1 Base reference conditions .36
7.1.1 General.36
7.1.2 Specified gaseous fuel.37
7.1.3 Specified liquid fuel .37
7.2 Preliminary test .38
7.3 Performance test .38
7.4 Duration of test runs .39
7.5 Auxiliary equipment operation.39
7.6 Tests with inlet air heating system .39
7.7 Tests with inlet air cooling system . .40
7.8 Maximum permissible variation in operation conditions .40
8 Calculation of results for absolute test .41
8.1 General .41
8.2 Correction to base reference conditions .41
8.2.1 General.41
8.2.2 Correction curves based correction approach .42
8.2.3 Thermodynamic heat balance model based correction approach.43
8.2.4 Boundary parameters for correction .44
8.2.5 Description of corrections to base reference conditions .46
8.3 Power output for combined cycle overall test .50
8.3.1 Measured power output .50
8.3.2 Power output corrected to nominal power factor .52
8.3.3 Corrected power output .52
8.4 Heat rate for combined cycle overall test .53
8.4.1 Measured heat rate/measured thermal efficiency .53
8.4.2 Corrected heat rate / corrected thermal efficiency .53
8.5 Power output of steam turbine determination for combined cycle in single
shaft configuration.54
9 Part load tests .54
9.1 General .54
9.2 Test set up and conduct .55
9.3 Correction method for part loads .57
10 Calculation of results for comparative test .57
10.1 General .57
10.2 Comparative performance test uncertainty .57
10.3 Preparation for comparative test .58
10.3.1 Instrumentation .58
10.3.2 Preliminary activities and plant settings .58
10.4 Execution of comparative tests and calculation of results .59
11 Test report .59
11.1 Form of the report .59
11.2 Detailed report .60
Annex A (informative) Typical secondary variables .61
Annex B (informative) Numerical examples of uncertainty calculation .64
Annex C (informative) Procedure for power factor conversion .69
Bibliography .73
iv © ISO 2017 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 192, Gas turbines.
Introduction
This document specifies standard rules for preparing, conducting, evaluating and reporting thermal
performance tests in order to determine and/or verify the power output, the thermal efficiency (heat
rate) and/or other performance test parameters for gas turbine driven combined cycle power plants.
It provides information on methods of measurement considering uncertainties and on methods
for corrected results obtained under test conditions in order to compare to guaranteed or specified
conditions.
The objective of testing conducted per this document is to determine combined cycle thermal
performance characteristics in accordance with any previously drawn up agreements such as the
purchase agreements, test criteria documents, engineering, procurement and construction (EPC)
requirements, power purchase agreements, power and water purchase agreements, contractual
services agreements.
The document also provides guidelines for comparative tests designed to check performance
differentials of the combined cycle and cogeneration power plants, for testing before and after
modifications, upgrades or overhauls. Improvements to achieve additional performance of the combined
cycle may include modification/substitutions of main components and additions of components inside
test boundary. This comparative testing philosophy may also be used for “periodic testing” of the
plant in order to monitor overall plant performance degradation, while giving due consideration to the
relative testing uncertainty.
vi © ISO 2017 – All rights reserved
INTERNATIONAL STANDARD ISO 18888:2017(E)
Gas turbine combined cycle power plants — Thermal
performance tests
1 Scope
This document specifies standard rules for preparing, conducting, evaluating and reporting thermal
performance tests on combined cycle and cogeneration power plants driven by gas turbines for base
and part load operation with or without supplementary firing.
This document is applicable to
— thermal performance tests for general information,
— thermal acceptance tests for determining the performance of the combined cycle plant in relation to
a contractual guarantee, and
— comparative tests designed to check the performance differentials of the combined cycle and
cogeneration power plants, for testing before and after modifications, upgrades or overhauls.
It can be used to determine the following thermal performance test goals and expected values, under
specific operating and reference conditions within defined test boundaries:
— electrical power output;
— heat rate or thermal efficiency;
— process steam and/or district heat w/o generation of electrical power output by means of a steam
turbine.
This document does not apply to individual equipment component testing, which is covered by
corresponding standards.
It is not intended to be applied to the following test goals:
— environmental testing for example emissions, noise;
— vibration testing;
— operational testing;
— absolute or comparative performance of specific components of the combined cycle covered by
dedicated standards (e.g. gas turbines).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2314:2009, Gas turbines — Acceptance tests
ISO 3675, Crude petroleum and liquid petroleum products — Laboratory determination of density —
Hydrometer method
ISO 5167 (all parts), Measurement of fluid flow by means of pressure differential devices inserted in circular
cross-section conduits running in full
ISO 6974-1, Natural gas — Determination of composition and associated uncertainty by gas
chromatography — Part 1: General guidelines and calculation of composition
ISO 6975, Natural gas — Extended analysis — Gas-chromatographic method
ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from
composition
ISO 9951, Measurement of gas flow in closed conduits — Turbine meters
ISO 10715:1997, Natural gas — Sampling guidelines
ISO 10790, Measurement of fluid flow in closed conduits — Guidance to the selection, installation and use of
Coriolis flowmeters (mass flow, density and volume flow measurements)
ISO 12185, Crude petroleum and petroleum products — Determination of density — Oscillating U-tube
method
ISO 12213-2, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-
composition analysis
ISO 17089-1, Measurement of fluid flow in closed conduits — Ultrasonic meters for gas — Part 1: Meters for
custody transfer and allocation measurement
ISO 20765-1, Natural gas — Calculation of thermodynamic properties — Part 1: Gas phase properties for
transmission and distribution applications
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ASTM D1945, Standard Test Method for Analysis of Natural Gas by Gas Chromatography
ASTM D4052, Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital
Density Meter
ASTM D4809, Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb
Calorimeter
ASTM D4868, Standard Test Method for Estimation of Net and Gross Heat of Combustion of Burner and
Diesel Fuels
DIN 51900-1, Testing of solid and liquid fuels — Determination of gross calorific value by the bomb
calorimeter and calculation of net calorific value — Part 1: Principles, apparatus, methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
absolute test
test carried out in order to prove an absolute guarantee or an absolute expected performance
3.2
comparative test
test carried out in order to prove a relative change or improvement of performance
EXAMPLE For retrofits.
2 © ISO 2017 – All rights reserved
3.3
performance test
means test of performance of power output, efficiency or heat rate, heat duty, process steam mass flows,
etc., as specified
EXAMPLE Performance tests could be specified in contractual agreements.
3.4
preliminary test
test or tests in advance of the actual performance test (3.3) to check the complete measuring system
and main components to verify that the power plant is in a suitable condition before conducting the
actual performance test
3.5
simple cycle
thermodynamic cycle consisting only of successive compression, combustion and expansion
Note 1 to entry: Generation of electrical power (3.16) output driven only from a gas turbine (3.29) or from the
gas turbine in combined cycle (3.28) using a bypass stack. The working fluid enters the gas turbine from the
atmosphere and is discharged into the atmosphere.
[SOURCE: ISO 11086:1996, 1.8, modified.]
3.6
open cycle
combined cycle (3.28) with the steam turbine bypassed in which the working fluid enters the gas
turbine from the atmosphere and is discharged through a heat recovery steam generator stack into the
atmosphere
Note 1 to entry: The generation of electrical power output in a combined cycle (3.28) plant operating in open cycle
is provided only from the gas turbine, as the steam turbine is bypassed.
3.7
test boundary
imaginary boundary drawn encompassing the major equipment included in the test scope
3.8
heat duty
thermal net/gross output produced from the combined cycle (3.28) plant
3.9
heat rate
HR
ratio of the fuel energy supplied per unit time to the electrical power produced
Note 1 to entry: Inverse of thermal efficiency.
Note 2 to entry: The heat rate is expressed in units of kilojoules per kilowatt hour.
[SOURCE: ISO 11086:1996, 5.31, modified.]
3.10
heating value
calorific value
specific energy
amount of heat released by the complete combustion in air of a specific quantity of gas or liquid fuel
when the reaction takes place at constant pressure
Note 1 to entry: If the combustion products accounted for are only in the gaseous state, the value is called lower
heating value (LHV) or inferior calorific value or net heating value. If the combustion products are gaseous with
the exception of water, which is in liquid state, the value is called higher heating value (HHV) or superior calorific
value or gross heating value at 15 °C for natural gas fuel.
Note 2 to entry: HHV at constant volume and a reference temperature of 15 °C shall be determined by means of a
bomb calorimeter method. Then LHV at constant volume is found by calculation deducting the latent heat of the
calculated amount of water vapour produced from the measured hydrogen content of the fuel.
3.11
high pressure
HP
highest pressure level of the working fluid
3.12
intermediate pressure
IP
medium pressure level of the working fluid
3.13
low pressure
LP
lowest pressure level of the working fluid
3.14
mechanical loss
reduction of power output due to bearing and windage losses of gas and steam turbine rotors
[SOURCE: ISO 11086:1996 5.34, modified.]
3.15
hot water
host that can accept or supply energy (non-fuel) to a cycle
3.16
power
quantity expressed in terms of mechanical shaft power at the turbine coupling or electrical power of
the turbine-generator
3.17
primary variable
value that is measured and used for calculation and correction of test results
3.18
process steam
host that can accept or supply energy (non-fuel) to the cycle
EXAMPLE District heating, steam consumers (refinery, pulp and paper industries, petrochemical industries),
steam producers (auxiliary boilers, steam from other power plant blocks), etc.
3.19
secondary variable
value that is measured but that will not be used for calculation of the results
Note 1 to entry: These variables are measured to ensure that the required test conditions are not violated and to
provide information for future use.
3.20
standard reference condition
condition for the ambient air or intake air at the compressor flange (alternatively, the compressor
intake flare) equal to
— absolute pressure of 101,325 kPa (1,01325 bar; 760 mmHg),
— temperature of 15 °C, and
— relative humidity of 60 %
4 © ISO 2017 – All rights reserved
Note 1 to entry: The conditions are defined in ISO 2533.
Note 2 to entry: In the case of the closed cycle, the standard conditions for the air heater are 15 °C and 101,325 kPa
for the ambient atmospheric air.
Note 3 to entry: An inlet water temperature of 15 °C applies if cooling of the working fluid is used.
Note 4 to entry: These reference conditions may be different if otherwise agreed in contractual documents or
agreements.
3.21
thermal efficiency
ratio of electrical power (3.16) output to the heat consumption
Note 1 to entry: Inverse of heat rate.
Note 2 to entry: It can be based on lower or higher heating value.
[SOURCE: ISO 3977-1:1997, 2.3.4, modified.]
3.22
total efficiency
ratio of the sum of electrical power (3.16) output and thermal output (3.23) to the heat consumption
3.23
thermal output
energy as process steam (3.18), hot water (3.15)or other export of thermal energy from the cycle
3.24
thermal performance guarantee
guaranteed value for net/gross power (3.16) output, net/gross heat rate (3.9), or net/gross thermal
efficiency (3.21), process steam (3.18) mass flows and/or heat duty (3.8)
3.25
tolerance
allowed deviation from a specific requirement
Note 1 to entry: To define in contractual agreements.
3.26
uncertainty
parameter associated with the result of a measurement, which characterises the dispersion of the
values that can reasonably be attributed to the measurand
Note 1 to entry: The determination of the quality of a measurement that can be expressed with the uncertainty
of the test result is of fundamental importance in any field of measuring and testing. A measure to quantify
such quality is the uncertainty of measurement. The shortened term “uncertainty” is used for simplicity in this
document.
Note 2 to entry: The expression “accuracy of measurement” (closeness of the agreement between the result of
a measurement and the value of the measurand), commonly abbreviated as “accuracy,” is not associated with
numbers and is not used as a quantitative term.
3.27
cogeneration power plant
gas turbine based power plant which delivers both electricity and heat
Note 1 to entry: Heat can be delivered in form of process steam or hot water/district heat water to one or more
external consumers. The plant can include a steam turbine, but can also deliver the steam or hot water produced
in the heat recovery steam generator or waste heat recovery unit direct to the external consumer.
3.28
combined cycle
CC
thermodynamic cycle employing the combination of a gas turbine cycle with a steam or other fluid
Rankine cycle
[SOURCE: ISO 11086:1996, 1.12]
3.29
gas turbine
GT
rotary engine that converts fuel thermal energy into mechanical work
Note 1 to entry: It consists of one or several rotating compressors, a thermal device(s) that heats the working
fluid, one or several turbines, a control system and essential auxiliary equipment. Any heat exchangers (excluding
waste exhaust heat recovery exchangers) in the main working fluid circuit are considered to be part of the gas
turbine.
[SOURCE: ISO 3977-1:1997, 2.1, modified.]
3.30
heat recovery steam generator
HRSG
energy recovery heat exchanger that produces process steam (3.18) and/or drives a steam turbine
Note 1 to entry: It may contain provisions for supplementary firing.
3.31
multi-shaft combined cycle
combined cycle (3.28) in which the useful power output from the cycle is taken from more than one shaft
[SOURCE: ISO 11086:1996, 26.7, modified.]
3.32
single shaft combined cycle
combined cycle (3.28) in which the useful power (3.16) output from the cycle is taken from one shaft
[SOURCE: ISO 11086:1996, 26.6]
3.33
steam turbine
ST
rotary engine in which the kinetic energy of a moving fluid (steam) is converted into mechanical energy
by causing a bladed rotor to rotate
3.34
waste heat recovery unit
WHRU
heat exchanger to deliver hot fluid (not gas) where there is no change of phase to the working fluid,
which is commonly a water/glycol blend
4 Symbols and units
For the purposes of this document, the symbols and units shown in Table 1 apply.
6 © ISO 2017 – All rights reserved
Table 1 — Global symbols
Symbol Definition SI unit
AC Additive correction (i) for measured power output kW
Pi
AC Additive correction (i) for measured fuel heat input kW
Qi
BRC Base reference conditions (guarantee conditions) –
C Global correction for power output –
P
C Global correction for fuel heat consumption –
Q
Net or gross heat rate of the combined cycle based on fuel lower or higher heating
HR kJ/kWh
corr
value and corrected to base reference conditions
Heat rate of the combined cycle based on measured electrical power output and
HR kJ/kWh
elec, meas
measured fuel lower or higher heating value
Heat rate of the combined cycle based on measured electrical power output,
HR kJ/kWh
total, meas
measured thermal output and measured fuel lower or higher heating
Specific enthalpy of fuel at temperature entering in the heat source kJ/kg
h
f
Specific enthalpy of fuel at standard reference conditions 15 °C / 1,01325 bar kJ/kg
h
Cooling water mass flow kg/s
m
CW
Fuel mass flow kg/s
m
fuel
m Process steam or hot water mass flow kg/s
process
MC Multiplicative correction (i) for measured power output –
Pi
MC Multiplicative correction (i) for measured fuel heat input –
Qi
P Gross or net power output of the combined cycle kW
CC
P Gross or net power output corrected to base reference conditions kW
corr
P Measured gross power output kW
gross,meas
P Measured net power output kW
net,meas
PF Power factor –
P Gas turbine power output kW
GT
P Part load power output of combined cycle kW
PL
P Part load power output of gas turbine kW
PL,GT
P Steam turbine power output kW
ST
Q Corrected heat input of the combined cycle kW
CC
Q Measured heat input kJ/s
meas
Net or gross thermal efficiency of the combined cycle based on fuel lower or higher
η %
corr
heating value and corrected to base reference conditions
Thermal electrical efficiency of the combined cycle based on measured electrical
η %
elec,meas
power output and measured fuel lower or higher heating value
Thermal total efficiency of the combined cycle based on measured electrical power
η %
total,meas
output, measured thermal output and measured fuel lower or higher heating value
5 Test boundary
The concept of a test boundary identifies the scope of hardware within the combined cycle power plant
subject to thermal performance testing while considering the reference conditions used to establish
the performance parameters (i.e. heat/power output, efficiency or heat rate). It provides the basis for
the definition and layout of instrumentation required to determine the energy streams crossing the
test boundary. It also determines the actual conditions during testing for correcting the test results to
reference conditions.
A combined cycle power plant can have a range of equipment within the plant boundary. Depending on
the scope of supply, and the understanding between parties, either the entire plant or only a portion
of the plant including gas turbine(s) within the test boundary can be tested. This document provides
flexibility in terms of the test boundary, and hence, the test boundary is typically defined along with the
base reference conditions that are used to specify the performance parameters.
Figures (1) to (7) provide a range of applicable test boundaries. The users of this document should
recognize that the test boundaries provided herein are for reference only, and that the actual test
boundaries can vary depending on the plant design and the contractually guaranteed scope of supply.
Key
ACC air cooled condenser(s) GT gas turbine(s)
Aux auxiliary consumption HRSG heat recovery steam generator(s)
C Twr cooling tower(s) Process heat in form of process steam or hot water / district heat
Cond condenser(s) ST steam turbine(s)
CW Pump circulation water pump(s) WHRU waste heat recovery unit(s)
Gen generator(s)
Figure 1 — Combined cycle plant test boundary: sample 1, overall plant test boundary for multi-
shaft configuration with process steam and duct firing (e.g. turnkey project)
8 © ISO 2017 – All rights reserved
Key
See Figure 1.
Figure 2 — Combined cycle plant test boundary: sample 2, typical overall plant test boundary
with water steam cycle operated in condensing mode (e.g. turnkey project)
Key
See Figure 1.
Figure 3 — Combined cycle plant test boundary: sample 3, test boundary including gross power
output and gross efficiency (e.g. power island project)
Key
See Figure 1.
Figure 4 — Combined cycle plant test boundary: sample 4, test boundary including condenser
pressure as primary variable for gross power output and gross efficiency
Key
See Figure 1.
Figure 5 — Combined cycle plant test boundary: sample 5, Overall plant test boundary
including back pressure steam turbine(s) for generation of process steam
10 © ISO 2017 – All rights reserved
Key
See Figure 1.
Figure 6 — Combined cycle plant test boundary: sample 6, overall plant test boundary for single
shaft configuration (e.g. turnkey project)
Key
See Figure 1.
Figure 7 — Cogeneration plant test boundary: sample 7, gas turbine combined cycle plant with
waste heat recovery unit for generation of hot water or process steam
6 Preparation for test
6.1 General
Thermal performance testing requires specific and detailed preparations. Since the purpose of such
tests varies depending on the equipment, site conditions and contractual scope, it is crucial that a
dedicated test procedure document is established and agreed well in advance of the planned test date.
The procedure document should be developed in accordance with this document and approved by all
responsible parties. Sufficient time to development the final procedure should be considered to allow
the parties involved for addressing comments. A clear determination of the equipment boundaries,
associated instrumentation and correction methodology shall avoid any potential disagreements after
the test.
6.2 Performance degradation
The thermal performance degradation of combined cycle equipment during operation is an existing
phenomenon. This is associated with effects of fouling, erosion, wear and tear of gas turbine
components, as well as those of the water/steam cycle equipment.
Thermal performance tests should be carried out immediately after the completion of the
commissioning. However, agreement to apply degradation corrections to the performance test results
is strictly a commercial issue between the parties and beyond the scope of this document.
In most cases, the combined cycle thermal performance guarantees are made based on “new and clean”
equipment conditions. The contractual agreements between the parties should define the period when
the equipment is considered as new and clean and state if performance corrections are permitted, when
equipment is tested beyond this period.
The detailed methodology on how to apply degradation correction may be derived from comparative
tests or predictive degradation curves.
6.3 Measurement classification
Measurements of variables used in calculation of test results are considered primary variables. These
measurements directly relate to the boundary conditions and require instrumentation accuracy in
accordance with this document.
Measurements of variables that are not included in the calculation and correction of the results but
provide indication that the required test conditions are met will be designated as secondary variables.
Examples of these variables are gas turbine exhaust temperature or steam turbine inlet pressure and
temperature. Instruments used for secondary measurements may require field verification against
suitable calibrated instruments (i.e. loop checks using portable calibration equipment). In this case,
the recommended calibration tolerance is 0,25 % of the measurement span or 0,5 K, and the reference
device should be such that it provides an accuracy ratio greater than 4 versus a field instrument.
6.4 Design and construction phase recommendations
The following recommendations should be considered when establishing the requirements for
instrumentation accuracy, calibration, documentation and location of permanent and temporary
instrumentation to be used for any thermal performance test.
a) Suitable access and isolation capability for permanently installed instrumentation and temporary
test provisions, such as fuel sampling tapping point and fuel flow measurement should be taken
into account in the design, as this will reduce manpower and downtime required during the
preparations for testing.
b) If permanently installed instrumentation is to be used during the test, the requirements of Table 4
should be implemented if possible during early stages of the design. The ability to conduct post-
test calibrations or to substitute with temporary instrumentation should also be considered. The
signal processing and data logging should also meet the requirements of this document. If the
permanently installed instrumentation has a local readout, then the display shall be in such a
position that reading the display is convenient for the reader or inspector (especially flow devices).
This is also applicable for the attached name plate identifications.
c) In the case of precision power measurement for testing, it is recommended that current and voltage
transformers in accordance with 6.7.2.3 are installed for the performance tests. The burden of
the measuring transformers should be measured and recorded to check if the load is inside the
calibration range.
d) For temporary installed instrumentation, the design should allow for connections and spools
sections, pressure connections, thermowells and electrical tie-ins. All tapping points for pressure
transmitter and differential pressure transmitter connection including required isolating valves
shall be made available for installing temporary precision test instrumentation. This also applies
12 © ISO 2017 – All rights reserved
to the provision of free thermowells and power meter connections for testing purposes. All test
instrument tapping points for connection of temporary precision test instrumentation need
to be serviceable and accessible. Where possible these should be located such that scaffolding
is not required for access. Suitable and correct isolation valves should be provided to allow safe
connection and removal of static and differential pressure transducers for the performance test.
e) Flow meters used for performance testing shall be designed, manufactured and located in a
suitable straight section with sufficient upstream and downstream lengths to ensure conformity
with the test codes. To meet the required flow meters measurement uncertainty limits, use of flow
straighteners is recommended. Flow meters should ideally be of flanged construction (if
...
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