ISO 4376

Cycle energy requirement — Test method

This International Standard applies to positive displacement compressors as covered by ISO 1217, low pressure compressors as covered by NP 22484 and centrifugal compressors as covered by ISO 18740. This International Standard defines and describes the acceptance test for Cycle Energy Requirement of a compressor. It specifies the operating and testing conditions which apply when a full test is specified. Cycle Energy Requirement is the additional energy required for a single cycle caused by transient conditions.

Exigence d'énergie de cycle — Essais de réception

General Information

• Status: Not Published
• ICS: 23.140 - Compressors and pneumatic machines
• Technical Committee: ISO/TC 118/SC 6 - Air compressors and compressed air systems
• Drafting Committee: ISO/TC 118/SC 6 - Air compressors and compressed air systems
• Current Stage: 6000 - International Standard under publication
• Completion Date: 15-Oct-2024

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 4376
ISO/TC 118/SC 6
Cycle energy requirement — Test
Secretariat: SIS
method
Voting begins on:
Exigence d'énergie de cycle — Essais de réception 2024-08-19
Voting terminates on:
2024-10-14
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 4376:2024(en) © ISO 2024

FINAL DRAFT
ISO/FDIS 4376:2024(en)
International
Standard
ISO/FDIS 4376
ISO/TC 118/SC 6
Cycle energy requirement —
Secretariat: SIS
Test method
Voting begins on:
Exigence d'énergie de cycle — Essais de réception
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 4376:2024(en) © ISO 2024

ii
ISO/FDIS 4376:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviations and subscripts . . 3
4.1 Symbols and abbreviations .3
4.2 Subscripts . .3
5 Measuring equipment, methods and accuracy . 3
5.1 General .3
5.2 Measurement of pressure and temperature .4
5.3 Measurement of compressor package actual flow rate.4
5.4 Measurement of compressor package power input .4
5.5 Measurement logging frequency .4
5.6 Throttle valve .4
5.7 Non-return valve .4
6 Test procedure . 4
6.1 CER test conditions and limitations .5
6.2 Cycle energy requirement test method .6
6.2.1 (Optional) Full load actual volume flow and package power input .6
6.2.2 Minimum actual volume flow and package power input .6
6.2.3 Idle power .6
6.2.4 Logging data .6
6.2.5 Cycling modes and determination of cycle.6
6.3 Calculation of cycle energy requirement .8
6.4 Test report .9
Annex A (informative) Cycle energy requirement — Simplified estimation.10
Annex B (informative) Cycle energy requirement — Compressor control strategies .11
Bibliography .23

iii
ISO/FDIS 4376:2024(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 118, Compressors and pneumatic tools,
machines and equipment, Subcommittee SC 6, Air compressors and compressed air systems.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 4376:2024(en)
Introduction
This document was developed to provide guidance to determine the cycle energy requirement for all types
of compressors. The types of compressors included in the consideration include dynamic and positive
displacement designs. Applicable pressures include low pressure (e.g. blowers), typical air network
pressures in industry and higher pressures needed for special application. Applications covered include but
are not limited to standard industrial air production and gas compression for industrial and other purposes.
Compressors are used in almost all types of industries and in processes such as energy production and water
treatment. In most industrial facilities, small and large, compressed air is an expected utility. In industry
and elsewhere many processes demand gases to be compressed to certain pressures.
Compressing a gas is energy intensive and growing attention to the environmental impact has encouraged
manufacturers of compressors to continuously raise the energy efficiency of its products.
The need for compressed gas usually varies with time. While some types of compressor can adapt to changes
of demand by delivering variable amounts of gas all compressors will at some point change from gas delivery
to no delivery and back. Such a no delivery mode, called idle mode, usually means the compressor is left
running being ready to resume delivery on short notice while still consuming energy.
Until now performance data is typically given and evaluated for a steady state design point. It is also
customary to provide data for the idle mode when the delivered amount of gas is zero. What is not provided at
present time is the energy consumed in switching from idle mode to delivery and vice versa. Taken together
the energy required for these two events combined can be referred to as the cycle energy requirement (CER).

v
FINAL DRAFT International Standard ISO/FDIS 4376:2024(en)
Cycle energy requirement — Test method
1 Scope
This document applies to electrically driven positive displacement and dynamic compressors.
This document defines and describes the test method to evaluate the cycle energy requirement.
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 5167-1, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section
conduits running full — Part 1: General principles and requirements
ISO 9300, Measurement of gas flow by means of critical flow nozzles
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
standard inlet point
location at which gas enters the compressor package
3.2
standard discharge point
discharge point for a packaged compressor is the terminal outlet
3.3
inlet pressure
absolute pressure of the gas at the standard inlet point (3.1)
3.4
inlet temperature
total temperature at the standard inlet point (3.1) of the compressor
3.5
compressor package
compressor unit with prime mover, transmission, fully piped and wired and generally includes all ancillary
items necessary for effective operation
3.6
compressor package power input
sum of the electrical power inputs to the prime mover and all other ancillary and auxiliary items included in
the compressor package (3.5)
ISO/FDIS 4376:2024(en)
3.7
compressor package actual volume flow rate
actual volume flow rate of gas, compressed and delivered at the standard discharge point (3.2), referred to
conditions of total temperature, total pressure and composition prevailing at the st
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ISO /TC 118/SC 06 6
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Secretariat: SIS
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Cycle energy requirement – — Test method
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Exigence d'énergie de cycle — Essais de réception
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ISO/FDIS 4376:2024(Een) Formatted: Font: 11 pt
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spacing: single
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
Header distance from edge: 1.27 cm, Footer distance
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
from edge: 0.5 cm
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester. Commented [eXtyles1]: The reference "ISO 2024" is to a
withdrawn standard
ISO copyright office
Formatted: Default Paragraph Font
CP 401 • Ch. de Blandonnet 8
Formatted: Default Paragraph Font
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: Adjust space between Latin and Asian text,
EmailE-mail: [e-mail]
Adjust space between Asian text and numbers
Website: www.iso.orgwww.iso.org
Formatted: French (France)
Published in Switzerland Formatted: French (France)
Formatted: French (France)
Formatted: FooterPageRomanNumber
ii © ISO 2024 – All rights reserved
ii
ISO/FDIS 4376:2024(en)
Formatted: Font: 11 pt, Font color: Auto
Formatted: Font: 11 pt
Formatted: HeaderCentered, Left, Space After: 0 pt,
Contents
Line spacing: single
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviations and subscripts . 3
4.1 Symbols and abbreviations . 3
4.2 Subscripts . 3
5 Measuring equipment, methods and accuracy . 4
5.1 General. 4
5.2 Measurement of pressure and temperature . 4
5.3 Measurement of compressor package actual flow rate . 4
5.4 Measurement of compressor package power input . 4
5.5 Measurement logging frequency . 5
5.6 Throttle valve . 5
5.7 Non-return valve . 5
6 Test procedure . 5
6.1 CER test conditions and limitations . 6
6.2 Cycle energy requirement test method . 6
6.2.1 (Optional) Full load actual volume flow and package power input . 7
6.2.2 Minimum actual volume flow and package power input . 7
6.2.3 Idle power . 7
6.2.4 Logging data . 7
6.2.5 Cycling modes and determination of cycle . 7
6.3 Calculation of cycle energy requirement . 9
6.4 Test report . 10
Annex A (informative) Cycle energy requirement — Simplified estimation. 11
Annex B (informative) Cycle energy requirement — Compressor control strategies . 12

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Formatted: Font: 10 pt
4 Symbols and subscripts . 3
4.1 Symbols . 3
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5 Measuring equipment, methods, and accuracy . 3
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5.1 General. 3
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5.2 Measurement of pressure and temperature . 3
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5.3 Measurement of flow rate . 4
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5.4 Measurement of compressor package power input . 4
5.5 Measurement logging frequency . 4
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© ISO 2024 – All rights reserved
iii
ISO/FDIS 4376:2024(Een) Formatted: Font: 11 pt
Formatted: Font: 11 pt
Formatted: HeaderCentered, Space After: 0 pt, Line
5.6 Throttle Valve. 4
spacing: single
5.7 Non-Return Valve . 4
6 Test Procedure . 4
6.1 CER test conditions and limitations . 5
6.2 Cycle Energy Requirement Test method . 5
6.2.1 (Optional) Full load Actual Volume Flow and Package Power Input . 6
6.2.2 Minimum Actual Volume Flow and Package Power Input . 6
6.2.3 Idle Power . 6
6.2.4 Logging data . 6
6.2.5 Cycling modes and determination of cycle . 6
6.3 Calculation of Cycle Energy requirement . 8
6.4 Test Report . 8
Annex A (informative) Cycle Energy Requirement – Simplified estimation. 10
Annex B (informative) Cycle Energy Requirement – Compressor Control Strategies . 11
Bibliography . 22
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iv © ISO 2024 – All rights reserved
iv
ISO/FDIS 4376:2024(en)
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Formatted: Font: 11 pt
Formatted: HeaderCentered, Left, Space After: 0 pt,
Foreword
Line spacing: single
Formatted: Adjust space between Latin and Asian text,
ISO (the International Organization for Standardization) is a worldwide federation of national standards
Adjust space between Asian text and numbers
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 document 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).
Formatted: English (United Kingdom)
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 118, Compressors and pneumatic tools, machines
and equipment, Subcommittee SC 6, Air compressors and compressed air systems.
Any feedback or questions on this document should be directed to the user’s national standards body.
...