ISO/TR 12942:2012

TECHNICAL ISO/TR
REPORT 12942
First edition
2012-09-01
Compressors — Classification —
Complementary information to ISO 5390
Compresseurs — Classification — Information complémentaire à
l'ISO 5390
Reference number
©
ISO 2012
©  ISO 2012
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ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Design classes.1
2.1 General .1
2.2 Classification by equipment type .3
2.3 Classification of compressor apparatuses by operation principles.3
2.4 Classification of compressor machines by operation principles .5
2.5 Design classes of compressor machines.6
3 Functional classes of the compressor equipment, terms and definitions.22
3.1 General .22
3.2 Basic functional classes of compressor machines.23
3.3 Formation principles of derivative functional classes for compressor machines.27
3.4 Functional classes of compressor apparatuses.32
4 Design classes of the aggregated compressor equipment, terms and definitions.34
4.1 General .34
4.2 Design classes of geared mechanical compressors.39
4.3 Design classes of driver-compressors .40
4.4 Design classes of geared driver-compressors .46
4.5 Design and service-duty classes of compressor plants .48
4.6 Design classes of packaged compressor plants .51
Annex A (informative) Design, functional and service-duty classification.54
Bibliography.59

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
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.
ISO/TR 12942 was prepared by Technical Committee ISO/TC 118, Compressors and pneumatic tools,
machines and equipment, Subcommittee SC 6, Air compressors and compressed air systems.
iv © ISO 2012 – All rights reserved

Introduction
Classification and terminology standards are fundamental to the identification of a product for using in
industrial and trade communications, education, information search, data processing, research, development,
inventing, patenting, etc. It is intended that these standards be based on the latest technical achievements
and classification theories, cover all viable modern equipment design types, exclude ambiguity, be adapted to
easy translations into different languages by exact terms, and be flexible and open to new innovations. This
Technical Report is intended to contribute essentially to obtaining these aims for a possible subsequent
revision of ISO 5390.
The main modern problems in compressor classification and terminology are associated with rapid
development and implementation of new design types. In addition, many manufacturers include in a single
non-separable compressor package, not only an aftercooler, but also a receiver, dryer, etc. In these
conditions, it is important to establish and maintain unified patterns and principles for forming new derivative
and composed terms by using a few basic original terms as well as using, as far as possible, established
professional terms which have emerged spontaneously.
The problems related to the classification of compressor equipment are complicated by the wide spectrum and
diversity of application fields, resulting in a great number of applicability and performance criteria, such as:
⎯ compression principles;
⎯ basic design features;
⎯ energy forms used (electricity, fuel heat, etc.) and driver types;
⎯ cooling agents (air, water, etc.) and methods;
⎯ lubrication conditions (oil-free or contaminated with oil);
⎯ mobility, transportability;
⎯ prefabrication level (packaged and factory-assembled compressor, compressor plant, etc.);
⎯ operation modes and service parameters;
⎯ range of functions (compression, energy conversion, cooling, drying, etc.) and appropriate structural
composition of the equipment.
Neither identification of the compressor equipment and its application fields nor selection of compressors for
specific services and comparison of their technical and economical parameters are possible without
knowledge of this information. That is why it is intended that the attributes listed in this Technical Report serve
as a basis for the practical multi-dimensional classification system of compressor equipment.
Some explanatory notes and methodical approaches are presented in Annex A.

TECHNICAL REPORT ISO/TR 12942:2012(E)

Compressors — Classification — Complementary information
to ISO 5390
1 Scope
This Technical Report gives a classification of modern compressor types and their definitions.
This Technical Report presents terms for use in technical and contractual specifications, manufacturer’s
literature, information searches and data processing systems, patent information, educational publications for
students, service and maintenance instructions, industrial statistics and market surveys, as well as in design,
quality, safety, testing and other standards, norms, regulations and codes.
It is intended that adequate technical and economical comparison and evaluation of compressor alternatives
for specific application conditions be performed with identical functional, mobility, service pressures and
service media classes, as well as with equal capacity ratings.
2 Design classes
2.1 General
The general hierarchy of compressor design classes is given in Figure 1.
Design classes specify the basic working principles and conceptual engineering philosophy of modern
compressors being operated, marketed, manufactured, developed, investigated or invented. The classification
tables in 2.2 to 2.5 contain preferred terms of basic compressor classes, their definitions and graphical
illustrations. Graphical materials are presented only as examples. Non-preferred synonyms are given in
parentheses. Special definitions are not given for those subclasses where the wording of the terms
characterizes sufficiently basic design features and attributes of the compressor types. More general high-
level terms can be used in the technical documentation instead of low-level particular subclasses, such as
“compressor”, “compressor plant” and “compressor equipment” after the first full description of functional and
design subclasses, and in all those cases where there is no possibility of confusion with other subclasses or
there is no need to differentiate between specific subclasses.

Figure 1 — Design classes of compressors
2 © ISO 2012 – All rights reserved

2.2 Classification by equipment type
Class, Subclass and definition Illustration
term (example only)
Compressor A machine or apparatus converting different types of energy into the
(generic term) potential energy of gas pressure for displacement and compression of
gaseous media to any higher pressure values above atmospheric pressure
with pressure-increase ratios exceeding 1,1.
NOTE 1 Similar equipment with pressure-increase ratio values of up to 1,1 is
regarded as ventilator.
Compressor A compressor in which conversion of different types of See 2.3 to 2.5 for specific
machine energy into the potential energy of gas pressure is effected classes
by mechanical motions of solid working members.
NOTE 2 In some design types of compressor machine,
intermediate liquid service media can be used for driving-force
transmitting from one solid member to the other one (e.g. in
electrically/hydraulically driven piston and diaphragm compressor).
Compressor A compressor in which conversion of different types of See 2.3 to 2.5 for specific
apparatus energy into the potential energy of gas pressure is effected classes
by stationary positions of working members effecting basic
energy conversion functions, mechanical motions being
used only for auxiliary functions, such as gas inlet and
outlet, and energy-agent supply and withdrawal.
2.3 Classification of compressor apparatuses by operation principles
Class, Subclass Definition Illustration
term (example only)
Compressor Ejector A compressor apparatus of dynamic type, comprising
apparatus suction chamber, cylindrical throat and diffuser, in which
auxiliary
the gas-pressure increase is obtained in continuous flow
fluid
by initial increasing its kinetic energy by mechanical action
of the motive high-velocity auxiliary fluid stream entraining

the gas into the accelerating mixed stream, and
successive conversion of the kinetic energy into the

potential energy of the mixture pressure by deceleration of
the mixture flow in the diffuser, the high velocity of the
gas
motive auxiliary-fluid steam being created by its
expansion in the nozzle from pressurized state to the
initial or lower pressure of the gas being compressed.
Thermo- A compressor apparatus of displacement type in which
compressor the gas pressure increase, its discharge and gas intake
are obtained by cyclically heating and cooling of the

closed volumes of the gas.
Adsorption A compressor apparatus of displacement type in which
compressor the gas pressure increase, its discharge and gas intake
are obtained by cyclical adsorption of the gas by special
adsorbents such as metal hydrides and its desorption at

higher pressures by changing temperature conditions.

Class, Subclass Definition Illustration
term (example only)
Compressor Acoustical A compressor apparatus of displacement type in which
apparatus compressor the gas pressure increase, its discharge and gas intake
Acoustical generator
(continued) are obtained by cyclical formation of low- and high-
pressure phases in the closed volumes of the gas due to

actions of pressure waves emitted by an acoustical
generator
Pressure – A compressor apparatus of displacement type in which
Fixed end plates
shock the compression of successive volumes of the gas is
compressor effected by shock waves created by the second high-
(Pressure pressure energy-carrying gas in several longitudinal
exchanger) through channels arranged circumferentially on the
cylindrical drum, these channels being cyclically closed by
rotation of the dr
...