ISO 21360-2:2020

INTERNATIONAL ISO
STANDARD 21360-2
Second edition
2020-06
Vacuum technology — Standard
methods for measuring vacuum-pump
performance —
Part 2:
Positive displacement vacuum pumps
Technique du vide — Méthodes normalisées pour mesurer les
performances des pompes à vide —
Partie 2: Pompes à vide volumétriques
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, 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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Test methods . 3
5.1 Measurement of the volume flow rate . 3
5.1.1 Measurement methods . 3
5.1.2 Throughput method . 3
5.1.3 Pump-down method . 4
5.1.4 Operating conditions . 4
5.2 Measurement of the base pressure . 4
5.3 Measurement of water vapour tolerance . 4
5.4 Determination of the power consumption . 4
5.4.1 General. 4
5.4.2 Measuring conditions . 4
5.4.3 Measuring procedure . 4
5.5 Lowest start-up temperature . 5
5.6 Measuring uncertainties . 5
Annex A (informative) Measurement of the water vapour tolerance . 6
Annex B (informative) Calculation of the water vapour tolerance.13
Annex C (informative) Table of the saturation vapour pressure of water .14
Bibliography .16
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 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 112, Vacuum technology.
This second edition cancels and replaces the first edition (ISO 21360-2:2012), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— Note added to 3.2 and 3.3. The test report should contain the ambient conditions.
ϕ
HO
— In A.1.5, the formula has been corrected to pp= T .
()
a S 1
A list of all parts in the ISO 21360 series can be found on the ISO website.
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 2020 – All rights reserved

Introduction
This document specifies methods for measuring the performance data of positive-displacement
vacuum pumps. This document complements ISO 21360-1, which provides a general description of the
measurement of performance data of vacuum pumps.
The methods described here are well known from existing national and International Standards.
The aim in drafting this document was to collect together suitable methods for the measurement of
performance data of positive-displacement vacuum pumps. This document takes precedence in the
event of a conflict with ISO 21360-1.
INTERNATIONAL STANDARD ISO 21360-2:2020(E)
Vacuum technology — Standard methods for measuring
vacuum-pump performance —
Part 2:
Positive displacement vacuum pumps
1 Scope
This document specifies methods for measuring the volume flow rate, base pressure, water vapour
tolerance, power consumption, and the lowest start-up temperature of positive displacement vacuum
pumps, which discharge gas against atmospheric pressure and with a usual base pressure <10 kPa.
In this document, it is necessary to use the determinations of volume flow rate and base pressure
specified in ISO 21360-1.
This document also applies to the testing of other types of pumps which can discharge gas against
atmospheric pressure, e.g. drag pumps.
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 21360-1:2020, Vacuum technology — Standard methods for measuring vacuum-pump performance —
Part 1: General description
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21360-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gas ballast
gas or air inlet into the swept volume of the pump
3.2
water vapour tolerance
p
HO
maximum water vapour pressure which can be conveyed by the pump without condensation in the pump
Note 1 to entry: If there is no problem of water vapour condensation, e.g. when an oil and water separation unit is
included, maximum water vapour pressure is acceptable.
Note 2 to entry: The test report should contain the ambient conditions.
3.3
water vapour capacity
mass of water which can be conveyed by the pump without condensation per time
Note 1 to entry: The test report should contain the ambient conditions
3.4
swept volume
V
SW
input volume, which is conveyed by the pump during one cycle
3.5
saturation vapour pressure
p
s
pressure exerted by the vapour of a pure chemical substance in equilibrium with a condensed phase
(liquid or solid or both) in a closed system
Note 1 to entry: For each substance, saturation vapour pressure is a function of temperature only.
3.6
water vapour saturation temperature
temperature corresponding to the water saturation vapour pressure (3.5)
3.7
compression energy
energy needed to compress a gas volume
4 Symbols and abbreviated terms
Symbol Designation Unit
α pressure-increasing factor to open the exhaust valve
ϕ relative humidity of air %
HO
κ adiabatic exponent
L molar evaporation energy J/mol
P power consumption of the pump at ultimate pressure at specified rotational W
frequency
P power consumption of the pump at ultimate pressure at specified rotational fre- W
0B
quency with maximum gas ballast
P maximum power consumption of the pump at specified rotational frequency W
max
p standard atmospheric pressure Pa
p air partial pressure of exhaust gas Pa
p water vapour partial pressure in atmosphere Pa
a
p air partial pressure in atmosphere Pa
B
p water vapour tolerance Pa
HO
p saturation water vapour pressure Pa
s
p saturation water vapour pressure at temperature T Pa
T
2 © ISO 2020 – All rights reserved

q volume flow rate of the pump m /s
V
q volume flow rate of the gas ballast duct m /s
VB
R general gas constant: R = 8,314 3 J/(mol·K)
T temperature corresponding to p K
T
T environmental temperature °C
T exhaust pump temperature °C
T exhaust temperature without throughput K
T corrected exhaust pump temperature for water vapour K
2cr
T exhaust saturation temperature dependent on p K
2s 1
V exhaust volume m
V swept gas ballast volume m
B
V swept volume m
SW
W adiabatic compression energy J
ad
W adiabatic compression energy for water vapour J
ad,H O
W adiabatic compression energy for air J
ada
W correction factor for the pump exhaust temperature
cr
5 Test methods
5.1 Measurement of the volume flow rate
5.1.1 Measurement methods
Volume flow rate measurement methods are specified in ISO 21360-1:2020, 5.1, 5.2 and 5.3. The
throughput method or the pump-down method shall be used for the volume flow rate measurement.
If no other descriptions or experimental arrangements are shown, those of ISO 21360-1 shall be used.
5.1.2 Throughput method
The standard method is the throughput method. It can be used for all pumps to which this document
applies.
The volume of the test dome shall be ≥2V , where V is the swept volume, for rotary plunger-type
SW SW
and fixed vane-type vacuum pumps. The volume of the test dome shall be ≥5V for other types of
SW
vacuum pump. The type of test dome shall be in accordance with ISO 21360-1.
The transition to the pump inlet flange shall be made through a 45° conical adaptor, as shown in
ISO 21360-1:2020, Figure 1, if the inlet flange diameter, D , is less than the inner diameter, D, of the test
N
dome for positive displacement-type vacuum pumps.
5.1.3 Pump-down method
The pump-down method is suitable for smaller pumps (e.g. up to 0,01 m /s), because a large test dome
is required. The volume of the test dome shall be larger than the expected maximum volume flow rate,
in cubic metres per second, multiplied by a factor of 120 s.
5.1.4 Operating conditions
The pump shall be connected to the equipment shown in the experimental setup and switched on. Before
taking the measurements, the pump should be operated until it has reached its normal operational
temperature. The rotational frequency ("speed") shall not deviate by more than ±3 % from the nominal
frequency.
If the test pump has a gas ballast device, the volume flow rate shall first be measured without and then
with gas ballast.
The environmental conditions shall be in accordance with ISO 21360-1.
5.2 Measurement of the base pressure
The measurement of the base pressure is specified in ISO 21360-1:2020, 5.4. It is measured with the
same experimental setup as specified in ISO 21360-1:2020, Clause 5. The measurement shall be done
first without and later with gas ballast. The measurements can be carried out in random order when
the order has no influence on them.
5.3 Measurement of water vapour tolerance
Water vapour tolerance is specified as the maximum pure-water vapour pressure at the input of the
pump. Several methods of water vapour tolerance measurement, in pascals, have been reported. An
example of the measurement method of water vapour tolerance is given in Annex A.
Several methods of water vapour capacity measurement, in kilograms per second, have been reported.
An example of the conversion between water vapour tolerance and water vapour capacity values is
shown in Reference [1] p. 331.
See also Reference [1] p. 329-333, and Reference [2] p. 60.
5.4 Determination of the power
...