ISO 21360-6:2023

INTERNATIONAL ISO
STANDARD 21360-6
First edition
2023-12
Vacuum technology — Standard
methods for measuring vacuum-pump
performance —
Part 6:
Cryogenic vacuum pumps
Technique du vide — Méthodes normalisées pour mesurer les
performances des pompes à vide —
Partie 6: Pompes à vide cryogéniques
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Test methods . 3
5.1 Test gas . 3
5.2 Measurement of the volume flow rate (pumping speed) . 3
5.2.1 General . 3
5.2.2 Pretreatment procedure . 3
5.2.3 Volume flow rate (pumping speed) measurement by the throughput method . 3
5.2.4 Volume flow rate (pumping speed) measurement by the orifice method . 3
5.2.5 Measurement of water vapour volume flow rate (pumping speed) . 4
5.3 Maximum throughput measurement . 4
5.3.1 General . 4
5.3.2 Measurement method . 4
5.3.3 Measurement setup . 4
5.3.4 Measuring procedure . 4
5.4 Pumping capacity measurement . 4
5.4.1 General . 4
5.4.2 Measurement setup . 5
5.4.3 Measuring procedure . 5
5.5 Measurement of base pressure cryogenic vacuum pump . 5
5.6 Measurement of cooldown time . 5
5.6.1 General . 5
5.6.2 Measurement setup . 6
5.6.3 Measuring procedure . 6
5.7 Measurement of crossover value . . 6
5.7.1 General . 6
5.7.2 Measurement setup . 6
5.7.3 Measuring procedure . 8
6 Test report . 8
6.1 Content . . 8
6.2 Report on general information. 9
6.3 Report on pump parameters . 9
6.4 Report on test equipment and conditions . 9
6.5 Report on operational parameters . 9
6.6 Report on pump performance . 9
Annex A (informative) The volume flow rate calculation for the water vapour.11
Bibliography .12
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 112, Vacuum technology.
A list of all parts in the ISO 21360 series can be found on the ISO website.
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iv
Introduction
This document specifies methods for measuring the performance data of cryogenic vacuum pumps.
This document complements ISO 21360-1, which provides a general description of the measurement
of performance data of vacuum pumps. This document takes precedence in the event of a conflict with
ISO 21360-1.
v
INTERNATIONAL STANDARD ISO 21360-6:2023(E)
Vacuum technology — Standard methods for measuring
vacuum-pump performance —
Part 6:
Cryogenic vacuum pumps
1 Scope
This document specifies methods for measuring the volume flow rate, maximum throughput, pumping
capacity, base pressure cryogenic vacuum pump, cooldown time and crossover value of cryogenic
vacuum pumps.
It is applicable to two-stage, closed-loop gaseous helium cryogenic vacuum pumps, which can be
directly flanged to a vacuum chamber.
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 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
base pressure cryogenic vacuum pump
p
b
pressure obtained in the test dome within 24 h of completing cooldown
Note 1 to entry: It is possible that the base pressure is not the lowest pressure obtainable with the cryogenic
vacuum pump. The base pressure represents the lowest pressure that can be obtained after reasonable
conditioning of the cryogenic vacuum pump and the test dome without any test gas (see 5.5).
Note 2 to entry: For many practical applications (e.g. only cooldown time is tested, see 5.6), base pressure also
can be obtained in the cryogenic vacuum pump with a blank-off flange at the entrance.
3.2
cooldown time
time elapsed between starting the cryogenic vacuum pump at room temperature (293 K ± 3 K) at a
starting pressure as indicated by the manufacturer and the point at which the temperature of the
second stage (3.6) reaches 20 K
Note 1 to entry: The roughing valve should only be closed when the action of closing does not cause the pressure
in the cryogenic vacuum pump to rise to a value above the starting pressure.
3.3
crossover value
q
cv
maximum amount of nitrogen gas which can be admitted into the pump over a short time with the
temperature of the second stage (3.6) remaining ≤20 K during the test gas flow
3.4
pumping capacity
q
pc
quantity of gas, which has been pumped up to the moment when the volume flow rate has reduced to
50 % of the initial value measured
Note 1 to entry: After having pumped this amount of gas, the pump still can reduce the pressure in the test dome
-3
down to a value of p ≤10 Pa in less than 10 min to ensure that a certain pumping performance is still available.
3.5
maximum throughput
Q
max
maximum quantity of condensable gas flow, which a cryogenic vacuum pump can pump
3.6
second stage
lower temperature side cooling station with the cold panels of a closed-loop, two-stage gaseous helium
cold head
4 Symbols
Symbol Designation Unit
-1 3 -1
Q
gas throughput of cryogenic vacuum pump Pa·l·s (or Pa·m ·s )
-1 3 -1
Q
maximum throughput Pa·l·s (or Pa·m ·s )
max
q crossover value Pa·l(or Pa·m )
cv
q
pumping capacity Pa·l(or Pa·m )
pc
pp,
pressures in the test dome for the orifice method Pa
de
p base pressure cryogenic vacuum pump Pa
b
p vacuum pressure on inlet Pa
p
starting pressure Pa
D
inner diameter of test dome m
D nominal diameter of test dome m
N
T
maximum temperature of the second stage K
max
5 Test methods
5.1 Test gas
All measurements in this document should be performed with at least 99,9 % (by mass) pure test gas.
The test gas should be nitrogen (alternatively dry air), argon and hydrogen.
5.2 Measurement of the volume flow rate (pumping speed)
5.2.1 General
The measurement of volume flow rate is specified in ISO 21360-1.
Pretreatment (see 5.2.2) is recommended before measuring the pumping speed of the test gas (except
hydrogen).
When the pressure remains stable within ±3 % (for hydrogen ±5 % is acceptable) for the following
minute, the average value per minute can be regarded as valid p .
If several test gases are used, without regenerating the pump completely, the gases should be used in
the following order: hydrogen, nitrogen (alternatively dry air), argon.
If during measurement more than 30 % of the pumping capacity as indicated by the manufacturer is
admitted, the cryogenic vacuum pump should be regenerated.
The test pump should be directly flanged to the test dome (see 5.7.2, Figure 1) or the quick-acting valve
(see 5.7.2, Figure 2). When using the test dome described in ISO 21360-1:2020, Figure 3, the cold surfaces
of the te
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