Overview
ISO 21360-6:2023 - "Vacuum technology - Standard methods for measuring vacuum‑pump performance - Part 6: Cryogenic vacuum pumps" defines standardized test methods for characterizing the performance of two‑stage, closed‑loop gaseous helium cryogenic vacuum pumps that can be directly flanged to a vacuum chamber. The document complements ISO 21360‑1 and provides specific procedures to measure volume flow rate (pumping speed), maximum throughput, pumping capacity, base pressure, cooldown time, and crossover value for cryogenic pumps.
Key topics and technical requirements
- Scope & applicability: Two‑stage closed‑loop gaseous helium cryogenic pumps, direct flange connection to test dome or quick‑acting valve; cold surfaces must not protrude into the test dome.
- Test gases & purity: Measurements use at least 99.9% pure test gas-nitrogen (or dry air), argon, and hydrogen; gas order and regeneration rules are specified.
- Volume flow rate (pumping speed):
- Two accepted measurement methods: throughput method (preferred when accurate flow meters are available) and orifice method (for low throughputs).
- Pretreatment procedure: admit a defined gas quantity α·qv (α specified in the standard) before measurement.
- Stability criteria: pressure stability ±3% (±5% for hydrogen) before accepting readings.
- Maximum throughput (Qmax): defined as the condensable‑gas throughput that raises and stabilizes the second‑stage temperature at 20 K; used to verify manufacturer claims.
- Pumping capacity (qpc): quantity pumped until the volume flow rate falls to 50% of initial value; includes recovery/conditioning performance note.
- Base pressure (pb): pressure obtained in the test dome within 24 h after completing cooldown; can be measured with the pump blanked off in some tests.
- Cooldown time: measured from room temperature (293 K ± 3 K) start to the second stage reaching 20 K.
- Crossover value (qcv): maximum short‑term admission of nitrogen the pump can accept while keeping second stage ≤20 K.
- Water vapour: volume flow rate is normally calculated (see Annex A) because stable water vapour flows are difficult to measure directly.
- Reporting: the standard specifies required test report content (general info, pump parameters, test equipment & conditions, operational parameters, and measured performance).
Applications
- Acceptance and performance testing of cryogenic vacuum pumps
- Manufacturer verification and R&D for cryopumps
- Quality control for semiconductor, accelerator, cryogenics, and research facilities
- System integration and metrology in vacuum technology laboratories
Who should use this standard
- Pump manufacturers and design engineers
- Test and calibration laboratories
- Vacuum system integrators and QA teams
- Researchers and facility engineers working with cryogenic vacuum systems
Related standards
- ISO 21360‑1:2020 - General description and baseline methods (this Part 6 takes precedence where it conflicts).