Overview
ISO 21360-4:2018 - "Vacuum technology - Standard methods for measuring vacuum-pump performance - Part 4: Turbomolecular vacuum pumps" specifies standardized test methods and reporting for measuring the performance of turbomolecular vacuum pumps. Used together with ISO 21360-1, this part covers all sizes and types of turbomolecular pumps (mechanical or magnetic bearings, with or without drag stages, single or multiple inlet ports). The standard recognizes that turbomolecular pump performance depends on the driving device and the backing (primary) pump, and supplements conventional pumping-speed data with throughput, compression-ratio and backing-pressure information.
Key topics and technical requirements
- Scope & applicability: Applies to all turbomolecular vacuum pumps and typical configurations; complements ISO 21360-1.
- Test gases: Measurements use at least 99.9% pure test gases (e.g., nitrogen, hydrogen, helium, argon).
- Volume flow rate / pumping speed: Defined measurement procedures using the throughput method and the orifice method (orifice recommended for low throughputs).
- Backing-pump influence: Procedures and formulae (with derivation in Annex A) to quantify how the backing pump size affects effective pumping speed.
- Maximum throughput (Qmax): Methods to determine the highest continuous gas load a pump can handle without damage; tests require monitoring limiting parameters over sustained intervals.
- Compression ratio: Measurement of compression ratio vs. backing pressure; includes effective and maximum compression-ratio definitions and curves.
- Critical backing pressure: Determination of the maximum allowable backing pressure for continuous operation without overload.
- Base pressure and ultimate pressure: Measurement of base pressure after conditioning; guidance on ultimate-pressure reporting.
- Vibration measurement: Test apparatus and procedures to quantify operational vibration.
- Test reporting: Required data and formats for reporting pumping speed, compression ratio, maximum throughput, critical backing pressure, base pressure and vibrational results.
Practical applications & users
ISO 21360-4:2018 is essential for:
- Manufacturers of turbomolecular pumps for product specification, quality control and data sheet preparation.
- Independent test laboratories performing standardized performance verification.
- Vacuum system designers and integrators who need reliable pump selection data considering backing-pump interactions.
- R&D and QA engineers validating pump performance under specified gas loads and backing conditions.
- Purchasing and procurement teams evaluating vendor claims and comparing pumps on a like-for-like basis.
Using ISO 21360-4 ensures consistent, comparable performance data-critical when selecting turbomolecular pumps for semiconductor fabrication, analytical instruments, research laboratories, thin-film deposition and other high-vacuum applications.
Related standards
- ISO 21360-1:2012 - General description and common methods for measuring vacuum-pump performance (normative reference for Part 4).