ISO/PWI 21360-7

Vacuum technology — Standard methods for measuring vacuum-pump performance — Part 7: Vapour driven vacuum pumps

Scope

This standard specifies terms and definitions, principles and methods of testing vapour driven vacuum pumps and single-stage and multi-stage steam jet vacuum pumps and steam jet compressors
Following general denomination, vapour driven vacuum pumps refer to diffusion pumps and diffusion ejector pumps. These vapour driven vacuum pumps are operated with mercury vapour or oils vapours with very low vapour pressure. Diffusion pumps rely on molecular flow of the suction flow to the motive fluid. Diffusion ejector pumps have laminar flow of the suction load to the vapour jet. Steam jet vacuum pumps and steam jet compressors are driven by water vapour (steam). The term steam jet compressor indicates its function of pressure increase. Operating under vacuum, it can be considered as a vacuum pump as well. The steam jet vacuum pump requires viscous flow of the suction load to the steam jet, usually operating under turbulent conditions.
While vapour vacuum pumps can create a vacuum in the region of 10-1 to 10-9 Pa, steam jet vacuum pumps create vacuums of 10 Pa and higher.
Due to the different working conditions, the test procedures for the different vapour driven vacuum pumps have to be treated separately. For the sake of usability this document will first show the test methods for vapour vacuum pumps. In the later part it will reflect on test methods for steam jet vacuum pumps and steam jet compressors using water vapour as the motive medium and gas/steam mixtures as suction media, for the purposes of measuring performance and for acceptance testing.
For measurements with suction media of different composition and temperature, an equivalent performance is defined so that the acceptance measurement and specified design data can be converted from one to another.
If the design data exceeds the capabilities of the acceptance test field, methods for model testing are specified, e.g. to take into account highly superheated motive steam or high motive pressures.
Performance measurements conducted on steam jet vacuum pumps are intended to provide proof that the data given by the manufacturer with regard to performance, steam and water consumption is correct under the required conditions, irrespective of the make of the pump. The purpose of this standard is to provide the same prerequisites for the preparation, performance, evaluation and documentation of acceptance measurements. The measurements can be conducted at the manufacturer’s location or at the installation site, where facilities are provided that comply with the specifications of this standard.
Single-stage and multi-stage steam jet vacuum pumps without intercondensers shall be tested as an entire unit. Multi-stage steam jet vacuum pumps with intercondensers shall only be tested in this way if the conditions specified in 6.2 are met; failing this, they may be tested in stages.