ISO/TC 112/WG 1 - Vacuum pumps

This document specifies three methods for measuring the volume flow rate and one method each for measuring the base pressure, the compression ratio, and the critical backing pressure of a vacuum pump. The first method for measuring the volume flow rate (the throughput method) is the basic concept, in which a steady gas flow is injected into the pump while the inlet pressure is measured. In practice, the measurement of gas throughput may be complicated or inexact. For this reason, two other methods are specified which avoid the direct measurement of throughput. The second method for measuring the volume flow rate (the orifice method) is used when there is very small throughput at very small inlet pressures (under a high or ultra-high vacuum). It is based on measuring the ratio of pressures in a two-chamber test dome in which the two chambers are separated by a wall with a circular orifice. The third method for measuring the volume flow rate (the pump-down method) is well suited for automated measurement. It is based on the evacuation of a large vessel. The volume flow rate is calculated from two pressures, before and after a pumping interval, and from the volume of the test dome. Different effects, such as leak and desorption rates, gas cooling by nearly isentropic expansion during the pumping interval, and increasing flow resistance in the connection line between test dome and pump caused by molecular flow at low pressures, influence the results of the pressure measurement and the resulting volume flow rate. The choice of the required measurement methods depends on the properties of the specific kinds of vacuum pump, e.g. the measurement of the critical backing pressure is only necessary for vacuum pumps which need a backing pump. All data that are measured on a vacuum pump, but not specified in this document (e.g. measurement of power consumption), are defined in the specific pump standard.

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 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.

This document gives definitions of vacuum pumps and related terms. It is a continuation of ISO 3529‑1 which defines general terms used in vacuum technology.

This document specifies methods and special requirements for measuring the maximum tolerable pressure difference, effective compression ratio, compression ratio with zero throughput and overflow valve pressure difference of mechanical booster vacuum pumps. It applies to mechanical booster vacuum pumps employed for medium vacuum or rough vacuum applications including gas-cooled mechanical booster vacuum pump and multiple mechanical booster vacuum pump systems. It covers particular characteristics of mechanical boosters that are different from those of the usual positive displacement vacuum pumps. Maximum tolerable pressure difference Δpmax, effective compression ratio Keff, compression ratio with zero throughput K0 and overflow valve pressure difference Δp1 are special characteristics of the performance of mechanical booster vacuum pumps.

This document, in conjunction with ISO 21360-1, specifies methods for the measurement of performance characteristics of turbomolecular vacuum pumps. It is applicable to all sizes and all types of turbomolecular vacuum pumps, including those — with mechanical or magnetic bearings; — with or without an additional drag stage(s) or other pumping stages on the shaft; — with one or more inlet ports. Since turbomolecular vacuum pumps are backed by primary pumps, their performance cannot be completely defined by the volume flow rate curve. Also, the driving device and the backing pressure of the turbomolecular vacuum pump is important to the performance. The following completes the performance characteristics: — information about throughputs and backing pressure of the turbomolecular vacuum pump; — the compression ratio curve (compression ratio vs backing pressure of turbomolecular vacuum pump).

ISO 27892:2010 specifies a method for the measurement of rapid shutdown torque (destructive torque) of turbomolecular pumps in which gas momentum is produced by axial flow type blades and/or helical channels. The main forces leading to failure of turbomolecular pumps are torques around the rotational axis. Other insignificant forces and moments that can occur lie outside the scope of ISO 27892:2010. There are two kinds of failure: rapid shutdown by whole burst and softer crash of rotor. ISO 27892:2010 applies to both. The same measurement method can be used for turbomolecular pumps and molecular drag pumps.

The measurements deal with diffusion pumps, ejector pumps, and booster pumps, i.e. pumps capable of operation in both the molecular and laminar flow regions.

The considered method of measurement deals with vapours jet vacuum pumps, diffusions pumps and diffusion-ejector pumps. The dependence of the performance of these pumps on the backing pressure can only be completely described be means of a curve relating the inlet and backing pressure over the range of operation. The recommended test dome and the principle of the test equipment are illustrated.

This part of ISO 21360 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 In this part of ISO 21360, it is necessary to use the determinations of volume flow rate and base pressure specified in ISO 21360‑1. This part of ISO 21360 also applies to the testing of other types of pumps which can discharge gas against atmospheric pressure, e.g. drag pumps.

ISO 21360:2007 is a basic standard which defines three different methods for measuring the volume flow rate and one method each for measuring the base pressure, the compression ratio and the critical backing pressure of a vacuum pump. The choice of the required measurement methods depends on the properties of the specific kinds of vacuum pump, e.g. the measurement of the critical backing pressure is only necessary for vacuum pumps which need a backing pump. All data that is measured on a vacuum pump but not described in ISO 21360:2007 (e.g. measurement of power consumption) is defined in the specific pump standard.

ISO 5302:2003 specifies methods for the measurements of performance characteristics of turbomolecular pumps. It is applicable to all sizes and all types of turbomolecular pumps, with mechanical or magnetic bearings, and with or without an additional drag stage.

The method of determining the volume of gas which flows in unit time through the pump inlet are specified. The considered pumps discharge the gas against atmosphere pressure and achieve a limiting inlet pressure less than 100 pa in one stage.

The considered pumps discharge the gas against atmosphere pressure and achieve a limiting inlet pressure of less than 100 Pa in one stage. The method adopted is that the ultimate pressure is measured at a specified temperature in a specified form of test dome attached to the inlet of the pump.

In addition to terms used in the three official ISO-languages (E, F, R) the equivalent terms in German are given. The annex provides a classification table of vacuum pumps in the above mentioned languages.