【国外标准】 Standard Practice for Leakage Measurement Using the Mass Spectrometer Leak Detector or Residual Gas Analyzer in the Hood Mode

5.1 Test Method A—This test method is the most frequently used in leak testing components. Testing of components is correlated to a standard leak, and the actual leak rate is measured. Acceptance is based on the maximum system allowable leakage. For most production needs, acceptance is based on acceptance of parts leaking less than an established leakage rate, which will ensure safe performance over the projected life of the component. Care must be exercised to ensure that large systems are calibrated with the standard leak located at a representative place on the test volume. As the volume tends to be large (>1 m3) and there are often low conductance paths involved, a check of the response time as well as system sensitivity should be made.5.2 Test Method B—This test method is used for testing vacuum systems either as a step in the final test of a new system or as a maintenance practice on equipment used for manufacturing, environmental test, or conditioning parts. As with Test Method A, the response time and a system sensitivity check may be required for large volumes.5.3 Test Method C—This test method is to be used only when there is no convenient method of connecting the LD to the outlet of the high-vacuum pump. If a helium LD is used and the high-vacuum pump is an ion pump or cryopump, leak testing is best accomplished during the roughing cycle, as these pumps leave a relatively high percentage of helium in the high-vacuum chamber. This will limit the maximum sensitivity that can be obtained.1.1 This practice covers procedures for testing the sources of gas leaking at the rate of 1 × 10 −8 Pa m3/s (1 × 10−9 standard-cm3/s at 0 °C) or greater. These test methods may be conducted on any object that can be evacuated and to the other side of which helium or other tracer gas may be applied. The object must be structurally capable of being evacuated to pressures of 0.1 Pa (approximately 10−3 torr).1.2 Three test methods are described;1.2.1 Test Method A—For the object under test capable of being evacuated, but having no inherent pumping capability.1.2.2 Test Method B—For the object under test with integral pumping capability.1.2.3 Test Method C—For the object under test as in Test Method B, in which the vacuum pumps of the object under test replace those normally used in the leak detector (LD).1.3 Units—The values stated in either SI or std-cc/sec units are to be regarded separately as standard. The values stated in each system may not be exact equivalents: therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.