Test Efficiency of Differential-pressure Method And Equal- pressure Method 1/3

March 25, 2009 - PRLog -- Excerption. Full and more theses: http://www.labthink.cn/service/Topic.aspx
Some people hold that equal-pressure method is superior to differential-pressure method in terms of test efficiency, which proves to be incorrect. Such opinion correlates with people’s misunderstanding about test duration and test efficiency of gas permeability testing. This article analyzes test efficiency of gas permeability testing based on the characteristics of the test. Based on current testing technology, this article also analyzes test efficiency of differential-pressure method and equal-pressure method.
1. How to Calculate Efficiency Of Gas Permeability Test
Test duration must be made clear before evaluating efficiency of specific test method. Differing from other physical testing, in addition to the state adjustment of specimen, gas permeability testers also require regulation time, which includes both warm up time of instruments and purge time of system. No matter what measures are adopted, the pollution of test cells and gases inside gas pipeline resulting from specimen attachment cannot be avoided. Gas impurity (non-test gas) will influence gas transmission process of specimen and in turn affects test results. Therefore, prior to gas transmission, gas impurity must be removed from test cells and gas pipeline.
How does system purge time relates with test duration? This problem is the root of people’s wrong opinion concerning efficiency of gas permeability test, i.e. having no explicit definition of test duration. Thus, whether purge time should be concluded into test duration has become random. For example, evacuation time of differential-pressure method is taken into account while purge time of equal-pressure method is excluded. Test duration of gas permeability test should include system purge time and the time to set up transmission equilibrium. Test efficiency should not be evaluated only by comparing test duration of equal-pressure method with the time sum of test duration and evacuation time of differential-pressure method.

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