Multi-pass test

Since the main function of any filter is the removal and separation of impurities, and the filters are rated in many different ways, it is inevitable that many tests are available to substantiate these ratings. The tests include the bubble point test used to establish the mean filter rating and the multi-pass test which provides the beta ratio of the hydraulic and lubrication filters. 

The multi-pass test simulates well the behaviour of clarifying filters in hydraulic or lubricating fluid systems, because the recycle of the filtrate carries with it the undersized particles, so that the proportion of fine particles increases continuously during the test. It was the first filter test to become an ANSI standard, and is now incorporated into an international standard (see BS ISO 16889 1999). It should be noted that the beta ratio will be different from that determined by this test if it is used in a system that contains particle distributions that differ from the distribution used in the test. 

Companies offering testing services, such as IFTS in France, or Palas in Germany, have fully automated test rigs, able to carry out single and multi-pass tests quickly and accurately. 

A.STM.B764, Std. Methodfor Simultaneous Thickness and Electrochemical Potential determination of Individual Eayers in Multi-layer Mickel deposit (STEP test), American Society for Testing and Materials, Philadelphia, Pa., 1986. 

Liu and co-workers [16] investigated the wear behaviour of ultra-high molecular weight polyethylene (UHMWPE) polymer. They concluded that the applied load is the main parameter and the wear resistance improvement of filler reinforced UHMWPE was attributed to the combination of hard particles, which prevent the formation of deep, wide and continuous furrows. Bijwe and co-workers [17] and Xu and Mellor [18] tested polyamide 6 (PA), polytetrafluoroethylene (PTFE) and their various composites in abrasive wear under dry and multi-pass conditions against SiC paper on a pin-on-disc tribometer. They concluded that the polymers without fillers had better abrasive wear resistance than their composites. 

C1477. (2008). Standard test method for isotopic abundance analysis of uranium hexafluoride by Multi-Collector, Inductively Coupled Plasma-Mass Spectrometry. West Conshohocken, PA ASTM. 

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