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Lube-Tech


Prescreening for vane pump simulation: Cyclic- stress vane-on-flat Falex Multispecimen? The Falex MultiSpecimen Test Machine (Figure 1a) is a versatile commercial system for evaluating friction, wear, and abrasion characteristics of materials, coatings, and lubricants. Standard Test Methods and Application Specific Custom testing programs are possible due to user selected contact geometries, motions, velocities, temperatures, contact pressures, and test specimen materials. One test apparatus meets many test specifications and simulates a broad range of field applications. Applications include research and development, quality control, product qualification and the evaluation of physical and performance characteristics of materials, coatings, and lubricants. Based on this machine a vane pump prescreening setup was developed by using a special vane-on-disk test configuration (Figure 1b) and a hydraulic fluid recirculation system.


To simulate the compression/de-compression pressure pattern contact conditions in the actual vane pumps, a new standardised test disk was designed, Figure 2. This standardised sample is made of 52100 steel and has a hardness of 58-63 HRC and an average roughness Ra of 0.23-0.38 µm. The grooves on this sample create the variable pressures encountered by the vanes in a pump during each cycle. In particular three different areas can be discerned on these disks, as indicated in Figure 2. Area A corresponds to the area of the highest pressure, area B to medium pressure and C to the lowest pressure. The grooves also allow a proper re-lubrication of the sliding contact, similar to pump behavior. As counter materials three high stress M-2 tool steel vanes having a hardness of 58-63 HRC, average roughness Ra 0.15-0.30 µm and a 6.35 mm radius Figure 2. This design was optimised to represent the pressure peaks and the refreshing of the contact as it occurs in the wane pump tests, by rescaling the geometry of the actual test. Prior to each test, the disk and vanes were cleaned with heptane in an ultrasonic bath for 10


PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE


No.114 page 2


min, dried and then weighted in an electrobalance with an accuracy of ± 0.1 mg.


Fig 1. (a) FALEX MultiSpecimen tester


Fig 1. (b) Vane-on-Disk contact configuration


Fig 2. Cyclic stress disk and Vanes for Falex MultiSpecimen vane pump setup


To avoid any possible contamination of the tested oils, before each series of tests (for the same oil), the recirculation system, the vane holder adapter, the chamber table and the test chamber assembly were thoroughly cleaned with an appropriate solvent. Several rinses may be necessary to completely remove all remaining test fluids from the previous run. The setup was then dried by dry air and visually inspected to insure that it is free from any used test fluid, solvent, wear particles or other surface contaminants that might influence the test outcome. Afterwards, the recirculation system was flushed with 1 litre of test fluid for 5 minutes to remove all traces of cleaning


LUBE MAGAZINE NO.143 FEBRUARY 2018 39


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