Lube-Tech
* Falex Tribology N.V., Wingepark 23B, B3110, Rotselaar, Belgium ** Falex Corporation, 1020 Airpark Drive, Sugar Grove, IL 60554, USA
State of the art on vane pump testing Hydraulic systems are widely used in the manufacturing, construction, forestry, mining and transportation industries. Over the years, systems for the transmission and distribution of power have become more complicated, their applications more numerous and their operating conditions more demanding. So hydraulic fluids need to get better to match the increasing industrial demand and requirements. Despite a large variety of commercial hydraulic fluids, pump manufacturers and users often have no comparable information on friction and wear properties of these fluids, due to a lack of efficient tribological techniques that simulate accurately the in-field conditions of a pump.
The current state-of-the-art for testing fluids for vane pumps is mainly the Conestoga-Vickers Vane Pump stand (ASTM D7043 - DIN 51389 - ISO 20763) or similar component testers. Standardised pump stands would provide the best possible representation of actual working conditions, but have their practical limitations. Apart from the investment cost of such pump stands, a critical issue is the test duration : 100 hrs for the ASTM D7043 method and 250 hrs for the ISO 20763 method. Also a large quantity of hydraulic fluids per test is needed (30 L for ASTM D7043 and 60 L for ISO 20763). These tests only measure wear
38 LUBE MAGAZINE NO.143 FEBRUARY 2018
losses, no information about frictional behavior of the tribosystem are measured. In 1996, G.E. Totten presented an overview of bench tests for Hydraulic Fluid performance, and came to three important conclusions: 1) none of the obvious laboratory tests (Four Ball test, Pin & Vee Block, SRV, Timken) provided any correlation with the standardised Vane Pump test; 2) a predictive test must reproduce the actual wear mechanism in the hydraulic pump and 3) be sufficiently reproducible. Earlier attempts to use a cyclic stress vane-on-flat methodology with a Falex Multispecimen machine were not satisfactory because the 2nd criterion wasn’t met: the test parameters didn’t reproduce the same wear mechanisms. In this paper, we have revisited the parameters of the cyclic stress vane-on-flat test to simulate the working conditions of a vane pump. A key feature of this approach was to fine-tune experimental conditions and specimens to accelerate wear without changing the wear mechanisms. To achieve this, we compared wear mechanisms and weight losses of the Falex MultiSpecimen vane-on- flat tester with the ones obtained from Conestoga Vickers Vane Pump tests. The outcome is a promising prescreening method that produces a reliable ranking of hydraulic fluids comparable to those of Conestoga tests, but in a significantly shorter test time, using less fluid and with additional information on the frictional behavior of the tribosystem.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.114 page 1
Prescreening hydraulic fluids for vane pumps: a ranking method
Emmanuel Georgiou*, Dirk Drees*, Michel De Bilde*, Michael Anderson**
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