In collaboration with the Milwaukee School of Engineering (MSOE), seals and sealing solutions provider Hallite Seals Americas has developed and performed a test method over the past eight months to assess the amount of dirt entering a simulated hydraulic system through the rod wiper.

Rod wipers are designed to prevent dirt ingression – a major cause of inefficiency, degradation and failure in hydraulic systems – caused by the axial movement of the rod, which plunges contamination into the cylinder and, consequently, into the hydraulic system.

The test procedure entailed a hydraulic cylinder, fitted with varying rod wipers being run the equivalent of 80 000 linear feet, for a cycle time of about 24 hours, inside a dust chamber. A laser monitoring system recorded the amount of contamination of the oil throughout the entire test cycle and then analysed the statistics for comparision. Each complete test procedure took about three days.

Hallite business development manager Chuck White tells Engineering News that measuring the oil contamination was a particularly challenging aspect of the new test method. Instead of using gravimetric measurement, the MSOE devised a method to count particles and classify them according to size.

Hallite director of engineering Ryan Webster adds that ascertaining the dust-to-air ratio correctly was particularly challenging.

Prior to establishing this test method, the only existing test for rod wipers was the SAE J1195, launched in 1993 by the Society of Automotive Engineers International. White adds, however, that this test did not simulate proper boundary lubrication and did not account for typical alignment of the rod to the bore of the cylinder.

During the new performance test, the two different Hallite wipers were tested against wipers produced by two competing market-share leaders.

Based on these results, the Hallite 820 umbrella-design wipers, which have a secondary protective structure outboard of the primary wiper lip, were shown to provide the best protection, allowing for the least amount of dust ingression.

Although Hallite determined during product development that more elaborate designs were too expensive and difficult to produce, the T820 wipers are easily manufactured, Webster adds.

He tells Engineering News that the performance test was designed to show the importance of using high-quality wipers and determining which wipers have the best quality. “We knew . . . that Hallite had the best wipers; we simply needed to prove that fact through an unbiased, third-party evaluation.”