Paper: Performance mapping of rectangular-rounded hydraulic reciprocating seals to minimize leakage, frictional work and and abrasive wear with the aid of a duty parameter.

Author: George K. Nikas

Published in: Tribology International, 2023, 179, 108191

Abstract

The performance of rectangular-rounded, elastomeric, hydraulic rod seals for reciprocating motion is theoretically evaluated in terms of the mass leakage per cycle, frictional work and abrasive wear. Maximal sealing performance is admitted when the leakage per cycle is nullified in conjunction with having minimal frictional work and minimal abrasive wear. This study proposes a method to construct sealing performance maps based on a newly defined duty parameter. The maps are subsequently taken advantage of to select optimal values of important parameters such as the sealed pressure, the stroking velocity and the edge radius of curvature of a seal for maximal performance. The selection process is automated by an objective function, which combines the effects of friction and abrasive wear under a leakage constraint. This could allow educated adjustments to a sealing system in real time, as for example, to compensate for the change of a sealís edge radius as a result of abrasion, using either condition monitoring or a predictive wear model. A linear relation between the average film thickness of a sealing contact and the new duty parameter is also established, allowing for a semi-analytical estimation of the film thickness for any lubricating conditions.

Highlights

A figure from this work

A real rectangular-rounded hydraulic rod seal for reciprocating motion has been analysed in the article using the author's in-house developed and experimentally validated software ROSEAL, which accounts for more than 45 design, material, dimensional and operating parameters. A parametric study on the effects of the sealed pressure, the stroking velocity and the edge (corner) radius of curvature of the seal was conducted with data for about 750 of the aforementioned triplets, such that sealing performance was thoroughly mapped. The below figure is a contour plot of the mass leakage per cycle (Qc) of the seal for the proposed new duty parameter N (Nin for instrokes and Nout for outstrokes). The dashed boundary separates the green area of zero leakage from the blue area where there is a leak at the end of every cycle. The target is to achieve zero leakage without starving the sealing contact of fluid during instrokes and so without causing increased abrasion. Optimum values for the duty parameters Nin and Nout for minimizing frictional work and abrasive wear with the aid of an objective function proposed in the paper have been established in the analysis as those corresponding to lambda ratio (λ) of 1 and 3, where lambda is the ratio of the average film thickness of the flat portion of the sealing contact over the composite RMS (root mean square) roughness. Given those constraints, optimal working conditions are identified as those corresponding to either point E or F in the figure, depending on the value of c, where c 𝜖 [0, 1] is a weighting coefficient using the previously mentioned objective function to allow selective prioritization by the researcher to either the frictional work or the abrasive wear of the seal. In case there are constraints in the sealing system that preclude operating at either point E or F, a compromise can be accepted by selecting any point of area EFGA. Subsequently, having selected optimal values for Nin and Nout, input data corresponding to Nin and Nout can be selected to complete the optimization process.

Rod seal - performance mapping

Contour plot of the mass leakage per cycle (Qc) of the seal, using the duty parameters for instroke and outstroke.

Homepage of Dr Nikas