Investigation on the sealing performance of polymers at ultra high pressures

Abstract

In this paper, the parameters affecting the sealing life of UHMWPE and PTFE in ultra high pressure systems were investigated. A life test system was designed and manufactured in which different parameters can be tested in the sealing construction. The life test system consists of two hydraulic pressure intensifiers, and a hydraulic and electronic control unit. The effects of the extrusion gap, piston rod material and surface roughness, in addition to the material, geometry and number of the sealing elements, on the life of the sealing members were investigated. Two levels were determined for each parameter, and experiments were carried out at a pressure of 450 MPa according to a Taguchi L8 orthogonal experimental design. Pressure intensifiers were operated reciprocatively, thus allowing to perform two tests simultaneously, saving time. Working cycles of the pressure intensifiers were measured. Each experiment continued until the seals were damaged, and a critical leakage rate occurred at the pressure intensifiers. ANOVA was applied to the experimental results. According to the results, the most significant parameter affecting the sealing life is the extrusion gap with a rate of 77%, followed by the piston rod surface roughness with a rate of 13%, and the piston rod material with a rate of 4%. The effects of the remaining parameters on the sealing life are more limited. The results obtained will contribute to the industrial design of sealing structures for ultra-high pressures.