Normally, the oil film discharged with the piston rod on the forward stroke back-pumps to the cylinder on the return stroke. However, critical operating conditions may generate a pressure imbalance between seals, such as a fast-forward stroke and a slow return; with long-stroke cylinders; and when the primary sealing edge is damaged. The resulting excessive pressure buildup can damage seals and lead to premature failure.
The Stepseal V contains an integrated nonreturn valve that prevents excessive pressure buildup. If pressure between the primary and secondary seals exceeds preset limits, a relief channel opens and reduces the interface sealing pressure. After ventilating, the channel automatically closes. The rod and piston seals are made of Turcon and Zurcon, offering good slide and wear characteristics, and they fit DIN/ISO 7425/2 grooves. Typical applications include injection-molding machines, hydraulic presses, and excavators.
Trelleborg Sealing Solutions, 3410 Meyer Rd., Ft. Wayne, IN 46803, (260) 749-6781, tss.trelleborg.com