Dynamic Seals for Advanced Hydraulic Systems

The purpose of this program was to identify rod seals and scrapers which would give long service life in fly-by-wire FBW flight control system actuators. This project determined a duty cycle spectrum for FBW flight control actuators. Realistic testing of rod seals and scrapers in a -65 to 275 F, 3000 psi, MIL-H-5606 fluid system identified a number of rod seals and scrapers which gave improved performance when compared to a baseline rod seal of MS28774 backupsM834611 0-ring or a MS28776M scraper. The rod seal tests evaluated backup rings, single stage, and two stage rod seals of many configurations. Scrapers were tested in an AC coarse test dust environment at 170 to 190 deg F. Principle conclusions for rod seals are that two stage unvented rod seals offer a significant reduction in leakage when compared to any single stage rod seal. With the use of a high performance backup ring, 0-rings are capable of withstanding the equivalent of 5 years service life in FBW mechanical duty cycles. Single stage rod seals with rubber in contact with the rod leak much less than those with plastic in contact with the rod. Four different two stage rod seal systems were identified which gave no measurable external leakage in tests. Five plastic and one bronze scraper were tested which allowed less transmission of contaminant to the rod seal than the MS28776M baseline. Author