... need two hydraulic seals (double acting), one for each of the directions.8) The life of hydraulic seals is dependent on many factors including ... , USI, UPI, ODI, IDI, OSI, ISI, SPG, LBH, LBI Engineering machinery appropriative seal:SPGW, SPG, SPGO, OUHR, OSI, OUY, HBY, HBTS ...