Soft seat design provides repeatable bubble-tight performance before and after each relief cycle.Leak-tight performance near set pressure allows higher operating pressure, resulting in increased process throughput and system optimization.Easily replaceable soft seat and seals eliminate expensive, time-consuming lapping of metal components, resulting in lower long-term maintenance costs.Externally adjustable blowdown on Types 81/83 allows precise adjustment of reseat pressure without affecting set pressure adjustment.Types 81/83 provide full lift at set pressure with no overpressure required.Minimizes possibility of freeze-up in applications involving a cryogenic or refrigerant and allows for D.O.T. applications to be set higher than Maximum Allowable Operating Pressure.Type 81P spindle design balanced against the effects of back pressure without the use of a bellows, reducing both initial purchase and associated long-term maintenance costs.Meet ASME Section VIII requirements, providing the user with third party verification of valve capacity and performance.Comply with the EC Pressure Equipment Directive 97/23/EC.