9100 Series Model 20 Features Auto Seat Technology Consistent Set Pressures allowing repeatable uses without repair or resetting. Open, Close, Seat and Seal. Fully guided disk keeps the disk properly aligned, opening and closing, helping to reseat the valve. Mechanical Stop prevents wear on parts and controls valve lift. Low rated and fully guided spring allows for more consistent set pressures from pop to pop. Pop Action relief allows valve to go to full lift at set pressure. Helps with DOT regulated applications. Built in accordance with the requirements of ASME Boiler and Pressure Vessel Code. Sec. VIII Div 1. Non-rising stems allowing valves to be installed in small areas.