How much seat leakage can I expect from a pressure relief valve?
Pressure relief valves come in a variety of seat configurations. In normal operation, most valves with metal to metal seats are allowed a certain amount of leakage past the seats. American Petroleum Institute Standard 527, Seat Tightness of Pressure Relief Valves defines the most widely used method for testing seat tightness as well as the leakage rates. The rates are defined by pressure category and valve size and range from 20 to 100 bubbles per minute. The tests are conducted at 90 % of set pressure. Some valves like our 2600 and 2700 series can be supplied with optional “O” ring seats which allow for zero leakage at 90 % of set pressure. The 3800 Series pilot operated valve is supplied as standard with “O” ring seats and can safely handle operating pressures up to 90 % of set pressure with no leakage.
