The Type P125 trip stop pilot is used in conjunction with a Spence main valve. This combination is known as a trip stop valve. Type P125 is a manually resettable trip pilot that, once “tripped”, results in the closing of a Spence main valve; therefore preventing further overpressure of the downstream system. The trip pilot is set at a pressure slightly greater than the desired delivery pressure. This setting procedure is completed at the factory before the pilot is shipped.