SRV is installed in the place that require fast responding performance to protect the piping system from the surge(water hammer) by sudden flow change and pump sudden stop. Model SRV-PH consists of a main valve, solenoid valve, and N2 bottle, which is completely assembled and tested as a unit and ready for field installation. Main Valve is closed tightly when normal operation is in state. When a exceeding pressure in piping system is occurred, surge command from pressure transmitter operates the solenoid valve, and main valve is opened to protect the surge (water hammer). Full opening time is less than 100 millisecond.