SRV is installed in the bypass line pipe to protect the piping system from the surge(Water hammer) by sudden flow change and pump sudden stop. Model SRV-PDA consists of a main valve, solenoid valve, air set, 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 exceed pressure in piping system is occurred, surge command from pressure transmitter operates the solenoid valve, and main valve is open for protect the surge (Water hammer). It’s fully opening time is less than 200 millisecond.