SRV is installed in the bypass pipeline to protect the piping system from the surge(Water hammer) by sudden flow change and sudden pump stop. Model SRV-PDA consists of a main valve, solenoid valve and air set, 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 pressure signal from pressure transmitter operates the solenoid valve, and main valve is opened to protect the surge (water hammer). Full opening time is less than 200 millisecond.