INTRODUCTION

  • A piston check valves are similar to lift check valves. the only difference is that piston check valves has a dashpot consisting of piston and cylinder that provides cushioning effect during operations.
  • The dashpot produces a damping effect during operation, thereby eliminating the damage caused by the frequent operation of the valve.
  • The flow of fluid through piston check valve is similar as lift check valve.
  • The construction of seat and disc for the piston check valve also same with the construction of lift check valve where the arrangement of seating is similar to a globe valve.
  • Piston check valves do not require an operation. The closing of the disc depends on the back flow and gravity whereas; the opening of the disc depends on the upward flow.
  • Piston check valve can be found in 1” to 12” size range with 150# to 900# class range.

OPERATION

  • Flow to piston check valves must always enter below the seat.
  • As the flow enters, the disc is raised within guides from the seat by the pressure of the upward flow.
  • When the flow stops or reverses, the disc is forced onto the seat of the valve by both the backflow and gravity.

APPLICATION

  • Piston check valves are used primarily in conjunction with globe and angle valves in piping systems experiencing very frequent changes in flow direction.
  • Piston Check Valves are particularly suitable for high-pressure service where velocity of flow is high.