Safety Valves

Typical safety valve installations calculated by AutoPIPE

Safety Valves Discharge

Safety valve tripping is one of the most common transient flow phenomena that the stress analyst has to deal with.

The most widely used method, in the case of steam, to determine the reaction forces in the pipe is to follow Appendix II of ASME B31.1.

AutoPIPE integrates the ASME B31.1 formulas and prepares the force profile for the valve and discharge. Forces in discharge pipe direction changes, whether open or closed discharge, can be calculated using AutoPIPE's fluid transient calculation.


The AutoPIPE Dialog for Calculating Safety Valve Discharge by Time History requires the following data:

  • Mass flow.
  • Enthalpy of steam.
  • Specific heat ratio.
  • Steam quality.
  • Valve openning time.
  • Time the valve is kept open.
  • Back pressure, if discharging into a closed system.

With these data the program prepares the histogram of the safety valve trip.

Safety Valve Trip Force Calculation Dialog.
Safety Valve graphic results


When reviewing the results it is important to take into account that displacements are absolute, so they should also be considered in the opposite direction.

The verification of stress is carried out according to the combinations of the piping code.