Relief Valve or Bursting Disc Tailpipes to Atmosphere (Open Systems)

•Ensure these are adequately restrained.

•Sometimes the discharge direction is changed from vertical to horizontal at site, so the restraints shall be designed to suit both a horizontal and vertical discharge; if this is not possible, add this note to the stress iso “valid for vertical discharge only” or “valid for horizontal discharge only”, as appropriate.

•Loadings due to flow at the open end shall include a dynamic load factor = 2.0 i.e. the shock load.

•Minimum natural frequency shall be 5.0Hz, and should be above 8.0Hz unless impossible.

•Long runs of pipe shall be axially restrained and this restraint shall be designed for the shock load. “Long” should be taken as 40 x pipe outside diameter, approximately.

Relief Valve or Bursting Disc Tailpipes to Flare or Vent Header (Closed Systems)

•Do not model forces at relief valve, since the out-of-balance duration is very short at this location.

•Minimum natural frequency shall be 5.0Hz, and should be above 8.0Hz unless impossible.

•Long runs of pipe shall be axially restrained and this restraint shall be designed for the shock load. “Long” should be taken as 40 x pipe outside diameter, approximately.

•If the header is thin-wall pipe, a reinforcing pad shall be called up; even if the pipe stress analysis or pressure calculation shows that this is not required.

•Acoustic fatigue of discharge system should be investigated where the RV set pressure exceeds a nominal value of 5 MPa and the pipe is thinner than standard wall thickness.

•RV outlet lines to silencers are considered closed systems if the silencer is anchored and there is no sliding joint at the nozzle.