Problem:

How to account for a thrust load from a :

> Pressure Safety Valve (PSV)

> pressure relief valve (PRV)

> Safety valve (SV)

> Relief Valve (RV)

>etc..

Solution:

When a safety valve exceeds its preset limits, the valve automatically opens to relieve the internal pipeline / vessel pressure. The sudden release of discharging pressure from a valve would be subjected to a pressure and momentum thrust load. The relief event is dependent on the type of vent piping either:

> Open discharge to atmosphere- with non-integral relief and vent piping

> Open discharge to atmosphere- with integral relief and vent piping

> Closed discharge to manifold - with integral relief and vent piping

There are 2 modeling approaches: static thrust load or dynamic thrust load. 

Static Thrust load:

Step #1:

Manually calculate relief valve thrust load.

Step #2:

Insert Concentrated force at the vent discharge node point in the proper direction. Suggest to set "Load case to combine with Force" to U1..Un. This will allow the user to easily evaluate code and non-code combinations as the operating conditions where a relief valve event was applying it's thrust load onto the piping system.

Dynamic Thrust load:

AutoPIPE has a tool to automatically calculate the thrust force and generate the time history files required to perform a dynamic time history analysis. This tool can only be used for STEAM systems. For complete step by step instructions see the following AutoPIPE help section:
Help > Contents> Contents Tab> Modeling Approaches> Example Systems> Steam Relief Example. The model can be found in AutoPIPE's Example systems folder. 

Otherwise, for other type of gas / liquids use another the tool to create the time history files and update the thrust force accordingly. Also not that there is an official AutoPIPE training class available on this subject. Contact your account sales person for training options available. 

Since these thrust loads are dynamic in nature, they can be analyzed more accurately using the AutoPIPE time-history solution than using the static thrust load approach mentioned above.  The Occasional stress ratio for the dynamic load would be slightly higher than that for the Statically applied load. This is a result of the dynamic affect being included and no DLF applied to the static load before applying it. 

See Also

Modeling Approaches in AutoPIPE

Bentley AutoPIPE