When to use thermal relief valves

[ab123456]

How can I determine whether I need to fit thermal relief valves to pipe runs?

There is no consistency on site at the moment and each engineer has a different opinion so we are trying to settle an arguement and set up some site standards.

The lines in questions are typically 8" stainless steel and approx 50m long containing a mixed solvent waste stream

Any links would be most helpful

Thanks

 

[DSB123]

ab123456,
Thermal relief valves are normally used where a significant length of line can be "locked in" (i.e. valves at either end are shut) whereby the liquid cannot expand due to changes in temperature. You have to calculate the increase in volume of the liquid for a known increase in temperature then the increase in pressure can be calculated. If the pipe cannot sustain the resultant pressure then thermal relief must be provided.

 

[Guidoo]

Subject has been discussed on eng-tips many times. Please do a keyword search on "thermal relief". See for example thread124-83163