Thermal Relief Spacing

[PMarinshaw]

Does anyone know of an existing "rule of thumb" for spacing thermal reliefs in a pipeline (every 1000' etc.) due to solar radiation? I know there are many variables to consider such as pipe size, product contained, elevation changes, where in the world the pipeline is, P&T, etc. I'm not looking rer anything scientific.

 

[rutherford703]

50 meters with liquid volume no more than 1 m3

 

[BigInch]

You must be able to relieve the expanded volume. Spacing is therefore a function of expanded volume, which is a function of blocked-in volume and temperature change. Normal practice as I know it is to calculate the volume that can be blocked-in, such as volume actually between adjacent block valves, calculate the expanded volume at the high temperature and the time to raise to that temperature, then size the valve for [Δ]V/[Δ]t.

Trying to size multiple relief valves in any one blocked-in segment spaced a certain distance apart has the potential to complicate the problem considerably, as it becomes a problem with possible multiple flow paths being set up within the same pipe, even if you don't consider elevation differences between relief points, or a nonuniformtemperature distribution along the pipe segment.

What would you be doing, if you knew that you could not fail?

 

[bimr]

What is the product in the pipeline?

 

[RaRo]

Old thread with info

For liquid that could not vaporize given the conditions and would not flash when relieved, we considered 250 liters as the maximum blocked-in liquid volume in pipes exposed to sunlight before installing a thermal relief valve
We had a liquid expansion coefficient limit to exclude some liquids from that, but I can't find it right now.

 

[BigInch]

That won't get you very far with a 36" pipe.

What would you be doing, if you knew that you could not fail?