isothermal compressibility coefficient

[Pepijn1976]

Hello,

According to API 521 I'm trying to calculate if it is neccesary to install a thermal relief valve on a line that can be blocked in.
The line is made of carbon steel so I found the linear expansion coefficient and modulus of elasticity.
But I can't find any figures for the isothermal compressibility coefficient (don't have Lange's Handbook).
Does anyone have a figure for heavy nafta? Or, can tell me how to calculate this coefficient via API 521
API 521 gives an equation (5) on page 35: x= 1/v1*(v1-v2/(p2-p1).
v1 and v2 are specific volume = 1/density @ T. If I'm correct this value will always be negative (for expansion of a liquid by temperature).
What should I take for p1 and p2: I thought p1= initial pressure at start of blocked line and p2=pressure at max temperature due to solar heating (70°C).

Can someone help me on this?

Thanks in advance!

 

[Latexman]

Here's another viewpoint on the subject I refer to occaisionally:

thread124-171158

Good luck,
Latexman

 

[don1980]

Personally, I don't see any value in doing this calculation. I'm open minded, so maybe I can learn something here.

If the piping is truly liquid filled, or can be liquid filled, then I consider overpressure protection to be needed, by default, when the line can be blocked in and any of the following situations are true:
1) fluid temp is < 140F (60C)and especially if the fluid is ambient or below ambient
2) pipe is heat traced
3) pipe fluid can be heated by process equipment

When any of these are true, then I think one can jump to the conclusion that overpressure is a credible risk, and there's no value in calculating the theoritical max pressure that can develop.

If you think I'm off in the weeds, then I welcome your comments.

 

[zdas04]

don,
If you're in the weeds, I'm there with you. I would add 4) if any part of the piping is exposed to sunshine.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.