5 replies to this topic

[bwstone]

Does anyone know where to find out how to calculate the hydrostatic shut-in pressure. For example if I had a section of pipe that was liquid full and blocked in at both ends, based on the type of fluid in the pipe what would the change in pressure be if the temperature rose 100 F?

Thanks for your help.

[pleckner]

First to answer your question:

Try these articles:

1. "Forestall Pipe Bursts", D.C. Copenhaver, L.A. Coppari, S. G. Rochelle, Chemical Engineering Magazine, January 2001

2. "Save Pipes from Bursting with a Compensator", J. Boteler, D. Clucas, Chemical Engineering Magazine, December 1999

3. "Soak up Surges in Liquid Systems", P. Jennings, J. Boteler, Chemical Engineering Magazine, July 2001

4. "Decide Whether to Use Thermal Relief Valves", F. Bravo, B.D. Beatty, Chemical Engineering Magazine, December 1993

5. "Thermally Blocked-In Liquids", E.C. Valdes, K.J. Svoboda, Chemical Engineering Magazine, September 1985

Be warned. If your differential calculus is weak, you may have a hard time with these.

Now, to possibly avoid a world of pain, please state what your problem or intentions really are? Is this an academic exercise or some real world problem? If the latter, please give some details as to what you are trying to accomplish. You may not need the calculations at all.

[bwstone]

This is a real world problem. We have a 1" sch 40 carbon steel pipe that contains Tetrahydrofuran. The pipe is blocked in on both ends. One end is closed with at floating ball valve and the other end has a flapper type check valve. Recently a filter housing in the line ruptured. My thought is that the rupture was caused by hydrostaic pressure buildup. Other people feel that it was a manufactures defect, but the housing had been in service for more than one year. Normal operating pressure in the line is about 55 psig. It is a 150# flanged system.

Any thoughts?


Thanks

[pleckner]

Yes. If the filter could be blocked-in, it should have had a relief valve on it in the first place. But the easy solution is to install a simple 3/4" x 1" thermal relief valve. With a liquid full pipe, the valve will basically hic-cup some liquid out and problem solved. The valve discharge can be piped either to grade (check with environmental authorities) or just jump over the isolation. If you can't find some place to put the relieving liquid (which again will be very, very small), you can put in one of the devices discussed in the articles I referenced in my last post. You might also pipe it to a waste drum.

For possible relief valves, contact Farris Engineering (Curtis-Wright, parent company website www.cwfc.com).

[mbeychok]

I totally agree with Phil Leckner's response. When I worked in Fluor-Daniels' process design group, it was standard practice to install small thermal relief valves on any line which could be blocked in.

Milton Beychok
(Visit me at www.air-dispersion.com)