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LPG - Vacuum Breaker Requirement for Pressurized Vessel
thread798-67046
msavila (Chemical) Aug 8, 2003
Does an LPG (Butanes) Pressurized Storage Sphere require a
vacuum breaker? Our existing tanks were designed with a vacuum
pressure (actually a duo-check valve) that is set to open at 1" H2O
and has a design pressure of 90 psi (tank design pressure) at
ambient conditions. I have been unable to locate a vendor that can
provide a vacuum breaker that can meet our specs. Can you help
me?
MJCronin (Mechanical) Aug 12, 2003
msavila, Do you have an ASME vessel with a code dataplate ? If
not, do you have a mfr's print with the National Board number on it
? For a few bucks, the people in Columbus OH will send to you the
design data submitted to them at the time that the vessel was
built... If you can read the dataplate, you may find the vacuum
rating on it....remember "FV" means "full vacuum protection/ What
are the dimensions of your vessel ? If the diameter is 6 feet or
less and the heads are dished, and the design pressure is 90 psig,
the chances are good that you have far more than a 1" H2o vacuum
rating. Just my thoughts.... MJC
Montemayor (Chemical) Aug 12, 2003
msavila (Chemical): Mike Cronin is giving you some great, basic
and essential advice that should go in your hip pocket for when
you're dealing with tanks and pressure vessels. You ask if a vacuum
breaker is required for Butane storage. Again, this is a basic and
elementary need that is easily resolved if you revert back to your
Thermodynamics and physical properties studies. If the tank is
going to be dedicated solely to Butane storage (saturated), then
you need to refer to the vapor pressure of Butane: Temp, oF Press,
psia 14.000 10.119 16.000 10.590 18.000 11.078 20.000 11.584 22.000
12.107 24.000 12.649 26.000 13.210 28.000 13.790 30.000 14.390
32.000 15.010 Depending on your tank's location and elevation, the
above table should tell you if you're going to generate a vacuum by
allowing the tank's contents to cool down with atmospheric winter
conditions. If you're located in Kingston, Jamaica, Port of Spain,
Trinidad or Pucallpa, Peru I wouldn't worry about needing a vacuum
breaker in a butane tank. If you're in
Page 1 of 2Chemical process engineering - LPG - Vacuum Breaker
Requirement for Pressurized Vessel
1/10/2005http://www.eng-tips.com/viewthread.cfm?qid=67046&page=26
the North Slope, you'd better have one. Normally, I would expect
to find the tank has been FV'd and I would not rest until I had the
documentation that Mike Cronin lists - especially the fabrication
drawings. You need these for inspection and as reference for all
tank-related calculations (such as the vacuum breaker).
Art Montemayor Spring, TX
msavila (Chemical) Aug 22, 2003
Hello MJCronin & Montemayor, Thank you both for your replies
to my post. I was able to dig up the fabrication drawings in our
drawing room. The vessel was built in 1969 by Chicago Bridge &
Iron Company (CB&I), and the tank was rated for -12.55 psig
vacuum. It is 62 ft in diameter, 90 psi MAWP, 135 psi test
pressure, with top thickness of 1.044" and bottom at 1 3/16". I
performed several calculations using the most extreme operating
conditions and worst case scenarios under our current operation,
and have determined that we cannot exceed the -12.55 psi vacuum
rating of the sphere. I have reviewed them with our process
engineering group here and submitted an MOC to remove the vacuum
breakers (check valves) from the sphere all together. I appreciate
your input and look forward to any other comments or suggestions
you may have. Thanks Again, Mark Avila Operations Engineer Los
Angeles Refinery ConocoPhillips
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Requirement for Pressurized Vessel
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