Safety: overpressure of vessel leading to its destruction 2

[Nanimo]

Hello,

I'm working on a safety report for an experiment I'll be working for. It involve pressure vessel and pipes under pressure that will be heated. For the safety clearance, I need to demonstrate the effect of a "worst case scenario", that would be
1) Overpressure of the pressure vessel (propane tank) leading to it's destruction
2) Overpressure of the pipes (stainless steel and ceramics) leading to its destruction.

I have other worst case scenario but are not relevant to this forum / are already handled.

As I'm quite new to this stuff, I was wondering if you had paper / handbook that could help me to put numbers or demonstrate the effect that would occur in case of these two scenarios? So I can then size the eventual protection system for the experiment.

PS: I mentionned I'm using propane but I'm not interested in the part when propane and air is mixed, that has been handled. It's really the overpressure aftermath that I'm investigating.

 

[stanweld]

Assuming that the pressure/temperature is such that the liquid propane will flash during rupture, you should treat the test as a pneumatic test and use NASA guidelines to determine the minimum distance at which personnel should be stationed for safety. And if so, why not use air or nitrogen for the test? Furthermore, if you are testing to rupture, why not use water?

 

[Nanimo]

Hi Stanweld,

Thanks for your answer. I've been reading a few things about the subject, and am working with "Workbook for predicting pressure wave and fragments effect of exploding propellant tanks and gas storage vessels". This one seems to have some good things for me.

The purpose of the test is not to go to rupture, but I have to show that in the "worst case scenario" everything has been made to ensure security of personnel.

 

[stanweld]

The stored energy of a gas containing vessel/closed pipe system is a function of Pressue X Volume. In english units:
E = 360PV{1-(14.7/P)} to the power of 0.286
Presure is in PSI, Volume is in cubic feet.
1 million ft-lbs is approximately = 1/2 lb of TNT.

NASA has developed safe distance equations/curves to be used during pneumatic testing based on the instantaneous release of stored energy, assuming possible rupture at a test pressure. I would advise using it to predict safe distances without additional blast protection measures.

 

[Nanimo]

Do you know the name/link of the paper presenting these equations?

When looking in google, I find lot of different things but nothing that straightforward.

 

[stanweld]

Mark's Mechanical Engineers Handbook
Berkeley Laboratories, Health and Safety Manual - Stored Energy of a Pressurized Gas Vessel.

 

[austsa]

Nanimo,
Google NASA Glenn Safety Manual. Contains a lot of info that may be relevant to you. Stanweld has already provided the formula.
Ensure there is no electrical instruments (including mobile phones) close to the vessel. Also suggest that you prevent static charge build up. The NASA formula only takes pressure energy into account. It does not account for propane's chemical energy (in the case of an explosion).
Don't rush into this test without doing your homework thoroughly.
austsa

 

[davefitz]

I am surprised that one would be putting on paper such a predicted failure. It would seem that there are so many availbable means to prevent a "worst case" from happening. A rutpture disc would cost less than the engineering study you are proposing.

 

[vpl]

Has anyone asked if this is a student assignment?


Patricia Lougheed

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[Nanimo]

Thanks for the info. I also used "Workbook for predicting pressure wave and fragment effects of exploding propellant tanks and gas storage vessels" (NASA, 1977).