High Pressure Pneumatic Test Chamber

[stanrick]

Hello All,

My company is very interested in building a test chamber to check pressure vessels (24” dia x 10ft long) pneumatically up to 770 psi for structural integrity. After that, we would follow up the structural test with a leak test capable of detecting 10E-9 to 10E-11 cc/min. The long term goal is to test vessels up to 42"dia x 24ft in another chamber

Can anyone point me to the appropriate codes (besides ASME Section VII, UG-90, 100, 101), as well as websites and other sources info on the design and construction of such a test facility?

Thanks.

 

[eliebl]

Take a look at the pneumatic testing article in this newsletter. You will want to think a bit more about it.

http://www.absa.ca/newsletter/v07-2002/v7-iss2.pdf

EJL

 

[TGS4]

stanrick - I take it that you probably understand all of the risks associated with pneumatic tests, and want to design a "chamber" to contain the potential "projectiles" in case the pneumatic test goes wrong. Am I correct?

 

[stanrick]

Eliebl- Thanks for the link to the newsletter. It included some basis for one or two of the anecdotal pieces of info I'd heard.

TGS4- Indeed I do want to contain the projectiles. Safety is of paramount importance to me. One of the questions floating around in my head is "How thick do the walls need to be, and of what material?" I understand that this chamber and/or the (unoccupied) room it is located in would need to be capable of containing a significant explosion.

-Rick

 

[doberdorks]

Rick,

For entertainment value, you might check out

http://www.nrcan-rncan.gc.ca/mms/cerl/Photos/ibc_e.htm

Perhaps more extreme that you need though (grin).

SLH

 

[TGS4]

There is currently a proposal floating around the ASME Code Committees addressing "Impulsively Loaded Vessels". I suggest googling that term. Not sure how that deals with projectiles, though - that's another entirely different issue.

 

[gerhardl]

Test chamber could be dug down sunken in ground, open above, preferably in relatively thinly populated area, or else protected by roof. What about noise protection and controlled venting if explosions?

Reconsider and test with liquid - water or other?

 

[gerhardl]

And also below in this forum:

pneumatic testing of fuel oil tank?
thread794-212847

 

[stanrick]

Thanks one and all for your help. I believe my task at this point is to educate myself and management on the seriosness of this undertaking, and to roughly sketch out the scope of work involved. They can decide if they really want to spend the resources to pursue it further. The guidance you provided should get me started.

I may be posting further questions as my knowledge increases.

Rick

 

[doberdorks]

A little more searching brings up

http://www.canpressmetalfab.com/files/home.html

click on the left hand side
"explosion chambers"

Looks like it IS quite the cadillac.

SLH

 

[SMF1964]

The consequences of a burst are difficult to anticipate. A piece of shrapnel can ricochet about in unpredictable ways so I wonder as to the wisdom of pneumatic testing when a hydro test (or some other fluid) is an option. Past issues of the Journal of Failure Analysis and Prevention show case histories of SCUBA tank failures during refill operations that are violent.

 

[stanrick]

My understanding of the major factor driving toward pneumatic testing is the unacceptability of even traces of hydrostatic fluid residue in the vessel. Also a factor is the time required to fill a vessel with fluid through a small opening. Finally there is the cost of the fluid and the environmental issues of dealing with any fluid that must be disposed of.

I tend to believe anything is possible IF you're willing to devote sufficient resources to the soulution. It appears to me that on the one hand there is the safety of performing a pneumatic test on a large vessel. I want to be able to sleep at night, and so do not wish to minimize the importance of this. On the other hand there are the issues of the time and expense of dealing with a hydro test. In the end, it comes down to whether the resources (time, money) needed to perform a safe pneumatic test are less than the resources needed to perform a safe hydro test. Compounding this is the desire to do something that everyone says can't (or maybe shouldn't) be done.

There is an assumption here at my organization that the resources needed for an acceptable hydro test are far greater than those needed for an acceptable pneumatic test.

Perhaps the first question to answer is: "What would it take to hydro test a vessel to 910 psi for R410A refrigerant applications, versus pneumatic to 770 psi?"

I now think I should start new threads, here and on the HVACR forums, with this as the question.

 

[eliebl]

Am I correct in assuming that your organization is putting a price on safety? I know that this may be an oversimplification of the problem but maybe add a couple of extra nozzles (2" or 4") for the filling and draining of water. Given the pressurization steps for the pneumatic test I don't see that there would be much of a time savings.

Regards,
EJL

 

[zeusfaber]

A Gravel Gertie might be overkill, but would probably catch all the bits.

A.

 

[JStephen]

From long ago, I seem to recall that the kinetic energy of a bullet is in the neighborhood that the paper referenced gives for a whole pound of smokeless powder. I think they're off by a couple of orders of magnitude on the smokeless and blackpowder energy.

 

[stanrick]

EJL,

Thanks for your input. Your suggestion of extra nozzles for filling/draining is just the sort of input I need. Essentially, I wish I could have a brainstorming session with a bunch of experienced engineers. Alas, I seem to be the only engineer on this controversial project, hence I come to this forum.

Regarding putting a price on safety, I'm sorry if my ramblings seem to put too much emphasis on this aspect. I am aware that trying to equate dollars with the health and well being of individuals has been tried without success by more qualified persons than myself. That being said, risk is inherent in any project - even a project like my getting out of bed and driving to work. I do my best to keep the risks reasonable, and respect the fact that what seems reasonable to me may not seem so to everyone. This is the other reason why I'm glad to have this forum available: I know what groupthink is, and I know my job can be a hermetically sealed microcosm.

I thank you for helping me to stay honest and aware of my motivations.

-Rick

 

[eliebl]

Rick,

Having worked for a regulatory organization, safety is the concern without taking into account the dollar value. Being charged with the duty of safety by the government they must take that stand. If a variance to a requirement is to be issued, there had better be reasons other than cost involved.

More to your problem, what sort of contaminants can be tolerated in the R410A refrigerent? Have you looked into getting another organization to perform the cleaning after the hydrotest? I was involved in the estimate of a vessel which was to eventually contain a pyrophoric (reacts with water - term may be incorrect) substance where residual water was bad. There was a place that could adequately clean the vessel and then dry it. I know this may seem costly but it is then someone's problem other than yours. It might be worthwhile to look at what a test chamber would cost, and compare it to the cost of someone doing the cleaning.

Regards,
EJL

 

[eliebl]

Rick,

I spent too much time thinking about this but what may want to consider is the NDT required for the category D welds. Please see UW-50 for this requirement.

If a vessel to to be pneumatically tested there is also a provision that no longer applies. UG-20(f) cannot be used as the vessel does not comply with UG-20(f)(2).

Just a few more things to think about.

Regards,
EJL