B31.3 and Deflagration

[BarnesMobile]

New to Eng-Tips and a newish Engineer here. Hoping for some input.

I'm working on conforming our design of a liquid nuclear waste sampler system to ASME B31.3 We have been asked to address potential deflagration due to hydrogen build.

Nothing unusual, but... The project manager is asking me to apply the calculated deflagration pressure to the B31.3 design requirements. I can't see anywhere in the code or elsewhere that I should do this. Perhaps I could see this listed as an occasional load under B31.3, but even then that doesn't make sense to me. As far as I can tell I should apply the maximum design pressure of the system, and nothing more.

Is this guy on the right track? Or am I just a newb that doesn't know what I'm talking about?

-Jon Barnes

 

[BigInch]

I don't think B31.3 by itself would address that situation in a cost effective manner. I haven't looked at this before, but as far as I know it would have to be addressed under transient allowable conditions with a maximum allowable stress still probably well under what the pipe would could actually withstand under those conditions, assuming they would be momentary in nature, rather than lasting even for 15 minutes or so.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MJCronin]

Barnes&Noble....

Look at the definition of Design Pressure in B31.1 and B31.3.

It is to be not less than the maximum SUSTAINED operating pressure for the system.

Transient pressures are also discussed in B31.1 ( and B31.3...I think)

-MJC

 

[ApC2Kp]

BarnesMobile,

It has been more than a few years since dealing with deflagration events in piping, so I googled and got 12,000 hits from 'deflagration detonation pipe' and a more focused 8,000 hits with 'deflagration detonation relief'.

There are listed publications from Protectoseal, Groth, Enardo, and Protego, among others. There is even an article that discusses possible hydrogen deflagration inside a nuclear containment building - might be just like your situation.

Your sampler system is probably expected to keep a possible deflagration inside the piping, and not allow the flame of deflagration to propagate to environment (reactor building) with more grievious consequences. The pressures from the deflagration heat of combustion would be applied as a type of Occasional load, above and beyond the system operating pressures.

 

[psafety]

Walk softly with hydrogen, with a Kg of 550 bar-m-sec, its is known to go from deflagration to detonation. NFPA 68 & 69 are your friend.

 

[XELR8]

Hey Folks,

There is no such thing as deflagration pressure. Deflagration is the propagation of a combustion zone at a velocity that is less than the speed of sound in a unreacted medium.

There are pressures associated with deflagration and are explained in NFPA 68. For the record, the following pressures are listed from smallest to largest in an enclosure, Pstat, Pred, Pdesign (this is the B31.3 one you are working with), Pmax (this one is above Pdesign and can have an explosive effect). Dont forget, asme give a 33% increase in allowable stress for the design of a one time occurance.