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Vessel Stored Energy Limits

Vessel Stored Energy Limits

(OP)
Looking for a good industry standard reference for calculating stored energy in pressure systems and determining safe working distances?

RE: Vessel Stored Energy Limits

Me too.  Standards for Pneumatic testing don't exist.  What do our fellow engineers consider adequate safety zones, please?

RE: Vessel Stored Energy Limits

The next county should be safe. Anecdotally, I have seen a few tons of 2" thick head (about 8ft dia) break loose, tearing off 12" pipe connections, go 100' up and land 300' away; due to 300 psi nitrogen. You add explosions or detonations and it seems pretty difficult to predict a "safe" zone.  

RE: Vessel Stored Energy Limits

(OP)
I found ASME PCC-2-2008 Repair of Pressure Equipment & Piping. In the mandatory appendix is a method for calculating stored energy & safe distance (pg. 197-198). This was sufficient for what I was doing, but I have heard there is a NASA document that addresses this issue, if any one has that reference, please share. Thanks for the comments :)

RE: Vessel Stored Energy Limits

Consult the February 2011 Issue of Chemical Engineering Magazine.

   

RE: Vessel Stored Energy Limits

(OP)
@ione: Thanks, I like to use NASA specs when working with NASA, this was a great help :)

RE: Vessel Stored Energy Limits

I wrote something that I think is pretty much exactly what you are looking for.  It is based on the NASA-Glenn approach, which used to be in the public domain via their website, but is tough to find now.  I even wrote a little spreadsheet that calculates the stored energy levels and safe working distances for you.  If you want, I will make it generic and upload it.  

Regards,

SNORGY.

RE: Vessel Stored Energy Limits

snorgy, by all means.  There should be a number of us that would use this spreadsheet.  I will, for sure.

RE: Vessel Stored Energy Limits

Do a stored energy calculation by:

E = (PV / k-1) x (1-(Patm / P)k-1/k, where:

E = Energy in Joules
P = Absolute pressure in Pascals
V = Test volume in M3
Patm = Atmospheric pressure in Pascals
k = Ratio of specific heat of air


Then convert to TNT:

TNTlb = E x 4.8 x 10-7

The safe distance can then be calculated by:  SD = 15 (TNTlb).5

I use this for calculating safe working distance for all pnuematic tests.  There are similar for hydrotests, but the stored energy is obviously a whole lot less.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
 

RE: Vessel Stored Energy Limits

Ooopps, should have been:

E = (PV / k-1) x (1-(Patm / P)^k-1/k,

and

SD = 15 (TNTlb)^.5

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
 

RE: Vessel Stored Energy Limits

Greg,

I'm assuming that TNTlb is equivalent weight in pounds.

What units for SD ?

Cheers
 

RE: Vessel Stored Energy Limits

Dunno about you, but I'd pick miles? :)

RE: Vessel Stored Energy Limits

Correct on the TNTlb.  SD = Safe Distance = meters, sorry should have specified.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
 

RE: Vessel Stored Energy Limits

If I take the liberty of pirating Greg Lamberson's posted equations, I obtain the revisions per the attached link.  The agreement in results is pretty good based on the cases I ran.  The differences are probably because the curve fit correlation that I used for the NASA-Glenn curve probably could be improved a bit.

Greg Lamberson's equations may be better than mine.

Regards,

SNORGY.

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