Vessel Stored Energy Limits 6

[jeffdoc]

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

 

[Duwe6]

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

 

[blacksmith37]

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.

 

[jeffdoc]

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

 

[ione]

Don’t whether it is what you’re referring to, anyway check page 83

 

[MJCronin]

Consult the February 2011 Issue of Chemical Engineering Magazine.

 

[jeffdoc]

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

 

[SNORGY]

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.

 

[Duwe6]

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

 

[GregLamberson]

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:

http://www.oil-gas-consulting.com

 

[GregLamberson]

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:

http://www.oil-gas-consulting.com

 

[C2it]

Greg,

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

What units for SD ?

Cheers

 

[btrueblood]

Dunno about you, but I'd pick miles?

 

[GregLamberson]

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

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[SNORGY]

Better late than never...

The unlock password is eng-tips for anyone inclined to modify it to suit.

Regards,

SNORGY.

 

[SNORGY]

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.