pneumatic test ?
pneumatic test ?
(OP)
What is the acceptable energy store in my system for a nitrogen test on a used (but empty) HTF line of 1 1/2'' dia, 3000 ft.
I have read 50000 (psig x cuft)
Is it alright ? I need reference
My client would like to do it in one run.
Thanks,
vladimir99
I have read 50000 (psig x cuft)
Is it alright ? I need reference
My client would like to do it in one run.
Thanks,
vladimir99





RE: pneumatic test ?
Thanks
vladimir99
RE: pneumatic test ?
The NASA Glenn Research Centre used to publish salient information regarding safe stored energy and restricted distances involved with pneumatic testing, but it's hard to get that data or their methodology from their website now.
One thing that I did several years ago when I didn't have that data was calculate the total stored energy, divide it by the total mass of the pipe, assume instantaneous conversion of that energy per unit mass from potential energy to kinetic energy, assume a 45-degree launch angle into still air with an average ballistic number, and thereby calculate how far the pieces would fly if it blew up. Anything farther than 50 metres meant too much stored energy.
NASA Glenn's approach was to assume a 0.5 psi blast pressure (shatters windows) and back their restricted distance data and stored energy limits out from that.
Regards,
SNORGY.
RE: pneumatic test ?
So, at first glance, 50000 in terms of psi x ft^3 seems to be pretty reasonable to me.
Regards,
SNORGY.
RE: pneumatic test ?
As to the "stored energy" discussion, most of it assumes that there is a point-failure and that the entire stored energy in a long line is dissipated instantaneously. What poppycock. A failed line at a point will release the energy in near proximity to the failure. The rest of the gas in the line will start rushing toward the opening (just as if you had opened a valve) and will make a lot of noise, but will not participate in the blast zone. Pneumatic tests require careful Engineering design, but the MegaTonne explosions that people calculate are so much nonsense--the stored energy is simply not in the proximity of the blast zone. It is like saying that if you light a firecracker, every grain of gunpowder in the world will sympathetically detonate.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: pneumatic test ?
There is brief mention of a similar calculation or guideline in the ES&H Manual for Jefferson Labs ...
http://www.jlab.org/ehs/ehsmanual/6151T4.htm
RE: pneumatic test ?
I also realized and wrestled with the fact that you cannot concentrate all that energy into one local failure site; hence my energy per unit mass rationalization. But even then, there is no credit taken for fracture toughness and the energy lost due to fragmentation (tear-away energy, if you will).
That said...in my jurisdiction, the local Regulatory Body requires the application of the NASA-Glenn Research Centre methodology towards establishing restricted distances and safe work plans for pneumatic tests.
Regards,
SNORGY.
RE: pneumatic test ?
I think I saw your number as well; might have been Syncrude maybe, circa 1986? But I seem to recall a plot like PV^3/1000...I forget what the abscissa was. I recall vaguely that if you were below the curve, you were safe; above the curve, they wouldn't let you do a pneumatic test.
Regards,
SNORGY.
RE: pneumatic test ?
RE: pneumatic test ?