Volume of Nitrogen needed for boiler hydro
Volume of Nitrogen needed for boiler hydro
(OP)
My plant would like to hydro the boiler after an outage with extensive tube repairs and is throwing around the idea of using nitrogen instead of water. I have the volumes of water needed for each section, but am not sure how to convert this into the volume of nitrogen needed to perform the hydro at 1500 psi (not NOP).
Can anyone help me figure this out?
One example is the superheater section holds 9531 ft3 or 71,292 gallons of water.
Thank you
Can anyone help me figure this out?
One example is the superheater section holds 9531 ft3 or 71,292 gallons of water.
Thank you





RE: Volume of Nitrogen needed for boiler hydro
RE: Volume of Nitrogen needed for boiler hydro
Regards
StoneCold
RE: Volume of Nitrogen needed for boiler hydro
I would bet this is in the hundreds of tons of TNT.
Don't even consider it.
RE: Volume of Nitrogen needed for boiler hydro
I like water.
Regards,
SNORGY.
RE: Volume of Nitrogen needed for boiler hydro
Out of curiosity, how is steam in the boiler when online less dangerous than Nitrogen while offline? The compressibility factor is about 10% more, but steam is still a pretty big energy source at 1000 F and 2500 psig.
RE: Volume of Nitrogen needed for boiler hydro
There have been some notable equipment failures during pneumatic testing. I've investigated a few myself. Every one that I've investigated or read a competent engineering post-appraisal (as opposed to an hysterical "news" report) was caused by either an improper procedure or by improperly executing a procedure. Usually the problem was either that the gas was very cold or the ambient temperature was very cold. Either of these conditions can easily lead to brittle failure if you change pressure too rapidly.
Not being able to calculate the volume of nitrogen you need does not bode well for your being able to write a competent procedure, but the volume you need (in SCF) is the empty volume (your hydro volume) times test density divided by the density at standard conditions. Since nitrogen is approximately an ideal gas, if you deliver the nitrogen at 60F then everything excepte pressure in the density calculation cancels and the equation is V(SCF)=V(empty)*P(test)/P(std).
On my web page under "samples" there is a document describing the safety considerations of testing. You might want to take a look at it before you go a lot further.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: Volume of Nitrogen needed for boiler hydro
You are correct. The calculation approach was based on the NASA Glenn Research Centre methodology, which our (up here) regulatory authority has dictated is the approach to be followed.
That aside, at the purely engineer-to-engineer level, I agree with you. I myself have tried to rationalize the amount of energy actually available to launch a fragment of steel into the atmosphere, once you deduct the energy stored at a location remote from the point of failure, and again after you further deduct the energy lost in the "tear-away" effect as the material breaks apart from what it was connected to / part of. You are right: nowhere near *all* of that energy can be concentrated for release at the point of failure. I have also pneumatically tested steam-methane reformer furnaces, PSA Units, big towers...safely...
In this instance, the OP has described that what is to be tested has been fraught with "extensive tube repairs". So, I do not think that inspires a lot of confidence. In this instance, I still prefer water.
Regards,
SNORGY.
RE: Volume of Nitrogen needed for boiler hydro
http://www.discity.com/kc135/
RE: Volume of Nitrogen needed for boiler hydro
you are correct.
Since, in reality, there is no hydro test requirement and in fact there is only a leak test required and the pneumatic testing requires a lower test pressure.
I always test slowly with stop points to allow checking for leaks when using nitrogen