Allowable Stress for Steam Blow Piping
Allowable Stress for Steam Blow Piping
(OP)
Hi all,
How can I get (and maybe raise) the carbon steel’s allowable stress for the purpose of steam blow piping stress analysis? The temperature is in excess of 1000 degF.
How can I get (and maybe raise) the carbon steel’s allowable stress for the purpose of steam blow piping stress analysis? The temperature is in excess of 1000 degF.





RE: Allowable Stress for Steam Blow Piping
More seriously... Using the right materials will reduce the likelyhood of people getting hurt and killed. Steam at over 1000 deg is not something to play around with. I guess the best way to deal with the issue is to melt down the carbon steel and add somewhere around 5 to 9 percent chrome and a dash of molybdenum to the mixture, then freeze it and reform it to pipe.
jt
RE: Allowable Stress for Steam Blow Piping
I have been asked to work on the temporary steam blow piping for venting steam to the atmosphere during the cleaning of the main & reheat steam lines.
The temporary piping material will be A106B but the permanent piping will be all made of P22, for the reason that you've already mentioned. The allowables shown in table A1 of B31.1 stops at 800degF but the steam to be used for cleaning will be over 1000degF.
Taking out the creep factor might be the best approach since these temporary piping will only have a few hours of life and will probably be junked forever. But how do you get the allowable values using this approach?
Thanks in advance!
RE: Allowable Stress for Steam Blow Piping
By the way, if this is temporary vent piping with no isolation points to atmosphere, you still might be able to get by at your own risk with using SA 106B carbon steel, assuming the maximum 1000 deg F for allowable stress per ASME Section II, Part D (I hope my esteemed ASME B31 colleagues don't figure out my alias).
RE: Allowable Stress for Steam Blow Piping
RE: Allowable Stress for Steam Blow Piping
The cleaning steam condition varies as per the individual line or common header to be cleaned. But it appears that a section of the temporary carbon steel piping (between the CS/P22 interface up to the first temporary desuperheater) will be subjected to a condition up to 1022degF & 80 psi. It is this section of the pipe that I am needing stress allowables. The highest design condition of the permanent piping, which is the main steam line, is 1065F & 690psig.
RE: Allowable Stress for Steam Blow Piping
I would hope they prohibit re-use or re-sale of the piping!
RE: Allowable Stress for Steam Blow Piping
I have asked the system engineer who spec'd the temporary piping and it looks like he could provide me the data I needed based from previous projects although he could not explain how those were obtained.
My understanding is that the CS piping will be junked after the steam blowing.
Thanks for all your help!
RE: Allowable Stress for Steam Blow Piping
I2I
RE: Allowable Stress for Steam Blow Piping
I'm not in that business now, but I thought I'd toss in what I know from what we used to do....in that exact business.
Thanks,
CW3
RE: Allowable Stress for Steam Blow Piping
RE: Allowable Stress for Steam Blow Piping
FWIW, I was in the field engineering building, at least 300 yards away, when a 12" crescent wrench, some odd pieces of pipe, and some 3/4" bolts/nuts sprayed the side of the building on the 2nd blow -- actually the wrench went thru the wall and onto a co-worker's desk. Needless to say the direction of the discharge pipe was changed the next day...
RE: Allowable Stress for Steam Blow Piping
I was given the value of 4ksi @ 1050degF which is what was used from the copied job. I have no idea how it was obtained. I'm still trying to find out.
Ross,
The project we are doing is a 470MW 2085psi/1050. The main line just before the turbine stop valve was designed with an end pipe that is blind flanged during the normal operation. It is at this end pipe that our temporary blow piping is attached to. No chemical cleaning. Only continous blowing.