B31.1 Vacuum Piping and Out of Roundness
B31.1 Vacuum Piping and Out of Roundness
(OP)
Hello All,
I am currently designing a geothermal power plant piping system in which we are using an expensive refrigerant as our working fluid. One of our operating cases is a full vacuum during working fluid evacuation. Thus I am designing the piping to handle a 15 psi external pressure as well as the internal pressures it will see during operation.Some of the lines are of substantial diameter 30-48 inches.
I would like to use ASTM A53 Gr. B, but I have found out that A53 piping has an out of roundness allowance of 2%, rather than the standard 1% for most other piping specs.
The BPVC section VIII div 1 UG-28 to UG-30 referanced by B31.1 all seem to be based on a 1% out of roundess. (per L.C. Peng book Pipe Stress Engineering)
Due to the sensitivity of external pressure calculation to out of roundness, how do I correct the calculation to properly account for the additional 1% of out of roundness in A53 pipes?
I am currently designing a geothermal power plant piping system in which we are using an expensive refrigerant as our working fluid. One of our operating cases is a full vacuum during working fluid evacuation. Thus I am designing the piping to handle a 15 psi external pressure as well as the internal pressures it will see during operation.Some of the lines are of substantial diameter 30-48 inches.
I would like to use ASTM A53 Gr. B, but I have found out that A53 piping has an out of roundness allowance of 2%, rather than the standard 1% for most other piping specs.
The BPVC section VIII div 1 UG-28 to UG-30 referanced by B31.1 all seem to be based on a 1% out of roundess. (per L.C. Peng book Pipe Stress Engineering)
Due to the sensitivity of external pressure calculation to out of roundness, how do I correct the calculation to properly account for the additional 1% of out of roundness in A53 pipes?
A question properly stated is a problem half solved.
Always remember, free advice is worth exactly what you pay for it!
http://www.ap-dynamics.ab.ca/





RE: B31.1 Vacuum Piping and Out of Roundness
The calculation method in this paper:
"Effect of Initial Eccentricity on Collapse Pressure of Circular Beam Tubes", S. Yadav
Fermi National Accelerator Laboratory, Batavia IL www.flab.gov
Gives results that seem to correlate well with a single data point collected/estimated from an expensive incident associated with pressure testing of jacketed tube.
Mike Halloran
Pembroke Pines, FL, USA
RE: B31.1 Vacuum Piping and Out of Roundness
If your pipe meets the permissible variations in ASTM A 53, you don't need to adjust your external pressure calculations. Paragraph UG-80(b)(10) of BPVC Section VIII, Div. 1 says...
RE: B31.1 Vacuum Piping and Out of Roundness
How many feet of pipe?
Could you consider running the pipe through a lathe or pulling a die through to smooth it out? It would reduce wall thickness - and be expensive! - but for a few large bore thick-walled pipes it might be worth the effort.
RE: B31.1 Vacuum Piping and Out of Roundness
Thank you for that paper reference, thats goes straight into my vast and evergrowing collection of usefull stuff.
doct9960:
I think you may be on the rigth track with your statment, the only thing I need to know to close the loop is if A 53 is an allowed piping material for vessel fabrication in the BPVC. If you could point me to were this is hiding in the code I would be most appreciative.
racookpe1978:
The lengths are between 30 and 100 feet in length.
As usual managment is pressuring for lowest cost and while both of your solutions are valid we have niether the capacity to do it ourselves nor the money to get it done. It would be cheaper to go to more expensive pipe.
A question properly stated is a problem half solved.
Always remember, free advice is worth exactly what you pay for it!
http://www.ap-dynamics.ab.ca/
RE: B31.1 Vacuum Piping and Out of Roundness
SA-53 is listed in Table UCS-23
RE: B31.1 Vacuum Piping and Out of Roundness