A335-P11 - allowable stress -1960s ?
A335-P11 - allowable stress -1960s ?
(OP)
hello,
We are in the process of evaluating an old main steam Line for a fosil fueled power plant in New England. The plant was constructed in the early 1960s and uses A335-P11 (seamless)for the piping material. Operating temperature is 1015F and pressure is 2200 psig
It is my understanding that ASME has changed (lowered) the allowable stress levels over the years for this material. Additionally, I understand that there are restrictions on use.
Does anyone have any documents that details and explains the change in allowable stress levels ?
Additionaly, I am looking for official restrictions in use of this material for high temperature applications. I am well aware of the history of creep related failures in MS and HRH systems since the late 1980s, but I have never found any offical restrictions on use...
Any web-based references or "white papers" would be appreciated...
regards,
MJCronin
We are in the process of evaluating an old main steam Line for a fosil fueled power plant in New England. The plant was constructed in the early 1960s and uses A335-P11 (seamless)for the piping material. Operating temperature is 1015F and pressure is 2200 psig
It is my understanding that ASME has changed (lowered) the allowable stress levels over the years for this material. Additionally, I understand that there are restrictions on use.
Does anyone have any documents that details and explains the change in allowable stress levels ?
Additionaly, I am looking for official restrictions in use of this material for high temperature applications. I am well aware of the history of creep related failures in MS and HRH systems since the late 1980s, but I have never found any offical restrictions on use...
Any web-based references or "white papers" would be appreciated...
regards,
MJCronin





RE: A335-P11 - allowable stress -1960s ?
I would suggest you contact MPC (http://www.forengineers.org/mpc/index.html) because they have a comprehensive database on Cr-Mo materials. MPC has access to a number of sister organizations like PVRC and the WRC that could locate this specific information (this is not a commercial plug).
I do remember a paper that was published in the 1980's (shortly after the Mohave steam line failure) that mentioned the revision (lowering) to the ASME B&PV code allowable stress values for 1.25% Cr - 1/2% Mo alloy steel -and reasons for this revision.
If I can find this paper, I will provide the date and author.
RE: A335-P11 - allowable stress -1960s ?
Some Info on P11
Look at the bottom of the page.
h
BR#1586
http://www.babcock.com/pgg/tt/tech%2Dservice.html
RE: A335-P11 - allowable stress -1960s ?
Anyway, to summarize;
A chart was provided with the article that shows the allowable stress reductions starting from 1951 to 1955 to 1967 and to 1991 within the elevated temperature ranges of 950 deg F to 1050 deg F. A major change in allowable stresses was noted in 1967 - the allowable stresses were reduced by up to 25% in elevated temperature ranges.
Another 15% reduction in allowable stresses was reported in 1991 for P11.
Apparently creep crack propagation tests were conducted to show the affects of changes in allowable stress. The information provided in the article compared creep crack growth rates at 1005 deg F using the 1991 (recent code revision at that time) allowable stress value to the allowable stress values in 1967 and 1955. The results were dramatic;
- using a 1991 allowable stress at 1005 deg F base line crack growth rate established
- using a 1967 allowable stress, at 1005 deg F a 6% increase in crack growth rate was observed
- using a 1955 allowable stress, at 1005 deg F a 60% increase in crack growth rate was established.
RE: A335-P11 - allowable stress -1960s ?
http://www.lindahall.org/
I seen mention of an ASTM Standard WK 658 for AE testing of steam lines that is supposed to be out anytime.
Sure glad we only had 650 psig @ 750?F steam. We were also fortunate in the man that oversaw the design, construction, and running the Powerhouse didn't skimp on materials.
RE: A335-P11 - allowable stress -1960s ?
The website references are very helpful....
I also found allowable stresses in an old 1960's vintage(?) book by "Brownell and Young".
The allowable stress levels matched exactly with those stated in the B&W plants Services Buletin PSB-1
After reading up on this topic, I am beginning to wonder,..... Is there anyone out there still using P11/T11 materials ? Havent the more fatigue resistant, higher chrome-molly materials become the standard ?
MJCronin
RE: A335-P11 - allowable stress -1960s ?
P91 has fantastic properties but its very difficult to achieve these properties in welded construction.
Regards,
XHPIPE
RE: A335-P11 - allowable stress -1960s ?
RE: A335-P11 - allowable stress -1960s ?
RE: A335-P11 - allowable stress -1960s ?
MJC