ASME A335 P11 Pipework - onset of creep
ASME A335 P11 Pipework - onset of creep
(OP)
Hi All,
Just wanted to ask for some opinions regarding the temperature at which creep should be considered for A335 P11 pipework. Any comments?
Just wanted to ask for some opinions regarding the temperature at which creep should be considered for A335 P11 pipework. Any comments?





RE: ASME A335 P11 Pipework - onset of creep
So, for SA 335 P11, I would use 950 deg F.
RE: ASME A335 P11 Pipework - onset of creep
I'm sure you're familiar with this website: http://www.ommi.co.uk/etd/eccc/advancedcreep/DShee....
It has many free downloads on creep data.I've attached the individual data sheet for European grade Steel 13CrMo4-5/5-5,which is the nearest equivalence to SA 335 P11.The allowable stress data at various creep life(No of Hours) are tabulated. The data may not be 100% authenticated to calculate the exact creep life.However it provides a good overview.
In addition to the above information provided by metengr, these data may be of help.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.
RE: ASME A335 P11 Pipework - onset of creep
RE: ASME A335 P11 Pipework - onset of creep
Keep in mind that the definition of creep for ASME B&PV design is based on x% deformation at temperature and stress. The stress values determined by ASME Section II Committee are based on the lowest stress to produce either x% deformation at the temperature and stress, or stress rupture or tensile properties. The lowest value governs. So, simply designing at 900 deg F does not mean creep does NOT occur. It simply means that creep will not reach x% deformation for the stress and temperature selected.
Now, what you need to do is to develop a comprehensive in-service based inspection plan to monitor creep at pipe girth welds and high stress locations at wyes and fittings. Don't get hung up on analysis details that try to pin point an exact temperature for creep deformation, that is a fools errand.
RE: ASME A335 P11 Pipework - onset of creep
I understand what you say but a colleague (who has now left) stated that the temperature of 460 Deg C and the Design Temperature of 480 Deg C meant that the A335 P11 would be operating below the temperature at which creep needs to be considered. In view of the design life being 39 years and the fact that the system stresses are quite high I beleive you cannot ignore the effects of creep and as you say it needs to be monitored.
RE: ASME A335 P11 Pipework - onset of creep
RE: ASME A335 P11 Pipework - onset of creep
RE: ASME A335 P11 Pipework - onset of creep
Are there no regulations (OHS) laws that cover operation of high risk plant? API 579 is a well known standard for in-service inspection. Here in Australia, having an in-service inspection plan or policy (and actually doing, and keeping records of inspection) is part of the legal framework of owning and operating "high-risk plant and equipment" which means boilers, vessels and a few other things. We use AS 3788 as a starting point, but API 579 is great. Seems strange for someone to expect to be able to run a high temp vessel without monitoring its condition.
RE: ASME A335 P11 Pipework - onset of creep
Yes there are statutory requirements for inspection of pipework, however in this case during the FEED it was stated that creep was not an issue with the material. However as it is just within the creep range at 460 Deg C operating temp and the "life" of the plant is 30 years and the stress levels are high I beleive the Client should be made aware and should have "creep damage" checks noted in his long term inspection plan so it is not forgotten about.
RE: ASME A335 P11 Pipework - onset of creep
It is unfortunate that the Plant operator does not understand risks associated with potential creep or creep/fatigue failures in piping components. In this case, should a problem develop they will have to react to repair the problem which will cost them time and money. Have you developed a spreadsheet to itemize the cost for inspection annualized over the design life and compare with the cost of lengthy outage and safety? The numbers should speak for themselves.
RE: ASME A335 P11 Pipework - onset of creep
RE: ASME A335 P11 Pipework - onset of creep
You could calculate the expected creep life at your operating temperature.
Since the operating temperature is expected to be lower than the original design temperature the creep strength will be higher and expected life longer. We are talking about logarithmic relationships here so expected life could by >>2x design life.
Also take into consideration that operating pressure might be way lower than design pressure, which would further reduce the actual stresses and increase the ratio between actual stress and creep strength.
For the calculation you could use the Omega method or Larson-Miller Paramater.
Set an inspection date at 2/3 of theoretical life consumption (inspection before that time don't make much sense as creep can only be detected in later stages of life). Depending on your material and the operating conditions this could be well past the intended lifetime of the equipment which would make inspection obsolete.
Additional
Daniel Breyer
Inspection Engineer
http://lnkd.in/dFcQA-w
RE: ASME A335 P11 Pipework - onset of creep
"In this bright future, you can't forget your past..." Bob Marley
RE: ASME A335 P11 Pipework - onset of creep
You always provide good responses and I am in-line with your thinking. Just wanted to get opinions.
RE: ASME A335 P11 Pipework - onset of creep
As a point of reference, a common carbon steel (A-516-70) is shown at 700 F.