ASTM A335 Gr P11 allowable stress at temperature
ASTM A335 Gr P11 allowable stress at temperature
(OP)
ASME B31.3 lists ASTM A335 Gr P11 material without any restriction on it's use at temperatures over a 1100 deg F. With the allowable stress of 20 Ksi at the min temperature to a low of 6.3 ksi at 1100 deg F. This is only 14% of the value at the min. temperature. Use of this material at these temperature ranges will result in a high wall thickness. Thickness over 13 mm will require heat treatment applied. It will be appropriate to use a matearial with higher allowable stress as other grades of Cr-Mo steels as P22 and higher. Is there any other code implied code restriction that may not allow the use of the P11 material at the temperature range of 1100 deg F. The allowable being so low at temperature, it becomes difficult to meet flexibilty, requiring larger loop lengths so as not to exceed the fractional allowble stress available.





RE: ASTM A335 Gr P11 allowable stress at temperature
RE: ASTM A335 Gr P11 allowable stress at temperature
Over 1000F one should be considering T22, T23, t24, T91, T92, austenitics. In addition to issues of weight and flexibility there are also issues of corrosion and ease of fabrication.
"Nobody expects the Spanish Inquisition! "
RE: ASTM A335 Gr P11 allowable stress at temperature
RE: ASTM A335 Gr P11 allowable stress at temperature
What is the T22 designation? Is it the same as the P22.
http://www.s-k-h.com/media/de/Service/Werkstoffbla...
The alternate designation depicting the composition is misleading, '10CrMo9-10'
stanweld,
I am trying to counter a contractor who insists that he is code compliant and therefore correct about his material selection of the P11 for the 1100 deg F service temperature. I can see his position, having made the piping system. It is costly to undo it.
RE: ASTM A335 Gr P11 allowable stress at temperature
This is a contractual problem, and not a technical problem. Good luck with trying to undo this mess. There is nothing in the Code to prohibit this material for use at 1100 deg F. I absolutely agree it is not the material choice but this is where experience comes into play.
RE: ASTM A335 Gr P11 allowable stress at temperature
By the way, per B31.3, Table A-1, the design allowable at 1100 F is 2,800 psi.
RE: ASTM A335 Gr P11 allowable stress at temperature
The regeneration case of the reactor is what has this high temperature, but at a lower pressure of about 10 bar g.
Will it be appropriate to have a Company specification that will limit the induced operating stress to say 80% of the code allowable expansion stress range? The intent of this being that there will be an additional margin for uncertainities as route changes, fabrication errors and other.
I happened to read a post in eng-tips that ASME B31 may be including an allowable for the operating condition.
RE: ASTM A335 Gr P11 allowable stress at temperature
RE: ASTM A335 Gr P11 allowable stress at temperature
I do not know the specifics of your reactor, but some reactors have issues related to hydrogen damage during the regeneration cycle- if this is applicable, there may be other metallurgical concepts to be reviewed when selecting a material for a reactor.
"Nobody expects the Spanish Inquisition! "
RE: ASTM A335 Gr P11 allowable stress at temperature
You can not counter with your vendor if you do not specify higher grade material in the begining. You are going to loose the fight.
How much % below the code allowable, it is personal preference. 90-95% of the code allowable is good to me in your case since regeneration is a short term operation, pushing to the limit shall not be a problem. No one is going to challenge you as long as you meet the code allowable. Be sure you have all weights counted including insulation. Many times, weights are underestimated that will cause problem because it is very sensitive for low allowable stress at high temp.
RE: ASTM A335 Gr P11 allowable stress at temperature
10 yrs ago, in London, there was a paper delivered by Alstom/CE on the economic advantages of using p91 in lieu of P22 piping, and the 2 primary savings were related to (a) lower metal mass results in savings in supports and(b) lower section modulus rsults in much fewer expansion loops, both are due to the much thinner wall thickness.
"Nobody expects the Spanish Inquisition! "