1.25Cr1Mo-V - code allowable stresses
1.25Cr1Mo-V - code allowable stresses
(OP)
We have been supplied with a steam turbine inlet stop valve of cast 1.25Cr-1Mo-V. I have not been able to find an ASME tabulated list of allowable stresses vs temperature. Is there an equivalent DIN or EU or BS or Japanese material spec that I can use to arrive at an equivalent ASME allowable stress?





RE: 1.25Cr1Mo-V - code allowable stresses
RE: 1.25Cr1Mo-V - code allowable stresses
Thanks for the info. Can you advise where I can get the Toshiba data.
In our case, The design Temp is 1063 F, and Toshiba provided a weld end prep of 21.26" x 3.02" thick. The EPC vendor goofed big time and simply butted a 18" OD x sched 140 ( 1.56" aw) P91 pipe against the valve, buttered it with P22 filler, and the weld failed after 1 yr operation.
RE: 1.25Cr1Mo-V - code allowable stresses
RE: 1.25Cr1Mo-V - code allowable stresses
Failure occurred in the carburized zone of P91 pipe.
RE: 1.25Cr1Mo-V - code allowable stresses
With respect to obtaining design allowables from GE, Toshiba, etc., what little info I have was obtained through months of requests from the Owner/Purchaser. I have never been able to obtain same (through the Purchaser or any other)from GE or Seimens.
RE: 1.25Cr1Mo-V - code allowable stresses
I don't have the information with me so I can't provide a lot of details, but I have heard that ASME is incorperating some of the ASTM A356 cast alloys in Section IX, which means it would have to be added to Section II or the B31 codes I think. You might check with an ASME committee member if you have a connection.
RE: 1.25Cr1Mo-V - code allowable stresses
Thanks for the tip. It will help if ASME recognizes the commonly used cast material, and it would help the general public even more if B16.25 and B31 explicitly inlcuded a paragraph dealing with butt welding of dissimilar strength alloys.
Although it seems elementary to me that the weld thickness must be equal to or greater than the minimum wall thickness required of the minimum strength material ( considering tube, valve, and filler), the EPC vendor still does not admit the failed weld doesn't meet code.
RE: 1.25Cr1Mo-V - code allowable stresses
If failure occurred out of the warranty period, retrieving costs for repair from the EPC contractor could prove difficult. Legal costs would far exceed the repair cost.
RE: 1.25Cr1Mo-V - code allowable stresses
I would like to think is is negligence; they repeated this error on 3 duplicate units, and all 3 will be out of service for over a month until we obtain the required transition joints. The lost power costs are staggering, considering otehr plants are out of service for scheduled maintenance.
RE: 1.25Cr1Mo-V - code allowable stresses
Appropriate PWHT is required for both the P91 and the 1 1/4 Cr-1Mo-V alloy. Inappropriate PWHT will adversely affect high tempearture properties of the weld joint.
RE: 1.25Cr1Mo-V - code allowable stresses
I think you are probably 100% right, except that the EPC contractor did not follow the Toshiba procedure: Toshiba had provided an explicit weld detail for a 3.02" thick weld. But B31.1 does require the Owner to inspect the nonboiler external piping weld.