Which UCS-66 Curve for SA-212 B Material

[UW1981]

We are moving a vessel to use in a different service (absorber to amine still). The vessel was built in 1965 using SA-212 B Firebox, but does not have a min. temperature stamped on the plate. I believe at that time, the code allowed -20F for this material. Since I am moving the vessel, I would like to comply with current code (internal policy). Given this, I was going to use API 579 to determine the hydro pressure I need in order to get the -20 F MAT I want. In order to do this, I need the UCS-66 Curve MDMT...but I am not sure which curve to use. The vessel is 1-7/16" thick (yes....way more than I need for the still...but the vessel is in our stock). Although the code indicates the replacement material for SA-212 B is SA-515/516-70, I am very hesitant to use Curve B for the MDMT. I have not been able to find anything on any interpetations regading this issue. I believe the right thing to do is use Curve A for the UCS-66 MDMT (as a non listed material) and then plug this into the API 579 hydro MAT reduction calculation. Is this the right way to go about this?

 

[steris]

I would use curve A. Even for Curve B the MDMT for 1-7/16" thick material is about 50F. I doubt that you'll be able to keep the -20F.

 

[metengr]

Use Curve A. Interestingly enough, I did some research on SA 212 Grade B firebox quality steel. According to the 1958 Edition of ASTM Ferrous Metals, SA 212 Grade B, firebox quality steel, was supplied fully killed and either grain refined or coarse grained. For plates over 2" in thickness, grain refinement was specified by either normalizing or heating the steel uniformly for hot forming.

As a side note, and I believe unclesyd touched upon this in another thread, the SA 212 plates could be furnished to meet ASTM A 300 "Pressure Vessel Steels for Service at Low Temperature". The minimum temperature requirement was -50 deg F, and required SA 212 plates to have bumped up manganese content to a maximum of 1% by mass (versus 0.90% maximum).

What does this mean? It means SA 212 Grade B specified without grain refinement would exhibit Curve A properties for impact exemptions. However, given a slightly altered Mn content and grain refinement, this material is capable of low temperature service conditions to -50 deg F.

 

[UW1981]

steris/metengr - thanx for the responses. The information I have does not indicate the plate meets ASTM A300. I will use Curve A, and then proceed to API 579 to get my -20 requirement.

 

[PVDean]

Getting the MAT down to -20 seems like a lofty goal. Is this a derived requirement?