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G40.21-38W Material

G40.21-38W Material

G40.21-38W Material

(OP)
Hi All,

I have recently come across an issue with G40.21-38W material and I was wondering if anyone else has come across this problem and what steps they took.

On 2 seperate tanks I have recently worked on I have received material specified as 38W on the MTR.  However on closer inspection it does not meet the additional chemistry requirements of API 650 Table 4.1.  On the first tank I caught it before the material was used and we had it replaced, however, on the second tank I caught it during my final review.  Now I have a tank where 70% of the shell material is not approved per API 650.  My concern is I don't know if my tank now meets my MDMT of -40F.  No impact testing of the plates has been done as it was impact test except to -40F.  I also don't have any crops or cutouts that I can send for testing.
   The specific item that the material fails is the Vanadium to Nitrogen ratio.  API 650 specifies a minimum ratio of 4:1 but I have a ratio less than that.  Any metalugists out there who know the significance of this ratio?

RE: G40.21-38W Material

(OP)
Has anyone ever recertified material to Grade 250?  The way I read API 650, Grade 250 steel is a method of reclassifying steel from a foreign mill for use in API 650.  My question is why is there so few restrictions on it?  As per Table 4-2 the steel has to meet a few strength requirements and carbon content and then you could classify it as a Gr III material.

I don't understand how you can have so few requirements on a steel and then give it an impact test exemption to -40. I haven't found a reference to Gr250 elsewhere, is it defined in another spec?
 

RE: G40.21-38W Material

Do you have the manway and nozzle cut-outs from the tank?  If so, that would let you test several pieces of the most critical plate.

RE: G40.21-38W Material

(OP)
Unfortunatly no.  The material is not in the bottom course and no nozzles were installed in it.
 

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