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C- 1/2 Mo Availibility

C- 1/2 Mo Availibility

C- 1/2 Mo Availibility

Working a proposal for replacement of an old S&T exchanger, materials as noted. I've not dealt with this stuff before, so can anyone tell me, in general is this stuff available?

Usual product forms, plate, pipe, forgings, tubes, B16.5 flanges.



The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: C- 1/2 Mo Availibility

I'm sure it's around somewhere out there, but generally speaking, C-1/2 Mo has been replaced with 1-1/4 Cr materials due to HTHA concerns (the old Nelson Curves had a C-1/2 Mo line that's since been removed since there were enough failures below it). Have had serious problems tracking down materials for repairs to C-1/2 Mo vessels.

Personally wouldn't even consider it an option for a new vessel.

Nathan Brink

RE: C- 1/2 Mo Availibility

NBrink, thanks, I'll alert the sales guys :)



The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: C- 1/2 Mo Availibility

These tubes can still be found in the USA. They are still used in boiler applications.

RE: C- 1/2 Mo Availibility

Ugh, why? 1-1/4 Cr won't be that much more, and will have higher creep strength and be immune to FAC...

Anyhow, I've had a devil of a time finding plate...

Nathan Brink

RE: C- 1/2 Mo Availibility

C-1/2 Mo boiler tubes were commonly used in the boiler industry, and started from the oil field industry. However, this material fell out of favor with most because the C-1/2 Mo has been prone to graphitization failures in elevated temperature service.

RE: C- 1/2 Mo Availibility

Actually there are two exchangers, almost identical designs, vintage mid 70's. Customer requests "Replace in kind", which means, no one ever knows exactly what :)

These designs use several thicknesses of plate, from thick to thin, body flange forgings, B16.5 flanges, pipe and tube all from C-1/2 Mo. I am always leery about availability with materials I don't use all the time, after all there is a reason they're not common.

I have run the designs as C-1/2 Mo, and am going to let sales & estimating know availability may be a problem. I would guess substitute materials will need to be approved by the customer. I'll let 'em have at and re-run the designs again later if needed.

Thanks again,


The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: C- 1/2 Mo Availibility

Plate availability is a different problem. You can find high strength, Manganese - Moly plate but it might not be suitable for your design parameters.

WBrink, I do not dispute your statement at all, only to indicate the availability of C-1/2 Mo and 1/2Cr-1/2Mo tubing which we have used in boiler repairs with like tubes.

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