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Hardfacing valve seat

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Yash23

Mechanical
Jan 5, 2015
3
Hi everyone!

I'm doing technical bid evaluation of valve and I came across with the below query.

As per our standard specification, seat and disc seating surfaces shall be hard faced with Stellite 6. Our valve body & trim is A351 CK3MCUN for CL. 1500 nozzle check valve. One vendor offered integral seat instead of HF while the other vendor informed that non of their customers have previously asked to HF 6Moly material & is offering a screwed nozzle seat with same trim material.

My question is, A351 CK3MCUN exempted for HF? If I'm not mistaken, Stellite-6 is harder than A351 CK3MCUN.

Thanks!
 
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A351 CK3MCUN exempted for HF?

You have tried to be nice to the vendor. IMO, it can be a good question to the vendor who said "non of their customers have previously asked to HF 6Moly material".
 
Dear Yash23,

When you do such evaluations, keep in mind that the original spec is quite sacrosanct, i.e. a lot of experience and deliberations have been behind its making....

The hard facing of the seat of a valve automatically suggests about the erosive nature of the service, it could be steam in your case....

How could a hard facing be replaced with a casting say even of the same composition?

Change the vendor, or re-float the P.O.

Regards.

DHURJATI SEN

 
Normally these 6% Mo alloys are used in sever corrosion environments.
Weld overlaying these alloys can seriously reduce the local corrosion resistance.
While these alloys have good erosion resistance they are nowhere as good as Stellite.
You need to decide which is more important, corrosion or wear.
What material did you use in this service before? What was the failure mode?
And if you need a hard facing you might look at alternatives to a conventional weld overlay.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
 
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