Why do we need impact testing for 2205 flange?

[jeevesme]

We have a carbon steel vessel that has a 304L nozzle installed on the top head. We are switching out the 2" sch40 nozzle with 2205 for CLSCC resistance. The vessel has an MDMT of -20. The company performing the calculations is saying that we need to have impact testing performed for the 150# flange per UHA-51(d)(3).

ASME Sect.VIII vessel
150psig mawp
-20mdmt

 

[NamiTS]

Impact testing exemption is for 2205 less than 3/8" thick which the flange is not is why they are saying that.

 

[jeevesme]

Oh okay. I was taking it that since the MDMT is -20 and above that it didn't need impact tested. But it seems that UHA-51(d)(3) applies only to (-a, -b, and -c)? So based on this, hypothetically, would it need impact tested if the MDMT were 32F?

 

[NamiTS]

Per UHA-51(d)(3)(-a) austenitic ferritic duplex steels are exempt from impact testing from -20F and warmer if less than 3/8" thick 2205 is duplex and would fall under that. So if it was 32F and .210 wall for the pipe then yes you would be exempt however the flange is going to be thicker than 3/8" and therefore does not get an exemption.

 

[EdStainless]

I would hope that you are also impact testing per ASTM A923 to verify that this material was heat treated correctly and free from intermetallics.
This (or the A923 corrosion test) should be standard practice for all DSS.

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P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

So you are welding part of this existing CS nozzle on to a 2205 nozzle extension neck ? How do you make that work from a galvanic corrosion perspective ? Wouldnt it be better to use a low temp CS flange and then mate it onto a 2inch 2205 matching flange with insulating flange bits?

 

[SnTMan]

NamiTS, I have always found it "interesting" that Part UHA does not have the various definitions of governing thickness found in Part UCS.

Regards,

Mike

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

 

[NamiTS]

georgeverghese,

I am pretty sure he's meaning they are cutting the entire 304L nozzle off and replacing with duplex. However the vessel is carbon steel.


SntMan, UHA-51s short paragraph of definitions leaves much to be desired when compared to what we get in UCS-66. Must've been a Friday when they wrote it.