UHA-51 And Impact Tests

[SnTMan]

Well, I have run into a new situation. I am replacing a shell of an older HX, formerly CS and now 2205. MDMT is +51 F. The cylinder is 3/8" thk with some both thinner and thicker parts both welded and bolted on the pressure boundary. Per UHA-51(d)(3)(a), the 3/8" and thinner materials are exempt from impact tests and, apparently, NOTHING else is. Apparently, the weld procedures will need to be impact tested for joining the thicker materials to the thicker, if duplex weld metal is used. OK, so far.

The duplex vessels I have done in the past had never met the 3/8" limit, so the question of exempting some components and not others did not come up.

What I find odd is that there is nothing in Part UHA that corresponds to the provisions in Part UCS-66 that define governing thicknesses, exemptions for nozzle flanges and so forth.

So I apparently need to impact test some 1" and 2" 150 lb flanges and a 1" thick bolted cover as well as the welded, thicker parts using a qualified weld procedure.

Is anyone familiar with interpretations, etc. providing any further guidance?

Regards,

Mike

 

[TJOrlowski]

Have you explored the UHA-51(g) exemption?

I'm not familiar with any interpretations, and I didn't see any revisions to UHA in the summary of changes for the 2010 edition, but maybe there will be a surprise.

What are your AI's thoughts?

-TJ Orlowski

 

[SnTMan]

TJOrlowski, UHA-51(g) not really an option, as stresses are not low enough.

Here again, a correspondence with UCS-66 is lacking, as the latter contains provisions for lowering the MDMT for flanges such as UCS-66(b)(1)(b) & (c).

Its odd to me that UHA-51 contains so little guidance.

Regards,

Mike

 

[TJOrlowski]

Just spitballing on the UHA-51(g).

I'd be interested to hear your AI's comments. We had a 2205 job where we impact tested everything, due to not having a definitive yes/no from the AI.

Good old CYA.

-TJ Orlowski

 

[SnTMan]

TJOrlowski, I hear you, and in this case I am just going to impact test everything that does not clearly fall under the thickness exemption, not that big a deal.

However, it just made me curious. I'll talk to the AI if I get a chance.

Thanks,

Mike

 

[TJOrlowski]

We received our 2010 BPVC late last week: no significant changes to UHA-51.

-TJ Orlowski

 

[SnTMan]

I had forgotten that a confounding factor was contained in Appendix JJ (see Fig JJ-1.2-6 3rd step), which reads somewhat differently than UHA-51(d)(3)(a). In any case our Agency has confirmed the language of UHA-51(d)(3)(a), and informed us that Fig JJ-1.2-6 contains a typo.

TJOrlowski, I haven't gotten my 2010 books yet, can you tell me if Fig JJ-1.2-6 has been changed?

Thanks,

Mike

 

[TJOrlowski]

Figure. JJ-1.2-6 has been changed.

Step 1 from '09 addenda reads:

Is MDMT colder than -20*F (-29*C) and nominal material thickness exceed that shown in UHA-51(d)(3)?

Step 1 from '10 edition reads:

Is MDMT colder than -20*F (-29*C) or nominal material thickness exceed that shown in UHA-51(d)(3)?

-TJ Orlowski

 

[SnTMan]

Uh-huh