3" dia pipe on head without PHWT

[jrupert24]

I have a compressor head (P1)about 36" dia X 8" thick that we need to weld in a 3" dia plug on outer diameter edge. The head gets final precision machining and we can not PWHT after this. Normally, we specify no more than 2" dia so we can make an as-welded fillet with no post weld heat treat. Customer wants a 3" dia so what are my options? I'm guessing I need to make a butter layer where the pocket is machined with either 309L or Inconel, PWHT, and then make final weld from butter layer to P8 pipe. Any recommendations? Would Inconel be better for butter pocket or would 309L be OK.

If you need more detail let me know.

Thanks,

 

[stanweld]

Are you confused? I assume that you are referencing Table UCS-56 as being applicable. Note (2)(c)(5)applies to joints in vessels under UW-2, Lethal Service.

Note 2(a)is applicable "for welded joints over 1 1/2" nominal thickness"; not the base metal thickness. It does not apply to a smaller (assumed) fillet welds as you described.

In the USA, compressor heads need not be manufactured per ASME VIII, Div.1.

 

[jrupert24]

Being confused is a definite and daily possibility. Some of this is new to me so be gentle.

We do produce a lot of systems that would be considered lethal, however this one is not one of them.

I have heard the statement about the head need not built to ASME section VIII. I checked into API 617 7th ed and it does refer to welding to ASME Section VII and Section IX for cases, but does not mention the heads. We do try to follow as best we can for any welding. Can you explain why the head doesn't apply? Just curious.

So per you comment, post weld heat treat would not be required for a 3" sch 80 socket welded to the face of the head??

This would be good news as this would save a lot of time and effort.

Anymore help with this would be great as I will have to challenge the norms here.

Thanks,

 

[stanweld]

The key to your design/fabrication requirments appears to be API 617, assuming that that is your Contract requirement. Unfortuneately, I do not have a copy of API 617. I have been involved with many compressors in the more distant past and their manufacture was proprietary and the heads were often not fabricated from ASME Section II materials; however, Welding Procedures for all of those compressors were required to be qualified per ASME IX.

You need to review API 617 to verify exactly how it references ASME VIII, Div.1 as it pertains to welding. Should API 617 require PWHT in accordance with ASME VIII, Div.1 UCS-56, the defined weld is not subject to PWHT.

 

[jrupert24]

Thanks for the reponses. Between API, ASME and customer specs, and our own exceptions to codes and customers specs its nearly impossible to figure it all out. I'm mostly looking for intent.

Let me make sure I understand. (I have the lastest copy). UW-40 describes nominal thickness. Table UCS-56 says "up to 2" nominal" use 1 hr/in. Down in notes (2)(a) says it mandatory for welded joints over 1-1/2". Do I assume then that it is not mandatory up to 1-1/2" in non-lethal service?

For lethal service (as described in UW-2), PWHT is required for all weld thicknesses (2)(c) with the exceptions listed in (2)(C)(1-2). Since I do not have a lethal service application this time, thissection doesn't apply.

I am going to ask this final question, because it will come up soon. What if I have lethal service, ASME Section VIII applies to heads and I have to make a 3" dia pipe weld. Do I need to PWHT?

Thanks. I really appreciate your help.

 

[stanweld]

If ASME VIII, Div.1 requirements must be met, PWHT is mandatory in Lethal Service. The exceptions to PWHT in Lethal Service are clearly listed in note (2)(c). Note (2)(c)(1) would apply for the weld described.

 

[metengr]

Customer wants a 3" dia so what are my options? I'm guessing I need to make a butter layer where the pocket is machined with either 309L or Inconel, PWHT, and then make final weld from butter layer to P8 pipe. Any recommendations? Would Inconel be better for butter pocket or would 309L be OK.

I would consider a temper bead approach, using Welding Method 5 in the NBIC.