UW-11(a)(5)(-b) Spot

[loilfan]

Apologies for another UW-11(a)(5)(-b) post. All the threads on this website and other documentation I've read (such as Pastor's Pressure Points Newsletter) haven't quite covered my situation though.

I am reviewing the design of an existing VIII-1 vessel from the 2001 ed. It has the following RT & E details and is stamped RT-4:

X-RAY
Shell Long Joints

SPOT UW-11(b)​

Head/Shell Joints

SPOT UW-11(a)(5)(-b)​

Joints in Heads

SMLS​

E Factor
Shell Long Joints

0.85​

Head/Shell Joints

0.85​

Joints in Heads

1.00​

All the examples I've seen discuss when the Category A long seams are either seamless or full RT. It seems to me that UW-12(d) is satisfied because the Category B welds have been spot radiographed as per UW-11(a)(5)(-b), even though the Category A welds haven't been Fully RT'd as per UW-11(a)(5).

Can I use E=1 in the UG-32 calculation for a 2:1 seamless head if spot RT was done on both the Category A and B (Table UW-12 Type 1) welds?

 

[david339933]

RT of long seam is irrelevant to satisfy UW-12(d). Only UW-11(a)(5)(b) need be satisfied. In other words spot RT on Head to Shell Circ.

Looks correct....spot on Long Seams, Spot on Circ Seams, + Spot for Head thickness (UW-11(a)(5)(b)). Must be RT-4 as you cannot have E=1 for head thickness with RT-3.

 

[david339933]

I just noticed you have SPOT UW-11(a)(5)(b) under RT head/shell joints.....you can't use the single shot for UW-12(d) to increase circ joint efficiency. You would need two spots.

 

[loilfan]

david339933, where does the two spots requirement come from? I neglected to say that the Diameter is 10' so each head to shell joint is less than 50ft as per UW-52.

edit: Or are you referring to UW-11(a)(5)(-b) where it says that the spot radiographs shall not be used to satisfy the spot radiography rules as applied to any other weld increment? i.e. one spot RT is required to satisfy UW-11(a)(5)(-b) and a second spot RT is required to satisfy the circ seam joint efficiency.

 

[loilfan]

This link also gives good information for my situation:

http://www.oakleysteel.co.uk/pressure-vessel-welded-joint-efficiency

I had been thinking about the Category A weld mentioned in UW-12(d) as the long seam, but this link explains that I should consider an "imaginary" Category A weld in the seamless head instead. Which, therefore, lines up with david339933's post that RT of the long seam is irrelevant to UG-32 calculations.

 

[david339933]

Yes, cannot be applied to any other weld increment. And yes, imaginary Cat. A in the head.

 

[israr1]

loilfan,

I think interpretation VIII-79-85 will answer all your queries.

 

[loilfan]

Thanks david339933 and israr1!

 

[crosby84]

So to revive this yet again, I have a related question.

After the fact, when you're looking at a pre-existing vessel and you have the U-1 Manufacturer's Data Report, is it supposed to indicate somewhere on the form that uw11a5b was satisfied and that the head JE can be taken as 1.0?

Thanks

 

[loilfan]

There's not a lot of room in Section 15 to write it out, so they will sometimes add it as a note in the Remarks section. I have also seen it in the manufacturer's drawings too.

 

[A clark]

Crosby,

The value of "E" for the thickness of a seamless head is 1, if the requirements of UW-12 (d)and UW-11 (a)(5)(b) are met. The joint efficiency of the head to shell joint is still .70.

 

[crosby84]

A clark,

I understand that. My question was about if the U-1 was supposed to indicate UW-11a5b.

Coincidentally, I came across a U-1 this morning that actually does list "UW-11(a)(5)(b)" in the additional remarks section. I've been operating under the assumption that if it doesn't say it, then it wasn't performed and the head E cannot be claimed as 1.0.

 

[david339933]

I wouldn't put too much emphasis on "if it doesn't say it, it wasn't performed".....MDRs are hard to decipher the amount of NDE completed....for example how do you decipher how much RT was done from an MDR which only states RT-4? That being said, it's still a good idea to put in remarks.

A Clark is just pointing out that you mentioned ".....and that the head JE can be taken as 1.0?". This is usually referred to as efficiency for head thickness calculations rather than Joint Efficiency....so as not to confuse with head to shell circ.

 

[A clark]

Crosby and David:
There are a lot of Certificate holders that still do not understand the meaning of UW-11 (a)(5)(b). When I was a ASME Team Leader I had to educate many Certificate Holders on this subject.