Extent of RT & Joint Efficiency

[Mac111]

Ref : Non-Mandatory Appendix L

I would like to understand the meaning of "UW-11(a)(5)(b) Not MET E = 0.85" For Seamless Head, in the Flow Chart Fig. L-1.4 - 2 Joint Efficiency and Weld Joint Type - HEADS

In this Flow Chart, against Seamless Head (after not selecting Full RT Mandatory UW-11(a)), there are 2 joint Efficiencies for 2 different conditions.

Condition 1: UW-11(a)(5)(b) MET E = 1.0

Condition 2: UW-11(a)(5)(b) Not MET E = 0.85 (1)

Can any one interpret the meaning of condition 2?

Is it the same which I think.....?

a. All Category A Joints are not fully radio graphed

And / OR

B. All Category B Joints of vessel are not spot radio graphed as per UW-11(a)(5)(b)

Please elaborate on this.

And now the main question:

The question arises - when we are using the SEAMLESS head, whatever may be the RT selection for the entire vessel, why we can not take joint efficiency as 1.0 for calculating the thickness of only that seamless head.

 

[vesselfab]

we are lalking about either a semless head or a head that has the cat a weld fully radiographed and the conditions stated are for the cat b weld joining to the shell

#1 UW-11(a)(5)(b) met....means there will be a radiographic film taken on that seam. that spot will meet the requirements and interpretation of full radiography but only that one spot, usually at the T joint of the adjacent shell can. we generally shoot two spots.

#2 UW-11(a)(5)(b) not met....means you have selected either spot radiography or no radiography. with spot, there is one film taken ever 50 feet of each welders welding. there may or may not be a film on that seam. If there is, it is not graded the same as full radiography. No radoiography is self eplanatory.


there is a rule about seamless shell sections joined together. that is where this comes from.

 

[CodeRef]

UW-12(d) discusses seamless shells/heads that have imaginary Type 1 long seam welds with the equivalent of 100% radiography as required by UW-11(a).

For calculations involving circumferential stress in seamless shells/heads, E = 1.0 when the spot radiography requirements of UW-11(a)(5)(b) are met. E = 0.85 when the spot radiography requirements of UW-11(a)(5)(b) are not met, or when the Category A or B welds connecting seamless vessel sections or heads are Type No. 3, 4, 5, or 6 of Table UW-12.

UW-11(a)(5)(b) is ASME's way of providing a means to ensure confidence in the quality of welding when attaching vessel shells/heads.

What is difficult for many to understand is that the weld for which radiography is being conducted is not the joint to which the efficiency is being applied. The Spot RT requirement can be classified as a "quality shot" for confidence when determining the joint efficiency of the intersecting (imaginary or real) longitudinal joint.

FAQ731-376