Table UW-12 / Head Circ. Seam JE Clarification 1

[jproj]

UW-12(d) clearly specifies the joint efficiency for seamless heads with or without spot radiography (0.85). Does the code specify JE for seamed (e.g. two-piece) heads? It is my understanding that it depends on the RT performed on the head long seam(s).

For instance, if the 2-piece head long seam is full radiographied, but the head to shell seam is not radiographied, the head to shell seam joint efficiency is 0.85.

However, if the no radiography is performed on the 2-piece head long seam, the joint efficiency for this seam as well as the head to shell seam is 0.70 per Table UW-12.

Was this clarified in an Interpretation? I can see that there are many interpretations relating to JE, but I only have interpretations from the 1989 and 1995 codes.

Thanks in advance!
jproj

 

[CodeRef]

UW-12(d) clearly specifies the joint efficiency for seamless heads with or without spot radiography (0.85).

No, it does not, it gives JE based on two conditions!

Read UW-12(d) again..... here it is for convenience.....I have highlighted in BOLD the key words....

(d) Seamless vessel sections or heads shall be considered
equivalent to welded parts of the same geometry in
which all Category A welds are Type No. 1. For calculations
involving circumferential stress in seamless vessel
sections or for thickness of seamless 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.

No changes for UW-12(d) from 1995 till now..... Did you notice that E can be either 1.0 or 0.85 for seamless heads?

For a two piece head with full RT apply UW-11(a)(5) and you will understand how to apply the Joint Efficiency.

There are three kinds of people in this world; those who can count and those who can't.

 

[jproj]

Thanks for the clarification and sorry for the typo in my first sentence (JE = 1 with spot RT & 0.85 without spot for seamless heads). I think I understand it now.

Thanks again!

jproj

 

[Shmulik]

thread794-187564

 

[jproj]

I have another question regarding the joint efficiency of circumferential seams between shell sections (not seamless) when radiography is not performed. Since UW-11(a)(5) does not apply, is it accurate to say that the circ. seam between two shell sections (not seamless) is per Table UW-12(c) (JE = 0.70 for Type 1 welds)?

Thanks in advance!

jproj

 

[eliebl]

jproj,

The joint efficiency for the circumferential seam would be 0.7 for a type 1 weld. It is unlikely to govern the design as it is used in the longitudinal stress calculations. If the two shell sections (or shell and head) were seamless this would still apply. There is an interpretation to this effect but I do not know the number off hand.

Regards,
EJL

 

[jproj]

EJL,

UW-12(d) would apply for seamless shell sections would it not (JE = 0.85 for no RT)?

(d) Seamless vessel sections or heads shall be considered equivalent to welded parts of the same geometry in which all Category A welds are Type No. 1. For calculations involving circumferential stress in seamless vessel sections or for thickness of seamless heads, E = 1.0 when the spot requirements of UW-11(a)(5)(b) are met. E=0.85 when spot radiography requirements of UW-11(a)(5)(b) are not met, or when category A or B welds connecting seamless vessel sections or heads are Type No. 3, 4, 5, or 6 of Table UW-12.

jproj

 

[eliebl]

jproj,

The joint efficiency of 0.85 would be used when calculating the circumferential stress as it is more analagous to a quality factor. That is one area where the code uses the same term with two different meanings. The E =0.7 would be used for equation 2 on page 18 of Section VIII-1 whereas the E=0.85 would be used in equation 1 and the head thickness calculations in UG-32. The only place where the E=0.7 could make a difference is if the UG-22 loadings resulted in the longitudinal stress governing the design. This is unlikely as the longitudinal stresses are hald fo the cifcumferential stresses.

This is one of those items which I found to be poorly understood when I did design review for a AIA.

Regards,
EJL

 

[CodeRef]

One key point I found and initially overlooked early in my career when deciphering UW-11 was this:

Calculations involving circumfirential stress implies longitudinal joints.
Calculations involving longitudinal stress implies circumfirential joints.

Additionally, understand UW-3 and Figure UW-3 (especially speherical heads)


There are three kinds of people in this world; those who can count and those who can't.

 

[lotoo1]

I am not certain which joint efficiency number to use for the following vessel:
Aluminum SB209 5454 alloy, 35 psi, temp. 200 F. Seamless torispheriacl head, lapp welded. 3 course shell sections butt welded. No RT.

For the shell thickness calculation do I use 0.85 as the joint efficiency for the circumferential stress and 0.7 for the longitudinal stress. Is the joint efficiency 1.0 for the seamless hed thickness calculation.

 

[CodeRef]

Consult with your AI...

There are three kinds of people in this world; those who can count and those who can't.