UW-11(a)(5)(b)/UW-12(d) - Type (2) Joggled Heads

[Rmclach]

I have the following design scenario:

Two seamless Type No. 2 joggled heads with one plate offset being welded to a rolled cylindrical shell that has a long seam.

Per UW-12(d), thickness calculations of seamless heads can use a value of E=1.0 when Spot RT per UW-11(a)(5)(b) is met and E=0.85 when Spot RT is not met. UW-12(d) applies to Type No. 1 and Type No. 2 joints.

My questions are:
(1) Do the values presented in UW-12(d) override those listed in Table 12 for Type No. 2 joints?
(2) In order to meet Spot RT per UW-11(a)(5)(b) and in fact use E=1.0, am I required to complete a spot RT shot for each of the head to shell circumferential seams of the respective vessel OR is one shot sufficient for both circumferential seams (or more for identical vessels) if the increment is less than 50ft and there is only one welder/welding operator?

Ryan

 

[SnTMan]

Rmclach, what is a "Type No. 2 joggled head"? I see no such designation in the Code. Sketch of the proposed construction would be most helpful.

In general if spot RT is used at the round seam to give the head E = 1.0, then that spot cannot be used to satisfy spot requirements for the rest of the vessel as per UW-11(a)(5)(b).

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Rmclach]

My apologies. The head to shell joint is per Figure UW-13.1 sketch (i). The industry name for that type of head is semi-elliptical with a joggled edge.

I tend to agree with you on your statement that the spot cannot be used to satisfy other spot requirements for the rest of the vessel. However, UW-11(a)(5)(b) says, "as a minimum, meet the requirements for spot radiography in accordance with UW-52." And UW-52 specifies the minimum extent of examination, i.e. 50 ft increments per welder/welding operator.

Regards,

Ryan

 

[SnTMan]

Rmclach, apology not needed I agree, Type 2 joint per UW-12. Looks to me as if E = 0.8 is all you're going to get for this seam, if spotted. This of course is for longitudinal stress, and I agree, if this seam is spotted, E for head is 1.0, if seamless.

Last sentence of UW-11(a)(5)(b) governs: "Spot radiographs required by this paragraph shall not be used to satisfy the spot radiography rules as applied to any other weld increment". Meaning, if you make use of UW-12(d) which invokes UW-11(a)(5)(b), then that shot can be used for that seam only.

Is your shell seamless or does it have a long seam?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Rmclach]

The shell has a long seam in it. I work for a manufacturer that mass produces vessels and I was debating on whether or not there was any benefit to applying the rules of UW-12(d) / UW-11(a)(5)(b) to use an efficiency of E=1.0. I was under the impression that it was required for each seam as well which does not sound worthwhile for us.

Thanks,

Ryan

 

[chicopee]

Obviously, you have copies of the unfired pressure vessel code which tends to be overwhelming when you try to figure out some particular aspects. To simplify all the innuendoes get a copy R.Chuse and S.M. Eber text "Pressure Vessel-the ASME code simplified". The question that you have is pretty covered in numerous illustrations with notes.

 

[Rmclach]

I will definitely take a look for that textbook. Thank you for the recommendation Chicopee.