Spot RT can mean 2 differnt things. It can be spot in accordance with UW-11(a)(5)(b), this gives a seamless section efficiency of 1, where a spot RT IAW UW-11(b) means a 0.85 on the seam inspected.
In your case you would need a spot IAW UW-11(a)(5)(b) to get the full allowable stress of ERW pipe. That is, the 85% efficiency otherwise it will always be less than 85%. The only way to get an efficiency of 1 in the ASME code is to perform full radiography on the seam or, in the case of seamless sections, spot RT to UW-11(a)(5)(b).
You may even have trouble finding the seam in some pipe.
B31.3 Table 302.3.4 states it is not permissible to increase the E of type 1 or 2 joints. ERW pipe is a type 2 joint. If you cannot increase the E for pipe, how can increase the E for a vessel ?
Thanks nde3rich,
I kind of thought you were looking at another construction code.
In your case, you are using the Longitudinal Weld Joint Quality Factor, Ej as given in B31.3 and trying to apply it to ASME Section VIII-1.
ASME B31.3 utilizes Table 1 (within ASME B31.3) for the material stress value (S) whereas ASME VIII-1 utilizes ASME Section II Part D.
What you will discover is that there is a difference between stress values. ASME B31.3 values are not exactly the same as ASME II-D. Thereby eveyrthing else is affected.
The rules within the ASME Codes are not as consistent as one might expect. Always, Sometimes, Maybe, Except.
My pointing out that the stress values were different between B31.3 and VIII-1 is just one example of how different they can be.....and of course it would be obvious that one is a piping code and the other is a vessel code....
I would have thought the values would be similar if you are going to use ERW pipe to fabricate a pressure vessel shell. My main question was and still is how can spot radiography be used to increase joint E. to 1. I always thought full radiography was the only way to obtain and E of 1.
Closely read paragraphs UW-12(a), UW-12(a), (d), and (e) with reference to UW-11(a)(5).
By performing the additional spot RT mentioned in these paragraphs you increase the relevant JE to "1". But the additional RT is not performed on the seam which obtains the "1" but on the seam that crosses said seam (or seamless shell). The additional spot RT allows you to obtain the full JE of "1" that the seam (either "seamless" or fully RT'd) is able to qualify for.
I was also under the same impression, however this can be done as stated earlier by Code Jackal, reference UW-12.d and UW-12.e Also note the stress value exception you inquired about.
Simply stated in your case the ERW pipe will be given a JE of 1.0 if the adjoining girth seams (cat B&C type 1 only) are spot radiographed per UW-11 a.5.b
To summarize, if you spot radiograph the shell to head seams when using ERW seamed pipe, it is permissible to use a JE of "1" for the shell when calculating Tmin. Do I have it right?
Cmon, now, somebody should ask the obvious question of what one would use for the weld joint efficiency of a one course ERW shell with tubesheets on either end (as in a Heat Exchanger) As you cannot apply the rules of UW-11(a)(5)(b) or UW-12(d).......anyone???....Oh I would ask that you provide a code reference for your answer!!
First - You must use the Code that is mandated by the jurisdiction in which the pressure component is to be installed and operated.
Quote nde3rich:
"B31.3 Table 302.3.4 states it is not permissible to increase the E of type 1 or 2 joints. ERW pipe is a type 2 joint. If you cannot increase the E for pipe, how can increase the E for a vessel ?"
B31.3 does not define "type 1 or type 2 joints". Table 302.3.4 has several illustrations of LONGITUDINAL seam welds. Illustration 1 is a furnace butt weld and illustration 2 is an electric resistance weld. Table 302.3.4 tells you that the longitudinal weld joint quality factor to be used in B31.3 PIPING SYSTEMS, for a ERW is 0.85 and it is not permitted to increase this longitudinal weld joint quality factor by additional examinations. B31.3 does not include rules for the design of Code pressure vessels. NEVER mix the rules from various Code documents.
If you are designing a piping system you MUST use the PIPING CODE mandated by the jurisdiction. If you are designing a pressure vessel you MUST use the Pressure Vessel CODE mandated by the jurisdiction. You do not use the rules of B31.3 to design pressure vessels. If you are unsure of a Code rule fly it by the Authorized Inspector who will have to inspect the pressure vessel for the affixing of the Code "U" stamp.
Some pressure component rules allow increasing the longitudinal weld joint quality factor by additional examinations FOR SOME TYPES OF WELDS. Electric resistance welds are not covered by this rule for good reason. Why do you not use seamless pipe?
UW-12(e) addresses ERW pipe when used as a shell section in ASME VIII-1.
My point is this, when using ERW pipe as the shell of a vessel such as a Heat Exchanger, the efficiency of the shell (ERW Pipe)would be 1.0 when using one shell course and tubesheets on either end. Since there is no Category B or C butt joints associated with the ERW shell that would invoke the requirements of UW-11(a)(5)(b), it is correct to use a joint efficiency E = 1.0 in accordance with UW-12(d) and UW-12(e) when determining the required wall thickness due to internal pressure as required by UG-27 and UG-31.
This is only supported by an interpretation and never addressed specifically in ASME Section VIII-1
