Thickness for rolled, bent and welded elbow 1

[jtseng123]

Dear all,

For a 36" eblow at the bottom head out of the skirt, vendor will buy plate, roll, bend and weld. Thickness is around 1" thick, 304 SS.

Vendor is citing UG-44 that ASME B16.9/B16.11 fitting shall be calculated as for straight seamless pipe as follows:

Design thickness, (at 150 °F) Appendix 1-1
t = P*Ro / (S*E + 0.40*P) + Corrosion
= 1,100*18 / (20,000*1.00 + 0.40*1,100) + 0
= 0.9687"

Questions:
(1)Shall I request vendor this elbow must meet B16.9 so UG-44 using straight pipe is applicable ? Or it does not matter ?

(2) B31.3 Clause 304.2.1, formula for thickness of pipe bend can be greater than Div 1 using straight pipe. Shall I ask vendor to follow B31.3 as well and provide thicker elbow even this elbow is within Div 1 boundary ?

(3) If I accept the thinner elbow per Div 1, pipe stress engineer will model external pipe together with this elbow under B31.3. They may find out the elbow thickness is not sufficient per B31.3. Shall I tell them it is Div 1 elbow, live with it ?

 

[racookpe1978]

OK.

If it looks like an elbow, is shaped like an elbow, and is expected to resist internal pressure like an elbow, should it not be calculated against stress like an elbow - regardless of how it is fabricated?

For example, if it were somehow machined from a single forged billet of steel into an elbow 30 inch OD, would you not require the stress analysis to be equal to that of a conventional ASME elbow?

 

[metengr]

For a 36" eblow at the bottom head out of the skirt, vendor will buy plate, roll, bend and weld. Thickness is around 1" thick, 304 SS.

Vendor is citing UG-44 that ASME B16.9/B16.11 fitting shall be calculated as for straight seamless pipe

Instead of citing UG-44, the elbow should be supplied under ASME B16.9.

 

[metengr]

Also, have the vendor review SA 403 because this is directly applicable.