Hi all,

1) I have a question regarding use of pipe caps for thermal sleeve nozzles where we use two pipes with a clearance of 6 to 12 mm bewteen OD of inner pipe and ID of outer pipe.
I am using pipe cap on the outer pipe and a hole in the pipe cap to run the smaller pipe through it.
MY concern is how to analyse pipe cap based on calculations. Even if i consider pipe cap as a 2:1 Semi-Elliposidal head, the hole size is bigger than 0.5 time the dia of the pipe cap and as per ASME I, this might not be allowed.
I need a way how to justify my design to use pipe caps having a hole in it with a pipe running through it bigger than 0.5 times its diameter.


2) what is the good engineerign practice to use set on nozzles for vessels, any dia range and pressure or shell thickness limitations to consider as a good engineering practice.
Thanks

Hi farid,

Ans:1
For calculation of pipe cap, you can go ahead taking it as Ellipsodal head, thickness calculation of Pipe cap will not be changed because of opening. Only you have to reinforce the opening as per code requirement like you can use Appendix 1-7 of ASME SEC VIII Div.1(Large opening clauses.)

Hi farid

You did a great job of answering this one.

Many thanks ...Ankur Gupta....
If some one can share their point of view for my second question that would be helpful as well..

thanks to all

One more Question , is the pipe tolerance of 12.5% applicable to pipe caps from ASME B16.11 ?

Thanks

Hello Farid

That is an interesting question. According the ASME Section VIII, Division 1, these fitting fall under Table U-3 (page 6 in the 2010 edition). Paragraph UG-11(a)(2) state that such fittings can be used in accordance within the temperature-pressure ratings stated in the Standard, such as ASME B16.11. In such a case, a calculation is not even needed, provided the fitting complies with the temperature-pressure rating.

However, it is common practice to let PV Elite perform the analysis, as the pipe cap has to be included in the 3D model for clarity. When that is the case, the 12-1/2% must be deducted unless the cap has been measured and verified to have a different thickness.

Thanks Ray,

I have just been through appendix 1-7.. but it states that the procedure is as per appendix 1-7 is for Large opening in Cylinderical shells... but in my case the pipe cap is not a shell it is almost like a spherical geometry.. so the question is, can i still apply Appendix 1-7 or 1-10 to my pipe cap large opening?

Thanks

Hello Farid

Appendix 1-7 only applies to cylindrical shells, not heads. You are not limited as to size for nozzles in heads. For heads, the nozzle will be analysed in accordance with UG-37 only.