B31.3 Nozzle Calculations through B16.9 Pipe Cap
B31.3 Nozzle Calculations through B16.9 Pipe Cap
(OP)
I am doing a design which requires a 3" Sch 40 nozzle to extend through (along the axis)of an 8" Sch 40 B16.9 Pipe Cap. I understand the branch calculations in B31.3 for run pipe, but how do I apply them to a pipe cap? Also, I want to install a 1/4" coupling as a drain in the pipe cap beside the 3" pipe. How do I calculate that, and how close can I place the drain to the 3" pipe.





RE: B31.3 Nozzle Calculations through B16.9 Pipe Cap
I would encourage you to remove the cap and use reducers to get the result you are trying to attain.
Since I will assime you will not do that, I would encourage you to very closely study B31.3, Paragraph 304.4.2, "Openings in Closures", as well as that paragraph's references to the ASME B&PV Code. The drain should be placed on the NPS 8 pipe - it would be bad practice to do otherwise. However, if the coupling is installed in the cap, it should be outside the "reinforcing zone" around the opening made for the NPS 3 pipe.
There are complications when making openings in B16.9 fittings that may not be apparent. The fittings are subjected to stresses other than the circumferential stresses that pipe (cylinder) wall thickness minimums are designed for. That is to say the cap may need more thickness than the pipe for a given pressure. So when applying the area replacement rules the MEASURED thickness of the cap (it is not a "standardized dimension in B16.9) should be used to calculate the amount of metal area (if any) that needs to be replaced.
Best regards, John.
RE: B31.3 Nozzle Calculations through B16.9 Pipe Cap
remove the cap and install a weld neck flange and blind (you'll have to figure out the rating and im assuming its not 600# either and the matl is not exotic). drill the blind and stick a 3nps weldolet where u connect your 3 nps spool.
if youre worried that the hole may reduce the flange rating, u may caheck out the stress using the roark handbook (donut plate).
RE: B31.3 Nozzle Calculations through B16.9 Pipe Cap
The advantage of the FEA is that you can take actual wall thickness and geometry measurements to perform the calculations. The proof test may be easier, but you will need to locate a cap with the same fabrication dimensions(preferably from the same manufacturer) in order to perform the test.
RE: B31.3 Nozzle Calculations through B16.9 Pipe Cap