Nozzle opening calculations
Nozzle opening calculations
(OP)
Hi
I am wondering how to consider an opening in a pipe manifold.
I have a 12"NB pipe manifold that at the end terminates with a standard pipe cap. However, what I wish to do is cut a 6" i/dia hole centrally in the 12"NB pipe cap, then weld a 8"NB pipe onto the pipecap in such that the 6" hole in the pipe cap acts as a restrictor orifice, and the 8" pipe acts as a continuation of the manifold to elsewhere.
Flow would then pass along the 12"NB pipe through the 6" hole and exit into the 8" discharge pipe.
I am aware that I would need to do some reinforcement calculations if this were a classic nozzle opening, however, in this case I am unsure of how to apply code rules, or even if they apply in such a case.
I do know that normally you wouldn't put an 8"NB nozzle into an 12"NB cap, however, this seems an elegant cheat, but perhaps not a legitimate one.
Any ideas / advice would help.
I am wondering how to consider an opening in a pipe manifold.
I have a 12"NB pipe manifold that at the end terminates with a standard pipe cap. However, what I wish to do is cut a 6" i/dia hole centrally in the 12"NB pipe cap, then weld a 8"NB pipe onto the pipecap in such that the 6" hole in the pipe cap acts as a restrictor orifice, and the 8" pipe acts as a continuation of the manifold to elsewhere.
Flow would then pass along the 12"NB pipe through the 6" hole and exit into the 8" discharge pipe.
I am aware that I would need to do some reinforcement calculations if this were a classic nozzle opening, however, in this case I am unsure of how to apply code rules, or even if they apply in such a case.
I do know that normally you wouldn't put an 8"NB nozzle into an 12"NB cap, however, this seems an elegant cheat, but perhaps not a legitimate one.
Any ideas / advice would help.





RE: Nozzle opening calculations
I ignored the 6" hole and considered it as 8".
The bigger the hole the more reinforcement that's required so I've also taken the assumption that using the bigger of the two values is the conservative option.
RE: Nozzle opening calculations
Further comments/ corrections most welcome.
RE: Nozzle opening calculations
B&PV code may prohibit an opening in a head this large, or have special design requirements for it, but there again, it would vary by code and application.
RE: Nozzle opening calculations
@JStephen: Thanks for reminding me, you are correct: we can utilize excess thickness available in the shell at least to partly compensate for the loss in the opening, such that only the balance of mass needs to be made-up by way of the pad. [speaking in terms of the BPV Code]
RE: Nozzle opening calculations
Regards,
Mike
RE: Nozzle opening calculations
I will check the excess in the shell and nozzle, hopefully they will give me the required numbers.
As a thought, in this situation if my orifice hole were very small, say 1/4", rather than 6" would that affect the way people thought of this problem ?
RE: Nozzle opening calculations
I don't think there is any problem with doing such a thing, its just that most canned programs will not handle the various dimensions properly in the calculations.
However if the "finished opening diamater" is very small, the actual attachement may be outside the limits of reinforcement. Again if the calculations are done properly and the design meets Code in all other respects, I don't see any real problem.
Regards,
Mike
RE: Nozzle opening calculations
The Code does not prohibit your design / arrangement. It is only to solve the process probems (hydraulic calcs, cavitation, erosion, pressure drop, design pressure and design temperature, etc) and the mechanical problems (estimate the loads on the 8" nozzle / pipe extension, calculate the stresses at the junction with the cap and compare with the limits set in WRC 107 or BS 5500). Estimate the required / available reinforcement and weld-in the pad, if required. If needed, you can include vibration analysis or any additional external loads you can imagine (and quantify), all this is acceptable per any PV Code, provided that the allowable stresses set in the Code are not exceeded.
RE: Nozzle opening calculations
then you can cut and inset the 6in with full penetration and if still need reinforcing, you reinforce it, so what?
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genb