Nozzle Reinforcing to API 661

[Seeker88]

HI,

I was wondering if anyone could offer advice on the above topic. We fabricate air cooled heat exchangers to API 661 but have recently received requests from clients to start performing nozzle reinforcing calculations as per section 5.1.11 of the code.

Is there software available to perform the nozzle loading calculations or is this only possible with FEA.

Any insight, suggestions and help would be greatly appreciated

Charles

 

[JStephen]

"Nozzle reinforcing calculations" can mean a couple of different things (I'm not familiar with API-661, so I'm speaking in general terms).

Typically, nozzles on pressure vessels, tanks, etc., will have reinforcing pads. This is primarily to reinforce the shell for the material removed at the nozzle location. The calculations involved are just area calculations, and can be conveniently handled by spreadsheet or other means, if you know your minimum thickness, etc.

Nozzles subject to external loads are a different matter. WRC-297 and WRC-107 are the standard references in that case. Some of the PV handbooks also cover such loading in less detail, I believe. Some of the PV design software probably does this type of analysis automatically. Doing it by hand in a general case is a major pain.

In analyzing nozzles subject to external loads, you normally need to know what the loads (plural) are. I've run into customers that wanted me to state the "maximum" load on the nozzle, but the the maximum loads (in 3-directions) and maximum moments (in 3 directions) are all inter-related. In other words, if they can't tell you what the applied loads are, there's not too much point in doing any of this sort of analysis. If stresses calculate out too high, it's ususally up to the piping people to reduce the loads, as there's a limit to what you can reasonably do in terms of stiffening a shell.

 

[Seeker88]

Thanks JStephen,

I perform the normal nozzle loading calculations to appendix G and WRC 107 on cylinderical vessels. API-661 however is a rectangular unit with an air cooler bundle and as such the calculations are performed on flat plates in rectangular headers. Hence the need for the question as there is not to my knowledge any software available to assist me in the calculations.

Many thanks for your assistance

Charles

 

[LSThill]

Hum! Team Members:

Contact Tony Paulin,

http://www.paulin.com

API PRO 661. 661 Pro Header Box Nozzle Analysis for Fin Fan Exchanger.

Leonard Thill