AIR COOLER HEADER NOZZLE LOAD CALCS

[roca]

I would be interested to hear how others calculate the nozzle loads on a flat header box in accordance with API 661 / ASME VIII - apart from of course using FEA.
Is there a "simple" method for doing this?

 

[bvi]

The loads on the nozzles come from the flexibility analysis of the piping attached to them.

 

[MJCronin]

roca,

cb4 is right....

A computerized "flexibility analysis" is performed on the piping system design. This would include materials, temperatures pressures layout geomety and support locations. A typical computer program used for this purpose is CAESAR-II by the COADE corp. (go to

http://WWW.COADE.COM

fro more information)

One of the results of this analysis are piping reaction loads on the equipment. These loads would be compared to the limits in API-661 to determine if they are acceptable.

If the loads exceed the allowables, the piping stress analyst would suggest a modified piping layout or a new scheme of pipe supports to meet the API Criteria.

Hope that this helps


MJC

 

[roca]

Hi cb4 and MJCronin
Thanks for your replies. I am fully aware of the piping design methods
My question is not related to the piping attached to the coolers. We in the mechanical / static equipment department typically ask vendors to design header box nozzles to take 2 or even 3 imes the loads specified in API 661.
My question is how do others calculate the actual nozzle loads - stresses in the rectangular header box plates? eg for vessesl we use WRC 107 / WRC 297 or BS 5500 Appendix G
Is there a simple method without having to resort to FEA?
Don't other members use air coolers or am I posting this in the wrong place?
Thanks again

 

[bvi]

Not being involved from the air fin cooler supplier side, I could not tell you what they do. However, I can tell you that if you look at it from a nozzle strength stand point, the nozzles are typically way stronger than required for the API 661 loads. Two of the sides of the nozzle typically align with the sides of the box, and if you did a stress analysis, you would find the stresses with the specified loads to be low. I was told, many years ago, that there were/may be other considerations, such as effect on tubes, but I could not tell you that was the fact. If you want a higher load, request or specify it for the vendor, and don't worry about it. I would not try to do an independent stress analysis of the nozzle, independent of the air fin cooler vendor, to qualify it for higher loads.

 

[prex]

You can use the 'trunnion loading' case available in the Roark in the flat plates section. This is for circular plates (simple support and fixed) but may be adapted to your conditions using an equivalent diameter.

prex

http://www.xcalcs.com

Online tools for structural design