Hi all,

I'm working on one of compression skid that there are rectangular special flanges that connecting the bottles (U-stamp required) to the compressor. The client requested calculation on the flange and rectangular neck to vessel including external loads analysis.

The rectangular flanges will be supplied as a package from the compressor and details as below:
a. Rectangular neck configuration as per App 13, Fig.13-2(a)(3), however it comes with 2 stay plates which is similar to Fig.13-2(a)(8)

Refer to App 13, there is no such configuration and would like to ask any alternatives for the neck calculation, as well weld and reinforcement area calculation.

In addition, can we assume rectangular neck as round attachment basing WRC107 shape conversion method to run the analysis for external loads? Alternatively, I could specify rectangular attachment with or without rectangular repad for the analysis.

Appreciate any feedback and advice.

Well CW

You seem to have covered all the angles regarding the nozzle itself, including Appendix 13 (rectangular vessels) and WRC 107 (applied loads). When you have a rectangular nozzle, the opening in the main component (shell or head) is difficult to assess as there area basically no code rules to cover this, especially if you have a long narrow slot. You may have to analyse the nozzles sides as a beam under a uniformly distributed load.

You mention a rectangular flange. The analysis of rectangular flanges is not really covered by our software. They can be tricky in the case of narrow gaskets that are placed inside the bolting positions.

Rectangular flanges are subject to rotation under initial bolting and pressure when narrow gaskets are used. If the flanges have a full face gasket that extends to outer edges of the flanges, rotation is arrested, and the flanges have a good chance of maintaining the pressure. Please (I mean this), ensure that the bolts are closer to the inner edge of the flange, than to the outer edge. This reduces the bolt load, and also reduces the prising effect on the bolts.

Now, if you have a copy of PD 5500, or you can lay your hands on a copy, there is a simple procedure for analysing rectangular flanges. Basically, the flange is designed as a cantilever. If you follow the rules, you should be Ok.

We intend to include this procedure in our software, but we are up to our armpits in alligators at the moment, but we hope to get there.