Appendix 2 Application for Large, Low-Pressure Flange Design: Issue with H/H0 factor 1

[wkg332]

Hello! I am a long-time viewer and first-time poster. I am working on a tool to design loose type flanges (corresponding to sketch (3a in figure 2-4) and integral type flanges (corresponding to sketch 8 in figure 2-4) > 36" ID for low pressure applications with a maximum pressure of 5 psi. The weld size is 1/4", and the pipe size is 1/4". The goal of this work is to decrease the cost of large diameter flanges for extremely low pressures.

My calculations show that for these flanges, the h/h0 constant is always below 0.10, sometimes as low as 0.05. My question is:
1. Is there a lower limit on the h/h0 value, after which point appendix 2 is no longer the appropriate design method to use for a flange?
2. Can the equations in table 2-7.1 be used to generate meaningful F, FL, V and VL values for flanges with h/h0 values that are below the ranges on figures 2-7.3 and 2-7.5?

 

[SnTMan]

wkg332, from what I understand of your designs I think I'd side step those issues and just design as loose type flanges without consideratipn of the hub, see 2-7(b). Such flanges would be per sketch 3(a), simple rings with two fillet welds.

For large, low pressure flanges the seating conditiopn will likely govern, depending on the gasket used. You will need to pay attend to bolt spacing, see 2-6, eqn (7) and 2-5(d) eqn (3). You should pay attention to flange rigidity as well, 2-14. Failing that you should apply an old rule of thumb that flange thickness not be less than sqrt(ID/10).

For some of the figures, ratios of h/ho < 0.1 are shown (2-7.4, 2-7.6) while for others they are not. If for some reason I was compelled to consider the hub then I think I'd insure h/ho was not less than 0.1, eliminating the concern. Frankly, doesn't seem worth the bother to me.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SnTMan]

A further thought: If you are not Code stamping, you can kind of do as you like

The problem with sloppy work is that the supply FAR EXCEEDS the demand