ASME B16.5 Flange Interchange

It depends on what codes the installation needs to make.

If there are no codes, and the failure poses no danger to humans and the fasteners fit through the holes you can probably do it.

A better answer would require more facts.

Can you do it? Probably.

Is anyone here going to promise it will be problem free? Absolutely not!

If you choose to do this, it will have to be at your own risk.

This is the OP. I think there is a bit of confusion here. If you look at ASME B16.5 and take the example of 3/4" flange, all the critical dimensions such as the bolt circle diameter, the thickness of flange, the diameter of the raised face are the same. The only difference is in the flange OD which for the customary units is 139.7 and the metric units if 140 mm. Now, this difference is minimal. I was wondering if I could simply join these two flanges.

Thanks

You should simply avoid using imperial (inch) flanges with metric flanges in the first instance, unless it comes under the same ANSI/ASME/BSI/ISO reference.

Where imperial (inch) flanged pipework is being extended and metric type is the only pipework fittings available, use a suitable flange adaptor (Viking Johnson for example).

"Let me tell you the secret that has led me to my goal: my strength lies solely in my tenacity." -- Louis Pasteur

The difference in the diameters is simply a conversion difference between SI and Imp.

Check a 3/4" CL2500 RF Flange - SI is 140mm Flange OD (or 5.510") for the same in Imperial is 5.50" Flange OD (or 139.7mm).

B16.5-2003 is published in both SI and Imperial units because not all manufacturers use both units.

Using the flanges to mate with one another is a non-issue as long as they are infact each built and stamped to B16.5 standards.

Stephen H. Parkes, C.E.T.
Design/Drafting Manager
Larsen D'Amico Mfg. Ltd.
Edmonton AB

I agree with Stephen... I don't think you can get a "metric" or "imperial" flange from stock... you will get simply a 3" 150# flange... don't think the stamping includes the table which it's been machined to.

Thank you Stephen and the other guests. I thought that you should be able to mate two ASME B16.5 flanges of the same nominal size and class, regardless of whether it is made in Imperial units or Metric units because the differences in the dimensions fall within the specified tolerance range. Thank you for the confirmation!

OP

Yes, you can assemble both the flanges as per ASME B16.5 with the same NPS and Rating (Class), where they will match each other in spite of the minor differences in dimensions due to conversion between SI and Customary units.