PN16 Raised Face Diameter too small

[MJL14]

I have recently imported a number of DN100 PN16 raised face flanges in stainless steel. The diameter of the raised face should be 158 mm (+2.0/-1.0) but it has come in undersized at 150/151 mm. The rest of the flange is dimensionally correct and the finish on the raised face is perfectly machined. There is even enough material on the overall thickness of the flange to machine the raised face down, thus increasing the diameter, but only by 2 of 3 mm. This would still mean that the diameter is undersized.

My question is: how critical is the face to face diameter in terms of mating via gasket. In other words, the undersized raised face that I have received (150.0mm) will ultimately be mating up to other DN100 PN16 flanges where the raised face is 157/158mm. Will the difference in diameter effect the performance of the seal?

I appreciate we have standards and tolerances for a reason but I may have to consider requesting a concession in this instance.

The standard I am working to is BSEN1092-1 (latest edition)

Mike Lomax

 

[XL83NL]

Hi Mike, if you really want to know, perform a calculation, e.g. per the rules of EN 1591. It’s the current best set of rules for calculating flanges and their sealing. The standard is however quite complex. There are free software tools, also online, to calculate a gasket as well. One I use, which could do the calculation for your case as well (and quite simple), is from Klinger. The tool is called KlingerExpert.

https://ked.klinger.co.at/kd/index_en.xhtml

It doesn’t however calculate the stresses in the flange. Provided there’s a bolt preload that allows a good sealing of the gasket, you still need to verify flange stresses.

To me, your case would be an NCR to the manufacturer. We recently bought a bunch of DN100 PN16 as well. May I ask what material your flanges are made of, and where you bought them (country, maybe the mill)?

 

[MJL14]

Thanks for the link......I'll give it a try.

I have reported the problem back to the manufacturer which may result in complete rejection of all the flanges (which is 700+). The mill is co-operating but the final decision will come from my customer because of the timeline involved. The flanges have been manufactured from ASTM A182 F316/F316L and the country of origin is China. Therefore, the delivery for any replacements will be approximately 8/10 weeks (including seafreight) unless they are prepared to pay for airfreight.

Mike