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Class 900 flanges less than 3" NPD

Class 900 flanges less than 3" NPD

Class 900 flanges less than 3" NPD

(OP)
Since B16.5 has a note in the Class 900 dimension table to use the Class 1500 dimensions for 1/2" thru 2-1/2" sizes does that mean there is no such thing as a 2" Class 900 flange?

Also, I guess you would never use the Class 900 pressure / temperature ratings for flange sizes less than 3".

Any thoughts on this subject?

thanks
mark

RE: Class 900 flanges less than 3" NPD

This question has been asked and answered before (possibly many times).

It is a case of economics.  The dimensional difference between these small high pressure flanges would be so small that it does not pay the manufacturers to make all the different ratings.  So, they consolidate the sizes to the higher pressure and thus reduce the number of different forging patterns they need and the different machining they need.
The Codes governing the flanges have endorsed and adopted this logic.

Experienced Pipers the world over accept this, beginner pipers should have been taught this in their class on Flanges.  

RE: Class 900 flanges less than 3" NPD

(OP)
I am the author of our pipe spec and I do not include small bore Class 900 flanges.  I am looking for info to convince our valve and aux equipment engineers that they should not specify small bore flanged valves or nozzles with a Class 900 rating.

I guess I should have asked if the Class 900 items exist, or will they all be stamped as Class 1500.

thanks
mark

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