Flange Ratings and Bolt Patterns
Flange Ratings and Bolt Patterns
(OP)
When specifying flanges, is it possible to abut different ANSI ratings to each other (e.g. 150# abutting to a 300#)? Or will there be problems with the bolt pattern, gasket, etc., not fitting correctly?





RE: Flange Ratings and Bolt Patterns
No it is not possible nor accepted. Neither bolt holes or BCD line up.
The only exception is some small (2" and less) #600 / 900 flanges which are the same dimensions, none of the others are the same so that you can't do this accidentally and to provide the correct flange sealing force.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Flange Ratings and Bolt Patterns
LittleInch has given you the correct answers but, what prompted you to ask these questions in the first place?
Sometimes its possible to do all the right things and still get bad results
RE: Flange Ratings and Bolt Patterns
RE: Flange Ratings and Bolt Patterns
RE: Flange Ratings and Bolt Patterns
RE: Flange Ratings and Bolt Patterns
RE: Flange Ratings and Bolt Patterns
Your last comment about using Class 300 flanges within Class 150 spec is very important. You have to show in your P&ID that these are 300# flanges used to connect an equipment (valve, pump, compressor, etc.). You do not need spec break indeed.
I think many people do not realize that process (Pressure & Temperature) will determine pipe class - not equipment. When I was young and saw spec break around Class 300 control valve installed in Class 150 piping system, I was confused. I did not understand why they change piping class before the valve from 150# to 300# and after the valve back from 150# to 300#. I thought there must me something going on inside the valve (some sort of process which increase pressure). I have decided go inside plant and check this "magic valve". It looked exactly the same as another valve installed nearby in the other class 300 system. I have decided to check full description of both valves in the company's database. Both valves were the same - no magic. I have decided to ask senior engineer about this and he explained me everything.
Curtis
RE: Flange Ratings and Bolt Patterns
Correct this will be highlighted on P&ID whether instrument or equipment connection, the inclusion of Class 300 flanges in Class 150 spec is in anticipation of this type of eventuality.