Flange Ratings and Bolt Patterns 2

[phllp581]

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?

 

[LittleInch]

Easy one -

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.

 

[pennpiper]

phllp581,
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

 

[11echo]

WELL splitting hairs here, you can bolt up a 125# flange to a 150# flange, and 250# to a 300#. But as everyone so far has indicated, in general NO you can't. BUT pressing farther, there are times when you have a piece of equipment that has say a 300# flange, but a 150# piping system needs to "bolt-up" to it. This is done by breaking the piping spec. at that point with the 300# flange, then from that point on go with the 150# piping spec you want to use. All you need to do now is note the spec. break on the drawings involved.

 

[rconner]

Really splitting frog hairs here, and the first responses were right; however, for many years some suppliers have in effect been furnishing adapting pipes or fittings for some applications by putting a 300# (or F&D 250 per B16.1) flange on one end and an F&D 125 or 150lb drilled flange on the other. [It can even be done e.g. in appropriate water and wastewater applications in a quite short laying dimension using a special one piece "Adaptor" (in appearance a little like a flange filler with different drillings or tappings either side) e.g. as pictured at

http://www.american-usa.com/product...ed-items/flange-adaptors/standard-dimensions.

]

 

[1gibson]

And while we're at it, another fun fact is if you are in B16.47 territory (larger than 24") you need to make sure you have the same series (A or B) because they have different bolt circles/number/size of bolts. So for example, a "30" A106 gr.B 150# B16.47 RFWN flange" is not a complete specification, because it doesn't say series A or B.

 

[MickMc]

Another while we are at it, in my experience it is normal practice to include Class 300 flanges in Class 150 Specifications to mate to control valves etc which are are normally Class 300 minimum and in some cases equipment nozzles and consequently no spec break.

 

[curtis2004]

MickMc,

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

 

[MickMc]

Curtis,

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.