Spec Break!!-piping

You put a 300# flange where the 150# flange would normally be. Yes this is "going out of spec" but there are exceptions to every Rule.

Thanks.....

Dear peppinjoe,

Please refer to the following CR4 Thread for some details: Connecting Different Types of Flanges.

Hello, Spec. breaks do not always occur at valves/flanges. You can have a spec. change for instance after a point where tee is used in a line and some other fluid is introduced into the system. It could be on a water line that changes spec after acid is added to change the Ph of the water as an example. I have seen changed specs in the middle of a pipe line from stainless steel to carbon steel and have a bi metal weld instead of a set of dissimilar material flanges. I have also seen in 850 to 150 steam pressure reducing valves that the spec does not change at the valve but rather down stream after the de-superheater, They do this because although the pressure changes at the valve the heat will not drop till after the de-superheater and the need for chrome-moly spec will continue to the point where the steam is cool enough to be safely held in a lower spec material. I have actually just finished a pipe replacement in this exact scenario. We made the chrome moly to carbon steel bi metal weld several feet down from the de-superheater. If you find your self having a spec. change at a valve as normal you should as a rule always use the higher rated flange on the lower spec. side of the valve instead of the lower rated flange on the higher spec. side if this makes since.

pipewelder