Yes.

The flat face flange is shorter through the neck by the thickness of the raised face which has been removed to make it into a flat face.

The thickness of the face removed depends upon the pressure class of the flange, as different pressure classes have different face thicknesses.

The previous commenter is correct but in only some cases. This happens on Valves as well as Weld-Neck (and other) Flanges and it all depends on how the Flat Face surface on the object was created.

If the Flat Face Weld-Neck Flange (or Valve) was created by modifing an existing Raised Face item then he is correct.

However some items (Weld-Neck Flanges and Valves) are created as "Flat Face" in the factory during original manufacturing. When this is done then the Face-to-Face dimension for Raised Face Valves and Flat Face Valves is the same. This is because the creation of the raised face part of the flange face is a second operation (not a primary operation).

If the dimensioning is critical then to be safe you may wantd to check with your flange (or Valve) supplier to confirm the actual dimensions.

In a bind I have turned down a raised face on the lathe to fit a flat face valve or another flat face flange. I think all flanges are forged to be flat and then machined into what ever they will be.(as been stated already)The difference in dimensions are so small that it can easily be made up by a little wider root gap on the next few fits. On allot of burner management pipe skids we make in the shop have the flat face cast iron FM rated valves so we have to be careful to not get the flanges welded to the wrong end of a spool piece. There is nothing worse to find out when it is time to bolt everything together after it has been to the paint shop that we did this. They make a spacer ring for raised face flanges so they will fit up to flat face flanges. If you use a raised face on a flat face cast iron valve you run the risk of cracking it when tightening the bolts. Same thing if you don't use a full face gasket with the flat face flanges.

pipewelder