Reducing Flange Dimensions

[PrudhoeBayAK]

Is there a good website out there with a table of available reducing flange combinations, and standard dimensions?

Is a 12" x 6" ANSI 150# RF Weldneck reducing flange available?

Thanks!

 

[TerryOsser]

ASME B16.5 doesnt mention WELDNECK reducing flanges, only THREADED and SLIP-ON (see page 69). From this my assumption is that the standard intimates that WELDNECK reducing flanges are not covered by the standard. No reason why you couldnt use a flanged reducer though.

 

[DLANDISSR]

PrudhoeBayAK:
Could you use a reducer and a weld neck or a reducer and a slip-on?

 

[paddymac]

If you need to reduce down in the thickness of a flange, you will either have to use a PTFE reducing flange (might be unacceptable in some situations) or you could use a blind flange and drill it to suit inserting a 6" pipe into it (not normally used in the horizontal because of creating a dead-leg, normally only used in the vertical when there are space restraints and standard reducers are too large)

 

[Scipio]

If you've got the space, I'd use a butt-weld reducer, eccentric or concentric, depending on flow direction, with weld neck flanges welded on. Remember that a sudden change in piping diameter can have a significant impact on hydraulics. As a rule, I wouldn't use a reducing flange on anything larger than 1-1/2" on the reduced end.

Also be very careful if you're going to try drilling a blind like paddymac suggested, if this is going into code pressure piping. It is permissable by code, however only certain combinations are possible with a standard blind. If memory serves, the largest reduction you can make by drilling a NPS 12 blind flange is NPS 4. Larger than that, you have to use a hub blind to ensure there's enough material left on the blind to meet the pressure rating.

Note, this is a code issue, addressed in ANSI B16.5, which you should confirm what you're doing with - they've actually got a nice little table setting out the available reductions, but you have to start with a proper (normal or hub, depending on reduction) blind. You drill a hole in a blind flange that doesn't meet that code, and without calculations to back it you could be on your way to court.