For clarity and ease of understanding, Huaxi Flange suggests you describe your part in this order: Quantity , Size (nominal pipe size) , Pressure Class (150-2500) , Facing (RF, FF, RTJ, ect.) , Type (WN, SO, Threaded, Blind, SW, LJ) , Bore (if SW or WN) , Material. For example: 2EA 4” 300# RFWN STD 304

If so, why can’t I find dimensions for them?

Yes, we sell reducing flanges (WN, SW, SO, Thrd) with the hubs or made from blinds (in the cases of SO or Thrd). B16.5 gives rules for how we do the reductions, but to my knowledge nobody produces the cut sheets. If you consider the various combinations possible it would get quite lengthy.

For reducing flanges with hubs, all dimensions except the Length Thru Hub (or OAL) come straight from the regular flange dimensions.

From the larger size:

OD, Thk, Bolt pattern, RF Dia

From the smaller size:

OD at base of hub

OD at point of weld

IF (dependent on schedule)

Hub height

Using abbreviations found in the catalog, here’s how you can calculate the OAL for a reducing weldneck:

Hub height = L2 – thk [all dims per smaller size]

LTH = Hub height + thk(of larger size) + face height

As an example, for a 4” x 3” 600# RF Red WN XH, one would calculate the LTH as follows: Hub height = 3.25 – 1.25 = 2.00” LTH – 2.00 + 1.50 + 0.25 = 3.75”

We have a joke around the office about the fellow who calls up and asks how much a flange costs. “Depends, which one of the 82 million different configurations do you need?” We do offer expedited service but giving any kind of rule of thumb on cost is hard to do. It really comes down to what material is needed and which processes must be interrupted or ran in overtime. Suffice to say, we will always try to appreciate and understand our customers’ needs and can usually turn parts out in a much quicker manner than “standard lead time” if you truly need it. The one caveat to this is if it takes 5 hours to machine the part, then the quickest we will ever be able to quote is 5 hours. With that in mind, please feel free to ask for the impossible and we’ll quote what we can.

AWWA C207 specifies parameters for the carbon steel. The criteria given allows for A283, A36, A516-70, A105, and A181-60 to be used. Limiting your spec to any singular variant of those materials can double or triple your costs. So for general purposes we recommend leaving the material callout for AWWA carbon steel flanges as “Carbon Steel per AWWA.” You will get a part that meets the design criteria set forth in AWWA and you won’t pay a premium for a “preferred” material.