For clarity and ease of understanding, Texas 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”

That depends entirely on what you are trying to accomplish. If you want a part that is automatically covered under ASME Code, then forget Slip Ons and opt for a Weld Neck from B16.47 Series A or B. If you don’t need to meet code or can run the calculations for your application, then the options open up:

For the Standard 150# drilling we offer the “Class 125/ 150#” series. These are made per B16.1 which is a Cast Iron Spec. We make them most often in Carbon Steel per A105. In addition, we offer them in Stainless 304, 316, and all the other alloys too. Since the spec is for Cast Iron and the applications in industry usually call for another material these are made “per B16.1 Dimensions only.” There is also a much less commonly used Class 250 option available.

There are also 150#, 300#, 400#, 600#, and 900# Slip Ons that were designed by Tube Turns to match the MSS-SP-44 spec (which was almost 100% brought into ANSI B16.47 under Series A.) These were originally designed to meet ASME Code of the time, but quite some time has passed since then and as a result in many cases they do not meet current design criteria. Nevertheless, they are used on a frequent enough basis that we stock the contoured forgings in A105 and do a decent amount of business getting rolled rings to make them in other materials.

We have also been asked to make Slip Ons to match the B16.47 Series B dimensions. For this there is an agreed upon industry standard method that provides no calculations but has garnered wide acceptance. The basic design includes cutting down the weld neck forging and opening the ID.

Still more options remain as Taylor Forge designed many “Boiler Code” flanges that serve to add Slip On options in various classes. These parts are drilled per their design and do not match any other standard. The classes offered are 75, 175, and 350. For the dated information on pressure-temperature allowance see Taylor Forge Catalog 541 or contact us

Finally, the American Waterworks Association (AWWA) under their spec C207 has designs on a series of plate Slip-on flanges in Class B, D, E, and F. They also have hubbed Slip Ons in Class D and E.

The short answer is Series A tend to be larger, heavier, have fewer bolt holes, and costs more. The longer answer is that these were competing specifications that were brought together in B16.47 as is put forth in a note from our catalog: ASME has incorporated most of the MSS-SP44 specification into B16.47 Series A and most of the API 605 Specification into B16.47 series B. They have also added Blinds to these two specs. You may note that these specs only include Weld Necks and Blinds. For Slip Ons over 24” you must refer to either Industry Standard (which are not automatically covered by ASME) or Boiler Code Flanges. If you need help deciding which flange best suits your application, feel free to contact us.


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.


API doesn’t let us publish them in table format. For this reason, we pioneered the concept of the electronic slide rule for API flanges. Check it out here.


The industry standard is to specify “TRUE 40” to distinguish Sch40 bores from Std bores for 12” NPS and larger when the application calls for the heavier wall.

The industry standard is to specify “TRUE 80” to distinguish Sch80 bores from XH bores for 10” NPS and larger when the application calls for the heavier wall.

Normally, when “Sch80” and “Sch40” are used without any other qualifier such as wall thickness or ID, XH and Std bores (respectively) will be supplied.

When Sch40 or 80 are specified followed by a “S” they are automatically assumed to refer to Std and XH respectively.

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.


DSA stands for Double Studded Adaptor. DSAs are designed to join dissimilar endpoints through bolting each side into it. The DSA is faced and partially drilled and tapped to match the flange or the flanged connection on each opposing side. Typically these require additional nuts and bolts, but these are sold separately as particular applications can require non-standard lengths.