office info

online catalog

ASME? ANSI? AWWA? API? what is the difference?

                                                 AWWA Ring  API RTJ flange  STEEL Flange es

Several governing specifications exist for a wide variety of industrial steel flanges, and each have their own suitability for our customers’ applications. Here at Texas Flange, our most popular product lines include ASME/ANSI flanges, API flanges, AWWA flanges, and DIN flanges. Lets dive a bit deeper below.

ANSI/ASME flanges – B16.5 and B16.47

The current ANSI/ASME flange specifications of B16.5 and B16.47 trace their roots to the old B16.1 specification from decades past, which consisted primarily of cast iron. This specification in turn was developed from the original AESC/ASA committee B16 in the 1920s. These modern specifications are the result of countless hours of engineering and design to form a standard which could be utilized worldwide. Our most commonly requested flange specification, ANSI/ASME flanges continue to be the most widely used type of steel flange across various industries. The pressure vessel and fabrication sectors use these in abundance in their pressurized applications to retain and transport air, water, and a variety of other chemicals. Often found in refineries, ANSI/ASME flanges are a critical component in their infrastructure, and are primarily used to connect piping, valves, and other fittings which compose the bulk of a piping assembly. The 150# class of steel flanges is the most popular for low pressure and vacuum applications, as the design has proven to be effective in applications which require an occasional fluctuation in the temperature and pressure of the environment.

API flanges – 6B and 6BX

A standard developed for the American Petroleum Institute, the API 6A specification shares many characteristics with ANSI/ASME flanges. They are dimensionally similar, however their minimal design requirements for operating pressure begin in the 2000# class, which is derived from the ASME/ANSI 600# class. Certain jobs require the use of pressure classes as high as the 6BX 25000#, though this is much less common than the typical 6B range of 5000# and below. All API flanges require ring type joint facings with the proper gaskets for optimal integrity of their application. This higher-pressure base requirement is due to their overwhelmingly popular use in petrochemical / oilfield applications of a volatile nature. Upstream assemblies with API flanges consist of wellheads, drilling equipment, and much more. The downstream sectors of refinery and processing also require these flanges for the development of crude oil into products for the everyday consumer.

AWWA flanges – C207

A specification designed for generally lower pressure applications (300 psi or less), American Water Works Association flanges are the exact opposite of the API flanges and can be found in a variety of assemblies in which temperature is ambient and media is not corrosive. In most cases, this is simply for the transportation of well water and waste water. AWWA C207 steel flanges are usually of a mild carbon steel or stainless variant and are most often either of the ring slip on or blind disc style. Due to their intended design, they do not have ring joint or raised faces, and are typically sealed with rubber gaskets. Due to their cost and weight compared to other flange types, they are also becoming more popular with project work for structural steel types which require mating or filling a gap between existing flanges.

DIN flanges

Across the pond, you will find the Deutsches Institute fur Normung (DIN) flange specification, consisting of a variety of European styles which have been unified into one code for the purpose of commonality. Although much less common than ANSI/ASME steel flanges in the United States, many of our international customers request flanges to these specifications for a variety of applications such as imported steel vessels, cargo ships, and other infrastructure which may consist of metric pipes/valves and European designed equipment. The subset flanges under the DIN standard consist of the same style of flanges in the United States, including the most commonly used slip on flanges, weld neck, flanges, and blind flanges. Adapter flanges can be custom made to end user requirements for the mating of American flanges to international ones, however we find it is a much more common and easy solution to provide DIN flanges to mate to existing equipment.

Although the most popular, Texas Flange provides more than just these flange types. Other specifications include JIS, BSPP, and a variety of other international styles. Call us Monday – Friday 8-5 CST 1-800-826-3801, or email us anytime at This email address is being protected from spambots. You need JavaScript enabled to view it. and we will get started on your inquiry. We have the flange you are looking for and we are always happy to help!

Please check out our online catalog as well as our collection of online drawings.



Continue reading
369 Hits

Quick industry note on waterworks flanges.

AWWA Ring , Flanges, industrial flanges, AWWA blind flange



The American Water Works Association has suspended the utilization of “hub” type flanges in their C207 and associated specifications. All flanges per AWWA specs are either “ring” type slip on flanges or “blind” type flanges. The aforementioned “hub” type flanges as outlined in AWWA C207 Class D and C207 Class E are derived from ASME specifications 125# Lightweight and 125# Slip On, respectively. We will still provide flanges as dual certified to both of these specifications, with the understanding that they will not be manufactured and stamped per the latest update of the AWWA standard.


As is standard from Texas Flange, you may request these flanges in any commercially available material grade you require. The most common are still carbon flanges, mild steel flanges and stainless steel flange variants. Please be advised that while many of these items are available in stock in carbon steel grades, most stainless, chrome, and nickel alloy type flanges are made to order, given the popularity of carbon steel flanges for the majority of water works flange and piping projects. Their lower pressure requirements and ambient temperature operation typically mean a more exotic alloy flange is not required. Any questions or concerns, please feel free to contact any of our trained sales staff here at Texas Flange.

Call us Monday-Friday 8-5 CST 1-800-826-3801, or e-mail us anytime at This email address is being protected from spambots. You need JavaScript enabled to view it..

Don't forget to check out our other free online resources!



Flange Charts/Tables

Continue reading
3828 Hits