Abbreviations of flange

Steel flanges must be packed with seaworthy packing method then delivery to customers, usually the packing way include wooden box, wooden pallet, iron & steel cage, iron & steel pallet etc.

Pipe Flange helps to connect piping components in a piping system with the use of bolted connections and gaskets.

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Only the most used flange classes are listed on this page. For more information on flanges and their respective standards, please follow the link below.

ASME B16.5 covers flanges with a nominal size from 1/2" through 24". It also includes classes from ANSI 150 through ANSI 2500. The flanges included in B16.5 are blind, lap joint, socket, slip-on, threaded and weld neck flanges.

ASME B16.47 covers flange with a nominal size of 24" and larger. The flange classes it covers are from ANSI 75 through ANSI 900. The flanges included are blind and weld neck flanges. Additionally, B16.47 has two series of flanges, Series A (similar to ASME MSS SP44) & Series B (similar to API 605). Series A flanges are larger, heavier and have fewer bolt holes. The reason for series A and series B is that both specifications mentioned before were brought together to be covered under ASME B16.47.


There are three primary types of flange facings. Not all facings are available with each end connection. This is based on the design of the flange and design of the piping system. The typical flange facings are:

There are six basic types of flanges and are described by the way the connect to the piping system. Click on the links below to be taken to a page detailing the different types of flanges.

Blind Flange (BF) - These flanges do not have a bore. It is used to blind off a flange or even a valve. When used at the end of a pipe or fitting, it provides an easy to open access for further extension of the pipe. The blind flange and its bolts are stressed more than any other flange.

Lap Joint Flange (LJF) - This flange is used with a lap joint stub end fitting. It is similar to a slip-on flange, but with two differences. The radius and the flat face, both allow the flange to secure against the stub end fitting. This is useful where alignment of bolt holes is difficult, such as with spools to be attached to flanged nozzles of vessels. A lap joint is used in low pressure applications and not suitable where high external of heavy loads are present.

Slip-on Flange (SOF) - Slip-on flanges are designed to slip over the outside of pipe, long-tangent elbows, reducers, and swages. The flange has poor resistance to shock and vibration. It is easier to align than welding neck flange. This flange is ideal for low pressure applications since the strength when under internal pressure is about one third that of a weld neck flange.
Socket Weld Flange (SWF) - This is similar to a slip-on flange, except they have a bored and counter bore. The counter bore allows the pipe to fit into the socket/counter bore. The bore of the flange is the same diameter as the inside of the pipe. These flanges were first designed for small diameter, high pressure pipe.

Threaded Flange (THDF) - It is similar to a slip-on Flange, but has internal threads. It is normally used for low pressure and not used where temperature or stress is very high.

Weld Neck Flange (WNF) - This flange comes in two types, regular and long. The hub of the weld neck is designed to reduce the stress at the base of the flange. Regular weld neck flanges are used with buttweld fittings and long weld neck flanges are usually used with equipment and vessel nozzles. A long weld neck flange is rarely used with pipe. Both types of flanges are bored to match the inside diameter of the pipe or fitting to which it will be welded to. They are suitable where high pressure, extreme temperatures, shear impact and vibratory stresses apply.

There are also a number of specialty flanges:


Flange - ASME B16.36, Orifice Flange (1/2"-24")

Flange - Industry Standard Flange (also called Large Diameter Flange) (26"-larger)

Industry Standard Flanges have no national standard code or are they covered by any governing body.

Flange - AWWA Standard Flange




Flanges are normally manufactured in seven basic ratings: 150 Lb, 300 Lb, 400 Lb, 600 Lb, 900 Lb, 1500 Lb and 2500 Lb. The ratings can be expressed in different ways but mean the same thing - 150 Lb, 150 Lbs, 150# or Class 150.

Each class of flange can handle more pressure than the previous class because of its construction. The higher the class is, the thicker the metal is. Thus a higher pressure can be handled. There a numerous factors that can affect the pressure capability of a flange, such as the type of metal that is used.


The BSI specifications for flanges are: