What are Buttweld Fittings?

Buttweld Fittings:

These are?pipe fittings used to?change the pathway of a pipeline, which is also known as ‘elbows'. It reduces or increases the pipe bore size which is reducers.

Buttweld fittings have the below-mentioned advantages:

• Limiting pressure reductions and the turbulence?inside the pipeline
• Allow strong, leak-proof, and piping connections
• Relatively cheap to execute
• Long service life

The?branch within the butt-weld is called tees and cross.

If it is to blind a pipeline it is called ‘butt-weld cap’.

American Society for Mechanical Engineers (ASME B16.9) covers Butt weld fittings.

Manufacturers Standardization Society MSS-SP 43, also is a point of reference.

For piping that is 2” and more in diameter Butt weld fittings are implemented.

Socket weld and threaded fittings are used?for smaller size pipes; refer to ASME B16.11

?Buttweld fittings are in various shapes which are;?

1.??????Elbows

2.??????Reducers

3.???????Crosses,

4.???????Tees

5.???????Caps

6.???????Stub-ends

Buttweld?material grades?are;

1.??????Carbon,

2.???????High-yield carbon

3.???????Low-alloy

4.??????Stainless

5.???????Duplex

6.???????Nickel alloys

?These are of sizes between 2 and 24 inches in seamless piping and welded for bigger pipe sizes.

Buttweld fittings’ key specifications are ASME B16.9; carbon and alloy fittings

MSS SP 43 integrates ASME B16.9 for stainless steel, duplex,?and nickel alloy BW fittings.

For piping systems below 2 inches in diameter,?Socket weld and threaded (forged) fittings are generally used (ASME B16.11).

Socket-weld and threaded (forged) fittings are used for piping systems which are under 2’’

Butt-weld Elbows

45 degrees

90 degrees

180 degrees B16.9 butt-weld elbows are manufactured in a wide range of dimensions (combinations of To adhere to ASME B36.10 and ASME B36.19 standards; carbon, alloy, and stainless-steel pipes sizes from 2’’ to 48’’, ASME B16.9 butt-weld elbows are produced in an array of dimensions, a mix of outside diameter and thickness of the wall.

Buttweld elbows below 24 inches in diameter are produced by cutting, heating, and bending seamless steel pipes; pipe elbows of larger sizes are manufactured, instead, from welded pipes or steel plates.?

Larger size butt weld elbows are fabricated from welded pipes/steel pipes. Buttweld elbows 24’’ or lower diameter are manufactured by cutting, heating, and bending seamless pipes.

The three most commonly used elbows in piping are the 45’’, 90’’ & 180’’. The 180’’ pipe elbows are known as ‘return elbow’.

Special types of pipe elbows are reducing elbows and mitered elbows.

Reducers/Reducing elbows:

Reducer using to reduce the diameter of a straight run of pipe, a reducing fitting must be used. The reducer is available in two styles.

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?Concentric: having a common centreline.

?Eccentric: having offset centreline.

?The concentric reducer maintains the same centreline at both the large and small ends of the fitting. Normally, this type of pipe reducer is used to modify the diameter of the pipeline by two or three measures, to avoid an excessive pressure drop in the pipeline.

The eccentric reducer has offset centrelines that will maintain a flat side on the top or the bottom of the fitting depending on how the fitting is called before welding.

?Normally, this type of pipe reducer is used for pipelines deployed in a horizontal position.

However, concentric reducers are used for pipelines laid vertically or for the inlets of suction pumps, as top flat eccentric reducers.

Top and bottom flat eccentric Reducers:

Eccentric reducers can be top flat, “TF” or bottom flat, “BF”

The bottom flat eccentric reducer type is used for pipe-racks (the bottom of the reducer is flat and at the same level of the bigger sized run pipe), while the top flat pipe reducer type is used at the inlet of piping suction pumps as shown in the image below (this setup prevents the formation of vapor traps in the pipeline):

Concentric & Eccentric Reducers:

The key difference between concentric and eccentric reducers is the centricity of the inlet versus the outlet of the fitting, which is perfect for a concentric reducer?and offset of an eccentric reducer.

Buttweld Reducer Manufacturing Process:

Cold forming is the most common manufacturing process for seamless eccentric/concentric reducers (welded reducers are produced with the single or double seam weld process):

Mitered Elbow:

The mitered elbow is not an actual fitting, but instead is a manufactured turn in the piping system. This elbow is made by making angular cuts in a straight run of pipe and then welding the cuts together after they have been rolled to a different angle. The mitered Elbow may be classified as 1, 2,3, or 4 weld miters. The number of welds used depends on the smoothness of flow required through the turn. A 2-weld miter will create more turbulence within the pipe than it will with a 4-weld miter.

?Short and long radius Elbow:

The centre to face distance of a long radius pipe elbow is always 1.5?times the?nominal pipe size, whereas, for a short radius pipe elbow, the centre to face distance is equal to the nominal pipe size.

Pipe Elbow Manufacturing Process:

Buttweld elbows of 45 and 90 degrees can be manufactured in different ways, the main ones are the “mandrel process” and the “cold forming” (other methods are the elliptical forming and the double-seam welding method).

There are the elliptical forming and the double-seam welding processes too.

Pipe Bends:

A pipe bend is a typical term to indicate a fitting that changes the direction of the piping system.

Elbows are pipe bends too but of a standardized type, in terms of angle degree and direction.

Pipe bends are manufactured by twisting a pipe or a tube using a bending machine, with a hot or cold-forming process. Pipe bends are economical ways of making pipe works layouts decreasing the number of other pipe fittings used.

Buttweld Tee:

?The name of this fitting comes from its resemblance to the letter T.?It is a three-way fitting used to make perpendicular connections to a pipe. Lines that connect to the main run pipe are known as branches. The main run of pipe is often called the header.

?The weld Tee requires three welds to be made to install the fitting. Two types of Tees are used in the piping industry.

?Straight & Equal Tee; all three outlets are at the same bore size. This is a?butt weld fitting used to branch a pipeline, or any other pipework, at 90 degrees.

Equal tees are available in sizes from half an inch to 48 inches (or larger) and in seamless and welded execution (seamless up to 24 inches, welded for tee sizes above 24 inches).

Reducing Tee; branch outlet is a smaller pipe size which reduces from the run of pipe.

In case a larger bore size reduction is necessary, then a reinforced branch connection, known as Weldolet, may be opted to prevent turbulence and have a smoother flow reduction.

Buttweld tees are manufactured according to ASME B16.9 (carbon and alloy) and MSS-SP 43 (stainless steel and nickel alloy).

The standard dimensions and tolerances of equal and reducing pipe tees are covered by the ASME B16.19 specification (carbon and alloy steel) and by the MSS-SP 43 spec (for stainless steel and nickel alloys tees).

Barred Tee

A barred tee is a special?type of equal tee used for pigging operations.

A barred tee exhibits a welded obstruction on the branch pipe side, that prevents the pig from flowing from the run pipe into the branched pipe.

Weld Tee:

?The name of this fitting comes from its resemblance to the letter T.?It is a three-way fitting used to make perpendicular connections to a pipe. Lines that connect to the main run of pipe are known as branches.

The main run of pipe is often called the header.

?Pipe headers may have two branch connections. The weld Tee requires three welds to be made to install the fitting.

?Two types of Tees are used in the piping industry.

Straight; all three outlets are the same pipe size.

Reducing; branch outlet is a smaller pipe size reduces.

?Pipe Nipples:

?By design, screwed and socket weld fittings cannot be assembled by placing one fitting directly in contact with another fitting. Screwed fittings are manufactured with threads on the inside of the fitting and socket weld fittings to have an internal socket that prevents fitting that makes up the assembly. To facilitate the assembly of screwed and socket weld fittings, a small length of pipe called pipe nipples are used between fittings.???????

?Swages:

?Swages are functionally similar to reducers but are specifically designed for screwed and socket weld pipe. Screwed swages have male (external) threats and can be connected to other screwed fittings without the use of a pipe nipple. They are used to make reductions in the line size on a straight run of pipe. Swages, like reducers, are available in either a concentric or eccentric shape.

Screwed swages will have thread ends (TE), socket weld swages plain ends (PE) and butt weld swages have bevelled ends (BE). When specifying a swage use the following abbreviations:

BBE Bevel Both Ends

TBE Thread Both Ends

PBE Plain Both Ends

BLE/ TSE Bevel Large End/ Thread Small End

PLE/TSE Plain Large End/Thread Small End

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For more information, please contact JSS; [email protected] or call on +97148053900