What is a Butt Weld (Buttweld) Fitting?

A buttweld fitting is a weldable pipe fitting that allows for change of direction of flow, to branch off, reduce pipe size or attach auxiliary equipment. Forged Steel buttweld fittings are manufactured in accordance with ANSI / ASME B16.9.

There are many different types of fittings and they are the same in all sizes and schedules as the pipe.

Fittings are divided into three groups:

• Buttweld (BW) fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43.

• Socket Weld (SW) fittings Class 3000, 6000, 9000 are defined in the ASME B16.11 standards.

• Threaded (THD), screwed fittings Class 2000, 3000, 6000 are defined in the ASME B16.11 standards.

Butt weld fittings are available as elbows, tees, caps, reduces and out lets (olets). These fittings are the most common type of fitting and are specified by nominal pipe size and pipe schedule. Buttweld fittings use seamless or as the starting material and are forged (through multiple process) to get he shape of elbows, tees and reducers etc. Just as the pipe is sold from Schedule 10 to Schedule 160, butt weld pipe fittings are sold the same way. Welded butt weld fittings are more common in stainless steel due to cost advantage. Sch 10 fittings are also more common in stainless steel butt weld fitting.

Common material for butt weld fittings are A234 WPB (A & C also available), High Yield Carbon Steel, Stainless Steel 304 and 316 and Nickel Alloys.

Buttweld pipe fittings comprises of long radius elbow, concentric reducer, eccentric reducers and Tees.They are an important part of industrial piping system to change direction, branch off or to mechanically join equipment to the system. Buttweld fittings are sold in nominal pipe sizes with specified pipe schedule. BW fitting’s dimensions and tolerances are defined as per ASME standard B16.9.

Butt Weld fittings are also called Welded Pipe fittings. These welded fittings in carbon steel and stainless steel offer many advantages compared to threaded and socketweld fittings. The later are only available up to 4-inch nominal size whereas butt weld fittings are available in sizes from ½” to 72”. Some of the benefits of Buttweld fittings are;


Types of Butt Weld Pipe Fittings
1. Elbow 90° long radius 2. Elbow 45° 3. Elbow 90° short radius 4. Elbow 180° long radius 5. Elbow 180° short radius 6. Tee straight 7. Tee reducing 8. Reducer concentric 9. Reducer eccentric 10. End cap 11. Lap joint Stub End

 

Welded pipe fittings in carbon steel and stainless steel are the joining components that make possible the assembly of valves, pipes and equipment onto the piping system. Welded fittings compliment pipe flanges in any piping system and allows;

  • Change direction of flow in a piping system
  • Connect or joint pipes and equipment
  • Provide branches, access and takeoffs for auxiliary equipment

A common example using welded pipe fitting is a pipe reduced by concentric reducer, welded to a weld neck flange and connected to an equipment. Figure below represent complete collection of butt welded pipe fitting


Applications of Buttweld Fittings

A piping system using buttweld fittings has many inherent advantages over other forms.

  • Welding a fitting to the pipe means it is permanently leakproof
  • The continuous metal structure formed between pipe and fitting adds strength to the system
  • Smooth inner surface and gradual directional changes reduce pressure losses and turbulence and minimize the action of corrosion and erosion
  • A welded system utilizes a minimum of space

Bevelled Ends

The ends of all buttweld fittings are bevelled, exceeding wall thickness 4 mm for austenitic stainless steel, or 5 mm for ferritic stainless steel. The shape of the bevel depending upon the actual wall thickness. This bevelled ends are needed to be able to make a “Butt weld”.

ASME B16.25 covers the preparation of buttwelding ends of piping components to be joined into a piping system by welding. It includes requirements for welding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and dimensional tolerances). These weld edge preparation requirements are also incorporated into the ASME standards (e.g., B16.9, B16.5, B16.34).


Material and Performance

The most common materials used in fittings produced is carbon steel, stainless steel, cast iron, aluminium, copper, glass, rubber, the various types of plastics, etc..

In addition, fittings, like pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the fitting themselves, which are “lined fittings”.

The material of a fitting is basically set during the choice of the pipe, in most cases, a fitting is of the same material as the pipe.

Buttweld Pipe Fitting Specification & Standards
Welded pipe fittings are made as per ASME spec B16.9. ASME B16.9 covers factory made wrought steel butwelding fittings in sizes 1/2″ to 48″. This standard however does not cover low pressure corrosion resistant buttwelding fittings. See MSS SP-43, Wrought Stainless Steel Butt-Welding Fittings.

Common Materials for Welded Pipe Fittings
Carbon Steel Welded Fitting:
A234 WPB is the most common material used for carbon steel butt welded fittings.

ASTM A234 WPB is the Standard Specification for of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service.

Specifications
  • ASTM: A234 WPB
  • ASME: B16.9, B.11
  • NACE: MRO175
  • MSS: SP-83, SP-95

Chemical Composition%

Grade C Mn P S Si Cr Mo Ni Cu Others
max max
WPB 0.3 0.29-1.06 0.05 0.058 0.1 0.4 0.15 0.4 0.4 V 0.08
(1,2,3,4,5) max min max max max max max
  1. Fittings made from bar or plate may have 0.35 max carbon.
  2. Fittings made from forgings may have 0.35 max Carbon and 0.35 max Silicon with no min.
  3. For each reduction of 0.01% below the specified Carbon maximum, an increase of 0.06% Manganese above the specified maximum will be permitted, up to a maximum of 1.35%.
  4. The sum of Copper, Nickel, Niobium, and Molybdenum shall not exceed 1.00%.
  5. The sum of Niobium and Molybdenum shall not exceed 0.32%.

Stainless Steel Butt Weld Fittings:

Stainless buttweld fittings are available in 316 and 304 grades.

304/ (UNS S30400/S30403)              

Chemical Composition%

C Cr Mn Ni P S Si
MAX MAX MAX MAX MAX
0.035 18.0- 20.0 2.00 8.0-13.0 0.045 0.030 1.00

Tensile Requirements                                 

Tensile Strength:  (KSI) = 60

Yield Strength:  (KSI) = 35

(KSI converts to MPA {Megapascals} by multiplying by 6.895)

316/316L (UNS S31600/S31603)              

Chemical Composition%

C Cr Mn Mo Ni P S Si
MAX MAX Max MAX MAX
0.035 16.0- 18.0 2.00 2.0-3.0 10.0-14.0 0.045 0.030 1.00

Tensile Requirements                                 

Tensile Strength:  (KSI) = 70

Yield Strength:  (KSI) = 25

(KSI converts to MPA {Megapascals} by multiplying by 6.895)

How a Butt Weld Fitting is Made?

A butt weld pipe fitting is made by the process of hot forming that includes bending and forming to shape. The starting material of butt weld fitting is a pipe that is cut to length, heated and molded into specific shapes by means of dies. Heat treatment is also done to remove residual stresses and obtain desired mechanical properties. Read the link here to get more in depth detail of butt weld fitting manufacturing.


Benefits of Butt Weld Pipe Fittings

Welded connection offers more robust connection

  • Continuous metal structure adds to the strength of the piping system
  • Buttweld fittings with matching pipe schedules, offers seamless flow inside the pipe. A full penetration weld and properly fitted LR 90 Elbow, Reducer, Concentric reducer etc. offers gradual transition via welded pipe fitting.
  • Option of various turn radius using Short Radius (SR), Long Radius (LR) or 3R Elbows
  • Cost effective compared to their expensive threaded or socket weld counter parts.
  • Stainless Steel Welded Fittings are also available in SCH 10, allowing a more thinner wall option.
  • Stainless Steel Butt Weld Fittings are more common in SCH 10 and SCH 40 configuration.

All butt weld fittings have beveled ends as per ASME B16.25 standard. This helps create full penetration weld without any extra preparation needed for the butt weld fitting.

Butt weld pipe fittings are most commonly available in carbon steel, stainless steel, nickel alloy, aluminum and high yield material. High yield butt weld carbon steel pipe fittings are available in A234-WPB, A234-WPC, A420-WPL6, Y-52, Y-60, Y-65, Y-70.  All WPL6 pipe fittings are annealed and are NACE MR0157 and NACE MR0103 compatible.


Q&A

We handle hundreds of requests every day. Some of the common misconceptions are addressed in Q&A below;

Customer call butt weld fittings in A105: Most common carbon steel buttweld fitting material is A234WPB. It is equivalent to A105 flanges, however there is no such thing as A105 or A106 butt weld fitting
Customer request “Normalized” butt weld fittings: This is also a misconception since flanges are available in A105 and A105 N, where N stands for normalized. However, there is no such thing as A234WPBN. Some manufactures normalize their butt weld fittings as a standard procedure and such request require checking individual material test certificates to verify if normalized heat treating process was done. Customer needing “normalized” butt weld fittings should request WPL6 fittings which are high yield and are normalized as a standard procedure
Customer forget to mention pipe schedule: Buttweld fittings are sold as per pipe size but pipe schedule must be specified to match the ID of the fitting to the ID of the pipe. If no schedule is mentioned, we will assume a standard wall is requested.
Differentiate between SCH 40 & True Schedule 40: Pipe fittings 12 inch or larger require specifying if fitting is standard wall (most commonly referred to sch 40) or a true schedule 40 is required. This is needed since schedule 40 do NOT correspond to standard wall for pipe sizes 12” and bigger. A true sch 40 will be thicker than standard wall for pipe fittings 12” or bigger.
Differentiate between SCH 80 & True Schedule 80: For pipe sizes 10 in and above, sch 80 do NOT correspond to XH. Customer must specify if they want SCH 80 or XH wall.
Stainless Steel buttweld pipe fittings are available in schedule 10s: Customer should specify if they need standard wall (sch 40s) or a thinner wall sch 10s stainless steel butt weld fitting. See pipe chart to clarify how the wall thickness for stainless correlated to different pipe schedules.
Customer forget to mention welded or seamless butt weld fitting: Butt weld fittings are available in both welded and seamless configuration. A seamless butt weld carbon steel or stainless steel fitting is made of and is generally more expenses. fitting is NOT common in sizes bigger than 12”. Welded pipe fittings are made of ERW welded carbon steel or stainless steel pipe. They are available in sizes ½” to 72” and are more affordable than seamless fittings.

What does Short Radius (SR) or Long Radius (LR) means?
You will often hear SR45 elbow or LR45 elbow. The 45 or 90 refers to the angle of the bend for buttweld fitting to change the direction of flow. A long radius elbow (LR 90 Elbow or LR 45 elbow) will have a pipe bend that will be 1.5 times the size of the pipe. So, a 6 inch LR 90 has bending radius that is 1.5 x nominal pipe size. A (SR45 or SR90) has pipe bend that is equal to the size of fitting so a 6” SR 45 has bending radius that is 6” nominal pipe size.

What is a 3R or 3D elbow pipe fitting?
First, the term 3R or 3D are used synonymously. A 3R butt weld elbow has bending radius that is 3 times the nominal pipe size. A 3R elbow is smoother than SR or LR fitting.

Welded Pipe Reducers
Butt weld fittings are available in concentric reducer and to reduce the flow from one size of pipe to another. A concentric reducer butt weld fitting is symmetrical: both ends are aligned along the center.

An eccentric reducer butt weld fitting is not symmetrical: ends are off center of one another.


Butt Weld Fitting Collection

LR 90 Elbow: Fittings that change direction in a piping system are called elbows. The directional change is given in degree such as 45 or 90. Long radius 90 degree elbow has the center line of elbow at 1.5 x NPS from eblow end. 3R elbow has center line at 3 x NPS from elbow end.

LR 45 Elbow: Long radius 45 degree elbow changes the direction by 45 degrees.

SR90 Elbow: Short Radius 90 degree elbow is same as LR90 except for the measurement between end of elbow to center line is 1 x NPS.SR90 Elbow

LR 180 degree Bend: Long Radius 180 degree return bend allows complete reversal of flow. The distance between end of elbow and center line is 3 x NPS.return bend 180 deg LR

SR 180 degree Bend: Short Radius 180 degree return bend allows complete reversal of flow but in a much tighter turn. The distance between end of elbow and center line is 1 x NPS.

Tee: Butt weld pipe Tee allows a 90 degree branch off from a running pipe.This allows for connecting auxiliary equipment to a pipe. A tee is welded on both side to the pipe, leaving the branch open for branch off.

Reducing Tee: Butt weld reducing tee has a branch that is smaller than main run. This allows for branching off to a smaller pipe of equipment from the main run. Reducing Tee

Concentric Reducer: A concentric Reducer is also called welded concentric coupling. It allows from connecting a large pipe to a smaller pipe by means of welding. A concentric reducer allows welded connection between two pipes with the same center line.

Eccentric Reducer: An eccentric reducer is also called welded eccentric coupling. It allows for welding a large pipe to a smaller pipe with an offset center line. The offset of the center line in an eccentric reducer is; Offset = 1/2 x (Largest ID – Smallest ID)

Weldolet: A weldolet, also called welding outlet, is a way of connecting a welded connection that is contoured at the bottom to match the contour of the pipe. So one end of welding outlet is welded on the pipe, whereas the other end is open to be welded to any other pipe or equipment. A welding outlet requires mentioning the size of out let and the “Run Size” of pipe so the contour can match the contour of the pipe. The size of welding outlet will always be smaller than run size such as 1/2″ welding outlet can be used on pipe (run size) 1/2″ and bigger.

Welded Stub End: Stub ends are used with lap joint flange to welded onto the pipe.


Long and Short Radius

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made.

Pipe ebows are split into two groups which define the distance over which they change direction; the center line of one end to the opposite face. This is known as the “center to face” distance and is equivalent to the radius through which the elbow is bent.
The center to face distance for a “long” radius elbow, abbreviated LR always is “1½ x Nominal Pipe Size (NPS) (1½D)”, while the center to face distance for a “short” radius elbow, abbreviated SR even is to nominal pipe size.

Here below, for example, you will find the<br />center to face distance of NPS 2 elbows<br />(the A distance on the image)

1. 90°-LR : = 1½ x 2(NPS) x 25.4 A=76.2 mm
2. 180°-LR : = 2 times the 90° LR elbow A=152.4 mm
3. 90°-SR : = 2(NPS) x 25.4 A=50.8 mm
4. 180°-SR : = 2 times the 90° SR elbow A=101.6 mm

SR (Short Radius) Elbows: These elbows have a Center-to-Face dimension of 1.0 X diameter. They are typically used in tight areas where clearance is the main issue.

LR (Long Radius) Elbows: These elbows have a Center-to-Face dimension of 1.5 X diameter. They are the most common type of elbow and used when space is available and flow is more critical.

Reducing Elbow: A reducing elbow is a type of fitting which is used to join two pieces of pipe of different sizes. The reducing elbow is so called because it looks like a reducing piece and elbow combined into one. Reducing elbows have different sized openings on each end and hence they can connect two different sized pipes. They are available in different materials, sizes, finishes and colors.

45° Pipe Elbow: 45° Pipe Elbow is also known as “45 bends or 45 ells”. The 45° pipe elbow is used to connect tubes at a 45° pipe angle. As the name suggests, this is a pipe fitting device which is bent in such a way to produce 45° change in the direction of flow of the fluid/gas in the pipe.

Like a 90° elbow, the 45° pipe elbow also attaches readily to pipes of various materials like plastic, copper, cast iron, steel, lead, rubber etc. They are typically made as LR (Long Radius) elbows. These types of elbows are available in various sizes (in mm or inches). They are available with different male to female BSP thread connections. Providing a wide choice of colors, these 45° elbows can be manufactured to meet different specifications, in terms of size and diameter.

Male Pipe Elbows & Female Pipe Elbows: Male pipe elbows and female pipe elbows are popular fittings which provide an angled change in the direction of a tubing run. While a male pipe elbow is used to connect fractional to female tapered pipe thread, a female elbow is used to connect fractional to male NPT thread. These types of fittings like male elbows and female elbows have been specifically designed for use on instrumentation, process and control systems and equipment employed in chemical, petroleum, fluid power, electronic and pulp and paper plants.

The most applied version is the 90° long radius and the 45° elbow, while the 90° short radius elbow is applied if there is too little space. The function of a 180° elbow is to change direction of flow through 180°. Both, the LR and the SR types have a center to center dimension double the matching 90° elbows. These fittings will generally be used in furnesses or other heating or cooling units.

Dimensions, dimensional tolerances and more images, can be found in the main Menu “Fittings”.

In addition to the defined elbows, there is the Reducing Elbow, which is a elbow with various diameters on the ends. Because this elbow, for many suppliers it is not a standard item, and thus probably a high price with a long delivery time, the use of a “normal” elbow with a separate reducer is an option if the situation allows.

Reducing elbow 90°: Other degrees elbows can be machined from a standard elbow. Longer radius type, the center to face dimension e.g. is three times the nominal size (3D), even is available.


 

Related products maybe you like
Main uses of stainless steel
JIS G3463 Stainless Steel Tube
Stainless Steel Seamless Pipes
Stainless Steel Seamless Pipes packing
ASTM Standard of Steel pipes
Usage characteristics of thin-walled galvanized stainless steel tube
Stainless solution treatment effect

Leave a Reply

Your email address will not be published. Required fields are marked *