INDUSTRIAL FITTINGS

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.

Butt weld fittings are available as elbows, tees, caps, reducers and out lets (olets). These fittings are the most common type of welded pipe fittings and are specified by nominal pipe size and pipe schedule. Buttweld fittings use seamless or welded pipe as the starting material and are formed (through multiple processes) to get the 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 fittings.

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 comprise of long radius elbow, concentric reducer, eccentric reducers and tees. They are an important part of industrial piping systems 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 socket weld fittings. The latter 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 mentioned below.

Types of Butt Weld Pipe Fittings

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 equipment. The figure below represents a complete collection of butt welded pipe fittings.

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.

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 Piping Fittings 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.

304/304L (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

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 dyes. 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 a 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.

Trupply is one of the largest distributors of pipe, flanges, and fittings. We handle hundreds of requests every day. Some of the common misconceptions are addressed in Q&A below.