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What is pipe fitting?

What is pipe fitting?

Table of Contents

Pipe fitting is the general name of components in piping system that connect, control, change direction, divert, seal, support and so on.
Steel pipe fittings are all pressure bearing fittings. According to the different type of end connections, it can be divided into six categories: butt welding pipe fittings (including two kinds of weld and no weld), socket welding and threaded pipe fittings, flange fittings, spigot fittings, buttress fittings.
End Connection Type of Pipe Fittings
There are different types of pipe fitting used in piping. Pipe Fittings used in piping work are mainly Elbow, Tee, Reducer, Union, Coupling, Cross, Cap, Swage Nipple, Plug, Bush, Expansion Joint, Adapters, Olet (Weldolet, Sockolet, Elbowlet, Thredolet, Nipolet, Letrolet, Swepolet), Steam Traps, Long Radius Bend, Flanges and Valve.

Types of Pipe Fittings in Piping
You can see the chart above that list most widely used standard pipe fittings. These standard fittings are either forging or wrought. Only seamless pipes are used to produce wrought fittings. Large diameter welded fittings are manufactured from the plate.

Types of Butt weld pipe fittings

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.

Pipe bend



Pipe cap

Stub end

Pipe cross

Saddle previously

Expansion joints



Forged fittings

Pipe elbows

Pipe elbows are used to be installed between two lengths of pipe or tube allowing a change of direction,usually these elbows distinguished by connection ends.

By default, there are 5 opportunities, the 45°, 90° and 180° elbows, all three in the “long radius” version, and in addition the 90° and 180° elbows both in the “short radius” version.

Long Radius Elbow

In long radius elbow, centreline radius is 1.5 times the nominal size of the pipe or you can say 1.5 times the diameter of the pipe. Normally long radius elbows are used in piping as pressure loss is less as compared to short radius elbow. It required more space than short radius elbow.

45° Long Radius Elbow

Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter

  • L/R 45°Elbow: Long radius 45 degree elbow changes the direction by 45 degrees.
  • L/R 90°Elbow: Long radius 90 degree elbow changes the direction by 90 degrees.
  • L/R 180°Elbow: Long Radius 180 degree return bend allows complete reversal of flow.

Short Radius Elbow

In short radius elbow, centreline radius is same as the nominal size of the pipe or you can say one times the diameter of the pipe. Short radius elbows are used under limited space application. However, it has a high-pressure drop due to a sudden change in the direction of flow.

45 degree Long Radius Elbow

Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter

  • Short radiu 45°Elbow: Short radius 45° elbow changes the direction by 45 degrees.
  • Short radius 90°Elbow: Short Radius 90° elbow is same as LR90 except for the measurement between end of elbow to center line is 1 x NPS.
  • Short radius 180° Elbow: Short Radius 180° return bend allows complete reversal of flow.

Elbows 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.

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

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


  1. 90 Degree Elbow – where change in direction required is 90°
  2. 45 Degree Elbow – where change in direction required is 45°
  3. L/R – Long radius, S/R – Short radius

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.

bw elbows1 - What is pipe fitting?

Reducing Elbow

The reducing elbow is designed to change direction as well as reduce the size of pipe within a piping system. The reducing elbow eliminates one pipe fitting and reduces the welding by more than one-third. Also, the gradual reduction in diameter throughout the arc of the reducing elbow provides lower resistance to flow and reduces the effect of stream turbulence and potential internal erosion. These features prevent sizeable pressure drops in the line.

Reducing Elbow

Types of reducing elbow:
The reducing elbows are available in various types like:

  • 90° reducing elbow
  • 45° reducing elbow
  • 135° reducing elbow
  • 180° reducing elbow etc

Wall Thickness of Elbows

The weakest point on an elbow is the inside radius. ASME B16.9 only standardizes the center to face dimensions and some “squareness” dimensional tolerances. The wall thickness at the weld line location even is standardized, but not through the rest of an elbow. The standard states that the minimum tolerance will be within 12.5% of the minimum ordered wall thickness of the pipe. A maximum tolerance is specified only at the ends of the fitting.

Pipe bend

Pipe bending

The pipe bending is used to change the direction of run of pipe.

It advantage is can matach long distance transition requirements,so it is commonly that bends dimension according to customer design.

Bend by size and degree

  • 3D pipe bend: 3D pipe bend is a bend in which the radius of the curve is equal to 3 times the diameter of the pipe. It is a smoother bend than a 1.5D bend, which looks almost like a regular 90-degree right angle, but it is a sharper bend than a 5D bend, which looks like a smooth arc between two perpendicular pieces.
  • 5D pipe bend: the radius of a 5D pipe bend is actually what is 5 times the nominal diameter. So if you had a 10″ diameter pipe, the radius of the centerline of the bend would be 50 inches.
  • 7D pipe bend: 7D pipe bend is a pipe bend that the bend radius is 7 times the pipe outside diameter.
  • 10D pipe bend: 10D pipe bend is a pipe bend that the bend radius is 10 times the pipe outside diameter.
  • 12D pipe bend: 12D pipe bend is a pipe bend that the bend radius is 12 times the pipe outside diameter.

How to Calculate a Pipe Bend?

Whether you are bending pipe for running electrical conduit or a metal project, calculating the bend for the start and end point can be an important factor. While there are different types of pipe benders on the market, they all share a common identification for the operation. Identified on all pipe benders is the size of pipe the unit will bend along with a number called the “take up.” The take up measurement is used for adding or deducting an allowance in the overall length of the bend. By following a basic process, you can calculate pipe bends regardless of the type of bender or the diameter of pipe.
Identify the take up measurement that is located on the pipe-bending shoe itself. This is the addition or deduction of measurement to the length of pipe from the front mark on the bending shoe. Also be aware that there is a second center-of-bend mark located approximately in the center of the bending shoe. Also located along the running length of the shoe are angle markings with lines. These numbers and lines correspond to actual angles that can be bent into the pipe by aligning the pipe with the angled line marked on the outside of the shoe.
Bend a 90-degree angle on a ½-diameter pipe with a ½-inch bender. The process will remain the same for different sized pipes and benders, but only the take up measurement will be different. Identified on the shoe for the ½-inch pipe may be the wording “stub take up 5 inches from arrow or line.” The 5 inches is the amount you will deduct from the overall length of the 90-degree bend measurement.
Use the measuring tape and pencil and place a mark at 12 inches from the end of the pipe. This will be the distance from the bend to the end of the pipe. By using the deduction measurement on the shoe, measure back 5 inches from the 12-inch mark and make a solid pencil line.
Lay the pipe on a level surface and insert the pipe into the bender. The solid pencil mark should be placed 5 inches back from the 12-inch mark and should be aligned with the front mark or arrow on the bending shoe. Pull back on the handle in a smooth motion until the pipe sits at a 90-degree position to the level surface. Place the small level against the upright portion of the pipe and check for level. This will give you a perfect 90-degree bend. Check the height of the overall bend by placing the end of the tape measure on the level base and measure the end of the pipe. It should read 12 inches exactly.
Practice with other angled bends by using the deduction measurement and the center of the bend mark on the shoe. All pipe benders may have their own quirks and slight measurement adjustments that will have to be done. The actual end result also depends on how well and secure you hold the pipe in the bender, prior to the first bend you place on the pipe.

Pipe tee

A pipe tee is also called triplet,three way and “T” pieces and it can be used to either combine or split a fluid flow. Most common are tees with the same inlet and outlet sizes, but ‘reducing’ tees are available as well.

Pipe tee
Pipe Tee is a type of pipe fitting which is T-shaped having two outlets, at 90° to the connection to the main line.

  • Reducing tee: reducing tee has a branch that is smaller than main run allows for branching off to a smaller pipe of equipment from main run.
  • Equal tee: equal tee (or straight tee), means the branch diameter of this tee is same with the main pipe (Run pipe) diameter of this tee.
  • Lateral tee: a Lateral pipe tee means a pipe fitting which is similar to a tee but has a side opening outlet branch at a 45 degree angle.
  • Barred tee: a barred tee is a tee or any fitting with a branch used in pipelines that is pigged and has a restriction bar welded internally preventing the pig from traveling down a branch connection.

TEES: Extrusion method (Hot Forming)

The hot-extrusion process consists of enclosing a piece of metal, heated to forging temperature, in a chamber called a “container” having a die at one end with an opening of the shape of the desired finished section, and applying pressure to the metal through the opposite end of the container. The metal is forced through the opening, the shape of which it assumes in cross-section, as the metal flows plastically under the great pressures used.

TEES: Extrusion method (Hot Forming)
Hot forming

Tees using raw material with a bigger diameter than the finished product, the branch outlet is extruded from pipe while the main body is being pressed.

The outlet’s wall thickness can also be adjusted as needed. Applied to Tees with large diameters, heavy wall thickness and/or special material with challenging workability that cannot be manufactured using the hydraulic bulge method.

Buying Tips of pipe tee

What should buyers consider for bulk purchase of pipe tees?

  • Type of pipe tee—whether welded or seamless
  • Standard
  • Size and dimension
  • Wall thickness
  • Material of construction
  • Durability and Economical
  • High pressure and temperature resistance
  • Corrosion resistance etc.

Pipe reducers

Pipe Reducers are the component in a pipeline that reduces the pipe size from a larger to a smaller bore (inner diameter).

Pipe reducers

We produce pipe creducer include oncentric reducers, eccentric Reducers, seamless or welded, with dimensions and tolerances according to Asme/Ansi B16.9 and EN 10253-4.

Types of reducer

  • Concentric reducer: a concentric reducer is used to join pipe sections or tube sections on the same axis.
  • Eccentric reducer: eccentric reducer is a kind of fitting that be used for reducing piping size.
  • Swage Reducer: the swage is like reducers but small in size and used to connect pipes to smaller screwed or socket welded pipes. Like reducers, they are also available in concentric & eccentric type. Swages are available in different end types. Such as both plain ends or one plain and one threaded end.

Types of reducer

Pipe cap

Pipe cap is usually used for protecting the end of pipe and other fittings, so the shape are designed according to the shape of pipe line.
Pipe Cap are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.
Pipe cap

Vessel heads

Vessel heads are very varied used in candleholders to pipe end-pieces or pressure vessels in equipment construction.

Vessel head

Torispherical head according to DIN 28011

Torispherical head according to DIN 28011

Surface treatment:

  • Transparent oil, rust-proof black oil or hot galvanized.
  • Special design available All the production process are made according to ISO9001:2000 strictly.
  • Based on different materials, pipe caps include carbon steel cap, stainless steel cap, and alloy steel cap etc.
  • Depending on their construction, pipe caps contain threaded cap, tapered cap and anti-roll cap etc.

Features of pipe caps:

There are several important specifications that the buyer should consider before making bulk purchase of pipe caps. The important specifications that needs to be considered are:

  • NPT (National Pipe Thread ) size: This feature is applicable for round shaped caps, wherein the object that has to be protected has a male NPT thread.
  • BSP (British Standard Pipe) size: This size option is applicable only for round shaped caps, wherein the object to be capped has a male BSP thread.
  • Diameter: Diameter is an important dimension that is applicable only for round caps and plugs. In case of fittings having straight threads, the most important feature to be considered is the major thread diameter. However, this dimension is not an
    important consideration when cap, plug or object to be capped has a tapered (NPT or BSP) thread.
  • Shape: The dimension and shape of pipe caps are also very important points to consider. Pipe caps of different shapes have different features.


  • Reasonable price with excellent quality
  • Abundant stock and prompt delivery
  • Rich supply and export experience, sincere service
  • Reliable forwarder, 2-hour away from port.

CAPS: Deep Drawing method

One of the most common manufacturing methods for caps, where plate is cut out in a circle and formed by deep drawing.

CAPS: Deep Drawing method

Deep drawing is the manufacturing process of forming sheet metal stock, called blanks, into geometrical or irregular shapes that are more than half their diameters in depth. Deep drawing involves stretching the metal blank around a plug and then moving it into a moulding cutter called a die.

A drawing press can be used for forming sheet metal into different shapes and the finished shape depends on the final position that the blanks are pushed down in. The metal used in deep drawing must be malleable as well as resistant to stress and tension damage.

How to get high quality pipe cap?

Pipe cap acts as protective device and are designed to protect pipe ends of various shapes. The main purpose of using pipe caps is to waterproof the connections. They are also used to close the the ends of hydraulic or pneumatic pipes and tubes. They are used in the plumbing apparatus of domestic, commercial and industrial water supply lines, machinery and processing equipment etc. They are also fitted on water pump lines with the sole purpose of removing air blocks. Pipe caps are highly demanded as an important category of pipe fittings. If a solvent-weld cap is used to provide for a future connection point, several inches of pipe must be left before the cap; when the cap is cut off for the future connection, enough pipe must remain to allow a new fitting to be glued onto it.

How to connect pipeline with pipe cap?

Pipe Cap is directly welded to die at the end of the pipeline; at the end of the pipeline can also welding flange, then with a blind flange to death, when necessary can open the blind flange, pipeline check inside. The conventional cap holder with pressure pressing made by thick wall; forging; by spinning large diameter. The need for maintenance or even after the connecting line, with blind, not later, with a pipe cap. With the blind plate has the possibility of leakage, there is a long time, and screw rust died, as useless, the heat pipe is not very easy to heat insulation.

Stub end

Stub end

Stub ends are also called Lap Joints and Vanstone Flared Laps that can be used (in combination with a lap joint flange) alternatively to welding neck flanges to make flanged connections.

Types of Stub Ends

Types of Stub Ends

Stub ends are manufactured in three different types and two standard length.

  • Type “A”: this type is produced and machined to fit lap joint flanges.The mating surfaces of the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside corner of type A has a radius to accommodate the lap join flange, whereas the inside corner is squared.
  • Type “B”: this type of stub ends is suited for standard slip-on flanges acting as lap-joint flanges. The lap thickness of type B stub ends is >= the minimum WT of the connecting pipe. The lap of these type of stub ends has generally a serrated face. To ensure tight joints, chamfers on the ID side of the flange are required.
  • Type “C”: this last type can be used both with lap joint and slip-on backing flanges and are fabricated out of pipes. The lap of C-type stub ends is flared over and the lap thickness is 75% of the connecting pipe WT. Type C has a short fillet outer radius able to host any back up flange.
  • Type “CS”: this type is similar to “C” with the difference that the lap face has concentric serrations machined during the manufacturing process.
short long stub end - What is pipe fitting?
Short / long pattern stub ends (ASA/MSS)

Short pattern (MSS) and long pattern stub ends (ASA)

Stub ends are available in two different patterns:

  • The short pattern, called MSS-A stub ends
  • The long pattern, called ASA-A stub ends (or ANSI length stub end)

Stub ends dimensions and weight

Dimensions and manufacturing tolerances are covered in ASME B16.9 – Butt Weld Fittings and MSS-SP-43 (JIS B2312, JIS B2313 may also apply).

Stub End come in three standard lengths, MSS SP43 or ANSI B16.9 short and long pattern. Short pattern stub ends are mostly used for flanges from class 300 to class 600 and above. Besides these standard types, End-Users and contractors can require stub ends with non-standard lengths to suit specific project’s requirement. This will of course come at an additional cost.



Ends/Face lap finishing

The following types of ends may be ordered:

  • Beveled Ends (generally ASME B16.25)
  • Squared Ends
  • Flanged Ends
  • Victaulic Grooves
  • Threaded Ends (Male Only)

Material for Stub Ends

Stub Ends are available in numerous ASTM and other international recognized materials, to match pipe specifications, as low alloy, stainless steel, austenitic-ferritic, high alloy steels (nickel alloy such as Inconel, Incoloy 800, Monel, Hastelloy C276), non-ferrous materials (copper, cupronickel 90 /10 and cupronickel 70 / 30) and titanium / zirconium / tantalum.

Material Grade UNS Equivalent
A234 WPB Carbon Steel B K03006
A403 Stainless Steel 304/304L S30403
304H S30409
316/316L S31603
316H S31609
317L S31703
904L N08904
309S/H S30908
310S S31008
321 S32100
6XN N08367
20CB N08020
347 S34709
254SMO S31254
A815 Duplex /Super Duplex 2205 S31803/S32205
Zeron 100 S32760
2507 S32750
410 S41000
A366 Nickel Alloys HC22 N06022
HB-3 N10675
HG3 N06985
HX N06002
HC2000 N06200
HC276 N10276
NCI N06600
NC N04400
N N02200
NL N02201
NCMC N06625
NICMC N08825
NIC10 N08810
NIC11 N08811

Lap-joint flanges are most commonly available in carbon steel and low temperature carbon steel, because it is a lower cost than the Stub End that will be wetted by the service and it must be of a suitable grade of steel. If orientation and alignment of bolt holes is the only issue, then for standardization, then the Stub End and the Lap Joint Flange can be of the same material.

The most common material grade for stub end is the ASTM A403 / ASME SA403 (stainless steel stub ends). With reference to EU materials, the most common grades are DIN 1.4301, DIN1.4306, DIN 1.4401, DIN 1.4404.

Stub Ends assembly

Stub Ends assembly2 - What is pipe fitting?

Stub ends and lap joint flanges can be assembled following this process:

  • The Lap Flange is slipped over and onto the Stub end Flange.
  • The Stub End Flange is then welded onto a pipe spool, using an approved Welding. Procedure Specification (WPS), by a qualified Welder. The Lap Joint Flange, backing Flange, can revolve around the Stub End, which is now attached to the piping spool.
  • The bolt holes of the Lap Joint Flange can now be orientated and aligned with the bolt holes of a mating Flange of the same ASME designate rating and NPS.
  • The Lap Joint Flange can be mated to any Flange covered in ASME B16.5, Weld Neck, Slip On, Threaded, Socket Weld, another Lap Joint Flange.

It can also be mated to a fabricated plate Flange with compatible, bolting dimensions.

Why use Stub Ends?

Lap Joint Stub End

A stud end and a lap joint flange can be used together as an alternative way to make a flanged connection than welding neck flanges.

The two devices to be combined, in this case, are:

  • The stub end, which is essentially a piece of pipe, with one end flared outwards and the other prepared to be welded to a pipe of the same bore size (NPS = nominal pipe size), material and wall thickness. The most widely used fabrication tool for stub ends is the flaring machine, which is able to flare the end of the pipe and then cuts it to length.
  • A Lap Joint Flange, which is used to actually bolt the two lengths of pipe together.

Commercial benefits

Commercial advantages are that the Stub End, will be wetted and it must be made of a grade of material that meets the process design and service conditions of the pipeline. However, the Lap Flange is un-wetted and it can be made of a lower grade of material as long as it meets
the mechanical strength requirements of the piping systems.

This means that instead of:

Duplex stub end and a duplex lap joint, you could have duplex stub end and carbon steel lap flange.
Or you could have stainless stub end and carbon steel lap flange. There are other bimetallic combinations that result in a flange assembly that is commercially cheaper.
During recent years the price differential between duplex/stainless steel and carbon steel has narrowed and this practice on large projects has become less common, however a cost difference always exists (the higher the nps and the length of the pipeline / piping system, the higher the saving). On the other hand, the warehousing cost of one single component, i.E. A weld neck flange, requires less shelf space than the cost of warehousing a lap joint and a stub end. End users and contractors shall determine the actual convenience of using stub ends, considering all these factors and generally the commercial advantage is still valid and it may suit certain situation, especially in “brownfield” modifications.

Installation benefits

The “loose” flange concept of a Lap Joint, is very beneficial during field installation of piping systems. If two spools are to be mated up in the field, having one flange that can be rotated is very advantageous when aligning the bolt holes, prior to the introduction of the Stub bolt and the accompanying nuts. The facility of easier orientation and alignment of bolt holes, is of particular use it there is a spool that
has to be removed frequently, if positive isolation is a process requirement.

Stub Ends limitations

A Lap Joint consists of two independent components that are not integrated with a weld and like for like in size/pressure class/material it lacks the mechanical strength and capabilities to withstand fatigue, like a one piece Weld Neck Flange or a welded together Slip On or Socket Weld Flanges. In cyclic services, collars EN 1092-1 type 35 PN 16-25-40 are used instead of stub ends (especially to close pumps and compressors). If carefully consideration is given to Process Design condition, the service and the final application, then a Lap Joint Flange mechanical connection are a valid and cheaper method for installing piping systems compared to the use of standard flanges.

A stud end and a lap joint flange can be used together as an alternative way to make a flanged connection than welding neck flanges.

Stub Ends assembly - What is pipe fitting?

The two devices to be combined, in this case, are:

  • The stub end, which is essentially a piece of pipe, with one end flared outwards and the other prepared to be welded to a pipe of the same bore size (NPS = nominal pipe size), material and wall thickness. The most widely used fabrication tool for stub ends is the flaring machine, which is able to flare the end of the pipe and then cuts it to length.
  • A Lap Joint Flange, which is used to actually bolt the two lengths of pipe together.

How to order a Stub Ends?

The following information shall be provided to order a stub end:

  • NPS
  • Schedule
  • Length (according to norms MSS SP43 / ASME B16.9 / custom)
  • Specs and material grade
  • Ends finish
  • Execution: seamless / welded (wx)

Stub end finish

Stub ends can be ordered with different ends finishing:

  • Beveled Ends
  • Squared Ends
  • Flanged Ends
  • Grooved Ends
  • Threaded Ends (Male Only)

Stubend geometry

The Stub End, which essentially a short length of pipe, which has one end that is flared outwards and the other end prepared to be welded to pipe of the same Nominal Pipe Size (NPS), material and of a similar wall thickness. The lap joint flange, which is a ring backing Flange and it is very similar in geometry to the Slip-on Flange.

Stubend geometry

Stub ends are mechanical joints that comprises of two components.

This type of flanged connection was also referred to as “Van Stone” or “Vanstone flare laps”, however this is an historic terminology and very rarely used technically or commercially.

N.D. Out diamater Hight(F) 翻边直径G 倒角半径R
NPS DN OD Mss ANSI Nominal&max Nominal&min A Max B Max
1/2 15 21.3 50.8 76.2 35 34 3 0.8
3/4 20 26.7 50.8 76.2 43 42 3 0.8
1 25 33.4 50.8 101.6 51 50 3 0.8
11/4 32 42.4 50.8 101.6 64 63 4.8 0.8
11/2 40 48.3 50.8 101.6 73 72 6.4 0.8
2 50 60.3 63.5 152.4 92 91 7.9 0.8
21/2 65 73 63.5 152.4 105 104 7.9 0.8
3 80 88.9 63.5 152.4 127 126 9.6 0.8
31/2 90 101.6 76.2 152.4 140 139 9.6 0.8
4 100 114.3 76.2 152.4 157 156 11.2 0.8
5 125 141.3 76.2 203.2 186 185 11.2 1.6
6 150 168.3 88.9 203.2 216 215 12.7 1.6
8 200 219.1 101.6 203.2 270 269 12.7 1.6
10 250 273.1 127 254 324 322 12.7 1.6
12 300 323.9 152.4 254 381 379 12.7 1.6
14 350 355.6 152.4 304.8 413 411 12.7 1.6
16 400 406.4 152.4 304.8 470 468 12.7 1.6
18 450 457.2 152.4 304.8 533 531 12.7 1.6
20 500 508 152.4 304.8 584 582 12.7 1.6
22 550 559 152.4 304.8 641 639 12.7 1.6
24 600 610 152.4 304.8 692 690 12.7 1.6

Pipe Cross

A pipe cross is a kind of pipe fitting that be used in the place where four pipes meet together. The pipe cross may have one inlet and three outlets, or there inlets and one outlet. The diameter of the outlet and inlet can be the same and can also be different. That is to say, straight cross and reducing cross are both availabe.
Pipe Cross

Types of Pipe Cross

  • Reducing cross: the reducing cross also is called unequal pipe cross , it is the pipe cross which the four branch ends are not in the same diameters.
  • Equal cross: the equal cross is one kind of the pipe cross, just like a equal tee, the equal cross means all the 4 ends of the cross are in same diameter.

Features of Pipe cross:

  • There are three female openings in a T shaped pipe cross.
  • There are straight pipe crosss which have the same size openings.
  • Reducing pipe crosss have one opening of different size and two openings of the same size.
  • There are sanitary pipe crosss which are used in waste lines. These kind of pipe crosss have a curved branch which is designed for a clean out plug. They are used to prevent obstruction of waste.
  • A cross pipe cross has four equal sized female openings.
  • A wing pipe cross has lugs to fasten the fitting to a wall or stud.
  • A compression pipe cross uses compression fittings on two or more ends.
  • A test pipe cross has a threaded opening. This opening is used in conjunction with a threaded plug for a clean-out opening on a drain pipe.

Buying Tips of pipe cross:

What should buyers consider for bulk purchase of pipe cross?

  • Type of pipe cross—whether welded or seamless
  • Standard
  • Size and dimension
  • Wall thickness
  • Material of construction
  • Durability and Economical
  • High pressure and temperature resistance
  • Corrosion resistance etc.

Saddle previously

Saddle previously is the ventilation ducts ‘crotch tee’, its shaped like pants, there Equal and unequal diameter, the formal name is “tube tapered pants tee.”

Saddle previously
There is no standard size, to be based on three tube spacing center line of the front and graphic design draw graphics, Lofting produced, lofting a certain degree of difficulty.

Industrial Processes of Saddle previously

saddle previously process1 - What is pipe fitting? saddle previously process2 - What is pipe fitting?
saddle previously process3 - What is pipe fitting? saddle previously process4 - What is pipe fitting?

Saddle previously DIN 2618

Saddle previously DIN 2618

DN d1 s h kg
20 26.9 2.3 30 0.06
25 33.7 2.6 30 0.09
32 42.4 2.6 35 0.13
40 48.3 2.6 40 0.21
50 60.3 2.9 45 0.27
65 76.1 2.9 50 0.45
80 88.9 3.2 60 0.70
100 114.3 3.6 65 1.20
125 139.7 4.0 85 2.10
150 168.3 4.5 100 2.90
200 219.1 6.3 135 6.40
250 273.0 6.3 150 9.80
300 323.9 7.1 175 17.20

Expansion joints

Expansion joints are devices containing a bellows membrane that are designed to absorb dimensional changes, such as those that occur due to thermal expansion or contraction of a pipeline, duct or vessel.
Expansion joints

Expansion joint accessories

  1. Bellows
  2. Angle Flange
  3. Weld End
  4. Liner (Baffle)
  5. Cover
  6. Particulate Barrier/Insulation
  7. Liner Seal
  8. Purge
Expansion joint accessories - What is pipe fitting?

Accessories Of Expansion Joints

  1. Minimize the pressure drop through expansion joint.
  2. Prevent vibration of bellows induced by high velocity, turbulent flow.
  3. Prevent erosion of bellows in abrasive services.
  4. Internally insulate bellows in high temperature services.
  1. Divide piping into two separate segments insuring proper movement of each bellows in double type expansion joint.
  1. Protect bellows against mechanical damage during installation and in service.
  2. Protect personnel in hazardous services.
  3. Serve as support for external insulation.

Used in conjunction with internal sleeve to:

  1. Prevent packing, “coking”, of flue-solids between internal sleeve and bellows.
  2. Introduce coolant between bellows and internal sleeve in very high temperature service.
  1. Prevent application of pressure thrust to piping, or equipment when expansion joint is used for lateral deflection and/or angular rotation only.
  2. Used as limit rods on expansion joints for axial movement. Limit over-extension of joint and damage to piping or equipment if anchor fails.
  3. Used as control rods to limit and control movement of universal type expansion joints.
  1. Permit use of internal sleeve for joint moving laterally or angularly without reducing inside diameter.
  2. Used in conjunction with internal sleeve to reduce bellows temperature in very high temperature service.
Expansion joint

What industries use expansion joints?

Expansion joints are used in all kinds of different sectors and in a huge range of different industrial contexts. Essentially, wherever there is a need to control pipework movement expansion joints are required.

Selection skill of compensator

The compensator adopts rectangular section, fillet waveform, and a single expansion joint in the pipeline bears two-dimensional displacement. The elbow joint pipe composed of two expansion joints can bear three-dimensional displacement. The metal corrugated expansion joint with rectangular fillet has full height and half height. According to the flue size, stress and strain requirements, users can select multiple wave joints.

Installation and pressure test of compensator

See the following figure for the installation method of corrugated expansion joint and pipe support, which must be followed in the installation process.

Expansion Joint installation pressure test - What is pipe fitting?

Fatigue test of compensator

The fatigue life design can be seen from the failure type and cause analysis of the bellows compensator that the plane stability, circumferential stability and corrosion resistance of the bellows are all related to its displacement, that is, the fatigue life. Too low fatigue life will lead to the decline of bellows stability and corrosion resistance. According to the test and use experience, the fatigue life of bellows used in heat supply engineering shall not be less than 1000 times.

Thick Wall Pipe Expansion Joint

Thick Wall expansion joints are frequently used in heat exchangers, furnace and blast furnace pipe work.

These may be a cost-effective option for large-diameter piping systems which operate at low pressure. Metals can be selected to satisfy different temperature conditions. The distribution of axial, angular, and lateral forces will be different when thick-wall pipe expansion joints are used. We can provide your design engineers with the potential forces and movements for proper design of the structural members supporting the system. These joints have a long life which justifies the initial investment.

Thick-wall expansion joints are used primarily in heat exchangers and large diameter piping systems where thin-wall expansion joints would not be sufficient. The bellows are typically fabricated from A516 Grade 70 material, with the thickness ranging from 3/16″ to 1″. Other materials are available to meet different temperature requirements.

Thick Wall Expansion Joints are normally supplied without any end connections due to the fact that it is easier to weld the end fittings to them by a relatively less skilled welders. The heavy wall bellows are less susceptible to damage during installation and system start-up however these bellows possess high spring forces as a result of high convolution profile. The thickness of these thick wall bellows elements vary from 1 mm to 3 mm depending up on size and the height of convolution varies from 50 mm to 100 mm.

Thick Wall Expansion Joint (Bellows), has a very diverse methodology, which is explained in one of the articles below. The following calculations are supported:

  • Cylinder calculations
  • Differential axial thermal expansion
  • Axial rigidity
  • Radii requirements
  • Cylinder calculations
  • Cycle life
  • Minimum thickness based on material and service

Universal tied expansion joint

Universal tied expansion joints consist of two bellows with a central pipe and tie rods to withstand reaction forces produced by internal pressure.  The universal tied expansion joint allows large lateral movement in all planes, this movement can be increased by increasing the length of the central pipe.

Universal tied expansion joint

Universal tied expansion joint with flanges

The universal tied expansion joint can take greater axial, lateral and angular movements than a single tied expansion joint. If the universal tied expansion joint is designed with only two tie rods, equally spaced 180 degree, the expansion joint will take both lateral and angular movements. If more than two tie rods are used then this kind of expansion joint will only take lateral movement. Dome washers are also used depending upon the design requirement.



Fittinga accessories such as Stub Ends, Flange bolts & Nuts, Flange Gaskets and Bolt Sets, Fasteners, Olets and many more items from China.

Bolts & nuts

flange bolts 200 200 - What is pipe fitting?

Flange bolts are those type of bolts having a ridge or skirt around the bolt head.


Olets (pipe fitting) are supplied according to proven designs and from the highest quality materials, the outlet components we supply are suitable for a variety of heavy duty applications. We supply outlet fittings in a number of hard wearing industrial grades to withstand high levels of flow and corrosion.

Reinforced pipe fittings mainly used for olet connection, instead of using reducer tee, reinforcing plate, reinforcing pipe section and other pipe connection types, it is safe and reliable, reduces cost, simple construction, improves medium flow channel, series standardization, and convenient design and selection. Such outstanding advantages, especially in high pressure, high temperature, large diameter, thick wall pipelines, are increasingly used, replacing the traditional olet connection method.

The main body of the olet is made of high-quality forgings, and the materials are the same as the pipe materials, such as carbon steel, alloy steel and stainless steel. Both the olet and the main pipe are welded, and the connection of the olet or other pipe (such as short pipe, wire plug, etc.), instrument and valve has three types: butt welding connection, socket welding connection and screw connection. Commonly used manufacturing standards for olet stations are MSS SP-97, GB/T19326 and other standards.

Olets / Outlet Material:

Titanium olet, Tantalum, Nickel , Cupro nickel, Zirconium, Hastelloy , Incolloy, HR Alloy, Alloy 20, Monel, Inconel, stainless Steel, Niobium, Nimonics ,duplex olets, super duplex outlet.

  • Standard: BONNEY ,SAE
  • Classes: 2000 lbs, 3000 lbs, 6000 lbs, 9000 lbs

Olets / Outlet Type

Socket outlets, Threaded outlets, Welded Olet, Nippolets

Olets / Outlet Type

Available Olet Fittings are :

Pipe Coupling VS Olets

pipe coupling vs olets – Pipe Coupling VS Olets

The olet table is used to open the olet on the main pipe wall; the connection form with the main pipe is welding, and the connection mode with the olet may be butt welding, socket welding or thread; the main pipe and the olet connected by the olet table are vertical or oblique Cross relationship.

The pipe Coupling is used for the connection at the pipe joint of the two pipes; the connection mode of the two pipes to the pipe Coupling is socket welding or thread; the two pipes connected by the pipe Coupling have the same axial direction.

For pipe diameter

  1. Sockolets: refers to the socket welding pipe table for pipe diameter DN15~DN40, see standard MSS-SP-97
  2. Weldolet: refers to the butt welding pipe table for pipe diameter DN50 or above, see standard MSS-SP-97
  3. Threadolet: Threaded pipe stand for pipe diameter DN15~DN40, see standard MSS-SP-97

Full coupling, socket welding, for pipe diameter DN15~DN40, see standard ASME B16.11, GB/T 14383-2008

Half coupling, socket welding, for pipe diameters DN15~DN40, see standard ASME B16.11, GB/T 14383-2008

The olet station is widely used in foreign countries in recent years. The reinforcing pipe fittings used for olet connection replace the traditionally used reducer tee, reinforcing plate and reinforced pipe section, etc., which are safe and reliable, reduce the cost; simple construction Improve the medium flow channel; serialization standardization, convenient design and other outstanding advantages, especially in high pressure, high temperature, large diameter, thick wall pipe.


Gaskets are used for improved joint performance.
They are considered much more superior than the conventional ring or full-face gaskets. Although pipe flange gaskets are usually used for all normal water and sewer service, they are especially useful in demanding services like in very large diameter piping.
For specially designed long-span installations, involving 2 or 3 or more lengths of pipe or with any underground flanges, flange gaskets are of great help because they could be subjected to undesirable beam loading.
These gaskets are available in numerous standard materials in various thickness and hardness options for various flange sizes. Flange gaskets are also available with adhesive on one or both sides or without adhesive. Most materials are available starting at 1/32” thick and can be supplied up to 1” thick. Some manufacturers supply flange gaskets in wide rolls from which you can cut your flange gaskets to size. Flange gaskets are also available to your exact requirements. Pipe flange gaskets are being very frequently used for flanged joints which are subjected to extreme chemical attacks.

What is the difference between a RTJ, FF, and RF flange on seals and thermowells?

Pipe gaskets (otherwise known as flange gaskets) are made from wide range of materials such as rubber, non-asbestos and graphite. The gaskets can be bought as either Full Faced (with bolt holes) or Inner Bolt Circle (IBC, ring type or raised face).

There are many standards in gasket for flanges of pipes.

gaskets type rf - What is pipe fitting?

Type RF

gaskets type ff - What is pipe fitting?

Type FF

gaskets type rtj - What is pipe fitting?

Type RTJ

The raised face, RF, is the standard process connection on our third party seals and thermowells. Both have options for a RTJ and FF type flange connections. The Raised Face (RF) is the most common type used in process plant applications.

flange connection - What is pipe fitting?

The gasket surface of the flange is raised above the bolting circle face. A Ring-type Joint (RTJ) can also have a raised gasket face with the difference being the ring groove machined in this face. This groove will accommodate a steel ring gasket for flange mating. The Flat Face, FF, flange has a gasket surface that is in the same plane as the bolting circle face. None of these three flange types are interchangeable between types, i.e. RTJ flange cannot be mated to a RF flange.


Each U bend tube of our range is rigorously quality checked by our team of talented professionals on every stage of production to deliver the clients defect free best quality products.

Measuring, Cutting, Deburring and Cleaning

We bring forth an exclusive range of U-bend tubes, which are known for their superior quality and excellent functionality.

Measuring, Cutting, Deburring and Cleaning

After U bend (cold forming), heat treatment of bending portion may be required. Temperature is controlled through the entire heat treated area by fixed and portable infrared pyrometers.

Standard for U bend Tubes

The semi-finished product for U bend tubes are heat exchanger tubes, manufactured and supplied according to DIN 28180 and ASTM A179.

u bend drawing - What is pipe fitting?

U bend dimension capablity

Tube OD Tube thickness Bending Radius U tube straight “leg” length Straight tube before U bending
Min. 12,7mm / Max. 31,75mm Min. 0,70mm / Max. 4,19mm Min. 1,5 x OD / Max. 1250mm Max. 12500mm Max. 27000mm

At present Yaang has purchased the equipment for production of the following product range:

Dimensional controls on U bend tube

‘U’ bends are produced, controlled and measured fully in accordance with relevant standards.

  • Hydrostatic Test
  • Air Underwater Test
  • Pulsating Pressure Test
  • Dye Penetrant Test
  • Magnetoscopic test
  • Dye penetrant of ‘U’ bend area
  • PMI testing
  • Heat Treatment

All tubes are cut to the specified leg lenghts, ends deburred and the bores are internally cleaned with dried air.

Heat Treatment

We are equipped to carry out heat treatment of bends plus a minimum 150mm of leg.

Heat Treatment Equipment

  • Heat treatment equipment is computer controlled with the added facility of data recording.
  • An argon protective atmopshere is used inside stainless and special alloy tubes during heat treatment.
  • We can provide all types of annealing; solution annealing and stress relieving.

All tubes are cut to the specified leg lenghts, ends deburred and the bores are internally cleaned with dried air.


U-bend tubes are widely used in heat-exchanger systems.

u bend tube heat exchanger animation - What is pipe fitting?

Heat-exchanger equipment on the basis of seamless stainless U-tubes is essential in strategically important and critical fields — nuclear and petrochemical machine building.

“U bend tubes for heat exchangers applied mostly in Oil & Gas plants, Chemical & Petrochemical plants, Refineries, Power plants, Renewable energy plants.”
  • Object medium: 10% sodium
  • hydroxide+5% sodium hypochlorite
  • Shell Diameter: ø 800
  • Working Pressure: 1.5mpa
  • Working Temperature: 40º C-90º C
  • Heat Exchange Surface Area: 100M2
  • Material: Gr1\Gr2


Any type of packing is available according to customer need to worldwide destinations.

  • For roadfreight in timber fingers or skids.
  • In strong open or closed wooden boxes depending destination.
  • Each bundle is protected with plastic sheets.
  • Customers can provide their own packing or Salem can prepare a packing plan.
  • Detailed packings lists are attached to wooden cases to give quick and clear identification of contents.

Any type of packing is available according to customer need to worldwide destinations.

Materials – U Bend Tube

‘U’ bends are produced, controlled and measured fully in accordance with relevant standards.

Carbon Steel SA 179 / A 179
Carbon Steel SA 210 / A 210
Carbon Steel SA 334 / A 334
Stainless Steel SA 213 / A 213
Duplex Stainless Steel SA 789 / A 789
Copper & Cu Alloys SB 111 / B 111
Titanium & Ti Alloys SB 338 / B 338

Feedwater Heater Tubes

Standard:ASME SA556 Chemical Compostion

Grade C % Si % Mn % P % S %
B2 0.27 max 0.10 min 0.29-0.93 0.030 max 0.030 max
C2 0.30 max 0.10 min 0.29-1.06 0.030 max 0.030 max

Mechanical Properties

Grade Tensile Strength MPA Yield Strength MPA Hardness HRB
B2 410 min 260 min 79 min
C2 480 min 280 min 89 min

Each U bend tube of our range is rigorously quality checked by our team of talented professionals on every stage of production to deliver the clients defect free best quality products. These U bend tubes can be custom designed in various diameters as per the requirements of our clients.

U-Bend Fabrication Tolerances

Heat-exchanger equipment on the basis of seamless stainless U-tubes is essential in strategically important and critical fields — nuclear and petrochemical machine building.

measuring u bend tubes arc - What is pipe fitting?

measuring u bend tubes od - What is pipe fitting?

Features :

  • ‘U’ bending is done by cold working process.
  • ‘U’ bending is done to the required radius as per customer drawings.
  • The bend portion and six inch leg is stress relieved by resistance heating.
  • Inert gas (Argon) is passed through it at the required flow rate to avoid oxidation in ID.
  • The radius is checked for its OD and wall thinning with the recommended specification.
  • The physical properties and micro-structure is checked at three different position.
  • Visual inspection for waviness and cracks is done with Dye Penetrant Test.
  • Each tube is then hydro tested at the recommended pressure to check for leakage.
  • Cotton ball test is done to check the ID cleanliness of the tube.
  • Thereafter pickled, dried, marked and packed.
Item Condition (when) Tolercance
Nominal bend radius ≤ 2 x nominal OD less than or equal to 12%
Ovality 2 x nominal OD < Nominal bend radius ≤ 4 x nominal OD less than or equal to 10%
Nominal bend radius > 4 x nominal OD less than or equal to 5%
Nominal bend radius ≤ 2 x nominal OD 0.75 x nominal wall
Mimimum wall thickness 2 x nominal OD < Nominal bend radius ≤ 4 x nominal OD 0.8 x nominal wall
Nominal bend radius > 4 x nominal OD 0.9 x nominal wall
Nominal bend radius ≤ 8″ (200mm) +/-3/64″(1mm)
Bending Radius 8″ (200mm) < Nominal bend radius ≤ 16″ (400mm) +/-1/16″(1mm)
Nominal bend radius >16″ (400mm) +/-5/64″(1mm)
Disrance between legs Max 1/16″(1.5mm)
Wall thinning of bending area Max 17%
Difference between leg lengths at the ends Leg length ≤ 16′ (4.88m) +1/8″(3mm)
Leg length > 16′ (4.88m) +3/16″(5mm)
Deviation from plane of bend ≤ 3/16″(1.5mm)
Flattening on bend ≤ 10% nominal diameter
Straight leg length ≤5m +1/8″(3mm)
>5m +3/16(5mm)
Total tube length including radius ≤6m +3/16(5mm)
>6m +5/16″(8mm)

Forged fittings

Yaang forged fittings can come in Elbows, Street Elbows, Tees, Crosses, Couplings, Reducers, Outlets, Inserts, Caps, Unions, Bushings, and Plugs.

  • Forged Elbow: forged Elbow is one of the commom pipe fittings applied in oil&gas industry. An elbow provides a change in material-flow direction.
  • Forged Tee: forged Tee is available with both socket weld and threaded ends.
  • Coupling fitting: coupling fitting is used for fluid conduits in which each end portion of two tubes to be connected is provided with a swaged-on adapter carrying the necessary means to connect or disconnect the tubes without disturbing the swaged-on adapter.
  • Forged Union: Unions are used as an alternative to flanges connection in low-pressure small bore piping where dismantling of the pipe is required more often. Unions can be threaded end or socket weld ends. There are three pieces in a union, a nut, a female end, and a male end. When the female and male ends are joined, the nuts provide the necessary pressure to seal the joint.
  • Forged Nipple: nipple is a short stub of pipe which has a male pipe thread at each end or at one end. It used for connecting two other fittings. Nipples are used for connecting pipe, hoses, and valves. Pipe nipples are used in low-pressure piping.
  • Malleable fitting: malleable fitting is the fitting has the property of malleability.

Classifications of Forging

Forging is one of metal pressure processing methods, referring to that use pressure to change the shape of metals so that can acquire forging pieces having mechanical property, shapes and dimensions.
The followings are the classifications of forging.
1. Hammer smith forging
The pattern of hammer forging is the same as blacksmithing. The work pieces are heated to the forging temperature, then, put between hammer flattener and drill plate for further forging. Small pieces can be made by hand, called as blacksmithing. Larger pieces need steam hammer. The work pieces are put between drill plate and hammer flattener. Structure of steam hammer is determined by forging capacity. Light one is single stand while heavy one is double stands.
2. Drop hammer forging
The difference between drop hammer forging and flat forging is that there is a mold cavity on hammer used for drop hammer forging. Work pieces suffer from two aspects of pressure or impact force in mold cavity, plastic deforming according to the shape of mold cavity. To ensure sufficient flowing of metal, forging is usually divided into several levels. Transformation in every level is gradual, advantageous for controlling flowing direction. Quantity of level depends on shape and dimension of forging pieces, forgeability of metal and precision of work piece.
3. Press forging
Press forging is a forging method that metal is extruded and formed inside mold under the pressure at a low speed. Due to metal stressed for a long time, extrusion is not only carried out on the surface of forging piece, but also carried out in center. Therefore, for even inside and outside, the quality of products is also better than that of drop hammer forging.
Forging used for manufacturing the shell of cellphone can reduce time of CNC effectively, having low relative cost. Moreover, aluminum alloy whose aluminum content exceeds 95% can be chosen for anodic oxidation.
Manufacturing process:

  • Firstly, acquire structural parts of cellphone having higher thickness;
  • Then, mill off the unnecessary parts through CNC, acquiring integrated structural members combining metal and plastic;
  • Treat surface with anodic oxidation;
  • Lastly, glue antenna cover.

4. Upset forging
Upset forging means that forge one of ends of an even long rod. Clamp the rod in the mold; heat one of end to high temperature. Force the end along the axial direction, upsetting and forming.
5. Roll forging
Use two round rollers (25%~75% reduction of diameter; the other part can be cut into groove shape based on requirements). Put rod into the two rollers and tight it, then, continue rotating, roll compacting the rod, reducing diameter and pushing it forward; when the rollers rotate to opening position again, withdraw the rod back to original position for the next cycle rolling, or send the rod to another grove for other construction.

Properties of Forged Steel

Forged steel is often used in weapons, thanks to its strength and durability.
Forging steel is a metal-working process which involves the use of hammering or pressing techniques to alter the steel’s shape, followed by heat treatment. This method produces in the steel a number of properties which distinguish it from other treatments of this metal, for example casting, where liquid metal is poured into a mold and then left to solidify.
Strong and Durable
Steel forgings have a generally higher strength and are typically tougher than steel processed in other fashions. The steel is less likely to shatter on contact with other objects for example, making forged steel highly suitable for items such as swords. This increased strength and durability is a result of the way in which the steel is forced into shape — by pressing or by hammering — during the forging process. The steel’s grain is stretched by this process, and ends up aligned in one direction, as opposed to being random. Following the pressing or hammering, the forging is cooled in water or oil. By the end of the process, the steel is stronger than it would have been had it been cast, for example.
A steel forging’s strength isn’t consistent all the way through; instead, steel forgings are anisotropic, which means when the metal is worked on and deformation occurs, the steel’s strength is greatest in the direction of the resulting grain flow. This results in steel forgings which are strongest along their longitudinal axis, while in other directions, the forging will be weaker. This differs from steel castings, which are isotropic and therefore have almost identical properties in all directions.
Consistency Between Forgings
Since the process of forging is controlled and deliberate, with each forging undergoing the same steps, it’s typically possible to ensure a consistent material over the course of many different forgings. This is in contrast to cast steel, which is more random in nature due to the processes used.
Limit On Size
During the forging process, it’s more difficult to shape the metal, since forging occurs while the steel is still solid, unlike in casting where the metal has been reduced to its liquid form as part of the process. Since the metallurgist working with the steel will have more difficulty altering the metal’s shape, there’s a limit on the size and the thickness of the steel which can be successfully forged. The larger the metal section being worked on, the harder it is to forge.

The Difference Between Casting & Forging

Casting is the process where metal is heated until molten. While in the molten or liquid state it is poured into a mold or vessel to create a desired shape.

Forging is the application of thermal and mechanical energy to steel billets or ingots to cause the material to change shape while in a solid state.

Why use castings?

Casting service
Casting service

We use castings for a wide range of wearparts and components that are too large, complicated, intricate or otherwise unsuitable for the forging process. We can forge parts up to 50kgs but the sheer energy required to forge larger items make casting a much more viable alternative.

We currently cast mining and earthmoving components to 580 kg. We can cast up to 3000 kg if required. Manganese work hardening screens are one of our specialities. We have found that by carefully choosing alloys and applying proven methods of heat treatment, we can produce castings of high quality, strength and wearability. The casting process better lends itself to making parts where internal cavities are required.

The advantages of casting include:

  • No real upper size limit in casting weight
  • Large range of alloy choices

As forgings remain solid, custom alloys are far more difficult to get into production whereas with casting, alloys including Chrome, Nickel and Moly can be added at the molten stage.

  • Tooling is often less expensive than forge dies
  • Smaller production “runs” required
  • Complicated/complex parts are no problem
  • For general GET as well as large and complex components – casting is a fantastic method of manufacture.

Why use forgings?

Forged service
Forging service

Forging offers uniformity of composition and structure. Forging results in metallurgical recrystalisation and grain
refinement as a result of the thermal cycle and deformation process. This strengthens the resulting steel product particularly in terms of impact and shear strength.

Forged steel is generally stronger and more reliable than castings and plate steel due to the fact that the grain flows of the steel are altered, conforming to the shape of the part.

The advantages of forging include:

  • Generally tougher than alternatives
  • Will handle impact better than castings
  • The nature of forging excludes the occurence of porosity, shrinkage, cavities and cold pour issues.

The tight grain structure of forgings making it mechanically strong. There is less need for expensive alloys to attain high strength components.

The tight grain structure offers great wear resistance without the need to make products “superhard” We have found that, on a blank HRC 38-42 forged grinder insert wear/wash is about the same as a high alloy HRC 46-50 cast grinder insert. The difference being a HRC 46-50 casting does not have the ductility to handle high impact grinding.

Materials of Pipe Fittings

They are manufactured utilizing higher grade raw material, advanced machines and technologies.

  • Carbon steel:

    • SA234 WPB, SA234 WPC,SA42 WPL6, SA42 WPL3
    • WP1. MSS-SP75, WPHY,WPHY 46,WPHY 52
    • WPHY 56,WPHY 60,WPHY 65, WPHY 70
    • DIN 1629 St37, RST37.2 St52, STPG38
  • Stainless:

    • ASTM/ASME SA403 304,304L ,316, 316L, WP304L, 3 WP316 WP347 (H) ,WP317 (L),WP321.
    • DIN 1.4301, 1.4306, 1.4401, 1.4571
    • JIS SUS304,SUS304, SUS304L, SUS316, SUS316
  • Alloy:

    • ASTM/ASME SA234 WP12, WP11,WP22, WP5, WP9, WP91, ASTM B361 GR.3003-6061, ASTM B366 UNS
    • N04400,N08800, N08825 N1001-N10276-N10665, WPT2-WPT12
    • ASTM 182 F1, F5, F6, F7, F9, F11, F12, F22, F51, 16MnR Cr5Mo
    • 12Cr1MoV 10CrMo910 15CrMo 12Cr2Mo1, St45.8

Fitting Tolerance

Butt-welding is the process of joining two pieces of material together along a single edge in a single plane.

Fitting Tolerance

Alignment tolerances are concerned with the way that the ends of a fitting are cut. Exaggerated distortions are shown for clarity in the diagram below.

Butt Welding Pipe Fitting Draw - What is pipe fitting?

Tolerances are in millimeters. mm -ASME / ANSI B16.9

All Fittings 90, 45
Elbows and Tees
Reducers Caps 180 Returns



Pipe Size
at Bevel
at End
Center to End Dimension Overall
Center to
Back to
of Ends
Pipe Size
(in) D t A.B.C.M H E O K U (in) Q P
1/2to 21/2 +1.52-0.76 0.76 Not Less Than 87.5% of Nominal Thickness 1.52 1.52 3.05 6.35 6.35 0.76 1/2 to 4 0.76 1.51
3 to 31/2 1.52 1.52 1.52 1.52 3.05 6.35 6.35 0.75 5 to 8 1.52 3.05
4 1.52 1.52 1.52 1.52 3.05 6.35 6.36 0.76 10 to 12 2.29 4.83
5 to 8 +2.29-1.52 1.52 1.52 1.52 6.35 6.35 6.35 0.76 14 to 16 2.29 6.35
10 to 18 +4.06-3.05 3.05 2.29 2.29 6.35 9.65 6.35 1.52 18 to 24 3.05 9.65
20 to 24 +6.35-4.83 4.83 2.29 2.29 6.35 9.65 6.35 1.52 26 to 30 4.83 9.65
26 to 30 +6.35-4.83 4.83 3.05 4.83 9.65 32 to 36 4.83 12.7
32 to 36 +6.35-4.83 4.83 4.83 4.83 9.65

This process can be used on many types of materials, though metal and thermoplastics are the most common. When two sheets of steel are laid side-by-side and joined together along a single joint, this is an example of butt-welding.

Fitting standards and certifications

In pipe fittings as well, standards play a vital role. The manufacture and installation of pipe fittings is tightly regulated by various standards and codes.

Who decides on standards and specifications for butt weld fittings ?

Manufacturers of butt weld pipe fittings have to meet specifications and requirements of many organizations, to assure quality, compatibility and performance of their products.

Key national and international standards organizations focus on materials and end-user industries, including American Society for Testing and Materials (ASTM), American Society of Mechanical Engineers (ASME), International Organization for Standardization (ISO), Norway’s NORSOK, …

Some international organizations also focus on quality standards across all industries, such as International Organization for Standardization (ISO).
Large industrial end-users also have their own programs to certify individual manufacturing plants as meeting their criteria to be listed on their Approved Manufacturers List (AML).

All these certifications and approvals are valid for a specific period, and must be renewed regularly.

Types of pipe fittings standards:

Some widely used pipe fitting standards are as follows:

ANSI: The American National Standards Institute

ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns “schedule numbers”. These numbers classify wall thicknesses for different pressure uses.

ASME: American Society for Mechanical Engineers

This is one of the reputed organizations in the world developing codes and standards. The schedule number for pipe fitting starts from ASME/ANSI B16.

The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows:

  • ASME/ANSI B16.1 – 1998 – Cast Iron Pipe Flanges and Flanged Fittings
  • ASME/ANSI B16.3 – 1998 – Malleable Iron Threaded Fittings
  • ASME/ANSI B16.4 – 1998 – Cast Iron Threaded Fittings
  • ASME/ANSI B16.5 – 1996 – Pipe Flanges and Flanged Fittings
  • ASME/ANSI B16.11 – 2001 – Forged Steel Fittings, Socket-Welding and Threaded
  • ASME/ANSI B16.14 – 1991 – Ferrous Pipe Plugs, Bushings and Locknuts with Pipe Threads
  • ASME/ANSI B16.15 – 1985 (R1994) – Cast Bronze Threaded Fittings
  • ASME/ANSI B16.25 – 1997 – Buttwelding Ends
  • ASME/ANSI B16.36 – 1996 – Orifice Flanges etc.

ASTM International: American Society for Testing and Materials

This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM). This is a reputed scientific and technical organization that develops and publishes voluntary standards on the basis of materials, products, systems and services. This is a trusted name for standards. The standards covered by this organization covers various types of pipes, tubes and fittings, especially made of metal, for high-temperature service, ordinary use and special applications like fire protection. The ASTM standards are published in 16 sections consisting of 67 volumes.

AN: Here, “A” stands for Army and “N” stands for Navy

The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments. For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16″ or ¼”. It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread.

BSP: British Standard Pipe

BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring.

DIN: Deutsches Institut für Normung
This refers to the industrial pipe, tube and fittings standards and specifications from the DIN, Deutsches Institut für Normung which in English means the German Institute for Standardization. DIN is the German national organization for standardization and is ISO member body for that country.

DIN standard designation
The designation of a DIN standard shows its origin where # symbolizes a number:

  • DIN # : Used for German standards having mainly domestic significance or designed as the primary step toward international status.
  • DIN EN # : Used for the German edition of European standards.
  • DIN ISO # : Used for the German edition of ISO standards.
  • DIN EN ISO # : Used if the standard has also been adopted as a European standard.

Dash (-) size

Dash size is the standard used to refer to the inside diameter of a hose. This indicates the size by a two digit number which represents the relative ID in sixteenths of an inch. This is also used interchangeably with AN fittings. For example, a Dash “8” fitting means an AN 8 fitting.
A standard hose guide is given below:

Hose Size In Nominal ID Inch Dash Size Standard Dash Size
1/4 3/16 -04
3/8 5/16 -06
1/2 13/32 -08
3/4 5/8 -12
1 7/8 -16
1 ½
1 ¼ 1 1/8 -20

ISO: International Organization for Standardization
ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows:

“ISO[/IEC] [IS] nnnnn[:yyyy] Title” where

  • nnnnn: standard number
  • yyyy: year published, and
  • Title: describes the subject

JIS: Japanese Industrial Standards

This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations.

NPT: National Pipe Thread

National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting.

What is an MTR ?

Material Test Reports (MTRs) are provided by manufacturers to certify physical properties and metal grade or alloy for each fitting, flange, pipe, or valve. This MTR is essential for demanding applications (pressure, temperature, corrosion, abrasion,…)

Sizes and Dimensions of Pipe Fittings

Pipe fitting dimensions are in either metric or Standard English. Because pipe fitting covers Pipe Fitting Dimensions several aspects, only the most common pipe fitting sizes can be given here.

How are pipe fittings measured?

Pipe fittings are measured by their diameter, wall thickness (known as “schedule”), and shape or configuration. (Fittings are also defined by their material grade and whether they are welded or seamless.)

Diameter refers to outside diameter of a pipe or fitting.

The North American standard is known as Nominal Pipe Size (NPS). The International Standard is known as Diameter Nominal (DN). Pipes and fittings are actually made in similar sizes around the world: they are just labeled differently.

From ½ in to 12 inch “Nominal Pipe Size”, outside diameters are slightly larger than indicated size; inside diameters get smaller as schedules grow.

From 14 in and larger “Nominal Pipe Size”, outside diameters are exactly as indicated size; inside diameters get smaller as schedules grow.
As with other North American standards (inch, foot, yard, mile, …), many pipe standards (diameters up to 12 inch and wall thickness) are based on historical precedents (a toolmaker’s dies during US Civil War) rather than a “scientific” method.

Schedule Numbers

The schedule numbers are used by the ANSI (American National Standards Institute) to denote wall thickness. The schedule numbers encompass all pipe dimensions beginning at NPS 1/8” up NPS 36”. Note that this configuration is only for fittings that match with a particular ANSI schedule number.

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures.

  • Schedule, often shortened as sch, is a North American standard that refers to wall thickness of a pipe or pipe fitting. Higher schedules mean thicker walls that can resist higher pressures.
  • Pipe standards define these wall thicknesses: SCH 5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS. (S following a number is for stainless steel. Sizes without an S are for carbon steel.)
  • Higher schedules are heavier, require more material and are therefore more costly to make and install.

What does “schedule” mean for pipe fittings?

Schedule, often shortened as SCH, is a North American standard that refers to wall thickness of a pipe or pipe fitting.

What is schedule 40, SCH80?

Higher schedules mean thicker walls that can resist higher pressures.

Pipe standards define these wall thicknesses: SCH 5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS.
(S following a number is for stainless steel. Sizes without an S are for carbon steel.)

Higher schedules are heavier, require more material and are therefore more costly to make and install.

Why are fittings sometimes thicker and heavier than pipes to which they are connected?

Fittings are sometimes thicker than their connecting pipes to meet performance requirements or due to manufacturing reasons.
Due to fitting geometry, stress is very different when compared to a pipe. Using extra material is often necessary to compensate for such additional stress, especially for tees and tight curve elbows.
Fitting manufacturers may not always stock plates or pipes for all metal grades or sizes. When responding to an order, manufacturers always use the right metal or alloy, but sometimes made with next-higher available plate or pipe size while still respecting specified inside diameters.

Tolerance For butt Welding Fittings

What to Check During Fittings Dimension Inspection?

Following to be confirmed during inspection of pipe fitting dimensions

  • Diameter
  • Length
  • Thickness schedule no
  • Straightness & perpendicularity of the fittings ends
  • Degree of elbows & bends
  • And Concentricity of reducer

Bevelled Ends of Pipe Fittings

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”.

Welding Bevel ASME / ANSI B16.9 and ASME / ANSI B16.28

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).

Our in-hourse R&D team developed bevel ends equipment are good using in thickness 2mm to 20mm pipe fittings, guarantee high efficiency and high quality.

End bevel

Send us your technical drawings

These weld edge preparation requirements are also incorporated into the ASME standards (e.g., B16.9, B16.5, B16.34).


ASME B16.25 sets standards for the preparation of the ends of components that need to be welded together.

ASME B16.25 sets standards for the preparation of the ends of components that need to be welded together

Cut square or slight chamfer, at manufacturer’s option for :

  • t ≤ 0.19” carbon steel or ferritic alloy steels
  • t ≤ 0.12” austenitic alloy steels

Buttweld Fittings general

A pipe fitting is defined as a part used in a piping system, for changing direction, branching or for change of pipe diameter, and which is mechanically joined to the system.

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

Testing for fittings

The most common non distructive tests (NDT) for pipe fittings:

  • Positive material identification (PMI): identification of the chemical composition of the metal used to manufacture the fitting. Uses PMI sensors, including X-ray fluorescence or optical emission spectrometry. This test is frequently executed for high value materials, from duplex steel onwards.
  • Penetrating liquids: this is a low-cost test to detect cracks or abnormal porosity on the surface of the fittings, and is executed by applying a special liquid to its surface.
  • Ferrite content: this test aims to measure the ferrite content for duplex, super duplex and stainless steel materials to make sure the metal is able to achieve the yield strength, fracture toughness and corrosion resistance it is meant to reach. Ferrite content is measured in weld seams by magnetic induction.
  • Hydrostatic test / hydro testing (pressure testing): the fitting gets filled with a test liquid (example water) and a pressure is applied to check if any pressure loss occurs (which would indicate manufacturing defects)
  • Magnetic particles: by means of a magnetic field, possible surface discontinuities or weakness can be identified
  • Macrography: 2 / 3 D pictures of items visible to naked eye.
  • Micrography: pictures at the microscope to see the microgranular structure of the metal and other details not visible at the naked eye
  • Pneumatic pressure: the fitting gets filled with pressurized air; measurements are taken to see if there is pressure loss due to any defects.
  • Radiography: X-rays / gamma rays to detect imperfections leading to possible quality defects

Out of the above tests, the pressure testing is one of the most commonly specified, especially for mission critical fittings in the pipeline.

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at Please notice that you might be interested in the other technical articles we’ve published:

What is the difference between elbow and bend?

Elbow is a standard fitting but bends are custom fabricated. In bends as the pipe is bent and there is no welding involved, there is less pipe friction and flow is smoother. Bend has a larger radius then elbows. Generally the most basic difference is the radius of curvature.

What is a 1.5 D Bend?

The nomenclature “1.5D” and “3D” refers to the radius of the bend of the fitting to the nominal diameter D of the fitting.

What is a 2d Bend?

A 2D bend on a 6-inch pipe would have a 12-inch centerline radius. This would be referred to as a long radius bend, which includes 2D up to and including 5D bends or the center line radius that is 5 times the pipe’s respective diameter.

How tight should thread pipe fittings be?

In general terms you want to aim for 2 to 3 full turns after hand tight. If it still feels loose, complete another full turn. A lot of plumbers will use both teflon tape and pipe dope. Depending on the thickness of the teflon tape you will want to use 3 to 6 wraps in the direction on the threads.

What is pipe fitting?
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What is pipe fitting?
Steel pipe fittings are all pressure bearing fittings. According to the different type of end connections, it can be divided into six categories: butt welding pipe fittings (including two kinds of weld and no weld), socket welding and threaded pipe fittings, flange fittings, spigot fittings, buttress fittings.
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