What are pipe fittings solutions?

What are pipe fittings?

Pipe fittings are the core of pipe components made from steel pipe and steel sheet by welding or mandrel/mold forming. Pipe fittings are used for transportation, changing direction, branching from a main or reducing the size of a pipe line.

Types of Pipe Fittings

Pipe fittings are the general name of parts and components that play the role of connection, control, direction change, diversion, sealing and support in the pipeline system. Pipe fittings are parts that connect pipes into pipes.

Our products includes Elbows, Laterals, Crosses, Caps, Tees, Reducers, Couplings, Stub ends, Etc., both in standard and specialty applications.
It mainly includes the following:

• 1. Pipe fittings used for connecting pipes include: flange, union, pipe hoop, clamp, ferrule, throat hoop, etc.
• 2. Pipe fittings that change the direction of pipes: elbows and bends.
• 3. Pipe fittings for changing pipe diameter: reducing (reducing pipe), reducing elbow, branch pipe support and reinforcing pipe.
• 4. Add pipe fittings for pipeline branches: tee and cross.
• 5. Pipe fittings for pipeline sealing: gasket, raw material belt, thread hemp, blind flange, pipe plug, blind plate, head and welding plug.
• 6. Pipe fittings used for pipeline fixation: snap ring, drag hook, lifting ring, support, bracket, pipe clamp, etc.

Butt-Welding Fittings

Butt-weld fittings or wrought fittings are the most common type of steel fittings used for pipelines mostly above 4 inches in diameter. Pipe fittings change the pathway of the pipeline (elbows with 45, 90 and 180 degrees angle curve), reduce/increase its flow conveyance capacity (concentric and eccentric reducers), branch (tees, cross) or blind it (butt weld cap). These fittings are supplied with ends chamfered for connection to pipe by means of butt welding.

Elbow
LR, SR, Reducing and Mitered

Among all of the fittings, elbow is the one most often used.
Elbow is used when a pipe changes direction, they can turn up, turn down, turn left, right, or any angle in between.
Elbows can be classified as one of the following:
• 90° Elbow
• 45° Elbow
• 180° Return
• Reducing Elbow
• Mitered Elbow
Tee
Straight, Reducing, Cross

The name of this fitting comes from its resemblance to the letter T.
It is a tee fitting used to make perpendicular connections to a pipe
Two types of tees are used in the piping industry:
• Straight: all three outlets are the same pipe size.
• Reducing: branch outlet is a smaller pipe size.
Reducer
Concentric, Eccentric

When the piping designer wants to reduce the diameter of a straight run of pipe, a reducing fitting must be used.
Two types of Reducers are used in the piping industry:
• Concentric: having a common centerline.
• Eccentric: having offset centerlines.
Lateral

For Low-pressure applications

Cap

To block off the end of a line

Pipe caps are used to block off the end of a line by welding it to the pipe.

Caps should never be stored in a position to trap rain water or sand.
Lap Joint Stub-End
It is mated with a lap joint flange.

The stub end is used in lines requiring quick disconnection.
The lap forms a gasket surface that replaces the gasket surface of a flange, and are mated with a lap joint flange. Stub ends should not be confused with stub-ins, the latter being one pipe stubbed into another pipe and welded.

Specification of the Butt-Welding Fittings

• ASME B16.9, ASME B16.28 and, MSS SP43 are the key specifications covering the dimensions and the manufacturing tolerances of butt weld fittings. ASME B16.25 covers the preparation of butt weld connections between pipes and fittings. ASME B16.49 covers the marking details.
• The wrought fitting materials conform to ASTM A234, A403, or A420, the grades of which have chemical and physical properties equivalent to that of the mating pipe.

Pressure Test of the Butt-Welding Fittings

• Pressure testing of the fittings is not required by either standard. However, the fittings are required to be capable of withstanding, without leakage, a test pressure equal to that prescribed in the specification of the pipe with which the fitting is recommended to be used.

Disadvantage of the Butt-Welding Fittings

• One of the major disadvantages of butt-welded systems is that they are not easy to dismantle.

Cost of the Butt-Welding Fittings

• Material costs are low, but labor costs are moderate to high due to the need for specialized welders and fitters.

Size of the Butt-Welding Fittings

• Most butt-welded piping installations are limited to NPS 2¹⁄₂ (DN65) or larger. There is no practical upper size limit in butt-welded construction.
• Butt-welding fittings and pipe system accessories are available down to NPS ¹⁄₂ (DN15). However, economic penalties associated with pipe end preparation and fit-up, and special weld procedure qualifications normally preclude the use of butt-welded

Other Properties of the Butt-Welding Fittings

• The interior surface of a butt-welded piping system is smooth and continuous which results in low pressure drop.
• The system can be assembled with internal weld backing rings to reduce fit-up and welding costs, but backing rings create internal crevices, which can trap corrosion products. In the case of nuclear piping systems, these crevices can cause a concentration of radioactive solids at the joints, which can lead to operating and maintenance problems. Backing rings can also lead to stress concentration effects, which may promote fatigue cracks under vibratory or other cyclic loading conditions. Butt-welded joints made up without backing rings are more expensive to construct, but the absence of interior crevices will effectively minimize ‘‘crud’’ buildup and will also enhance the piping system’s resistance to fatigue failures.

Materials of the Butt-Welding Fittings

Carbon Steel
ASTM A234 WPB , WPBW, WPHY 42, WPHY 46, WPHY 52, WPH 60, WPHY 65 and WPHY 70
Low Temperature Carbon Steel
ASTM A420 WPL3 , A420 WPL6
Stainless Steel
ASTM A403 WP (Gr. 304, 304H, 304L, 309, 310, 316, 316L, 317L, 321, 347, 904L)
Alloy Steel & High Yield Steel
ASTM A234 (Gr. WP1, WP5, WP9, WP11, WP12, WP22, WP91)
ASTM A860 (WPHY 42 – WPHY 46 – WPHY 52 – WPHY 56 – WPHY 60 – WPHY 65 – WPHY 70 – WPHY 80 only as per MSS-SP75)
Duplex Steel
ASTM A815 (UNS S31803, S32205, S32760, S32750)
Nickel Alloy
ASTM SB 336, ASTM SB 564 / 160 / 163 / 164 / 166 / 472, UNS 2200 (NICKEL 200) , UNS 2201 (NICKEL 201 ) , UNS 4400 (MONEL 400 ) , UNS 8020 ( ALLOY 20 / 20 CB 3 ) , UNS 8825 INCONEL (825) , UNS 6600 (INCONEL 600 ) , UNS 6601 (INCONEL 601) , UNS 6625 (INCONEL 625), UNS 10276 (HASTELLOY C 276)

Standard of the Butt-Welding Fittings

ASME B16.9, ASME B16.28 and, MSS SP43 are the key specifications covering the dimensions and the manufacturing tolerances of butt weld fittings. ASME B16.25 covers the preparation of butt weld connections between pipes and fittings and ASME B16.49 covers the marking details.
ASME B16.9 and B16.28
This Standard covers overall dimensions, tolerances, ratings, testing, and markings for wrought carbon and alloy steel factory-made butt-welding fittings of NPS 1/2 through 48. It covers fittings of any producible wall thickness. This standard does not cover low pressure corrosion resistant butt-welding fittings. See MSS SP-43, Wrought Stainless Steel Butt-Welding Fittings. Short radius elbows and returns, which were previously included in ASME B16.28-1994, are included in this standard. B16.9 is to be used in conjunction with equipment described in other volumes of the ASME B16 series of standards as well as with other ASME standards, such as the Boiler and Pressure Vessel Code and the B31 Piping Codes”. (source: ASME)
MSS SP 43
The MSS SP 43 sets the dimensions, tolerances, and markings for butt weld fittings for low pressure, corrosion resistant applications. It covers only fittings for use with Schedule 5S or 10S pipe, for all NPS sizes listed in ASME B36.19M, except that for short pattern stub ends suitable for use with Schedule 40S are also shown. Essentially, MSS SP 43 is the reference standard for lightweight corrosion resistant butt weld fittings (stainless steel, duplex).
ASME B16.25
ASME B16.25 sets standards for the preparation of the ends of components that need to be welded together. As stated in the ASME website: “This Standard covers the preparation of butt-welding 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 tolerances). Coverage includes preparation for joints with the following: no backing rings; split or non-continuous backing rings; solid or continuous backing rings; consumable insert rings; gas tungsten arc welding (GTAW) of the root pass” (source: ASME).
ASME B16.49
The ASME B16.49 Norm covers the manufacturing, marking, design, material, testing, and inspection requirements for factory-made bends of carbon steel materials having controlled chemistry and mechanical properties, produced by the induction bending process, with or without tangents. This standard covers induction bends for transportation and distribution piping applications (e.g., ASME B31.4, B31.8, and B31.11).

Forged Fittings

Socket Weld Fittings

Socket weld fittings are used for applications where a strong and long-lasting connection is required. These type of pipe fittings feature a socket where the connecting pipe has to be fitted and welded (with a fillet-type seal weld). Socket weld connections are very reliable but are time-consuming to install, due to the necessary welding operations. Socket weld fittings are available in sizes from 1/8 to 4 inches and in pressure ratings from classes 2000 to 9000.
The typical applications for socket weld fittings are:
• Steam
• Explosive fluids/gas
• Acids and toxic fluids
• Long service / durable installations

Threaded Fittings

Threaded fittings are used for non-critical pipelines such as water distribution, fire protection and cooling systems (low-pressure applications not subject to vibration, elongation and bending forces). Threaded fittings are not suited for fluids with variable temperatures, as sudden changes may crack the connection. Threaded fittings are available in gray cast iron, malleable iron, carbon steel ASTM A105, stainless steel A182 F304/F316 and in sizes from 1/8 inch to 4 inches with pressure ratings between 2000 and 6000. Although different types of threads are available, the most common type is the NPT (national pipe thread).

Elbow

Elbows are used to bend the pipework layout at 45 or 90 degrees. Forged elbows are manufactured according to ASME B16.11. A special type of elbow is the so-called “street” type.

Tee

Tees are a forged steel fitting used to combine or divide process flow and Reducing Tees additionally allow for pipe size change. The run outlets of the tee are the two in-line outlets, and the branch is the third outlet.

Cross

Cross fittings are used to combine or split pipe or tube sections. Cross fittings have one input and three outputs (or vice versa) that intersect at 90 degree angles. All three designs come in standard designs (in which all outlets/inlets are the same diameter) and reducing designs (in which one or more is a different size).

Union

• Unions are used as an alternative to flanges connection in low-pressure small bore piping placed within a piping configuration that will allow the assembly to be disassembled for inspection, repair, or replacement.
• Unions should be positioned in locations that will facilitate the easy removal of critical pieces of equipment.
• 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.

Coupling

• It is used to connect two lengths of pipe, and Half-coupling is screwed onto the pipe, while the other end is made to be tightly inserted, or welded, onto the other end to pipe or vessel.
• Standard Couplings have female threads or open sockets at both ends, whereas reducing couplings connect smaller pipes to larger ones.
• There are three types of coupling available;
1. Full Coupling
Full Coupling is used for connecting small bore pipes. It used to connect pipe to pipe or pipe to swage or nipple. It can be threaded or socket ends types.
2. Half Coupling
Half Coupling is used for small bore branching from a vessel or large pipe. It can be threaded or socket type. It has a socket or thread end on only one side.
3. Reducing Coupling
Reducing coupling is used to connect two different sizes of pipe. It is like concentric reducer that maintains a center line of the pipe but small in size.

Cap and Head Plug

The plug, like a cap, is designed to close off the end of a run of pipe.
• Plugs are manufactured for screwed fittings with male threads and are screwed into the end of a pipe to create a seal, whereas, Caps have female threads.
• They come with different head types, including: hex, square, and round.

Nipple

To facilitate the assembly of screwed and socket-weld fittings, small lengths of pipe called pipe nipples are used between fittings.
• Many companies will use 3” as the standard minimum for pipe nipples. This length will accommodate the amount of pipe lost inside the fitting on each end as well as provide sufficient wrench clearance during assembly for the larger screwed and socket-weld pipe sizes.

Boss

Head Bushing

Bushings are forged steel fittings that allow for a change in pipe size. Pictured here is the hex head bushing, which is most commonly used.

Insert

Swage Nipples

Swages are functionally similar to reducers to make reductions in the line size on a straight run of pipe, However, they are specifically designed for screwed and socket-weld pipe.
• They have male (external) threads and can be connected to other screwed fittings without the use of a pipe nipple.
• Swages, like reducers, are available in either a concentric or eccentric shape.
• Swages are also manufactured with different preparations on the two ends.

• BBE—bevel both ends;
• TBE—thread both ends;
• PBE—plain both ends;
• BLE/TSE—bevel large end/thread small end;
• PLE/TSE—plain large end/thread small end.

Standard Specification for Forged Swage Nipple
Dimensions	ASME B16.11 BS 3799 NPT threads conform to ASME B1.20.1
Size	1/4”-4”
Type	–
Class	2000 LBS – 9000 LBS
Variation	BBE, TBE, PBE, BLE/TSE, PLE/TSE
Test Certificate	MTC as per EN10204 Type 3.1 and EN10204 Type 3.2

Specification of the Forged Fittings

For socket welding fittings, the pressure rating must be matched to the pipe wall thickness to ensure that the flat of the band can accommodate the size of the fillet weld required by the applicable code.

Pressure of the Forged Fittings

These fittings are available in four pressure-temperature rating class.
• 2000 class fittings are available in only in threaded type.
• 3000 ~ 6000 class fittings are available in both Threaded and Socket Weld types.
• 9000 class fittings are available in only socket weld type.

Thread of the Forged Fittings

• Most screwed fittings are manufactured with internal, female threads per American Standard and API thread guidelines
• Some fittings, such as plugs and swages, however, are manufactured with external threads.
• Internal threads of threaded fittings are in accordance with ASME B1.20.1-Pipe Threads, General Purpose (Inch).

Disadvantage of the Forged Fittings

Fatigue resistance is lower than that in butt-welded construction due to the use of fillet welds and abrupt fitting geometry, but it is still better than that of most mechanical joining methods.

Application of the Forged Fittings

The internal crevices left in socket-welded systems make them less suitable for corrosive or radioactive applications where solids buildup at the joints may cause operating or maintenance problems.
• Lines containing high pressure and temperature commodities, which are subject to movement and vibration, require fittings made of forged steel.
• Socket-welded construction is a good choice wherever the benefits of high leakage integrity and great structural strength are important design considerations.

Size of the Forged Fittings

Screwed and socket-weld fittings are normally reserved for installations using fittings 4” and smaller. They are usually available in cast iron, malleable iron, or forged steel.

Cost of the Forged Fittings

Construction costs are somewhat lower than with butt-welded joints due to the lack of exacting fit-up requirements and elimination of special machining for butt-weld end preparation.

Marking and Packing of the Forged Fittings

Products are packaged to ensure that there is no damage during transit. In case of exports, standard export packaging is done in wooden cases. All forged fittings are marked with Grade, Lot No, Size, Degree and our trade mark. On special requests we can also, make custom marking on our products.

Materials of the Forged Fittings

Carbon Steel
ASTM A105
Low Temperature Carbon Steel
A350 (LF1, LF2, LF3)
Stainless Steel
ASTM A182 (Gr. 304, 304H, 309, 310, 316, 316L, 317L, 321, 347, 904L)
Alloy Steel & High Yield Steel
ASTM A182 (Gr. F 5, F 9, F 11, F 12, F 22, F 91)
ASTM A694 (Gr. F42, F46, F56, F52, F60, F65, F70)
Duplex Steel
ASTM A182 (Gr. F51, F52, F53, F54, F55, F57, F59, F60, F61),
UNS S31803, S32205, S32760, S32750
Nickel Alloy
ASTM SB 336, ASTM SB 564 / 160 / 163 / 164 / 166 / 472, UNS 2200 (NICKEL 200) , UNS 2201 (NICKEL 201 ) , UNS 4400 (MONEL 400 ) , UNS 8020 ( ALLOY 20 / 20 CB 3 ) , UNS 8825 INCONEL (825) , UNS 6600 (INCONEL 600 ) , UNS 6601 (INCONEL 601) , UNS 6625 (INCONEL 625), UNS 10276 (HASTELLOY C 276)

Standards of the Forged Fittings

ASME B16.11
This standard covers pressure-temperature ratings, dimensions, tolerances, marking, and material requirements for forged carbon and alloy steel. Acceptable material forms are forgings, bars, seamless pipe, and seamless tubes which conform to the fittings chemical compositions, melting practices, and mechanical property requirements of ASTM A105, A182, or A350.
MSS-SP 83
This Standard Practice establishes envelope and other essential dimensions, finish, tolerances, testing, marking, material, and minimum performance requirements for forged carbon steel, alloy steel, stainless steel, and nickel alloy pipe unions, socket welding and threaded ends.
MSS-SP 95
This Standard Practice covers dimensions, finish, tolerances, marking, and material for carbon steel and alloy steel Swaged Nipples (male end reducing fittings), NPS 1/4 through NPS 12 and Bull Plugs (hollow or solid male closures) NPS 1/8 through NPS 12. These fittings are made with ends that are threaded, beveled, square cut, grooved, or any combination of these. Both concentric and eccentric Swaged Nipples are included.
ASME B1.20.1
ASME’s widely-referenced B1.20.1 Standard on Pipe Threads, General Purpose, Inch covers dimensions and gaging of the world’s most common pipe threads: NPT, NPSC, NPTR, NPSM, and NPSL.

Special Fittings

Special fittings are all those fittings manufactured based on specific customer requirements to fulfill.

Types of Special Fittings

Out-Lets

Out-lets (also known as O-lets) are fittings which provide an outlet from a larger pipe to a smaller one (or one of the same size). The main pipe onto which the branch connection is welded is usually called the Run or Header size. The pipe to which the branch connection provides a channel is usually called the Branch or Outlet size. Branch connections are in all sizes, types, bores, and classes, in a wide range of carbon steel, stainless steel, chrome-moly, and other alloys.
Whenever branch connections are required in size where reducing tees are not available and/or when the branch connections are of smaller size as compared to header size, O-lets are generally used.

Weldolet
Weldolet is the most common of all branch connections, and is welded onto the outlet pipe. The ends are beveled to facilitate this process, and therefore the weldolet is considered a butt-weld fitting. Weldolet’s are designed to minimize stress concentrations and provide integral reinforcement.
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Specifications for carbon steel forgings in accordance with ASTM A105.
• This is a buttweld connection used for making 90 degree branching for high pressure, high temperature piping and pressure vessels.
• Each outlet size is available to fit any run curvature.

Sockolets
Sockolets are similar to Weldolets, with the difference that the branched pipe sits, and can be welded, on the socket present in the inner part of the branch fitting. Sockolets are classified as “socket fittings” and are available in classes 3000#, 6000# and 9000#. They are used for 90 degrees branched pipe connections and can be size on size (the bore of the fitting matches the bore of the run pipe) or reducing (the fitting has a smaller bore size).
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Specifications for carbon steel forgings in accordance with ASTM A105.
• Each outlet size is available to fit any run curvature.

Threadolet
Threadolets are similar to Weldolets, but the branched pipe is in this case screwed with the fitting and not welded. Threadolets belong to the family of “threaded fittings” and are available in classes 3000# and 6000#. The threaded end is generally of the NPT type (National Pipe Thread, the American standard).
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Specifications for carbon steel forgings in accordance with ASTM A105.
• Each outlet size is available to fit any run curvature.

Sweepolet
Sweepolets are contoured, integrally reinforced, butt weld branch connections suited for low stresses and long fatigue service. The weld on the run pipe side can be easily inspected with radiographic examination (RX or RT), ultrasounds (UT) and other non-destructive testing methods. They are available in classes 2000#, 3000# and 6000#.
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Specifications for carbon steel forgings in accordance with ASTM A105.
• Each outlet size is available to fit any run curvature.
• Class 2000 – for use with Sch. 40 pipe.
• Class 3000 – for use with Sch. 80 pipe.
• Class 6000 – for use with Sch. 160 pipe.

Nipolet
Nipolet is a one piece fitting for valve take-offs, drains and vents. Manufactured for Extra Strong and Double Extra Strong applications in 3.1/2 in to 6.1/2 in lengths. It is 90° branch connection and comes in different types of ends that suit for butt welding, socket welding or threaded joint
• Class 3000 – for use with Sch. 80 pipe.
• Dimensions and tolerances in accordance with ANSI/ASME B16.11 and MSS SP-97.
• Specifications for carbon steel forgings in accordance with ASTM A105.
• Threads in accordance with ANSI/ASME B1.20.1.
• Each outlet size is available to fit any run curvature.
• Outlet combinations fit a number of run pipe sizes, and fittings are marked accordingly.
• Nipolets come in 3 1/2″, 4 1/2″, 5 1/2″ and 6 1/2″ lengths.
• XS and XXS represent the nipple part of the nipolet.

Latrolet
There are some special olets also used in piping such as Latrolet that is used for taking branch which is not at 90 degrees to run pipe. Latrolet comes in a 45°or any other special degree as required by purchaser. End connections of a Latrolet can be butt welded, socket welded or threaded.
• Class 3000 – for use with Sch. 80 pipe.
• Class 6000 – for use with Sch. 160 pipe.
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Dimensions and tolerances in accordance with ANSI/ASME B16.11
• Specifications for carbon steel forgings in accordance with ASTM A105
• Threads in accordance with ANSI/ASME B1.20.1.

Elbolet
Elbolet is a special type of olets which fits on elbow surface. It is 90° branch connection and comes in different types of ends that suit for butt welding, socket welding and threaded joint
• Class 3000 – for use with Sch. 80 pipe.
• Class 6000 – for use with Sch. 160 pipe.
• Dimensions and tolerances in accordance with ANSI/ASME B16.9, ANSI/ASME B16.25 and MSS SP-97.
• Dimensions and tolerances in accordance with ANSI/ASME B16.11
• Specifications for carbon steel forgings in accordance with ASTM A105
• Threads in accordance with ANSI/ASME B1.20.1.

Coupolet
Coupolet are designed for use in fire protection sprinkler systems and other low pressure piping applications. manufactured with NPT female threads for 300# service.
• Threads in accordance with ANSI/ASME B1.20.1.

Flangolet
Flangolet is similar to a weldolet or a nipolet, with the shape being alike to a long weld neck flange. Flangolets guarantee water-tight branch connections at a 90° angle, and functions like that of a weldolet, acting as a complementary branch connection instead of a tee or elbow.

Barred Tee
A barred tee (pigged 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. The bars are installed so they are flush with the inside diameter of the pipeline to keep the pig from hanging up when it passes through. The bars should be of a similar or identical material as the parent material.
The size of the bars on the tee should be small enough so that they do not restrict the flow from the branch connection. However, they should be large enough to prevent breakage based on the flow rate through the branch connection of the tee.
Barred tees are pipe fittings with two outlets, one at 90 ° to the connection to the main line that has tiny holes. Barred tees can either be extruded or fabricated and are used to connect two pieces of pipe or fittings. Barred tees are used in pipelines that are pigged.

It really depends on the kind of pig you are running. A mandrel pig will never make the turn into any size branch. A foam pig will pretty much go through whatever pipe has the lower pressure (I once had a 10-inch uncoated foam pig go through a 2-inch weld-o-let on a receiver barrel, but it took a while and did not remain intact). Realistically, I always bar tees since most company standards only allow reducing tees to be used down to 1/2 the run diameter (i.e., I can use a 10X6 tee, but not a 10X4 if I could buy one). 1/2 the diameter can take a coated foam pig and some turbo pigs.

Pipe Bends
A pipe bend is the generic term for what is called in piping as an “offset” – a change in direction of the piping. A bend is usually meant to mean nothing more than that there is a “bend” – a change in direction of the piping (usually for some specific reason) — but it lacks specific, engineering definition as to direction and degree. Bends are usually custom-made (using a bending machine) on site and suited for a specific need.
Pipe bends typically have a minimum bending radius of 1.5 times pipe radius (R). If this bending radius is less than 1.5R, it is called Elbow. Reference to any international / industry standard need to be traced. 1.5, 3 and 4.5 R are the most common bending radii in industry. A pipe bend typically flows smoother since there are not irregular surfaces on the inside of the pipe, nor does the fluid have to change direction abruptly.
Generally Pipe bends can be manufactured from seamless or welded pipes, but the choice is made taking into consideration the technical challenges involved. Increasing number of customers in the industry are choosing pipe bends as a preferred option for modern piping systems, as good quality pipe bends significantly reduce the need for welding and use of pipe fittings. Use of bends in piping systems also improves the flow of fluids in the piping system.

We Would Like To Introduce Ourselves as the reputed supplier of Long Radius Bend, Piggable Bend, Hot Bend, Hot Induction Bend, U Bend, J Bend, and Customized Bend.
We can offer Pipe Bends in a variety of materials and wide range of radius and diameter as per project specification.

Hot Induction Bends
Induction Bending is a controlled means of bending pipes through the application of local heating using high frequency induced electrical power.
Originally used for the purpose of surface hardening steels, induction technology when used in pipe bending consists basically of an induction coil placed around the pipe to be bent. The induction coil heats a narrow, circumferential section of the pipe to a temperature of between 850 and 1100 degrees Celsius (dependent on the material to be formed). As the correct bending temperature range is reached, the pipe is moved slowly through the induction coil whilst the bending force is applied by a fixed radius arm arrangement.

Long Radius Bend
To keep the client satisfied, we supply high quality Extra Long Radius Bends like 3D & 5D & 10D. Being a quality-oriented organization, we assure our clients that these products are best in quality. Our skilled professionals only utilize fine quality assured raw material, while manufacturing the entire range. Moreover, our offered range can be available in a wide range of sizes and shapes, as per the requirements of our esteemed clients.
The most important application for these pipe fittings is in heater coils and heat exchangers.

Piggable Bend
These Butt-weld Piggable Bend are used for connecting pipes of different diameters. Our Bends are demanded by all due to their less maintenance, high tensile strength and excellent finish. These Piggable Bends are available in different specification, grades, shapes & thickness as per the clients’ requirements.

Manufacturing Process of Pipe Bends

The production of high-quality bends depends on the manufacturing process of the steel pipe that is transformed into the bend.
Obtaining the most suitable chemical composition is also important as this enables the recovery of the pipe’s material properties following the bending process. Depending on pipe dimensions, grades and final bending conditions, alloying elements can be added to the steel in order to guarantee the required hardness and mechanical properties and to ensure that the bend’s chemistry matches as much as possible the line pipe’s chemistry.
Heat treatment is carried out on each bend in order to achieve the required mechanical properties after bending. For critical applications, such as high-strength steel, heavy wall, sour service or low-temperature, we also perform full quenching and tempering after bending, as a preferred process.
Machining of the bend ends guarantees optimum tolerances of inside diameters, as we ensure the bend has at least the minimum working tolerances of the mother pipe.

Pipe bending techniques are varied and offer different advantages and disadvantages depending on the function of the bend and the type of material being bent. Some use mechanical force and some use heat treatment, the most common are as follows:
Press Bending
Press bending is the simplest and cheapest method of bending cold pipe and tube. The pipe or tube is restrained at two eternal points and a ram in the shape of the bend advances on the central axis and deforms the pipe.
The bent pipe or tube is prone to deformation on both the inside and outside curvature. The pipe or tube is often deformed into an oval shape depending on the wall thickness of the material. This process is used where a consistent cross section of the pipe is not required.

Rotary Draw Bending
This is the most commonly used style of bender for bending pipe and tube where maintaining a good finish and constant diameter is important.
Rotary draw benders (RDB) are precise in that they bend using tooling or “die sets” which have a constant center line radius (CLR). The die set consists of two parts: The bend die creates the shape to which the material will be bent. The pressure die does the work of pushing the straight material into the bend die while traveling the length of the bend. Often a positioning index table (IDX) is attached to the bender allowing the operator to reproduce complex bends which can have multiple bends and differing planes.

3-Roll Bending
3-roll bending is also used for producing work pieces with large bending radii. The method is similar to the ram bending method, but the working cylinder and the two stationary counter-rollers rotate, thus forming the bend. Normally there are 2 fixed rollers and one moving roller and the work piece is passed forward and backward through the rollers while gradually moving the working roller closer to the counter rollers which changes the bend radius in the pipe.
This method of bending causes very little deformation in the cross section of the pipe and is suited to producing coils of pipe as well as long sweeping bends like those used in powder transfer systems where large radii bends are required.

Heat Induction Bending
In the case of heat induction, a coil is placed around the pipe. The coil heats a section of the pipe to a temperature between 430 and 1,200 °C. The temperature depends on the material. The pipe passes through the coil at a gradual rate while a bending force is mechanically applied to the pipe. The pipe is then quenched with either air or water spray. The products thus obtained are generally of high quality, but cost significantly more to produce.

Sand Packing Hot-Slab Bending
In the sand packing process the pipe is filled with fine sand and the ends are capped. The pipe is then heated in a furnace to 870 C or higher. The pipe is then placed on a slab with pins set in it. The pipe is then bent around the pins using a winch, crane, or some other mechanical force. The sand in the pipe minimizes distortion in the pipe cross section. It is an old process but one that hasn’t really been improved on for its flexibility when it comes to unique applications, and so is still in common use.

Materials of Pipe Fittings

Pipe fittings are made of various types of steel like Carbon Steel, Alloy Steel, Stainless Steel, Duplex/ Super Duplex, Nickel Alloy, etc.

Carbon Steel

Carbon steel is much more durable and stronger than other varieties of steel, which makes it suitable for making pipe fittings. Also known as plain carbon steel, carbon steel is a malleable and iron-based metal, made by combining iron with between 0.02%-1.7% and small amounts of manganese and other elements. Steel is subjected to various processes and can either be cast to shape or wrought into various mill forms from which finished parts are formed, forged, stamped, machined or otherwise shaped. Carbon is the main hardening and strengthening element present in steel, which offers maximum hardness and strength; and decreased ductility and weld-ability.

Based on carbon %, steel can further classify as:
• Low carbon steel: in which Carbon is in range from 0.05% to 0.25%
• Medium Carbon Steel: in which Carbon is in range from 0.25% to 0.5%
• High Carbon Steel it is in range from 0.5% to less than 2%

Application of Carbon steel

Fittings made of carbon steel are used in pipe systems that carry liquids or gases, such as oil, water, natural gas, or steam. Apart from that, carbon steel fittings are highly demanded in construction and maintenance activity in the residential construction, commercial construction, electric-power generation, petroleum refining, shipbuilding and other industrial-use sectors.

Galvanized Steel

In order to protect steel from rust and corrosion, steel is coated in layers of zinc through a chemical process. Galvanized steel offers resistance to rust and corrosion and is highly preferred for making pipe fittings and pipe. Galvanized steel also increase the longevity of pipe fittings.
Fittings made of galvanized steel are available in standard sizes ranging from 8mm to 150mm.

Application of Galvanized Steel

Galvanized steel pipe fittings are for all types of piping inside a building. They are also used in water supply lines, but not in gas pipelines.

Low-alloy Steels

Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.

For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.
As with steels in general, low-alloy steels can be classified according to:
• Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels;
• Heat treatment, such as quenched and tempered, normalized and tempered, annealed;

High-Strength Low-Alloy Steels

High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition.

The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce adequate formability and weld-ability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium and zirconium are used in various combinations.

Stainless steel

Stainless steel is widely used for making pipe fittings because of the fact that it is highly resistant to oxidation and corrosion in various natural and man-made environments. Stainless steel is actually a ferrous alloy containing minimum 10% chromium. Selection of right grade of stainless steel for a particular application is really important. A range of pipe fittings like tees, unions, elbows, etc are made of stainless steel. Stainless steel fittings are usually used for household pipelines.

Duplex Stainless Steel

Austenitic-Ferritic stainless steels, also called duplex stainless steels, were developed more than 70 years ago in Sweden for the paper industry in order to combat corrosion problems caused by chloride-bearing cooling waters and other aggressive chemical process fluids.
Due to the high content of chromium, nitrogen, and molybdenum, these steels offer good resistance to localized and uniform corrosion. The duplex microstructure contributes to the high mechanical strength, good abrasion, erosion and fatigue resistance. Duplex steels also possesses good weld-ability properties.
Typical applications of duplex stainless steel are:
• Pulp and paper industry
• Components for structural design
• Storage tanks
• Cargo tanks and pipe systems in chemical tankers
• Water heaters
• Flue-gas cleaning
• Heat exchangers

Super Duplex Stainless Steel

First used in the 1980s, Super- Duplex refers to highly alloyed, high performance Duplex stainless steel with an improved pitting and crevice corrosion resistance.
Super duplex steels were designed for specific applications where both high mechanical strength and good corrosion resistance are required. Super Duplex Stainless Steel is noted for its high level of chromium, which gives the alloy excellent resistance to acid chlorides, acids, caustic solutions and other harsh environments.
Typical applications of duplex stainless steel are:
• Desalination plants • Heat exchangers
• Pollution control
• Pulp and Paper industry
• Tube & Pipe systems for petrochemical refineries
• Downhole

Selection criteria for pipe fittings:
The pipe fittings “bodies” are most often of the same base material as the pipe or tube in which they are to be connected, e.g., steel, polyvinyl chloride (PVC), copper or other plastic or metal. Besides this, any material that is allowed by a code or a standard can also be used. For example, a pipe fitting made of brass is common in otherwise copper piping and plumbing systems. The materials of construction of pipe fittings must satisfy certain criteria like as follows:
• The material of construction must be compatible with the other materials in the system.
• It must be compatible with the fluids or solids being transported.
• It should withstand fluctuating temperatures inside and outside of the system.
• It should also be compatible with different pressure levels.
• Fire hazards, earthquakes, and other unforeseen factors also influence pipe fitting materials.
• Pipe fitting material specifications and construction are application-dependent.
• For optimization of component selection, user consultation with fitting suppliers is a must.
• The materials of construction should also conform to certain standards like BSP, NPT, ASME, ASTM, DIN, JIS etc.
• Surface finish is equally important. It is to be noted that all pipe fittings should have a proper finish as pipe fittings are constantly in harsh environments. Corrosion resistant property of the materials is an essential requirement.
ASTM International: American Society for Testing and Materials
This is one of the largest voluntary standards development organizations in the world. ASTM standards define the specific manufacturing process of the material and determine the exact chemical composition of pipe fittings, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by “Grade”. 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.
UNS: Unified Numbering System
The Unified Numbering System (UNS) for identifying various alloys is also quoted. This is not a specification, but in most cases, it can be cross-referenced to a specific ASTM specification.
Alloy numbering systems vary greatly from one alloy group to the next. To avoid confusion, the UNS for metals and alloys was developed.
The UNS number is not a specification, because it does not refer to the method of manufacturing in which the material is supplied. The UNS indicates the chemical composition of the material. An outline of the organization of UNS designations follows:

Some ASTM materials are compatible with specifications from other countries, such as BS (Britain), AFNOR (France), DIN (Germany), and JIS (Japan). If a specification from one of these other countries either meets or is superior to the ASTM specification, then it is considered a suitable alternative, if the project certifications are met.

Standards of Pipe Fittings

Process plants designed and constructed to the ASME B31.3 code also rely on the standardization of the components used for piping systems and the method of process plant fabrication and construction. There are numerous standards, many of which are interrelated, and they must be referred and adhered to by design engineers and manufacturers in the process industry. These standards cover the following:
• Material: chemical composition, mechanical requirements, heat treatment, etc.
• Dimensions: general dimensions and tolerances.
• Fabrication codes: welding, threading.
Standards covering the preceding were drawn up by the following major engineering bodies:
• American Petroleum Institute (API).
• American Society for Testing and Materials (ASTM).
• American Water Works Association (AWWA).
• American Welding Society (AWS).
• Manufacturers Standardization Society (MSS).
• National Association of Corrosion Engineers (NACE).
• Society of Automotive Engineers (SAE).
Periodically, these standards are updated to bring them in line with the latest industry practices. Most of the standards have been in circulation for a number of years, and the changes are rarely dramatic; however, such changes must be incorporated into the design. It is essential that the latest revision is the final reference point.
Other countries publish comprehensive standards containing data on material, dimensions of components, and construction procedures; however, for the purpose of this book, the standards mentioned previously are referenced.
American standards are not superior to other national standards, but they are the ones most commonly used in the process industry. They are based on a long track record with a very low failure rate, so there is a high degree of confidence in these publications. Always refer to the latest edition of the relevant standards, and if necessary, make sure your company’s library holds the most current version.

Material Standard for Pipes and Tubes

API

API Spec 5B: Specification for Threading, Gauging and Thread Inspection of Casing, Tubing and Line Pipe Threads;
API Spec 5L: Specification for Line Pipe;
ANSI/API Std 1104: Welding of Pipelines and Related Facilities;
ANSI/API RP 1110: Pressure Testing of Liquid Petroleum Pipelines.

ASME

B31.3, Process Piping: This code covers the design of chemical and petroleum plants and refineries processing chemicals and hydrocarbons, water, and steam. It contains rules for the piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. The code prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping. This code applies to piping for all fluids, including (1) raw, intermediate, and finished chemicals; (2) petroleum products; (3) gas, steam, air, and water; (4) fluidized solids; (5) refrigerants; and (6) cryogenic fluids. Also included is piping that interconnects pieces or stages within a packaged equipment assembly.
B36.10: This standard covers the standardization of dimensions of welded and seamless wrought steel pipe for high or low temperatures and pressures. The word pipe is used as distinguished from tube to apply to tubular products of dimensions commonly used for pipeline and piping systems. Pipe NPS 12 (DN 300) and smaller have outside diameters numerically larger than corresponding sizes. In contrast, the outside diameters of tubes are numerically identical to the size number for all sizes.
B36.19: This Standard covers the standardization of dimensions of welded and seamless wrought stainless steel pipe for high or low temperatures and pressures. The word pipe is used, as distinguished from tube, to apply to tubular products of dimensions commonly used for pipeline and piping systems. Pipes NPS 12 (DN 300) and smaller have outside diameters numerically larger than their corresponding sizes. In contrast, the outside diameters of tubes are numerically identical to the size number for all sizes. The wall thicknesses for NPS 14 through 22, inclusive (DN 350–550, inclusive), of Schedule 10S; NPS 12 (DN 300) of Schedule 40S; and NPS 10 and 12 (DN 250 and 300) of Schedule 80S are not the same as those of ASME B36.10M. The suffix “S” in the schedule number is used to differentiate B36.19M pipe from B36.10M pipe. ASME B36.10M includes other pipe thicknesses that are also commercially available with stainless steel material.

AWS

AMERICAN WELDING SOCIETY A3.0: Standard welding terms and definitions, including terms for adhesive bonding, brazing, soldering, thermal cutting, and thermal spraying.
A5.01-93R: Filler metal procurement guidelines.
A5-ALL: Filler metal specifications series plus filler metal procurement guide.

AWWA

AMERICAN WATER WORKS ASSOCIATION C200-97: Steel water pipe—6 in. (150 mm) and larger.

MSS

MANUFACTURERS STANDARDIZATION SOCIETY SP-69: Pipe hangers and supports—selection and application.

NACE

NATIONAL ASSOCIATION OF CORROSION ENGINEERS MR0175: Metals for sulfide stress cracking and stress corrosion cracking resistance in sour oilfield environments.
RP0170: Protection of austenitic stainless steels and other austenitic alloys from polythionic acid stress corrosion cracking during shutdown of refinery equipment.
RP0472: Methods and controls to prevent in-service environmental cracking of carbon steel weldments in corrosive petroleum refining environments.

SAE

SOCIETY OF AUTOMOTIVE ENGINEERS SAE J 518: Hydraulic flanged tube, pipe, and hose connections, four-bolt split flange type.

ASTM

American Society of Testing and Materials The American Society of Testing and Materials specifications cover materials for many industries, and they are not restricted to the process sector and associated industries. Therefore, many ASTM specifications are not relevant to this book and will never be referred to by the piping engineer.
We included a number of the most commonly used ASTM specifications in the Materials page of the products.
Some ASTM materials are compatible with specifications from other countries, such as BS (Britain), AFNOR (France), DIN (Germany), and JIS (Japan).

Manufacturing Process of Pipe Fittings

There are various Pipe Fittings Manufacturing Process that used to manufacture Elbow, Tee, Reducer and other pipe fittings.
Pipe Fittings are manufactured from bar, Seamless Pipe and from Welded Pipe with filler material (ERW & EFW pipes cannot be used to manufactured fittings). Large diameter fittings are manufactured from Plate.
Each product is manufactured with its own special process. The most appropriate manufacturing process for each product will be decided with consideration of its material, sizes, shape, use, standards and special properties.

Butt-Welding

To manufacture wrought fittings various methods are used, these are the some types of Hot forming and cold forming processes:
• Hot forming or Extrusion Method
• Hydraulic Bulge method – Cold forming
• UO or Single weld seam Method
• Monaka or Double weld seam Method
• Deep Drawing Method for caps
• Flare Method for stub ends

ELBOW
Mandrel Method(Hot Forming)
One of the most common manufacturing methods for manufacturing Elbows from pipes.
After heating the raw material, it is pushed over a die called “mandrel” which allows the pipe to expand and bend simultaneously. Applicable to a wide size range.
Characteristics of mandrel bending strongly depend on the integrated shape and dimensions of the mandrel.
Elbows manufactured by using hot mandrel bending have advantages of small thickness deviation and shorter bending radius than those of any other bending method type.

Extrusion method (Cold Forming)
In cold Extrusion method, a pipe with the same diameter as finished product is pushed through a die and formed into its desired shape.
It is usually applied to stainless steel small to medium sizes elbow.

“UO” Method (Welding)
In this method the plate is cut out into a specially designed shape, it is formed first into a U-shape using a die and then into an O-shape or tubular form using another die, that is why this method is known as UO method. Once the fittings formed in tumbler shaped it is welded from inside and outside of the closing seam. A cut plate is 1st from in U shape and then in O shape.

Hot Forming Die Bending method
In this method the pipe is been inspected before any process. Then after cutting out pipe into specified length, it goes under elliptical forming using a die shown in the picture. For producing a specified radius for elbow, it bends in another die. In the next step the elbow goes under heat treatment. In the end shot blasting, cleaning, beveling and coating are done respectively to finalize the product.

TEE
Hydraulic Bulge method (Cold Forming)
Cut piece of Pipe is placed in hydraulic die and liquid is fill inside the pipe, Hydraulic pressure pushes out the branch, in the fixed opening in the die.
This method gives the good surface finish. However, higher thickness Tee cannot be manufactured by this method.

“Monaka” method
This manufacturing method is similar to Elbows, using steel plates as the raw material.
In this method two pieces of raw material plates cut out symmetrically and are press-formed and welded together.

Hot Extrusion Method
Tee with large diameters, heavy wall thickness and/or special material with challenging workability that cannot be manufactured using the hydraulic bulge method are manufactured using hot Extrusion Method.
In hot Extrusion Method, Normally Bigger diameter pipe is used than the finished product size, the branch outlet is extruded from the pipe with help of extrusion tool.
Other dimensions of body and branch can also be adjusted by pressing the die if required.

REDUCER
Outer Die method
One of the most common method for manufacturing Reducers is using an outer die.
The pipe is cut and pressed in the outer die; compressing the one end of the pipe into a smaller size. This method is useful for manufacturing of small to medium size of reducers.

Plate Forming Method
Plates can also be used to manufacture Reducers.
In an UO method, plate is cut in a specially designed shape which is formed into a U-shape and an O-shape respectively, then finished with a single weld seam.

CAP
Deep Drawing method
CAPs are manufactured by Deep Drawing method. In this method, Plate is cut out in a circle and formed by deep drawing die.

STUB END
Flaring method
Stub Ends or Lap Joints Flange are manufactured by flaring method. Pipe end is a flare or spared out to form flange face. Stub ends are also manufactured by forging in which forge block are machined to final dimension.

FORGED FITTINGS

There are multiple options for Fittings deformation using the forging concept. The two most common processes are open and closed die forging. While similar in the basic idea of using pressure and temperature to modify material, the two types of forging are made distinct by their use of dies to form the metal.

Open Die Forging
Open die forging is the process of deforming a piece of metal between multiple dies that do not completely enclose the material. The metal is altered as the dies “hammer” or “stamp” the material through a series of movements until the desired shape is achieved. Products formed through open forging often need secondary machining and refining to achieve the tolerances required for the finished specifications. Open die forging is often used for short run forgings of parts that are simple, rather than complex, in design, such as discs, rings, sleeves, cylinders and shafts. Custom shapes can also be produced with open die forging. The repeated working of the material through the deformation process increases the strength of the grain structure. Some additional benefits of open die forging include improved fatigue resistance and strength.

Closed Die Forging
Closed die forging (also referred to as impression die forging) is a metal deformation process that uses pressure to compress a piece of metal to fill an enclosed die impression. In some closed die forging processes, a succession of impression dies are used to modify the shape of the material into the final desired shape and form. The type of material, tightness of tolerances, and need for heat treatment can determine the number of passes the product requires through the dies.

Inspection of pipe fittings

The project name	Specification and sampling
Chemical composition	Take 1 sample from each furnace
Tensile test (at room temperature/high temperature)	Take 1 sample from each batch on two pipe fittings
Weld stretching (for welded pipe)	Take 1 sample per batch
Hardness test	Take 1 sample from each batch on two pipe fittings
Impact test	Each batch takes 1 group of 3 samples on two pipe fittings
Flattening test	Take 1 sample from each batch on two pipe fittings
Flaring test	Take 1 sample from each batch on two pipe fittings
Bending test	Take 1 sample from each batch on two pipe fittings
Metallographic analysis (Intergranular corrosion/Grain size/Macroscopic examination)	Take 1 sample from each batch on two pipe fittings
Nondestructive testing (ultrasonic /Eddy current)	By the root
The quality of the coating	Take 1 sample from each batch on two pipe fittings
Dimensions, surface quality, roughness	Take 1 sample from each batch on two pipe fittings
Involved in standard
GB/T, ASTM, HG, ISO, JGJ

Installation of pipe fittings

The pipeline used in the production unit is generally longer than the standard length (i.e., the fixed-length pipe produced by the manufacturer according to the standard), especially the pipeline used in the petrochemical transmission system, which is often tens of kilometers or even hundreds of kilometers in length, so the pipeline connection has become a very important part of the pipeline design. A reasonable choice of connection method can not only save man-hours, but also ensure the smoothness of the process and increase safety.
The connection method of pipeline is roughly divided into: threaded connection, welding, flange connection, socket connection, socket bonding, ferrule connection, clamp connection, other connections, etc.
The choice of connection: should be based on the type of pipe, pipe diameter, wall thickness, medium, pressure, corrosion, design requirements, etc. Comprehensive consideration, in practice, generally subject to the project requirements of the project.

Threaded connection

Threaded connection, also known as a fillet connection (SCR’D), is a method of processing the pipe end into external threads, and the internal threads of the pipe fittings for a close connection, generally applicable to nominal diameter ≤ 50 mm (indoor open water piping can be ≤ 150 mm), working pressure less than 1.0 MPa, medium temperature ≤ 100 ℃ (373K) of welded steel pipe, galvanized welded Steel pipes or hard PVC plastic pipes are connected with pipes or valves and fittings with threads. When the threaded connection, between the threads often add filler such as hemp wire, asbestos wire, lead oil. Now generally use polytetrafluoroethylene (raw material tape) as filler, the sealing effect is better.

Welding

Welding is a non-detachable connection and is a common method used in production activities. As far as pressure piping is concerned, welding is the majority of connections used, and socket welding (SW) and butt welding (BW) are commonly used in engineering.
All pressure pipelines, such as steam, air, gas, vacuum and other pipelines try to use welding. Pipe diameter greater than 32mm, thickness of 4mm or more using electric welding; thickness of 3.5mm or less using gas welding.
In the construction site welding carbon steel pipeline, often using gas welding or manual electric arc welding. The weld strength of electric welding is higher than that of gas welding, and is more economical than gas welding, therefore, electric welding connection should be used as a priority.

1. Socket welding

Socket welding English translation: Socket Weld, usually in ≤ DN40 pipeline using socket welding, the pipeline inserted into the welding, so as to achieve the connection of pipe and tube, pipe fittings, valves, welding after the formation of the weld is a fillet weld.
The advantages of socket welding: there is no problem of beveling; there is no problem of misalignment; the socket has a certain complementary effect.
Disadvantages of socket welding.
The stress condition after welding is not good, easy to occur not weld through the phenomenon; to the cleanliness of the media requires high, the end part of the pipe due to sealing in the internal, easy to remain
Pipe system internal gaps, gaps corrosion-sensitive media pipeline system and high cleanliness requirements of the pipeline system is not suitable for socket welding, passivation treatment of stainless steel, pay particular attention to; for the pipeline with RT requirements, socket welding the formation of the fillet weld can not be achieved.

2. Butt welding

The two workpiece ends are placed opposite each other, using welding current to heat, and then pressurized to complete the welding resistance welding method. Including resistance butt welding and flash butt welding two.
Usually used in ≥ DN40 pipeline butt welding, widely used in petrochemical installations in flammable, combustible media, and other high temperature – pressure parameters of the media pipeline.
Advantages of butt welding.
Good welding performance and high structural strength.
High production efficiency, easy construction, low price and no leakage points.
The formation of a ring weld after welding, which facilitates nondestructive testing.
Disadvantages of butt welding.
the need to locate the axis of the two workpieces before welding.
certain requirements for the beveling of the pipe end, and the beveling form is more demanding for pipelines with larger thicknesses.
Wall thickness is different, the use of butt welding, according to the welding process procedures to select the appropriate bevel.

Flange connection

Flange Introduction: Flange (Flange) is also called flange or flange flange. Flange is to make the pipe and pipe and and valve interconnected parts, connected at the end of the pipe, but also useful in the import and export of equipment on the flange, for the connection between two devices. Flanges with holes, bolts to make the two flanges tightly connected, flanges with a gasket seal between. Flange is divided into threaded connection flange, welding flange and tube flange. Flange connection or flange joint is a detachable connection consisting of flange, gasket and bolt connected to each other as a group of combined sealing structure.
Features: Suitable for large pipe diameter, high sealing requirements of the pipe connection, such as vacuum pipe; also suitable for glass, plastic, valve parts and pipe or equipment connection. For the connection of cast iron pipes and lined pipes, flange connections are usually used. For flange connections of special piping, there is no standard flange fittings, and the size of the specifications are determined by the manufacturer.
Flange connection advantages and disadvantages.
High strength, good sealing performance; larger pipe diameter, higher pressure occasions are more suitable; equipment and pipelines can be used, so the application is more common; complex processing, higher costs.
Flange connection principle.
The gasket is placed between the two flange connection surfaces, and after tightening the nut, the specific pressure on the surface of the gasket reaches a certain value to produce deformation and fill the uneven out on the sealing surface, so that the connection is tight and does not leak.

Socket connection

It is applicable to the connection of buried or along the wall laid water supply and drainage pipes, such as cast iron pipes, ceramic pipes, asbestos cement pipes with pipes or fittings, valves. The use of asbestos cement, asphalt marsupial, cement mortar as a seal, working pressure ≤ 0.3MPa, medium temperature ≤ 60 ℃.
Socket connection is divided into two kinds of rigid socket connection and flexible socket connection.
The rigid socket connection is made by inserting the socket of the pipe into the socket of the pipe, and after alignment, it is first embedded with inlay material and then sealed with sealing material to make a solid and closed connection.
The flexible socket joint puts a flexible rubber ring on the stop seal of the pipe socket, and then applies force to insert the plug end of the pipe to form a closed pipe that can adapt to a certain range of displacement and vibration.
There are two kinds of seals in the socket: oil sisal and rubber ring. The main role of the seal ring is to block the interface filler into the tube and prevent the medium inside the tube from penetrating outside the tube.
Socket bonding.
Applicable to a variety of plastic pipes (such as ABS pipes, glass fiber reinforced plastic pipes, etc.) in the connection of the pipe or valve, pipe fittings. Use adhesive coating and insert the outer surface of the tube, and then insert the socket, after curing, that is, into one, convenient construction, good airtightness.

Ferrule connection

Suitable for the connection of metal pipe with metal pipe or with non-metal pipe fittings and valves of pipe diameter ≤ DN40, with a gasket in the middle, convenient construction and easy disassembly, generally used for instruments, control systems, etc.
Steel tube fitting: working principle, steel tube fitting is composed of ferrule, joint body and nut. The ferrule is a metal ring with a taper on the outside of the front and rear ends and an edge on the inside of the front section; the joint body is equivalent to an extrusion die; the role of the nut is to push the ferrule so that the front outside of the ferrule arches in the middle under the action of the taper inside the joint, and the front of the ferrule shrinks and deforms radially, causing the edge on the inside of the front of the ferrule to catch the tube. If you continue to tighten the nut, the ferrule in the process of deformation will force the edge to cut into the steel pipe to form a seal. And the outer side of the front and rear ends of the ferrule form a tapered seal with the joint body and the inner taper of the nut respectively.
Scope of use: Steel tube fittings have strong connection, good sealing and high pressure resistance, and can be used in steel pipes with nominal pressure of 16MPa and 32MPa, and the maximum nominal diameter is 32mm. steel tube fittings are easy to operate without fire during installation, and are widely used in the pipelines of self-control devices in chemical, light industry, machinery, national defense, aviation, medicine and other fields, as well as the hydraulic transmission pipelines of various engineering machinery and machine tools. It is widely used in the pipeline of automatic control devices in chemical, light industry, machinery, national defense, aviation, medicine and other fields, and the hydraulic transmission pipeline of various engineering machinery and machine tools. Steel tube fittings can be made of high quality carbon steel when used for conveying non-corrosive media; when used for conveying corrosive media, they can be made of acid-resistant steel according to the characteristics of the media.

Clamp connection

Groove fitting connection technology, also known as clamp connection technology, has become the current preference for liquid and gas pipeline connections. Although this technology was developed later in China than abroad, it was quickly accepted by the domestic market due to its advanced technology. Since 1998, it has been developed and applied in just a few years, and has gradually replaced the two traditional pipeline connection methods of flange and welding. Not only is the technology more mature, the market is also generally recognized, and has been actively guided by national regulations and policies. The application of groove pipe connection technology, so that the complex pipeline connection process becomes simple, fast and convenient. Make a big step forward in pipeline connection technology.
Groove connection fittings include two major products: ① the role of the connection seal fittings, rigid joints, flexible joints, mechanical tees and grooved flanges; ② the role of the connection transition fittings, elbows, tees, tees, reducers, blind plates, etc..
The groove connection pipe fittings that play a role in connecting and sealing have three main components: sealing rubber ring, clamps and locking bolts. The inner rubber seal ring is placed on the outside of the connected pipe and coincides with the pre-rolled groove, and then the clamp is fastened on the outside of the rubber ring, and then fastened with two bolts. Due to the unique sealable structure design of the rubber seal and clamp, the groove connection has good sealing, and the sealing is enhanced with the increase of fluid pressure in the pipe.
Advantages of the clamp connection: The connection operation of groove fittings is very easy and requires no special professional skills, and can be operated by ordinary workers with simple training. This is because the product has a large number of fine technical parts that have been factory-developed into the finished product. A pipe connection takes only a few minutes, which simplifies the technical difficulty of the field operation to the maximum extent and saves man-hours, thus also stabilizing the quality of the project and improving the efficiency. This is also the general direction of the development of installation technology. In addition, because the trench fittings are finished parts, the operation space required at the site is small, and can be truly installed against the wall and corner, the operational difficulties are greatly reduced, thus saving floor space and beautifying the effect of pipe installation.
The original characteristics of the pipe will not be destroyed, only the outer surface of the connected pipe extruded with a groove roller, without destroying the internal structure of the pipe, which is the unique technical advantage of the groove pipe connection.
Scope of use: As an advanced pipeline connection method, groove pipe connection can be open or buried, i.e., there are steel joints and flexible joints. Therefore, it has a wide range of application.

Application of pipe fittings

• 1. Stainless steel pipe fittings can be used in vehicle / Automobile Industry: the body structure made of high-strength stainless steel can greatly reduce the dead weight of the vehicle and enhance the strength of the body structure. Using stainless steel as the panel and decorative parts of the vehicle can reduce the maintenance cost.
• 2. Stainless steel pipe fittings are used in industry. It is convenient to quickly Su connect stainless steel pipe fittings at the construction site for people to use.
• 3. Stainless steel pipe fittings are used in construction. It is one of the earliest fields of stainless steel application. In terms of architectural decoration, at present, stainless steel is mainly used in the coating of exterior walls, indoor and outdoor columns of high-rise buildings, handrails, floors, elevator wallboards, doors and windows, curtain walls and other internal and external decoration and components. The stainless steel plate with surface treatment, coloring and coating solves the problems of fingerprints after touching, and further expands the application range of stainless steel.
• 4. Stainless steel pipe fittings are used in home appliance industry: in the home appliance industry, the largest amount of stainless steel is the inner cylinder of automatic washing machine, the inner tank of water heater, the inner and outer shell of microwave oven, the lining of refrigerator, and ferritic stainless steel is mostly used.
• 5. Stainless steel pipe fittings are used in water industry: people pay more and more attention to the pollution of water in the process of storage and transportation. A large number of facts have proved that stainless steel is the most Jia material for water industry such as water storage, storage, transportation, purification, regeneration and seawater desalination. Its advantages are: corrosion resistance, earthquake resistance, water saving, sanitation (no rust and copper green), light weight (reduced by 1 / 3), less maintenance, long service life (can be used for 40 years), low life cycle cost, and it is a recyclable green environmental protection material.

The application fields of stainless steel pipe fittings are mainly household appliances, household appliances, petroleum, chemical industry, smelting, electric power, water conservancy, water supply, heating, gas supply, natural gas, ships and large-scale infrastructure.

How to choose the right pipe fitting solution

Selection of flange 

Concerned about the selection of the highest non-impact working pressure of the flange 

In the steel pipe flange pressure a temperature level HG20604-97 standard specifies the highest non-impact working pressure of the pipe flange (European system) in the working temperature. And requires the highest impact-free working pressure of the flange selected in the working temperature must be greater than or equal to the design pressure. For example, the design temperature of the nitrogen and hydrogen gas pipeline of the compression section 150E, the design pressure 6.0MPa, the need to choose the appropriate grade and material flange. HG 20604-97 standard flange nominal pressure 6.3MPa, working temperature 150C, flange material 20, the highest impact-free working pressure is only 4.85MPa; and flange material 16Mn II, the highest impact-free working pressure of 6.17MPa. Therefore, the flange is selected with nominal pressure of 6.3MPa and flange material of 16Mn II. 

Concerned about the equipment orifice flange sealing surface form 

In the form of equipment orifice flange sealing surface for the study of the general form are concave and convex surface of the orifice flange, in this case most of the time is set to the concave and convex flange in the top and side pipe mouth. The bottom orifice flange is set to convex flange. And valve manufacturers generally make valves with their own concave flanges. When the process piping requirements of the equipment orifice and pipeline valves directly connected, it is necessary to give the equipment professional to mention the requirements of the form of sealing surface of the orifice to match the valve flange connection. 

Selection of valves

More butterfly valves, less gate valves 

In the previous period of time, butterfly valves are generally only used in large-diameter water pipes, in the process of continuous development, the market for butterfly valve manufacturing process and technology has also made considerable progress and development, due to its superior performance, in some industrially developed countries have been used in large numbers to replace the traditional gate valve, globe valve, ball valve and plug, this is because the butterfly valve has the following characteristics. 

• (1) small size, light weight, easy construction, its weight is only 1/3 to 1/4 of the same level gate valve, the height and width is only 1/3 of the same level gate valve;
• (2) cut-off performance than the gate valve, globe valve;
• (3) simple structure, easy maintenance;
• (4) easy to configure automatic control mechanism;
• (5) and the same level (referring to temperature, pressure, quality indicators) of the gate valve, globe valve comparison, butterfly valve The price is relatively low. In the flue gas desulfurization production device as large as DN900 circulating slurry valve as small as DN25 other slurry shut-off valve almost all used are butterfly valves.

Plunger valve

Steam, oil and sealing requirements of high occasions appropriate to use plunger valve. We are accustomed to use the globe valve in sealing and service life are not as good as the plunger valve, the reason is that the plunger valve has the following characteristics. 

• (1) in considering the sealing, mainly the use of metal, non-metallic combination of practices, the point of doing so is to seal the smaller specific pressure, easy to achieve sealing requirements.
• (2) plunger valve in general are relying on the plunger valve and the upper sealing ring to maintain the seal, he generally does not have a stuffing box.
• (3) If there are small, hard solid particles attached to the sealing surface in the pipeline, it will cause local damage to the sealing surface of the valve seat, the plunger of the plunger valve moves just enough to push away the debris attached to the sealing surface, so it will not cause local damage to the sealing surface to ensure sealing performance.
• (4) sealing ring with non-metallic materials, will not rust, the valve is slightly open when the end face of the plunger and sealing ring is scoured, the sealing surface is not scoured, so the service life is longer than the globe valve;
• (5) easy maintenance, except when necessary to replace the sealing ring, unlike the globe valve requires grinding of the valve flap, valve seat. The United States and other industrially developed countries have long been commonly used.

Selection of tees

In people’s habits, often accustomed to the bottom of the main pipe from the other sub-pipe, the advantage of such a practice is that when the process of water with a tee, will not be restricted by the up and down, more convenient, and for the transport of gas in the horizontal direction of the pipeline sub and when the tee should face up, to avoid condensate blocking the pipeline. In particular, it is best to connect the steam pipe from above. Vacuum pipe merge tube, should be merged in the same direction. 

Selection of elbows

Some designers often say “piping does not matter, if not connected, add a few more elbows on the”, the error of this approach is that: the drawings only add an elbow, but for the production of increased resistance and may cause leakage, for the construction of two more welds, for investors and an increase in expenditure, so a reasonable design approach is to use as few elbows as possible, in order to make the pipeline layout warp and weft, to avoid disorder. 
When the process pipeline and not commonly used utility pipelines are connected, it is appropriate to use the two ends with flanges back to the elbow instead of the traditional valve. This can avoid misoperation. If the traditional design, that is, the process pipeline and regeneration pipeline connected together, when the normal operation of only part of the pipeline is working, it is often a hot end cold (room temperature), the stress problem is not easy to deal with, the use of back to the elbow can avoid such problems; sewage pipe need to change the direction of the 45-degree elbow should be used to facilitate the exhaustion of materials, reduce the material precipitation. 

Selection of reducers

In daily circumstances, the reducer is mainly divided into two kinds, one is eccentric reducer, the other is concentric reducer. In general, no special requirements in the horizontal pipeline is generally connected to the eccentric reducer, in the vertical direction is generally connected to the concentric reducer. For horizontal suction centrifugal pump, when the inlet pipe reducer, eccentric reducer should be set near the entrance of the pump. When the pipe from the bottom up into the pump, should use the top flat installation, when the pipe from the top down into the pump, should use the bottom flat installation. The principle of use is to be able to drain the condensate and prevent air resistance.

Source: China Pipe Fittings Solutions Supplier – Yaang Pipe Industry (www.epowermetals.com)

(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.)

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