What are pipe fittings

What are pipe fittings?

Pipe fittings are general terms for components in the piping systems that function as connection, control, direction change, split, seal, and support.

According to different processing methods, it is divided into four categories, namely butt welding pipe fittings (both weld and no weld), socket welding and threaded pipe fittings, flanged pipe fittings. 
Common classification of

There are many types of pipe fittings, which are classified according to the use, connection, materials, and processing methods.

By purpose	By connection
Socket weld pipe fittings	Buttweld pipe fittings
Threaded pipe fittings	Outlet pipe fittings
By material	Standards of pipe fittings
Applications and markets of pipe fittings	How to get high quality pipe fittings

By purpose

• Pipe fittings for connecting pipes are: flange, union, expansion joint, coupling, ferrule, hose clamp, swage nipple, etc.
• Change the pipe direction of the pipe: elbow, bend, pipe tee, pipe cross, adapters, olet (weldolet, sockolet, elbowlet, thredolet, nipolet, letrolet, swepolet)
• Pipe fittings that change the pipe diameter: reducer, branch pipe
• Pipe fittings for pipeline sealing: gasket, pipe plug, blind flange, head, cap
• Pipe fittings for pipe fixing: snap ring , tow hook, lifting ring, bracket, bracket, pipe card, etc.

By connection

• Buttweld pipe fittings
• Threaded pipe fittings
• Socket weld pipe fittings
• Outlet Pipe Fittings

Socket weld pipe fittings

A Socket Weld is a pipe attachment detail in which a pipe is inserted into a recessed area of a Valve, fitting or flange. In contrast to buttweld pipe fittings, Socket Weld fittings are mainly used for small pipe diameters (Small Bore Piping); generally for piping whose nominal diameter is NPS 2 or smaller.

To join pipe to Valves and fittings or to other sections of pipe, fillet-type seal welds be used. Socket Welded Joints construction is a good choice wherever the benefits of high leakage integrity and great structural strength are important design considerations.

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.

Some details of socket weld pipe fittings

SW Fittings are family of high pressure fittings are used in various industrial processes.

• They are used for lines conveying flammable, toxic or expensive material where no leakage can be permitted, and for steam 300 to 600 PSI.
• They are used only in conjunction with ASME Pipe and are available in the same size range.
• They are used in areas where pipe-work is permanent and are designed to provide good flow characteristics.
• They are are produced to several ASTM standards and are manufactured in accordance with ASME B16.11. The B16.11 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 requirements, melting practices, and mechanical property requirements of ASTM A105, A182, or A350.
• They are available in three pressure ratings: Class 3000, 6000 and 9000.

Advantages and disadvantages of socket weld fittings

Advantages

• The pipe need not be beveled for weld preparation.
• Temporary tack welding is no needed for alignment, because in principle the fitting ensures proper alignment.
• The weld metal can not penetrate into the bore of the pipe.
• They can be used in place of threaded fittings, so the risk of leakage is much smaller.
• Radiography is not practical on the fillet weld; therefore correct fitting and welding is crucial. The fillet weld may be inspected by surface examination, magnetic particle (MP), or liquid penetrant (PT) examination methods.
• Construction costs are 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.

Disadvantages

The welder should ensure for a expansion gap of 1/16 inch (1.6 mm) between de pipe and the shoulder of the socket.
ASME B31.1 para. 127.3 Preparation for Welding (E) Socket Weld Assembly says:

• In assembly of the joint before welding, the pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16″ (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket.
• The expansion gap and internal crevices left in socket welded systems promotes corrosion and make them less suitable for corrosive or radioactive applications where solids buildup at the joints may cause operating or maintenance problems. Generally require butt welds in all pipe sizes with complete weld penetration to the inside of the piping.
• Socket welding are unacceptable for UltraHigh Hydrostatic Pressure (UHP) in Food Industry application since they do not permit full penetration and leave overlaps and crevices that are very difficult to clean, creating virtual leaks.

The purpose for the bottoming clearance in a Socket Weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal, and to allow for differential expansion of the mating elements.

Buttweld pipe fittings

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.

Fittings are divided into three groups:

• Buttweld (BW) pipe fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43.
• Socket Weld (SW) pipe fittings Class 3000, 6000, 9000 are defined in the ASME B16.11 standards.
• Threaded (THD), screwed fittings Class 2000, 3000, 6000 are defined in the ASME B16.11 standards.

Applications of buttweld pipe fittings

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

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

Bevelled ends

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

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

Material and performance

• The most common materials used in fittings produced is carbon steel, stainless steel, cast iron, aluminium, copper, glass, rubber, the various types of plastics, etc..
• In addition, fittings, like pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the fitting themselves, which are “lined fittings”.
• The material of a fitting is basically set during the choice of the pipe, in most cases, a fitting is of the same material as the pipe.

What is a seamless buttweld pipe fitting?

• A seamless butt weld pipe fitting is made directly from a section of seamless pipe material, by applying heat and pressure to transform pipe directly into an elbow or other shape.
• A seamless fitting has no welded parts by itself, a characteristic demanded in some critical applications.
• By comparison, a regular butt weld fitting has one, two or more welds, depending on dimension, shape and manufacturing method.
• No weld means less risk of weld yield and porosities.

Threaded pipe fittings

Threaded joints probably represent the oldest method of joining piping systems. Like Socket Weld fittings, threaded fittings are mainly used for small pipe diameters (Small Bore Piping); generally for piping whose nominal diameter is NPS 2 or smaller.
The dimensional standards for taper pipe threads are given in ASME B1.20.1. That document gives all required dimensions including number of threads per inch, pitch diameter, and normal engagement lengths for all pipe diameters.

• Threaded piping is commonly used in low-cost, noncritical applications such as domestic water, fire protection, and industrial cooling water systems.
• Threaded fittings are normally made of cast gray or malleable iron, cast brass or bronze, or forged alloy and carbon steel.
• They are available in three pressure ratings: Class 2000, 3000 and 6000.

Npt thread

All fittings on this page are described, are provided with NPT thread, ASME B1.20.1. The American National Pipe Thread Tapered, is the best known and most widely used connection where the pipe thread provides both the mechanical joint and the hydraulic seal.

Advantages and disadvantages of threaded pipe fittings

Advantages

• Installation productivity is moderately high, and specialized installation skill requirements are not extensive.
• Leakage integrity is good for low-pressure, low-temperature installations where vibration is not encountered.

Disadvantages

• Rapid temperature changes may lead to leaks due to differential thermal expansion between the pipe and fittings.
• Vibration can result in fatigue failures of screwed pipe joints due to the high stress intensification effects caused by the sharp notches at the base of the threads.
• In hazardous piping systems threaded connections should be avoided, if possible. Their vulnerability to fatigue damage is significant, especially where exposed threads are subject to corrosion.

Outlet Pipe Fittings

Olet pipe fittings (otherwise called Branch Connection Fittings or Outlet fittings) will be fittings which give an outlet from a bigger pipe to a smaller one (or one of a similar size). The fundamental pipe onto which the branch association is welded is generally called the Run or Header size estimate. The pipe to which the branch association or connection gives a channel is normally called the Branch or Outlet size. Branch associations are in all sizes, sorts, bores, and classes, in an extensive variety of stainless steel, chrome-moly, and different amalgams alloys.

Different types of Olet or Outlet Pipe Fittings:

1) Brazolet (Brazo Outlet)

Brazolet is utilized generally abroad as of late, it is utilized to interface or connect the fortified fittings. It happens of conventional associating ways. The assortment of Brazolet is made in phenomenal Forgings. It’s intended for use with KLM and IPS metal or copper tubing. It’s accessible with socket or threaded connections.

Brazolet for IPS Pipe
ASME SB-98 UNS C665500 Alloy A
Outlet Sizes	A	B	C	Brazing Surface	F-MIN. MIL-1183
1/4	11/16	1	9/16	0.188	0.700
3/8	13/16	1 1/4	3/4	0.190	0.855
1/2	1	1 7/16	7/8	0.220	1.020
3/4	1 1/16	1 3/4	1 1/8	0.240	1.250
1	1 1/4	2 1/8	1 7/16	0.270	1.535
1 1/4	1 5/16	2 9/16	1 3/4	0.300	1.900
1 1/2	1 3/8	2 7/8	2	0.330	2.160
2	1 1/2	3 1/2	2 9/16	0.360	2.675
2 1/2	1 13/16	4 1/8	3	0.384	3.215
3	2	4 13/16	3 11/16	0.442	3.880
4	2 1/4	6	4 3/4	0.476	4.940
5	2 5/8	7 1/16	5 9/16	0.656	6.163
Brazolet for Tubing
Type K, L, and M Tubing. ASME SB-98 UNS C65500 Alloy A
Outlet Sizes	A	B	C	Brazing Surface	F-MIN. MIL-1183
1/4	11/16	1	9/16	0.188	0.700
3/8	13/16	1 1/4	3/4	0.190	0.855
1/2	13/16	1 1/4	3/4	0.190	0.855
3/4	1	1 7/16	7/8	0.220	1.020
1	1 1/16	1 3/4	1 1/8	0.240	1.250
1 1/4	1 1/4	2 1/8	1 7/16	0.270	1.535
1 1/2	1 5/16	2 9/16	1 3/4	0.300	1.900
2	1 3/8	2 7/8	2	0.330	2.160
2 1/2	1 1/2	3 1/2	2 9/16	0.360	2.675
3	1 13/16	4 1/8	3	0.384	3.215
4	2 1/8	5 1/2	4 5/16	0.437	4.400

2) Coupolet (Coupling Outlet)

Coupolet pipe fittings are intended for use in flame/fire insurance sprinkler frameworks and other low weight pressure piping applications. Produced with NPT female threads for 300# administration and are UL Listed and F.M. affirmed. 

300# Female Threaded Coupolet
Nominal Outlet Size	Dimensions
	A	C	F
1/2	15/16	0.745	1.188
3/4	1	0.958	1.441
1	1 3/16	1.188	1.562
1 1/4	1 5/16	1.550	1.906
1 1/2	1 9/16	1.780	2.188
2	1 11/16	2.260	2.750
2 1/2	1 13/16	2.890	3.386
3	2 1/2	3.400	4.000
4	3	4.380	5.000

Interchangeability or Combination of Sizes
Coupolet Outlet Size Inches	Run Sizes
1/2	1/2	3/4	1-1/4 -1	2-1/2 – 1-1/2	8-3	36-10
3/4	3/4	1	2 – 1-1/4	6 – 2-1/2	36-8
1	1	1-1/4	2 – 1-1/2	4 – 2-1/2	8-5	36-10
1-1/4	1-1/4	1-1/2	2-1/2 – 2	4-3	8-5	36-10
1-1/2	1-1/2	2	2-1/2	4-3	8-5	16-10	36-18
2	2	2 1/2	3	3-1/2	4	5	6	8	10	16-12	36-18
2-1/2	2-1/2	3	3-1/2	4	5	6	8	12-10	16-14	36-18
3	3	3-1/2	4	5	6	8	10	12	14	18-16	36-20
4	5	6	8	10	14-12	16	18	20	24	36

3) Elbolet (Elbow Outlet)

Elbolet is used on 90° Long Radius Elbows (can be manufactured for Short Radius Elbows) for thermowell and instrumentation connections. Available butt-weld to meet specific reinforcement requirements, and 3000# and 6000# classes for Socket Weld and threaded applications.
An Elbolet is used on 90° long radius elbows, short radius elbows and can be used on 180° returns. However, an Elbolet on a short radius elbow is not used often. It typically is used for Thermowell and instrumentation connections but can be used as a drain connection when room isn’t available for using a Weldolet. The Elbolet is available with buttweld, socketweld or threaded connections.
Outlet is used widely abroad in recent years, It is used to connect the reinforced fittings. It can replace the reducing tee, reinforce plate and reinforced pipe. It is used widely more and more in high pressure high temperature large diameter and thick wall pipe. As it is reliability, cheap, simple, good for flow, seriation, standardization and choose easily. It takes place of traditional connecting ways. The body of outlets is made in excellent Forgings. The material is same as pipe’s. We can make outlet from Carbon steel, Alloy steel and Stainless steel. branch or other fittings such as nipple thread plug, Instrument and valve by Butt Welding, Socket Welding and Threaded.

Nominal Elbow Size Inches	Outlet Size Inches	Dimensions
		CL 3000 Threaded & Socket Weld Std. & XS Butt-Weld		CL 6000 Threaded & Socket Socket-Weld Sch. 160 & XXS Butt-Weld
		C	E	C	E
36 – 3/4	1/4	1 1/2	1 19/32	1 1/2	1 19/32
36 – 3/4	3/8	1 1/2	1 19/32	1 1/2	1 19/32
36 – 3/4	1/2	1 1/2	1 19/32	1 23/32	1 7/8
36 – 1	3/4	1 23/32	1 7/8	2 1/4	2 1/4
36 – 2	1	2 1/4	2 1/4	2 7/8	2 1/2
36 – 2	1 1/4	2 7/8	2 1/2	3 1/8	2 11/16
36 – 2	1 1/2	3 1/8	2 11/16	4 3/16	3 1/4
36 – 3	2	4 3/16	3 1/4
	**2 1/2	4 3/16	3 1/4
	**3	5 1/16	3 7/8
Order to Specific	**4	6 5/8	4 13/16
Elbow Sizes	**6	9 3/8	6 1/2	**	**
	**8	13 5/16	8 1/16
	**10	17 1/32	10 3/8
	**12	19 5/8	11 1/8

4) Flexolet (Flexo Outlet)

Flexolets are like weldolets with a minor distinction i.e. flexolet has straight bore while weldolet has decreased bore. We give flexolets butt weld, socket weld and threaded ends. Hence, you can pick any of them as per the piping applications.

What is the difference between weldolet and flexolet?

All Weldolets are Flexolets but not all Flexolets are Weldolets in the same way that all dogs are animals but not all animals are dogs.

The Flexolet and the Weldolet products are our two branch connection designs. They perform the same function, which is that they reinforce the strength lost when a hole is cut into the header pipe and they connect the header pipe to the branch pipe. The difference in designs is that the Weldolet has a tapered bore while the Flexolet has a straight-through bore. 

See below:

The tapered bore provides a better transition (reduces the flow resistance) and it also provides a lower stress intensification factor, which results in less stress on the welds and longer fatigue life. The straight-through bore decreases the diameter of the part and allows for larger run-size consolidations (meaning you can use them on a wider range of header pipe diameters). Because of the smaller size of the straight-through bore, the Flexolet tends to be less expensive as compared to the Weldolet.

5) Insert Weldolet (Insert Welding Outlet)

Insert Weldolet is the most widely recognized of all branch connections, and is welded onto the outlet pipe. The ends are slanted to encourage this procedure, and in this manner the weldolet is viewed as a butt-weld fitting. Weldolets are intended to limit stretch fixations and give essential fortification / reinforcement.

Outlet Size	A’ Dimensions (Height  above run pipe)
	1 1/2	2	2 1/2	3	4	5	6	8	10	12	14	16	18	20	24
Std Wt Run Pipe	1.50	1.50	1.62	1.75	2.00	2.25	2.38	2.75	3.06	3.38	3.50	3.75	3.81	4	4.56
XS Run Pipe	1.50	1.50	1.62	1.75	2.00	2.25	3.06	3.87	3.69	4.06	3.81	4.19	4.38	4.69	5.50
.500″ to .750″ Thick Run Pipe	–	–	–	2.88	3.31	3.75	4.12	4.18	4.25	4.37	4.50	4.69	5.13	5.62	6.50
.750″ to 1.00″ Thick Run Pipe	–	–	–	3.22	3.38	3.75	4.34	4.62	4.84	5.10	5.25	5.88	6.50	6.75	7.62
1.00″ to 1.25″ Thick Run Pipe	–	–	–	3.38	3.50	4.00	4.50	4.88	5.00	5.38	5.50	6.00	6.50	7.00	8.00
1.25″ to 1.50″ Thick Run Pipe	–	–	–	3.62	3.87	4.25	4.69	5.16	5.31	5.68	5.81	6.44	6.50	7.56	8.72
Outlet Size	*’W’ Dimensions (Max. O.D. of fitting  – Max. size of hole)
	1 1/2	2	2 1/2	3	4	5	6	8	10	12	14	16	18	20	24
Std Wt Run Pipe	3.50	4.25	4.88	5.69	7.00	8.06	9.71	11.71	14.00	16.32	17.56	19.75	22.00	24.00	29.00
XS Run Pipe	3.56	4.38	5.00	5.75	7.12	8.25	10.44	13.44	14.25	16.56	18.00	20.00	22.44	25.00	30.32

6) Latrolet (Lateral Outlet)

Latrolets are a variety of weldolets. You have to connect it in same way, however these Latrolets make a 45-degree connection to the principle pipe instead of a 90 degree. These olets can be either butt welded, socket welded, or threaded.

7) Nipolet (Nipple Outlet)

Nipolets is only a blend of olets with nipples. These olets work like the weldolets or threadolets, yet are with nipple. They come either with a plain end or a threaded end. You can utilize either as indicated by the applications. Nipolets are broadly utilized for vents, taps, or depletes (drains).

Plain end and Threaded
Size		1/2	3/4	1	1 1/4	1 1/2	2
XS	A	3 1/2	3 1/2	3 1/2	3 1/2	3 1/2	3 1/2
	C	15/16	1 3/16	1 7/16	1 3/4	2	2 9/16
XXS	A	3 1/2	3 1/2	3 1/2	3 1/2	3 1/2	3 1/2
	C	9/16	3/4	1	1 5/16	1 1/2	1 11/16

8) Sockolet (Socket Weld Outlet)

A Sockolet is the same basic design as a “weldolet” or “threadolet” where the major difference is that a Sockolet has a socket for welding versus a buttweld connection that a Weldolet has. This makes a 90° branch and comes in full size or reducing for a straight piece of pipe. Sockolets are available in Class 3000, 6000 and 9000 for high pressures.

What is the difference between a weldolet and a sockolet?

The weldolet and the sockolet both have a run end and a branch end. The run end connects to the larger diameter pipe, and the branch end connects to the smaller diameter pipe. The connection to the run pipe is a fillet weld for both the weldolet and the sockolet. They differ, however, at the connection to the branch pipe. The weldolet has a bevelled end to butt weld to the branch pipe (which will also have a bevelled end), whereas the sockolet has a socket into which a plain end branch pipe is inserted, then fillet welded together.

Dimensions Reducing Sockolets – MSS SP97

9) Sweepolet (Swept Outlet)

Sweepolet is a shaped, essentially fortified; butt-weld branch association with a low stress escalation factor for low burdens and long exhaustion life. The connection weld is effectively inspected by radiography, ultrasound and other standard non-damaging methods. It’s produced to meet your particular support prerequisites. It reduces the stress concentration factors and pipe stresses.

Run Size	Outlet Size Inches	Dimensions
		*A	B
6 to 36	1 1/4	1 1/4	4
6 to 36	1 1/2	1 3/4	5 1/2
6 to 36	2	1 1/2	5 1/2
6 to 36	3	1 21/32	7
6 to 36	4	2 1/32	8 3/4
10 to 36	6	2 11/16	13
12 to 36	8	3	15
16 to 36	10	3 1/8	18 1/2
16 to 36	12	3 5/16	20 1/2
20 to 36	14	3 5/8	24
24 to 36	16	3 3/4	28
24 to 36	18	4 5/8	31
24 to 36	20	5 1/8	33
30 to 36	24	5 5/8	38

Weldolet Vs Sweepolet

Weldolets (aka WOL) are cheaper in terms of purchasing cost than sweepolets (aka SOL).

WOLs may, in some situations (large dia, thin wall) warp the pipe, i.e. unstraight and oval, due to excessive heat input arising form the relative thick required weld metal layer.

Since for WOLs the weld metal thickness is always greater than for SOLs (where one only welds the base metal wall thickness), welding may require some extra time to allow cooling off on the heat input to prevent banana-warping the pipe.

SOLs are less standard, I think most of the time custom made. Without having specific experience with SOLs, preparing and beveling the pipe for it may be more difficult/time-costuming compared to WOLs. For WOLs, you can weld them on, and then bore through the hole. This gives a smooth weld profile on the inside. This may give the best option for a flushing branch, as there is not weld metal ‘sticking into the run’ (provided the pipe doesnt become oval, as this will cause the pig trap to become stuck perhaps).

Since the saddle form is quite specific (but then again, the SOL may be laid down on the pipe, and the contour can be drawn), and a lot bigger than WOLs, more material has to be removed. 

If you use a SOL and the run pipe is large enough in dia, you may counter grind the root weld to become flush.

WOLs can be RT-ed, SOLs can.

WOLs are likely to give more peak stress than SOLs, since the latter has a much more continuous profile into the branch.

10) Threadolet (Threaded Outlet)

A threadolet is the same basic design as a “weldolet.” However the main difference is the fitting has a female threaded connection to mate to the branch connection. This makes a 90° branch and comes in full size or reducing for a straight piece of pipe. It typically is in the size range of 1/2″ to 2″ and is welded over a hole either drilled or burned in the pipe. 

You use a “weldolet” when you want to weld a pipe or fitting directly to the branch fitting and a “threadolet” when you want to screw the connecting pipe or fitting (e.g. valve) to the branch connection.

I believe there is a ANSI standard for the dimensions and pressure rating of these type of fitting. 

Depending of the relative size of the olet and the main pipe run the affect can vary from no affect to causing the header to bow or warp due to the heating and cooling of the weld. A good run of thumb is to never use an olet that is larger that 1/2 the size of the main pipe run. Size in this case being the nominal size.

Dimensions Reducing Thredolet – MSS SP97

11) Weldolet (Welding Outlets)

Weldolet (Welding Outlet) is the most common of all branch connections, and is welded onto the outlet pipe. The ends are bevelled to facilitate this process, and therefore the weldolet is considered a butt-weld fitting. Weldolet (Welding Outlet) is designed to minimize stress concentrations and provide integral reinforcement. manufactured to meet your specific reinforcement requirements.

What is a weldolet (Welding Outlet)?

A Weldolet is commonly known on drawings as a WOL and makes a 90° branch connection. It comes in full size or reducing for a straight piece of pipe. A weldolet is designated by the run length by the branch length. For example a 6-inch weldolet on a 19-inch pipe would be a 19×6 Weldolet. 

Outlet Pipe Fittings Classes as per this standadrd are : 

1. Standard : Buttwelding : 1/8″ to 24″, for connecting STD thk Pipe.
2. Extra Strong : Buttwelding : 1/8″ to 24″ for connecting Extra Strong Pipe
3. Schedule 160 : Buttwelding : 1/2″ to 6″ : for connecting Schedule 160 Pipe
4. 3000 : Threaded and Socket Welding : 1/8″ to 4″ : for connecting Extra Strong Pipe
5. 6000 : Threaded and Socket Welding : 1/2″ to 2″ : for connecting Sch 160 Pipe.

Material

• Carbon steel
• Stainless steel
• Other

Specifying the Schedule of both the Run and Branch

Generally the schedules of the run pipe and branch pipe are identical and thus specification of the equivalent schedule Weldolet assures the proper fitting being used.

EXAMPLE:
16″ Standard weight x 6″ Standard weight is specified as a 6″ standard weight fitting.
Where the schedule of the run is greater or less than the schedule of the branch, it is essential that both schedules be specified since (a) The Weldolet’s reinforcing characteristics are a function of the run pipe wall thickness, which in turn designates the schedule of the basic Weldolet fitting to be used;(b) The wall thickness of the outlet or branch end must match the wall thickness of the branch pipe.

EXAMPLE:
16″ Extra strong x 6″ Standard weight
16″ Standard weight x 6″ Extra strong
Special care is suggested to avoid confusing schedule 40 and standard weight as being identical (above 10″ schedule 40 is heavier) and schedule 80 and extra strong (above 8″ schedule 80 is heavier).

By material

Special Alloys

• Hastelloy® X
• Monel® R-405
• Monel® K-500
• Hastelloy® C-276
• Hastelloy® C-22
• Hastelloy® B-2
• Incoloy® 825
• Incoloy® 800h / 800ht®
• Inconel® 718
• Inconel® Alloy 625
• Inconel® Alloy 601
• Inconel® Alloy 600
• Monel® Alloy 400
• Alloy 20
• Nickel 200/201
• Monel® R-405
• Monel® K-500
• Monel® Alloy 400
• Inconel® 718
• Inconel® Alloy 625
• Inconel® Alloy 601
• Inconel® Alloy 600
• Incoloy® 825
• Hastelloy® X
• Hastelloy® C-276
• Hastelloy® C-22
• Hastelloy® B-2
• Incoloy® 800h / 800ht®
• Hastelloy® B-3

Duplex Stainless Steel

• Zeron® 100, Super Duplex Stainless Steel
• Super Duplex S32760
• Ldx 2101®, Duplex Steel
• Duplex S31803
• Super Duplex 2507
• Duplex 2205

Stainless Steel

• Stainless Steel Nitronic 50hs
• Stainless Steel Nitronic 60
• Stainless Steel Nitronic 50
• Stainless Steel 13-8ph
• Stainless Steel 15-5ph
• Stainless Steel Prodec 303
• Stainless Steel 303
• Stainless Steel 446
• Stainless Steel 410s
• Stainless Steel 410
• Stainless Steel 304-304h
• Stainless Steel 17-4
• Stainless Steel 347
• Stainless Steel 440c
• Stainless Steel 309
• Stainless Steel 316-316l
• Stainless Steel Al-6xn®
• Stainless Steel 330
• Stainless Steel 321
• 317l Stainless Steel
• Stainless Steel 310/310s
• Stainless Steel 304l
• Stainless Steel 304
• Stainless Steel 253 Ma

Carbon Steel

• A-36, 204
• Sa-283, 285
• A-572, A-514, 515
• A-516, A-537
• A-572
• A-588
• 1008, 1010
• 1015, 1045, 1060
• Api-5, A53
• A106b
• A179, A209
• A36, 1018, 1020
• 1044, 1045
• 1117, 11l17
• 1035, 1141l
• A36
• A588gra
• A105, WPB, WPC

Titanium

• 10v-2fe-3al
• 6al-4v
• 6al-4v Sta
• 6al-4v Eli
• 6al-2sn-4zr-2mo

Cobalt

• Waspaloy®
• Tribaloy®t-800®
• René 41
• L605
• C263
• 694 (cm-64)
• 188

Standards of pipe fittings:

Some widely used pipe fitting standards are as follows:

Production process of pipe fittings

① Blanking
The pipe materials is used primarily for pipe, process, and bars, the shape of the blank to select the cutting method based on the material properties and product. Blank shape, size and other requirements according to different process requirements.

② Forming (welding)
For all pipe manufacturing process, the steel pipe cross-section is an indispensable process. Due to the forming process of the different products is different, you need a longer length.

③ Heat treatment
The heat treatment process is an important part of the pipe manufacturing. Heat treatment step of heating, insulation and cooling, eliminating the forming process of hardening, residual stress and deformation defects of metal pipe after forming the metal structure, performance of a steel pipe network, restored to the state or its performance in the deformation processing will be improved.

④ Surface treatment
Pipe surface treatment is usually by sandblasting, shot blasting, grinding, pickling method to remove the product surface rust, scratches and other products to achieve a smooth surface to meet the follow-up processing, and inspection requirements.

⑤ Cutting
Cutting pipe, soldering end, structural size, geometric tolerance machining processes. Also includes some pipe cutting, the diameter of processing. The cutting machine is mainly via a dedicated machine or universal; oversized pipe, when the existing machine capacity can not meet the processing requirements, you can also use other methods to complete processing, such as large diameter elbow with gas cutting, grinding method.

⑥ Non-destructive testing
Non-destructive testing is an important process of the possible defects of the test materials and fittings processing. The majority of pipe product standards for the requirements of the non-destructive testing requirements, but requirements are not consistent. In addition to meeting the product standards and ordering requirements, nondestructive testing, more stringent on quality control factory to develop non-destructive testing requirements according to the materials, processes, and internal quality control requirements in order to ensure the quality of manufactured products.

End Beveling of pipe fittings In the behavior, we make beveling after shot blasting, bevel ends are fully machined by advanced equipment Double Beveling Machine ensure the height, length, thickness, O.D. and I.D. are all qualified.

WELDING BEVEL ACC.TO ASME / ANSI B16.9 AND ASME / ANSI B16.28

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.

Send us your technical drawings: yaang.com will supply you with whatever flanges you are looking for. 

END CONNECTIONS
There are four different type of connections that are used for fittings:

1. Butt Weld Fittings – Probably the most common type of fitting. They are easily manufactured and are easily installed. Butt weld fittings can be connected directly to each other. This is called fitting make up.
2. Flanged Fittings – Flanged fittings are piping components where the flange is an integral component of the fitting. These are most often used in water treatment applications or lined piping where welding would be destructive to the liner.
3. Socket Weld Fittings – These fittings have a socket weld connection on each end. They might be used for smaller diameter piping. These fittings utilize a single fillet weld to join the piping with the fitting.
4. Threaded Fittings – Threaded fittings are generally four inches and smaller. The reason for this size constraint is the pipe end needs to be threaded with a male type connection and die sizes are unobtainable in the larger diameters.

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.

Applications and markets of pipe fittings

Fittings are used wherever liquids, gases, chemicals and other fluids are created, processed, transported, or used.

Range of industries is very wide, as shown below:

• Energy related. 
  Oil and gas industries, including upstream (exploration and production), midstream (transportation by ships, pipeline, rail, trucks; storage and wholesale) and downstream (refining into fuels or chemicals; marketing and distribution). Power plants using fossil or nuclear fuels. Geothermal energy for harnessing heat from the earth.
• Food and beverage production. 
  From basic ingredients to elaborate desserts. From milk, to juices and other beverages. Cold chain to keep produce fresh, drinks and frozen foods at a set temperature. Desalination plants to transform seawater into drinking water for arid areas and various tropical islands.
• Pharmaceuticals and biotech production. 
  Medicines and vaccines that treat illnesses and help restore bodies and minds to their top conditions.
• Semiconductor manufacturing: 
  Microchips that go into all electronics, including smartphones, tablets, computers, television sets, telecom networks …
• Pulp and paper production. 
  Newsprint, glossy paper, cardboard boxes, books, writing paper
• Production of construction materials and plastics. From roofing materials, to glassmaking for windows, to copper wiring for transporting electricity, and various plastics throughout houses and office buildings.

How to get high quality pipe fittings?

Testing for pipe 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 (www.steeljrv.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.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

• Dimensions of Pipe Fittings
• Specifications of Steel Pipe Fittings
• Development trend of high pressure pipe fittings
• How to test pipe fitting
• What is Pipe fitting
• Specifications of Steel Pipe Fittings
• What are Outlet Pipe Fittings
• Industrial Standards of Pipe Fittings
• What are forged pipe fittings

References:

1. https://www.yaang.com