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Pipe fittings are available in various shapes, sizes and materials. Used to connect pipes of different lengths  and sizes, these pipe fittings and flanges should make the right connections. Pipe and pipe-fittings are  produced from a various materials for the transport of wide variety of solids and fluids. The wrong pipe  fitting can lead to many problems like: 1. leaks 2. unwanted flow restrictions and 3. extra cost The proper pipe fittings and flanges let your equipment do the work that you intend it to do. The various  types of pipe fittings include  plugs,  90 degree elbows, 45 degree elbows,  flanges, nipples, concentric  reducers, eccentric reducers,  straight tees, reducing tees, unions, pipe caps, full coupling, half coupling  and many more. You should select the right fittings for your application among the wide range of fitting  types and sizes offered. • Common points to consider The integrity of any fitting for proper functioning depends upon the following:  1. Selection of correct components or fittings appropriate for the application 2. Careful preparation and cleaning 3. Careful installation and assembly 4. Correct tightening and loading • Selecting Your Pipe Fittings The points to consider are as follows:  1. Determine Material Compatibility: Material selection plays a vital role in the proper working of fittings.  There are certain fluids which are not compatible with fitting material and these fittings cause leakage or  system damage. It is very essential to check the material compatibility of your fluid with any chemicals. 2. Check Temperature and Pressure Conditions: Appropriate temperature and pressure ratings are  needed for proper operating conditions. It is necessary to know whether the fittings are capable of  performing at their maximum temperature and maximum pressure ratings because most fittings cannot  perform both the task simultaneously. • Some popular fitting types 1. Threaded Pipe Fittings: These are the most commonly used fittings based on certain standards. For instance, there are threaded fittings of pipes in BSP (British Standard Pipe), NPT (National Pipe Taper), UNF (Unified Fine Thread) sizes  for permanent, high-pressure pipe connections. 2. Socket Weld Fittings:                                                                                                                                                                     A socket weld fitting is unthreaded, but has large sockets at both ends to accept a pipe end. The fitting is  then permanently welded to the pipe.          3. Butt Weld Fittings: Buttweld (BW) fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43. 4. Flanges: A flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system. It  also provides easy access for cleaning, inspection or modification.  • Pipe Thread Sizes This is a very important consideration for any pipe fitting. All pipes were manufactured with specification of a standardized outside diameter (OD) and wall thickness which in turn implies that the nominal pipe size is approximately equal to the inside diameter (ID). Nowadays, various thread configurations are used. We give below an example of British Standard Pipe (BSP) fittings for connecting systems that use both NPT and BSP thread configurations. The table shows a comparison of these two thread styles. Size Threads per inch NPT BSP1/8″27281/4″18193/8″18191/2″14143/4″1414 • To sum up: Selection criteria for buyers  1. Material 2. Pressure Ratings 3. Design and operation 4. Safety information 5. Temperaturepipe fittings and flanges, certain questions need to be answered for that particular pipe fitting and the manufacturer who is manufacturing that particular fitting. Some of these questions are as follows: • Buyer’s assistance Before purchasing  1. Can it handle pressure? 2. Can it handle high temperature? 3. Does it have proven long-term performance? 4. Are the joints or seals reliable? 5. Can it be fitted properly? 6. Does it have confidence of manufacturers? 7. Can it withstand outdoor storage and ultraviolet rays? 8. Can it resist punctures and abrasion? 9. Does it have widespread approval and acceptance from inspectors and engineers? 10. Does it have quality and value?The more the number of “YES”, the better is your product. The more the number of “YES”, the better is your product.

Type Of Steel Pipe Fittings And There Application Since ages, steel is considered best material for making pipe and pipe fittings. The properties in steel like – durability, high strength and high resistance to heat makes it ideal for pipe and pipe fittings. Steel pipe and fittings are used for domestic as well as industrial purposes. Steel pipe fittings are often mixed with other material to enhance the durability and provide better resistance to rust. The most common variety of such steel pipe fittings used are Galvanized steel pipe fitting, Carbon steel pipe fitting and Stainless steel pipe fitting. • Galvanized steel pipe fitting and its applications Through a chemical process, a layer of zinc is coated over the steel. Such pipes are highly resistant to corrosion due to which they are ideal for making pipe and pipe fittings. The zinc layer increases the life of the pipe fittings. They are usually manufactured from seamless tubes or forgings under specific standard. They are available in sizes ranging from 8mm to 150mm and used for piping inside the building and water lines but not ideal for gas pipelines. • Carbon steel pipe fittings and its application Carbon steel is iron based metal, and is durable and stronger than the other steel type which is why it is suitable for manufacturing pipe fittings. Carbon being the main element, it enhances the hardness and strength of the steel. It contains more of carbon with small quantity of manganese and other elements. Carbon steel pipe fittings are used in oil, water, gas and steam lines which are expose to high pressure. They are also considered ideal for different construction purposes. • Stainless steel pipe fittings and its application Stainless steel resists oxidation and corrosion when expose to certain environments. These steel type contains 10% chromium and is a ferrous alloy. They are generally used for household pipelines. Pipe fittings like tees, elbows, unions etc are made of stainless steel.

Pipe welding is performed to join two metal parts of a pipe, like the pipe itself and the fitting, together to prevent leakage. The fitting is a part that comes in various sizes and designs, and it is specifically used to join two or more pipes together. The fitting may also be used to make bends in the pipe line where necessary. • Plug Fittings The plug fitting is used to cap off an end of pipe that would otherwise spill out the material held by the pipe. The plug is placed on the pipe with a socket wrench, which is dependent on the type of fastening hole on top of the plug used. Of the numerous designs, there are hexagon head plug, square head plug, round head plug. • Pipe Union Pipe union fittings are meant to screw onto, and seal, a pipe without requiring a weld. Unionsmay be male to male, female to male or female to female. With a female end, the outside of the fitting is smooth, while threads line the inside. The male end would be the opposite, with threads on the outside. • Pipe Elbows An elbow is a short pipe piece at a 90° angle. The elbow is used to create a turn in the pipes, where an obstruction is able to be moved. The elbow comes in a variety of sizes, including one end being larger than the other to gradually reduce the pipe diameter overall. • Pipe Tees A tee is used to join together three separate pipes. The part looks just like a T, with two ends set in a horizontal fashion and the third end directly in the center, running vertical. • Pipe Welding Aside from the threaded fittings available, there are many types of connections that require welding two smooth surfaces together, like most elbows or tees. The procedure cannot take place until the area is entirely clean. There cannot be dripping water or other material in the pipe while it is being welded. The metal is typically preheated to soften the ends of the pipe and fitting, then the fitting is set into place. Once the piece is in place, the final weld is made. The binding metal, with a melting point of higher than 450° Celsius but less than the melting point of the pipe metal, is held over the fitting and heated until it melts into the cracks. Once the weld is secure, the pipes are checked for leaks, then welded once more if needed.

BUT TWELD FITTINGS: STRAIGHT TEE AND REDUCING TEE The primary purpose of a Tee  is to make a 90° branch from the main run of pipe. Standard there are 2 possibilities, on behalf of the equal tee and reducing tee. The equal tee  (or straight tee) is used as the branch has the same diameter as the run-pipe. The reducing tee is used as the branch has a smaller diameter as the run-pipe. When we talk about a tee NPS 3, a equal tee or straight tee is intended. With a tee  NPS 3 x 2 a reducing tee is intended. Although, officially a reducing tee will be indicated by 3 diameters, namely 3 x 3 x 2 (A x B x C).The A & B measure stands for the Nominal Pipe Size of Run-Pipe, C measure stands for Nominal Pipe Size of Outlet. This designation actually is superfluous, but comes from the time that  tees were available in 3 different ends of diameters, such as 4 x 3 x 2 (A x B x C). In this implementation of course it is necessary, to specify 3 different sizes. That kind of tees is probably no longer available. Applying a equal tee with a concentric reducer or eccentric reducer is now the usual practice. A straight buttwelding Tee or equal buttwelding Tee is available for all common diameters. A Reducing Tee not, because many diameters are not produced, or can not be produced. As an example: A Reducing Tee  NPS 6 x 4 is a standard item for most suppliers, but A Reducing Tee  NPS 16 x 2 is probably not available by any supplier. It would also not economical to use a NPS 16 tee with a NPS 2 outlet; in such situations a Branch Fitting will be used or a Branch Connection will be made. In addition to the defined tees, there are straight  cross and reducing cross. Straight crosses are generally stock items, reducing crosses are often difficult to obtain. By the shape of a tee, the wall thickness can be a critical item. ASME B16.9 only standardizes the end-to-end dimensions, center-to-end dimensions and some “squareness” dimensional tolerances. The wall thickness at the weld line location even is standardized, but not through the rest of the fitting. The standard states that the minimum tolerance will be within 12.5% of the minimum ordered wall thickness of the pipe. A maximum tolerance is specified only at the ends of the fitting. Many providers of welding tees (and elbows) provide one schedule greater thickness so that sufficient wall thickness, after forming, remains. In Tee′s, the crotch radius (T) varies from one manufacturer to another, but some establish itself as a requirement, 1.3 times the wall thickness to maintain the crotch. ASME B16.9-2003 Section 2.2 Design of fittings says: …it is expected that some portion of formed fittings may have to be thicker than the pipe wall with which the fitting is intended to be used Because there is no maximum tolerance for some parts of the fitting, the customer itself must indicate his requirements. Depending on a customer specification, the manufacturer must certify that the manufactured tee, is made according to the requested requirements. He can do that with additional drawings, with additional wall thickness measurements et cetera verified by an independent party or a customers inspector. All these additional tests cost money, so it can happen, that the additional costs, many times higher, as the tee itself.

• Pipe Fittings: Swage Nipples Swage nipples are often used in small diameter pipe systems, and are similar to buttweld reducers. They are concentric swage nipple and eccentric swage nipple available, with various ends. The most common types are: 1. PBE = Plain Both Ends 2. BBE = Beveled Both Ends 3. TBE = Treaded Both Ends Size range NPS 1/8 – NPS 8. Manufactured from A106 Grade B seamless pipe or cold drawn bar which is heat treated in accordance with ASTM A234. Choice of raw material dependant upon size and reduction. Available wall thickness: standard (STD), extra strong (XS), schedule 160, or double extra strong (XXS).

Butt weld fittings: stub end A Stub End always will be used with a Lap Joint flange, as a backing flange; both are shown on the image below. This flange connections are applied, in low-pressure and non critical applications, and is a cheap method of flanging. In a stainless steel pipe system, for example, a carbon steel flange can be applied, because they are not come in contact with the product in the pipe. Stub End is available in almost all pipe diameters. Dimensions and dimensional tolerances are defined in the ASME B.16.9 standard. Light-weight corrosion resistant Stub Ends (fittings) are defined in MSS SP43.

Butt weld fittings: pipe cap Basically a pipe cap will be applied, to shut down the end of a pipe. The pipe cap, as it is shown in the image below, is available for all pipe dimensions, and is sometimes also used for other purposes. The large variations of pipe caps, are the so-called ellipsoidal or dished heads. There are used to close pipes of large diameters, and are similar to those used for constructing vessels. Often you can see on a vessel drawing the name “Klöpperboden” according to ASME F & D, and it is a German name for a special pipe cap head. F & D stands as an abbreviation for flanged and dished, and this form is also known as torispherical head defined. “Korbbogenboden”, is also an german indication that you can find on a vessel drawing. This head is similar to the ellipsoidal head.

With the rapid expansion in the global trade, standardization of various products has become an essential requirement. The standards given to various products significantly contributes towards increasing international trade which in turn bridges the quality gap between the manufacturers, producers and buyers of different nations. In pipe fittings as well, standards play a vital role. The manufacture and installation ofpipe fittings is tightly regulated by various standards and codes. The integrity of pipe fittings and flanges in the piping system depends on various principles used in design, construction and maintenance of the entire system. The components of pipe fittings are made in different materials, in a variety of types and sizes and hence should be manufactured according to common national standards or according to manufacturers’ proprietary item. Some manufacturers also use their own internal piping standards based upon national and industry sector standards. • Difference between “Standard” and “Codes” Piping codes imply the requirements of design, fabrication, use of materials, tests and inspection of various pipe and piping system. It has a limited jurisdiction defined by the code. On the other hand, piping standards imply application design and construction rules and requirements for  pipe fittings like couplings,elbows, tees, flanges, reducers, unions, plugs, pipe caps, nipples etc. Like a code, it also has a limited scope defined by the standard. Factors affecting standards: “Standards” on pipe fittings are based on certain factors like as follows: 1. Pressure-temperature ratings 2. Size 3. Design 4. Coatings 5. Materials 6. Marking 7. End connections 8. Dimensions and tolerances 9. Threading 10. Pattern taper etc. • Types of pipe fitting standards Some widely used pipe fitting standards are as follows: 1. ANSI: The American National Standards Institute ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns “schedule numbers”. These numbers classify wall thicknesses for different pressure uses. 2. ASME: American Society for Mechanical Engineers This is one of the reputed organizations in the world developing codes and standards. The schedule number for pipe fitting starts from ASME/ANSI B16. The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows: ASME/ANSI B16.1 – 1998 – Cast Iron Pipe Flanges and Flanged Fittings ASME/ANSI B16.3 – 1998 – Malleable Iron Threaded Fittings ASME/ANSI B16.4 – 1998 – Cast Iron Threaded Fittings ASME/ANSI B16.5 – 1996 – Pipe Flanges and Flanged Fittings ASME/ANSI B16.11 – 2001 – Forged Steel Fittings, Socket-Welding and Threaded ASME/ANSI B16.14 – 1991 – Ferrous Pipe Plugs, Bushings and Locknuts with Pipe Threads ASME/ANSI B16.15 – 1985 (R1994) – Cast Bronze Threaded Fittings ASME/ANSI B16.25 – 1997 – Buttwelding Ends ASME/ANSI B16.36 – 1996 – Orifice Flanges etc. 3. ASTM International: American Society for Testing and Materials This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM). This is a reputed scientific and technical organization that develops and publishes voluntary standards on the basis of materials, products, systems and services. This is a trusted name for standards. The standards covered by this organization covers various types of pipes, tubes and fittings, especially made of metal, for high-temperature service, ordinary use and special applications like fire protection. The ASTM standards are published in 16 sections consisting of 67 volumes. 4. AN: Here, “A” stands for Army and “N” stands for Navy The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments. For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16″ or ¼”. It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread. 5. BSP: British Standard Pipe BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring. 6. DIN: Deutsches Institut für Normung This refers to the industrial pipe, tube and fittings standards and specifications from the DIN, Deutsches Institut für Normung which in English means the German Institute for Standardization. DIN is the German national organization for standardization and is ISO member body for that country. DIN standard designation The designation of a DIN standard shows its origin where # symbolizes a number: DIN # : Used for German standards having mainly domestic significance or designed as the primary step toward international status. DIN EN # : Used for the German edition of European standards. DIN ISO # : Used for the German edition of ISO standards. DIN EN ISO # : Used if the standard has also been adopted as a European standard. 7. Flanges: Ratings in Classes and Pressure Numbers (PN) Flange Class15030060090015002500 Flange Pressure Number, PN2050100150250420 8. ISO: International Organization for Standardization ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows: “ISO[/IEC] [IS] nnnnn[:yyyy] Title” where nnnnn: standard number yyyy: year published, and Title: describes the subject 9. JIS: Japanese Industrial Standards This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations. 10. NPT: National Pipe Thread National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting.

Size ½” (15 NB) to 48″ (1200NB)Class  150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS ASA 150#, ASA 300# DIN ND 6,10,16,25,40 Etc. MaterialGrade Stainless Steel  ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H,904L  Duplex Steel   ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61  Alloy Steel ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91  Carbon Steel ASTM / ASME A/SA 105 ASTM / ASME A 350 , ASTM A 181 LF 2 / A516 Gr.70 A36, A694 F42, F46, F52, F60, F65, F70In FormSORF, WNRF, BLRF, SWRF, LAP Joint, Threaded, Reducing, Spectacle, etcSpecializeSpecifications As Per The International Standard ASTM, ASME, API, AISI, BS, ANSI, DIN, JIS, MSSP, NACE   Value Added Services» CNC Machining  » Customized FlangesStandardANSI : ANSI B16.5, ANSI B16.47, MSS SP44, ANSI B16.36, ANSI B16.48Type of Flanges :» Weld Neck Flanges – WNRF » Socket Weld Flanges – SWRF » Slip On Raise Face – SORF » Blind Raise Face – BLRF » Lap Joint Flanges » Screwed (Threaded) Flanges » Long Weld Neck Flanges » Plate Flanges » Spectacle Blind » Ring Joint » Large Dia Flanges » Orifice Flanges » Girth Flange

• Market Trends Pipe fittings manufacturing and material specifications are application-dependent. User consultation with the suppliers of pipe fittings is typical for optimization of component selection. There are certain safety and environment related issues facing the pipe fittings industry. This is an important factor influencing buyers to select or buy only quality products and the best fittings for specific applications. Pipe fittings manufacturers are responding by devoting more time and resources to product development and service. There is also a recent trend to give more importance in the design process of these highly demanded fittings. The growth area for pipe fittings manufacturers is in manufacturing high-tech and developed products, rather than making commodity-type products. Pipe Fittings Industry Thanks to the large-scale construction and development activity in the recent past, the pipes and pipe fittings industry is a rapidly growing industry. Pipes are essential for connectivity, be it for water supply inlets to provide for clean and waste water distribution systems, agricultural watering system, liquid discharge installations, water sprinkling and dropping systems, sanitation and sewerage disposal etc. Together with pipes, pipe fittings are equally important because no pipes can be installed without the use of fittings. Pipe fittings are essential to connect pipes together. There are various types of pipe fittings like couplings, elbows, tees, flanges, reducers, unions, plugs, pipe caps, nipples, etc. which are used to connect pipes, tubes and other fittings for various configurations. Pipe and pipe fittings are manufactured from a wide variety of materials including stainless steel, brass, copper, carbon steel, cast iron, etc. • Factors affecting the pipe fittings industry The growth of this industry is dependent on various factors. In all pipes and piping system used in various industrial, commercial and residential applications,pipe fittings play a vital role. No sealing in pipes and tubes is impossible without the use of pipe fittings. Starting fro labor to government policies, many factors affect this industry. Two important factors are as follows: 1. Capital expenditure, including private machinery and equipments 2. Real household disposable income Pipe fittings of all types, materials and sizes are critical in construction, building, chemical, energy, and other industrial applications. According to a recent estimate, the pipe fittings industry witnessed a growth of close to 8-10% globally in the last few years. The global export market of the metal pipe fittings comprises US, Western Europe, Australia, and Japan. China is one of the major exporting nations. The pipe fittings industry is expected to experience considerable change and varying growth rates in coming years.

Chemical & Mechanical Composition Of Stainless Steel: stainless steel pipe fittings, stainless steel buttweld fittings, stainless steel socketweld fittings, stainless steel threaded fittings, stainless steel flanges –Chemical & Mechanical Composition Of Stainless Steel CHEMICAL COMPOSITION ( IN PERCENTAGE )GradeC (Max)Mn (Max)P (Max)S (Max)Si (Max)CrNiMoNitrogen (Max)Cu/ Others3010.1520.0450.03116.00 – 18.006.00 – 8.00–0.1–3040.0820.0450.030.7518.00 – 20.008.00- 10.50–0.1–304L0.0320.0450.030.7518.00 – 20.008.00- 12.00–0.1–310S0.0820.0450.031.524.00- 26.0019.00 – 22.00–––3160.0820.0450.030.7516.00 – 18.0010.00 – 14.002.00 – 3.000.1–316L0.0320.0450.030.7516.00 – 18.0010.00 – 14.002.00 – 3.000.1–3170.0820.0450.030.7518.00 – 20.0011.00 – 14.003.00 – 4.000.1–317L0.0320.0450.030.7518.00 – 20.0011.00 – 15.003.00 – 4.000.1–3210.0820.0450.030.7517.00 – 19.009.00 – 12.00–0.1Ti5 ( C + N )  Min or 0.70 max3470.0820.0450.030.7517.00 – 19.009.00 – 13.00––Cb= 10x ( C Min )  or 1.00 Max4090.0810.040.01110.50 – 11.750.5––Ti= 6x (C+ N )  Min or 0.70 Max409M0.030.81.20.030.030.40.7511.00- 12.001.5 max.––Ti= 6x (C) Min  or 0.70 Max410S0.0810.040.03111.50- 13.500.6–––4100.1510.040.03111.50- 13.500.75–––4200.350.50.0350.0150.512.00 – 13.000.20.3–––4300.1210.040.03116.00 – 18.000.75–––JSL AUS0.087.08.00.070.030.7515.50 – 16.504.25 – 4.75––0.9 – 1.10JS- 2030.089.2510.250.070.030.7514.25 – 15.252.25 – 2.75––1.60- 2.0301M0.14.55.5   0.060.030.7514.50 – 15.506.0 – 7.0––1.70- 1.90* Thickness of 1.27mm & below will have elongation of 20% min.

1. Hydraulic fittings Hydraulic systems use extremely high fluid pressures to create useful work, such as in the hydraulic actuators for powered machinery such as bulldozers and backhoes. 2. Elbow Short radius 45° elbow or regular 45° elbow  Long radius 90° elbow or sweep 90° elbow  An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made. The ends may be machined for butt welding elbow, threaded (usually female) elbow, or socketed elbow, etc. When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow. Elbows are categorized based on various design features as below: Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter 90 Degree Elbow – where change in direction required is 90° 45 Degree Elbow – where change in direction required is 45° A 90 degree elbow is also called a “90 bend” or “90 ell”. It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe. It used to change the direction in piping and is also sometimes called a “quarter bend”. A 90 degree elbow is available in many materials like copper, cast iron, carbon steel, stainless steel, galvanized steel. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains.  A 45 degree elbow is also called a “45 bend” or “45 ell”. It is commonly used in water supply facilities, food industrial pipeline networks, chemical industrial pipeline networks, electronic industrial pipeline networks, air conditioning facility pipeline, agriculture and garden production transporting system, pipeline network for solar energy facility, etc. Most elbows are available in short radius or long radius variants. The short radius elbows have a center-to-end distance equal to the Nominal Pipe Size (NPS) in inches, while the long radius elbows is 1.5 times the NPS in inches. Short elbows are widely available, and are typically used in pressurized systems. Long elbows are typically used in low-pressure gravity-fed systems and other applications where low turbulence and minimum deposition of entrained solids are of concern.  3. Coupling  Pipe coupling, a coupling connects two pipes to each other. If the size of the pipe is not the same , the fitting may be called a reducing coupling or reducer. By convention, the term “expander” is not generally used for a coupler that increases pipe size; instead the term “reducer” is used. 4. Union  A combination pipe union and reducer fitting, A union is similar to a coupling, except it is designed to allow quick and convenient disconnection of pipes for maintenance or fixture replacement. While a coupling would require either solvent welding, soldering or being able to rotate with all the pipes adjacent as with a threaded coupling, a union provides a simple transition, allowing easy connection or disconnection at any future time. A standard union pipe is made in three parts consisting of a nut, a female end, and a male end. When the female and male ends are joined, the nuts then provide the necessary pressure to seal the joint. Since the mating ends of the union are interchangeable, changing of a valve or other device can be achieved with a minimum loss of time. Pipe unions are essentially a type of flange connector, as discussed further below. 5. Reducer Reducer fittings, a reducer allows for a change in pipe size to meet hydraulic flow requirements of the system, or to adapt to existing piping of a different size. Reducers are usually concentric reducers buteccentric reducers are used when required to maintain the same top- or bottom-of-pipe level. 6. Olets 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, olets are generally used. The following are few configurations of olet connections: Flanged Olet Socket-Weld Olet Threaded Olet Lateral Olet Elbow Olet Nipple Olet Butt-Weld Olet 7. Tee  Pipe tee, a tee is the most common pipe fitting. It is available with all female thread sockets, all solvent weld sockets, or with opposed solvent weld sockets and a side outlet with female threads. It is used to either combine or split a fluid flow. It is a type of pipe fitting which is T-shaped having two outlets, at 90° to the connection to the main line. It is a short piece of pipe with a lateral outlet. A tee is used for connecting pipes of different diameters or for changing the direction of pipe runs. They are made of various materials and available in various sizes and finishes. They are extensively used in pipeline networks to transport two-phase fluid mixtures. They are categorized as: Equal tee Unequal tee When the size of the branch is same as header pipes, equal tee is used and when the branch size is less than that of header size, reduced tee will be used.  8. Cross Cross fittings are also called 4-way fittings. If a branch line passes completely through a tee, the fitting becomes a cross. A cross has one inlet and three outlets, or vice versa. They often have solvent welded socket ends cross or female threaded ends cross. Cross fittings can generate a huge amount of stress on pipe as temperature changes, because they are at the center of four connection points. A tee is more steady than a cross, as a tee behaves like a three-legged stool, while a cross behaves like a four-legged stool. (Geometrically, “any 3 non-colinear points define a plane” thus 3 legs are inherently stable.) Crosses are common in fire sprinkler systems, but not in plumbing, due to their extra cost as compared to using two tees. 9. Cap  Pipe cap, a type of pipe fitting, usually liquid or gas tight, which covers the end of a pipe. A cap is used like plug, except that the pipe cap screws or attaches on the male thread of a pipe or a nipple. They have a solvent weld socket end cap or a female threaded end cap. If a solvent weld cap is used to provide for a future connection point, several inches of pipe must be left before the cap. This is because when the cap is cut off for the future connection, enough pipe must remain to allow a new fitting to be glued onto it. In plumbing systems that use threaded cap, the cap has female threads. Industrial caps can be round, square, rectangular, U-shaped, I-shaped and have a round hand grip or a flat hand grip. 10. Plug A plug closes off the end of a pipe. It is similar to a cap but it fits inside the fitting it is mated to. In a threaded iron pipe plumbing system, plugs have male threads. 11. Nipple A short stub of pipe, usually threaded steel, brass or copper; occasionally just bare copper. A nipple is defined as being a short stub of pipe which has external male pipe threads at each end, for connecting two other fittings. Nipples are commonly used for plumbing and hoses, and second as valves for funnels and pipes. 12. Gender of fittings Piping or tubing are usually (but not always) inserted into fittings to make connections. To avoid confusion, connections are conventionally assigned a gender of male or female, respectively abbreviated as “M” or “F”. Common fittings for both piping and plumbing, While there are hundreds of specialized fittings manufactured, some common types of fittings are used widely in piping and plumbing systems.