The basic difference between a coupling and a union is that coupling is for joining pipe to pipe or pipe to a swedge and the union is made for joining and disassemble a part of a piping system (a steam trap or control valve, etc) for maintenance or replacement. The use of couplings or unions is not a code issue.
1. What is A Pipe Coupling?
A pipe coupling is a short piece of pipe used to connect two pipes and the pipe coupling connects two steel pipes through a threaded connection. The seal at the connection is a threaded seal. The disassembly should be disassembled from one end of the pipe in turn, mostly used for lengthening the pipeline.
Pipe coupling materials: carbon steel, stainless steel, alloy steel, PVC, plastic, etc.
Pipe coupling connection methods: threaded connection, welding, socket, etc.
Pipe coupling manufacturing standards: ASME B1.20.1, DIN2986, BS10241.
Pipe coupling manufacturing process: forging and casting (Forging refers to the use of steel ingots or round bars for heating and forging forming, and then processing threads on a lathe; Casting refers to the melting of steel ingots and pouring them into a fixed pipe hoop model, and then cooling them).
Pipe coupling applications: because of their convenient use, pipe couplings are widely used in civil construction, industry, agriculture, and other fields.
2. What Is A Pipe Union?
A pipe union is a commonly used pipe connector that can be easily installed and disassembled. It mainly consists of three parts: nut, cloud head, and flat connection. And the pipe union is generally used for there are front or back ends of valves, water meters, and other equipment in the pipeline, which is convenient for the disassembly and maintenance of this equipment.
Pipe union materials: threaded unions used in industry are generally made of metal with high-pressure resistance. The materials include carbon steel, stainless steel, alloy steel, brass, etc.; threaded unions used in daily life generally include PC, PVC, PE, etc.
Pipe union connection forms: socket welding and threaded connection. (Socket welding is to insert a steel pipe into a socket for welding. Therefore, it is called "socket "Swivel joint"; the threaded connection is to screw the steel pipe into the screw hole for connection. Therefore, it is called "threaded union". )
Pipe union main manufacturing standards: ASME B16.11, MSS SP 83.
Thread union definition: threaded union refers to a pipe connection with thread, which is the most common type of pipe fitting in industry and life. The threaded union makes the connection of the pipeline simpler and easier to disassemble and replace, which greatly saves the cost of the pipeline connection.
Threaded union type: there are equal diameters and different diameters of threaded unions.
3. Pipe Coupling VS Union
Both pipe couplings and pipe unions belong to pipe fittings.
The basic difference between a coupling and a union is that coupling is for joining pipe to pipe or pipe to a swedge and the union is made for joining and disassemble a part of a piping system (a steam trap or control valve, etc) for maintenance or replacement. The use of couplings or unions is not a code issue.
Couplings are pipe fittings in the pipeline. If the pipeline exceeds the length of a single pipe (such as 4m, 6m, etc.), a coupling should be used, which means that the coupling is purely to extend the pipeline; the union can be disassembled as a pipe fitting, that is, the things connected through the union can be removed and replaced, such as the valve side, the radiator side, etc., for maintenance and disassembly. And Pipe unions are generally used on threaded pipes and used on pipes with small pipe diameters. Larger pipe diameters are generally connected by means of flanges, etc., which are also easy to disassemble.
The pipe coupling has threaded coupling, butt welded coupling, and socket coupling, while the pipe union only has threaded union and socket union. Even the slip knot of the socket can be unscrewed with threads. With a union, there is no need to screw the pipe. If there is no threaded connection of the union, the pipe must be moved to disconnect the connection.
From the practical application point of view, the union is used on low-pressure occasions, while pipe coupling is used on high-pressure occasions. The union is a threaded connection, which is generally used in public engineering occasions less than 10kg.
Hebei Sanvo is one of the quality pipe fittings manufacturers and suppliers in China and exports a variety of threaded steel pipe fittings, including carbon steel pipe nipple, carbon steel pipe coupling, stainless steel pipe nipple, stainless steel pipe coupling, and stainless steel threaded pipe fittings.
If you are interested in our pipeline products, please do not hesitate to contact us, we look forward to good news.
Pipe fittings are widely demanded for any piping and plumbing systems used in industrial and commercial applications. Fittings allow pipes to be joined or installed in the appropriate place and terminated or closed where necessary. Fittings are available in various shapes and sizes. They can be expensive, require time, and different materials and tools to install. They are an essential part of piping and plumbing systems. There are thousands of specialized fittings manufactured. Each type of pipe or tube requires its own type of fitting, but usually all pipe fittings share some common features. Pipe fittings are available everywhere where plumbing materials are sold.
1. Elbows: Such pipe fittings are used to change the direction of the flow. They are majorly available in two standard types - 90 and 45 degree angles owing to their high demand in plumbing. The 90 degree elbow is primarily used to connect hoses to water pumps, valves, and deck drains, while the 45 degree elbow is mostly used in water supply facilities, electronic and chemical industrial pipeline networks, food, air-conditioning pipelines, garden production, agriculture, and solar-energy facility.
Available in: Acrylonitrile Butadiene Styrene (ABS plastic), polyvinyl chloride (PVC), chrome-plated brass, chlorinated polyvinyl chloride (CPVC), stainless steel, malleable (galvanized and black), and copper.
2. Couplings: A coupling is a pipe fitting used to stop leakages in broken or damaged pipes. The pipes to be connected should be of the same diameter. The two kinds of couplings used in plumbing are regular coupling and slip coupling. The regular coupling is arranged between the two pipes to prevent further leakages with the help of rubber seals or gaskets on the both sides. The slip coupling itself contains two pipes to repair the damaged lengthy pipes.
Available in: ABS, brass, copper, chrome-plated brass, CPVC, PVC, malleable (galvanized and black), and stainless steel.
3. Union: This type of pipe fitting is almost similar to coupling in terms of functions, but just with a difference, i.e. a union can be removed easily any time while the coupling cannot. A variety of dielectric unions are used to join pipes made of different materials to avoid any kind of galvanic corrosion between them. These pipe fittings comprise of a nut, female and male ended threads.
Available in: Brass, copper, chrome-plated brass, malleable (galvanized and black), PVC, CPVC, and stainless steel.
4. Adapters: Adapters are connected to pipes to either increase their lengths or if pipes do not have appropriate ends. These pipe fittings make the ends of the pipe either male or female threaded as per the need. This permits unlike pipes to be connected without any need of extensive setup. They are mostly used for PVC and copper pipes.
Available in: ABS, CPVC, copper, malleable (galvanized and black), PVC, brass, and stainless steel.
5. Nipple: This is a short butt of a pipe that works as a connection between two other fittings having male threads. A close nipple is a type of pipe fitting having continuous threading on them. They are mostly used in hoses and plumbing.
Available in: Brass, chrome-plated brass, malleable (galvanized and black), PVC, copper, and stainless steel.
6. Reducer: This pipe setting is used to reduce the flow size of the pipe from the bigger to smaller one. There are two kinds of reducers- concentric reducer and eccentric reducer. The former one is in the shape of a cone used for gradual reducing of the size of the pipe. The latter one has its one edge facing the mouth of theconnecting pipe reducing the chances of air accumulation.
7. Tee: This T-shaped pipe fitting used in the plumbing system has one inlet and two outlets arranged at an angle of 90 degrees to the main pipe. This kind of fitting is used to connect the two pipes and make their flow direction as one. If all the three sides of this fitting are same in size, it is called equal tee, otherwise unequal tee.
Available in: ABS, copper, CPVC, PVC, brass, chrome-plated brass, malleable (galvanized and black), and stainless steel.
8. Cross: This type of pipe fitting contains four openings in all thefour major directions. This fitting is adjoined to four pipes meeting at common point. There is either one inlet and three outlets or vice-versa to flow water or any other liquid in four different directions. These kinds of pipe fittings are commonly used in fire sprinkler systems.
Available in: PVC, brass, malleable (galvanized and black), and stainless steel.
9. Flanges: A flange is another pipe fitting used to connect pipes, pumps, valves, and other components to form a full-fledged piping system. They come with a flexibility of easily cleaning or inspecting the whole system from within. They are fixed to the pipes using welding, threading or screwing techniques and then finally sealed with the help of bolts. They are used in residential pump systems and majorly for industrial purposes.
Available in: Brass, copper, malleable (galvanized and black), and PVC.
10. Caps & Plugs: Both these pipe fittings are used to close the ends of the pipe either temporarily or permanently. The plugs are fitted inside the pipe and threaded to keep the pipe for future use. There are a good number of ways a cap can be applied to the pipe like soldering, glue, or threading depending on the material of the pipe.
Available in: ABS, brass, copper, chrome-plated brass, malleable (galvanized and black), CPVC, PVC, and stainless steel.
11. Bushings: These pipe fittings are used to combine pipes of different sizes together by decreasing the size of the larger fitting to the size of the smaller pipe. Bushings are not always threaded inside out and occupy very little space in comparison to a union or coupling used for the same purpose.
Available in: ABS, chrome-plated brass, copper, brass, CPVC, PVC, stainless steel, and malleable (galvanized and black).
12. Wyes: Such type of pipe fittings are used in drainage systems and have a branch line at 45 degrees to keep the flow of water smooth. When the sanitary tees fail to work in a horizontal connection, such cases needs a wye.
Available in: Brass, ABS, and PVC.
13. Valves: Valves are used in the plumbing system to stop the flow of gases or liquids. There are of three types – throttling, isolation, and non-return. The isolation valves are used to disconnect a part of the piping system temporarily for maintenance or repair. The throttling valves are used to regulate the amount of pressure of a liquid in a pipe; they can also withstand the stress caused by this process.
14. Barb: A barb is another useful pipe fitting used in the plumbing system that connects flexible tubing to pipes. It has a male-threaded end on one side that connects with the female threads, and the other end has a single or a multi-barbed tube that is inserted in the flexible tubing.
Available in: Brass for hot water uses and plastic for cold water.
15. Diverter tee: This kind of a tee-shaped pipe fitting is commonly used in the pressurized hydronic heating systems to redirect a part of the flow from the main line to the side branch connected to a heat exchanger.
16. Olet: These fittings are used when the standard size of the fittings fails to serve the purpose.
How are pipe fittings connected to pipes?
Pipe fittings are either male fittings or female fittings. In threaded
pipe fittings, female threads are on the inside while male threads are
on the outside. Pipe fittings that have one female end and one male end
are called street fittings. Pipe fittings are used to connect pipes or
tubes in two ways:
The basic purposes of any pipe fitting are as follows:Pipe fittings are to be chosen considering certain factors. They are as follows:Depending on the purposes served, pipe fittings can be categorized as under:On the basis of the above categories, we give below an idea about the various types of pipe fittings available in the market.