types of pipe fittings

Types of pipe fittings and how to choose them

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Various types of pipe fittings and different shapes of them are available in different sizes and materials depending on the expected application.

Piping systems are connected to each other or branched by a series of fittings. Depending on the expected application, different types of pipe fittings and different shapes of them are available in different sizes and materials. Fitting material is usually selected with the same material as the pipe, and common materials for fitting are: stainless steel, carbon steel, brass, copper, plastic, PVC, and so on.

Fitting size Depending on the method of connecting to the pipe, a slightly smaller or larger amount or the same size is selected. Types of piping fittings such as pipes are used in various industries such as oil and gas, water and wastewater, etc., and their characteristics vary depending on the industry in which they are used.

Proper installation of fittings and their sealing is very important. And it is necessary to choose the best method for connecting fittings and valves and fittings according to the fluid passing through the pipe, pipe material and connection, temperature and fluid pressure and the importance of sealing in the system.

What is the purpose of Pipe fittings

Various types of pipe fittings are used in the piping system for various purposes, some examples of which are as follows:

  • Connect two or more different pipes or hoses to each other
  • Connecting different components of the piping system to the main system
  • Connecting pipes to various devices and equipment such as pumps, purification equipment and…
  • Redirect fluid flow and piping system
  • Maintain or regulate fluid flow
  • Blocking or sealing the pipe

Some examples of common and widely used fittings are:

Elbow, three-way, four-way, nozzle, booster, cap, connection of two ends of Union nut and… In the continuation of this article, complete explanations about the types of pipe fittings and their standards and their application and method of use will be given.

Types of pipe fittings

Elbow is one of the most important types of pipe fittings used in piping systems. These fittings are used to change the piping direction. Elbows are usually 90 degrees and 45 degrees, which can change the flow in the piping system, according to the angles.

Reducing elbows are used when the two pipes connected to the elbow are not the same size. The lowering elbow actually has different sizes in the input and output size, the smaller end of which is connected to the smaller tube.

The elbow radius is actually the radius of a circle whose elbow is a segment of this circle. Elbows have two types of short radius and long radius, in the first type the elbow radius is equal to the nominal diameter of the pipe and in the second type the elbow radius is 1.5 times the nominal diameter of the pipe. For some piping systems, such as powder and suspended particle transfer systems, in order to ensure the system more and not to drop high pressure in the flow path, which causes sediment formation and duct obstruction, it is necessary to consider the elbow radius 10 times the nominal diameter of the pipe. To be taken.

The size of the elbows varies according to the dimensions of the tubes and their size is usually expressed as the outer diameter of the elbow in the form of NPS. The material of the elbows also generally depends on the material of the tube. The elbows can be connected to the pipe through different methods depending on the different conditions of the system and the fluid passing through the pipe and the dimensions and pressure of the pipeline, some of which are: threaded fittings, flange fittings, male fittings and Female, thermal press fittings, adhesive fittings and etc.

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Three-way and four-way

The purpose of using tees and crosses is to create a branch in the pipeline. Three-way is usually used for a situation where we want to separate a sub-branch from the main path of the pipe, two of which are connected to the main pipeline and the third path to the branch.

The third three-way outlet can be more or less in diameter than the two parallel outlets and can also be perpendicular to the main direction of the pipeline or at an angle of 45 from the main line.

Crossroads have four different flow channels that make a 90 degree angle with each other. These fittings include three inputs and one output or vice versa one input and three outputs. It is also sometimes taken from the main path of a bifurcated pipe. Depending on the expected use of the system, a valve can be installed in the path of each of the outlets so that the flow through each of the branches can be controlled and, if necessary, their path can be blocked.

types of pipe fittings


Reducers (Reducer) are used to connect two pipes of different size and cross section. The inlet current to these fittings decreases in pressure and accelerates when it exits from the larger side, and increases in pressure and deceleration when it exits from the narrower side when exiting from the smaller side.

Reducers have two types, Concentric Reducer and Eccentric Reducer. The concentric type is installed coaxially with both pipes and its diameter is gradually reduced, which can cause air accumulation and cavitation and damage to the system. In the eccentric type of reducers, one reducing edge is completely parallel to the edge of the two tubes and the diameter reduction is done only on one side of the reducing and in a non-gradual and heterogeneous way. In this type of reducers, air accumulation and cavitation are not possible. One of the disadvantages of these reducers is that they cause more pressure drop and more turbulence in the flow path.

Reducers are widely used in pneumatic systems, refrigeration cycles (specific type of ejector) and the chemical industry. These fittings come in different sizes Are available and have high operational flexibility in the piping system.


Coupling is a type of fittings that is used to connect two pipes of the same size. These types of fittings provide good sealing and significantly reduce leakage. Couplings are used when the pipe is corroded or damaged to eliminate system leaks. They are also used instead of welded or flange fittings to connect two pipes.

Couplings are available in all different pipe sizes and include ABS, copper, brass, nickel-chrome, galvanized steel, carbon steel, stainless steel, plastic and PVC .

Union fittings

Union fittings have a structure almost similar to couplings, except that the unions can be easily removed from the system at any time, while this is not easy for couplings.

The fittings type of unions is male and female fittings and therefore it is easy to separate them. A galvanized coating is commonly used on these fittings to prevent any corrosion on them.

Olet fittings

Olet fittings are used when there are no fittings of suitable sizes for our intended use. If the size of the inlet and outlet pipes are different, the first one should be used. There are several types of olives, including:

Butt-weld Olet

Socket-weld Olet

threaded Olet

Elbow Olet

Nipple Olet

Lateral Olet

Sweep Olet

Flange Olet

Plug and Cap

Caps are used to block the flow path. Path blocking is applied because sometimes by making changes to the plumbing plan and building a new system, it is necessary to close some paths of the old system or so-called blind. Also, during repairs and inspections in the system, it is necessary to block the pipe path so that the flow does not spill out, in which case it is necessary to use caps.

The type of plug fittings to the pipe is usually threaded or male and female, which is the male and female type of pipe fitting cap. The cap has a completely similar structure to the Plug, except that the Cap is female and the tube is male.


Bushings are another type of pipe fittings that are used to connect two pipes of the same size. Bushings usually have a threaded structure. The structure of bushings is much denser than that of reducers. Bushings are not commonly used to connect flexible systems and plastic pipes to metal pipes. Bushings are available in a variety of materials including copper, brass, nickel-chrome, galvanized steel, carbon steel, stainless steel, plastic, PVC and..


Flanges are a type of pipe fittings between components such as pipes, pipe fittings, fittings and valves. These components provide easy access to clean, inspect or modify the piping system. Flanges are usually welded or screwed. Flange fittings are made by screwing two flanges with washers between them to seal and prevent leakage.

Flanges are produced in different materials such as stainless steel, cast iron, aluminum, brass, bronze, plastic and.. But most of the material used in making flanges is carbon steel with machined surfaces. ASME B16.5 standard describes the dimensions and types of different flanges.

types of pipe fittings

Criteria for selecting suitable pipe fittings

Choosing the right Fittings to meet our needs depends on a number of factors, some of which are listed below:

In general, when buying fittings, it should be noted that the types of piping fittings include two general types of male and female in male and female fittings, which should be male fittings for the inner thread of the pipe, considering that the threads of the pipe are inside or outside it. And select the material fittings for the external thread of the pipe.

Different types of pipe fittings include threaded fittings, flange fittings, adhesive fittings, thermal fittings, welding fittings and.. Depending on the material of the pipes and the sealing conditions and the fluid inside the pipe, the proper fittings method for the fittings must be chosen. For example, for connecting plastic and PVC pipes and fittings, thermal and press fittings are mostly used, and for connecting pipes and metal fittings, where the system does not have a sufficient degree of freedom for screw fittings and the sealing of the system is of great importance. Welding is used.

Fittings material (Materials Of Construction)

As a general rule, the material of the fittings used in the piping system must be of the same material as the pipes connected to it. But in some cases, materials that conform to specific codes or standards can also be used in pipes of another material.

Fittings diameter

The diameter of the fitting is usually equal to the diameter of the pipe connected to it. Just keep in mind that to keep the flow constant, the end of the pipe fittings must be slightly larger than the rest of the pipe so that it can hold the fittings without narrowing the inside diameter (ID) of the pipe.

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