All About Steel Pipe Fittings

A steel pipe fitting is a piece of steel used to connect separate sections of pipe together. Fittings can be used to extend lengths of pipe or to create angles in a piping system, and they’re necessary to regulate and manipulate the flow of air or fluid. Steel pipe fittings come in a variety of shapes and styles including tees, adapters, elbows, couplings, unions, reducers, and more.

Tee

A tee is one of the most common types of pipe fittings and is used to combine or divide the flow of fluids. Tees have three openings to create a “T shape” and most often connect pipes of identical sizes, though they can be used to connect pipes with varying diameters as well.

Adapter

A steel pipe adapter is a fitting that connects together pipes of different materials or sizes. There are several varieties of adapters, including expansion adapters, bell adapters and adapter spools. Expansion adapters are designed with a flexible section that can absorb the expansion or contraction from two dissimilar pipe materials. Bell adapters have a stainless-steel backup ring to keep the seal between their adjoining pipes tight. Finally, adapter spools have openings on each end with different diameters, allowing pipes of different sizes to be connected.

Elbow

An elbow is an adapter that’s installed between two lengths of pipe to create a change of direction. Elbows are typically designed at 45-degree angles (called a “45 bend”) or 90-degree angles (called a “quarter bend”), though 22.5-degree elbow fittings are sometimes also used. Elbows are commonly applied in water-supply facilities, food, chemical and electronic industrial pipeline networks, agriculture and garden production, air conditioning pipelines, and solar energy facility piping. Similarly, longer pipe elbows can be used in low pressure, gravity fed systems.

Cross

A cross, also known as a four-way fitting, is the center point of a four-way connection, with one inlet and three outlets. Because they are at the center of four connection points, cross fittings may cause stress to pipes, especially as temperatures change. Crosses are commonly used in fire sprinklers and other systems where temperature change is not an issue.

Coupling

Like an adapter, a coupling connects two pipes together. However, where an adapter is meant to connect two pipes of different materials or sizes, a coupling connects like pipes. There are two types of steel pipe couplings: regular and slip. A regular coupling has a small ridge in its center that prevents a pipe from being over-inserted (which would result in the under-insertion of the second pipe and therefore a compromised connection). A slip coupling, on the other hand, is made without this ridge, allowing it to be slipped into place at any level. Slip coupling is often used in pipe repair, such as in instances where a pipe has a leak or had to be cut temporarily during a project.

Union

Like a coupling, a union connects two identical pipes, but it’s different in that it allows for easy disconnection of the pipes. Unions are most often used in systems where disassembly is necessary, such as those that require maintenance. A union consists of three parts: a nut, a female end and a male end. When the female and male ends are connected, the nut is used to seal the joint.

Nipple

A nipple is a short steel stub of pipe that connects two other fittings of equal diameter. Nipples are commonly used in plumbing systems and with hoses.

Cap

A cap is an airtight cover that is used to close the open end of a pipe. Caps attach to the outside of pipes and may be round, square, rectangular, U-shaped or I-shaped.

Reducer

A steel pipe reducer connects a pipe with a larger diameter to a pipe with a smaller one. Reducers are often necessary to meet a system’s hydraulic flow requirements, or to adapt an existing pipe to one of a different diameter. Reducers come in many sizes and can be made to match pipes with a range of diameters.

To learn more about steel pipe, check out our blog titled "All About Steel Pipe".

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