What’s a Reducing Coupling?

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Reducing couplings join pipes of different diameters, available in various types and sizes for steel, copper, and PVC pipes. They can be screw-in, compression, braze, or adhesive type. They can accommodate multiple connections and are used in various industries.

Reducing couplings are pipe fittings designed to allow pipes of different diameters to be joined together. These fittings are typically used where small feed or process feed lines are joined into large feed loops or where small diameter fittings are installed. Reducing couplings are available for the most common pipe types, including steel, copper and PVC, and for a wide range of pipe sizes and configuration combinations. These fittings can be screw in, compression, braze or adhesive type, depending on the relevant application.

Joining pipes or tubes of different diameters requires the use of a reducing coupling. These special tube joint fittings are designed to facilitate the joining of a wide range of different size tubes while maintaining the integrity of the tube loop. Reducing couplings are typically no more than standard two-way couplings with a low profile and two different size inlets. Their designs can, however, accommodate multiple connections, elbows or bends and be formed into Y’s, Tee’s or cross joints. Most pipe types, such as copper, steel or PVC, have a range of general purpose or application specific reducing couplings.

The reducer used on steel pipes is usually cast steel with standard threads cut into both ends. These couplings normally feature a simple low profile and screw onto the two lengths of pipe in the same manner as a standard pipe coupling. Reduced flanged joints are also available and have a stepped diameter pipe section between the two flanges. Welded reducer designs are similar to screw-in examples but do not have threads.

A reducing coupling for copper pipes is similar in design to its steel pipe counterpart and is typically brazed or welded across the two pipes. Some copper pipe reducers may be compression type, depending on the application. Just like steel flanged joints, these fittings feature two different sized screw-in compression fittings joined by a stepped length of pipe. The bottleneck profile reduction common to metal fittings is also common among PVC reducing joints. These fittings are usually attached to both ends of the pipe with a PVC adhesive to ensure a good seal.

The reducing coupling can also be used to insert small diameter ancillary equipment, such as valves, flow meters and inspection or maintenance ports, into large diameter pipe loops. This type of reducing joint is often used at the end points of piping loops in the high pressure petrochemical industry. Because few pipe runs consist of only one size of pipe, the reducing coupling is a critical part of the layout of most pipe installations.




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