A Short Article on Nipple as Pipe Fitting

In piping, a nipple is a fitting, consisting of a short piece of pipe, usually provided with a male pipe thread at each end, for connecting two other female threaded fittings or pipes. Pipe Nipples are commonly used as adapters from one connection type to another. Pipe nipples are mainly used in low-pressure piping systems.

Pipe nipples are manufactured by cutting a specified length of pipe and applying the desired end connections. The pipe nipple dimensions and material follow from pipe specifications. Similar to pipe, pipe nipples also come in either a seamless or welded construction.

When ordering pipe nipples, the following properties must be specified:

• Diameter
• Length
• Schedule
• Material
• End Connections

The length of pipe nipple is usually specified by the overall length including threads. Pipe Nipples can come in any specified length, but most commonly range between close to 12”.  A close pipe nipple is the shortest piece of pipe necessary to allow for fully threaded end connections, where there is no smooth surface between threads.

Types of Pipe Nipple

There are several different types of pipe nipples in common use. A short list includes:

• Close Nipple / Running Nipple
• Hexagonal Nipple
• Reducing Nipple / Unequal Nipple
• Hose Nipple
• Welding Nipple

Close Nipple / Running Nipple

In its most basic form, a pipe nipple is a short length of pipe with male pipe threads at both ends for connecting other fittings. Generally there is a short distance of unthreaded pipe between the two threaded ends, depending on how far apart you need the attached fittings to be. When there is no unthreaded pipe between the two connecting ends, the pipe nipple is called a “close nipple” or a “running nipple”. In that case, connected fittings come close to touching one another and very little of the nipple can be seen.

Close nipples are difficult to work with. A close nipple can only be unscrewed by gripping one threaded end with a pipe wrench which will damage the threads and necessitate replacing the nipple, or by using a specialty tool known as a nipple wrench which grips the inside of the pipe, leaving the threads undamaged.

Hexagonal Nipple

In pipe nipples where there is a little space between both the threaded ends, there may have a hexagonal section in the center for a wrench to grasp the nipple. These nipples are called as “hexagonal nipple”. This hexagonal section in the middle functions like a nut that can be gripped by a normal wrench, providing a greater mechanical advantage than normal rounded pipe nipple. A hexagonal nipple with more distance between the threaded ends is called a “long hex nipple”.

Reducing Nipple / Unequal Nipple

For ping systems which require a change in pipe dimension, “reducing nipple” or “unequal nipple” is used. Reducing nipple takes a female fitting with a larger connection and attaches it to a smaller one. Care should be taken when using these parts since a reduction in pipe diameter can mean more pressure and greater flow rate in the smaller pipe/fitting.

Hose Nipple

For piping systems which require pipe connection to tubing, “hose nipple” is used. Hose nipple features a male threaded connection on one end and a hose barb on the other end. The hose barb may be the same size as the pipe connection or it may be of reduced size.

Welding Nipple

For piping systems which requires to be connected to welded pipes or fittings, “welding nipple” is used. Welding nipple has a threaded connection on one end and normal cut pipe at the other end. The unthreaded end of the pipe provides more surface area for the use of welding materials to make the stronger connection. One main benefit of welding nipple is that once the unthreaded end is connected, connecting pipes or other fittings to the threaded end becomes much more easy.

Pipe Nipple End Connections

The end connections need to be specified by the customer as well;

Plain Both Ends (PBE), Threaded Both Ends (TBE), Beveled Both Ends (BBE), Threaded One End (TOE), Beveled One End (BOE), Plain One End (POE) or a combination thereof, depending on the ends of the piping system into which the pipe nipple will be fitted.

A Plain Both Ends (PBE) pipe nipple, has both the ends as plain ends, with no thread, typically used to fit a socket weld connection.

A Threaded Both Ends (TBE) pipe nipple has both the ends as threaded ends and used to fit female threaded connections.

A Beveled Both Ends (BBE) pipe nipple has both the ends as bevel ends and is used for welding purposes similar to a buttweld fitting.

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Now it’s Your Turn to Contribute

What do you think about the above article – informative or needs improvements? What are further types of pipe nipples commonly used in piping industry? Any question or query about pipe nipple in your mind? Share your feedback and experience in the comment box below for making this article more meaningful. 

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