Using the word "nipple" to describe a small section of pipe is surprising for those who deal with plumbing supplies irregularly, and it is not clear when and where people began to use the term "nipple" to refer to pipes. Its history can be traced back at least to the 1530s. Its root is the meaning of "mouth, mouth, nose" - literally "little Bulge".
Type and application of pipe nipple:
However, whatever the basis of the term, it is now widely used in pipelines. Moreover, there are many different types of/subsets of tube streets that can compete. The shortlist includes threaded nipples, hexagon streets, long hexagon streets, reducer nipples, etc. I'm sure there are more. In its most basic form, the street is a short length of pipe with screwed ends for connecting other fittings. In general, the unthreaded pipe distance between the two threaded ends is very short, depending on how far you need the fitting, and in the absence of a hose, the part may be referred to as a "close joint" or "run joint". In this case, you can see that the connected fittings are close to each other and it is very small.
Although some structures require such a tight position, tight nuts can be difficult to operate because unscrewing them requires keeping the threaded part tight and may damage the thread. When you can leave a small space between them, finally, you can use the "hex nipple", which has a hex in the middle. Its function is just like the nut that an ordinary wrench can hold, providing a greater mechanical advantage than an ordinary round pipe.
The hexagon joint with a larger distance between the threaded ends is called "long hexagon nipple". For the items that need to change the pipe size, you can buy "reducer nipple", sometimes it is called "unequal joint", which has a larger connection degree and can be connected to a smaller pipe nipple. Care should be taken when using these parts, as a reduction in the pipe diameter may result in greater pressure and greater flow lines/connections.