PLUG or CAP

A plug and a cap are accessories used to close an industrial installation. It is also convenient to use the term "fittings" for all connecting and supplementary elements of an installation - the customary Polish term "armatura" is unclear and ambiguous.

The following refers primarily to threaded metal components in industrial installations.

So what kind of fittings are a plug and a cap: in other words, they are stoppers, elements that close openings, pipe ends. They close them during the operation of the installation and are used primarily for maintenance, inspection, cleaning, etc. during breaks in the operation of the installation.

A plug looks like a type of screw: it has a threaded shank and a head that can be gripped with a tool for screwing it in. The difference results from the application: a screw connects structural elements together, while a plug only closes certain spaces.