Brass NPT threaded Pipe Plug in a Caliper

A threaded pipe is a

pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circular ...

with screw-threaded ends for assembly.

Tapered threads

The threaded pipes used in some plumbing installations for the delivery of gases or liquids under pressure have a tapered thread that is slightly

conical A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines c ...

(in contrast to the parallel sided cylindrical section commonly found on bolts and

leadscrew A leadscrew (or lead screw), also known as a power screw or translation screw,Bhandari, p. 202. is a screw used as a linkage in a machine, to translate turning motion into linear motion. Because of the large area of sliding contact between ...

s). The seal provided by a threaded pipe joint depends upon multiple factors: the labyrinth seal created by the threads; a positive seal between the threads created by thread deformation when they are tightened to the proper torque; and sometimes on the presence of a sealing

coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Pow ...

, such as

thread seal tape Thread seal tape (also known as PTFE tape, Teflon tape, or plumber's tape) is a polytetrafluoroethylene (PTFE) film tape commonly used in plumbing for sealing pipe threads. The tape is sold cut to specific widths and wound on a spool, making it ...

or a liquid or paste pipe sealant such as

pipe dope Pipe dope is any thread lubricant, thread sealing compound, or anaerobic chemical sealant that is used to make a pipe thread joint leak proof and pressure tight. It is also referred to as "thread compound" or "pipe thread sealant." Although c ...

. Tapered thread joints typically do not include a

gasket Some seals and gaskets A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. It is a deformable material that is used to ...

. Especially precise threads are known as "dry fit" or "dry seal" and require no sealant for a gas-tight seal. Such threads are needed where the sealant would contaminate or react with the media inside the piping, e.g., oxygen service. Tapered threaded fittings are sometimes used on plastic piping. Due to the wedging effect of the tapered thread, extreme care must be used to avoid overtightening the joint. The overstressed female fitting may split days, weeks, or even years after initial installation. Therefore many municipal plumbing codes restrict the use of threaded plastic pipe fittings. Both

British standard British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the ...

and

National pipe thread American National Standard Pipe Thread standards, often called national pipe thread standards for short, are United States national technical standards for screw threads used on threaded pipes and Piping and plumbing fitting, pipe fittings. They in ...

standards specify a thread taper of 1:16; the change in diameter is one sixteenth the distance travelled along the thread. The nominal diameter is achieved some small distance (the "gauge length") from the end of the pipe.

Straight threads

Pipes may also be threaded with cylindrical threaded sections, in which case the threads do not themselves provide any sealing function other than some labyrinth seal effect, which may not be enough to satisfy either functional or code requirements. Instead, an O-ring seated between the shoulder of the male pipe section and an interior surface on the female, provides the seal.

External links

NPT Vs. NPTF Taper Pipe Threads

an

show the Whitworth form BSP or ISO pipe thread. {{DEFAULTSORT:Threaded Pipe Piping Plumbing

Tapered threads

Straight threads

See also

External links