A
threaded pipe is a
pipeA pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
with
screw-threadedA screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
ends for assembly.
Tapered threads
The threaded pipes used in some plumbing installations for the delivery of gases or fluids under pressure have a threaded section that is slightly
conicalA cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...
(in contrast to the cylindrical section commonly found on
boltsA screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
and
leadscrewA leadscrew , also known as a power screw or translation screw, is a screw designed to translate turning motion into linear motion...
s). This is called a "tapered thread". The seal provided by a threaded pipe joint depends upon the
labyrinth sealA labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. An example of such a seal is sometimes found within an axle's bearing to help prevent the leakage of the oil lubricating the bearing....
created by the threads; upon a positive seal between the threads created by the deformation of the threads when they are tightened to the proper torque; and sometimes on the presence of a sealing
coatingCoating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...
, such as
thread seal tapeThread seal tape, or teflon tape can be used in many ways, the most common use in America is to seal things. Thread seal tape — commonly known as "Teflon tape", "PTFE tape", "tape dope", or "plumber's tape"–is a polytetrafluoroethylene film cut to specified widths for use in sealing pipe...
("Teflon tape"), or a liquid or paste pipe sealant such as
pipe dopePipe dope is slang for thread lubricants, thread sealing compounds and anaerobic chemical sealant that is used to make a pipe thread joint leak proof and pressure tight...
. Tapered thread joints typically do not include a
gasketthumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
.
Especially precise threads are known as "dry fit" or "dry seal" meaning that no sealant is required 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 over-tightening the joint. The over-stressed 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.
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 sealA labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. An example of such a seal is sometimes found within an axle's bearing to help prevent the leakage of the oil lubricating the bearing....
effect, which may not be enough to satisfy either functional or code requirements. With straight pipe threads, the seal may be provided by an O-ring seated between the shoulder of the male pipe section and an interior surface on the female part.
See also
- AN thread
The AN thread is a particular type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid. It is a US military-derived specification that dates back to World War II and stems from a joint standard agreed upon by the Army and Navy, hence AN.AN sizes range from -2 to -32...
- British standard pipe thread
The British Standard Pipe thread is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external with an internal thread.-Types:...
(BSP)
- Buttress thread
The buttress thread form, also known as the breech-lock thread form, refers to two different thread profiles. One is a type of leadscrew and the other is a type of hydraulic sealing thread form...
- National pipe thread
National Pipe Thread Tapered Thread is a U.S. standard for tapered threads used on threaded pipes and fittings. The taper rate for all NPT threads is measured by the change of diameter over distance. The angle between the taper and the center axis of the pipe is 1° 47′ 24″...
(NPT)
- Nipple (plumbing)
In plumbing and piping, a nipple is a fitting, consisting of a short piece ofpipe, usually provided with a male pipe thread at each end, for connecting two other fittings....
- O-Ring Boss Seal
An O-Ring boss seal is a technique for joining two fluid-carrying pipes, hoses or tubing. In an o-ring boss system, a male threaded part is inserted into a female threaded part, providing a mechanical seal...
- Steel conduit thread
- Piping
Within industry, piping is a system of pipes used to convey fluids from one location to another. The engineering discipline of piping design studies the efficient transport of fluid....
- Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...
- RIDGID
Ridgid is the brandname of the Ridge Tool Company of Elyria, Ohio. Founded in the 1920s as a manufacturer of professional plumbing and HVAC tools, it has branched out into more general-purpose hand tools and power tools. It is now a division of Emerson Electric Company.-External links:*...
, notable manufacturer of pipe threaders
- Tap and die
- United States Standard thread
United States Standard thread , also known as Sellers Standard thread, Franklin Institute thread and American Standard thread, is a standard for inch based threaded fasteners and washers....
External links
- NPT Vs. NPTF Taper Pipe Threads
- Newman Tools Inc. and J.W. WINCO, INC. show the Whitworth
British Standard Whitworth is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes, the others being British Standard Fine thread and British Standard Cycle...
form BSPThe British Standard Pipe thread is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external with an internal thread.-Types:...
or ISOThe International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
pipe thread.