Also known as pneumatic couplings, quick disconnects, air couplers, quick connect couplers, and quick couplers, hand-operable air-line fittings allow manual disconnection of gas supply lines, including compressed air and breathable air (a subset of breathing gases). Most fittings do not have regional standardization but have become de facto standards through popular adoption.
A coupled pair consists of a male nipple or plug and a female coupler or socket. One side is connected to a flexible supply hose; the other may be attached to a manifold, valve, tool, or another hose. A female coupler is used on the supply side, and a male nipple is used on the receiving side.
Fitting profiles have identifiable geometry on the male end, but care must be taken to use a compatible coupler. Couplers use springs and balls to lock mating nipples into place. A seal is effected using O-rings along the shaft of the nipple or by compression by the tip. Although incompatible pairs may latch, the sealing performance may be compromised.
For breathable air applications such as SCBA, these may found on both sides of the first-stage and second-stage pressure regulators (very similar to SCUBA diving regulators) to allow for rapid and tool-free return-to-service. [1] For breathable air applications such as supplied-air and mixed supplied-air with SCBA backup, the quick-disconnect fittings allow movement of a worker from one supplied-air station to another.
These fittings or special-service variants may also be found in hydraulic applications and alternative compressed gas applications (Oxy-acetylene welding and cutting, fuel gases, NSF C-2 food-contact, etc.).
European convention uses DN (nominal diameter) to denote a nominal size of each fitting. Various manufacturers specify series or styles for each profile. Fittings are commonly referred to by their manufacturer name/series, i.e., "Rectus 25" for the common European standard. Proprietary designs supported by a single manufacturer are not included in this table. [2] [3]
| Manufacturer Series | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Profile | Description | DN | Standards | RTC | CEJN | Rectus | Parker | Milton | PCL | Walther |
 | German/Walther 2.5 | 2.5 | 200.03 | 141 | 50 | LP-002 | ||||
 | German/Walther 2.7 | 2.7 | 020 | 20/91 | 06-003 | |||||
 | US Industrial 1/8" HP | 3 | ISO 6150C | 170.03 | 303 | |||||
 | German/Camozzi/EWO/Kani | 5 | 021 | 223 | 21/90 | |||||
 | Schrader 1/4" | 5 | 017.06 | 17 | TL | PF | ||||
 | US Industrial 1/4" | 5.3/5.5 | A-A-59439, ANSI T3.20.14-1990,MIL-C-4109F, ISO 6150B | 023 | 310 | 23/24 | 20/30 | M | ISO B12 | |
 | US Industrial 1/4" HP | 5.5 | ISO 6150C | 170.06 | 291 | 18 | ||||
 | Tru-Flate/Automotive 1/4" | 10 | T | |||||||
 | ARO 210 | 5.5 | 014/022 | 300 | 14/22 | 50 | A | A Style | ||
 | Lincoln | 70 | L | |||||||
 | UK/English Industrial/PCL | 5.5 | 019 | 19 | Standard | |||||
 | German/Walther 6 LP | 6 | 200.05 | 52 | LP-006 | |||||
 | German/Walther 6 SP | 6 | 200.06 | 51 | SP-006 | |||||
 | Scandinavian 6.5/7.4 | 6.5/7.4 | 032.06 | 303 | 31/1300 | |||||
 | Hi-Flow/Eurostandard 7.2 | 7.2/7.4 | 025/026 | 320 | 25/26 | V | XF-Euro | |||
 | Asian/Japanese/Nitto | 7.5 | 013 | 315 | 13 | KF | ||||
 | Tru-Flate/Automotive 3/8" | 10 | P | |||||||
 | US Industrial 3/8" | 8.2/8.5 | A-A-59439, ISO 6150B | 030 | 430 | 30 | 20/30 | H | ||
 | US Industrial 3/8" HP | 8 | ISO 6150C | 170.08 | 381 | 84 | ||||
 | ARO 310 | 9 | 014.09 | 40 | AA | |||||
 | Scandinavian 9.5/10 | 9.5/10 | 032.10 | 408 | 32/1800 | |||||
 | Eurostandard 10 | 10 | 027 | 410 | 27 | |||||
 | Schrader 1/2" | 017.10 | TL | |||||||
 | US Industrial 1/2" | 11 | A-A-59439, ISO 6150B | 037 | 550 | 37 | 20/30 | G | ||
 | US Industrial 1/2" HP | 11 | ISO 6150C | 170.11 | 471 | |||||
 | Tru-Flate/Automotive 1/2" | 10 | G | |||||||
 | German/Walther 12 | 12 | 200.12 | 57 | LP-012 | |||||
A scuba set, originally just scuba, is any breathing apparatus that is entirely carried by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness or rigging by which it is carried and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.
Aqua-Lung was the first open-circuit, self-contained underwater breathing apparatus to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin-hose diving regulator, or demand valve. The Aqua-Lung was invented in France during the winter of 1942–1943 by two Frenchmen: engineer Émile Gagnan and Jacques Cousteau, who was a Naval Lieutenant. It allowed Cousteau and Gagnan to film and explore underwater more easily.
Pneumatics use of gas or pressurized air in mechanical systems.
A self-contained breathing apparatus (SCBA) is a respirator worn to provide an autonomous supply of breathable gas in an atmosphere that is immediately dangerous to life or health from a gas cylinder. They are typically used in firefighting and industry. The term self-contained means that the SCBA is not dependent on a remote supply of breathing gas. They are sometimes called industrial breathing sets. Some types are also referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA). Unofficial names include air pack, air tank, oxygen cylinder or simply pack, terms used mostly in firefighting. If designed for use under water, it is also known as a scuba set.
A diving regulator or underwater diving regulator is a pressure regulator that controls the pressure of breathing gas for underwater diving. The most commonly recognised application is to reduce pressurized breathing gas to ambient pressure and deliver it to the diver, but there are also other types of gas pressure regulator used for diving applications. The gas may be air or one of a variety of specially blended breathing gases. The gas may be supplied from a scuba cylinder carried by the diver, in which case it is called a scuba regulator, or via a hose from a compressor or high-pressure storage cylinders at the surface in surface-supplied diving. A gas pressure regulator has one or more valves in series which reduce pressure from the source, and use the downstream pressure as feedback to control the delivered pressure, or the upstream pressure as feedback to prevent excessive flow rates, lowering the pressure at each stage.
Storz is a type of hose coupling invented by Carl August Guido Storz in 1882 and patented in Switzerland in 1890, and patented in the U.S. in 1893 that connects using interlocking hooks and flanges. It was first specified in standard FEN 301-316, and has been used by German fire brigades since 1933. Amongst other uses, it has been widely employed on fire hoses in firefighting applications. It is the standard coupling on fire hoses in Portugal, Denmark, Slovenia, Germany, Austria, Switzerland, Sweden, the Netherlands, Poland, Czechia, Israel, Croatia, Serbia, Bosnia & Herzegovina, Macedonia, Montenegro and Greece. It is also one of the standard couplings on fire hoses in Australia and the United States.
Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses, tubes, or pipes.
An air line is a tube, or hose, that contains and carries a compressed air supply. In industrial usage, this may be used to inflate car or bicycle tyres or power tools worked by compressed air, for breathing apparatus in hazardous environments and to operate many other pneumatic systems.
This is a glossary of firefighting equipment.
A street elbow is a type of plumbing or piping fitting intended to join a piece of pipe and another fitting at an angle. The difference between a street elbow and a regular elbow is the gender of its two connections.
A hose coupling is a connector on the end of a hose to connect it with another hose or with a tap or a hose appliance, such as an irrigation sprinkler. It is usually made of steel, brass, stainless steel, aluminium or plastic.
A 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 (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.
A fitting or adapter is used in pipe systems to connect sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of fluids such as water for potatory, irrigational, sanitary, and refrigerative purposes, gas, petroleum, liquid waste, or any other liquid or gaseous substances required in domestic or commercial environments, within a system of pipes or tubes, connected by various methods, as dictated by the material of which these are made, the material being conveyed, and the particular environmental context in which they will be used, such as soldering, mortaring, caulking, plastic welding, welding, friction fittings, threaded fittings, and compression fittings.
A pressure regulator is a valve that controls the pressure of a fluid to a desired value, using negative feedback from the controlled pressure. Regulators are used for gases and liquids, and can be an integral device with a pressure setting, a restrictor and a sensor all in the one body, or consist of a separate pressure sensor, controller and flow valve.
The breathing performance of regulators is a measure of the ability of a breathing gas regulator to meet the demands placed on it at varying ambient pressures and temperatures, and under varying breathing loads, for the range of breathing gases it may be expected to deliver. Performance is an important factor in design and selection of breathing regulators for any application, but particularly for underwater diving, as the range of ambient operating pressures and temperatures, and variety of breathing gases is broader in this application. A diving regulator is a device that reduces the high pressure in a diving cylinder or surface supply hose to the same pressure as the diver's surroundings. It is desirable that breathing from a regulator requires low effort even when supplying large amounts of breathing gas as this is commonly the limiting factor for underwater exertion, and can be critical during diving emergencies. It is also preferable that the gas is delivered smoothly without any sudden changes in resistance while inhaling or exhaling, and that the regulator does not lock up and either fail to supply gas or free-flow. Although these factors may be judged subjectively, it is convenient to have standards by which the many different types and manufactures of regulators may be objectively compared.
The Scott Air-Pak SCBA is an open-circuit, self-contained breathing apparatus designed to meet the National Fire Protection Association (NFPA) Standard 1981. All components, excluding the air cylinder, were designed and manufactured by Scott Safety. Formerly a division of Tyco International, Ltd., Scott Safety was sold to 3M in 2017.
For hoses and piping, a quick connect fitting, also called a push fitting, is a coupling used to provide a fast, make-or-break connection of gas or liquid transfer lines. Operated by hand, quick connect fittings replace threaded or flanged connections, which require wrenches. When equipped with self-sealing valves, quick connect fittings will, upon disconnection, automatically contain any fluid in the line.
Dixon Valve & Coupling Company, LLC is a manufacturer and supplier of hose fittings and accessories. The company, often referred to as just Dixon, offers products for fire protection, food processing, dairy processing, beverage and brewery operations, industrial manufacturing, mining, construction, chemical processing, petroleum processing and refining, oilfields, mobile tankers and agricultural operations. Dixon Valve, which was founded by H. W. Goodall in 1916, maintains manufacturing, warehouse, sales or service facilities in eleven U.S. states. It also has sales and service offices on five continents. Its international headquarters are in Chestertown, Maryland (USA).
A cam and groove coupling, also called a camlock fitting, is a form of hose coupling. This kind of coupling is popular because it is a simple and reliable means of connecting and disconnecting hoses quickly and without tools.
The mechanism of diving regulators is the arrangement of components and function of gas pressure regulators used in the systems which supply breathing gases for underwater diving. Both free-flow and demand regulators use mechanical feedback of the downstream pressure to control the opening of a valve which controls gas flow from the upstream, high-pressure side, to the downstream, low-pressure side of each stage. Flow capacity must be sufficient to allow the downstream pressure to be maintained at maximum demand, and sensitivity must be appropriate to deliver maximum required flow rate with a small variation in downstream pressure, and for a large variation in supply pressure, without instability of flow. Open circuit scuba regulators must also deliver against a variable ambient pressure. They must be robust and reliable, as they are life-support equipment which must function in the relatively hostile seawater environment, and the human interface must be comfortable over periods of several hours.