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Air admittance valves (AAVs, or commonly referred to in the UK as Durgo valves and in the US as Studor vents and Sure-Vent®) are negative-pressure-activated, one-way mechanical valves, used in a plumbing or drainage venting system to eliminate the need for conventional pipe venting and roof penetrations.
The valves are normally installed with the first installation of a system, then remain in place for the life of the system. They are generally reliable and require no maintenance. If they do eventually fail, they are replaced rather than repaired. A leaking valve commonly shows a dribble of water from the air vent, or stains of rust or limescale.
An air-operated valve, also known as a pneumatic valve, is a type of power-operated pipe valve that uses air pressure to perform a function similar to a solenoid. As air pressure is increased, the compressed air starts to push against the piston or diaphragm walls which causes the valve to actuate. Whether the valve opens or closes depends on ...
In domestic applications, traps are typically U, S, Q, or J-shaped pipe located below or within a plumbing fixture.An S-shaped trap is also known as an S-bend.It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880.
In the 1980s, many U.S. production engine remanufacturers began reaming valve guides, rather than replacing them, as part of their remanufacturing process. They found that by reaming all the valve guides in a head to one standard size (typically 0.008 in. diametrically oversized), and installing remanufactured engine valves having stems that are also oversized, a typical engine head can be ...
Another application of admittance in geophysics takes atmospheric pressure as the input and measures changes in the gravitational field as the output. In such case admittance is measured in μGal/mbar. These units convert according to 1 Gal = 0.01 m/s 2 and 1 bar = 100 kPa, so in SI units the measurement would be in units of;
Following on the success of the Molteno implant, several varieties of device have been developed from the original, the Baerveldt tube shunt, or the valved implants, such as the Ahmed glaucoma valve implant and the later generation pressure ridge Molteno implants. These are indicated for glaucoma patients not responding to maximal medical ...