Ordliste

There are 16 entries in this glossary.
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Term Main definition
GALLING

A form of surface damage arising between sliding solids distinguished by macroscopic usually localized roughening and creation of protrusions above the original surface it often includes plastic flow or material transfer or both. The onset of galling usually requires that the contact pressure exceeds some threshold value. Galling can be a precursor to seizing or loss of function.

GALVANIC CORROSION

Corrosion associated with the current resulting from the electrical coupling of dissimilar materials (electrodes) in an electrolyte.

GAS

A compressible fluid such as air hydrogen nitrogen etc.

GAS OVER OIL ACTUATOR

For pipelines where high pressure gas is used to displace hydraulic fluid into the actuator.

GAS TESTING

Gas testing can be divided into 2 categories namely high- pressure and low-pressure gas testing. Both these tests are considered supplementary test requirements within the AP/ 60 specification. For the low pressure gas test nitrogen is most often used along with acceptance criteria based on ISO 5208. For the high pressure gas test the standard hydrostatics seat test required by AP/ 60 is carried out using an inert gas (usually helium) as the test medium.

GASKET

A seal or packing placed between mechanical joints (such as flanges) to prevent the escape of the flowing medium.

GATE

The closure element of a gate valve.

GATE VALVE

A straight-thru pattern valve whose closure element is a wedge or parallel-sided slab situated between two fixed seating surfaces with means to move it in or out of the flow stream in a direction perpendicular to the pipeline axis.

GAUGE (Pressure Gauge)

An instrument usually with a threaded connection for measuring and indicating the pressure in a piping system at the point at which it is connected.

GLAND OR GLAND BUSHING

That part of a valve which retains or compresses the stem packing in a stuffing box (where used) or retains a stem 0-Ring lip seal or stem 0-Ring bushing. Sometimes manually adjustable. See Packing and Stuffing Box.

GLAND PLATE

The plate in a valve which retains the gland bushing or stem seals and sometimes guides the stem.

GLASS TRANSISTION (Tg)

Temperature at which a viscous polymer loses its ability to flow or store energy becoming hard and brittle (like glass).

GLOBE VALVE

A valve whose closure element is a flat disc or conical plug sealing on a seat which is usually parallel to the flow axis. The tortuous flow path produces a relatively high pressure loss.

GMAW (Gas Metal Arc Welding)

In GMAW also known as metal inert gas (MIG) welding an electric arc is established between the workpiece and a consumable wire electrode. The arc continuously melts the wire as it is fed to the weld puddle. The weld metal is shielded from the atmosphere by a flow of an inert gas or gas mixture.

GO (Gear Operated)

The actuation of a valve through a gear set which multiplies the torque applied to the valve stem. See BGO and MGO.

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