MISL Energy

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Acme thread:   A flat-topped trapezoidal shaped thread used for power transmission rather than fastening.

Actuator:     A mechnical device that uses an energy source other than manual power to operate a valve; also called an operator.

Adjusting rings:   The parts of a safety vavle or safety relief valve used to control disc lift and blowdown.

Ambient temperature:    The temperature of the environment surrounding a valve, normally ranging from -20degF to 100degF

Angle valve:   A globe valve whose ends are perpendicular to each other, rather than parallel; one end is directly below the disc.

Backseat:     An auxiliary seat in the bonnet to enable packing replacement while the valve is under pressure.

Ball:    The spherical flow control element of a ball valve or ball check valve.

Ball check valve:     A lift check vavle whose flow control element is a solid ball.

Ball Valve:    A type of valve whose flow control element is a ball with a circular passage through it and that rotates 90 deg from open to closed.

Bellows seal valve:   A gate or globe valve that uses a cylindrical metal bellows to hermetically seal the valve against stem leakage.

Bevel gear operator:    A gear operator that uses a bevel geat set.

Block-and-bleed:    An operation done with a double seated valve having a between-seats drain. When the valve is closed (blocked) the drain is opened, allowing the fluid trapped between the seats to drain (bleed) away.

Blowdown:   The difference between the set (opening) pressure and the disc reseating pressure of a pressure relief valve, which is usually expressed as a percentage of the set pressure.

Body:     The part of a valve that houses the flow control element, contains seating surface, retains fluid pressure, and in most valve designs, has ends for attaching to connecting pipe.

Bolted bonnet:    A body-bonnet joint design in which the bonnet is fastened to the body using studs or bolts and nuts; it uses a gasket to provide joint sealing.

Bonnet:   The part of a gate valve, globe valve, or diaphragm valve that is fastened to the body to complete the pressure-retaining shell; it has on opening for the stem to pass through, and it usually contains a stuffing box. Depending on the valve stem design, it may also have a yoke attached.

Bore:   The dia meter of the smallest opening through a valve; also called a port.

Bubble tight:    A phrase used to describe the tightness of valve seating surfaces. It derives from a seat tightness test in which compressed air is used for the test. with water on the downstream side of the seat so that leakage is detected by air bubbles. It is usually used in conjunction with soft-seated valves to indicate zero leakage.

Butt weld end:    A valve end machined to the proper dimensions to enable butt welding to connecting pipe.

Butterfly valve:    A valve whose flow control element is a disc with an axis perpendicular to flow and that rotates 90deg from open to closed.

Bypass:    A short pipeline, containing a sop valve, that is mounted on a valve to connect the inlet and the outlet and bypass the flow control element.