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Hand wheel

A wheel-shaped valve operating device intended to be grasped with one or both hands which allows turning the valve stem or operator shaft to which it is attached.

Heat treatment

Describes any process or procedure by which the internal structure of steel is altered by heating to produce desired physical and mechanical characteristics.

Hot tap

A connection made to a pipeline while the line is under pressure or in service. A special procedure is required to make an opening in the pipe without leaking any of the line contents.

Hydrostatic test

A pressure test in which a valve is tested with water to detect leaks - may be a shell test or a seat closure test.

ISRS

Inside screw, rising stem - common term for any valve design in which the stem threads are exposed to the fluid below the packing and the stem rises up through the packing when the valve is opened.

Lever

A handle type operating device for quarter-turn valves.

Locking device

Any valve attachment whose purpose is to prevent the operation of the valve by unauthorized persons.

Magnetic particle inspection

A nondestructive method of detecting the presence of surface cracks and imperfections through use of fine iron particles in an electrical field. Abbreviated as MPI or MT.

Mold

A hollow cavity, frequently in packed sand, for giving a desired shape to a material in a molten or plastic shape

NPS

Nominal pipe size - dimensionless number used to indicate sizes of pressure pipe and valves - used interchangeably with valve size in inches.

NPT

National Pipe Taper - standard tapered thread for pressure pipe and components. Requirements defined in ASEM B1.20.1.

NRS

Non-rising stem - A gate valve having its stem threaded into the gate. As the stem turns the gate moves but the stem does not rise. Stem threads are exposed to the line fluid.

O-ring

An elastomeric or synthetic seal ring of circular cross section

Pinhole

Numerous small gas holes at the surface or just below the surface of castings, generally occurring in the thicker parts of the casting as a reduction in the solubility of gases in the metal as the metal cools.

Pinion shaft

The external input shaft of certain gear operators which drive the internal reduction gearing.

Pneumatic test

A test in which a valve is tested with air - usually a seat closure test.

Porosity

A defect found in castings or welds consisting of gas bubbles or voids in the solidified metal.

Pressure class

A pressure rating expressed as a dimensionless number. The class rating charts give actual pounds per square inch maximum allowable pressure at a given temperature.

Ring type joint (RTJ)

A flange connection using a specially shaped soft metal ring as a gasket. Generally used on high pressure valves. May be the body and bonnet connection and/or the end flange connection

Resilient seat

A valve seat containing a soft seal such as an o-ring or plastic to assure tight shut-off.

Shrinkage

Internal defect in castings that are internal voids, irregular in shape, caused by volume contraction during solidification. Can be caused by not maintaining a fluid channel to the riser during solidification.

Socket weld end (SWE)

The end connection of a valve suitably prepared for socket welding to a connecting pipe.

Spur gear

The simplest of gears - in a gear set, the pinion and ring gear are aligned on parallel shafts. Can be added to another gear operator to further increase the mechanical advantage afforded by the gear.

Stem

The rod or shaft transmitting motion from an operator (handwheel or gear operator) to the closure element of the valve.

Stem nut

The threaded nut that surrounds a reciprocating valve stem and causes the stem to move when the nut is rotated.

Stuffing box

The annular chamber provided around a valve stem in a sealing system into which deformable packing is placed. Sometimes called packing chamber.

Swing check valve

A check valve in which the closure element is a hinged clapper which swings or rotates about a supporting shaft

Tensile test

A destructive test performed on a specially machined specimen taken from material in its delivered condition to determine mechanical properties, such as tensile strength, yield strength, and percent elongation.

Torque

The rotational force imposed on or through a shaft, usually expressed in foot-pounds.

Trunnion

The part of a ball valve which holds the ball on a fixed vertical axis and about which the ball turns.

Union bonnet

A type of valve construction in which the bonnet is held on by a union nut with threads on the body.

Worm gears

A gear set in which the input shaft is offset from and perpendicular to the output shaft, and driving gear is very small and perpendicular to the driven gear. Worm gear operators are used on ball valves.

Yield strength

The limiting stress beyond which a material will sustain permanent deformation.

Malaysia Valves Supplier & Distributors - Encord Sdn Bhd