Valve Terminology - III

Half stellited:

A valve is termed half stellited when only the seating surfaces of the valve seat(s) are hard faced with wear and corrosion-resistant material (Stellite or other such material).

Hard facing:

Application or deposit of hard, wear, and corrosion-resistant material on soft surfaces subject to wear.

Inside screw–nonrising stem (ISNRS):

Threads on the stem are inside the valve body. The valve disc travels up and down the stem threads when the stem is rotated. Stem does not rise.

Inside screw–rising stem (ISRS):

Threads on the stem are inside the valve body and exposed to the flow medium. The stem rises when it is rotated, thus opening the valve. Position of the stem indicates the position of the valve disc.

Iron body–bronze mounted (IBBM):

A valve having cast iron body and bronze trim.

Lantern ring:

A spacer ring used in the lantern ring type of packing chamber to permit lubrication of the packing, purging of the shaft or stem, or a leak-off system.

Leak-off connection:

A pipe or tube connected to a hole in the stuffing box at the level of lantern ring. It is used to collect leakage past a lower set of lantern ring–type of packing or to inject lubricant into the stuffing box.

Linear-flow characteristics:

A flow characteristic of the valve when the flow is directly proportional to the position of the flow control element.

Liner:

Lining of protective materials applied on the inside surfaces of valve body (or valve trim) to enhance resistance to corrosion, erosion, or contamination.

Nonreturn valve:

Stop-check valve, a check valve in which the closure member can be mechanically closed.

Nonrising stem:

Refer to Inside screw, nonrising stem (ISNRS).

Outside-screw-and-yoke (OS&Y):

A valve design in which the threaded portion of the stem is outside the pressure boundary of the valve. The valve bonnet has a yoke, which holds a nut through which the rotating stem rises as the valve is opened. The stem part inside the valve is smooth and is sealed so that stem threads are isolated from the flow medium.

Pilot operated pressure relief valve:

A pressure-relief valve in which the major relieving device is combined with and controlled by a self-actuated auxiliary pressure-relief valve.

Port:

See bore.

Power actuated pressure-relief valve:

A pressure-relief valve in which the major relieving device is combined and controlled by a device requiring an external source of energy.

Quarter-turn valve:

A valve whose closure member rotates approximately a quarter turn (90⁰) to move from full-open to full-closed position.

Reduced port:

Valve port smaller than the inside diameter of the end-connecting pipe. It is approximately equal to the inside diameter of the one pipe size smaller than the end size for gate valves, and 60 percent of full bore on ball valves.

Regular port:

A valve port smaller than the full bore, approximately 75 to 90 percent of full bore on ball valves and 60 to 70 percent on plug valves.

Relief valve:

A pressure-relief valve actuated by inlet static pressure and having a gradual lift generally proportional to the increase in pressure over the opening pressure (set pressure).

Rotary motion valve:

A valve that involves a quarter-turn motion to open or close the valve closure element.

Rupture disc:

A non-closing pressure-relief device actuated by inlet static pressure and designed to function by the bursting of a pressure-containing disc.