Valve and Glossary (3)

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 (90^o) 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.

Safety-relief valve: A pressure-relief valve characterized by rapid opening pop action, or by opening generally proportional to the increase in pressure over the opening pressure.

Safety valve: A pressure-relief valve actuated by inlet static pressure and characterized by rapid opening or pop action.

Seat: The portion of the valve against which the closure member presses to effect shutoff.

Seat ring: A separate piece inserted in the valve body to form a seat against which the valve-closure member engages to effect shut-off.

Set pressure: The inlet static pressure of the system at which a relief valve starts to open, or safety valve pops open.

Short pattern valve: A valve that has face-to-face or end-to-end dimension for a short pattern design according to standard ASME B16.10.

Steam working pressure (SWP): The maximum rated or working pressure corresponding to the steam temperature that must not be exceeded when valve is used in steam service. It is marked with S, SP, or SWP on the valve.

Stroke: The amount of travel the valve-closure member is capable of from a fully closed position to a fully open position or vice versa. In linear-motion valves it is expressed in in (mm) and in degrees, 0 to 90, for rotary motion valves.

Throttling: The process of regulating the fluid flow rate or pressure by controlling the position of the closure member between the full-open and full-closed positions.

Trim: Functional parts of a valve which are exposed to the line fluid. Usually refers to the stem, closure member and, seating surfaces. The removable or replaceable valve metal internal parts that come in contact with the flow medium are collectively known as valve trim. Valve parts such as body, bonnet, yoke, and similar items are not considered trim.

Venturi port: A valve bore or port that is substantially smaller than the full port, approximately 40 to 50 percent of full port. It is normally found in plug valves.

Wafer body: A valve body that has a short face-to-face dimension in relation to pipeline diameter and is designed to be installed between two flanges using special length studs and nuts.

Wedge: A gate valve–closure member with inclined sealing surfaces which come in contact with valve-seating surfaces that are inclined to the stem centerline. Wedge is available in solid, split, and flex designs.

Yoke: That part of the valve assembly used to position the stem nut or to mount the valve actuator.

Yoke bushing, yoke nut: Yoke nut, yoke bushing, or stem nut is the valve part that is held in a recess at the top of the yoke through which the stem passes. It converts rotary-actuating effort into thrust on the valve stem.


Weldless Stainless Steel Ball Valve and Spigot