A–B–C–D–E–F–G–H–I–J–K–L–M–N–O–P–Q–R–S–T–U–V–W–X–Y
Backseat
A shoulder on the stem of a gate valve which seals against a mating surface inside the bonnet to permit replacement, under pressure of stem seals or packing.
Ball
The spherical closure element (obturator) of a ball valve.
Ball Valve
A valve which has a ball shaped component inside the body of the valve. The ball valve is rotated through to 90° (quarter turn) to open or close the valve. It is used to isolate or control the flow of oil or gas.
Barg
A metric unit of pressure. It is not a SI unit, but it is accepted for use with the SI. 1 bar = 14.504 psi = 0.1 MPa.
Barrier
A separating device to insulate or isolate electrical circuits. Also the separating device in gas/hydraulic systems.
BBL
An abbreviation for “barrel”. It is the name of several units of volume. One barrel of oil equals 42 US gallons, i.e. 158.99 liters or 34.97 UK gallons.
BDV (Blow Down Valve)
A small ball valve that is installed on the above ground end of an extended drain line. This valve also serves to vent body cavity pressure in the ‘’block and bleed” mode.
Beacon Indicator
A highly visible device to show open/closed valve status, usually incorporates limit switches.
Belleville Spring
A conical shaped disc spring called after its inventor Julian Belleville who patented the product in 1867. It is used in some valves to push the seats against the closure element. Also termed Belleville Washer.
Bending Moment
The mechanical load produced by a force applied to a part at right angles to its surface or axis. Its magnitude is the product of the force times the perpendicular distance to the point of restraint. Usually expressed in Nm (SI unit) or pound∙feet.
Bevel
An edge of a structure that is not perpendicular to the two adjacent surfaces. It is used to term weld end preparation
BGO (Bevel Gear Operated)
The actuation of a valve by means of a set a gear where the axes of the two shafts intersect and the tooth-bearing faces of the gears are conically shaped. The reduction ratio of this gear determines the torque ratio achieved. Mostly used on gate valves.
Bi-Directional Valve
Valve designed for blocking the fluid and can be installed with either of the flange ends in the upstream or downstream direction.
Bleed Valve
Connected to the valve body cavity used to release or bleed the fluid or gas.
Blind Flange
Flange with no centre bore, used to close off completely a flanged end or outlet connection.
Blister
Raised area on the surface of a molded product caused by the pressure of internal gases.
Block & Bleed
The capability of obtaining a seal across the upstream seat of a valve when the body pressure is bled off to atmosphere through blow down valve or vent port.
Body
The principal pressure containing part of a valve, in which the closure element and the seats are located.
Bolt
A fastener comprised of a screw and a nut.
Bolt Circle
The dimension of a circle of tapped or through holes on a valve top flange or actuator mounting plate for securing the two devices.
Bolted Bonnet
The top part of a valve joined to the body which guides the stem and adapts to extensions or operators.
Bolted Contruction
Describes a valve construction in which the pressure shell elements are bolted together and thus can be taken apart and repaired in the field.
Bolted Sets
Bolts or studs and nuts are sometimes supplied with flanged valves to install the valve between line flanges.
Bolted Bonnet
The top part of a valve joined to the body which guides the stem and adapts to extensions or operators.
Bolted Construction
Describes a valve construction in which the pressure shell elements are bolted together and thus can be taken apart and repaired in the field.
Bolting Sets
Bolts or studs and nuts are sometimes supplied with flanged valves to install the valve between line flanges.
Booster
A device to increase air pressure and volume usually between a low volume pilot supply and a large actuator cylinder.
Bore or Port
The inside diameter of the smallest opening through a valve. The diameter of the hole in the ball of a ball valve; the diameter of the hole in the gate of a gate valve; the inside diameter of seat rings.
Breakaway Thrust or Torque
Thrust or torque required for moving a valve from the fully closed position and under a pressure differential.
Breather
Permits air movement between atmosphere and the component in which it is fitted.
Brinell Hardness
Brinell hardness is determined by forcing a hard steel or carbide sphere of a specified diameter under a specified load into the surface of a material and measuring the diameter of the indentation left after the test. The Brinell hardness number or simply the Brinell number is obtained by dividing the load used in kilograms by the actual surface area of the indentation in square millimeters. The result is a pressure measurement, but the units are rarely stated. ASTM E10 is a standard test for determining the Brinell hardness of metallic materials. Can be converted to Rockwell B or C hardness by reference to conversion tables in ASTM E140
BRV (Body Relief Valve)
A relief valve installed on double-seated valves used in liquid service to provide for the relief of excess body pressure caused by thermal expansion.
BS Standard
Refers to British Standard. See www.bsigroup.com/
Bubble Tight Shut-Off
Describes the sealing capability of a valve. During gas pressure testing of a valve in the closed position, leakage past the seat is collected and bubbled through water. To qualify as “bubble tight”, no bubbles should be observed in a prescribed time span.
Bulk Modulus
The ratio of the hydrostatic pressure to the volume strain. It actually determines how much a material compresses under a given amount of external pressure. Expressed in stress units, e.g. GPa, ksi, etc. A representative value of the bulk modulus for steel is 160 GPa and for water is 2.2 GPa.
Buried Service
An application in which a valve is installed in lines which are buried below ground level.
Burst Pressure
That pressure at which rupture of a stressed element or pressure containing vessel takes place.
Butterfly Valve
A short face-to-face valve which has a movable obturator in the center of the flow stream and rotates 90° as the valve opens and closes.
Bypass
A system of pipes and valves permitting the diversion of flow or pressure around the main valve.