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A
Actuator: Device used to operate a valve using
electric, pneumatic or hydraulic means. Often used
for remote control or sequencing of valve
operations.
Alloy steel: A steel consisting primarily of
iron with some percentage of one or more other
elements such as chromium, nickel, manganese, or
vanadium deliberately added to enhance its
properties.
Ambient temperature: The prevailing temperature
of the environment immediately surrounding an object
generally considered to be -20° F to +100° F.
Austenitic stainless steel: The common
stainless steel, where the primary micro structure
is austenite and the composition primarily iron but
also includes both chromium and nickel. The steels
are designated as 300 series such as 304, 316, CF8M,
etc. |
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B
Bevel gear operator: Device facilitating
operation of a gate or globe valve by means of a set
of bevel gears having the axis of the pinion gear at
right angles to that of the larger ring gear. The
reduction ratio of this gear set determines the
multiplication of torque achieved.
Back seat: A shoulder on the stem of a gate
or globe valve which seals against a mating surface
inside the bonnet to prevent leakage of media
through the bonnet stuffing box when the valve is
fully opened.
Ball: The closure element of a ball valve.
Ball valve: A valve using a spherical closure
element which is rotated through 90º to open and
close the valve.
Body: The principle pressure containing part
of a valve in which the closure element and seats
are located.
Bolted bonnet: A bonnet which is
connected to a valve body with bolts or studs and
nuts.
Bolted construction: Describes a valve
construction in which the pressure shell elements
(such as body and closures of a trunnion ball valve)
are bolted together and so can be taken apart and
repaired in the field.
Bonnet: The top part of a valve, attached to
the body, which contains the packing gland, guides
the stem, and adapts to extensions or operators.
Bore (or port): The inside diameter of the
smallest opening through a valve, e. g., inside
diameter of a seat ring, diameter of hole through
ball in a ball valve.
Butt weld end (BWE): The end connection of a
valve suitably prepared for butt welding to a
connecting pipe. |
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C
Carbon steel (CS): Iron containing carbon in
the form of carbides, about 0.1 to 0.3 percent
carbon with no other alloying elements other than
the sulfur, phosphorus, and other elements present
in almost all steels.
Cast iron: The common term for cast gray iron
or iron containing flake carbon in the range of _%
to 2 _%. Cast iron is brittle, exhibiting very
little ductility before fracturing.
Casting: A product or the act of producing a
product made by pouring molten metal into a mold and
allowing it to solidify, thus taking the shape of
the mold.
Charpy impact test: A destructive mechanical
test conducted on a precisely machined coupon of
steel to be tested. The coupon is clamped in a
special machine and subjected to lateral hammer
blow. The test provides a relative measure of the
toughness of the steel or its resistance to shock or
impact loads and is usually required for material
used in low temperature applications.
Check valve: A one-directional valve which is
opened by the fluid flow in one direction and closed
automatically when the flow stops or is reversed.
Clapper: The hinged closure element of a
swing check valve.
Closure: The ends of a bolted construction
ball valve, bolted to the body, which often retain
the seat rings.
Closure element: The moving
part of a valve, positioned in the flow stream,
which controls the flow through the valve, e. g.,
wedge, plug, clapper, ball.
Cv: Flow coefficient expressed as the number
of gallons of water that would flow through an
opening, such as a valve port, in 1 minute under a
differential pressure of 1 psi.
CWP: Cold working pressure - the maximum
allowable pressure under non-shock conditions at
ambient temperature ( -20° F to +100° F). |
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D
Dezincification: A form of pitting corrosion
which attacks certain zinc bearing copper-based
alloys, often called "yellow brasses", when in
contact with sea water or fresh water that is high
in oxygen and carbon dioxide. (ASTM B61 and B62 are
"red brasses" and not susceptible to
dezincification.).
Double block and bleed: The capability of a
valve under pressure to obtain a seal across both
the upstream and downstream seat rings and to have
its body cavity bled down to atmospheric pressure.
Drain plug: A fitting at the bottom of a
valve, the removal of which permits draining and
flushing the body cavity. |
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E
Elastomer: A natural or synthetic elastic
material, often used for o-ring seals. Typical
materials are viton, buna-n, EPDM (ethylene
propylene dimonomer), etc.
End connection: The type of connection
supplied on the ends of a valve which allows it to
be connected to piping - may be weld end, flanged
end, threaded or socket weld. |
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F
Face-to-face: The overall dimension from the
inlet face of a valve to the outlet face of a valve
(one end to another) allowing valves of the same
size and pressure class to be mutually
interchangeable, regardless of manufacturer.
Facing: The finish of the gasket contact
surface of a flange.
Fitting: Any component, other than valves,
used with pipe as part of the pressure system and
normally referring to items covered by a national
standard.
Flat Face (FF): A flange surface in which the
gasket sealing area is the entire surface from the
ID to the outside edge. Usually used for class 125
cast iron valves.
Fire safe: A valve design that is capable of
passing a fire test with specified limits on leakage
to the atmosphere and downstream after being closed
subsequent to fire exposure.
Floating ball: A ball valve design in which
the ball is not rigidly held on its rotational axis
and so is free to float between the seat rings.
Float valve: A valve which automatically
opens or closes as the level of a liquid changes.
The valve is operated mechanically by a float which
rests on the top of the liquid.
Forging: A metalworking process that involves
hammering or squeezing, with or without a die, at
hot working temperatures to form a specific shape.
Full bore (full port): Describes a valve in
which the bore (port) is nominally equal to the bore
of the connecting pipe.
Full penetration weld: Describes the type of
weld wherein the weld metal extends through the
complete thickness of the parts being joined. |
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G
Gasket: A component whose purpose is to seal
a joint between two larger components, softer than
the surfaces of the joint being sealed and usually
squeezed by means of bolting to effect the seal.
Gate: The closure element of a gate valve
(sometimes called wedge or disc).
Gate valve: A straight through pattern valve
in which closure element is a wedge situated between
two fixed seating surfaces, with means to move it in
or out of the flow stream in a direction
perpendicular to the pipeline axis. Used as a block
valve, or on-off valve.
Gland or gland bushing: The part of the valve
which retains or compresses the stem packing in a
stuffing box.
Gland follower or gland flange: The component
used to hold down or retain the gland in the
stuffing box.
Globe valve: A valve whose closure element is
a flat disc or conical plug sealing on a seat which
is usually parallel to the flow axis. Can be used
for throttling services.
Graphite: Flexible carbon material used to
make gaskets and packing. The gaskets may be flat
graphite sheet or have metal inserts for added
strength. The packing is a combination of lattice
braided rings used as anti-extrusion or wiper rings
and die-formed rings which are compressed to effect
the seal.
Grease fitting: A device which permits
injection of grease into a bearing surface. |
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H
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.
Hard facing: A surface preparation in which
an alloy is deposited on a metal surface usually by
weld overlay to increase resistance to abrasion and
or corrosion.
Heat analysis: A chemical analysis conducted
by a foundry immediately prior to pouring which
measures the exact chemical composition of a
particular batch of molten metal.
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.
Hot tears: A defect occurring in castings
caused where partially solidified or weak, newly
solidified sections are subjected to a pull
resulting from the contraction of thinner parts that
have solidified earlier. A hot tear is an
intergranular failure.
Huey test: A corrosion resistance test for
stainless steels, most useful for predicting
resistance to intergranular corrosion.
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. |
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I
IBBM: Iron body, bronze mounted - common term
for valves with cast iron body and bonnet and bronze
trim (seating surfaces, stem, bushings).
ID: The measurement of the inside diameter of
a circular part.
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. |
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L
Lever: A handle type operating device for
quarter-turn valves.
Liquid penetrant inspection: A nondestructive
method of detecting the presence of surface cracks
and imperfections through use of a special red dye.
Abbreviated as LPI or PT.
Locking device: Any valve attachment whose
purpose is to prevent the operation of the valve by
unauthorized persons. |
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M
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. Material Test Reports Certificates
provided by the steel manufacturer indicating the
chemical analysis and mechanical properties of a
specific batch of steel traced by sequentially
assigned heat numbers or codes.
Mold: A hollow cavity, frequently in packed
sand, for giving a desired shape to a material in a
molten or plastic shape. |
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N
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. |
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O
OD: The measurement of the outside diameter
of a circular part.
O-ring: An elastomeric or synthetic seal ring
of circular cross section.
OS&Y: Outside Screw & Yoke - A valve design
in which the stem threads are above the packing
gland or outside the valve body and there is a yoke
to support the top or outer end of the stem. Packing
The deformable sealing material inserted into a
valve stuffing box which when compressed by the
gland provides a tight seal about the stem. |
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P
Pattern: A duplicate made of wood or metal of
a part to be cast. Used to form the mold into which
the molten metal is poured.
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.
Plastics: A broad classification covering a
variety of non-metallic, synthetic or organic
materials capable of being molded or formed into
desired shapes. Typical materials include nylons and
tetrafluoroethylenes such as Teflon.
PMI: Positive material identification - a
method for cross checking the identity of a piece of
material, often using a portable spectrometer,
usually with x-rays (TN 9266, nuclear analyzer) or a
welding arc (Arc Met 900, optical spectrometer).
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.
Position indicator: Any external device which
visually indicates the open and closed position of
valve.
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.
Pressure-Temperature Ratings: The maximum
allowable working pressures at specified
temperatures. For steel valves, the ratings are
defined by "classes" and found in ASME B16.34. For
iron and bronze valves, the ratings are defined in
the applicable MSS specifications.
Product Analysis: The chemical analysis of a
material done on a finished component to show
compliance with the material specifications. Usually
has tolerances defined for each element to allow for
differences in the completed product compared to the
molten metal.
PSI: Pounds per square inch - the force per
unit area exerted against a resisting body. |
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R
Ra: Abbreviation for "arithmetic average
roughness height" - the measure of the roughness of
a surface expressed in microinches. The higher the
number, the rougher the surface. Used to designated
the desired surface finish for end flange raised
faces.
Radiographic inspection: A nondestructive
inspection method using x-rays to locate internal
flaws in castings, fabricated parts and welds.
Abbreviated as RT.
Raised faced (RF): The raised area of a
flange face which is the gasket sealing surface
between mating flanges. Defined in ASME B16.5. Class
150 and 300 valves have 0.06" RF and Classes 600 and
up have a 0.25" RF.
Reduced port: A valve port opening that is
smaller than the line size or the valve end
connection size.
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.
Rim pull: The force required at the edge of
the handwheel to generate the required torque at the
center of the handwheel.
RS: Rising stem - A valve stem with threads
arranged so that as the stem turns, the threads
engage a stationary threaded area and lift the stem
along with the closure element attached to it.
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S
Schedule: A system for indicating the wall thickness
of pipe. The higher the schedule number, the thicker
the wall for a certain pipe size.
Seal weld: A weld
that does not contribute anything to the mechanical
integrity of an assembly, but is made purely to seal
or prevent leakage from, for instance, a threaded
joint.
Seat: The part of a valve against which the
closure element effects shut-off.
Self-relieving:
The process by which excessive internal body cavity
pressure is automatically relieved either into the
upstream or downstream line - generally found in
ball valves.
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.
Sour gas:
Natural gas containing significant amounts of
hydrogen sulfide (H2S). Requires special material
treatments to avoid failures from sulfide corrosion
cracking.
Specification: A document that defines the
requirements that a finished product must conform to
- may include chemical and mechanical properties,
tolerances, marking, shipping, etc.
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.
Square operating nut: A nut, usually 2" x 2", which
is attached to a valve stem or the pinion shaft of a
gear operator allowing use of wrenches to quickly
operate the valve.
Stainless steel (SS): Any of a
number of types of iron alloy with chrome, nickel,
or other elements that does not oxidize in free air.
Stem: The rod or shaft transmitting motion from an
operator (handwheel or gear operator) to the closure
element of the valve.
Stem nut (yoke nut): The
threaded nut that surrounds a reciprocating valve
stem and causes the stem to move when the nut is
rotated.
Stud: A bolt, threaded on both ends, often
used in bolting together bodies and bonnets or
bodies and closures.
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. |
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T
Tensile strength: The highest
tensile stress that a material can withstand before
failure or rupture occurs -the force being applied
in a direction tending to elongate the material.
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.
Throttling: The
intentional restriction of flow by partially closing
or opening a valve.
Thrust: The net force applied to
a part in a particular direction - e.g., on the end
of a valve stem.
Torque: The rotational force
imposed on or through a shaft, usually expressed in
foot-pounds.
Trim: Commonly refers to the valve’s
working parts and to their materials. Usually
includes seat ring sealing surfaces, closure element
sealing surfaces, stems, and back seats. Trim
numbers which specify the materials are defined in
API 600 and API 602.
Trunnion: The part of a ball
valve which holds the ball on a fixed vertical axis
and about which the ball turns.
Turns to operate:
The number of complete revolutions of a handwheel or
the pinion shaft of a gear operator required to
stroke a valve from fully open to fully closed or
vice versa. |
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U
Ultrasonic inspection: An inspection
procedure using high frequency sound waves to detect
wall thickness or flaws throughout the thickness of
metal parts. Abbreviated as UT.
Union bonnet: A type
of valve construction in which the bonnet is held on
by a union nut with threads on the body. |
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V
Valve: A
device used to control the flow of fluid contained
in a pipe line. |
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W
WOG: Water-oil-gas - a rating
designation generally used for small valves chiefly
in low ratings. Indicates maximum working pressure
at ambient + 32° F to +100º F. Also called Nonshock
Rating.
Working pressure: The pressure (pounds per
square inch) at which a valve is designed to
operate.
Wall thickness: The thickness of the wall
of the pressure vessel or valve. For steel valves,
minimum thickness requirements are defined in ASME
B16.34, API 600, and API 602.
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. |
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Y
Yield
strength: The limiting stress beyond which a
material will sustain permanent deformation.
Yoke:
The part of gate or globe valve which acts as a
bracket to support the top or outer end of the stem
and stem bearing |
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