ActuatorDevice used to operate a valve using electric, pneumatic or hydraulic means. Often used for remote control or sequencing of valve operations.Alloy steelA 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 temperatureThe prevailing temperature of the environment immediately surrounding an object - generally considered to be -20 F to +100 F.Austenitic stainless steelThe common stainless steel, where the primary microstructure 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.Bevel gear operatorDevice 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 seatA 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.BallThe closure element of a ball valve.Ball valveA valve using a spherical closure element which is rotated through 90 to open and close the valve.BodyThe principle pressure containing part of a valve in which the closure element and seats are located.Bolted bonnetA bonnet which is connected to a valve body with bolts or studs and nuts.Bolted constructionDescribes 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.BonnetThe 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 endThe end connection of a valve suitably prepared for butt welding to a connecting pipe. Carbon steelIron 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 ironThe 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.CastingA 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 testA 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 valveA one-directional valve which is opened by the fluid flow in one direction and closed automatically when the flow stops or is reversed.ClapperThe hinged closure element of a swing check valve.ClassA pressure rating expressed as a dimensionless number. The class rating charts give actual pounds per square inch maximum allowable pressure at a given temperature.ClosureThe ends of a bolted construction ball valve, bolted to the body, which often contain the seat rings.Closure elementThe moving part of a valve, positioned in the flow stream, which controls the flow through the valve, e.g., wedge, plug, clapper, ball.CvFlow 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.CWPCold working pressure - the maximum allowable pressure under non-shock conditions at ambient temperature ( -20 F to +100 F).DezincificationA 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 bleedThe 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 plugA fitting at the bottom of a valve, the removal of which permits draining and flushing the body cavity.ElastomerA natural or synthetic elastic material, often used for o-ring seals. Typical materials are viton, buna-n, EPDM (ethylene propylene dimonomer), etc.Emergency seat sealA fitting on the valve body through which sealant can be injected to effect a seat seal in an