【正文】 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. TrunnionThe part of a ball valve which holds the ball on a fixed vertical axis and about which the ball turns. Turns to operateThe number of plete 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.Ultrasonic inspectionAn inspection procedure using high frequency sound waves to detect wall thickness or flaws throughout the thickness of metal parts. Abbreviated as UT.Union bonnetA type of valve construction in which the bonnet is held on by a union nut with threads on the body.ValveA device used to control the flow of fluid contained in a pipe line.WOGWateroilgas a rating designation generally used for small valves chiefly in low ratings. Indicates maximum working pressure at ambient + 32176。 F to +100176。 F. Also called Nonshock Rating. Working pressureThe pressure (pounds per square inch) at which a valve is designed to operate.Wall thicknessThe thickness of the wall of the pressure vessel or valve. For steel valves, minimum thickness requirements are defined in ASME , API 600, and API 602.Worm gearsA 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.Yield strengthThe limiting stress beyond which a material will sustain permanent deformation. YokeThe part of gate or globe valve which acts as a bracket to support the top or outer end of the stem and stem bearing.VALVE SPECIFICATIONSBelow is a listing of the basic specifications used in the design and manufacture of valves and fittings.American Petroleum InstituteAPI Q1 Specification for quality programsAPI 6D Specification for pipeline valvesAPI 6FA Fire test for valvesAPI 598 Valve inspection and testingAPI 600 Steel gate valves, flanged and buttwelding ends, bolted and pressure seal bonnetsAPI 602 Compact steel gate valves flanged, threaded, welding, and extended body endsAPI 607 Fire test for soft seated quarter turn valvesAPI 608 Metal ball valves flanged and butt welding endsAmerican Society of Mechanical Engineers/American National Standards InstituteASME/ANSI Valves flanged, threaded and welding endASME/ANSI Pipe flanges and flanged fittingsASME/ANSI Facetoface and endtoend dimensions of valvesASME/ANSI Forged fittings, socketwelding and threadedASME/ANSI Buttwelding endsASME/ANSI Large diameter steel flangesNote: This specification for flanges larger than 24 replaces MSS SP44 and API 605 with the designations of Series A (MSS SP44) and Series B (API 605).ASME Chemical plant and petroleum refinery pipingANSI Liquid petroleum transportation piping systemANSI Gas transmission and distribution piping systemManufacturers Standardization Society of the Valves and Fittings IndustryMSS SP25 Standard marking system for valves, fittings, flanges and unionsMSS SP55 Quality standard for steel castings for valves, flanges, and fittings, and other piping ponents visual methodMSS SP70 Cast iron gate valves, flanged and threaded endsMSS SP71 Cast iron swing check valves, flanged and threaded endsMSS SP79 Socketwelding reducer insertsMSS SP80 Bronze gate, globe, angle and check valvesMSS SP83 Class 3000 steel pipe unions, socketwelding and threadedMSS SP85 Cast iron globe and angle valves, flanged and threaded endsNational Association of Corrosion EngineersNACE MR0175 Standard material requirements for sulfide stress cracking resistant metallic materials for oilfield equipment.British Standards Institute BSI 1414 Steel wedge gate valves (flanged and butt welding ends) for the petroleum, petrochemical, and allied industriesBSI 1868 Steel check valves (flanged and butt welding ends) for the petroleum, petrochemical, and allied industriesBSI 1873 Steel globe and globe stop and check valves (flanged and butt welding ends) for the petroleum, petrochemical, and allied industriesBSI 5352 Steel wedge gate, globe and check valves 50 mm and smaller for the petroleum, petrochemical, and allied industriesInternational Organization for StandardizationISO 9001/9002 Quality system Model for Quality Assurance