API 594:2004 pdf download
API 594:2004 pdf download.Check Valves: Flanged, Lug, Waferand Butt-welding.
The total cross-sectional area of the bolts shall be in accordance with the requirements of ASMF. 916.34.
4.1.16 When valve design utilites a stem that extends beyond the pressure boundary, it shall be provided with a means so that, in (he event of a structural failure of stem-to- closure attachment items, the stem will not be ejected through the pressure boundary while the valve is under pressure.
4.2 PLATES AND DISC
Valves are cla.ssihed as follows:
a. A single-plate valve has a plate or disc that closes the valve when flow reversal or gravity forces the plate or disc against the valve-body seat. This closure may be aided by the use of springs or other devices,
lx A dual-plate valve has plates that close the valve with the assistance of one or more springs, when flow reversal forces the plates against the valve-body seat.
c. For Type ‘A’ single-plate valves and ‘Tpe ‘B’ valves, when a nut is used to assemble the disc or plate to the hinge arm, the nut shall he secured to prevent separation: the use of a single tack weld, lock washer or lock nut are not acceptable means.
4.3 SEATING SURFACES
4.3.1 The body and plate or disc seating surfaces may he of deposited weld metal, integral metal, mechanically retained metal, or a resilient material. On flpe ‘A’ single-plate valves and Type ‘B’ valves, a resilient seal ring may be titted either to the hody or plate seat as specified by the purchaser. The ring shall he designed to give a full metal to metal seal if the resilient seal is inoperative or removed.
4.3.2 %tding is not pennined on cast iron or ductile iron.
4.3.3 Brasing is pemsined on cast iron and ductile iron only for attaching seating surfaces to the body or the plate and only if agreed to by the purchaser and the manufacturer. Fur- mace bra.ting is the only type otbraiing permitted and may be used only if the parts are heated under closely controlled conditions, in a uniform manner, and to a temperature no higher than the losver critical temperature of the base material. Cool’ ing shall be in the furnace or in still air.
4.4 EXTERNAL BOLTS AND ThREADED HOLES
4.4,1 Bolts and threaded holes with a diameter I in. or smaller shall have coarse (UNC) threads. Those larger than I in. diameter shall he of the eight-thread series (8 UN).
Bolt threads shall he Class 2A. and nut threads shall be class 28. Threads shall conform to A-SM F B 1.1.
4.4.2 For bolts I in. diameter or smaller, threaded body- flange bolt holes shall be drilled and tapped acconling to the requirement.s for coarse thread senes Class 2B in ASME H I I For boh larger than I in. diameter, such holes shall be drilled and tapped according to the requirements for eight- thread series Class 2B in ASME HI_I.
4.4.3 For Type ‘W salves, cover flange bolts shall be continuously threaded stud bolts with heavy. semilinished hexagon nuts conforming to the requirenient’. of ASMF HIW2.2. Hex bolts or cap screw’. conforming to ASME B 18.2.1 may also he used for NPS 2l2 and smaller valve,., lies huh’. and cap screws shall he suitable 11w etcmaI wrenching only.
4.5 FLOW INDICATiON
The valve husk shall be furnished with a clearly visible ca.st. lorged. machined-in. or die-slamped arrow to indicate the direction of flow through the silvc.
4.6 GASKET SURFACE
Fasteners in the flange seating surface shall be recessed to or below the flange gasket level. Interruptions in the sealing area of a centered ASME B 16.20 spiral wound gasket for valve sites NPS 6 and brgcr shall not exceed the liinitidions given in Figure 6. The peniiissihlc surface intcmlprions on smaller size salves shall be as agreed between purchaser and manufacturer kit shall not exceed S0’k of the gasket seating width.
Note: The degree of inremiption may affect the ‘.eaINhty of a spiralsssund gasket.
5 Material
5.1 BODY AND COVER
The body of Type A sakes and the body and coser of Type B valves shall he made of a material conforming to a purchaser selected material specification listed in the applicable ASMII standard as referenced in 3.2.
