API STD 609-2009 pdf download.Butterfly Valves: Double-flanged, Lug- and Wafer-type.
3 Pressure-temperature Ratings 3.1 Valve Rating Category A valves shall have a CWP rating that is the lesser of its shell rating, seat rating, or differential pressure rating. 3.2 Shell Rating 3.2.1 Category A valve bodies and related pressure boundary elements shall have the CWP rating assigned by the manufacturer. 3.2.2 Category B valve bodies and related pressure boundary elements shall have the pressure-temperature rating as listed in one of the following standards according to the valve’s body material: a) for ductile iron, ASME B16.42; b) for cast copper alloys, ASME B16.24; c) for steel, nickel alloy, or special alloy material, ASME B16.34 (standard class). 3.3 Seat Rating 3.3.1 For Category B valves, the valve seat ratings for polytetrafluoroethylene (PTFE) and reinforced polytetrafluoroethylene (RPTFE) shall be at least equal to those listed in Table 1. For seating materials not listed in Table 1, seat ratings shall be established by the manufacturer. 3.3.2 Valves furnished with internal liners, encapsulation, resilient seating materials, or a combination of these features shall have pressure-temperature limits conforming to the valve manufacturer’s published specifications. Temperature limits shall be marked on the nameplate as required in 7.1.
4 Design 4.1 General 4.1.1 Category B Valves Valves manufactured in accordance with this standard shall meet the requirements of ASME B16.34 for standard class and any additional requirements as specified in this standard. For materials not listed in ASME B16.34, the applicable requirements and design rules of ASME B16.34 shall be used. In the event of a conflict between ASME B16.34 and this standard, this standard shall prevail. 4.1.2 Fire-tested Valves If the purchaser specifies fire-tested valves, the valves shall be certified to have been tested to, and met, all of the performance requirements of API 607. Supporting documentation shall be made available to the purchaser upon request. 4.1.3 Lockable Device When specified in the purchase order, valves shall be furnished with a lockable device that accepts a purchaser- supplied lock that enables the valve to be locked in both the open and closed positions. The lockable device shall be designed such that a lock with a 8 mm ( 5 / 16 in.) diameter shank, not more than 100 mm (4 in.) long, can be inserted directly through appropriate holes and locked. Provisions for a lockable device are permitted even when it is not specified in the purchase order. 4.1.4 Disc Position Indication The indication of the position of the disc shall be integral with the valve shaft and shall be aligned with the valve disc. The indication may be accomplished by a mark on the shaft or by a shaft shape. The design shall ensure that a valve (and/or operator) cannot be assembled to falsely indicate the valve’s open and closed positions.
4.1.5 Shaft-to-lever Connections Shaft-to-lever connections shall be designed so that the lever always correctly indicates the disc position. The lever- type handle shall be mounted so that the handle is in parallel with the valve disc. 4.2 Body 4.2.1 The minimum body-wall thickness shall comply with the applicable ASME B16 standard listed in Section 2 based on the body material. If the applicable standard covers fittings for a particular material, the valve minimum wall thickness shall be as specified for fittings. The valve design shall be structurally suitable for its stated pressure and temperature limits, taking into account that localized thinning may be necessary between the shaft bore in the body and the adjacent bolt holes. Such sections shall be designed in accordance with the requirements of ASME B16.34. 4.2.2 When a wafer-type valve is installed between piping flanges and the disc is in the closed position, the valve shall be self-centering, that is, designed to center itself within the bolt circle by using the valve’s outside diameter, or by means of integral or attached alignment devices. 4.2.3 End flanges for double-flanged valves shall be integrally cast or forged with the body; however, flanges may be attached by full-penetration butt-welding if agreed to by the purchaser. End flanges attached by welding shall conform to ASME B16.5 and have butt-welding ends for use without backing rings. Welds shall conform to ASME B31.3, as shall qualifications for the welding procedure and the welder or welding operator. The finished weld thickness shall not be less than the minimum body-wall thickness. 4.2.4 If drain or bypass connections are specified by the purchaser, they shall conform to ASME B16.34 or MSS SP- 45, as applicable.