API 609 pdf download Butterfly Valves: Double Flanged, Lug- and Wafer-Type
3.3.1For Category B valves the valve seat ratings for PTFEand RPTFE shall be at least equal to those listed in Table 3.For seating materials not listed in Table 3 , seat ratings shall bcagreed upon by the purchaser and the manufacturer.
3.3.2Valves furnished with internal liners， encapsulation,resilient seating materials,or a combination of these featuresshall have pressure-temperature limits conforming to thevalve manufacturer’s published specifications. Temperaturelimits shall be marked on the nameplate as required in 7.1.
3.4DIFFERENTIAL PRESSURE RATING
A valve’s differential pressure rating measures the valvescapability to hold pressure from one side either at shutoff orin the partly open position with flow in the line.
4.1.1Category B Valves
Valves manufactured in accordance with this standard shallmeet the requirements of ASME B16.34 for standard classand any additional requirements as specified in this standard.For materials not listed in B16.34,the applicable require-ments and design rules of B16.34 shall be used. In the eventof a conflict between ASME B16.34 and this standard, thisstandard shall prevail.
4.1.2 Fire Tested Valves
If the purchaser specifies fire tested valves, the valves shallbe certified to have been tested to, and met, all of the perfor-mance requirements of API Standard 607. Supporting docu-mentation shall be made available to the purchaser uponrequest.
When specified in the purchase order, valves shall be fur-nished with a lockable device that accepts a purchaser-sup-plied lock that enables the valve to be locked in both the openand closed positions.The lockable device shall be designedsuch that a lock with a 5/16-in. (8-mm) diameter shank,notmore than 4 in. ( 100 mm) long, can be inserted directlythrough appropriate holes and locked. Provisions for a lockable device are permitted even when it is not specified in thepurchase order.
4.1.4 Disc Position Indication
The indication of the position of the disc shall be integralwith the valve shaft.The indication may be accomplished bya mark on the shaft or by a shaft shape.The design shallensure that a valve (andor operator) cannot be assembled tofalsely indicate the valve’s open and closed positions.
4.1.5 Shaft-to-Lever Connections
Shaft-to-lever connections shall be designed so that thelever always correctly indicates the disc position.
4.2.1 The minimum body-wall thickness shall comply withthe applicable ASME Bl6 standard listed in Section 2 basedon the body material.If the applicable standard covers fittingsfor a particular material, the valve minimum wall thicknessshall be as specified for fittings.The valve design shall bestructurally suitable for its stated pressure and temperaturelimits, taking into account that localized thinning may be nec-essary between the shaft bore in the body and thc adjacentbolt holes. Such sections shall be designed in accordance withthe requirements of ASME B16.34.
4.2.2When a wafer-type valve is installed between pipingflanges and the disc is in the closed position, the valve shallbe self-centering, that is, designed to center itself within thebolt circle by using the valve’s outside diameter, or by meansof integral or attached alignment devices.
4.2.3 End flanges for double flanged valves shall be inte-grally cast or forged with the body; however, flanges may bcattached by full-penetration butt welding if agreed to by thepurchaser. End flanges attached by welding shall conform toASME B16.5 and have butt-welding ends for use withoutbacking rings. Welds shall conform to ASME B31.3, as shallqualifications for the welding procedure and the welder orwelding operator.The finished weld thickness shall not beless than the minimum body-wall thickness.
4.2.4If drain or bypass connections are specified by thepurchascr, they shall conform to ASME B16.34 or Mss sp-45, as applicable.
4.3 FACE-TO-FACE DIMENSIONS
4.3.1 Face-to-face dimensions for lug- and wafer-typevalves shall be as listed in Tables 1 and 2-A.These dimen-sions are either: (a) the compressed or installed dimensions ofvalves that use nonmetallic liners, sleeves, or auxiliary sealsextending from or over the body contact faces and acting as flange-sealing elements, or (b) the metal-to-metal dimensionsof valves that do not use such nonmetallic components.
Note 1: When valve body liners，sleeves，or O-ring seals act asflange-sealing surfaces,separate gaskets should not be used unlessspecifically recommended by the manufacturer.