API 608:2008 pdf download

API 608:2008 pdf download.Metal Ball Valves- -Flanged, Threaded and Welding Ends.
3 Terms and Definitions
3.1
Class
An aiplianumenc designation that s used for reference purposes relating to valve pressureiten,perature capability. taking into account valve material mecbanical properties and valve dimensional characteristics. It comprises the letters Class followed by a dimensionless whole number. The number following the letters Class do not represent a measurable value and are not used for calculation purposes except where specified in this Standard. The allowable pressure for a valve having a Class number depends on the valve material and its application temperature and is to be found in tables of pressure!temperature ratings Class usage is applicable to steel valves bearing NPS nominal size designations.
3.2
NPS
An alpha numeric designation of size that is common for components used in a piping system, used for reference purposes, comprising the letters NPS folowed by a dimensionless number indirectly related to the physical size of the bore or outside diameter of the end connection as appropriate, The dimensionless number may be used as a valve size identifier without the prefix NPS. The dimensionless size identification number does not represent a measurable value and is not used for calculation purposes Prefix NPS usage Is applicable to steel flanges bearing Class designations.
3.3
DN
An alpha numenc designation of size that is common for components used in a piping system, used for reference purposes, comprising the letters DN followed by a dimensionless number indirectly related to the physical size of the bore or outside diameter of the end connection as appropriate. The dimensionless number following ON does not represent a measurable value and is not used for calculation purposes except where specified in this international standard. DN usage is applicable to steel valves bearing PN designations.
5.5 Ball-stem Design and Construction
5.5.1 The valve shall be designed 10 insure that if a failure occurs at the stem-to-ball connection or of the stem itself within the pressure boundary, no portion of the stem is ejected by internal pressure.
5.52 The torsional strength of both the stem-to-ball connection and the portion of the stem within the pressure boundary (below top of packing) shall exceed the torsional strength of the stem portion above the pressure boundary (above the top of the packing) by at least 10 %.
5.5.3 The stem and the ball-to-stem connection shaM be designed such that no permanent deformation occurs and no failure of any part occurs when a force applied to the lever or gear operator handwheel produces a torque equal to the greater of:
— 15 ft-lbs (20 N-m), or
— twice the manufacturer’s maximum published torque,
The manufacturer’s maximum published torque shall be based upon dean, dry air service at the maximum differential
pressure rating of the valve.
5.6 Bail Construction
Ball shall have a cylindrical bore and shall be of solid, one-piece construction. Other constructions, such as °holloWtype, cored cavity, or sealed cavity may be furnished only if agreed to by the purchaser.
5.7 Packhig Glands and Gland Bolting
5.7.1 Adjustable packing glands shall be accessible for re-sealing stem packing without the disassembly of valve parts or operator parts.
5.7,2 Packing glands that are threaded into bodies or covers or onto stems shall not be used for valve sizes greater than NE’S 3 (DN 80) unless otherwise specified by purchaser. (See Figure 1 and Figure 2 for parts Identification.)
5.7.3 Vertically split glands shall not be used.
5.7.4 When used, gland bolts shall pass through holes in the packing gland. The use of open slots is not permitted on any portion of the packing gland.
5.7.5 Packing gland bolts shall be designed so that the bolt stress shall not exceed ‘h of the ultimate tensile strength of the bolting material when compressing packing material to a compressive stress of 5500 PSI (38 PApa) at
100°F (38 °C).
5.8 Operation
5.8.1 Unless otherwise specified on the purchase order, manually operated valves shall be equipped with lever-type handles.
5.8.2 Gear operators shall be fitted with handwheels and shall be sized to comply with the requirements of 5.8.3
5.8.3 Unless otherwise specified by the purchaser, the length of the lever handle or the gear ratio, efficiency and handwtieel diameter of gear operators shall be designed so that the required input force to fully open and close valve shall not exceed 80 lb (360 N) when operating valve at manufacturer’s maximum published torque as described in 5.5,3.