—valves NPS 4 (DN 100) to NPS 12 (DN 300): one size below nominal size of valve with bore according to Table 1,

—valves NPS 14 (DN 350) to NPS 24 (DN 600): two sizes below nominal size of valve with bore according to Table 1。 EXAMPLE A NPS 16 (DN 400) Class 1500 reduced-opening ball valve has a minimum bore of 11。31 in。 (287 mm)。

Reduced-opening valves with a noncircular opening through the obturator shall be supplied with a minimum opening by agreement。

4Design

4。1Design Standards and Calculations

Pressure-containing parts, including bolting, shall be designed with materials specified in Section 6。

Design and calculations for pressure-containing elements shall be in accordance with an internationally recognized design code or standard with consideration for pipe loads, operating forces, etc。

NOTE Examples of internationally recognized design codes or standards are ASME BPVC, Section VIII, Division 1 or Division 2; ASME B16。34; EN 12516-1 or EN 12516-2; and EN 13445-3。

The allowable stress values shall be consistent with the selected design code or standard。

If the selected design code or standard specifies a test pressure less than 1。5 times the design pressure, then the design pressure for the body calculation shall be increased such that the hydrostatic test pressure in 9。3 can be applied。

4。2Pressure and Temperature Rating

Valves covered by this specification shall be furnished in one of the following pressure classes:

— Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500,

or Class 2500。

Pressure–temperature ratings for class-rated valves shall be in accordance with the applicable rating table for the appropriate material group in ASME B16。34。

Pressure–temperature ratings for Class 400 valves shall be in accordance with the applicable rating table for the appropriate material group in ASME B16。5。

NOTE It is not required that identical material or material form be used for body and bonnet or cover parts。

The pressure–temperature rating applied shall be based on the material group of the valve end connection。 Where the valve ends are made from material in two different groups, the material with the lower pressure– temperature rating shall govern。

All metallic pressure-containing and pressure-controlling parts shall be designed to meet the applicable valve pressure–temperature rating。

If intermediate design pressures and temperatures are specified by the purchaser, the pressure–temperature rating shall be determined by linear interpolation in accordance with ASME B16。34。 Valves with flanged end(s) shall not be designed to an intermediate rating due to the risk of the valve being transferred to a different application, which may utilize the full flange rating。

Pressure–temperature ratings for valves made from materials not covered by ASME B16。34 shall be determined from the material properties in accordance with the applicable design standard。

Manufacturer shall advise any limits on the design pressures and the minimum and maximum design temperatures due to nonmetallic parts。

The maximum operating pressure at the minimum and maximum operating temperatures shall be marked on the nameplate。

4。3Sizes

Valves constructed to this specification shall be furnished in nominal sizes as listed in Table 1。

NOTE In this specification, NPS sizes are stated first followed by the equivalent DN size between brackets。

Except for reduced-opening valves, valve sizes shall be specified by the nominal pipe size (NPS) or nominal diameter (DN)。

Reduced-opening valves with a circular opening shall be specified by the nominal size of the end connections and the nominal size of the reduced opening in accordance with Table 1。 EXAMPLE 1 A NPS 16 (DN 400) Class 150 valve with a reduced 11。94 in。 (303 mm) diameter circular opening shall be specified as NPS 16 (DN 400) × NPS 12 (DN 300)。