6 Design
6.1 Pressure and temperature rating
The nominal pressure (PN) class or the ANSI rating class shall be used for the specification of the required pressure class.
Valves covered by this International Standard should be furnished in one of the following classes:
PN 20 (Class 150)           PN 150 (Class 900)
PN 50 (Class 300)           PN 250 (Class 1500)
PN 64 (Class 400)           PN 420 (Class 2500)
PN 100 (Class 600)

Pressure classes shall be specified by the purchaser in accordance with the applicable rating tables for material groups in ASME B16.34.
The purchaser may specify intermediate design pressures and temperatures for his specific application. Allowable operating pressures and temperatures for valves made of materials not covered by ASME B16.34 shall be determined by calculations in accordance with an agreed pressure vessel design standard, such as ASME Section VIII, Division 1 and Division 2, or BS 5500.

Non-metallic parts may limit minimum and maximum operating pressures and temperatures.
The maximum operating pressure at the minimum and maximum operating temperatures shall be marked on the nameplate

6.2 Sizes
All valves, except for reduced-opening valves, shall be furnished in the nominal sizes (DN) listed in Tables 2 to 6. Reduced-opening valves shall be furnished in the nominal sizes in accordance with Table 1.
NOTE In this International Standard, DN sizes are stated first followed by the equivalent NPS size between brackets. Except for reduced-opening valves, valve sizes shall be specified by the nominal sizes (DN) or nominal pipe size (NPS).

Reduced-opening valves with a circular opening through the obturator shall be specified by the nominal size of the end connections and the nominal size of the minimum bore of the obturator in accordance with Table 1, except that for valve sizes DN 50 (NPS 2) or smaller the actual bore of the obturator shall be specified. For example, a DN 400 valve with a reduced 334-mm-diameter circular opening through the obturator shall be specified as 400 × 350.

Reduced-opening valves with a non-circular opening through the obturator and reduced-opening check valves shall be designated as reduced-bore valves and specified by the nominal size corresponding to the end connections followed by the letter "R". For example, a reduced-bore valve with DN 400 end connections and a 381 × 305 mm rectangular opening through the obturator shall be specified as 400R.

6.3 Face-to-face and end-to-end dimensions

Unless otherwise agreed, face-to-face and end-to-end dimensions of valves shall be in accordance with Tables 2 to 6.
Face-to-face and end-to-end dimensions for valve sizes not specified in Tables 2 to 6 shall be in accordance with ASME B16.10. Face-to-face and end-to-end dimensions not shown in Tables 2 to 6 or in ASME B16.10 shall be established by agreement.
The length of valves having one welding end and one flanged end shall be determined by adding half the length of a flanged-end valve to half the length of a welding-end valve.
Tolerances on the face-to-face and end-to-end dimensions shall be ± 2 mm for valve sizes DN 250 and smaller, and ± 3 mm for valve sizes DN 300 and larger.

The nominal size and face-to-face or end-to-end dimensions shall be stated on the nameplate if not specified in or not in accordance with Tables 2 to 6.

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