API SPEC 6DSS:2009 pdf download

API SPEC 6DSS:2009 pdf download.Specification on Subsea Pipeline Valves。
Pressure classes shall be specified by the purchaser in accordance with the applicable rating tables for material groups in ASME B16.34 and the pipeline system design.
The purchaser may specify intermediate design pressures and temperatures for a 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, for example ASME Section VIII Division I or Division 2, or BS 5500.
NOTE Non-metallic parts can limit minimum and maximum operating pressures and temperatures. The minimum design temperature shall be 0 °C unless otherwise specified by the purchaser.
6.3 Cavity relief
The manufacturer shall determine whether fluid can become trapped in the body cavity in the open and/or closed position. If fluid trapping is possible, then valves shall be provided with an automatic cavity pressure relief unless otherwise specified by the purchaser. External cavity relief shall not be used.
6.4 External pressure and loads
Valves shall be designed for loads other than internal pressure and temperature (see 6.2), if specified by the purchaser. The purchaser shall specify any other construction, test, functional or accidental load combinations or external pressures which shall be accounted for in the design.
NOTE ISO 13623 specifies construction, functional and accidental loads and provides examples of such loads for consideration by the purchaser.
6.5 Sizes
All valves, except for reduced-opening valves, shall be furnished in the DN sizes listed in Tables 2 to 5. Reduced- opening valves shall be furnished in the nominal sizes in accordance with Table I.
NOTE In this International Standard, DN sizes are stated first, followed by the equivalent NPS size between parentheses. Except for reduced-opening valves, valve sizes shall be specified by DN or 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.
EXAMPLE I A DN 400 (NPS 16) valve with a reduced 334-mm-diameter circular opening through the obturator is specified as 400 x 350.
6.10 Valve ends
6.10.1 Flanged ends
Standard end flanges shall be furnished with raised face or ring-joint faces (raised face or full face). Dimensions, tolerances and finishes, including drilling templates, flange facing, spot facing and back facing, shall be in accordance with
— ASME B16.5 for sizes up to and including DN 600 (NPS 24), except DN 550 (NPS 22),
— MSS SP-44 for DN 550 (NPS 22),
ASME BI 6.47 Series A for DN 650 (NPS 26) and larger sizes.
6.10.2 Welding ends
Welding ends shall conform to Figures 434.8.6 (a) (1) and (2) in ASME B31.4:1998 or Figures 14 and 15 of ASME B31.8:1999 unless otherwise agreed. In the case of a heavy-wall valve body, the outside profile may be tapered at 300 and then to 45° as illustrated in Figure 1 of ASME B16.25:1997.
The purchaser shall specify the outside diameter, wall thickness, material grade, SMYS and special chemical composition of the mating pipe, and whether cladding has been applied.
6.10.3 Special flanges and mechanical joints
Other end connections, such as special flanges or mechanical joints, may be specified by the purchaser.
6.11 Bypass, drain and vent connections
The use of bypass, drain and vent connections should be avoided.
Bypass, drain and vent connections and plug entries shall be drilled and threaded unless otherwise specified. The purchaser may specify other types of connections, such as welded or flanged.
Threads shall be either tapered and capable of providing a pressure-tight seal or parallel-threaded. Connections or plugs with parallel threads shall have a head section for trapping and retaining a sealing member suitable for the specified valve service.
Connection sizes shall be in accordance with Table 6. Thread forms shall be in accordance with ISO 228-1 or ISO 228-2 or ISO 7-1 for metric sizes and ASME B1.1 or ASME B1.20.1 for US Customary (USC) sizes.