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API Specification 6D Twenty-second Edition - Introduction |
6.7 Valve ends
6.7.1 Flanged ends
Standard end flanges shall be furnished with a
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 B16.47 Series A for DN 650 (NPS 26) and
larger sizes.
6.7.2 Welding ends
Welding ends shall conform to Figures 434.86 (a)
(1) and (2) of ASME B31.4 or Figures 14 and 15
of ASME B31.8 unless otherwise agreed. In the
case of a heavy-wall valve body, the outside
profile may be tapered at 30° and then to 45° as
illustrated in Figure 1 of ASME B16.25.
The purchaser shall specify the outside
diameter, wall thickness, material grade, SMYS
and special chemistry of the mating pipe, and
whether cladding has been applied.
6.7.3 Special flanges and mechanical joints
Other end connections, such as special flanges
or mechanical joints, may be specified by the
purchaser.
6.8 Pressure relief
The manufacturer shall determine whether fluid
can become trapped in the body cavity in the
open- and/or closedvalve position. If fluid
trapping is possible, then valves for gas
service, unless otherwise specified by the
purchaser, and liquid service shall be provided
with an automatic cavity pressure relief.
Cavity relief, when required, shall prevent the
pressure in the cavity from exceeding 1,33 times
the valve pressure rating determined in
accordance with 6.1 for material at 38°C
(100°F). External cavity relief valves shall be
DN 15 (NPS 1/2) or larger.
6.9 Bypass, drain and vent connections
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.
Thread sizes shall be in accordance with Table
7. Thread forms shall be in accordance with ASME
B1.1, ASME B1.20.1, ISO 228-1, ISO 228-2 or ISO
7-1.
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