MIL-HDBK-1022A
downstream outlet pressure exceeds the inlet pressure (which
normally holds the valve open), the valve will close and
prevent backflow.
6.5.3.4
Remote Operation. Hydraulically operated diaphragm
control valves can be operated remotely. This is accomplished
by installing tubing from the point of pressure sensing to the
valve or by using remote-controlled solenoids within the trim.
6.5.3.5
Materials of Construction. Use stainless steel or
aluminum (in non-contained areas) pilots and tubing. Use
bodies, bonnets, and covers made of aluminum, stainless steel,
or internally plated (chromium or nickel) cast steel. Provide
viton or Buna-N diaphragm and disc ring. Enclose electrical
apparatus according to classification of the area in which
they are installed. Provide means to wire seal adjustable
pilots. Do not use aluminum valves within a contained area.
6.5.3.6
Applications. For pipeline systems, use
hydraulically operated diaphragm control valves in the
following applications:
a) Rate of flow control.
b) Pressure reduction.
c) Pressure relief.
d) Excess flow shutdown.
6.5.3.7
Combinations. A combination of these controls is
also possible. Typical use of these controls is on a
filter/separator for water slug shutoff and rate of flow
control.
6.5.4
Surge Suppressors. If used, provide surge
suppressors of the diaphragm or bladder type; equipped with a
top-mounted liquid-filled pressure gauge, isolation valve,
limited bleed-back check valve, and drains; and located as
close as possible to the point of shutoff that is expected to
cause the shock. Provide a check valve at the bottom with a
weep hole in the clapper. Surge suppressors can reduce shock
pressure but will not eliminate it entirely. The preferred
solution to hydraulic shock is conservative piping design, use
of loops, and slow-closing valves.
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