BENDIX DOUBLE CHECK VALVES Manual
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Bendix
Double Check Valves
SUPPLY
DELIVERY
O-RING
CAP
BODY
FIGURE 1 - DC-4
™
DOUBLE CHECK VALVE (SHUTTLE TYPE)
DESCRIPTION
Double check valves are used in an air brake system to
direct a flow of air into a common line from either of two
sources, whichever is at the higher pressure. They may be
used for directing air flow for specific functions or to select
the higher pressure of either of two sources of air as a
supply source.
Bendix manufactures two types of double check valves:
shuttle and disc. Although the valves are somewhat different
physically, the same function is performed by both types.
The difference in the design of the two valves is that the
shuttle type has a movable shuttle to seal off the lower
pressure source, whereas the disc type has a movable disc.
SUPPLY
O-RING
SHUTTLE
VALVE
CAP
SHUTTLE
GUIDE
FIGURE 2 - DOUBLE CHECK VALVE (DISC TYPE)
OPERATION
As air under pressure enters either end of the double check
valve (inlet port) the moving shuttle or disc responds to the
pressure and seals the opposite port, assuming it is at a
lower pressure level than the other. The air flow continues
out the delivery port of the double check valve. The position
of the shuttle or disc will reverse if the pressure levels are
reversed. Double check valves are designed so that the
shuttle or disc can never impede the backflow of air in the
exhaust mode.
Figure 3 (see page 2) illustrates a typical use of a double
check valve to control a given device, such as trailer brakes,
from either of two control sources.
Figure 4 (see page 2) illustrates a typical use of a double
check valve to supply air to a system or systems from either
of two separate sources, whichever is at the greater pressure
level. In this type of installation the pressure differential to
which the valve is subjected may under certain conditions
be minimal. It is therefore suggested that performance of
the double check valve will be optimized if it is mounted in
the horizontal position.
DELIVERY
SUPPLY
VALVE
GUIDE
SUPPLY
DELIVERY
VALVE
DISC
BODY
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