BENDIX D-2 User Manual
®
Bendix® D-2™ Governor
SD-01-503
COVER
EXHAUST
PORT
UNLOADER
PORTS (3)
RESERVOIR
PORTS (3)
UPPER SPRING
1
RETAINING
RING
PRESSURE SETTING
MOUNTING
HOLES
17
SPRING
19 LOWER
SPRING SEAT
18
SPRING GUIDE
19 LOWER
SPRING SEA T
8 O-RING
12 O-RING
EXHAUST
(2)
INLET/EXHAUST
8
O-RING
9
VALVE SPRING
16
SEA T
5
STEM
INLET/EXHAUST
VAL VE
ADJUSTING
10
4
SCREW
15
RETAINING
RING
3
LOCKNUT
2
BODY
PISTON
RETAINING
RING
11
PISTON
EXHAUST
FILTERS
11
14
STEM
7
6
13
WASHER
RETAINING
O-RING
INLET/
EXHAUST
VAL VE
9
INLET/EXHAUST
COVER VALVE
SPRING
15
RING
12
10
FIGURE 1 - D-2™ GOVERNOR
BLUE
NONMETALLIC
20
O-RING
CLEAR/BLACK
NONMETALLIC
WITH O-RING
BLACK
RUBBER
FIGURE 2 - TYPES OF COVERS
DESCRIPTION
The D-2™ governor, operating in conjunction with the unloading
mechanism, automatically controls the air pressure in the
air brake or air supply system between a maximum (cutout) pressure and a minimum (cut-in) pressure. The
compressor runs continually while the engine runs, but the
actual compression of air is controlled by the governor
actuating the compressor unloading mechanism which stops
or starts the compression of air when the maximum or
minimum reservoir pressures are reached.
5
11
15
NONMETALLIC METALLIC
5
11
FIGURE 3 - TYPES OF PISTONS
D-2™ governors are provided with mounting holes which allow
direct mounting to the compressor or remote mounting.
Porting consists of three reservoir ports (1/8 inch P.T.),
three unloader ports (1/8 inch P.T.) and one exhaust port
(1/8 inch P.T.).
1
OPERATION
Reservoir air pressure enters the D-2™ governor at one of its
reservoir ports and acts on the piston and inlet/exhaust valve.
As the air pressure builds up, the piston and valve move
together against the resistance of the pressure setting spring.
When the reservoir air pressure reaches the cut-out setting
of the governor, the exhaust stem seat s on the inlet/exhaust
valve, closing the exhaust passage, and then opens the
inlet passage. Reservoir air pressure then flows around the
inlet valve, through the passage in the piston and out the
unloader port to the compressor unloading mechanism. Air
also flows around the piston which is slightly larger at the
upper end. The added force resulting from this larger area
assures a positive action and fully opens the inlet valve.
As the system reservoir air pressure drops to the cut-in
setting of the governor, the force exerted by the air pressure
on the piston will be reduced so that the pressure setting
spring will move the piston down. The inlet valve will close
and the exhaust will open. With the exhaust open, the air in
the unloader line will escape back through the piston, through
the exhaust stem and out the exhaust port.
Never condemn or adjust the governor pressure settings
unless they are checked with an accurate test gauge or a
dash gauge that is registering accurately. If the pressure
settings of the D-2™ governor are inaccurate or it is necessary
that they be changed, the adjustment procedure follows.
Note: If the governor cover is marked nonadjustable and the
adjusting stem has been sheared off, this is a nonserviceable
governor and must be replaced with a new or remanufactured
unit.
A. Remove the top cover from the governor.
B. Loosen the adjusting screw locknut.
C. T o raise the pressure settings, turn the adjusting screw
counter-clockwise. To lower the pressure settings,
turn the adjusting screw clockwise. Note: Be careful
not to overadjust. Each 1/4 turn of the adjusting screw
raises or lowers the pressure setting approximately 4
psi.
D. When proper adjustment is obtained, tighten the
adjusting screw locknut and replace the cover.
(Note: The pressure range between cut-in and cut-out is not
adjustable.)
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performing any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed during
the warranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuable guide in determining the best maintenance interval
for air brake system components. At a minimum, the D-2
governor should be inspected every 6 months or 1500
operating hours, whichever comes first, for proper operation.
Should the D-2™ governor not meet the elements of the
operational tests noted in this document, further investigation
and service of the governor may be required.
SERVICE TESTS
OPERATING TESTS
St art the vehicle engine and build up air pressure in the air
brake system and check the pressure registered by a dash
or test gauge at the time the governor cuts-out, stopping the
compression of air by the compressor. The cut-out pressure
should be in accordance with the pressure setting of the
piece number being used. (Common cut-out pressures are
between 105-125 psi.) With the engine still running, make a
series of brake applications to reduce the air pressure and
observe at what pressure the governor cuts-in the
compressor. As in the case of the cut-out pressure, the cutin pressure should be in accordance with the pressure setting
of the piece number being used. (Common cutting pressures
are between 90-105 psi.)
LEAKAGE TEST
Leakage tests on the D-2™ governor should be made in both
cut-in and cut-out positions.
CUT-IN POSITION
Apply soap solution around the cover and to the exhaust
port. Slight bubble leakage permitted. Excessive leakage
indicates a faulty inlet valve or lower piston o-ring.
™
CUT-OUT POSITION
Apply soap solution around the cover and to the exhaust
port. Slight bubble leakage permitted. Excessive leakage
indicates a faulty exhaust valve seat, exhaust stem o-ring,
or o-ring at the top of the piston.
If the governor does not function as described or leakage is
excessive, it is recommended that it be replaced with a new
or remanufactured unit, or repaired with genuine Bendix parts
available at authorized Bendix parts outlets.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
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