Non-Compression Of Air (Unloaded); Compressor & The Air Brake System; Operational-Loaded (Intake); Operational-Unloaded - BENDIX TU-FLO 750 COMPRESSOR Manual

AIR
DISCHARGE
PORT
DISCHARGE
VALVE
CLOSED
FIGURE 4 - OPERATIONAL-LOADED (INTAKE)
AIR
DISCHARGE
PORT
DISCHARGE
VALVE
OPEN
FIGURE 5 - OPERATIONAL-LOADED (COMPRESSION)
air in the discharge line from returning to the cylinder bore
as the intake and compression cycle is reseated.

NON-COMPRESSION OF AIR (UNLOADED)

When air pressure in the reservoir reaches the cut-out set-
ting of the governor, the governor allows air to pass from the
reservoir, through the governor and into the cavity above the
unloader pistons. The unloader pistons move down holding
the inlet valves off their seats (see Figure 6.) With the inlet
valves held off their seats by the unloader pistons, air is
pumped back and forth between the two cylinders, and the
discharge valves remain closed. When air pressure from the
reservoir drops to the cut-in setting of the governor, the gov-
GOVERNOR
PORT
AIR
INLET
PORT
INLET
VALVE
DISCHARGE
OPEN
PISTON
MOVING
DOWN
FIGURE 6 - OPERATIONAL-UNLOADED
ernor closes and exhausts the air from above the unloader
GOVERNOR
pistons. The unloader springs force the pistons upward and
PORT
the inlet valves return to their seats. Compression is then
resumed.
COMPRESSOR & THE AIR BRAKE SYSTEM
GENERAL
AIR
INLET
The compressor is part of the total air brake system, more
PORT
specifically, the charging portion of the air brake system. As
a component in the overall system its condition, duty cycle,
INLET
proper installation and operation will directly affect other
VALVE
CLOSED components in the system.
Powered by the vehicle engine, the air compressor builds
PISTON
the air pressure for the air brake system. The air compres-
MOVING
UP
sor is typically cooled by the engine coolant system,
lubricated by the engine oil supply and has its inlet con-
nected to the engine induction system.
As the atmospheric air is compressed, all the water vapor
originally in the air is carried along into the air system, as
well as a small amount of the lubricating oil as vapor. If an
air dryer is not used to remove these contaminants prior to
entering the air system, the majority, but not all, will con-
dense in the reservoirs. The quantity of contaminants that
reach the air system depends on several factors including
installation, maintenance and contaminant handling devices
in the system. These contaminants must either be elimi-
nated prior to entering the air system or after they enter.
DISCHARGE
PORT
VALVE
CLOSED
UNLOADER
GOVERNOR
PISTON
PORT
AIR
INLET
PORT
INLET VALVE
HELD OPEN
BY UNLOADER
PISTON
3