Duty Cycle; Compressor Installation; Discharge Line; System Drawing - BENDIX TU-FLO 750 COMPRESSOR Manual

Discharge Optional "Ping" Tank
Line
Compressor
FIGURE 6A - SYSTEM DRAWING

DUTY CYCLE

The duty cycle is the ratio of time the compressor spends
building air to the total engine running time. Air compres-
sors are designed to build air (run "loaded") up to 25% of the
time. Higher duty cycles cause conditions that affect air
brake charging system performance which may require ad-
ditional maintenance. Factors that add to the duty cycle
are: air suspension, additional air accessories, use of an
undersized compressor, frequent stops, excessive leakage
from fittings, connections, lines, chambers or valves, etc.
Refer to Table A in the Troubleshooting section for a guide to
various duty cycles and the consideration that must be given
to maintenance of other components.

COMPRESSOR INSTALLATION

While the original compressor installation is usually com-
pleted by the vehicle manufacturer, conditions of operation
and maintenance may require additional consideration. The
following presents base guidelines.

DISCHARGE LINE

The discharge line allows the air, water-vapor and oil-vapor
mixture to cool between the compressor and air dryer or
reservoir. The typical size of a vehicle's discharge line, (see
column 2 of Table A in the Troubleshooting section) assumes
a compressor with a normal (less than 25%) duty cycle,
operating in a temperate climate. See Bendix and/or other
air dryer manufacturer guidelines as needed.
4
Air Dryer
Governor
(Governor plus Synchro valve
™
for the Bendix ® DuraFlo
Compressor)
The Air Brake Charging System
compressed air for the braking system as well as other air
accessories for the vehicle. The system usually consists
of an air compressor, governor, discharge line, air dryer,
and service reservoir.
Optional Bendix
Oil Coalescing Filter
Service Reservoir
596 (Supply Reservoir)
The discharge line must maintain a constant slope down
from the compressor to the air dryer inlet fitting or reservoir
to avoid low points where ice may form and block the flow. If,
instead, ice blockages occur at the air dryer or reservoir
inlet, insulation may be added here, or if the inlet fitting is a
typical 90 degree fitting, it may be changed to a straight or
45 degree fitting. Shorter discharge line lengths or insula-
tion may be required in cold climates.
While not all compressors and charging systems are
equipped with a discharge line safety valve this component
is recommended. The discharge line safety valve is installed
in the cylinder head (Tu-Flo
pressor discharge port and protects against over pressurizing
the compressor in the event of a discharge line freezeup.
THREAD
FIGURE 6B - DISCHARGE LINE SAFETY VALVE
supplies the
® PuraGuard ® QC ™
Reservoir Drain
®
550/750) or close to the com-
HOLE