TM 5-3810-307-24-1-2
Water Flow Rate: To provide adequate head cooling, a
water flow rate of 16.9 liters [4.5 gallons] plus or minus
3.785 liters [1.0 gallon] per minute is required at rated
engine speeds. Recommended minimum water flow rate
through the head is 9.4625 liters [2.5 gallons] per minute at
rated engine speed with a 1:1 compressor drive ratio.
Compressor to engine drive ratios higher than 1:1 can
require higher coolant flow rates to provide optimum op-
erating life.
Water Temperature: The engine's cooling water must be
sourced immediately after the water pump to provide the
lowest temperature water available. Water temperature to
the compressor must never exceed 93C [200F].
Water Lines: inlet and outlet water line size must be 12.7
mm [0.50-inch] outside diameter (OD) minimum of opti-
mum flow rate. Either water port can be used for inlet or
outlet water plumbing.
Normal air compressor life cycle is a function of application
operating parameters and system installation con-
figuration, both of which, along with maintenance prac-
tices, will influence compressor duty cycle.
Duty Cycle
Duty cycle is defined as the period of time the compressor is
pumping (compressing air) as a percentage of total operating
time. The air compressor duty cycle defines the life cycle,
generally, lower duty cycles result in the longest life cycles.
Duty cycle observations range from 5 to 10 percent on new
vehicles used in line haul tractor applications to as high as
50 to 60 percent, or higher, for off-highway, garbage pick-
up, or transit bus applications. Duty cycle can be measured
on vehicles with either data recorders or by monitoring or
timing the pumping cycle of the compressor (audible
measurement) during vehicle operation.