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Airmac Owner’s Manual
August 2006
© Glenco Manufacturing Pty Ltd
Page 26 of 44
It should ideally operate in a repeating run-stop or pump-unload cycle, with total
compressor “pumping” time not exceeding 75% or 45 minutes in every hour on average.
The elapsed time between the start and finish of any given pumping cycle (i.e. the
continuous duration that the electric motor operates or the continuous duration that the
petrol or diesel engine runs at full speed) should not exceed 10 minutes.
If the unit cannot supply the compressed air demand without exceeding the above duty
cycle limits, then either the demand should be reduced or the compressor should be
replaced with a unit having a larger free air delivery.
The duty cycle limit is intended to protect the compressor pump valves and heads
against stabilized high operating temperatures that can cause premature pump failure.
In applications where multiple compressors are required to satisfy the total air demand,
it is recommended that the distribution system be split into separate circuits each
supplied by a single compressor operating within its recommended duty cycle limits.
The parallel operation of individual compressors supplying a common air system can
often result in very unbalanced duty cycles amongst the units unless they share a single
controller.