30
Table 5: Typical ‘V’ Belt Defl ection Forces Table
ADJUSTMENT OF MANUAL
UNLOADER CONTROLS
Hydraulic Unloading - All pressure lubricated Hycomp
model air compressors come with hydraulic unloading,
also known as load-less start. The hydraulic unloader
valve senses the oil pressure developed in the oil
pump, and allows air from the receiver to fl ow to the
unloader towers when the oil pressure is too low. When
the oil pressure has increased to an acceptable level,
the oil pressure closes a piston/spring mechanism,
closing off the receiver air pressure, allowing the
unloader towers to depressurize and thereby loading
the compressor.
The hydraulic unloader valve may be plumbed at the
factory. If not, see the Compressor Installation section
in this manual for details on how to plumb the unloader
control.
Two hydraulic unloader valves are available for
different receiver pressure ranges:
1RX001-3 Receiver pressure 0-200 psig
1RX001-4 Receiver pressure 200-500 psig
The proper hydraulic unloader valve must be used for
the operating requirements. No other adjustment of
the hydraulic unloader is possible.
Constant Speed Unloading (Dual Control if Used in
Conjunction with Hyrdaulic Unloader) - All pressure
lubricated Hycomp model ambient air compressors
can be set-up for constant speed unloading. When
used in conjunction with a hyrdraulic unloader valve,
this allows protection from low oil pressure damage,
as well as allowing the compressor to run continuously
with varying air demands. If the compressor starts/
stops more than six (6) times per hour, this is the
preferred control. Air pressure from the receiver is
split between the hydraulic unloader (described above)
and the constant speed unloader. The constant speed
unloader senses this receiver air pressure, and when it
rises above the user adjusted level, the constant speed
unloader allows air pressure to travel to the three-way
check valve, and then to the unloader towers, opening
the inlet valves. When the receiver air pressure drops
below a specifi ed level, the constant speed unloader
shuts off air fl ow to the unloader towers, vents the
remaining air pressure, and allows the unloader towers
to depressurize, loading the compressor.
‘V’ Belt
Cross Section
Small Sheave
Diameter Range (in)
Recommended Defl ection Force (lbs)
MIN. MAX.
4.6 10.2 14.8
5.0 - 5.2 11.6 17
2B 5.4 - 5.6 12.4 18.2
6.0 - 6.8 14.2 20
7.4 - 9.4 16.2 24
4.6 15.3 22.2
5.0 - 5.2 17.4 25.5
3B 5.4 - 5.6 18.6 27.3
6.0 - 6.8 21.3 30
7.4 - 9.4 24.3 36
4.6 20.4 29.6
5.0 - 5.2 23.2 34
4B 5.4 - 5.6 24.8 36.4
6.0 - 6.8 28.4 40
7.4 - 9.4 32.4 48
7.0 36.4 52
7.5 38.8 56
4C 8.0 - 8.5 44 64
9.0 - 10.5 48 72
11.0 - 16.0 56 84
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