Pilot Air SILENT K17SI, Instruction And Maintenance Manual

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17 | P a g e Silent Series Rev 01 03-2020
8.Principles of Operation
Circuit diagram:
When the compressor is switched on, the head blowdown solenoid valve (N.O. normally open) is
triggered and closes, thus blocking blowdown (in motors with delta-star configuration, the solenoid
valve closes when it receives the signal from the delta power contactor). Each time the machine is
stopped, either intentionally or accidentally, this solenoid valve unloads the pressure from the head
in the section of the hose between the unit and the check valve.
When the pressure inside the sump reaches the maximum value that has been set, the pressure
switch stops the machine until the pressure falls to the re-start value. These pressure values are set
by the pressure switch manufacturer.
Compressors with delta-star starting that also incorporate the OFF-LOAD RUN function are designed to
run continuously. This means that the compressor runs even when the maximum operating pressure
has been reached, but without compressing air in the sump. This function is useful for heavy-duty
applications that would require excessively frequent startups in normal configuration and result in
excessive amounts of energy being absorbed and wasted. The off-load run function is available in 2
different versions: pressure switch with solenoid valve or pilot valve.
When the maximum pressure value is achieved, the pressure switch sends the signal to a N.C.
(normally closed) 3-way solenoid valve that allows the compressed air to be unloaded from the sump
and triggers the pistons on the head of the pump unit, which block the intake vanes. The motor
continues to run but the air intake is interrupted. In order to guarantee safety, a second pressure switch
is installed, with a pressure setting that is higher than the OFF-LOAD RUN value (usually 11 bar).
When the line sends a new request for air, the pressure switch moves to the minimum pressure
value, the solenoid valve stops activating the pistons and the compressor takes in air. The pilot valve
works the same way as the pressure switch and solenoid valve, by triggering the pistons to stop and
then restart suction.
Before starting the compressor, the following preliminary checks must be carried out (in strict
compliance with the instructions set forth herein):
1. Power supply voltage and frequency must correspond to those specified on the machine
data plate.
A LED (40.9)[fig.14] on the control panel of SILENT2 and SILENT4 versions switches
on to indicate that the compressor is energized
2. The pump unit must turn to the RIGHT , when looking at the machine from the front. This can be
verified by removing the front panel of the cabinet. If requested by the customer, a phase
sequence relay can be installed. This prevents startup in case of incorrect phase direction and
signals the fault condition by means of the dedicated LED.
3. When using lubricated compressors, check the oil level through the transparent plug (27)
[fig.3-4-5].
This should be at the half-way mark on the display (transparent plug) on the pump
unit. (In case of incorrect oil levels, refer to the chapter
entitled “Maintenance Operations”). The
compressor is supplied with the following type of oil:
•
Q8 Haydn 100 for single-phase machines with less than 2.2 kW (3HP).
•
Q8 Haydn 150 for three-phase machines with more than 2.2 kW (3HP).
4. Models in the SILENT1 series:
Make sure that the condensate drain valve under the sump [fig.12] is closed.
5. Models in the SILENT1 series:
Check that the pushbutton on the pressure switch
[fig.13] is set to “OFF - 0”.