ARAG Electriccontrol unit for crop-spraing application 871 - Manual (Page 7)

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2.2 Components function
1 Gearmotor of main control valve
Opens or closes main valve to let fluid flow through the system.
Gearmotor is operated via a suitable switch installed on the control device of the unit (e.g.: control
box or computer).
•
Valve open = liquid sent directly to the circuit for application;
• Valve closed = liquid sent to the tank;
the suction system, if present, starts functioning.
2 Maximum pressure valve
Eliminates the excess liquid when the set pressure level is reached.
Can be adjusted manually using the appropriate knob; the knob has a different colour according to
the maximum pressure for the valve (refer to par. 7.1 - Correspondence between valve parts and
maximum valve pressure).
3 Proportional electric valve
Adjusted via a dedicated switch installed on unit control device (e.g.: control box or computer), this
valve regulates spraying pressure: when the vehicle progress speed changes during spraying, the
volume of the liquid distributed per surface unit (litres/ hectare) remains stable.
The increase or reduction in delivery is proportional to the number of revs of the engine with a
tolerance of +- 20%.
4 Filter
Protects nozzles from dirt, which would eventually reduce their performance.
With self-cleaning filters, there is less need for frequent cleaning of the cartridge inside the filter.
5 Boom section electric valves
These valves open/close the corresponding boom section; for valves with metered by-passes, the
valve closed position is the same as the drain position for the respective metered by-pass.
6 Metered by-passes
These are adjusted so the level of spraying pressure remains steady when one or more sections
of the boom are closed.
7 Pressure gauge adapter or pressure sensor connection (supplied on request)
Connection for pressure gauge or pressure sensor to provide working pressure indication when
main control valve is open.
Operation details will be described below.
For information on the adjustment of individual components, see Chap. 4 - Setting
before use - and Chap. 5 - Use.
For information on connectable control devices, see Par. 3.4 - Connection to control
devices.