Parent System «

CONTROL SYSTEM:

This type of control system constitutes a governing component of our chain-type fixed weed screen cleaning systems installed at open-source water intakes of some irrigation pumping stations in Egypt. It is used to monitor and control the cleaning systems in both the automatic and manual operation modes. Control of automatic operation is carried out through an internal control panel. Manual operation is handled by an external control panel appropriately located so as to allow the operator to manage monitoring and control functions. Keeping in mind that several machines are normally installed in a single site, the control mechanism adopted must possess enough flexibility to allow for targeting a particular machine, any subset or even the whole set of installed machines. When a particular machine is accidentally overloaded, it is only this machine that has to be stopped. Alternatively, when the cleaning system runs out of grease, all machines are automatically stopped. This applies to operating and non-operating machines. The control system thus provides necessary safeguards, handles machine malfunctions and avoids machine breakdown.

INTERNAL CONTROL PANEL:

An internal control panel is used to allow for monitoring and controlling chain-type fixed weed screen cleaning systems during automatic operation. Two contactors operate the machines in both the normal raking direction and the reverse direction. Two timers automatically connect and disconnect the geared motor so as to allow for a prescribed number of raking cycles. A third timer adjusts the lower sprocket greasing interval. Separate thermal switches enable the disconnection of geared motors, greasing pump motor and greasing solenoids. All indicators and controls are available on the external side of the internal control panel door.

EXTERNAL CONTROL PANEL:

Appropriately located, the external control panel allows the operator to easily monitor the motion of all installed weed screen cleaning machines during manual operation in both the normal and reverse directions. All indicators and controls are available on the internal door of the external control panel. The external door is only meant for protection purposes.

MULTIPLE-MACHINE CONTROL:

The control system provides the options to monitor and control a single machine, multiple machines or the whole set of machines installed in the site. This applies to both the automatic and the manual modes. Controls are conveniently arranged in a matrix of rows and columns to provide the necessary monitoring and control means for different machines. Four rows of LEDs followed by three rows of switches form the automatic control matrix. Two rows of LEDs followed by two rows of selection switches and three rows of push buttons constitute the typical arrangement of the manual control matrix. In both cases, the number of matrix columns is equal to that of the machines installed with each column representing a particular machine.

GEARED MOTOR:

A 3-phase 3-KW 1500-rpm electric motor with brake is combined with a gearbox in one unit to provide the power necessary to drive each weed screen cleaning machine. The output speed is reduced to 7.8 rpm to suit raking requirements.

TORQUE LIMITER:

A torque limiter is used to limit the drive shaft torque so as to protect the machine chain from mechanical overloads. The torque calibration value corresponds to the sum of the rake weight and its load carrying capacity. Accidental overloads during normal or reverse operation can thus be sensed, electric motor is disconnected and the machine is stopped. The machine would not be operable unless the factors causing the overload are removed.

PROXIMITY SWITCH:

A proximity switch is used to determine the rake stop location during automatic operation.

GREASING CONTROL:

A greasing system is used to grease lower sprockets. The greasing pump is self-started once a weed screen cleaning machine is operated in either its manual or automatic mode. A pre-defined greasing interval is set through a 60-second-range timer to operate and stop the greasing pump. Turning-on the greasing pump motor opens a specific solenoid valve thus allowing the flow of grease to the lower sprocket of the machine to be operated. Conversely, turning-off the motor closes the solenoid valve. A green LED is turned on as long as greasing is in-progress. Once the greasing pump tank runs out of grease, all machines are stopped, an alarm is automatically operated and the grease standard level must be restored before machines can be restarted. No machine can resume operation unless the greasing pump tank is refilled to its standard level.

MECHANICAL OVERLOADS:

Rakes may be overloaded due to overweight of collected bodies. The existence of tree trunks or branches between the rake and screen bars or the chain and sprockets provides another source for overloads. Alternatively, some screen bar may be so dislocated that it hinders the rake motion in normal or reverse operation. This can be identified by repetitive rake stops at some particular location. In all cases, the machine must be automatically stopped once its rake is overloaded.

EMERGENCY STOP:

In case of emergency, an emergency push button is pressed. This stops the operation of all machines, fixes each rake at its current location, turns on a red LED on the internal control panel and activates the alarm. Machines will never resume operation unless emergency causes are removed, emergency button is reset and the restart button on the external control panel is pressed.