China (Mainland)
Features
1. ST series bunker dredging device has overcome defects of other dredging forms, such as high strength, small effect, large investment and tank body damage.
2. High Automation: Save coal bunker system layout. The dredging device usually does not work. When the coal bunker cuts off flow due to congestion, the device will dredge and shut down after smooth flow automatically.
3. Dredge Area: The dredge area is 2-6 square meters; the dredge height is 2-3m; the machine will automatically shut down after smooth flow.
4. Energy Conservation: Momentum is greater than 60,000N, while the power consumption is only 3KW.
5. Convenient Installation and Maintenance: Reliable use and high cost efficiency. Under normal circumstances, the hydraulic oil will be replaced every 2 years, namely, years return with once investment.
6. Wide Application: The series dredging device is applicable to different storage containers, such as square tapered, conical, hyperbolic, concrete structure and steel structure warehouses. In addition to coal bunker for coal-fired power plants, it also can be widely applied to similar storage containers in other industries, such as mining, metallurgy, cement, chemicals and construction, etc.
7. Ideal Environmental Protection Effect: This series dredging device adopts high-pressure pumps to drive hydraulic fluid work in a closed loop pipe, so it has no harm, pollution or noise in the course of use.
8. Easy Control (local or remote control); locally, the dredging machine can be started manually and automatically stop after a cycle of action. When remote control is required, dredging machine has an interface with the remote control switch distributed control system (DCS) and the action will automatically stop after a cycle.
9. The action and time of dredging machine will be displayed by the counter.
10. The dredging device has emergency stop button (local or remote) to make operators stop the dredging machine or cut off power at any time.
11. The dredging device has pump motor protection function; when it is overloaded or lacks phase, the electrical control panel will issue &ldquo instructions and carries out automatic power-off reset in 3 seconds. If the machine is overloaded for 3 times within 9 seconds, the motor will cut off power and pump will be stopped. It will start normal work when the start button is pressed after the error is handled.
Working Principle of the Dredging Machine:
1. Measure coal feeder belt thickness, connect limit switches in the absence of coal (or less than half of the thickness) and issue power command.
2. Power command makes motor contactor combined and motor rotates clockwise.
3. Motor drives gear pump and outputs pressure oil, which will reach power cylinder through solenoid valve to make the scraper do up and down work for dredge.
4. After dredging, the coal will fall on the belts to make signal interrupt automatically, so the dredging cycle ends.
A: A control station with two dredging bars:
1. Signal device on coal feeder or main control room DCS percept that media stops or media flow is less than set values, and the limit switch will be connected to send start signal to dredging machine.
2. Control station contactor combines and the motor starts and rotates clockwise to drive oil pump, which will deliver pressure oil through solenoid valve to fuel tank. The rib plates and blades driven by rods make dredging machine move up and down along silo wall, so as to play a role of dredging. Since the dredging machine fuel tank is left-right layout, the two fuel tanks move up and down oppositely (upper left, lower right or vice verse) with respect to the reverse connection of oil tubes.
3. When the media restores circulation or reaches the set value, the flow of the media makes signal limit switch off, so the signal is switched off or the main control room DCS will issue a stop signal. The motor and pump on dredging machine control station stop working, the tanks and dredging levers will end a dredging cycle. And the dredging machine will be on standby status.
4. In manual debugging, press the manual button to replace signal device or DCS to send start signal to the control station, and the dredging machine will move according to the order of &ldquo and 2”. Release the manual button, then all the action stops. Manual button is only used in dredging machine debugging!
B: A control station with four (or more) dredging bars; hopper 1 # and 2 # with two dredging bars controlled by one control station:
1. When signal device (DCS) installed in hopper 1# of coal feeder percepts that media stops or media flow is less than set values, limit switch 1 will be connected to send start signal to dredging machine control station.
2. Control station 1# contactor combines and the motor starts and rotates clockwise to drive oil pump, which will deliver pressure oil through solenoid valve 1# to fuel tank of hopper 1#. The rib plates and blades driven by rods make dredging machine move up and down along silo wall, so as to play a role of dredging. At this time, since the solenoid valve 2 # is in the close position, hopper 2 # tank is motionless.
3. Dredging action and manual control process are the same as a control station with two dredging bars.
4. When hopper 2 # blocks, the dredging machine will act as the above.
5. If there are two blocked hoppers, signal controllers 1 # and 2 # will respectively send signals to control system, so two solenoid valves and two fuel tanks move according to pre-set sequence, namely, one hopper will be dredged, then the other till completely dredge.
Control Meathods
The alarm and control device consist of a material flow signal switch, a programmable logic controller, an electronic counter, an over-current protection circuit breaker and a dredging device. The dredging machine unit can be put into operation after the operation of coal feeder; material flow switch will delay 5 seconds (adjustable) to send breaking signal to dredging device. When the breaking signal is issued, dredging machine can automatically dredge until the breaking signal disappears.
The system has three control methods: Manual control, timing automatic control and intelligent automatic control:
1. Manual Control: Press start button to control dredging machine on the automatic control device panel and one action can complete a cycle.
2. Timing Automatic Control: The set of timing switch on the device panel can switch timing control; set timing control when the feeder is running, so the dredging machine will move according to the setted time interval and each movement will complete a cycle to prevent spontaneous combustion of long-term coal accumulation.
3. Intelligent Automatic Control: In the operation of coal feeder, if the off switch acts, automatic interlocking control dredging machine will move until the signal disappears and the dredging machine stops.
Automatic Protection of the Dredging Machine
1. Allowable Conditions of Dredging Machine Starting: Dredging machine and coal feeder control interlock; if the dredging machine runs when coal feeder does not work, it will ultimately result in coal re-blocking, coal shedding or more serious situation to equipment damage because a coal flow can not be formed. The dredging machine we installed interlocks with coal feeder control, i.e., the dredging machine only starts when the coal feeder runs.
2. Maintenance Protection:
(1) Overload, over current, phase failure protection;
(2) Semi-load start protection;
(3) One run-time protection;
(4) Auto off-coal signal continuous operation maximum number protection;
(5) System continuous operation maximum number protection;
(6) Hydraulic cylinder reset protection.