Rotary coal sampling unit are used mainly in the coal industry to acquire samples of coal from a continuously moving conveyor belt.
Components Of Coal Sampling Unit
1. Primary Sampler
It consist of following parts:
Control Panel – A PLC based control panel controls the operation of the sampler.
Housing – The main components of the housing are the top cover for the sampling arm and cutter, Dust cover to minimize pollution and spillage during the sampling action, mounting position for the sensor proximity switch, sample discharge chute.
Mounting Frame – The frame is usually mounted onto the existing conveyor stringers.
Motors and gearbox – The geared motors are supplied with a built-in, spring applied, electrical release brake on the rear of the motor. The brake will keep the swing arm in the parked position between 8 o’clock and 11 o’clock. This ensures that the swing arm is kept out of the stream on the conveyor belt. During the sampling action, the motor is energized via a PLC operated timer. The motor is switched off only once the sensor plate has passed the proximity switch.
Sampling Arm – The main components of sampling arm are arm extension, Swing arm with cutter, rubber scrapper, proximity sensor and proximity sensor shield.
2. Belt Feeder
The speed of the belt feeder used in CSU is relatively very slow which is acting as material feeding devices.
3. Crusher
Hammer mill types crusher are generally used in coal sampling unit.
4. Secondary Sampler
It consist of following parts:
Housing – The mild steel housing totally encloses the dividing plate, protecting it from unnecessary corrosion contains dust generation and enclosing all moving parts.
Divider Plate – The divider plate operated continuously rotated vertically through a 360 degree arc. The plate can be activated and de-activated by means of a sequence stop/start operation.
Geared Motor – The speed of the geared motor depends on the diameter of the dividing plate. It is designed to provide a cutter tip speed 0.6 m/sec. The motor shaft is coupled directly onto the hub of the rotating plate. A motor brake is fitted on some units to ensure that the cutter not stop in the path of the incoming feed and is parked in the 12 0’clock position.
Control Panel
5. Collector
It consist of following parts:
Sampling Container – Container is generally manufactured from SS-304 material with a low coefficient of friction, thereby ensuring no hand-up of material. The lid seals are air tight to prevent moisture loss.
Drive – A geared brake motor are used ranging from 0.25 KW to 0.75 KW as per requirement.
6. Screw Feeder / Screw conveyor
They are used to discharged excess coal from secondary sampler to plant conveyor.
Working Principle
The primary sampler consists of swing arm with cutter which rotates one revolution per cycle perpendicular to the coal flow. It cuts a swath through the coal and throws a sample into a chute which directly goes to the belt feeder and this belt feeder conveys the material to the crusher. The material is crushed to reach under screen size and material will pass to secondary sampler through the transfer chute. The sample coal from secondary sampler is finally collected in sampling container and excess coal from secondary sampler is discharges to other plant conveyor through screw conveyor.
Work Involve During Preventive Maintenance of Coal Sampling Unit
Check for any spillage.
Check the cutter for any wear, tightness and obstructions.
Check oil level, oil conditions, oil leakage of gear boxes.
