ALL BELT CONVEYORS ARE SUPPORTED BY FREE BEARINGS 1. DRIVE PULLEY, 2. NON DRIVE PULLEYS 3. ROLLERS IN CARRYING AND RETURN SIDE

BELT CAN MOVE DUE TO GRAVITY AS IN CASE OF A TREAD MILL

DEPENDING ON THE ANGLE WITH HORIZONTAL LINE, CONVEYORS CAN BE DIVIDED IN 3 TYPES

1. HORIZONTAL CONVEYOR BELT IN HORIZONTAL CONVEYOR WILL NOT MOVE IF POWER TO MOTOR IS OFF

WHEN THE POWER TO MOTOR IS SHUT, THE BELT WILL ROLL BACK

IF POWER TO MOTOR IS SHUT, MOMENTUM OF THE LOADED BELT INCREASES AND BELT SPEED WILL ACCELERATE TILL IT GETS UNLOADED TO THE MAXIMUM. CONVEYOR 1017 OF 10&11A PROJECT SLOPE : 11 DEGREES

IF THE BELT IS EMPTY, WEIGHT OF CARRYING SIDE AND RETURN SIDE BELT IS EQUAL AND THUS THE BELT WILL NOT MOVE EVEN AFTER POWER TO MOTOR IS WITHDRAWN.

IN CASE OF HORIZONTAL AND INCLINED CONVEYORS DRIVE IS REQUIRED TO START AND RUN THE CONVEYOR

IN CASE OF DOWNHILL CONVEYORS DRIVE IS REQUIRED FOR INITIAL STARTING AND THEN ONLY FOR CONTROLLING THE SPEED IF POWER TO MOTOR IS SWITCHED OFF CONVEYOR ON LOAD WILL START OVERSPEEDING

BAD EFFECTS OF OVERSPEEDING OF DOWNHILL CONVEYOR: 1. SAFETY HAZARD TO PERSONNEL & MACHINE 2. OVERLOAD ON SUCCEEDING CONVEYOR 3. OVERTENSION/STRETCH ON BELT JOINTS ( JOINTS BECOME WEAK) 4. DAMAGE OF MAJOR COMPONENTS LIKE GEARBOX, MOTOR, PULLEYS, COUPLINGS, BRAKE UNIT AND STRUCTURE ETC. 5. ALL THE ABOVE WILL LEAD TO PRODUCTION LOSS

1) AIR BRAKE 2) HYDRAULIC BRAKE NORMALLY IN VEHICLES EVERY POSSIBILITY OF HUMAN ERROR OPERATOR WILL USE HIS INTELLIGENCE AND SKILL AND THEN APPLY BRAKES.

a) ELECTRO MAGNETIC BRAKE b) ELECTRO HYDRAULIC BRAKE (THRUSTER OPERATED) THE BRAKES WILL EITHER OPEN OR CLOSE WITHOUT ANY PARTIAL ENGAGEMENT.

POWER OPERATED BRAKES IN CONVEYORS ARE APPLIED WITHIN FEW SECONDS (SAY 3 TO 4 SECONDS) BECAUSE OF DESIGN. LOT OF BRAKING TORQUE IS REQUIRED LOT OF SHEARING AND BENDING FORCE ON ALL COMPONENTS LIKE BELT, MOTOR, GEARBOX, PULLEYS ETC.

THAT IS WHY SUDDEN BRAKE NOT ACCEPTABLE BRAKES NEED TO BE APPLIED SLOWLY MANUAL BRAKES ARE APPLIED DEPENDING ON SITUATION, NORMALLY AFTER REDUCING SPEED

POWER OPERATED ELECTRO MAGNETIC AND ELECTRO HYDRAULIC BRAKES CANNOT BE USED SLOWLY. RETARDATION NOT POSSIBLE ALTERNATE IS:

SPEED IS REDUCED ELECTRICALLY AND THEN BRAKE IS APPLIED WHEN THE POWER TO MOTOR IS CUT OFF AFTER 1.2 SECONDS REVERSE POLARITY IS FED IN TO STATOR FOR A PERIOD OF 4 SECONDS WITH HELP OF A SEPARATE ELECTRICAL PANEL FOR THE PURPOSE.

MOTOR WILL TRY TO ROTATE IN REVERSE DIRECTION FOR 4 SECONDS. WITH THIS MOTOR SPEED REDUCES TO 60% OF ITS FULL SPEED. TILL THEN BRAKE IS NOT COMING IN WAY AFTER 4 SECONDS THE REVERSE POLARITY TO THE STATOR IS WITHDRAWN THEN BRAKE APPLIED IN ABOUT 3 TO 4 SECONDS. TOTAL TIME TAKEN TO STOP CONVEYOR IS ENHANCE TO ABOUT 8 SECONDS STOPPING OF CONVEYOR IS SMOOTH INITIAL COST MORE THAN THE NORMAL BRAKES

DISADVANTAGE: 1. IN CASE OF POWER FAILURE PLUG IN TYPE BRAKE WILL NOT FUNCTION (BUT UPS CAN BE PROVIDED) 2. IN CASE OF ANY PROBLEM IN PANEL EVERY POSSIBILITY OF CONVEYOR RUNNING IN REVERSE DIRECTION AND CAUSE DAMAGE TO THE SYSTEM. NEXT ALTERNATE IS:

BRAKE SYSTEM IS VERY INTELLIGENT COMPLETE BRAKE IS CONTROLLED BY PLC BASED ON LOGICS

WORKING CAPACITY OF CONVEYOR: 2000 TPH LENGTH OF CARRYING SIDE BELT: 2000 MTRS BELT SPEED :180 MTRS/MINUTE IF BELT STOPPED ON LOAD LOAD ON THE BELT: 365 TONS

BRAKING SEQUENCE: 1. BRAKING COMMAND IS RECEIVED 2. INPUT POWER TO MOTOR IS WITHDRAWN 3. UP TO 1.2 SECONDS BRAKE PADS ARE ALLOWED TO COME NEAR BRAKE DISC BUT NOT ALLOWED TO TOUCH 4. AT 1.4 SECONDS 70 VOLT, 100A DC IS FED IN TO STATOR (IN TWO PHASES) THROUGH UPS MAGNETIC FLUX WILL OPPOSE THE DIRECTION OF ROTOR 5. SPEED REDUCED TO 60% OF THE FULL SPEED.

6. AT THIS POINT OF TIME BOTH DC AND HYDRAULIC BRAKE PADS WORK TOGETHER BRAKE PADS COME CLOSER AND GO BACK THROUGH PLC. 7. THE SPEED OF MOTOR REDUCED TO 40% OF FULL SPEED. 8. AT THIS MOMENT THE DC IS WITHDRAWN AND ONLY HYDRAULIC BRAKE IS APPLIED AND THE SPEED BECOMES ZERO 9. TOTAL TIME TAKEN TO STOP THE CONVEYOR IS FROM 17 TO 19 SECONDS. VERY SMOOTH BRAKING OPERATION

INITIAL COST IS VERY HIGH RUNNING COST IS HIGHER THAN THE NORMAL BRAKES AND PLUG IN TYPE BRAKES RISC OF FAILURE IS NEGLIGIBLE

ALL THESE TYPE OF BRAKES WILL WORK ONLY WHILE STARTING AND STOPPING OF CONVEYORS NO CONTROL DURING RUNNING

TO OVERCOME:

VARIABLE VOLTAGE VARIABLE FREQUENCY DRIVE SPEED IS ALWAYS UNDER SPECIFIED LIMIT

4 BRAKES IN CON. 121

DOUBLE BRAKE IN CON. 118

SINGLE BRAKE IN CON. 414

COMPARISON OF CONVEYORS IN DONIMALAI. CON. NO CENTRE LENGTH CAPACITY (TPH) WEIGHT ON THE BELT NO OF BRAKES FAILURES MTRS TONS2NIL MTRS TONS4NIL MTRS TONS1VERY OFTEN

FAILURES OF 414 BRAKE AND DRIVE INCLUDING BELT SNAP: CONVEYOR 414 WAS COMMISSIONED IN 1980 THERE WERE MORE THAN 20 MAJOR BREAKDOWNS SINCE INCEPTION WHICH HAVE TAKEN MORE THAN 3 DAYS EACH TIME FOR RESUMING PRODUCTION: FAILURES LIKE: 1)BRAKE UNIT 2) MOTOR 3) GEARBOX 4) BELT SNAP

VALLEY DUMP WAS EARLIER POSSIBLE AT PRESENT WHOLE PRODUCTION ACTIVITY IS STOPPED IN CASE OF ANY BREAKDOWN IN FINE ORE SECTION

BRAKING TORQUE IS MORE IMPORTANT THAN TORQUE DURING RUNNING CONVEYOR 414 INPUT SHAFT DIA : 60MM CONVEYOR 118 AND 121 SHAFT DIA: 120MM SHAFT DIA IS JUST DOUBLE IN 121 SQUARE AREA OF SHAFT: CON. 414: 3.14 X 60 X 60 = SQ.MM CON. 118: 3.14 X 120 X 120= SQ. MM CON. 121: 3.14 X 120 X 120X2= SQ.MM CAPABILITY OF BRAKING TORQUE IN 118 IS 4 TIMES AND IN CON. 121 IT IS 8 TIMES

THERE IS NEED IN INCREASING SHAFT DIA AND DRIVE CAPACITY IN CONVEYOR 414 ALONG WITH MODIFICTION OF BRAKE DESIGN.