Major Components of Conveyor Long Continuous belt Carried on rolls - rollers held by frame Belt wrapped around pulleys at ends Pulleys coupled to gears and motors Peripheral Devices to drop on belt, direct around corner, clean, discharge etc.
How Conveyors Function Material Falls on moving belt that carries it along A continuous haulage system that is not limited by cycles of batch movement Requires a continuous frame and structure before can transport material over route
Significant Variations Belt may ride on a frame with air holes - a compressor blows air under belt. Belt rides on a cushion of air. Rollers wrap belt entirely around material - used to allow vertical conveying of material
Conveyor Belting Parts Carcass - woven fabric or material for tensile strength Skims - rubber layers between carcass plys Braker - fabric coat above carcass to break impact of load Top Cover - A rubber that resists cutting abrasion and sometimes chemical action
Conveyor Belting Types Multi-Ply - multi-ply carcass separated by skims - traditional - trade-off between stiffness and strength Reduced Ply - complex interwoven carcass not dependent on separate plys thinner less stiff for same strength Steel - carcass lengthwise steel belts - high tensile strength - heavy ores long runs Solid Woven - Carcass impregnated with elastomer
Conveyor Belting Elastomers Most Elastomer Covers in Mining for bump and abrasion resistance - good natural or synthetic rubber Oiled Stoker Coals may need chemical resistance - neoprene rubber Hot process Ores may need heat resistance - check the carcass too - usually limit to 75% of rated
Conveyor Belting Splices Mechanical –Fast –Done by Hand –Easily done and undone (even when don’t want it undone) –collects dirt looses strength Vulcanized –Needs big machine and time –Once done hard to undo –Provides Superior Strength
Idlers Supports Belt and Material Load Built with –Shaft surrounded by bearings –Then roll of steel or rubber Two main types –Carrying for material and belt –return supports belt on return trip
Idler Size and Duty Rated by Diameter –ranges 4 to 7 inches –smaller is less costly but higher wear and frictional losses –5 inches common for mining Rated by Weight Carriage –ranges A to E for increasing duty –A and B light C and D heavy duty E extra –B and C common for mining
Carrying Idlers Usually troughed with 3 equal size rollers on a frame in mining applications –Some suspended catenary systems have 5 rollers Troughs usually 20, 35, 45 degrees –Deeper trough more volume –Requires thinner belt to lay in trough which limits strength –35 common choice for mining
Return Idlers Usually Flat and one piece Sometimes two piece V for belt training Spiral roll to self and belt clean
Specialty Idlers Impact Idlers for taking material dropping onto belt Belt Training (Training means keeping in line in trough) –Can put idler off center to pull to side –Can put wheels on edge but wear belt –Can put v return to pull one way or other.
Pulley Like Roller only belt wraps around Head Pulley - turns belt back around to return - may be coupled to drive Tail Pulley - turns empty belt around for loading - occasionally coupled to drive Drive Pulley - Coupled to motor pulls belt - usually special grip surface
Pulleys Snub Pulley - usually used to change direction of belt and increase the contact angle with the drive pully (more surface area to transfer power) Take Up Pulley - Used to maintain tension on a belt left loose enough for some flexibility
Drive Pulley Considerations Pulley should be large enough to avoid to hard bend at point of tension application Pulley should have grab - risk of slippage is function of grab and tension - more grab - less tension - could mean a cheaper belt Place Drive in practical location to minimize the highest tension in the belt - a head pulley location often good on a belt up a slope
Loading a Conveyor Belt Need to get even load on belt and get material traveling in same direction to minimize belt strain Chute - may use scalping bars so fines fall on first and provide cushion Transfer Conveyor - wear on short replaceable belt get things up to speed Vibratory feeder
Loading a Conveyor Belt Skirt board along edge for about 8 to 10 feet to keep material on belt and line it up Loading points or transfer points are common spill locations –Production rate is not really constant –Simulation programs can aid in determining speed and belt size for network.
Unloading a Belt Over the end of belt –Flatten to fast and stretch the belt –Flatten to slow material will spread and spill over sides –for 35 degree trough need about 1.5 times belt width to flatten Often have brushes to belt after material discharge
Unloading a Belt Plow - V on belt pushes off to sides. –Limited speed about 200 fpm –Need flat belt Tripper - moving plow to one side –can trip from one conveyor to another –good for loading multiple silos