Document MMnGY9qJqM2oXJJmmjQGzbgvz

HOISTING APPARATUS AND CONVEYORS conveyor and struck a person Workmen should always be warned to place material carefully on a conveyor so that it will nde safely Maintenance precautions Before mainte nance men commence working on a con veyor, they should padlock the main power control in the "off" position The mainte nance foreman should carry the only key to this lock If two gangs work on one con veyor, the foremen of both gangs should each padlock the master switch Areas should be readily accessible so that maintenance men can change the position of pulleys, sprockets, or sheaves to compensate for normal working conveyor stretch and wear If adjustment is required while equipment is operating, moving parts should be thoroughly guarded Belt conveyors The belt conveyor, consisting of an end less rubber, fabric, plastic, leather, or metal belt running over two large pulleys with numerous flat or troughing idler pulleys be tween them to support the belt, is probably the most common type (Fig 18-24) It is used to carry boxes, cartons, bags, and simi lar objects as well as the bulk material to which this discussion is confined Material in bulk form, such as coal, ore, ot sand, passes from the loading hopper into a loading boot above the tail end of the con veyor At the opening in the boot there is a skirtboard at each side of the belt, about an inch above it and 2 or 3 in inside either edge Thus as the material is delivered onto the belt, it forms a mound on the center that is far enough from the edges not to spill off In the simplest conveyor the material is discharged over the pulley at the head end of the conveyor The loading hopper, with its boot, can be mounted on flanged wheels that nde on small railrpad rails, so that the belt can be loaded at any point In some installations, such as over coal bunkers, it may be necessary to discharge the matenal from the conveyor at various places In this case, the belt is raised up and over a large pulley mounted on a mov able tnpper that runs on a track straddling the conveyor. The on-running belt should be guarded for at least 18 in from the points of tan- gency between the belt and the head and tail pulleys and between the belt and the tnpper and hump pulleys If the hazard is out of reach (more than 7 ft above the floor or platform) or close to a wall or other obstruction, no one in the normal course of his dubes should be exposed to it. The fact that the skirtboards of the load ing boot are dose to the upper surface of the belt means that if a man's arm should be caught, the belt could not be raised suffi ciently to allow the arm to nde over an idler pulley under the belt where the arm un doubtedly would be badly mangled There fore, guards should be installed at the sides of the conveyor at the loading boot The points of contact where the wheels of movable tappers roll on the rails also must be guarded Where the operator travels on the tnpper, b platform should be provided for him It should be so located and con structed as to protect him from slipping and falling and to prevent contact between him or his clothing and moving parts To help prevent his falling into the hopper, the platform should have handholds and railings At the conveyor floor above the coal bunkers in power plants, the slot through which coal from the tapper chute is dis charged into the bunker is protected by bars placed across it about 12 in apart at floor level A piece of discarded belting of the required width and length can be placed to cover the slot, and its ends are securely anchored At the tnpper platform are four pulleys that raise this belt vertically so that it passes over the access to the tapper plat form This device not only provides safety, but also seals the slot and thus keeps the dust in the bunker Wherever a man might fall onto a con veyor, a gate or paddle can be suspended as low as practicable above the belt near the head pulley, so that a man's body nding on the belt would automatically pull a stop rope and quickly stop the conveyor On belt conveyors at floor level or on balconies or gallenes, a shield guard or housing should completely enclose each end Cuardrails and toeboards should extend the length of the conveyor To help remove static from belt convey ors, tinsel or needlepoint static collectors can be placed dose to the outrunning sides of the dnve pulleys and idlers, which, along 18-32