Hoist drum / rope ratios

(1) The ratio of the diameter of a hoist drum to the rope diameter shall be– (a) equal or greater than 60 to 1 for a drum hoist where the nominal rope diameter is 26 mm (1 in.) or less; (b) 80 to 1 where the nominal rope diameter is greater than 26 mm (1 in); (c) 48 to 1 for a shaft sinking drum hoist where the nominal rope diameter is less than 26 mm (1 in); (d) 60 to 1 where the rope diameter is greater than 26 mm (1 in); (e) 80 to 1 for stranded ropes on a friction hoist; and 100 to 1 for locked coil ropes. (2) A hoist shall not be used to transport persons in a shaft unless it has two sets of mechanical brakes Hoist brakes. 144 (a) that are each capable of holding the drum when the conveyance is carrying its maximum permitted load; (b) that are so arranged that they can be independently tested and be equipped with a device to indicate tread wear or slack linkage and also prevent movement of the hoist if predetermined wear limits are exceeded. Arrangement of hoist brakes. (3) A hoist’s mechanical braking system shall be so arranged that the brake is applied by a control lever that is pulled, unless– (a) there is a common brake and power lever, where brake weights are installed; (b) they can be readily tested to ensure freedom of movement, and at least one set of brakes is applied automatically if there is a loss of power. Braking (4) The brakes of a drum hoist shall be designed and arranged to decelerate the drum at between 1.5 and 3.7 meters (5 and 12 feet) per second when braking is initiated by an interrupted circuit and the hoist is operating in the normal full speed range. Foot brakes (5) No hoist shall be equipped with a foot-operated brake. Fall-safe electrical supply to hoists. (6) All electric hoists shall be equipped with a fall-safe, protective electrical circuit operating at a nominal potential not exceeding 250 volts which, when interrupted, will cut off the power supply to the hoist and actuate the mechanical brake. Electrical safety circuit interruption. (7) The safety circuit of an electric hoist shall be interrupted whenever145 (a) there is a failure of the power supply or a significant drop in voltage that would affect the hoist operation; (b) there is an abnormal overload on the hoist motor; (c) there is a short circuit in the hoist electrical system; or (d) a prescribed safety device has operated. Emergency stop switch. (8) An emergency stop switch, arranged to interrupt the safety circuit of an electric hoist, shall be located within easy reach of an operator controlling the hoist, and the switch shall be easily identified and operated by hand. (9) A track limit switch shall be installed in each shaft hoisting compartment, above the normal upper limit of travel, and so arranged and positioned that in the event of an overwind contact with the conveyance it shall interrupt the hoist safety circuit and bring the conveyance to a safe stop. Track limit switch. (10) Every electric hoist shall be equipped with a device to protect the shaft conveyance against overwinding, approaching a limit of travel at an excessive speed and travelling at speeds in excess of the normal operating speed. This device shallOverwind (a) interrupt the hoist safety circuit when activated; (b) be driven directly by the hoist drum; (c) be protected against loss of motion; (d) prevent the paying out of excess rope during sinking operations; and 146 (e) be set to bring the hoist to a safe stop before the conveyance or rope attachments can reach any permanent obstruction in the shaft or Abnormal slip friction hoist. (11) A friction hoist shall have devices installed which are set to interrupt the hoist safety circuit if– (a) abnormal slip occurs between the hoist drum and the ropes; (b) abnormal wear occurs on the rope treads or the permissible limit of tread wear has been reached; (c) an abnormal swinging or rising occurs in the loop of a balance rope at the bottom of the (There shall also be a device installed in the shaft that detects a conveyance approaching the shaft collar at an excessive speed.) Synchronizing (12) A device shall be installed on a friction hoist to synchronize the position of the shaft conveyance with the safety devices driven from the hoist drum. (13) Every electric hoist shall have the followingAmmeter on (a) an ammeter within plain view of the hoist operator to indicate the hoist motor current; Audible warning (b) except where automatic retardation controls are installed at the limits of travel, a device to audibly warn the hoist operator when the shaft conveyance is at a point in the shaft where manual breaking must be commenced; 147 (c) a speed indicator if the normal rope speed exceeds 2.5 meters (25 feet) per second; Speed indicator. Voltage meter. (d) a device which gives a voltage reading proportional to the speed of the hoist; Backout device. (e) a backout device to enable a shaft conveyance to be removed from an overwound or underwound position and the device shall only be capable of manual operation and designed to prevent the brakes from being released until sufficient torque has been developed to ensure movement in the right direction; Underwind bypass device. (f) underwind and overwind bypass devices arranged so that they are only capable of manual operation and will only allow the hoist to be operated at a slow speed; (g) overwind devices arranged so that they will only allow travel beyond the first device providing overwind protection; Overwind (h) a master controller that has a neutral or brake reset position; Master controller. (i) brake operating levers arranged so that, after any interruption of the hoist safety circuit, power cannot be restored to the hoist unless the brake levers are in the brake-applied position; and Brake lever arrangements. (j) accurate and sensitive safety controllers. (14) A hoist shall be provided with depth indicators that continuously, accurately and clearly show the hoist operatorDepth and other indicators. (a) the position of a shaft conveyance; 148 (b) a change in gradient in an inclined shaft; (c) the overwind, underwind and track limit switches; (d) any collar doors, dump doors or crosshead landing chairs; and (e) the limits of normal travel for the shaft (15) No drum hoist shall haveMaximum layers of rope on drum. (a) more than 3 layers of rope where the drum has helical or spiral grooving or does not have grooving; (b) more than 4 layers of rope if the drum has parallel and half pitch grooving; and (c) no less than 3 turns of rope on the drum when the conveyance is at its lowest possible point in the shaft. Fleet angle for sheave/hoist. (16) A drum hoist and sheave shall be arranged so that the rope coils properly across the face of the drum and winds smoothly from one layer to another without cutting into the rope layer beneath. Interlocking clutch and brake. (17) A clutch of a drum hoist shall be interlocked with the brake so that the clutch can be disengaged only when the brake is fully applied and so that the clutch is full before the drum can be released.