| Chapter 14 - Koepe/Friction Hoists |
| Number |
Topic |
Rule of Thumb |
| 14.01 |
Hoisting Distance |
A friction hoist with two skips in balance is normally suitable for hoisting from only one loading pocket horizon and for a hoisting distance exceeding 600m (2,000 feet). Otherwise, a counter-balanced friction hoist (conveyance and counterweight) is usually employed (for multi-level, shallow lifts, or cage hoisting). Source: Ingersoll-Rand |
| 14.02 |
Hoisting Distance |
A friction hoist with two skips in balance may be suitable for a hoisting distance as shallow as 400m (1,300 feet). Source: Sigurd Grimestad |
| 14.03 |
Hoisting Distance |
The practical operating depth limit for a friction hoist is 1,700m (5,600 feet) for balanced hoisting and 2,000m (6,600 feet) for counterweight hoisting. Beyond these depths, rope life may be an expensive problem. Source: Jack de la Vergne |
| 14.04 |
Hoisting Distance |
The hoisting ropes (head ropes) for a friction hoist are not required to be non-rotating for depths of hoisting less than 800m (2,600 feet) provided right hand and left hand lays are employed to cancel rope torque effect. Tail ropes must always be non-rotating construction and connected with swivels at each end. Various Sources |
| 14.05 |
Static Tension Ratio |
For a tower-mounted skip hoist, the calculated static tension ratio (T1/T2) should not exceed 1:1.42, but 1:1.40 is preferable. For a ground mounted skip hoist, the calculated static tension ratio should not exceed 1:1.44 but 1:1.42 is preferable. For a cage hoist installation, these values may be exceeded for occasional heavy payloads of material or equipment transported at reduced speed. Various Sources |
| 14.06 |
Static Tension Ratio |
22 years of experience with operation of seven tower mount Koepe hoist installations has taught me that the T1/T2 ratio should be kept below 1.4:1 to avoid slippage and unsafe operation as a consequence. Source: Alex Murchie |
| 14.07 |
Tread Pressure |
Tread pressure should not exceed 17.5 kg/cm2 (250 psi) for stranded ropes and 28 kg/cm2 (400 psi) for locked coil ropes. Source: A.G. Gent |
| 14.08 |
Tread Pressure |
For lock coil hoist ropes, the tread pressure calculated for skip hoists should not exceed 2,400 kPa (350 psi), or 2,750 kPa (400 psi) for a cage hoist when considering occasional heavy payloads of material or equipment. Source: Jack de la Vergne |
| 14.09 |
Tread Pressure |
For stranded hoist ropes, the tread pressure calculated for skip hoists should not exceed 1,700 kPa (250 psi) or 2,000 kPa (275 psi) for a cage hoist when considering occasional heavy payloads of material or equipment. Source: Largo Albert |
| 14.10 |
Tread Pressure |
For flattened (triangular) strand headropes hoisting in balance, a tread pressure up to at least 2,200 kPa (319 psi) seems to be quite satisfactory. Source: Sigurd Grimestad |
| 14.11 |
Tail Ropes |
The natural loop diameter of the tail ropes should be equal to or slightly smaller than the compartment centres. Source: George Delorme |
| 14.12 |
Hoist Wheel Rotation |
The total number of friction hoist wheel revolutions for one trip should be less than 100 for skip hoists, but may be as high as 140 for cage hoists. Source: Wire Rope Industries and others |
| 14.13 |
Hoist Wheel Rotation |
To keep the load distribution between the ropes to an acceptable limit, the number of revolutions of the hoist wheel for one trip should not exceed 125 for any multi-rope friction hoist. Source: Sigurd Grimestad |
| 14.14 |
Hoist Wheel Rotation |
The hoist wheel rotation at full speed should not exceed 75 RPM for a geared drive, or 100-RPM for a direct drive. Source: Ingersoll-Rand |
| 14.15 |
Position |
The distance between the hoist wheel and the highest position of the conveyance in the headframe should not be less than 1.5% of the distance from the hoist wheel to the conveyance at the lowest point of travel. Source: Largo Albert |
| 14.16 |
Position |
At full speed, a time increment of at least ½ a second should exist as any one section of rope leaves the hoist wheel before experiencing the reverse bend at the deflector sheave. Source: George Delorme |
| 14.17 |
Position |
The clearance between the bottom of the conveyance at the lowest normal stopping destination in the shaft, and the top of the shaft bottom arrester (first obstruction) is usually 5 feet. This arrangement ensures that the weight of the descending conveyance is removed from the hoist ropes. Source: Largo Albert |
| 14.18 |
Position |
The tail rope loop dividers are generally placed below the arrester. The bottoms of the tail rope loops are then positioned 10 to 15 feet below the dividers. Beneath this, a clearance of about 10 feet will allow for rope stretch, etc. Source: Largo Albert |
| 14.19 |
Hoist Speed |
Where the hoist line speed exceeds 15m/s (3,000 fpm), the static load range of the head ropes should not be more than 11.5% of their combined rope breaking strength. The (ratio of) hoist wheel diameter to rope (stranded or lock coil) diameter should not be less than 100:1, and the deflection sheave diameter to rope diameter should not be less than 120:1. Source: E J Wainright |
| 14.20 |
Hoist Speed |
The maximum desirable speed for a friction hoist is 18m/s (3,600 fpm). Source: Jack Morris |
| 14.21 |
Hoist Speed |
The maximum attainable speed for a friction hoist that can be safely obtained with today’s (1999) technology is 19m/s (3,800 fpm). Source: Gus Suchard |
| 14.22 |
Hoist Speed |
In North America, the desirable speed for cage service is approximately 2/3 of the optimum speed calculated for a skip hoist for the same hoisting distance. Source: Jack de la Vergne |
| 14.23 |
Hoist Wheel Specifications |
The hoist wheel diameter to rope (lock coil) diameter should not be less than 100:1 for ropes up to 1-inch diameter, 110:1 for ropes to 1½ inches diameter, and 120:1 for ropes to 2 inches diameter. Source: Glen McGregor |
| 14.24 |
Hoist Wheel Specifications |
A ratio of 100:1 (wheel diameter to lock coil rope diameter) is adequate for ropes of 25-35 mm diameter. This should increase to 125:1 for ropes of 50-60 mm diameter. Source: Jack Morris |
| 14.25 |
Hoist Wheel Specifications |
Rope tread liners on the hoist wheel should be grooved to a depth equal to one-third (1/3) of the rope diameter when originally installed or replaced. The replacement (discard) criterion is wear to the point that there is only 10 mm (3/8 inch) of tread material remaining, measured at the root of the rope groove. Source: ASEA (now ABB) |
| 14.26 |
Hoist Wheel Specifications |
On most fiction hoist installations, the maximum tolerable groove discrepancy is 0.004 inches, as measured from collar to collar. Source: Largo Albert |
| 14.27 |
Production Availability |
A friction hoist is available for production for 108 hours per week. This assumes the hoist is manned 24 hours per day, seven days per week, and that muck is available for hoisting. Source: Jack Morris |
| 14.28 |
Production Availability |
With proper maintenance planning, a friction hoist should be available 126 hours per week (18 hours per day). Source: Largo Albert |
| 14.29 |
Spacing |
The minimum distance (design clearance) between a rope and bunton or divider is 5 to 6 inches. This is mainly because the hoist rope vibration is normally 2 to 3 inches off centre; 4 inches is considered excessive. Source: Humphrey Dean |
| 14.30 |
Spacing |
The spacing between head ropes should be 1 inch for each foot diameter of the hoist wheel to get an adequate boss for the deflection sheave. Source: Gerald Tiley |