Mine hoisting ropes
For further information regarding hoisting systems please see the article Mine hoisting systems.
In rope construction, wires around a core form strands and strands around a core form the rope. Ropes are designated by: # of strands x # of wire/strand (e.g. 6 x 27). The strands that surround a core can be in different shapes such as round or triangular, etc.
Cores can be constructed out of multiple types of material. They can be natural fibre core, independent wire rope core, or wire strand core.
The rope lay is the direction the wires go in relation to the direction of rope. The two types of lay in ropes are Lang lay, where the wires are diagonal to the direction of the rope and regular lay, where the wires travel parallel to the rope.
In Lang lay the wires travel diagonal to the direction of the rope axis. In this lay there is greater exposure to any frictional points. This type of lay also provides greater resistance to abrasion and is more flexible. A common problem seen with this rope type is that it untwists during operations. This rope is often used in hoisting and as drum ropes.
In regular lay the wires travel parallel to the direction of the rope axis. In this lay there is good resistance to kinking and twisting and can withstand crushing and distortion. This rope is often used for slings and balance ropes.
There is a convention that is used in determining the direction of the rope. Point the index finger in the direction of the rope with your fist in the place of the drum. If this layout is completed with your right hand than the rope is a right lay and vice versa. If the back of your hand is facing you the rope is in an overwind setup. If the front of your hand is facing you the rope is in an under wind setup. Most drums are constructed for right hand lay use.
Locked and Half-Loocked Coils
These locked and half locked coils are used in situations where higher breaking strength is needed. They also have less frictional wear. They are constructed with the center wires lying straight as opposed to twisted. Then one or more layers of shaped wires surrounds the core with the outermost layer interlocked to some extend depending if it is half locked or completely locked.
Wire Selection Criteria
When selecting wire the purpose of the wire must be examined in order to select the appropriate type. Due to the high use and severity of consequences if the rope should fail the safety factor is usually designed to be around 5. According to the operation resistance to: banding, fatigue, abrasion, crushing, and rotation must all be considered.
- Edwards, F. A. (1992). Chapter 17.5 Hoisting Systems. In SME Mining Engineering Handbook (2nd ed., Vol. 1, pp. 1646-1678). Littleton: Society for Mining, Metallurgy, and Exploration, Inc.
- De Souza, Euler (2010). Lecture 7: Hoisting Systems. In Mine 244 - Underground Mining Course Notes. Kingston: Queen's University.