Importance of Wire Rope Lubrication and Discard Criteria

This safety alert outlines the importance of wire rope lubrication and the main criteria used to discard passenger lift wire ropes. Wire ropes bend and straighten when the lift is in operation resulting in relative movement between wires in strand, strands and core in wire rope, as well as between wire rope and sheave groove and pulley. Losses due to friction during operation can be minimised by effective and regular lubrication.

Application of correct lubricant should be carried out periodically to ensure adequate lubrication. Insufficient lubrication can cause corrosion, abrasive wear, and stiffening of the wire rope. In corrosive environment, additional care and attention is vital. Sufficient lubrication also reduces fatigue because it allows smooth movement between wires. The fibre core should never be allowed to become dry, in order to avoid abrasive wearing to occur between strands and core. If this state continues over a considerable period of time, the core could no longer support the strands. Lubrication with grease also only masks the issue and not addressing the real problem.

The frequency of lubrication depends on several factors such as type of lift service, speed of wire rope, environmental and temperature conditions. Inspection should be carried out to establish the frequency of lubrication. Appropriate lubrication methods should be used to avoid excessive lubricant being applied onto the surface of wire rope. Excessive lubricant may reduce traction.

Discard of wire rope is indispensable in order to ensure the safe operation of lift. Several wire rope discard criteria are as follows:

1. Maximum number of broken or cracked outer wires;
2. Maximum percentage of allowable wear on outer wires;
3. Mechanical damage, excessive wire rope elongation or other incongruity form of wire rope caused by fracture of a strand;
4. Maximum percentage loss of the breaking strength and a consequent reduction in safety factor; and
5. Extreme corrosion.

Further information on the lubrication and discard criteria used for the wire rope can be sought from the References.

References

1. Howkins RE. 1998. Lift Modernisation Design Guide. Elevator World.
2. Janovsky L. 1999. Elevator Mechanical Design, 3rd Edition. Elevator World.
3. Schunemann W, Vogel W, Barthel T. 2009. Steel wire ropes for traction elevators: Part 1-3. www.elevatorbooks.com.