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and improper storage. High stress loading, shock loading, jerking heavy loads or rapid acceleration or deceleration (speed of the cable stopping and starting) will accelerate the wear rate.


Corrosion can cause shortened rope life due to metal loss, pitting and stress risers from pitting. If a machine is to be shut down for an extended period, the cables should be removed, cleaned, lubricated and properly stored. In service, corrosion and oxidation are caused by fumes, acids, salt brines, sulphur, gases, salt air, humidity and are accelerated by elevated temperatures. Proper and adequate lubricant application in the field can reduce corrosive attack of the cable.


Abrasive wear occurs on the inside and outside of wire ropes. Individual strands inside the rope move and rub against one another during normal operation, creating internal two-body abrasive wear. The outside of the cable accumulates dirt and contaminants from sheaves and drums. This causes three-body abrasive wear, which erodes the outer wires and strands. Abrasive wear usually reduces rope diameter and can result in core failure and internal wire breakage. Penetrating wire rope lubricants reduce abrasive wear inside the rope and wash off the external surfaces to remove contaminants and dirt.


Typical Rope Applications Many types of machines and structures use wire ropes, including draglines, cranes, elevators, shovels, drilling rigs, suspension bridges and cable-stayed towers. Each application has specific needs for the type and size of wire rope required. All wire ropes, regardless of the application, will perform at a higher level, last longer and provide greater user benefits when properly maintained.


Through years of field experience, Lubrication Engineers has found that longer wire rope life can be


obtained by using penetrating lubricants, either alone or when used in conjunction with a coating lubricant. Practical experience at a South African mine suggests that life cycles may be doubled with this approach. At one mine site, the replacement rate for four 44-mm ropes was extended from an average 18.5 months to 43 months. At another mine, life cycles of four 43-mm x 2073 metre ropes were extended from an average 8 months to 12 months.


In another study involving 5-ton and 10-ton overhead cranes in the United States that used 3/8-inch and 5/8-inch diameter ropes, the average life of the ropes was doubled. The author attributes this increased performance to the ability of the penetrating lubricant to displace water and contaminants while replacing them with oil, which reduces the wear and corrosion occurring throughout the rope. A good spray with penetrating wire rope lubricant effectively acts as an oil change for wire ropes.


In these examples, the savings in wire rope replacement costs (downtime, labour and capital costs) were substantial and dwarfed the cost of the lubricants. Companies who have realised the importance of proper wire rope lubrication have gained a huge advantage over those who purchase the lowest priced lubricant, or no lubricant at all, while replacing ropes on a much more frequent basis.


References 1. American Iron and Steel Institute. (1985). Wire Rope Users Manual, Second Edition. p. 5-17, 67-68.


2. (1983). CRC Handbook of Lubrication, Volume 1. p. 193-201. 3. Brewer, A. (1974). Effective Lubrication. p. 236-242.


LINK www.lelubricants.com


14


LUBE MAGAZINE NO.152 AUGUST 2019


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