Wire rope forms an important part of many machines and structures, and it is composed of continuous wire strands wound around a central core.
Most of these are steel wires made into strands wound with each other, and the core can be made of steel, rope including plastics.
A number of industries such as mining, chemical, steel, forestry, agriculture, construction, contracting, civil engineering and many others require steel ropes for pulling, dragging and hoisting. As for lubrication of wire ropes there are many choices and these include heavy black asphaltic based, petrolatum, grease, petroleum oils, or vegetable oil based products. From thick tacky grease to thin penetrating and dewatering oils.
Wire Rope Lubricants
Too much grease can lead to splatter under load and too little grease will lead to excessive wear and corrosion and finally the degradation and possible failure of the cable.
There are two types of wire rope lubricants, penetrating and coating. Penetrating lubricants contain a petroleum solvent that carries the lubricant into the core of the wire rope, then evaporates leaving behind a heavy lubricating film to protect and lubricate each strand.
Coating lubricants penetrate slightly, sealing the outside of the cable from moisture and reducing wear and fretting corrosion from contact with external bodies. A combination approach in which penetrating lubricant is used to saturate the core, followed with coating to seal and protect the outer surface, is recommended.
The correct lubrication of wire ropes can safely extend the operational life of the wire rope and in some cases double this life span. Wire rope lubricants prolong the life of wire ropes and they perform far better when they are maintained.
Wire ropes are often exposed to harsh environmental conditions which include adverse weather conditions. Although most wire ropes are lubricated during the manufacturing process, the lubrication will not last the entire life of the wire rope. Most wire ropes fail from the inside out and a corroded wire rope is therefore a safety concern. The correct lubricant prevents deterioration of the wire rope from rust and corrosion.
Cable life Cycle
Several factors determine cable life cycle and performance, and they entail the type of operation, care and environment. Cables can be damaged by worn sheaves, improper winding and splicing practices, including improper storage. In addition, high stress loading, shock loading, jerking heavy loads, 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 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, and humidity and are accelerated by elevated temperatures. However, proper and adequate lubricant application in the field can reduce the 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 the normal operation, creating internal two-body abrasive wear. The outside cable accumulates dirt and contaminants from sheaves and drums, and it causes three-body abrasive wear, which erodes the outer wires and strands. Abrasion usually reduces rope diameter and can result in core failure and internal wire breakage. Hence, penetrating wire rope lubricants reduce abrasive wear inside the rope and also wash off the external surfaces to remove contaminants and dirt.
If a cable is dirty or has contaminants, it must be cleaned with wire brush and petroleum solvent, compressed air or steam cleaner before lubrication. Corrosion can cause shortened rope life due to metal loss, pitting and stress risers from pitting. Wire ropes mostly fail from the inside, it is important to make sure that the centre core receives sufficient lubricant.
Choosing a Wire Rope Lubricant
The main properties of wire rope lubricants, which are usually indicated in the technical characteristic of the product, include the thickener type, base oil type, consistency (NLGI), temperature range, colour, base oil viscosity, viscosity index, dropping point, pour point, flash point and saltwater/ salt spray test and four ball wear test.
Hence, the key performance attributes to look for in a wire rope lubricant are wear resistance and corrosion prevention. Useful benchmark performance will include high four-ball EP test values, such as a weld point (ASTM) of above 350 kg and a load wear index of above 50. For corrosion protection, look for wire rope lubricants with salt spray (ASTM) resistance values above 60 hours and a humidity cabinet (ASTM D1748) values of more than 60 days.
Choose a wire rope lubricant that possesses a good adhesive strength to stick to the cable and is highly water resistant. It is important that the lubricant penetrates between the wires and strands, has a high film strength, resisting oxidation and remaining pliable. The use of a lubricant that contains acids or alkalis should be avoided, and the pH of any degreasing fluid used to clean the wire rope is crucial.
Lubricating wire ropes is difficult, regardless of the construction and composition. Ropes with fibre cores are somewhat easier to lubricate than those made exclusively from steel materials. For this reason, it is important to carefully consider the issue of field re-lubrication when selecting rope for an application.
Operation Costs and Downtime
Due to increasing cost and tightened availability of energy, the opportunity for significant savings in improved lubrication is ever increasing. Energy cost is never part of the maintenance budget, but part of the operating budget. However, documenting energy savings resulting from improved lubrication creates the opportunity to reduce maintenance costs and increase equipment reliability and profitability.
To the maintenance departments, precision lubrication is no-brainer, hence it stands to reason that lubrication excellence is a good investment. To those who do not understand the nuances of lubrication, lithium complex grease thickeners or filtration beta ratios, spending money on lubrication upgrades and improvements is simply another overhead cost. Lubrication can affect equipment reliability-beyond the last catastrophe that shut down production, and lubrication like other costs, should be minimized to help the organization survive the current economic down turn.
SOS Oil: If We Don’t Stock No One Does
SOS Oil, founded by Freddi Stafford more than 20 years ago, specialises in providing high performance lubricants used in the automotive (OEM approved) industry, mining, construction, marine and farming industries as well as specialised lubricants for all types of machinery and equipment within the food industry.
With a range of over 1700 products in their store and access to a further 1800 products, they can satisfy the lubrication needs of a very wide variety of industries. SOS Oil offers products with a world-class reputation for improving performance and productivity, ensuring they do not compromise on quality. With the technical knowledge SOS Oil developed over the past 25 years, they have expanded the boundaries of lubrication science and redefined the performance possibilities of modern machinery and engines. With their technical innovation, commitment to high quality products and belief that consumers will always respond to a superior product, the company has remained as the market leader in the field of technical lubrication.
Give them a call and enjoy the benefits of honest, reliable and passionate suppliers of lubricants, greases and fuel. With over 3500 products available they remain committed to their slogan – if we don’t stock it, no one does.