twisted the same way. Lang lay ropes are said to have better fatigue resistance due to the flatter exposure of the wires.

Wire ropes are made mostly from high carbon steel for strength, versatility, resilience and availability and for cost consideration. Wire ropes can be uncoated or galvanised. Several grades of steel are used and are described in Table 1.

Figure 2: Foam Penetrating Type Wire Rope Table 1: Tensile strength of wire rope materials

Steel cable wire is stiff and springy. In non-preforming rope construction, broken or cut wires will straighten and stick out of the rope as a burr, posing a safety hazard. A preformed cable is made of wires that are shaped so that they lie naturally in their position in the strand, preventing the wires from protruding and potentially causing injury. Preformed wire ropes also have better fatigue resistance than non-preforming ropes and are ideal for working over small sheaves and around sharp angles.

Wire Rope Lubrication Lubricating wire ropes is a difficult proposition, 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 consider carefully the issue of field re-lubrication when selecting rope for an application.

Wire rope lubricants have two principal functions: 1. To reduce friction as the individual wires move over each other.

2. To provide corrosion protection and lubrication in the core and inside wires, and on the exterior surfaces.

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

Both types of wire rope lubricants are used. However, because most wire ropes fail from the inside, it is important to make sure that the center core receives sufficient lubricant. A combination approach in which a penetrating lubricant is used to saturate the core, followed with a coating to seal and protect the outer surface, is recommended. Wire rope lubricants can be petrolatum, asphaltic, grease, petroleum oils or vegetable oil-based (Figure 3).

lubricate each strand (Figure 2). Coating lubricants penetrate slightly, sealing the outside of the cable from moisture and reducing wear and fretting corrosion from contact with external bodies.

Figure 3: Grease Lubed Wire Rope

Petrolatum compounds, with the proper additives, provide excellent corrosion and water resistance. In addition, petrolatum compounds are translucent, allowing the technician to perform visible inspection. Petrolatum lubricants can drip off at higher temperatures but maintain their consistency well under cold temperature conditions.

Asphaltic compounds when used as a coating generally dry to a very dark hardened surface, which makes inspection difficult. They adhere well for extended long-term storage but will crack and become brittle in cold climates.

Various types of greases are used for wire rope lubrication. These coating types penetrate partially but usually do not saturate the rope core. Common grease thickeners include sodium, lithium, lithium complex and aluminum complex soaps. Greases used for this application generally have a soft semi-fluid consistency. They coat and achieve partial penetration if applied with lubricators such as the Viper Wire Rope Lubricator.

Continued on page 12 LUBE MAGAZINE NO.152 AUGUST 2019 11

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