Because the lubricant applied during manufacture is consumed. Every pass over a sheave or onto a drum makes the individual wires slide against each other, and that internal friction is a principal cause of rope degradation. Heat, water, load and centrifugal action gradually strip the original core lubricant away. Dressing in service replaces it, reduces internal wear and protects against corrosion, and on well-maintained equipment it extends rope life substantially.

A penetrating dressing is thin and usually carried in a solvent so it can wick between the wires and strands into the core, where the internal wear occurs; the carrier then evaporates and leaves lubricant behind. A coating dressing is heavier, often wax or asphaltic based, and forms a barrier on the outside of the rope against water and abrasion. They address different problems and are commonly used together.

Usually yes, and in that order: penetrate first so lubricant reaches the interior of the rope, then coat to seal the exterior against moisture. Applying a heavy coating first traps the rope's condition beneath it and prevents any later penetrating product from reaching the core. Where only one can be used, choose the penetrating type, since internal wear is the failure mechanism a surface coating does nothing to address.

Yes, and this is a genuine safety issue rather than a housekeeping one. Lifting ropes are subject to statutory periodic examination for broken wires, corrosion, deformation and diameter reduction, and a thick opaque dressing can conceal all of them. Clean the rope and inspect it before dressing, apply only what is needed for protection, and use a product and quantity that leave the rope's surface condition assessable at the next examination.

On short ropes, by brush, swab or spray with the rope moving slowly, applying to the section entering a sheave where the strands open slightly and accept lubricant. On long ropes and continuous operations, pressure lubricators that seal around the rope and force dressing into the core are far more effective and much less wasteful. Apply to a clean rope, and contain and collect the excess rather than letting it fall.

It should be. Incompatible products can emulsify, harden or fail to mix with the manufacturing lubricant already in the core, which reduces rather than restores protection. Check the rope manufacturer's recommendation, which is normally stated for the rope type, and keep to one product family once a rope is in service. Changing dressings mid-life is a decision to take deliberately, not by whatever happens to be in stock.

It depends on duty, environment and exposure rather than on a fixed calendar. Ropes working in water, steam, abrasive dust or corrosive atmospheres need dressing far more often than those in clean, dry service. Set the interval from inspection findings: dryness, discoloration, surface rust and stiffness all indicate the reserve is depleted. On critical lifting equipment, tie the schedule to the examination regime so dressing follows inspection rather than preceding it.