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Understanding Wire Rope Lubricants: Grease or Wax?

Connor Kristensen

Did you know the majority of secondary dressing lubricants are greases but the majority of primary build lubricants are wax… why is that???

Let’s take a look at the performance characteristics, discuss the differences with the two technologies, and the reasons why rope manufacturers may choose to coat with a grease or a wax.

As mentioned in our – ‘Wire rope lubricant selection’ blog we can consider the performance of a rope lubricant in terms of core functionality (corrosion, wear protection, EP performance, heat protection, etc…), secondary features such as, environmental performance, water wash-off, fling-off, UV Resistance and tertiary features like application.

 Core functionality:

  • Wear & Abrasion – every time your rope operates it experiences wire-to-wire contact and given the high operating hours; bend cycle fatigue is a common cause of rope failure. Greases typically have a much lower coefficient of friction than waxes and better lubricity to fundamentally protect against metal-to-metal contact. Using a grease at the build stage, or thoroughly applied as a secondary lubricant, gives the best opportunity for prolonging rope life through reduced metal-to-metal contact. Likewise, wire rope is frequently subjected to forces from other metal parts, (pullies, sheaves, drums, neighbouring rope lengths, etc…), and repeat failures in the same sections can be common. Again, the greater lubricity from grease, over wax, helps alleviate problem spots by limiting metal-to-metal contact and protecting ropes for longer. (Further analysis on any rope failure can help to identify underlying problems and allow for correct measures to be implemented).
  • Shock loading – Many ropes are utilised in lift and transfer operations and despite good operational skills and crane design features, ropes remain exposed to a degree of shock loading. In addition, if time is short and ropes operating under load are moving at a quicker pace, shock loading can increase and the life of a rope can shorten. With the addition of additives, greases can offer better extreme pressure (EP) protection and present it uniformly, mitigating the impact of shock loading across every section of your rope.
  • Corrosion – Can be a readily diagnosed and a common rope failure mode. Wire Ropes are frequently found in marine environments; on ships, ports, offshore O&G, offshore energy, etc…, while rope design can inadvertently lead to entrained contaminates and corrosive salts. Greases are more likely to remain semi-fluid, continually fill voids within a rope, and provide a physical barrier on all surfaces it contacts, while the inclusion of corrosion inhibitors also provides a chemical barrier for prolonging rope life with noticeable benefits in even a short period of time. Waxes on the other hand, while they can form an initial firm barrier, they are susceptible to cracking, allowing water and corrosive components to ingress which are then retained and rapidly lead to rope failure from within.

 Secondary features:

  • Worked Stability – Greases are more likely to show better stability over waxes when worked, providing the same level of protection across a wider operating window and protect your rope for longer. A wax, while firm on first introduction, can soften under worked conditions and offer limited performance within a short timeframe.
  • Temperature Stability – a major issue with waxes is their limited temperature stability. While this assists the rope manufacture with application, it does mean even slight temperature rises can be detrimental in the field, where even the ambient temperature in some warmer climates can be too much and wax can be seen physically dripping from the rope. Greases can offer a wide operating temperature range to limit losses in the field and be less susceptible to cold temperatures, protecting your ropes across much wider temperature ranges.
  • Rope storage – As a grease can remain ‘semi fluid’ for much longer and not dry out like a wax, the storage of finished ropes can be extended without compromising quality.
  • Eco/Bio – With grease formulations it’s much easier to be Eco-friendly and achieve VGP (Vessel General Permit) compliance while not compromising on performance. They are also non-bio-accumulative and non-hazardous to aquatic life.
  • Operator Safety – Greases are also easier to formulate as non-toxic and non-hazardous allowing operator safety when handling, storing and manufacturing ropes. It is the employer’s responsibility to control substances hazardous to health including providing control measures to reduce harm to health.
  • Retention – Lubricant and coating performance is only useful if the product is retained on the rope and while a wax is firm on initial introduction, providing a physical barrier, they offer very little movement through the rope and are quickly susceptible to failure and loss leaving unprotected areas for contaminant ingress and metal-to-metal contact (fret-fatigue). As waxes break down, the firm outer coating can actually act to retain contaminates and expediate rope failure from within. Grease design provides more options to tailor towards specific needs such as marine environments, submerged ropes and extreme temperatures. A grease is also more likely to remain semi-fluid, malleable and able to self-repair as it migrates into exposed areas under normal rope running conditions.
  • Compatible dressing lubricants – As waxes set firm, they are difficult to remove if they remain present in any significant quantities which makes protection replenishment difficult without the aid of heat or solvents (difficult to handle, transport, store), which can inadvertently damage the integrity of your rope. As greases are likely to remain semi-fluid the addition of added protection through regular replacement is much easier and prolongs the rope life way beyond that seen from wax alone.

Tertiary features:

  • ApplicationRope coatings have historically developed around waxes, with the wax heated to a water like consistency and poured over the strands at closing during manufacture. This allows the rope manufacturer to provide some level of core functional protection. It also means initial pricing can be kept low, given the minimal price per kg for waxes and the availability of existing wax handling equipment. Although grease costs are typically higher than a wax, this generally accounts for <1% of the overall cost and, as outlined above, a grease can offer much greater protection to the rope, whilst also enabling the ability to ‘top-up’ protection throughout the rope lifecycle via secondary dressing lubricants. In addition, with the introduction and greater use of pressurized lubricators, the use of a grease at manufacturing is becoming much more common place.

RS Clare’s Wire Rope ClareGuard range has been developed with full rope protection in mind to maximise your rope life. The range comprises of several build (primary) products that provided a high level of extended protection from day one of manufacture, through storage and use, giving your rope the best opportunity for a longer life in the field. Followed with a range of compatible dressing or secondary lubricants to maintain this level of protection and extend your rope life further.

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