Finished Lubricants

Hanging by a Thread?


Wire ropes are found in a number of heavy industrial lifting applications, from elevators to ski lifts, ships cranes and mining draglines to drilling rigs, construction hoists and mooring lines, to dredgers, suspension bridges, dam gates and more. According to U.K.-based Bridon Group, the worlds largest wire rope producer, global production of wire rope amounts to around 3.0 million metric tons each year.
Woven from galvanized, bright or stainless steel, wire ropes can expect to face deteriorating conditions throughout their lifetimes, such as extreme pressures and shock loads, strong weather, temperature extremes, corrosion and rust.
Indeed, each time the ropes bend or flex, the internal strands of the braided rope grind together creating friction. While most ropes are sold prelubricated, this factory-applied coating may not last through the lifespan of the rope, and without treatment eventually there will be corrosion and rust.
If not discovered, the hidden damage can lead to tragedy, such as seen two years ago on the cruise ship Thomson Majesty. Five crew members were killed during a safety drill when wire ropes snapped and dropped their lifeboat 65 feet into the sea. Marine investigators later found the ropes inner strands were dry of lubricant and severely corroded inside, which routine monthly inspections had missed.
Wire ropes have a number of components. First, there are the individual steel wires – many of which make up one strand. Varying numbers of these strands are then wrapped together tightly around a supportive core to form the rope; more layers of strands may be added to build strength and fatigue resistance. At the center is the core, made of either fiber (for flexibility) or steel (for strength) and usually impregnated with a lubricant during manufacturing.
Many applications demand regular replacement of the ropes. For example, a 2005 study involving BHP Billiton found the Australian mining giants dragline ropes averaged just 10 weeks of service, and hoist ropes survived about 30 to 35 weeks; some hoist ropes lasted just five weeks in operation. That study concluded that wire ropes accounted for 10 to 15 percent of total maintenance costs at mines, and consumed $300,000 per machine per year.
Aside from the cost of leaving ropes in disrepair and shortening their usable life, improperly serviced wire ropes also pose a significant safety hazard, as kinked and frayed wire strands can be abrasive and sharp, or, as on the Majesty, can give out with little warning. Where industrial users have recognized the benefits of maintaining these expensive products, demand has grown for wire rope lubricants that can be applied in the field.
Essentially, lubricants for wire ropes perform two main functions: They reduce the amount and intensity of friction when the strands touch, and they protect against the weather and other environmental elements that would lead to corrosion. Filling this need is a niche industry devoted to creating and supplying lubricants specifically designed to prolong the lifespan of these costly wire ropes.
There are several approaches and treatments for wire ropes. For example, some products work as penetrating lubricants that bring the lubricant into the inside of the rope and cover each strand. This type of lubricant works to prevent against ropes wearing down from the inside – which is the most common type of wear.
Another common type of wire rope lubricant is coating lubricant, which only penetrates the rope slightly and works to create a seal on the outside of the rope, thus preventing corrosion and prolonging shelf life. Of course, these lubricants are not mutually exclusive and sources say the best protection for wire ropes is a combination of penetrating and coating fixes, at work on both the interior and exterior of the wire strands.
One company that has experience in this field is the Texas-based company Whitmore Manufacturing, which produces both coating and penetrating lubricants for its clients. Whitmores manager of technical services, Tom Muckian, spoke with LubesnGreases and indicated that, while the company has consolidated all of its operations in Rockwall, Texas, Whitmore exports wire rope lubricants all over the world, especially to mining clients in Australia.
Most of the lubricants go onto draglines and shovels in the mining industry, but we also have some that are used in marine applications, Muckian revealed. With regard to mining sheaves, Whitmore estimates that, with proper maintenance and lubrication, clients could prolong the life of their wire ropes by an additional 25 percent and also save nearly $80,000 per year in repair costs. Even greater savings will come from avoiding the downtime needed to remove and install the new hardware, he said.
Ironically, wire rope lubricants have been a declining part of Whitmores business over the past few years. Muckian noted that the sale of these products has dropped from the largest area of sales to almost nothing (in terms of sales revenue). This highlights an interesting trend: Wire rope manufacturers increasingly offer products that are prelubricated at higher and more sustainable levels. Moreover, Muckian says some large end users and prospective clients (such as large mining outfits) are opting to simply discard their used wire ropes – ostensibly for safety concerns – rather than pay to have them relubricated.
Lubrication Engineers Inc., based in Fort Worth, Texas, also focuses on this market space. LE offers both penetrating and coating lubricants and specializes in developing products that are environmentally friendly, such as its Low Tox Penetrating Lubricant which is biodegradable and claims a tenfold reduction in toxicity effects, compared to comparable lubricants. Other wire rope products include its coating grease, which is tacky and water resistant and protects against corrosion and wear.
In the field, most rope lubricants are applied by drip, spray or brush, but LE also produces three lines of wire rope lubricators, named the Viper MK II, which automate the relubrication process and prevent the mess and hazard of manual application. The pressurized lubricator looks like a sleeve that is clamped and sealed around the rope. As the rope runs through the sleeve, lubricant is squeezed into the strands. Automatic lubricators are now used on wire ropes on a variety of applications including cranes, anchor cables and bridges.
Jeff Turner, executive vice president at LE, noted that 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.
Turner also has noted cable life cycle and performance are influenced by several factors, including type of operation, care and environment. Cables can be damaged by worn sheaves, improper winding and splicing practices, 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.
Rust and corrosion control is another critical property for wire rope lubricants, especially those used in harsh environments such as mining and saltwater. Wire rope lubricants have to be formulated with strong additives including rust inhibitors, antioxidants, extreme-pressure agents, tackifiers and anti-friction ingredients. The newest challenge is biodegradability, and low toxicity for use around water.
Among the companies playing in the wire rope lubricant space are:
Castrol Marine, which offers Biotac MP, a lithium complex grease based on biodegradable base oils and an optimized performance additive system to impart corrosion protection, oxidation stability and load carrying capability. Biotac MP is fully compliant with the vessel general permit requirements of the U.S. Environmental Protection Agency. The product is aimed at wire ropes, marine mooring and cargo winches, and other marine deck applications.
New Jersey based Bel-Ray Co., also has lately targeted the marine environments where potential contamination is a primary concern. With the EPA now regulating all lubricants that may come in contact with U.S. waters, its Bio-Bel cable and rope lubricant is biodegradable, non-toxic and solvent-free.
Fuchs Lubricants, the worlds largest independent lubricant manufacturer, also has a significant stake in the wire rope lubes market, which has only grown since the 1991 acquisition of mining lubricant specialist Century Oil. Like its competitors, Fuchs has been focusing on environmentally acceptable lubricants; other key targets industries are elevators, surface mining, drilling and construction cranes.
The Texas-based Kirkpatrick Group also focuses on environmentally friendly lubricants for wire ropes and as well as a variety of lubricant applicators. Kirkpatrick supplies a range of clients including the U.S. Navy and Coast Guard, and the navies of Canada and Australia. Other Kirkpatrick systems can be found in service for shipping, mining, offshore construction and oceanographic research.
Kirkpatrick produces three types of wire rope lubricants in its Dynagard series, including versions designed for severe weather conditions which need reliable water resistance. The products slickness and viscosity allow it to stay alive with the wire rope as the strands move during load-bearing operations, which serve to continuously redistribute the lubricant to cover any internal strand areas that may have been missed during the initial lubrication process. Kirkpatrick also produces pressurized systems to apply the lubricants.
Whether lubricants are applied manually or automatically, they are critical for wire rope maintenance. As the BHP study emphasized, rope life can be shortened by 40 percent to 50 percent if ropes are not lubricated beyond what is applied during manufacture.