Maybe, but manufacturers will have challenges to overcome in the years ahead
By Andreas Schmeiss, SVP Global Cranes, WireCo
(photo above: Workers aboard an oil tanker handling LANKO®FORCE ropes from WireCo’s Lankhorst Ropes – courtesy of WireCo)
For all its advantages, fiber or synthetic rope poses important challenges to manufacturers and end users alike in the effort to fully replace steel rope.
In the industrial environment, in which ropes frequently encounter sharp edges and abrasive surfaces, steel is generally impervious, while fibers are susceptible to fraying. Fibers are also sensitive to ultraviolet radiation and excessive heat. High temperatures can cause a condition known as “creep,” in which a rope becomes pliable and stretches to a point beyond its original form. Ultraviolet radiation can degrade the rope filaments, requiring that special coatings be applied to prevent failure.
Retirement criteria are also more difficult to determine with synthetic ropes, where the nondestructive testing methods used to judge the condition of a steel rope are not suitable. Synthetic ropes also tend to be more expensive than steel wire ropes. For the same application, the cost of fiber can exceed that of steel by up to three or four times.
Manufacturers having both steel and synthetic portfolios from which to draw focus on providing customers the optimal solution for a given end use, regardless of the material employed.
In some cases, steel is the clear winner. In other cases, fiber. Advanced coatings might one day tip the balance in favor of synthetics, but, for now, it would be difficult to imagine that fiber rope would fully displace steel any time soon.
Still, a handful of crane OEMs have explored replacing wire rope with fiber. The primary purpose in doing so is to reduce weight without compromising strength, increasingly a concern as lifts become higher, heavier, and more complex.
Synthetic ropes tend to be easier to handle and install, reducing fatigue and the possibility of injury for those who conduct installations, inspections, and changeouts. And, without any need for lubrication, fiber ropes offer environmental benefit.
Fiber lends itself well to static applications, particularly in the maritime environment. These include applications in which ropes are not continually wound and unwound over drums. Common uses include mooring lines for ships, offshore energy platforms, and, more recently, floating wind turbines. Ropes for these applications are transported and installed at sea, making synthetics’ reduced weight, high strength, ease-of-handling, and corrosion resistance the preferred choice over steel.
Boom pendants, used to connect mining shovels’ various extraction and lifting components, represent another static application that lends itself to the use of synthetics. Unlike the steel used in conventional pendants, the fibers act like a shock absorber during digging operations, reducing fatigue-related stresses for both the shovel equipment and those who operate it. This, in turn, could extend the service lives of shovels and draglines by up to three to four times over the lives typically experienced when using traditional steel technologies.
Fiber also has potential for wider use in dynamic applications.
Synthetic hoist ropes have gained wider acceptance for use on ship cranes. The same is not entirely true of mobile cranes, however, where ropes must strike an optimal balance between breaking load and weight. Both the limited axle loads of road-approved vehicular cranes and weight limitations for crawler cranes require that ropes provide a steadily increasing breaking load at a constant diameter.
To meet these requirements, synthetic alternatives must employ special fibers with tensile strengths similar to those of steel.
Lankhorst Ropes’ LankoLift S does exactly that. The bright yellow rope consists of twelve braided outer strands made of high-tech Dyneema and provides a breaking strength equal to that of steel rope of the same thickness. LankoLift’s core is designed to resist transverse pressures, and laboratory tests involving reversed bending cycles have yielded promising results for extended service life. The rope also features a special fiber coating that reduces interior friction and increases ultraviolet resistance.
LankoLift offers low weight, flexibility, and ease of handling during installation and hook block changes. The rope has proven suitable for higher payloads, especially those involving higher lifting heights and longer jib lengths. The low maintenance requirements offer further advantage since synthetic ropes of this type are corrosion-proof and require no further lubrication.
Not all solutions are strictly steel or synthetic. Hybrids can provide the benefits of both in the same rope.
An example is mining rope with a plastic-coated, high-strength fiber core, surrounded by steel-wire strands. This construction provides a high strength-to-weight ratio, as well as resistance to abrasion and bending fatigue for use in underground mining, where shafts have become progressively deeper and weight the limiting factor in hoisting capacity.
As with other applications that favor synthetics, reduced weight is a clear benefit. The same is true of the added durability and reduced creep provided by hybrid ropes.
In terms of downside and factors that would limit wider use, cost is likely the most significant.
As with most things, the choice between steel and synthetic ropes involves tradeoffs. That will continue to be the case for the foreseeable future. Nonetheless, as rope manufacturers and OEM partners work together to close performance gaps between steel and fiber, they drive the type of innovation that benefits the entire industry. Whether the future is all-steel, all-fiber, or some combination thereof, it is bound to be brighter.
Andreas Schmeiss, Senior Vice President, Global Cranes, for WireCo is based in Germany.
WireCo is the world’s leading manufacturer of mission-critical wire rope, synthetic rope and netting, and electromechanical cable. Headquartered in Prairie Village, Kansas, the company has manufacturing facilities, distribution centers, and sales offices on five continents.
This article appeared in the September/October 2022 issue of Wire Rope Exchange