Time to shine17 April 2017
High-strength synthetic ropes are now being used in multiple crane applications and approval for use by crane companies is growing. Bernadette Ballantyne reports
Manitowoc head of global innovation Dr Sammy Munuswamy believes that, in the 21st century, fibre ropes will usurp wire rope to dominate the lifting market. “I truly believe this is going to happen.
In the 19th century natural fibre rope was used for lifting, tying and handling all over the world.
Then, in the 20th century, the situation changed and wire rope took revenge against the fibre.
In the 21st century it is the time where the fibre rope takes revenge against wire rope dominating the industry,” he says.
His view is not surprising considering that Manitowoc is leading the industry as the first crane manufacturer to offer synthetic hoist ropes in its cranes. Partnering with US high-performance rope manufacturer Samson in 2012, the company began supplying K-100 synthetic ropes to rough-terrain cranes in 2014 and can now offer them to boom trucks, truck mounted cranes and all terrains.
“K-100 was created specifically for use with mobile cranes. The first step in the process was for Samson to learn about mobile crane applications, performance requirements and wear modes. The requirements identified were robust spooling performance, adequate bend-fatigue characteristics, abrasion resistance and chemical resistance,” explains Michael Quinn, business development director at Samson. “We were able to leverage technologies that we already use in other markets, such as mining, commercial fishing, and offshore oil and gas to meet these needs.”
Samson describes the K-100 rope as a proprietary blend of high-modulus fibres, including Dyneema, to produce a rope with strength comparable to wire at similar diameters. The rope has an outer braid that comprises the load carrying portion of the rope. This section is made up of 12 strands, with six twisted in each direction before being braided together to create a torque-neutral construction, which Samson claims eliminates load spin and cabling. The rope has a polyester core. While it does not contribute to the strength of the rope, Quinn says that it provides a firm cross-sectional stiffness that improves the spooling performance and reduces diving.
Regarding strength, K-100 sizing is specified to allow maximum permissible line pull with a 5:1 safety factor for each crane installation. The rope is slightly larger, 1–3mm, in size than the steel wire it is replacing. “Due to the K-100 material construction, it is still compatible with existing sheaves and drum grooves, even at this slightly increased size, and still maintains the 7:1 weight savings,” says Quinn, noting that – unlike traditional synthetic fibres such as polyester and nylon – K-100’s high-modulus construction has low elongation, providing the operator with load control similar to wire.
From Manitowoc’s perspective, Munuswamy says that the development of cranes that use fibre ropes for hoisting is part of a bigger philosophy: designing to optimise the user experience and make the worksite environment a fun and rewarding place. “It is more than a rope; to me, it is an emotional connection between operator and the equipment,” he says. This “emotional connection” is enabled by the easier handling characteristics of synthetic rope, which is not only much lighter, but also does not require the lubrication that its wire counterpart needs.
He says that once customers have had the experience of using their Samson K-100 product they realise just how challenging the wire rope is to handle and are reluctant to put their gloves back on to deal with the traditional product.
“From the operator perspective it makes his job easier. There is less maintenance and easy reeving.
Wire rope is rough and hard, and difficult for operators to reeve. [Fibre rope] is easy because it is smooth and soft.”
Avoiding the handling of oil and grease, particularly in hot climates, is a key benefit and the lightweight nature of the rope means that extra equipment such as forklifts are not necessarily required. Furthermore, some of the issues that affect wire rope during operation such as diving, bird-caging and kinking are not an issue for ductile fibre rope. And the new constructions don’t have the elasticity issues that affect nylon rope.
“Then there are the non-value added activities like downtime for a one to two-hour minimum where the rope has to be inspected, and oil and grease added again periodically. They absolutely don’t have to do this with fibre,” Munuswamy continues.
The K-100 is now in use on 25 job sites on a range of cranes from 40t taxi cranes to 130t rough terrains, as well as all terrains and boom trucks. One of the most recent applications is on a Grove GMK4100L in Sweden where contractor Lambertsson Kran used K-100 on both of the 100t crane’s hoists. It was specifically attracted to the new technology because of the reduced weight, lower maintenance requirements, environmental benefits and the ease of handling.
Munuswamy says that applications such as this show that the market is advancing from the diffusion of innovation phase into early adoption.
Germany’s Liebherr may not yet be offering synthetic ropes with its crane hoists but it is has been working on a product with Austrian wire and synthetic rope manufacturer Teufelberger for more than eight years. “Eight years ago, Teufelberger was looking for a partner in the crane business to bring the idea of fibre ropes on cranes to the market,” says Christof Gstrein, member of the synthetic rope joint-venture development programme at Teufelberger. “Liebherr, at the same time, wanted a partner to develop such a synthetic rope and told us that the partner should be an expert in crane applications as well, because the partner should understand the requirements of the crane business.”
The result of this partnership has been the development of a new product called soLITE, which was introduced to the market at Bauma 2016. This synthetic rope has just 80% of the weight of a wire rope, resulting in an increase of the crane bearing load of up to 200%. Designed for lifting applications on cranes, it has a unique multicoloured jacket specifically designed to simplify visual inspection and reliable determination of the point of discard.
Developing discard criteria is one of the biggest challenges for the high-strength synthetic-rope manufacturers that cannot use the same criteria as those of its wire counterpart. For wire ropes, international standards give clear instruction for discard based on wire breakage. Instead, soLITE uses a clever woven jacket – bound over the core – consisting of a range of fibre types in an array of colours representing different stages of wear. “There is a specific system of how the fibres are arranged. It is a combination of different kinds of fibre material and coating of the fibres, which, through their different and exactly defined wear behaviour, create a clear visualisation of the rope condition,” says Gstrein.
As a last stage, the fibres, once worn through, will reveal the bright red core, signifying the latest possible time for the rope to be discarded. Furthermore, both companies are developing an electronic condition-monitoring solution to enable operators to check that the rope has maintained full load capacity. This is expected to be revealed at Bauma 2019. Manitowoc and Samson’s K-100 solution is non-jacketed and relies on visual retirement criteria where users compare appearance of their rope to a condition chart and rank it from one to four. Rope that is given a four must be replaced.
“We are still in the process of fine-tuning but we will further develop that so that we can link the retirement criteria with life expectancy,” says Munuswamy. In this area Samson says that the inspection and retirement criteria are based on that development for products made from similar fibres and coatings over the past 15 years. “We used that baseline of experience as the starting point for K-100. We then collected and analysed samples during the development and testing phases to modify and validate the correlation between this visual inspection and the remaining rope strength. To date, the field samples of the K-100 product offered for sale have shown results that correlate with lab predictions. We have an ongoing sampling programme to continue expanding upon this data set,” says Quinn.
Since Teufelberger and Liebherr began their partnership, over 50,000m of rope has been manufactured for 150,000 hours of testing and 200 breaking-force tests. “We have done a lot in the past eight years. We had a breakthrough in the construction [of the rope] in 2012 and we started real-life testing on cranes in January 2016, which is going on until 2018.
Our goal is to get soLITE ready for sale in Autumn 2018.” The major launch of soLITE on Liebherr cranes is expected at bauma 2019.
In terms of multilayer spooling, Teufelberger and Liebherr say that soLITE has been proved to spool up to ten layers and 38 windings without problems. Field testing is continuing and Gstrein estimates that the rope is currently being tested on ten different cranes in the field.
Samson, too, says that extensive testing has shown that K-100 performs successfully with numerous combinations of load, speed, boom length and reeving pattern. “Tests were also varied to simulate field scenarios where an operator may have to lift small loads followed by heavy loads. The extremes were tested to ensure that the product would successfully perform in the field. These tests proved successful prior to introduction in the marketplace,” says Quinn.
Interestingly, most of the 25 market applications for K-100 have been retrofitted, which Quinn describes as a straightforward process.
“It takes two to eight hours depending on the size and condition of the crane. The primary need to be addressed is the surface condition of the crane where the rope will contact it, such as the hoist drum, sheaves and boom guides. These often need some level of refinishing to prepare the crane for use of K-100. However, the same sheaves and drums are used,” he says noting that in some cases, wind guards or rollers are installed as a precaution, but this is reviewed on a case-by-case basis.
All of these applications have then had original equipment manufacturer (OEM) approval.
After almost three years in the market, Samson has clearly learned a lot from its experiences and says that there is more value in the use of K-100 than the company had anticipated. This includes the potential for quieter road travel by eliminating the noise created when the steel wire contacts the boom; greater visibility in low-light condition thanks to its distinctive orange colour; and ease of transportation. “K-100 is very valuable when a crane has transport issues due to overweight axle loads, since it is a fraction of the weight of a similar length of steel wire,” says Quinn.
This is not the first time that Teufelberger has produced an alternative to wire rope. The same trend emerged in the forestry industry in 2005, when machinery used for dragging huge trees through woods turned to fibre ropes.
“Engineering and manufacturing a synthetic rope to replace traditional wire is not new for us. We know exactly what a crane operator needs and have knowledge of doing it with fibre rope,” says Helene Leitner, head of marketing at Teufelberger.
The partnership between Liebherr and Teufelberger is currently exclusive, and will continue beyond the major product launch in 2019. However, Teufelberger declined to reveal how long the exclusivity will last for.
“Considering the complete lifetime, soLITE is more economic for many crane applications and the weight is a big advantage. We are sure that wire ropes will continue to be the right technology for some applications and that is why we are in a lucky position to have both technologies.”
Looking ahead, Samson says it expects that synthetic hoist ropes will become a standard in the industry in the near future. “The benefits to the users in safety, time and ease of use are incredible,” says Quinn. “Competitors are also looking to enter this marketplace with their product offerings. We believe this reinforces the assumption that synthetic rope technology is the new choice for crane hoist lines.”
At the same time, Samson is continuing to work on new ropes for other crane types. K-100 was specifically designed for mobile cranes and the firm plans to grow its portfolio. “Future Samson products will provide even more options for synthetic hoist ropes and the cranes they can be installed on,” says Quinn.
To date, the K-100 has been approved for use by manufacturers including Link-Belt for its telescopic cranes and Altec for a select number of its cranes. There are currently six other manufactures in the process of evaluating K-100 for use.
Manitowoc, too, has big plans. Moving forward, it plans to keep working with innovation partners to take its product offering to the next level. This includes a replacement of the steel-tensioning systems with fibre pendants. “We constantly try to find new technology and disrupt ourselves before anyone [else] disrupts us,” says Munuswamy.