Tangible benefits

At ConExpo in Las Vegas earlier in 2014, Manitowoc fitted a 65t Grove RT770E rough terrain crane with a synthetic rope developed by fellow US company Samson, called KZ100. The dramatic weight reduction -- losing 80% of the weight of steel wire rope -- was part of a package of features aimed at improving the load chart at radius. The crane has a 42m boom, said by Manitowoc to be the longest in its class.

Manitowoc president Eric Etchart, talking at the recent CICA Conference in Australia, said that he believes the use of synthetic materials is on the brink of making a major breakthrough.

"Using synthetic rope is an obvious next step for the industry and the advantages in terms of weight savings and ease of use speak for themselves," said Etchart.

"I think in a few years, we'll all look back and ask ourselves why there was ever any doubt about using synthetic rope to replace wire rope.

I know from talking to customers, they can already see the tangible benefits it offers in terms of making their cranes more competitive."

This view is backed up by other activity in the industry. Liebherr and Huisman are both using synthetic pendants; Sany is set to introduce a synthetic boom retraction rope on a telecrawler; and Samson is looking into the use of its rope on other crane types, including tower cranes.

For now, the next stage for Manitowoc is to introduce the KZ100 rope as an option of all of its Grove rough terrain and truck-mounted cranes by the end of 2014 -- with the exception of the Grove Yardboss industrial cranes, the RT9150 and TMS9000 models, and national boom-trucks, on which the rope will be introduced by the end of the first quarter of 2015. By the third quarter, the company plans to have introduced it onto its GMK3060 and GMK4100 Grove all terrain cranes. Manitowoc's mobile crane division has exclusivity on using the rope in the crane sector until September 2015.

The move represents a way of improving the capabilities of cranes without requiring a major re-think in crane design, says Michael Quinn, director of sales at Samson:

"For the crane developers and manufacturers, the weight saved by using the lighter rope can be added into the load chart, either extending the boom length, increasing the maximum load, or both.

"Cranes are always being asked to do more -- to load more, or to be more efficient. To achieve this without developing a new crane, incremental improvements can be used -- such as using lighter rope.

"The rope also offers advantages for the operator -- it is easier and safer to handle. It won't cause cut hands as metal rope can do, and the reduced weight lessens the risk of back strain.

"Installation and handling is easier, which can enable singlelift cranes -- typically hired for a minimum half-day -- to perform multiple jobs in that time, rather than just one.

"KZ100 is a braided rope, with strands twisted in opposite directions, making it torque neutral. Compared to metal wire, this results in significantly less potential for spin and birdcaging."

The rope also eliminates issues with multi-layer spooling, which had affected synthetic ropes in the past, says Quinn:

"We developed a 12-strand rope on the outside but with a center core, to provide stability. It will properly lay into the drum grooves when spooled at high tension.

"We tested various constructions for spooling, and developed a process which is just as efficient as spooling metal rope, but is more forgiving to handling issues which extends the life of the rope."

The benefits are clear, then -- but as with any new technology, straightforward integration into existing operations is key to ensuring the industry accepts the innovation. To this end, a full retrofitting and training service is offered by Manitowoc's Crane Care division, says the company's senior manager of engineering, Sammy Munuswamy: "For existing in-service cranes, Manitowoc Crane Care offers the full service that includes purchasing the rope, retrofitting it and training operators on this new technology. Typically, the operator training and crane retrofitting for synthetic rope will take one day.

"Manitowoc has developed a hoist rope system reconditioning procedure for crane retrofitting. Depending on the existing condition of the wire rope hoist system, the reconditioning typically takes oneand- a-half to two hours of prep work for installation of new synthetic rope. This can be done by job site operators along with the help of either Manitowoc or Samson reps.

"The Manitowoc-Samson partnership has developed a training manual for rope handling, installation, inspection and retirement guidelines."

Part of the training involves identifying when the rope needs to be replaced, says Quinn: "We have developed discard criteria which are necessarily different to metal rope.

The KZ100 comprises millions of individual fibres, so the operator cannot count broken fibres as with metal rope. Instead, we have produced an abrasion comparator, with a scale in seven stages all represented with photographs showing comparative levels of abrasion."

While the cost of KZ100 is around three times that of metal rope, the advantages more than make up for this, says Quinn: "The other industries which have adopted synthetic rope have found that the advantages outweigh the additional cost."

The rope is produced by Samson using Dyneema, an 'ultra-high-molecular- weight' polyethylene fibre produced by Netherlands based DSM. With sales of around €10bn in 2013 and almost 25,000 employees worldwide, the company supplies Dyneema for a range of applications. For the hoist rope sector, the key differentiating quality of Dyneema was its flexibility, says DSM's application development manager Paul Smeets:

"There are a number of synthetic fibres available but these are not a flexible as Dyneema. Due to the need for ropes used in the crane sector to run over sheaves, the bending performance of Dyneema was the key differentiating feature compared to other fibres.

"The other important quality of Dyneema for use within the crane sector was compression resistance, which is important in countering the pressures of multi-layer spooling.

"The material also has the highest modulus within synthetic fibres -- it is similar to that of steel. Rope which does not elongate is of course very important to lifting applications."

As well as representing the first synthetic hoist rope, KZ100 also pays tribute to one of its developers, says Quinn: "The name of the rope comes from the initials of Karim Ziyad, who was a lead engineer on the project and who was killed in a cycling accident in 2013. So, as a tribute to Karim, the product was named after him."

Retractive prospect
Dyneema is also currently being tested in applications for retracting telescopic booms, says Smeets: "For this, the weight reduction is less important, but what is key is the flexibility of Dyneema, as the rope is required to move over small sheaves."

Leading this development is Sany America, currently completing the structural testing on its SCC8100TBXL crane, a telecrawler with a five-section boom. Suited particularly to road and bridge building, the 110t crane uses Dyneema ropes in the boom, reducing weight while maintaining strength.

After introducing the project at ConExpo, Sany is aiming to have the application commercially available by early 2015, says senior structural engineer Kyle Gerber.

"The Dyneema material has the advantage of being as strong as steel but eight times lighter," says Gerber. "We saved approximately 1,800lbs in our boom by using this rope over steel wire rope. However, the real advantage comes in the flexibility. According to the standard ASME B30.5, the diameter of the sheaves inside a boom are required to be 18 times larger than the diameter of the wire rope running over them. The inflexibility of wire rope makes it difficult to package nicely inside a boom system. With our new Dyneema rope we do not have to worry about this restriction, enabling us to put more rope inside the boom volume, translating into significantly better lifting capacities.

"Also, since this machine is a crawler crane with a telescopic boom, we were able to take the weight savings attained by using the fibre rope and apply them to the tube structure of the boom.

This boom is considerably wider than a typical boom Sany would design for a RT or truck crane. This increased lateral stability will make it the perfect boom for a telecrawler which is rarely level when lifting or travelling with load. Our machine will be able to lift and travel with load while being up to four degrees out of level.

"We have performed lots of functional testing with this boom and the wear characteristics of the rope have been outstanding. We have also performed bend fatigue testing at the DSM facility in the Netherlands using the same size sheaves as we use in our boom and we achieved good results. Overall this material looks very promising for applications in heavy equipment."

Buccaneering spirit
Synthetic materials are already being used in the industry for other applications, including pendants and stay cables. In 2012, Dutch crane company Huisman Equipment supplied a 17m super fly jib for one of the heavy lift mast cranes on board the Happy Buccaneer, a vessel owned by BigLift Shipping.

The jib increased the lifting height and outreach of the crane by 50%, bringing the height above deck to 59m and the radius to 55m. To reduce installation time of the jib, Huisman used synthetic stay cables produced by compatriot company FibreMax.

"The application in the project with BigLift required more outreach than is usual, so the super fly jib was used," says Mathijs te Velthuis, engineering group leader for mechanical engineering at Huisman.

"With the super fly jib, the wires are installed after the fly jib and stay beam have been fitted on, and as another crane is already required to lift the jib, the rigging is typically done using manpower. Handling and installing light synthetic cables instead of steel wires makes this much easier, particularly in projects which are executed on board a vessel and in remote locations. The result was a greatly reduced set-up time for BigLift."

The stay cables were produced by FibreMax using Twaron, a material produced by Netherlands-based Teijin Amarid, which also produces other synthetics such as bulletproof Kevlar. Lightweight and five times as strong as steel, Twaron is particularly suitable for pendants due to its low creep and specific weight, and its high strength and modulus, says Wil Willemsen, sales and technical manager for cables and composites at Teijin Amarid.

Gem Wender, project engineer at BigLift, experienced first-hand the practical benefits of using lightweight cables: "The specifications and conditions of Twaron exemplify the suitability of these fibres for heavy lift applications. Because of the strength, flexibility and light weight of Twaron stay cables, we were able to significantly shorten and simplify the installation of the super fly jib on the Happy Buccaneer."

The Amarid material also offers more long-term benefits, says Wilco van Zonneweld, business development manager at FibreMax: "Amarid offers a number of important qualities. It has a higher strength-to-weight ratio compared to steel, it has good temperature resistance in both heat and cold, it is very stable and has negligible creep properties."

While the technology was sufficiently advanced to assist BigLift with its project, Huisman and FibreMax had a tight deadline to finalise their product, says Huisman's te Velthuis: "We started discussing the project with FibreMax at the beginning of 2011, and by Christmas of 2011 we had developed the product, conducted testing, and completed the project, which was the first application of its type in the world.

"In 2014, we then completed a similar project on a 700t super fly jib on a 900t heavy lift mast crane for Jumbo, a maritime lifting company based in the Netherlands."

Despite the fast turnaround of the BigLift project, not all members of the crane industry are always so quick to adopt new technologies, says FibreMax's van Zonneveld:

"FibreMax specialises in pendant ropes, and currently focuses on the cranes and mining sectors, as well as offshore, heavy lifting and structural applications.

"It took a while before companies became convinced by the product. The crane industry is conservative, and operators are trained in steel and are used to handling steel. Synthetic pendants were, to the industry, a new and unproven technology.

"Introducing the name FibreMax in 2009, the first application was launched commercially at the end of 2010, on a heavy lifting extension to an existing crane.

"One company first looked at the technology four years ago, and is only now adopting it commercially. There are now more than five companies using synthetic pendants in serial production.

"With these companies using the technology, next year I would hope for faster progress. There are still many companies who are unsure of the technology, but as it is now being used commercially, we are able to prove it works in practical applications.

"The cost advantage of using synthetic pendants is spread over time, which can also initially deter companies from converting to using it. But with the longer life of the product, the greater lifts it makes possible, and the time saved in installation, companies find that it is a worthwhile investment."

Slings and beyond
FibreMax is also working on applying synthetics to other areas, says van Zonneweld: "We are testing slings and grommets made from synthetic materials, which will offer similar benefits -- longer life, corrosion resistance, and lighter weight.

"They are not being used commercially yet -- we are working with crane rental companies and end users to trial the developments."

As well as using Aramid materials, other synthetics offer FibreMax different qualities which are suited to other applications, says van Zonneweld:

"We also use carbon fibre, which are suitable for shorter pendants -- but, because the material is not flexible, it cannot be spooled and so producing very long pendants from carbon fibre would make transportation difficult. For example, we are currently making 55m-long pendants with a breaking strength of 680t for a tower crane, which could not be transported without spooling.

"Carbon fibre does offer advantages compared to Aramid, though -- it has a longer service life, it is stronger, and elongates less."

At Liebherr, meanwhile, the company has used synthetic pendants since 2007, when it introduced carbon-fibre-reinforced-polymer (CFRP) pendants for its 200t HS 895 HD duty cycle crawler crane.

Since then, the German company has also added carbon fibre jib backstops and pendant links. And as well as rough terrain cranes using synthetic hoist ropes, the technology could in the future be applied to other crane types.

Samson is testing the use of the KZ100 rope in other cranes, says Michael Quinn: "The rope is not specific to mobile cranes -- it may be suitable for other cranes types as well. We believe tower cranes would benefit from using synthetic rope, which is something we are currently looking into."