The company has taken a number of steps to deal with these issues. Firstly, they work to ensure that the selection of cable reels and reeling cable precisely matches application requirements: “Expert knowledge and experience with these applications is the key for high-performing systems. Today, it is mandatory to make sure that deflection devices are perfectly in line, so as not to generate additional torsion on the cable.” The manufacturer adds: “Some devices such as cable guides need to be positioned at the proper height and according to the anchor bollard depth, for example. This helps to reduce cable tension at the centre point when crossing at full speed. Full speed at the centre point is one of the key issues at the moment, while productivity cannot afford slowing down for any reason. [Our] currently installed systems achieve 180m/min crossing the feeding point.” Of course, a further fundamental is the choice and design of the cables. There are a number of variables to think about in cable choice, all of which have a knock-on effect and must be carefully considered to provide an effective, comprehensive solution. For example, the weight and diameter of a cable affects the size and cost of the cable reel, and alters torque and storage space requirements. “The lighter the cable is, the less torque you need,” states Conductix-Wampfler. “However, most of the time, a lighter cable has a lower maximum tensile strength. Looking at this, when speed is high at the centre feed, or when the installation height is huge, we often have to go for a bigger cross-section than electrically required.” The company operates several testing facilities in Germany (V-REX) and France, where reeling cables and reeling systems can be tested intensively. It adds that, “all well-known cable manufacturers make use of our test systems to test the performance of reeling cables under lifetime conditions.” Finally, the company cites accuracy of pull regulation as being more important than ever before. This comes down to two main technologies available on the market: “On the one side, we have the permanent magnet coupler. This technology has been around for over 40 years; however, Conductix-Wampfler is continuously optimising it to achieve perfect performance and reliability,” the manufacturer states. “With the modular design concept of the Conductix-Wampfler range, standard AC motors are used for the reeling systems. Depending on the torque requirements, they can be switched on and off during the operation to always keep the perfect tension on the cable. In 2006, Conductix-Wampfler developed and patented a new generation of high-tech permanent magnet couplers based on rare earth magnets. These couplers generate an almost constant torque at various speeds. They are much smoother for the cables and more efficient than previous generations of magnetic clutches or competitor products. This provides a further step forward for our product for the future.” In terms of reducing maintenance downtime, Conductix-Wampfler states that it is working towards improving maintenance windows, increasing the lifetime of reels and cables, and offering a ‘plug and play’ solution. With modern drive technology, the company states, it has also become possible to feed back energy into the power grit. Conductix-Wampfler tells us that, in the past, energy has been wasted in large braking resistors at the spreader reel. This energy, the company states, can now be re-used to enable a much more energy-efficient operation. Conductix-Wampfler adds that the variable frequency drive (VFD) solution is another important facet in delivering cable solutions. This adjusts the torque level directly inside the motor, and the cable pull is continuously adjusted along the run or lift. VFD is required for fast applications of up to 300 m/min and accelerations up to 0.6m/s². The company admits that, in line with the experiences of crane manufacturers, it has suffered through the effects of the global economic downturn. While its order books are now certainly showing signs of improvement, project decisions continue to take longer than they had previously, and larger-scale projects have been scarce in recent times. Orders for medium-sized projects for ship-to-shore cranes, railway terminals and, mainly, electric rubber-tyred gantry crane (E-RTG) applications have accounted for the greater share of orders. The company’s largest cable solution project in 2010 so far has been a deal with ZPMC, using Tratos cables, for 38 rail-mounted gantry cranes. The manufacturer has also notched several new projects for the electrification of RTGs. It has been involved in a number of further projects for large-level wind reels in the Australian mining industry, supplying more than 25 large wind reels to various customers. The company boasts that local engineering, production and assembly facilities have helped it become “a key supplier for this industry in Australia.”
Tried and tested solution
Stefan Munko, the European PR contact for US-based, global company Kabelschlepp, is keen to underline the continuing importance of steel in the production of cable solutions. “Steel as a material for energy chains is still going strong, as many satisfied Kabelschlepp customers experience in daily operation. Highly rigid and sturdy, the ancestor of all cable chains is still the first choice for many applications. A little known fact, though, is that steel chains are maintenance-free,” details Munko. “In engineering, steel is indispensable in delivering properties like sturdiness, heat resistance, durability, impact and corrosion resistance. Also for cable carriers, demanding operation conditions have shown steel to be first choice. This is why Kabelschlepp has continuously upgraded its Steel Line to latest specifications, offering bespoke solutions for demanding and extreme applications.” Kabelschlepp cites offshore applications as being one example of this. Because steel chains are corrosion and UV resistant, with maximum durability offered by their material properties and specific design, they can withstand high mechanical stresses, high loads and long unsupported travels. The manufacturer states that its decades of experience have aided it in delivering sophisticated solutions and designs, including chain bands and links with diverse geometries, amongst them an open stroke system with self-cleaning properties to reduce wear and to increase longevity. This also allows maintenance and lubrication-free designs. “Steel Line does not require maintenance downtimes,” the company boasts.
Contract for Cavotec
In June, global company Cavotec MSL announced that it had sealed a contract to supply high-voltage cable reel units and associated control reels to Chinese engineering group Dalian Huarui Heavy Industry, as part of an extension project at the Caofeidian Island Coal Terminal, located on China’s east coast. The island is built entirely on reclaimed land and located 210 km (130 miles) south-east of Beijing. The State Development and Investment Corporation Caofeidian Port Co Ltd oversee and manage the extension project. “This is an excellent vote of confidence in our customer service and advanced engineering capabilities, because Cavotec installed all the cable reels used in Phase 1 of the Caofeidian Coal Terminal project in 2007 and 2008,” Gustavo Miller,
Managing Director of Cavotec Shanghai, said when the deal was struck.
The company is manufacturing seven high-voltage cable reels and seven control cable reels for use on six re-claimers with an operational capacity of 6,500 tonnes per hour, and one stacker with the same capacity. The coal terminal’s extension will see a total investment of RMB 5.43 billion (EUR 670 million, USD 800 million), and is set to increase handling capacity to around 100 million tonnes per year.