Chain reaction

The use of energy chain systems for gantry cranes [in particular container cranes, RTGs and RMGs] rather than the more traditional festoon system seems to generate great interest from manufacturers. Our latest reply (following that from Conductix-Wampfler in our January/February 2010 issue) has been from the US subsidiary of German-based Vahle. According to Marvin Minton, Technical/Sales Manager North America for the company, their stance on the use of energy chain systems is that this is relatively new technology (compared to the tried-and-tested festoon arrangements) so it is difficult to gauge the effect on festoon suppliers. “It must be realised that this concept [energy chain system] does not eliminate wear items, rather it increases them as every link of the energy chain has to move and flex,” explains to Minton. “There will also be increased potential wear of the cables due to the greater flexing of the cables over a tighter radius”. Vahle has attempted to produce a study regarding these phenomena as a comparison, but feels that the technology in this application is still too new. According to Minton they have spoken to some end-users with these applications on RTG cranes and the response was not completely favourable for energy chain applications.
Case in point
Up to now, Traditionally the transfer of data and power has been achieved on quayside ship-to-shore container cranes primarily through the use of festoon systems..However, and according to Minton, there are significant problems with this relatively ‘old’ technology. For example, due to mechanical stress the cables on the festoon system have to be replaced every three years and there is a limitation on the trolley speed. But as we have seen in previous articles, energy chain applications are not cheap to purchase, while on the other hand festoon systems can be quite costly in the long run. Therefore, terminal operators have been looking for a more reliable solution which will give considerable [productive and] maintenance advantage and in addition bring a certain degree of cost savings. Energy chain manufacturers set out to design and create an extremely reliable and almost maintenance free solution in order for the crane trolley to receive both communication signals and electrical energy from one source. Up to now, the transfer of data and power has been achieved on quayside ship-to-shore container cranes primarily through the use of festoon systems. Vahle designed their energy chain system by combining their U35 conductor rail and a contact-less data communication system (SMG). The combination of two new technologies solved many of the ‘common’ problems. The U35 conductor rail provides the trolley with power and the SMG gives all the necessary control signals, as well as video, voice and emergency stop communications, resulting in trolley speeds of up to 600m/min (in theory). Another advantage of combining the two technologies is that maintenance costs, downtime and wear are minimised, as only the carbon brushes of the U35 collecting trolleys need to be replaced. This is required only around very 15,000km, which can, depending on crane use, mean a service gap of several years.
Other benefits
For operators there are numerous benefits when using an energy chain systems rather than a festoon system including the absence of cable loops hanging down from the boom. Effectively this means that container stacking levels for example for RTGs and RMGs can be increased by up to 3m – a huge advantage for those container ports and terminals where available space is limited. Another benefit is that there is a significant reduction in mechanical stress levels – not only on the system as a whole but also on the cables and moving parts. Compare this with the festoon approach and this leads to greater reliability on the energy chain system. Furthermore, the system’s lower weight allows the crane to have a higher load capacity, while the absence of a cable storage area simplifies crane construction. Another point to consider is that an energy chain system is less likely to be affected by environmental factors, such as wind, ice and rain compared to a festoon system.
New concept?
As we have seen previously (see October 2009 issue) the idea of the energy chain system on gantry cranes is not something new, although it has so far proven its reliability in a number of container ports and terminals. For Vahle, their first container crane equipped with the SMG/U35 combination was delivered in 2001 and built by Kranservice Rheinberg, Germany, for the Tees & Hartlepool Port Authority, UK. “No complaints or problems have been reported, and in fact the crane seems to be working faultlessly,” report Vahle. It took another 4 years before Vahle installed another SMG/U35 system during a refurbishment project of a panamax crane in Hong Kong. The crane – originally built by Mitsui Engineering Services from Japan – with a festoon type system was used at the HIT terminal but was moved and is now operating in the Hui Zhou river terminal in mainland China, which also belongs to the Hutchison group. Vahle also installed their system on a crane, built by Shanghai Port Machinery Plant (SPMP) in China, at the Shanghai Pudong International Container Terminals (SPICT) facility. The rope driven ship-to-shore crane was being refurbished and the festoon system was replaced with the fitting of a SMG and 4-pole U35/230AE aluminium stainless steel conductor rail. As with all new technology the benefits have to be considered against its investment cost. Although many operators can see the [financial] benefits of energy chain systems it will be a long way off before they can be convinced they can make a return on their investment. As Minton points out, consideration on the choice of the right cable for the job is another hurdle to overcome – with greater flexing over a tighter radius perhaps this will be a bigger challenge faced by the operator than the costs of the energy chain system itself. But with the industry facing a global downturn, investing in this technology might be put on hold even though now might be the right time to upgrade your cargo handling equipment.