Power supply in overhead cranes: energy chains vs. festoons
25 June 2019
Reliable, dynamic cable management is one of the greatest challenges in modern crane technology.
Virtually all types of crane applications are facing increasing requirements for travel distances, speeds and precision. In the international overhead crane market, where numerous standards exist, manufacturers and end-users are seeking electrification solutions that can be adapted to the specific scenario. In this article, Justin Leonard, the-chain director at igus, looks at the current festooning method and suggests a better alternative.
Festoon systems are designed to provide direct electrification with flat or round cables. The cables in festoons are hung from trolleys that park together at the end of the crane rail. While this structure provides defined linear guidance, it consumes space on the crane rail, which this limits the length of crane travel. As the cables are essentially clamped in bunches, replacing or adding individual cables can be a time-consuming process. The festoon system also incorporates a variety of linked components, including wheels, tow cables, shock cords and bearings. Each individual part requires regular maintenance and lubrication, especially when exposed to tough operating environments.
In festoon systems, cables and hoses hang loose while moving. Unprotected, the cables can swing, become tangled and get caught in the crane structure, especially during adverse weather conditions, which leads to costly repairs. Often, festoons use flat composite cables consisting of multiple conductors in a single jacket. When these cables are used, the entire composite cable may need to be replaced if one conductor becomes damaged. For instance, ship to shore cranes are often equipped with festoons. As this application is exposed to high winds, heavy rain, ice and other barriers, festoon users face high costs for repairs caused by wear and weather. This means further downtime wasted on maintenance and inspections. The hanging cables and steel-dominated structure of festoons also requires ample space for setup and maintenance.
To avoid the maintenance and costs that come with festoons, crane manufacturers are increasingly using an alternative electrification system – the energy chain. Made from high-performance, engineering plastic, energy chains can take on demanding operating environments with their corrosion and wear resistant features, yet have a simple design and are, therefore, very easy to install.
igus energy chains are designed for optimal efficiency. Cables are guided securely in the system with interior separators, so they can never cross over one another and become tangled. With strain relief, cables are tightly clamped and can be easily and released individually for repair or replacement. Unlike festoons, where an entire composite cable may need to be replaced if one conductor is damaged, only the one cable would have to be swapped. Also, because the need for a loop parking station is eliminated, approximately 50 percent less cable is needed. This also brings the additional benefits of reducing mechanical stress, system weight and acquisition costs. And, with no hanging loops, the required operating envelope is smaller – a benefit for applications where space is restricted.
Installation is truly simplified with igus energy chains; a guide trough is installed on the crane girder and the e-chain is populated with cables and then installed into the trough. The moving end is attached to the trolley and the cables are routed to their connection points. Making installation even more straightforward, energy chains are available to order as readychain, equipped with cables and connectors.
Horizontal, vertical, rotary and three-dimensional movements can also be achieved. While festoon wheels, shock cords and bearings are marked for wear and require replacement or lubrication, the chains are maintenance-free, only needing basic visual inspections to ensure the system is in good working order.
igus energy chains are engineered to protect cables from debris and extreme weather conditions. Their clean and durable design is proven to withstand the most demanding environments. Wind will not damage the system, as cables are securely guided and cannot get caught at any point. The predefined bending radius also prevents the cables from being bent below the manufacturer’s recommended bend radius, which sometimes occurs with free-hanging festoons. For additional protection, the chains are available with integrated rollers for extremely long travel distances, as well as special materials for chemical resistance. These rugged energy chain systems can be configured in many ways, from use on hoist trolleys at high speeds to managing long travels with special requirements. This modularity can be applied to a wide variety of applications, including both outdoor gantry cranes and indoor bridge cranes.
The entire range of igus energy chains includes over 90,000 variations, all of which are tested continuously. The most popular energy chains for use in crane technology are the heavy-duty E4.1 series and the cost-effective E2/000 series. Crane manufacturers are progressively reaping the benefits of energy chains solutions, as the carriers are compliant to industry standards, yet universally applicable. To date, over 30,000 cranes, worldwide, are equipped with igus energy chains. Various factors can be considered during the selection process, but when maintenance, costs and environmental resistance are of the essence, users should consider using energy chains instead of festoon systems.
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