Umbilical cords of port machinery
Dave MacIntyre finds out if crane cable chains deliver everything they promise
Cable carriers, also known as drag chains, energy chains (e-chains), or cable chains depending on the manufacturer, have been likened to the umbilical cords of modern machinery, reducing maintenance and increasing the service lives of cables and hoses.
They are guides which surround flexible electrical cables and hydraulic or pneumatic hoses connected to moving automated machinery. They may carry data and fibre-optic cables or electricity, gas, air and liquids, reducing wear and stress on the cables and hoses, preventing entanglement and improving operator safety.
They are deployed in moving plant such as cranes and forklifts, and therefore are of importance to the operation of marine terminals. It is a competitive environment and one in which several major suppliers work closely with ports.
From a port's perspective, cable chains claim to offer benefits when compared with festoons.
German-headquartered igus developed plastic energy chains in 1971 and in 2017 surpassed 1,000 ship-to-shore crane e-chain systems installed worldwide. The company's engineered systems manager for igus North America, Sean McCaskill, says the biggest difference is that energy chains only require periodic visual inspection.
“They are maintenance and lubrication free and resistant to moisture and ultraviolet rays. They also save space and are easier to replace than festoon systems.”
Mr McCaskill says energy chain systems require less preventative and corrective maintenance than festoon systems. “There are no wheels, shock cords or other parts that need to be replaced at regular intervals. New designs are predicted to operate for up to 20 years without parts being marked for regular service or replacement.
“Also, they are simple systems that require no additional controls or motors to operate at high speeds.”
The mastery of being able to offer a product to a port or marine terminal, he says, is in “getting it to run for ten years in that environment without touching it”.
E-chains can also be equipped with smart sensors, which Mr McCaskill says is indicative of an industry utilising every advantage it can get to gain a competitive edge.
“Predictive maintenance and monitoring systems are at the forefront of that push. The iSense system allows insight that was never possible before, into the operational status of your equipment.
“The first generation of smart sensors from igus could do things like shut down the crane in case of the failure of a system. The second generation can send you warnings before a failure event happens by monitoring performance in real time and picking up abnormal operation conditions before they become real problems.
“These sensors can monitor for energy chain system disconnection of links; over/under push-pull force values during operation; wear and life prediction; cable tension; conductor life inside cables; and rising of the upper run of the energy chain system due to blockage. The system alerts operators when something starts to go wrong before a failure occurs.”
Cosimo Lupo, export sales senior manager for the Italian-based manufacturer Brevetti Stendalto, says that while the advantage of a festoon system is that it is less noisy than chains, there are several disadvantages.
“Festoon cables have to be as long as 1.6 times the travel distance they have to cover. The cables lodged into a centre-fed energy chain will be as long as 0.6 times the travel distance they have to cover.”
He adds that festoon cables are always bent in the same points, which means that both the copper of the conductors and the plastic material of the sheaths can “get to their fatigue limits within a quite limited number of cycles”. Consequent breakages can lead to serious safety troubles or to service being halted.
Further, the high winds that marine applications can be exposed to may cause the hanging cables of festoons to be twisted with possible work interruption. “Off-shore installations do not allow hanging cables for safety reasons,” he points out.
Mr Lupo says motors, carts, guide rails and pulling ropes require constant maintenance in outdoor applications. “The original set of cables cannot be easily changed in case [more are] required during the life of the system.”
Because some festoon cables are of a special design, they also require big industrial batches to be produced.
He compares this with Brevetti's chain systems which are designed to facilitate easy replacement of the parts subject to wear during the planned stops of the cranes.
“This means that the operating life of our chains can be extended to the life expected for the cranes themselves,” he says.
Another major player with 65 years' experience in the cable carrier sector is Germany's Tsubaki Kabelschlepp, which supplies everything from small plastic cable carriers and guide single cables up to huge stainless steel heavy duty cable carriers for rig skidding applications on offshore oil rigs.
Asked to compare the benefits of different types, Peter Sebastian Pütz, the company's head of strategic marketing and head of crane division, says guiding cables with a cable carrier instead of a festoon system is a safer and more modern way for crane applications and also saves space.
“A cable carrier system is directly installed under the main beam with a system height of approximately less than one metre. No down-hanging loops which can be caught up by the crane steel structure. No loop station, no additional steel structure – to store the festoon loops you need approximately 10% of the travel way additional steel structure.
“This is not necessary with a cable carrier system. The end of the crane beam is at the same time the end of the cable carrier. There are no additional drives – a cable carrier will be pushed and pulled by the trolley. For fast-running cranes you don't need any additional drives like you need with fast-running festoon systems.”
Having no additional drives also means there is no need for an additional control system to synchronise the trolley with the cable management system.
Mr Putz says a cable chain system is the only system you can use for all kinds of media at the same time, such as cables, hoses and fibre optics, which can be guided in one system.
Another benefit of cable chains is the reduction of mechanical stress for cables. Even if a crane is not running, festoon cables are always moving due to the travelling trolley, the gantry travel and wind effects.
“You don't have this situation with cable-carrier cables. They are installed inside the cable chain and the cable carrier is moving smoothly back and forward with less mechanical stress to cables and hoses.”
Maintenance is also easy, with no greasing, no roller changes and no bungee rope change. Mr Putz says every mechanical system which is installed on a port crane needs some maintenance, but this may be minimal. “Crane cable carriers from Tsubaki Kabelschlepp just need some visual inspection, that's all,” he says. “Most of our port crane customers are expecting ten years lifetime independently from operation hours.”
For marine terminals, Tsubaki Kabelschlepp recommends hybrid cable carriers which consist of plastic side parts and seawater-resistant aluminium crossbars. The company says these crossbars are much better gliding partners for cables than glass-fibre-reinforced plastic crossbars.
Asked what advice Tsubaki Kabelschlepp would give to a port or marine terminal looking to make an investment in cabling systems, Mr Putz says he would suggest a personal visit to the company's headquarters in Germany to get advice on the right cable carrier for their needs. The company has a test laboratory for all kinds of cable carriers and an outdoor crane test facility.
VIRGINIA SWITCH PROVES A SUCCESS
The Port of Virginia has expanded operations in recent years and was awarded $15.5m for improvements by the federal government in 2018.
It selected igus e-chain systems for the all of its new equipment at Virginia Inland Port and Norfolk International Terminals.
Jeff Johnstone, crane maintenance manager at the Port of Virginia, says the port had used a wheeled festoon port for years.
“Bearings, bolts, shock cables, tow cables – all of those components need to be maintained monthly and replaced quite often. When we switched to the energy cranes, all of that went away.
“In the first year they were in service, we were waiting for something major to go wrong and it just didn't happen. The maintenance we had to do was minimal compared to the maintenance we had to do with the wheeled festoon systems.”
Danny Webb, the port's general manager of technical support and special projects, confirms that the reliability of the new system was the biggest surprise, and has contributed to other ports taking notice of Virginia.
“Cranes are getting bigger, they're getting taller, they're getting faster. It's impressive to see the amount of technology on one piece of equipment.
“The size of the port, and the projects we're undertaking, and the aggressiveness we're going after is unrivalled. Now, everybody's thinking 'What's Virginia doing?',” he says.
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