The Kocks Barge Server crane equipped with ITT Control Technologies’ buffers at the inland container terminal in Meerhout, Belgium.

Along with vibration, shock is detrimental to maintaining a machine for peak performance. In extreme situations, shock can damage equipment and injure workers. One instance where shock (if an energy absorption device is not considered) can cause damage is with crane systems. If an operator loses focus or a motor on the crane’s trolley malfunctions, a runaway condition can send a trolley and load crashing toward the end of the crane bridge. Shock absorbers prevent damage or injury when a high-impact situation occurs.

At seaports and inland terminals, container ships rely on industrial cranes suspended from bridge trolleys to load and unload goods. These cranes lift 6.1-meter-long intermodal containers, or twenty-foot equivalent units (TEUs), between ships, trains and trucks. The crane operator controls the process from a cab that runs along a trolley suspended high above the work area. The best container terminals maintain low operational costs, high performance and around-theclock availability. To make this happen, cranes with low maintenance and operational costs as well as a long service life are required.

A New Crane for the Container Terminal

Kocks is a crane manufacturer headquartered in Bremen, Germany, specializing in lifting and transporting heavy loads. It is one of three companies (the others are Ardelt and Kirow) part of Kranunion, and has placed a premium on designing and building crane systems that anticipate a range of challenges, including vibration and shock. Kocks is currently erecting a Barge Server crane for an inland container terminal in Meerhout, Belgium. Kocks designs its Barge Server crane equipment to unload barges and stack containers under the crane portal. Trucks are then loaded under the landside cantilever. In Meerhout, a single lift spreader or a twin lift spreader in twin-twenty operations can handle empty containers.

The Meerhout terminal, owned by Binnenlandse Container Terminals Nederland (BCTN), is spread over 110,000 m². Meerhout has a capacity of 400,000 TEUs. The container terminal already includes two cranes for unloading barges and stacking TEUs under the respective crane portals. The Barge Server crane is a gantry crane designed to achieve the lightest overall weight, either in full panel construction or with lattice structure. In comparison to solid structures, the lattice-type construction from Kocks is considerably lighter, which enables large span widths. According to Kocks, the project began last year and the crane manufacturer will have the new, 300-tonne crane operating by February 2016. It takes approximately 15 months to build a crane of this type, according to Kochs.

"One of our initial challenges was working with BCTN Meerhout to decide where on the terminal site they wanted the new crane installed, says Holger Brunzlaff, contract manager for Kocks. Brunzlaff’s job is coordinating the construction of the crane bridge including its mechanical parts and design of the electrical equipment. There can be approximately a dozen firms involved in delivering major parts and equipment, adds Brunzlaff."

"Initially, the idea was to replace one of the existing cranes with a new Barge Server crane. The terminal’s management rethought that approach and decided they wanted the crane on the same tracks, between the existing cranes, says Brunzlaff."

"The terminal manager then felt this would be too much of a disruption for operations. So we decided to place the new crane outside of one of the existing cranes, making the new Barge Server the first in a row of three cranes."

As part of the design and construction process, Kocks included provisions for isolating and preventing vibration and shock that could affect the crane’s operation. A design challenge for the Meerhout project was the fact that a new Kocks Barge Server crane will be working alongside an existing crane travelling on the same tracks, at a different speed and mass.

An Active Vibration Damper Speeds the Operation

To address the issue of vibration, Kocks had previously turned to ITT Control Technologies EMEA GmbH to design a vibration damper for its container bridges. This active vibration damper on the shore side boom of its container bridges compensates for undesirable structural vibrations that can slow down operations as a crane operator steadies a load, resulting in longer handling times. The vibration damper also minimizes load swing on the spreader, so crane operators can accurately set down containers without delay.

To protect the new and old bridge from shock in the event of a collision with one another, Kocks consulted again with the engineers at ITT to develop and install buffers on the Barge Server crane.

The Kocks Barge Server crane’s undercarriage equipped with the ITT buffers painted with black and yellow diagonal stripes.

The ITT buffers.

Deciding where to place the buffer stops and designing them took several iterations because, as mentioned before, the position of the new crane at the terminal was revised several times. As a result, Kocks had to reposition the buffers. Ultimately, the solution was placing buffers on both new and old cranes, so a collision would cause buffer to meet against buffer.

Engineers calculated the forces and designed the buffers to meet starting conditions of 150kN. The solution was a heavy duty shock absorber that would operate from -20 °C to 40 °C and decelerate an energy capacity load of up to 8 million in-lbs. per cycle. Once designed and manufactured, Kocks placed the fixed buffers at the end of the crane rail as well as between the cranes. While Kocks can often use the same overall design for its Barge Server cranes, Brunzlaff notes that every crane is different from one another and each application is unique. Even the shock absorbers and vibration isolators must be tuned and modified each time to account for differences in the length of outriggers, the span of the bridge and the lifting heights and speed of the crane.

For the new Barge Server crane at BCTN Meerhout, the lifting speed is 30 m/min for a full load and 60 m/min when empty. The crane’s top travel speed is 120 m/min, while travelling a crane rail almost 400 meters in length. The bridge on the Barge Server crane is nearly 90 meters long, so Kocks is transporting the structure in four parts to the terminal by water. The Barge Server’s machinery house trolley reaches a speed of more than 180 m/min. The crane runs on 400 volt AC power and a 3-phase induction motor. The Barge Server’s trolley includes a motor on each wheel, plus two hoists with motors for a total of approximately 20 motors.

Buffers for the Crane Operator’s Cab and the Trolley

ITT’s engineers also developed buffers for the crane operator’s cab and the trolley, so that neither cab nor trolley slam into the end of their respective tracks when moving above the container terminal. The shock absorbers include an air-charged bladder accumulator that provides a shorter length and reduced weight compared to competing products. The zinc-plated skin on the shock absorbers gives an added layer of protection against corrosion, especially where equipment is exposed to the elements.

As Koch made its design decisions for the Belgian container terminal’s new Barge Server crane, engineers knew they couldn’t simply choose shock absorbers and mounts from a catalogue. They went about thoroughly analysing and testing their assumptions to ensure optimal results. To determine, for example, the right viscous damper design, Koch turned to ITT to consider the angle of recline and the right damping coefficient and characteristics. The consultative engineering approach led to the right damping and vibration isolation solution, which will ensure the new crane and the terminal’s profits alike are protected.

It is important to consider more than just the weight of the material handling device when considering shock protection, whether it is an overhead crane, container terminal crane, assembly line or overhead conveyor system. The velocity of the impact plays an important role in the amount of damage that could occur in the event of an impact, as it has a squared function in the calculation of kinetic energy (E = ½ mV2). By fully analysing the shock event, a crane builder or buyer can insure that equipment is protected.

The article was originally released in German in the magazine Hebezeuge & Fördermittel.

Dieter Klaiber

Project &Application Manager,

ITT Control Technologies EMEA GmbH,

dieter.klaiber@itt.com