Can automation tick the safety first box for straddle carriers. John Bensalhia investigates
Ports have found that when it comes to productivity, the straddle carrier is a godsend: a good straddle carrier can carry two 2ft containers at once and can stack containers one over as many as four rows.
And with the technological age well and truly upon us, the straddle carrier is also a popular choice in that it can be automated. This means a double-win for ports: not only does it further boost productivity, it also lowers costs by keeping both equipment and labour requirements to a minimum.
Indeed, in Kalmar’s view the safest mode of operation is automation.
Dr Tero Kokko, vice president for Kalmar’s Horizontal Transportation business line, says: “With automation being a major focus area of Kalmar, we have worked intensively on the fully automated version of the straddle and shuttle carriers. Automation does require a different set-up of systems and components, which resulted in numerous changes and improvements of various sub-systems and the way in which they are controlled.
“With the testing of the new generation now ongoing on our test-site we are seeing that our learnings are paying dividends in the performance of the machines.
Safe and sound
But not all ports are willing to take on unmanned straddle carrier systems, which poses the question – what makes a safe straddle carrier? One notable source to provide an answer to this question is a joint venture between three different companies – the Port Equipment Manufacturers' Association, the TT Club and ICHCA International.
The three parties initially came together in 2010 to put forward a series of recommended minimum safety features for use on all quay container cranes. The first result of this initiative was the publication of Recommended Minimum Safety Specifications For Quay Container Cranes in June 2011. Contained in this are a number of suggested safety features for straddle carriers.
Those features tackle issues such as anti-collision; air filtration system in the operator cabin; braking and parking; the weight and eccentricity of each container load; smoke and temperature detection; detection and suppression of fire; the prevention of unintended access to risk areas; controls for even load distribution; seat belts; plus stability and visibility. Requirements are outlined for each issue in order to achieve high safety standards.
Straddle carrier manufacturers have taken the health and safety issues on board. Two of the main players, Kalmar and Liebherr have implemented a number of features that allow safe and productive straddle carrier use.
“Kalmar ensures that the shuttle and straddle carriers meet all the international health and safety regulations, both in design and manufacturing as well as in operations,” says Dr Kokko. “Thorough risk analysis to recognise and eliminate possible safety hazards in operation and maintenance has been carried out. The solutions in this regard are tested and verified extensively at the test site in Kalmar’s new technology centre as well as field testing at end users’ sites.
“Kalmar is co-operating with domestic and international suppliers and institutes in relation with health and safety.”
The manufacturer ensures that its manually operated systems are as safe as possible. Each machine has the optional monitoring, alarming and diagnostic features in the control system for functions such as stability, tyre pressure, smoke and fire, and fault detection.
“Additionally each machine can feature active stability control, semi and fully automatic fire suppression systems, while wet disc brakes which are insensitive to climate conditions are standard,” says Dr Kokko. With respect to the health of the straddle carrier operator and the ergonomics of controlling the carrier, Kalmar has also made sure that noise reduction materials are employed and that the carriers can be equipped with both reverse cameras and improved lighting.
Liebherr has also included a number of technical features to its range of straddle carriers to ensure maximum safety. The design of its carrier uses a four axle steer by wire system, which allows a two or four steering mode. So, if the carrier goes beyond set travel speed, then it locks out the rear wheels and instead, only steers with the leading wheels. This allows for stable, agile movement at a slower speed.
One notable issue regarding common causes of fire risk in straddle carrier engine enclosures is that of hydraulic oil. With that in mind, Liebherr has ensured that the hydraulics are located at ground level each side (as opposed to being in the engine enclosure) – this means that the risk of fire is considerably reduced.
The proximity of the Liebherr carrier's ground level hydraulics also makes for a more precise wheel alignment. This enables improved directional stability on straights and cornering. The operator will therefore find it easier to keep the carrier moving in a straight line at speed – additionally, this aspect of the carrier means less wear and tear on the tyres claims the manufacturer. Each steering cylinder is also independently monitored, which means that the wheel alignment system is self-correcting throughout the steering range.
Safety logic blocks are built into the carrier, which monitor both stability and the control of speed. These blocks closely monitor the stability ratio to limit speed in accordance with ISO14829 defined stability cases. As a result, this facet allows for travel speed reduction with increasing hoist height or steering angle. The operator of the carrier can also be warned in the event of getting too close to the stability limit through both sound and visual facilities.
Training for safe operation of straddle carriers will – as Dr Kokko of Kalmar says - depend on the qualification of the drivers and the characteristics of the port. Dr Kokko adds that “there are different trainings that can be considered. The required trainings should at least include training for safety issues, internal driving regulations (the rules of the terminal), understanding of stability factors and using of the emergency systems of the machine.
“Additionally Kalmar always advices that the correct reporting of machine faults and malfunctions be added to the training program. This knowledge allows operators to recognise when their machine is behaving differently, making sure that it is serviced before it breaks down. Also with the proper input to the maintenance crew, the Mean Time to Repair can be reduced greatly. Finally training on economical driving is also advised. With the fuel prices ever increasing, the ‘smart’ usage of the machine can help reduce the resulting operational costs.”
With automation now part of the equation, the straddle carrier looks set to have a future that is both safe and productive. And by meeting the many safety requirements involved with manual operation, straddle carrier manufacturers are ensuring that their products not only tick the boxes of efficiency and quality service, but also a safe, protected environment for the operator.
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