Remote load-control systems are designed to make taglines obsolete providing greater productivity, efficiency and safety by automating lifting operations. The Crane Industry Council of Australia’s Technical Committee examines these technologies in this issue’s CICA Tech Corner.
Safety is always the priority for our crane industry. New rigging technologies used by the industry that wirelessly control the load remotely and make taglines obsolete, can help reduce the risk of riggers/doggers being in close proximity to the load and improve industry safety and efficiency.
Why do we need to control the load?
Freely suspended loads from the crane hook are subject to load effects from different forces. These forces could cause the load to swing or rotate during the lifting process. The action of wind force could make the load rotate to its smallest sail area (wind surface area) to the wind, i.e. lifting a lightweight load with a large wind surface area vs lifting a vertical cylinder.
The hoist rope may spin as the load is lifted. Or the load may want to rotate when the crane is slewing, due to inertia force (heavy load has more inertia force compared with light weight). These unintended movements need to be controlled, as they could be risky during the lifting process (i.e. create excess lateral force on the sheave, or if the crane is operating near powerlines, the swinging movement could push the load into the danger zone).
How do we control the load movement?
The rigger/dogger uses tag lines attached to the load to control load swinging/rotation or guide the load along a particular path during the lift. Or in the less common cases – manual load control may apply, for example, aligning the load with a foundation on the ground to bolt it down.
When controlling the load with taglines, the pulling force applied by the rigger/dogger is most effective when the tagline is near horizontal. At 45° to the horizontal, the pulling force is only 71 per cent effective.
As the angle to the horizontal increases, the effective pulling forces decreases, when pulling at near vertical position with the tag line, the pulling force is all vertical.
What are the benefits of remote load control systems?
Most crane lifting operations involve lifting the load up and placing the load to a different location by hoisting, slewing, crawling or a combination of movements. Riggers/doggers who work with the crane operators and use the taglines to control the load movement need to move with the load to make sure the load control effort is effective. This requires the rigger/dogger to work and move near the load.
Data from NSW Centre for Work Health and Safety shows that between the year 2012 and 2019, “Hit by load” was the most frequent mechanism of incidents (42 per cent) and accounted for a high proportion for all crane types.
Remote load control rigging devices use angular momentum, inertial force, and gyroscopic modules to rotate and control the load. The rigger/dogger can control the movement of the load remotely without working near the suspended load. This could help with preventing some of the “Hit by load” accidents happening during the lift.
When lifting the load up to an elevation high above the rigger’s/dogger’s standing location for example, lifting something up to the top of a building – effective pulling force from the rigger/dogger will decrease, when they are standing at near vertical position to the load.
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The effective pulling force that is used to control the load may not work if there is a sudden gust of wind passing by when the load is high up and clear of surroundings, the load may swing. Not all load swing caused by wind can be eliminated, but it can be minimised by orienting the load to the smallest sail area. Another potential disadvantage of tag lines in this situation is the tag line may get caught onto surrounding obstacles/structures.
With remote control rigging technology, control of the load while hoisting the load to a high up position can be managed.
A 5 tonne, 3.2-metre-long chiller unit was lifted 90 metres to the 28th floors for replacement. The replacement was carried out via main window on Level 28. Narrow access through the façade of the hotel required precise maneuvering of the chiller. To make precise control and rotation of the load at 90m height possible, a remote-controlled spreader system with a remotely rotator was used.
With this system, mobile phone/tablet interface were used to enable loads to be easily lifted from and delivered to precise GPS coordinates. This overcame the need for human held taglines to control free-swinging or suspended loads and eliminated risk of the taglines contacting the hotel facade. The lift was controlled by a single dogger at the landing point inside the building, it saved at least 2 doggers (on very long tag lines) and shortened the cycle times due to accuracy of the smart technology and eliminated building damage due to precision.
How to adopt new technology safely?
Innovation in technology is essential for the development of our society. New technologies bring safety benefits to our industry in different areas. Modern cranes and rigging gear are now designed and manufactured to higher safety requirements compared with what we had 20 or 30 years ago. With all the changes happening, however, our safety principles are always the same – for any lift, planning, assessing risks and risk control should be conducted for all aspects of your lift.
The benefits and risks of adopting new technology for any lift should be considered. In other words, with all the benefits of the remote-control rigging system mentioned above, there are some key points to consider:
- Because of all the new technology used in these devices, the weight of these units might be more than what you expected and could exceed the rated capacity allowed for the crane you selected
- Will the size and shape of the unit cause any problem with wind? All wind effect may not be eliminated by only rotating the load but is dependent on the load shape
- When you use these units together with other rigging gear, check if they are compatible and the right capacity for each other
Again, work as a team to plan the lift, assess the risks and control the risks to make sure you have a safe lift.
The CICA Technical Corner is made possible in part by a contribution from IncoLink.