Hydraulic: 1. adj. – of water or other liquid conveyed through pipes and channels; operated by movement of liquid (Source: The Concise Oxford Dictionary)With the above definition, we can be justified in saying that hydraulic engineering dates back thousands of years. Ancient Egyptians and Mesopotamians built irrigation canals; the Euphrates was diverted into the Tigris to supply water; and a dam was built on the Nile six thousand years ago.

The history of using hydraulics in lifting machinery is not quite so old, but still goes back more than 50 years. It is unsurprising, therefore, that there is not too much rapid development in the field of hydraulics today.

Where there has been significant progress, however, is in the electronic control of hydraulically operating systems. Manufacturers of knuckle boom truck loader cranes are finding new ways to make crane movements smoother. This is particularly significant on a loader crane because speed is often an important factor in loading operations, and loader cranes have a natural tendency to bounce as they pick up a load, swing it over, and put it down. The technical term for this bouncing is dynamic oscillation.

Boom control becomes more of an issue the longer crane is, and cranes are getting longer all the time, it seems. Uncontrolled movements represent not just lost time but also a potential safety hazard. They also cause wear and tear on the crane and shorten its life.

A common focus of development among loader crane manufacturers is how to use electronically-assisted motion control systems to reduce the dynamic forces on the crane.

Austrian manufacturer Palfinger says that it seeks to ‘continually develop systems and components which minimise the inherent disadvantages of crane operation, and thereby market products which alleviate crane operation and at the same time increase operating efficiency’.

It is not alone. So do most of its competitors.

A recent innovation from Palfinger is its Active Oscillation Suppression (AOS) system, integrated into its Paltronic 50 control system. AOS uses sensors to measure vertical oscillations. Pressure peaks in the cylinders are measured and processed by the Paltronic 50 system. The necessary corrective movements are then introduced in the elevating cylinder of the boom via the control valve.

Fassi Gru of Italy has also spent time and money in research and development, resulting in multipurpose load sensing hydraulic distributors. Its FX load control system manages load conditions electronically by monitoring the use of the crane within the established optimum values. Data is displayed on a monitoring screen.

Electronics cannot yet take the place of good mechanical engineering, however. Hiab’s control systems manager Lars Andersson says that the most we can expect from electronic controls is to optimise performance.

‘Electronics alone are not yet a shortcut to better performance. It still relies on good mechanics, something that not even the most advanced electronics can take the place of,’ he says.

In Hiab’s case, electronic controls have actually improved the lifting capacity of loader cranes by as much as 40%.

The trade-off for improved control can be a loss of speed, but in Hiab’s case this is small or even unnoticeable.

Says Anderson: ‘It’s the equivalent of about three minutes in five hours. And during these five hours there is at least 20% more lifting capacity than before. In loader cranes with a long outreach, the increase in lifting capacity is as much as 40 per cent. In practice, also productivity improves. Since the hydraulic system optimises oil distribution to the different functions, the crane can be used more quickly and without interruption. The crane functions in constant motion, steadily and reliably.

‘The advantages are emphasised when the hydraulic equipment is used for things like bucket work. With the same oil flow, our HiPro crane has 5% more productivity than a crane that doesn’t have the corresponding electronic functions.’

Hydraulic gantries

It is not just cranes that are benefiting from improvements in electronic control systems. J&R Engineering, a US manufacturer of hydraulic gantry systems, has recently improved the radio remote control operations of its Mini Boom Gantry. The Mini Boom Gantry was developed in 2003, and first used in October of that year by rigging company George Young Company of Philadelphia to relocate the famous Liberty Bell.

The MG88 Series Mini Boom two leg gantry system has a lifting capacity of 20t up to a full height of 6.7m. With four legs it can lift 40t. Unlike J&R’s larger system, the Mini Boom has round cylinder legs, but like the larger square-section gantries, the Mini Booms have a protective outer tube that can take side loading up to approximately 5% of the total vertical load.

The new remote control system has a continual read-out display for each leg of the gantry, showing both the vertical stroke on each lift boom as well as the current load on each.

An on-board computer matches each cylinder stage with an individual oil pressure. The computer adds an additional safety feature by preventing the gantry from lifting a load in excess of its specified capacity.

The lift housings are 813mm wide and 1,676mm long and each weighs approximately 1.3t. The gantry is self-propelled: there are four wheels per housing and they are each 152mm wide, set as a 1,397mm wheel base. The steel wheels can be swapped out for cushioned ones when working on floors likely to be scratched or damaged.

Similar to 4 Point Lift Systems’ Mini Jacks Model 2020, the J&R Mini Boom Gantry is powered by 110-volts. Each leg uses a 1.12kW (1.5hp) single-phase electric motor pumping an internal reservoir of only 75 litres (20 gallons).

The radio remote control box operates each housing either simultaneously or independently. Each leg has its own toggle control combined with a master joystick. The joystick allows variable speed cylinder extension/retraction as well as variable speed propulsion.

George Young Company’s operator, Kevin Dougherty Sr., says of the new control system: ‘The control we experienced in lowering loads is fantastic. The system’s ability to smoothly “creep-speed” position loads is spectacular.’

He adds: ‘The smoothness of this generation of gantry is even better than when we hoisted The Liberty Bell.’

Dougherty also clearly likes the radio control option. ‘Our experience has shown that the control cords are the one’s most prone to job-site damage. So obviously when there is no control cord, there is no chance of damage,’ he says.

An additional safety feature is a ‘return to zero’ elevation lift readout. Once the load’s rigging has been fully tensioned, the lift readouts can be set to zero. ‘This can be a wonderful equalising feature when one pair of housings is set at a different starting elevation to the second set or when the lift beams start at different elevations,’ Dougherty explains.