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Into the danger zone Safety and logistical factors are driving the development of remote controlled construction plant. Richard Thompson reports.

Ask a hundred engineers how to build a tunnel below one of the world's roughest stretches of water and you will doubtless receive a hundred different answers. Most however, would probably specify remote controlled plant.

The whole point of remote control is to allow work to be carried out safely in hazardous environments. Today the most advanced robot technology is used in the most dangerous situations, such as bomb disposal, work inside nuclear reactor cores and digging lava flow channels on active volcanoes. As the technology develops it is likely to be used in increasingly demanding situations. These could include the placing tunnel segments for ambitious projects like Symonds' Irish Sea immersed tube tunnel project (see News).

Manufacturers say that safety has always been one of the strongest technology drivers for construction plant. Increasingly tough health and safety legislation and technological advances mean that remote control machines are appearing on construction sites more and more often.

Of course, remote control has been on site for a number of years. Concrete pumps, for example, guided by operators using chest packs, are now common place. But these have theirlimitations. Control units for the equipment are connected to the pump by an umbilical cable. This arrangement is fine for static plant items like pumps but is less practical for mobile equipment.

The next advance has been to remove the physical link altogether. Crane manufacturers pioneered this five or six years ago and operators watching a television screen in a control office can now carry out lifts using radio signals.

More recently compaction plant companies such as Bomag, Benford, Rammax and Wacker have introduced remote control machines for trench compaction. Many used last week's SED '98 plant exhibition - to show off this equipment.

Bomag GB general manager Alex Ferris believes it is natural that trench compaction should be the next area for the development of remote control construction plant. 'Working in trenches is one the most dangerous areas of construction. Sides can give way without warning.'

Benford, which claims to be the first British manufacturer to produce remote control construction equipment, used SED to showcase its range of infra red guided trench rollers. These allow the operator to guide the machine from as far away as 20m.

Though radio signal control was an option for these machines, the company opted for infra red controls similar to those used, in domestic television channel changers for safety reasons.

Project engineer Howard Leigh-Firbank explains. 'Infra red was chosen because we believe it satisfies the tight specifications required to obtain a CE (European quality assurance) mark. The problem with radio control is safety. The machine can operate over a greater distance where it can be hard for the operator to see. Also with radio the machine will still operate even when the operator turns away. With infra red it will only operate when the operator is facing the machine.'

German compaction specialist Bomag launched its BMP851 multi-purpose compactor last year. The machine is unique in that it can be operated by infra red, radio, manual or cable controls. The company prefers the radio control system. Ferris believes 'radio is the easiest system and operators seem to prefer it. The machine can operate over a longer distance, in fact we limit ours to 80m for safety. The big advantage over infra red is that it does not suffer interruptions. Infra red signals can be blocked by objects in the way such as props.'

There are also developments in other areas. Last week Britain's largest plant manufacturer JCB, launched a remote control fire fighting machine.

Developed with the West Yorkshire Fire Brigade, the machine allows firefighters to take cameras into a burning building without putting operators at risk. The machine is based on the JCB Robot Skid Steer Loader which was granted Millennium Product status earlier this year (NCE 2 April).

The loader has been fitted with rooftop cameras front and back which allow firefighters to see inside a fire from a control room up to 100m away. The fire crew can guide the machine using identical controls to those in the skid steer. Radio signals were the only option because the heat energy given off by the fire interferes with infra red guidance systems.

JCB believes remote control will enter the construction industry in a big way. Marketing manager Keith Hoskins explains: 'Remote control was pioneered by the crane industry five or six years ago. JCB dabbled about three years ago with skid steers but saw no market at that time. We looked at skid steers because they are versatile and can be applied to many hazardous situations. Tightening health and safety standards mean that the technology is likely to cascade down into other areas.'

West Yorkshire Fire Brigade technical services manager Noel Rodriguez says the relatively low cost of the JCB machine was its main attraction. 'One of our restrictions was cost, therefore we wanted to stick as close as possible to a machine that was already in production for construction. We looked at all the skid steers and JCB was the most suitable because of its joystick controls. These were the most simple to adapt for a chest pack.'

Another area of construction that will benefit from remote control technology is tunnelling. Tunnelling and pipe jacking expert Barhale used last week's Civils 98 exhibition in Birmingham to show its state of the art Iseki Unclemole Micro tunnelling System. A camera mounted inside the machine allows an operator in the site office to guide the machine using a television monitor.

As technology develops, remote control plant can be expected to be applied to increasingly ambitious projects. Remote control submersible machines could even help place immersed tube tunnel sections in the Irish Sea if the scheme being developed by Symonds ever gets going.

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