European standards call for change in crane electronics
By Laura Hatton21 January 2013
Electronic systems have been in cranes for years but proposed changes to the European EN 13000 standard for wheeled and crawler mobile cranes will see a step change in the monitoring and control systems. Colin Sowman reports
European standard EN 13000, introduced in 2004, included the requirement for the rated capacity indicator to trigger visual and audible warnings, not only to the operator but also to other site users when the system is activated. The standard was updated in 2010 and, among other things, required the RCI/L override switch to be positioned outside the cab to counter the risk of constant overriding.
Two major changes will be made to EN 13000 in the next few years, the first of which will be proposed amendments to the 2010 version that will require the monitoring of outrigger positions. Second, a revised version of the standard will be introduced a couple of years later with more far-reaching changes than just the electronic systems. Following each change the crane manufacturers will have a set period to ensure that the specification of their new cranes meets the required standard.
By 2015, Tim Watson, technical consultant to the Construction Plant-hire Association in the UK, expects the amended standard will require electronic monitoring of the outrigger extension, as this is where most problems arise. This system is likely to confirm whether the outriggers are extended to the degree required for the duty selected. A warning will signal the operator if they are incorrect. The operator will be able to cancel the alarm – for instance in the case that the outriggers are asymmetric but the boom only needs to slew through a narrow arc. While the system will allow the operator to carry on working, the machine’s data logger will automatically log the alarm being cancelled. If there is an accident or incident operators can be called to account for their actions.
A couple of years later the full revision of EN 13000 is likely to require a full interlock system to prevent the crane from being used if the outriggers are not correctly deployed. It is unlikely that the operator will be able to override the system. Similar interlocking systems are already mandatory on the likes of mobile elevating work platforms (MEWP) and truck mounted knuckle boom loader cranes.
“MEWPs are relatively simple compared to a mobile crane. Unlike a mobile crane, a MEWP has a defined configuration and a light load which doesn’t vary greatly. On the other hand a mobile crane can be configured in many ways with different jibs and counterweights, the outriggers may be deployed asymmetrically and the load and radius can vary considerably. This means that there are many variables which have to be processed quickly and reliably,” says Watson who is a member of the committee drafting the amendments to EN 13000.
“This will take additional instrumentation, including a turret sensor so the system knows in which direction the boom is pointing,” Watson says. He also highlights the requirement for significant processing power to be able to instantly calculate the rated capacity for each configuration, including load radius, jib length, counterweight and outrigger positions.
“Monitoring systems on cranes already measure the effect of the load and if the outriggers are set asymmetrically the system will have to calculate in real time how far the boom can be telescoped and slewed before it could affect strength and stability. The system will then impose a limit to ensure that point cannot be exceeded,” Watson says.
As with all new standards, EN 13000 will only set requirements and not specify how that requirement is to be achieved, to leave the way open to innovation. It gives rise to the potential for a system monitoring the pressure each outrigger is exerting on the ground. If the pressure under one or more outriggers is diminishing, it may restrict and slow slewing, telescoping and boom movements in the same way the RCI does when approaching the edges of the working envelope.
Once the full revision comes in the operator may not be able to override the warnings and interlocks on new cranes, although the standard may require the override key to be in a box outside the cab to continue to allow the machine to operate for a limited time at a reduced speed. This may frustrate some operators and it is not unknown for individuals to try to circumvent such safety systems.
The primary legislation for the supply of machinery in the EU is the Machinery Directive which was also updated in 2010. This update introduced the concept of “reasonably foreseeable misuse” where it can be reasonably foreseen that a safety system can be circumvented or the machine used for duties for which it was not designed. One example is circumventing the system which reduces the travel speed on a self propelled MEWP when the basket is raised. Machinery designers and manufacturers must now take account of such reasonably foreseeable misuse.
“If it was as simple as sticking the limit switch down with a piece of tape then that would be reasonably foreseeable misuse and the manufacturers would have to devise another method of sensing the basket position,” says Watson. If, however, an individual opened the junction box and started bridging out safety circuits, then that would be abuse, for which the manufacturer is not responsible. Watson says that this is the reason why many manufacturers are now using proximity sensors rather than limit switches as they are more difficult to override; but their use requires a system to monitor the sensor position rather than a simple, cheap and reliable switch which is either open or closed.
With the increase in computing power comes the potential to add other systems such as sensors to detect the vicinity of electric cables. According to Tim Watson the Americans are very keen on this technology but the Europeans are less so because of the unreliability (perceived or otherwise) of the sensors.
“If you include a system like this it has to be reliable because people come to depend on it so, if it fails, it can expose individuals to a significant risk of death and serious injury,” he says.
While the capability will be there to do more, it is unlikely that the operator will be provided with much additional information beyond what they get at the moment. They will still have to select a duty and part of the checking process of the RCI will be whether the outriggers are in the correct position, of extension and angle – if not the system will not allow the crane to be used.
“What the operator needs to know immediately remains the same: what am I lifting, what radius is it at and is it within the duty that I have selected? Beyond that everything else is of secondary interest,” Watson says. While additional information will be in the system, the operator may have to drill down through the menus to find it.
As has already been seen with earthmoving equipment, electronics have the potential to make the whole machine operation more efficient, saving time, money and reducing pollution. Cranes are likely to follow.
There are already examples of that electronic data being relayed wirelessly to the machine owner or even the manufacturer for remote diagnostics. This gives rise to “spy in the cab” type objections. Managers do not have the time to sit and watch the fuel consumption and coolant temperature of each machine on a site. What is far more likely, and is already happening with some crane owners (see box), is management by exception where alarms and over-rides are transmitted back to base. Then, if the manager wants to question why an operator has just overridden an alarm, they can call to ask the question.
This technology can have both positive and negative sides for crane owners as, on very complicated lifts, the manufacturer or other experts could view live data from anywhere in the world to help ensure an operation goes smoothly. The flip side is that the management has to manage the behaviour that the new data is highlighting. For instance, if an operator has been repeatedly overriding alarms and their crane is then involved in an accident, the accident investigators could legitimately ask why management failed to challenge the operator’s behaviour before the accident occurred.
While forthcoming generations of cranes will have interlocks and other safety systems, however, older machines will be around for many years. “This makes it even more important that operators are properly familiarised with each crane they use – especially when they move from a newer to an older machine,” Watson concludes.
Crawler crane rental specialist AGD Equipment in the UK has been using the telematics incorporated in the tracking systems fitted to its cranes to monitor when the operator presses the reset button. “We mainly fitted the telematics to keep track of the machines that went out on self-drive hire and the override monitoring isn’t very sophisticated. Most of the activations have been when the operator is rigging the crane but it has highlighted a few incidents where we have had to ask questions of the operator,” says Robert Law, AGD managing director.