Anti-clash tech on the Burj Plot
Emaar Properties' Burj Plots 55-57 & 58-59 built near Burj Khalifa
Emaar Properties’ Burj Plots 55-57 and 58-59, high rise towers being built within a stone’s throw of the Burj Khalifa in Downtown Dubai, featured numerous tower cranes on a tight site.
For major job sites in the Middle East, with 10s of tower cranes, anti-clash or anti-collision systems are in widespread use. Using sensors on the cranes, the systems work to automatically prevent a clash between the jibs, in the case of operator error.
Several companies provide anti-clash, among them SK Solutions. Its CEO, Dr Severin Kezeu, is also the inventor and designer of its proprietary system, called Navigator. Kezeu says that SK Solutions can supply a safety integrity level (SIL) 2 monitoring system, above a SIL 1 system.
The distinction lies in part on the possibility of a sensor failure, but is a complex calculation based on all factors in the monitoring system.
In a category 1 system, the efficacy of sensors may bee checked periodically, such as by resetting them at the beginning of each shift.
Al-Futtaim-Carrillion is one of the major users of the SIL 2 anti-clash system. For AFC, an ‘incident’ in Muscat in 2009 demonstrated the weakness of a category 1 system, after one of the anti-clash sensors on a crane failed.
There was no clash or accident, but the potential was there. For a period of time the crane was in use without the protection system in place, reliant only on the operator.
Unsurprisingly, the incident resulted in a number of late night phone calls to have the sensor fault resolved.
Yet, in a category 1 system there is no solution to avoid this, says Kezeu, since the senor can fail between checks.
“You can make a check, but you have to trust the operator.”
AFC were not the only organisation to have noticed the deficiency. The French military, says Kezeu, had already asked him to create a system to be used on their vehicles in the field that would have redundancies, able to detect if there was a problem with any of the sensors.
Installed in 2007, the French military had exclusive use of the system for three years, after which SK was allowed to disclose the product’s existence and market it commercially, in 2010.
“The difference between a category 1 system and SIL 2 is the redundancy. Everything is redundant. With SIL 2 we can guarantee that there will be no clash. Cat 1 is help, assistance. SIL 2 is insurance,” says Kezeu.
Indeed, it’s not just a sales pitch: SK Solutions can take on the liability for a clash accident between tower cranes on a job site.
The SIL 2 system was introduced to Mike Quinn, construction services manager, at Al-Futtaim Carrillion.
After the weakness of a category 1 system was exposed by the incident in Oman, AFC agreed that the company needed to update its anti-clash systems, and AFC became the first company in the world using the SK Solutiuons new SIL 2 anti-clash solution. Every AFC tower crane in the Middle East is now operating with this level
“We’re using SIL2 because we have a responsibility to raise safety practices in everything we do,” explains Quinn. But the use of an anti-clash system doesn’t mean relaxing operator practice. For Quinn, the safety system is a back-up only, one that ideally should never need to be used.
“We have been using anti-clash for many years, across the globe, and view it as a PPE (personal protection equipment), like the helmet, and it’s usually your last line of defence.”
“We put systems in place on site where the operators, the banksmen and the riggers all work together to a known system, and communicate to each other before the tower crane is allowed to move.
“But as with all systems they’re not fail-safe, hence the reason why we use anti-clash. It’s not our first defence, but it’s certainly our last. If we have to use the anti-clash, it means something else has failed.”
Indeed, companies utilising anti-clash may need to be on the guard against operator complacency.
Stuart Foster, project manager with Al-Futtaim Carillion on Emaar Properties’ Burj Plots 55-57 and 58-59, says that training of operators has not changed. All are certified, and regularly undergo retesting.
“We haven’t changed the intensity of the training we put in place for operators. You can’t allow them to become lenient in the way they work or forget the correct procedures.
“SIL 2 is a safety blanket, but it doesn’t negate the need for paperwork and auditing, the training of our men, or the way we operate our cranes.”
And at the end of the day, a poorly trained operator will be as inefficient as he is unsafe.
“You don’t want to lose the art of being a rigger, or a banksman, or a crane operator,” says Foster.
While companies first and foremost look at anti-clash as a safety measure, there are productivity spin-offs as well.
Foster says that being able to view the movements of the cranes on a computer monitor from the project office has improved efficiency on site.
“You can see how much usage you’re getting out of your cranes, and times when they’re slow getting up and running, such as after breaks.”
With daily competition for hook time on the towers, project managers can see the position of cranes in real time.
Foster had overlaid an outline of the towers on the screen of the monitors, something which software updates will do automatically in the future.
“You can schedule your work so that you can increase the efficiency of your crane usage, essential, on such a tight site like this one, with such high towers and restricted space.
“If you’ve got two trades trying to work with two cranes in an area at the same time, you can be restricted where you can slew, and sometimes you’ll end up sending the crane the long way, which will increase the period it takes to complete a certain job,” he explains.
SIL 2 also allows the operator to take the shorter route into a clash area where another crane is working.
While the project is coming to an end, with only three tower cranes remaining, the ability to see the position of the cranes on the monitor in real time was invaluable when communicating with workers on the site, especially during the busy period when they were erecting 70-80 precast panels a day.
While tower crane anti-collision systems can prevent these cranes from clashing, if installed only on the towers they provide no protection against an accident involving, for example, a mobile crane or concrete placing boom.
Kezeu is keen to stress that there is nothing about his system that is designed specifically for tower cranes; rather, the Navigator sensors can be placed on any dynamic object, and incorporated into the monitoring system.
“The technology has been designed for any type of vehicle. It is universal.”
He’d like to see sensors placed on all major machines on work sites. But while there are safety advantages, he envisages monitoring of equipment on-site to lead to efficiency advantages for operators.
“The future of the next ten years will be about monitoring the business intelligence of work sites.”
“We’ve come a long way from where we were four-five year ago”, says Quinn, on the benefits of using anti-clash.
Whether companies will embrace Kezeu’s vision of a fully monitored worksite depends in a large part on how much they’re willing to pay.
As always, with a premium product focused on efficiency, the case has to be made that the initial outlay will be returned through worksite savings. Quinn is unequivocal that from a work place efficiency perspective, the monitoring of tower cranes has improved more than just safety.
“[On another site with 14 cranes operating], the system allowed those cranes to work so much closer together and allowed so much more hook time in clash areas.
“A site like that is under so much time pressure, it allowed us to be more efficient with our hook time. If a system is shown to us and demonstrates work efficiencies and monetary savings then we will always take a closer look.”
Whether he’s convinced of Kezeu’s vision of a fully monitored site remains to be seen. “As a business we want to be more efficient, and any tool that allows us to do that we will look at. If we can balance the cost, and if it saves us money, we will do so.”
The French Connection
It’s no accident that many companies supplying tower crane anti-collision systems are French, as it was the first country to require the systems be used on worksites, with a mandatory order coming into effect in 1987.
That’s in distinction to Germany, where anti-collision systems are not frequently used or required, instead relying on the training and participation of the drivers.
For contractors, there are a variety of companies in the market, all offering different solutions to the same problems.
Variations in technology can include questions about whether the sensors communicate through radio frequencies or WIFI, or solutions for mobile cranes entering into the tower cranes’ zone.
What is SIL2?
The safety of a system such as a tower crane anti-collision solution is a complex calculation based on all factors in the monitoring system.
SK Soliutions describes it as: “to guarantee an unbreakable system and a high level of safety and reliability, an anti-collision system must be at least a SIL2 (Safety Integrity Level 2) system according to international standards ANSI/ISA-S84.01 and IEC 61508.
“A Safety Integrity Level is a statistical representation of the reliability of a Safety Instrumented System (SIS) when a process demand occurs. Safety instrumented systems are used to provide safe control functions for processes.
SIS typically are composed of sensors, logic solvers and final control elements. The higher the SIL (as measured on a scale of 1-4), the more reliable or effective the system.”
Another standard can also be used to evaluate anti-clash systems, the European Standard EN14439, formulated by a number of organisations, both manufacturs and governmental.