Let’s face it; building sites are generally pretty grim places to work. A bleak landscape with heat, dust and occupational hazards are quite the industry norm out here.
While there is little that can be done about the heat and the dust, the other aspects are a little better on the site that we are visiting today.
For one, the skyline is far from bleak, thanks to the ever-changing vista across the Arabian Gulf, but more importantly the workplace hazards have been reduced a little, thanks to a modern anti-collision system fitted to the tower cranes working on site.
To be fair, this site is hardly the most complex in terms of cranes. Five fixed-jib Korean units are working on the resort which will comprise of the main hotel block, shaped roughly like a ‘W’, with a further block on the back.
The rest of the development has half a dozen other buildings, plus various smaller structures, the shape of which is becoming apparent now that the formwork system is beginning to rise out of the ground.
BREAKWATER
The project itself is quite interesting. Situated on the breakwater of the Palm Jumeirah next to the Atlantis Hotel, this is surely one of the most prime real estate sites in the world, whatever the economic climate.
Mirk General Trading owns the local franchise of posh French hotel chain Sofitel and it has appointed Burt Hill as the lead consultant and Evan Lim – Penta Construction as the main contractor.
Because the development is on the curved breakwater of the Palm, it is not completely symmetrical.
Instead it resembles a kind of ‘curved oblong’ and as such the pattern that the cranes have been divided into meant that there are overlaps on each, as well as ‘no hoisting areas’, namely zones that the cranes are not permitted to slew into.
Working on separate structures at the same time, means that communication might not always be clear between teams, and as such the project manager took the decision to install an anti-collision system known as the AGS AC3.
ACCURACY
Like most operations there is a need and an obligation to measure the wind speed accurately. This is why part of the system includes an anemometer, a device not dissimilar to the airflow meter on a car, and works similar in principle to an old fashioned weather vane.
This is linked to a real-time display showing the wind speed, and a siren sounds and lights flash if this speed is exceeded. This is a fairly fundamental piece of kit on any tower crane, but the box sullied to the Sofitel site can be further enhanced with an orange flashing beacon and a very loud 115db siren in case the tower is being operated on the ground via remote. You can also have data links to a repeater or a repeater-recorder if needed.
If the site manager had so desired, a number of wireless cameras could also be linked in to this system. Obviously, the primary use is to lose ‘blind spots’ around the operator, but it can also be positioned above the winch to make sure that the cable is being wound correctly.
The AC3 system comprises of a computer, and the crane itself is rigged with sensors which can determine things like the hook height, and the position of things like the position of the jib and counter jib of all the other cranes on site.
As the cranes slew, an alarm is sounded if the booms get too close together. If no action is taken by the operator of one or both of the cranes, then the brake will be automatically applied.
There is another module available which will sound the alarms if the hook height drops below a certain point over the ‘no hoisting’ areas.
This, understandably is to prevent members of the public from getting bonked on the head by a crane hook. Of course, hi-tech cranes are always useful on a job site, but they do not build the whole structure of course.
On the Sofitel site, a number of smaller mobile cranes belonging to subcontractors are also in use to sling items around. The heavy excavators have moved out, but there are still a couple backhoe loaders for lighter trenching and loading jobs.
Apart from that, the site is alive with the hustle and bustle of a busy construction site – which itself is nice to see in the current financial climate.
Whatever the season, the site is in a good spot, so hopefully the collision-proof cranes will continue until the structure is finished.
With crane safety still a serious concern around the region, we hope similar systems will find their way on to other sites in the region soon.
Tower Cranes in Tight Spaces
Cranes also face dangers on very tight workspaces. Here are a couple that are currently jammed in a tight site in Singapore.
Bovis Lend Lease construction superintendent Geoff Barrow says that the irregular-shaped site has a 95 m frontage on Orchard Road and 70 m on Somerset Road, with the other two sides hemmed in by other buildings.
Sited directly above one of the busiest stations on Singapore’s metro and with Stamford Canal running through the site, space for the contractors has been severely constrained.
“We are very tight for space on this site, with buildings on either side of us,” says Mr Barrow.
“Conventional tower cranes would have been very limited in operational terms and might not have given us the construction speeds we need. The luffing jib cranes have however resolved the problem of lifting within this very confined area.”
Liebherr’s HC-L series of luffing jib cranes has been designed to work in extremely restricted spaces, while still able to slew through 360 degrees.
The 160 HC-L 8/16 Litronic cranes on the site can work with the jib raised to 70 degrees and have a maximum lift capacity of 16,000 kg. With the jib fully extended to the maximum of 55 m, the crane can lift 2,000 kg.
Mr Barrow says that the building will be 45 m in height, which means that the 37.5 m tower height of the 160 HC-L coupled with the high placing power of the jib makes this model a very appropriate one for the project.
The average load being carried by the two cranes is around 3 to 4 t, he says.
The cranes are located in two of the lift shafts of the building, with the contractor having had no other choice but to place the foot of the cranes in the middle of the temporary course of the Stamford Canal, temporarily diverted while construction work is underway.
AST, at the request of Bovis Lend Lease, have arranged for the two units to be painted white and red to match the contractor’s corporate colours.
Crane anti-collision systems
There are dozens of anti collision systems on the market, and different experts will give you different opinions on different types.
Shata M , a safety consultant, and a member of the UAE’s crane safety forum suggested that the AGS system mentioned in the article is the best all round kit.
Other types are available, but he points out that “not all systems are compatible with every tower crane”.
He advised checking the systems carefully and seeking independent advice before committing.