Tower cranes remain a constant presence on the skylines of major cities. Cranes and Lifting examines the real and hidden costs of adopting anti-collision systems.
Should there be more regulation around the operation of tower cranes, especially when multiple units are operating on the one site? And with many tower crane operators sceptical, do anti-collision systems enhance or hinder the safety and performance of tower crane operations?
Anti-collision systems are not mandated in Australia but in countries like France, they have been mandatory on all tower crane installations, under a Ministry of Labour directive issued in 1987. During a recent conversation, a local construction manager told Cranes and Lifting that, despite having multiple towers working together, he’d chosen not to use any anti-collision systems, as it caused unnecessary stoppages and would slow down his work schedule.
In the UK, prominent tower crane operators have expressed doubts about anti-collision systems, saying that they won’t actually stop cranes hitting each other.
French companies still use anti-collision systems, even in countries where they are not required to, believing the total cost analysis of using anti-collision systems is positive.
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The high-rise residential boom has seen Australia’s eastern coast host more cranes than the entirety of North America. Tower cranes are integral apparatus for high-rise construction, yet they can pose dangers to site personnel and adjoining properties. Legal cases relating to airspace rights and crane oversail have been increasingly subject to media coverage and scrutiny. With prolific crane use, crane safety must be of paramount importance.
In 2016 WorkSafe ACT recorded a number of concerning incidents involving tower cranes which had potential for serious injury or death.
Of significant concern to WorkSafe in the first half of 2016 was the recording of a number of notifiable incidents involving tower cranes over an eight-week period. The first incident involved the slewing jib of one tower crane coming into contact with the hoisting ropes of a second tower crane located on the site. A second incident on another site involved two tower cranes colliding due to a lack of communication between the crane operators. Another incident, which occurred on a different site, involved the jib of a single tower crane being struck by the raised boom of a concrete placement truck. Again, lack of communication and collision avoidance systems were the main contributing factors to these incidents.
Other notified incidents involving tower cranes were due to:
• a system failure with manufacturer’s instructions when installing a luffing cable on a jib; and
• a qualified electrician working on a heater in a tower crane cabin receiving a serious electrical shock and electrical burns.
In response, the ACT Work Safety Commissioner issued a Crane Safety Alert followed by a well-publicised audit of all ACT construction sites that had a tower crane in operation. In all, 21 cranes on 17 sites were comprehensively inspected from July to October 2016.
The inspections covered both the physical aspects of the crane as well as checking all appropriate paperwork associated with crane set-up and operations.
Overall, compliance was found to be poor as a number of key safety areas were not being appropriately addressed on many sites, including:
• non-compliant operation of zoning and anti-collision systems or failure to have a back-up form of communication;
• failure to verify electrical supply and wiring connections in accordance with AS/NZ 3000:2007 Electrical Installations;
• inadequate Safe Work Method Statements (SWMS) including the failure to have a site-specific risk assessment; and
• inadequate or non-existent emergency rescue procedures in terms of lack of documentation, no testing of procedures and a lack of trained crew to undertake rescue procedures.
Crane failures, in Sydney in 2017 included the collapse of a tower crane operating on a high-rise apartment block at Wolli Creek due to a mechanical/engineering fault. Worryingly, the crane fell onto an adjoining high-rise residential building. Given incidents such as these, it is evident that crane failures have a very real possibility of damaging adjoining property and the potential to harm residents and the public.
The latest European tower crane safety harmonisation, EN14439:2006, requires that tower crane manufacturers wishing to sell their products in the EU make it possible for users to install anti-collision systems.
In practical terms, this means that users should be able to fit sensors to slewing rings, hook carriages and luffing jibs, connect the whole system to a power cable, and have a machine interface access the crane’s braking system. The harmonisation echoes the requirements of the 1998 UK interpretation of the Machinery Directive, which states, in clause
4.1.2.6 b, that:
“Where several fixed or rail-mounted machines can be manoeuvred simultaneously in the same place, with risks of collision, such machines must be so designed and constructed as to make it possible to fit systems enabling these risks to be avoided.”
This requirement to ensure anti-collision systems can be fitted reflects a deeper commitment to their use in many neighbouring countries of the region. In one country, France, the devices have been mandatory on all tower crane installations, under a Ministry of Labour directive issued in 1987. This 20-year requirement to make use of the systems has meant that French companies such as AGS, SK Group, SMIE and Ascorel have come to dominate the market for the manufacture of third-party anti-collision systems.
There are two types of anti-collision systems; one is a crane to crane where the cranes have to communicate their positions with each other, the other is Restricted Slew Zone where cranes are prevented from either hitting other cranes, buildings or oversailing areas like schools, powerlines, railways and private properties.
One of the big issues in Australia is some tower crane fleet owners will buy a SMIE, others Ascorelor or an AMCS system and none will cross communicate. This means the prime contractor will want to use whatever equipment they have, and subcontractors have to fall in line.