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Our method of using Derrick Cranes range has been designed to provide a solution for the dismantling of tower cranes, offering our customers a safe and comprehensive service.
Background
In September 2018 a tower crane jib collapsed in mumbai while the jib was being dismantled. Three workers were on the jib and suffered various injuries. Parts from the jib landed on an adjacent building. The building and the street on either side of the building were closed for the recovery operation.
In November 2019 a climbing frame was being installed on an existing tower crane. The climbing frame lowered uncontrolled approx. 3 m to the floor below, causing minor damage but no injuries.
In both incidents a system of work was developed that was different to that provided in the manufacturer’s manual.
This alert focuses on the activity of erecting, climbing or dismantling the tower crane. For more information on other matters such as pre-erection inspection, post-commissioning criteria, geotechnical inspections, footing design and traffic management, see further Information documents listed below.
RISK
Erection / climbing / dismantling of tower cranes is a potentially hazardous process involving working at heights, awkward postures, lifting and aligning components of significant size and mass and installing temporary support systems. These are all often performed under significant time pressure due to the need for road closures, suitable daylight hours or short weather windows.
It is acknowledged that there are rare occasions when it is not reasonably practicable to follow the erection/climbing/dismantling process provided for in the tower crane’s manual. Examples may be cranes provided with an inadequate or non-English manual or exceptional site restrictions that prevent following the manual’s instructions. However, deviating from the recommended process that has been considered in the design of the crane, brings the potential for significant additional risks such as overloading components, untested or uncalculated methodologies and even collapse.
For example although it may be necessary, and some aspects will be safer, when splitting the jib rather than installing / removing in one piece, splitting introduces additional risks. These risks include those created from moving the jib supports and inserting/removing pins well out from the tower, i.e. additional work at heights, potential falling objects and potential support problems, which all need to be considered in the overall planning.
Action required by developer / Civil contractor / builder
Consider the crane erection / climbing / dismantling needs when designing buildings and selecting the crane(s) for the building’s construction, noting that the needs for dismantling may be different from erection as the building and road conditions may have changed substantially. Issues include:
- Location of the tower crane to provide for safe erection/dismantling, not just optimal coverage of the site.
- Access for cranes and trucks required for erection and dismantling.
- Mass of individual crane components to be lifted during erection/dismantling.
- Crane component pick up and drop off locations.
- Providing crane setup locations by considering the crane capacity, and thus size, which may limit potential set up locations, and that the dismantling crane and location may need to be different than that used for erection.
- Checking that the crane supplier has a dismantling plan and being aware of any limitations this puts on the project, e.g. sequencing of roof works, or delaying ground works (landscaping, pool installation etc.) to leave space for the dismantling crane or trucks.
- Monitor the area for works on adjacent sites, roadways etc. that might prevent the dismantling as planned, e.g. erection of other buildings, underground services, street light poles, power lines, street furniture etc. If any of this occurs, alert the crane supplier and work with them to develop an alternative dismantling plan.
- Obtain, or ensure others have obtained, any required authorities for road closure / occupation and CASA acceptance for any airport restrictions.
Action required by crane erector/dismantler
Understand the manufacturer’s recommended method of erection/climbing/dismantling and follow it where it is reasonably practicable to do so. If this is not reasonably practicable an alternate method may be developed using risk management principles in consultation with appropriate parties including the crane manufacturer.
The alternate method should be documented in detail. The crane manufacture or, if the crane manufacturer no longer exists or is not prepared to assist, other suitably competent person(s), such as an independent engineer experienced with tower cranes should be involved in developing or checking the alternate method.
The alternate method should be checked, including with appropriate calculations, to ensure the method maintains the crane and its components in a safe state, e.g. counterweights may need to be removed before removing the jib, new temporary support connections to be checked for structural adequacy, or the mass of components not normally preassembled checked for the ability to be lifted and supported.
This alternate method, and the checks, should be finalised well in advance of the commencement of the activity to allow for consultation with all those involved in the activity and with consideration taken of any feedback they provide.
Persons undertaking the work should be competent in the tasks they will be involved in, and must have the appropriate high risk work licence if performing licensed work. They should also be provided with detailed information as to the erection/climbing/dismantling method and their roles in the method, with extra focus on any changes from the method they would normally use.
Whilst it may not be reasonably practicable to cover every possible emergency in detail, an adequate emergency plan should be prepared for the work covering procedures for any reasonable foreseeable emergencies, such as recovery of an incapacitated worker(s) from the various locations on the crane, whether incapacitated by a medical condition, a fall arrested by fall arrest equipment or structural failure of the crane.
The plan should provide for appropriate equipment and workers to deal with the first response and those workers must be trained in its implementation. The plan should allow for contingencies in the event that some persons and equipment are unavailable as a result of the emergency.
Documented detailed information should be readily available on site should the workers need to check on any details of the erection/climbing/dismantling method. This should detail each step in the alternate process, including the sequence and equipment to be used and be in a format that is readily understandable to those performing the work.
Where an incident, or near miss, with potentially serious consequences does occur during the erection or dismantling process, when performed in accordance with the manufacturer’s instructions, the crane manufacturer should be advised in the interests of preventing similar occurrences.
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