Careful climbing25 May 2011
Climbing a tower crane to increase its height relies on meticulous planning, good communication and the skill and dedication of the erection team, if it is to be completed without mishap. The consequences of a collapse are often loss of life, delays to construction programs, criminal prosecutions, loss of reputation and massive costs for all involved. Cristina Brooks reports
In the UK, the law requires that tower cranes are installed, used, maintained and thoroughly examined in a safe manner. The European product standard for tower cranes, EN 14439, sets out safety requirements for tower cranes and climbing systems, whilst British Standard BS 7121-5 gives guidance on safe use, including erection and climbing.
Nevertheless, the tower crane industry in the UK has for some time felt the need for additional guidance on tower crane climbing.
In response to this need the Construction Plant-hire Association (CPA) Tower Crane Interest Group (TCIG) is publishing a Best Practice Guide on the Climbing of Tower Cranes, an 86 page document detailing the planning and carrying out of climbing operations. The Best Practice Guide is supplemented by a DVD, produced by Lend Lease and Select Plant Hire, showing an actual climbing operation from initial planning, through the climbing process to thorough examination and handing the crane back to the user.
Haydn Steele, CPA's Training and Technical Manager, says, "Our aim is to give guidance on the problems people may come across during climbing and the best ways to avoid them. The guide is targeted at a wide audience including tower crane owners, construction companies and the Health and Safety Executive (HSE)."
Steele observes that the development of the guidance has been driven by a number of crane collapses over the last ten years at Canary Wharf and Battersea in London, Liverpool, Croydon and Worthing. "When a tower crane has collapsed or falls over the consequences are often catastrophic. There’s not only a risk to people on the site but also to the public.”
In addition to the terrible human cost, there is a very strong business case for avoiding accidents. Steele says, “Financially, there are direct costs of the accident, which may be covered by insurance and uninsured costs such as delays to the project, the costs of any prosecutions and fines, and reputational costs. The last thing that a contractor wants is a tower crane to fall over on their contract, even if it is not directly the contractor's fault. The damage to their reputation may well have a considerable effect on winning future work."
HSE research supports the idea of big, unrecoverable costs. “The HSE did some work on this in 1997 and at that time they found that for every £1 of insured cost there is another £8 to £36 that is not covered by insurance. In theory if the costs that can be recovered from insurance are £100,000 then uninsured costs could be as much as £3.6m".
Following the tower crane collapses between 2000 and 2007, the UK Health and Safety Executive asked the CPA Tower Crane Interest Group to produce specific best practice guidance for tower crane owners, suppliers and users. The result of this has been a series of guidance documents including Maintenance, Inspection and Thorough Examination of Tower Cranes, Safe Use of Self Erecting Tower Cranes, Safe Use of Top Slew Tower Cranes, Tower Crane Operator's Handbook, a set of thirty Technical Information Notes and now the Climbing Best Practice Guide.
As with all these guides, while they have been written by the industry with input from tower crane owners, manufacturers and users, there has been active support from both the United Kingdom Contractor's Group (UKCG) and the HSE. The foreword to the Tower Crane Climbing Best Practice Guide has been written by Philip White, the HSE's Chief Inspector of Construction and the HSE have allowed their logo to be used on the cover. HSE inspectors will also refer to it as UK best practice when investigating tower crane climbing accidents, the CPA says.
The CPA TCIG Working Group looked at the issue of training for tower crane erectors and found that while erectors employed by the major tower crane suppliers have been trained and assessed as competent to the required standard, this is not always the case with sub-contract erectors who are sometimes used to augment erection teams.
Syd Appleyard, Operations Manager at Select Plant Hire, says, ”I’ve seen requests from some contractors asking for all the members of an erection team carrying out climbing to have had factory training, whether they are direct employees or sub-contractors. They realise that in climbing operations the competence of the erection team members is vital to the safety of the operation."
As well as the importance of a trained and competent erection team, the Working Group identified the importance of communication, particularly in the liaison between the tower crane supplier and the contractor on site.
Steele explains, “Before a climbing operation starts on site there is a lot of planning work required to ensure that all the potential hazards have been identified and measures put in place to reduce or eliminate them. This involves all parties working together to ensure that everyone is clear on their roles and responsibilities.“
One of the dangers of not having good communication between the tower crane supplier and the contractor on site is that issues can arise at the last minute, causing delays. For example, if equipment arrives late or is delayed because someone has dug a trench across an access road, the erection team may attempt to "rush" through the process without stopping to make the necessary checks, significantly increasing the risk of the process going wrong.
Ian Watson, Technical Safety Manager from major contractor Lend Lease, who was part of the Working Group says, “The one thing you don’t want to do with climbing is to rush. If everything goes smoothly and to plan there is less pressure on the people doing the climbing. On the other hand if parts turn up late, the climbing program gets behind and if the light’s going or the erectors need to be somewhere else, it puts immense pressure on the climbing team. That pressure can lead to people making mistakes, which may have disastrous consequences. To my mind one of the most important messages we have put in the document is where we say:
'It is essential that Principal Contractors allow sufficient time in the construction programme for the planning and execution of the climbing process. Any pressure for this potentially hazardous operation to be completed hastily will increase the risk of catastrophic failure.'“
Tim Watson, the CPA's Technical Consultant, who acted as Secretary to the Working Group and edited the document, emphasized the importance of balancing the tower crane during the climbing process.
To climb the crane, the top must be balanced about the climbing frame cylinder before it is jacked up to insert a new section. Balance is essential as the connection between the top of the crane and the top of the tower is through the climbing frame, which is not designed to take large out-of-balance forces.
The crane is balanced by lifting a tower section with the tower crane and moving it to the radius specified by the manufacturer. The erection team then carry out a trial lift of a few centimeters and check that the clearance between the climbing frame rollers and the tower legs is the same on all sides.
“It is vital that the erection supervisor can ensure the crane is in balance using the balancing information in the manufacturer's manual,” says Watson. “If you can’t get the crane in balance within a small tolerance, then you stop the operation and get in contact with your manager and ask for advice.”
“That’s another of the messages we’ve tried to get through. If the erection supervisor has any questions, go to someone in the management structure of the tower crane hire company or go back to the manufacturer,“ says Watson.
The CPA document seeks to build on existing standards and guidance with a Best Practice Guide that focuses on the management of the climbing processes. Watson was involved in the redrafting of the British Standard Code of Practice for the safe use of tower cranes, BS 7121 Part 5 in 2006, and says that “When you write a BS Code of Practice you have to follow strict rules covering the content and the language you can use, but when you write an industry best practice guide you can put in specific examples of forms and procedures, better illustrations and more detailed explanations.”
The upshot of these improvements is that this guide and DVD are already seeing great potential for use as an international climbing standard. Requests for the DVD have already come from all corners of the globe. “We’ve sent out 300 copies already, across the world, to America, New Zealand, China, Malaysia, India, Europe, South Africa, United States, Canada, and Ireland,” says Steele. “We’re hoping when the guide is launched and on our website it will be downloaded by all the people who already have the DVD.”
“BS 7121 Part 5 is a useful document but this guide, together with the DVD, sets out best practice for tower crane climbing worldwide, not just in this country,” says Appleyard.