Crane safety experts, operators, owners, engineers, manufacturers and representatives from insurance companies and regulatory bodies from all over the world descended on the Thistle Tower Hotel in London on 16 and 17 June, under the shadow of the famous Tower Bridge.
They came from North America, Australia, Africa, the Middle East, all over Europe, and even the Philippines to make it a truly international event, designed to share knowledge and experience, and discuss how the crane industry can reduce its terrible accident rate.
Mobile Crane Safety
Day one focused on mobile cranes, and first up was Tom Broderick, executive director of the US Construction Safety Council. Broderick explained that while crane drivers are sometimes at fault, the underlying problems usually relate to the management system. People cause accidents, not equipment, he said. He addressed the subject of overhead power lines. Electrocution is a major killer in the US crane industry, and yet it is so preventable. Crane users can protect themselves from power lines by using proximity sensors, by having the electricity cut in part of the power grid; by having the power company shield a line; or by specifically employing a watcher to look out for power cables.
Broderick also showed dramatic footage of the Big Blue collapse at the Miller Stadium in Milwaukee in July 1999.
Peter Oram, chairman of BS 7121 and CEN TC 147, and the UK’s pre-eminent authority on crane safety standards, began with a little history lesson. In 1857 Isambard Kingdom Brunel lifted a 1,000t bridge section successfully without a single injury. He delegated the responsibility of the lift to one person. In 1998 the concept of the responsible person was built it into the UK’s Lifting Operations & Lifting Equipment Regulations (LOLER). Brunel also determined the centre of gravity of the load and created an entire signalling system for communications during lifting. Oram then went on to give details of some of the more significant accidents in the UK, including the 1964 Brent Cross accident, in which a mobile crane fell onto a bus, killing seven and injuring 32 passengers. Oram also told the audience about the new version of part 2 of BS 7121 Code of practice for the safe use of cranes, which was recently published.
Professor Wojciech Sobczykiewicz is managing director of the Institute of Handling and Engineering Machines at Warsaw University of Technology in Poland. He presented an analysis of accidents involving the 9,800 mobile cranes in Poland. Technical experts suggest that risks above one in 10,000 (10-5) need to be reduced. In comparison, Polish data from 1993-1999 suggests the probability of a serious accident is 1 in 102 (0.0102). The top three most common accidents were loss of crane stability, exceeding the material strength and electrical shock. The top three most deadly were electrical shock, loss of stability and exceeding material strength.
Graham Brent, executive director of the USA’s National Commission for the Certification of Crane Operators gave an overview of the mish-mash of operator requirements in the USA. The federal structure of the USA allows different states to have different requirements and only 11 states and six cities including New York City and Los Angeles require a crane operator licence.
A further seven states have a requirement pending. The National Commission for the Certification of Crane Operators was formed in 1995 to develop performance standards for crane operators. The NCCCO has qualified 20,000 operators to date. In the US, crane operators’ rights have fallen slightly; in a 1968 standard they had the absolute right to refuse to make a lift if they considered the conditions unsafe; in the current draft they do not. Many big contractors are now writing in the requirement that crane operators be licensed.
Klaus Meissner, research and development director for Terex Demag, was one of two representatives from mobile crane manufacturers that spoke. The other was Holger Streitz, Liebherr Nenzing’s crawler crane design manager.
Meissner discussed computer control systems, explaining that they could only ever be an aid to drivers, and not a replacement for a driver. Drivers’ reactions in critical situations cannot be replicated. In developing computer systems, drivers’ wishes must have the highest priority. According to EN 954-1, motions should only be activated by the intention of the driver in the operating position which is why levers return to zero. Dead man switches are built into crane cabins, but many drivers override them. Terex Demag has a new computer control system that helps create a smooth application of forces.
Streitz explained all the different standards and regulations that crane manufactures must meet, both in Europe and North America. Standards are used differently in different places. For example, in Europe, de-rating a crane is part of the standard; in the US, de-rating a crane is up to the operator. He also explained the different standards for lift cranes and duty cycle cranes, and why different manufacturing technology was needed for different applications. Do not expect your lift crane to last very long if you use it for duty cycle work, seemed to be the message.
Next up to speak were crane experts from oil companies on either side of the world. From Syncrude in Canada was Andy Ciupa who explained how it had been five years since Syncrude had last had any crane-related injury requiring medical aid, from either its own fleet, or the hundreds of cranes that it had brought in from lifting contractors during that time. Some in the audience thought Syncrude’s processes of risk assessment and control were overly bureaucratic for a regular taxi crane firm to implement cost-effectively, but the results speak for themselves. Syncrude leant heavily on the Exxon Crane Guide in developing its safety programme.
From Saudi Arabian oil company Saudi Aramco, critical lift engineer Hosam Hashem explained Aramco’s impressive commitment to training and development. Employees attend basic maths, science and English language classes during their first two years. If they are successful, they can attend the basic crane operator or rigger course. Then they are assigned a qualified mentor and, once ready, they are set an examination. There are two levels of crane operator basic and advanced, and three levels of rigger. Lift plans are devised by the highest grade of rigger or a critical lift engineer. Other educational facilities, such as a computer room and on-line courses, are also made available to employees.
Repairing telescopic booms after an accident remains a controversial subject. Manufacturers would prefer crane owners referred all damaged booms back to them, but many crane owners know that there are several capable independent boom repair specialists. One of these is Köhler Kran-Service of Germany. Managing director Andreas Köhler explained what is and is not possible and gave some useful advice. In the event of an accident the recovery should be treated as a critical lift to prevent further damage. Do not cut up a damaged crane boom it just adds to the expense of repair. There are three ways to repair a boom: straightening, partial replacement or complete replacement. The less work required, the lower the cost. As an example, repairing one bent boom by straightening cost E14,000 and took two weeks.
Marc Ostertag, international product manager of PAT America gave an overview of working area limiters that warn the operator if the load is approaching an obstacle. If two reference points are inputted, a virtual wall between those two points is created, which the boom cannot cross. Ostertag also introduced the audience to a new load motion alert that is attached near the hook. It is designed to keep riggers safe by providing an audible indicator of the location of a moving crane hook.
Kevin Cunningham, president and CEO of US firm Special Risk Services, gave sound advice on insurance. The state of the reinsurance market means increased risk taking for primary insurers, which means less interest in insuring higher-hazard industries, such as cranes. To protect your company, Cunningham advised establishing a relationship with the most financially sound insurance partners, and making sure that you know who from that company will appear on the scene of an accident. Increase your risk participation by paying an excess in the event of an accident. Re-evaluate your company’s risk management process and safety programme methods. How current is your equipment rental agreement? Who is responsible to act when claims occur? Can other parties participate in claims scenarios? Do you have progressive legal insurance? Are your employees / supervisors accountable? Implement a continuous improvement process. Conventional methods do not suit the crane industry, so you have to take an unconventional approach, he said.
The context for Cunningham’s presentation was given beforehand by Andrew McMellin of Lloyds insurance underwriter SJ Catlin. McMellin gave some mind-boggling numbers faced by the insurance industry. The 11 September terrorist attacks on the USA in 2001 cost the market about $40.6bn. But this pales beside the cost of the whole asbestos crisis current estimates put it at $122bn. Since the 1970s, claims payments have exceeded premium income. Investment income has provided a profit, but now that investment income is falling, insurers are having to underwrite for a profit.
Final speaker on day one was Hugh Pratt, president of Insulatus, which makes a load insulating link. Pratt explained that when a crane boom touches a live power line, the operator is usually safe, if he stays in the cab, because he is insulated from the ground. It is usually the rigger that dies. There are two methods of protection against load electrocution proximity warning devices and insulating links. Pratt argued that an active protection method was superior to a warning system. It is better to have your life saved than to be told that you are in danger, he believed.
Tower Crane Safety Day two concentrated on tower cranes. First speaker, Felix Weinstein of israel-based engineering consultancy Felix-Engineering, immediately grabbed attention with a photo of a tower crane in mid air, falling from the Taipei 101 skyscraper after being dislodged by an earthquake. Weinstein presented a catalogue of tower crane accidents that he had investigated in Israel over the years. As operators in Israel must undergo 700 hours of practical and theoretical training, Weinstein challenged the prevailing wisdom that people, not machines, were the biggest risk. In Israel many of the cranes are old and accidents have been caused by cracks in connecting pins, fatigue and internal corrosion. Among other causes were faulty foundations and high winds (see CT Feb03, pp20-23). Many loads with large surface areas should not be lifted in winds anywhere close to the 72km/h standard maximum in-service wind speed, but the engineering calculations needed to determine safe wind speed for each particular type/shape of load was too complex for most crane operators, he said.
Next up was another consulting engineer, Gordon Stewart of Stewart & Associates, Australia. Stewart presented a history of the development of crane standards in Australia, right up to the current AS 1418. New versions of the tower crane manufacturing and safe use standards, AS 1418.4 and AS 2550.4, are issued this year.
John Winson, inspection & test services manager of UK hire company Select Tower Cranes, explained how his company had set up its own centralised lifting tackle operation to support its 300-odd tower cranes. A certification database holds paperwork for each bit of tackle, and each item is colour-coded. All tackle 7,500 pieces of kit is inspected twice a year, once in March and once in September, and the colour band on each item is changed after inspection. Everyone at Select knows, therefore, that until September 2003 they must use only green-coded lifting tackle. A cycle of four colours is used.
Alain Voyatzis, director of SMIE of France, addressed the subject of anti-collision devices, made mandatory in France in 1987. Anti-collision systems are not simple because of the inertial behaviour of tower cranes. To stop the slew of a heavily loaded jib might need as much as 90°. If you have a second heavily loaded crane moving in the opposite direction, the slow-down action has to start at 180°, that is while each of the drivers is practically unable to see the impending danger. Short-term remote obstacle identification by remote sensing technology such as radar is inadequate, Voyatzis said. Work area limiters on their own may exclude too much of a building site to be practicable. SMIE’s method is analytical deterministic real-time dynamic risk evaluation, and if necessary, crane movement inhibition. Voyatzis compared the system to other driver supports like antilock braking systems (ABS) on cars. If the system is activated, the driver is already in trouble. The system reduces risks of collisions, and even if it fails, it does not add any new risks, save possibly a driver’s increased reliance on the system. Anti-collision systems create a reduction of risk, and that is worth something. System down time on a large installation is in the region of 1%. The real problem is explaining to site managers how such systems work.
The afternoon of day two was given over to manufacturers of tower cranes.
Bosko Mujica, manager of Jaso’s structural and welding department discussed foundations and structural safety. Different lifting jobs require different types of cranes, he explained. The more frequently the crane is used, and the greater the loads the crane lifts, the stronger the structure needs to be. Loads that should be considered are the dead weight, the working load (including dynamic forces due to acceleration), loads due to horizontal motions and loads due to the wind. Stable foundations require correct calculations, suitable ground bearing capacity, well-levelled base and tracks, and appropriate electrical ground connection. Jaso uses, among other techniques, finite element analysis to design crane components. The software breaks an object into many small parts, and calculates the interaction of those parts on each other.
Emanuele Greppi, the chief designer at Carlo Raimondi, gave an overview of the safe installation of tower cranes. He said that the first problem to consider when choosing a tower crane is the interference between the slewing jibs and other obstacles. The supporting ground must be strong enough to withstand the crane’s loads. Bottom slewing saddle-jib self-erectors are most suitable for small buildings where installation space is not too limited. This crane is also suitable where the jobsite is large, with low buildings, and requires frequent crane movements. These cranes are still quite complicated in erection procedure; they require a trained operator to do the job. Top-slewing saddle-jib tower cranes are more suitable for heights under hook of more than 30m. The city type of top-slewing tower crane ranges from 35tm up to 200tm and relies on a mobile crane for erection and dismantling. It is always advisable that the crane operator sits in the cabin because he can better sense the crane behaviour than when away from the crane using a remote control. Installation of ties linking tower cranes to a building may involve serious risks even if carried out by experienced personnel. Tower cranes today can be composed with different-sized towers and jibs. Cranes working on bridge piles, for example, need a small jib and large mast.
Potain engineering director Guy Galand addressed maintenance and revealed that the European Federation of Materials Handling & Storage (FEM) will this year publish a document on maintaining tower cranes in a safe condition (FEM 1.007). This standard contains nothing new but rather clarifies European standards on the subject. It sets out a programme of inspections, which are the best means of maintaining cranes safely. Before use, operators should inspect the function of mechanisms, brakes, safety devices and try to observe defects. At least twice a year a technician should inspect lubricants, electrical and hydraulic equipment, connections, brakes and supports. Once a year, or upon re-erection, a technician should look over and test the entire crane, including the structure, installation of components, and documentation. When the crane is 4, 8, 10, 12 and 14 years old, and each year afterward, an expert should carry out a very detailed inspection with tests and dismantling.
Day two ended with a wide ranging panel discussion on other aspects of tower crane safety of concern to the audience, giving them an opportunity to quiz the manufacturers.
Crane Safety 2003 concluded on Wednesday morning, for those delegates able to stay on, with a site visit to see the construction of Heathrow Terminal Five. There are 1,500 workers on this 250ha site currently, which will rise to 6,000 at fit-out stage. A total of 34 Terex tower cranes (there were 18 erected at time of visit) are helping to place a million cubic metres of concrete, 190,000t of reinforcement steel and 50,000m2 of curtain walling. The site visit was hosted by Select Tower Cranes and parent company Laing O’Rourke, the main contractor on site.
