Studying accident reports that cover lifting operations can be a sobering experience. While accidents during lifting procedures are probably no more frequent than in other areas of industrial activity, the human cost of mistakes soon becomes clear, not to mention the financial and legal implications.
Perhaps the most striking characteristic of such reports is how easily preventable most of these incidents are. Furthermore, although considerable attention is quite rightly paid to the condition of lifting equipment, it is fair to say that the most common cause of accidents is a lack of adequate planning and supervision. Straightforward equipment failure is relatively rare. Recent changes in legislation in many countries have reflected this, placing greater emphasis on correct training and preparation. The fact of the matter is, however, that a methodical, planned approach has always been the foundation of safe lifting. Furthermore, despite the ever-increasing range of equipment available to assist with lifting procedures, the basic principles that need to be applied are pretty much universal.
An appropriate starting point is an understanding of what actually represents a ‘good’ lifting operation. Quite simply, the objective of good lifting practice is to ensure that the load is safe and, when lifted, is as secure in the air as it was on the ground. Irrespective of the type of equipment being used, a number of critical issues should be addressed, beginning with an assessment of the load. This will include a determination of its weight (mass) and the position of its centre of gravity in relation to the lifting (pick-up) points. Other questions will include whether the load is in one piece. Will it fall apart when lifted? Is it fixed down or free standing? Does it have built-in lifting points? Is special equipment needed to lift it? Care should obviously be taken not to exceed the safe working load of the equipment involved, particularly in multi-point lifting operations. The use of sensing devices is strongly recommended if there is any degree of doubt.
The task to be performed should always be considered in advance. The route the load will take must be checked. Does the load need to be moved, turned over or re-orientated? Who will potentially be put at risk by the operation? Is the landing site itself clear and suitable for the load? Are there any other environmental conditions that need to be taken into account? Numerous factors will influence the choice of lifting equipment and sling (or other load lifting attachment). Not least of these should be the ability to position the lifting machine’s hook over the load’s centre of gravity. The appropriate method will ensure that the load is balanced, does not violently or unintentionally change in attitude when lifted, and remains stable at all stages of the lift. Whatever equipment is chosen, its fitness for the job must be verified. This will include evidence that it passed a thorough examination including any appropriate test, conducted by a competent person and is still within the valid period.
Obviously, unless absolutely unavoidable, loads should not be lifted above people. The area in question should be cleared and a system of communication must be agreed between personnel involved in the lifting operation. Unless exceptional circumstances demand otherwise, just one person should be responsible for giving instructions to the operator of the lifting machine.
The final stage of the planning process should always include a trial lift of the load in question. With the load lifted to a nominal height, balance, stability and security can be assessed prior to the lifting operation proper.
This may all seem obvious, but referring back to real-life incidents serves to highlight how easily they can be overlooked. An accident currently under investigation in the UK by the Health & Safety Executive highlights many of the dangers inherent in a lack of planning. A heavy load being hoisted on a construction site slipped from its sling and fell on a worker below, causing a very serious injury. The lifting operation was characterised by a number of planning failures; had any one of them been addressed before the lift took place, at the very least the personal injury would have been avoided. The most obvious would have been to ensure that the lift was not performed above a person. Furthermore, the operation was not authorised by the main contractor responsible for the site before it took place, which it should have been. Finally, the load was badly slung, with inappropriate equipment modified by staff on site in an attempt to accommodate the load in question.
In this case, the entire operation was characterised by a lack of planning. Even where planning has been undertaken, it is essential to monitor the work to ensure that it follows the plan. Ill-conceived changes are often the cause of accidents. An example of this was a job involving the erection of a series of concrete arch sections to span a waterway under a new motorway. The arch sections were of reinforced concrete in the shape of an inverted J and weighed 22t. Each had to be lifted, orientated to the vertical and positioned. When erected, they interlocked to form a tunnel. As each had to butt up to the adjacent section, the plan was to cast them with two holes positioned along the centreline, through which anchor points would pass, so that the section could be lifted by two slings and a lifting beam. This arrangement allowed the arch section to be orientated to the vertical and rocked slightly to align it with the mating sections.
The plan was changed when the arches were delivered to site and found to be without the essential holes. Attempts were made to drill them but failed when the reinforcing bars were hit. Next the contractor attempted to lift them with standard slings wrapped around the section, relying on friction to grip. However each section had to butt up to its neighbour and the sling prevented that. As a last resort they allowed a small gap and used a pair of roundslings – the slimmest slings with the capacity required. A supply of slings was obtained and a trial lift of a section was made using a pair of slings in choke hitch together with the lifting beam from the original equipment. The test apparently worked but the following day, with one section suspended in place from a crane, a sling on its mating section, which was being manoeuvred by another crane, failed and the section fell into the waterway. Fortunately in this case no one was injured, but the job was brought to a halt at considerable expense.
What went wrong? Apart from the most obvious – the omission of the lifting point holes – the sections weighed 25t, three tonnes more than expected. This overloaded the slings. To get sufficient grip, the choke of the slings was tightened down beyond the natural 120° angle, again causing local overload. The ultimate cause however was the orientation of the lifting beam. Because both slings were the same length, as the arch rotated to the vertical, the beam also tipped back and the uppermost sling engaged on the edge of a steel plate that formed part of the beam. It cut straight through the sling.
Even if this had not occurred the new plan was fraught with problems. The positioning of the slings was critical to ensure the load was correctly orientated. The pre-positioned holes would have ensured this but, without them, the slinger had to judge each time. Inevitably, as the sections were rotated to orientate them to the vertical, there would be some movement of the choke, risking damage to the slings. Moreover, as they had to butt up as close as possible to the adjacent section, the risk of trapping the slings was very high.
These are just two examples of failures in planning. This article simply aims to highlight the dangers and by no means provides a comprehensive list of the issues that need to be addressed. Relevant codes of practice and legislation must be referred to for a complete summary of the questions that should be considered. On paper, nearly all will seem no more than straightforward common sense.
Taken seriously and consistently applied, however, good planning and preparation procedures will go a long way to ensuring that the risk of accidents is dramatically reduced.
