Essentially there are four key factors which affect the safety of slings and lifting accessories: the suitability of the equipment, the quality of the equipment, the condition of the equipment, and the way it is used. When equipment fails it is usually a combination of factors which are the cause. The important safety message is therefore to pay adequate attention to each of these four key factors. Doing so automatically stacks the odds in your favour and, at the very least, provides a second chance to get it right.
We start with the suitability of the equipment. Whilst it is true that a good slinger can rig most loads using a selection of standard slings, this takes considerable skill and is certainly not always the most efficient or safe method. Moreover, for a repetitive series of lifts it often takes longer to position the sling and get it just right every time. There is now a wide range of special purpose equipment available for purchase or hire, including equipment to lift loads previously handled manually. Last minute lash-ups, made under pressure of time and money, are a common cause of accidents.
Quality of equipment is a hot topic at present, with much variation evident in the products reaching the market. By quality I mean the fundamental quality, as designed and manufactured, rather than the state of repair. Regrettably, the buyer’s specification for lifting tackle is all too often minimal and the key deciding factor in the purchase or hire of equipment is the price. For example, suppliers get asked for a two leg chain sling, SWL 7.5 tonnes, two metres long. There is no reference to a standard or any other technical requirements. Needless to say, you get what you pay for. Good quality equipment made to a recognised standard is more tolerant of accidental misuse, climate extremes and other external influences, and offers much better durability.
Slings and other lifting accessories can have a hard life and are vulnerable to damage each time they are used. If loaded wrongly they can fail, or be damaged lifting a load that is well within their safe working load. Most countries have some regulatory requirements for the formal inspection of lifting equipment but usually it is of the order of every six months. Considering the type of damage which can so easily occur, this is far too long. Frequent in-service inspection is vital. A trained slinger should be able to quickly look over the equipment every time it is used. Equipment which is not fit for service should be separated and securely quarantined to prevent accidental use.
Here I want to make an important point about the culture of the user organisation. No one likes to be blamed for making a mistake, so it is vital that, when it comes to accidentally damaged lifting equipment, there is a ‘no blame’ culture. This is not to encourage carelessness, but to ensure that damaged equipment is not kept in use or left available for others. It also means having some spare equipment available, particularly for those operations that are most vulnerable. In the broader context of other costs, this is unlikely to prove expensive.
As well as protection against accidental damage, most equipment requires some form of maintenance to keep it working safely. Even a simple sling might need cleaning and drying. Left to their own devices, operators don’t always think through the consequences of their actions and use inappropriate methods such as drying wet textile slings by heat. The result might look OK, but has the heat damaged the material or concentrated the contaminants that may reside within it?
During use, there are three main causes of failure of slings and lifting accessories. These are: errors in the geometry of the rigging arrangement; cuts from sharp edges, and failures from excessively high dynamic loads, ie shock loading.
It is essential that the slinger has an adequate knowledge of these causes and knows how to avoid or compensate for them. However, we still see bundles of materials such as reinforcing bar being lifted in simple choke hitch which the slinger tightens by battering it down with a piece of wood or scaffold pole. The result is a local overload. With a sufficiently long sling leg, a full wrap and choke hitch would hold the bundle much more securely. The photograph which inspired this article is typical of many of the applications we see: slings at such an angle as to risk overloading the sling or cause it to slip from the hook. Loading the hook in a manner which will cause it to open out is also an all too common sight.
All these lessons have been learnt many times in the past. Good training at the outset for all concerned – the specifier, the buyer, the planner, the inspector and the slinger – followed by regular assessment and refresher courses remains the best means of ensuring that basic mistakes are not repeated time and time again.
