In this article I aim to convey the responsibilities of those who select, specify and purchase lifting accessories, the information required about the load in order to select the most appropriate equipment and the range of equipment available.

I have used the term ‘lifting accessories’ because that is the term used in modern legislation in many regimes. However older terms such as lifting gear, lifting tackle and below hook equipment are still widely used. Effectively we are talking about what connects the load to the lifting machine. It is safety critical equipment and, as I have often stated, is relatively vulnerable compared to the lifting machine.

A lifting machine in serviceable condition, once correctly installed or erected, is in a very controlled situation. All mobile cranes have load indicator and limiting devices. Since the European Machinery Directive came into force over a decade ago, every other type of crane and hoist sold in the EU with a working load of one tonne or more (and many of lower capacity) has some sort of load limiter. Unless deliberately overridden, such devices will limit accidental overload to a few percent.

By comparison, lifting accessories, even when lifting a load of less than their working load, can be overloaded. This is due to the way in which they are applied and in extreme cases it can lead to failure and a dropped load. To ensure adequate levels of safety it is therefore essential that those who select or specify lifting accessories are knowledgeable about what is available and the attributes of each.

The range of equipment now available is very much wider than a generation ago and there is no need to rely on just a few basic slings. For many types of load there are purpose designed lifting accessories which eliminate a lot of the difficulties of connecting to or gripping the load in the manner required. Some of these items are relatively expensive and purchasing them can perhaps only be justified for regular use. However many are available from the hire industry at a cost which can be justified for a single use.

There is also the issue of equipment quality. To the uninitiated it can be very difficult to distinguish between similar items and, with an eye on the budget, cost can all too easily be the deciding factor. However, in Europe at least, employers do have a legal duty to ensure that any lifting equipment they provide for their employees complies with the essential health and safety requirements of the Machinery Directive. The same duty applies to the self employed.

Buyers need to be aware of this duty. It is not sufficient to specify, for example, a sling by just the safe working load and the length. You need to be sure that the working coefficient, for example, the factor safety, is adequate, that the fatigue life is adequate, that the material it is made from has adequate low temperature toughness and that it has all the other attributes which contribute to it being of an adequate safety standard.

The easiest way of doing this is to specify that the item is made to the relevant harmonised European Standard. These standards have a special status. If a product is made to a harmonized standard, it is deemed to comply with the legal requirements in so far as they are dealt with by the scope of the standard. To achieve that status, the standard is vetted by a technical consultant on behalf of the European Commission and its approval is published in the Official Journal.

Manufacturers must show compliance with the legal requirements by affixing the CE mark and issuing an EC Declaration of Conformity for their product. The declaration should include details of any standard the item complies with. Therefore, for buyers, harmonized standards provide the easiest way of specifying equipment which complies with the legal requirements. Obtaining the Declaration of Conformity is the easiest way of getting the necessary evidence that it does.

The load
Having dealt with how to specify the lifting accessory, we need some information about the load. In particular:
• What does it weigh?
• Where is the centre of gravity?
• Are there lifting points?
• If there are no lifting points, how can the lifting accessory be attached?
• Is the load in one piece or likely to fall apart?
• Is the load strong enough to support itself or does it need support to be lifted?
• Are there any special problems with the load, for example, delicate, hot, cold, corrosive or sharp edges?
• Are there any special environmental problems, for example, very hot, cold or wet, the presence of fumes, solvents, acids or other chemicals?
• Does the load have to be turned or orientated before landing?

Knowing what the load weighs with reasonable accuracy is essential so do not guess. If the information is not available from drawings and it can’t be weighed, there are tables and formulae available to help you estimate within a reasonable accuracy. If in doubt it is safer to over estimate.

Knowing the position of the centre of gravity along the length and width of the load is necessary to achieve a balanced and level lift but the height is also needed to ensure load stability.

If there are suitable lifting points then a sling is usually the best option, perhaps in conjunction with shackles, eyebolts or swivel links at the connection point.

If there are no lifting points then consider whether a sling can be wrapped around or passed through a load. Whenever a sling connects to a load in this way, the choice of sling must be such that the sling will not damage the load and the load will not damage the sling. Often packing material is required between the sling and the load.

Other connection options are various designs of clamps, grabs, special shaped hooks and equipment such as crane forks for handling palletised loads. Also available for a surprisingly wide range of applications are vacuum handlers and lifting magnets which attach to the load by adhesion.

The strength of the load is a vital factor in the choice of lifting accessory. Multi-leg slings with the legs used at an angle exert an inward force. If the load cannot withstand that force a lifting beam or spreader is required to counter it. A lifting beam can also provide a long flexible load with support at several points. This may be necessary to prevent damage to the load but the arrangement can also be used to prevent the load ‘peeling’ off from vacuum heads or lifting magnets.

These various lifting accessories are frequently used in combination. For example a sling and a plate clamp, or slings and a spreader beam.

For some loads, special purpose designed lifting accessories are needed. For example a piece of machinery without suitable lifting points may require a bolt on attachment to provide temporary lifting points.

If the load or the environment present any special problems, it can limit the options. The materials used for lifting accessories can be adversely affected by exposure to heat, cold, wet, sea water, solvents, acids and other chemicals. However the materials have various degrees of resistance and with careful selection, some can be used with such loads and environments.

Many lifting operations, such as those in machinery manufacture and maintenance, require the load to be turned over or manipulated in some way to achieve the required orientation. For repetitive use the best option will probably be a purpose designed accessory but, with skill, such jobs can often be done using off-the-shelf equipment. Manually operated lifting machines such as lever hoists and hand chain blocks can be used in conjunction with lifting accessories to provide the means by which the load can be turned and manipulated.

Sling types
Sling types fall into three broad categories: chain, wire rope and textile. Textile slings include those made from webbing, fibre rope and endless roundslings. Within each category are a number of variants.

There are five basic configurations of sling: single-leg, two-leg, three-leg, four-leg and endless. The availability of each configuration depends upon the type of sling and will be explained in more detail later. Depending on the sling type, there is a variety of terminal fittings to choose from. As well as those for general applications, there are fittings which enable a sling to be tailored to specific loads. They include pipe hooks, bale hooks, foundry hooks, can hooks and case/carton grabs. Where appropriate, the use of such purpose-designed fittings is highly recommended.

Each type of sling has its own characteristics and the best choice of type and configuration will depend very much on the nature of the load.

Chain is a very durable and versatile option. It is flexible, and therefore able to wrap around the load. Packing is often required between the sling and the load to prevent chain links being bent over a corner of the load or the chain damaging the surface finish of the load. A shortening clutch or hook allows the leg length to be easily adjusted to the nearest link. Depending upon the grade, chain slings tolerate a wide range of operating temperature. The grade of chain is determined by the mean stress in the chain at the minimum breaking load. The higher the grade, the smaller and therefore lighter the chain for a given working load.

Currently the most popular is grade 8 to EN 818-4 which is manufactured from alloy steel. It is relatively difficult and expensive to assemble slings of this grade by welding so the vast majority are mechanically assembled using coupling components or fittings with a clevis and pin.

Sling systems comprise chain and a variety of components in a range of sizes. From these, slings are assembled to specific customer requirements, usually by authorised distributers. Several manufacturers offer grade 10 chain and components which have some advantages, particularly a further saving in weight.

Although not widely used now, grade 4 slings to EN 818-5 are still available. These can be easily assembled by welding and are more suitable for some applications, particularly those involving high temperature or an acidic environment. Chain slings made from alloy steel, for example, grade 8 and above, are not suitable for use in acidic environments as this can cause hydrogen embrittlement.

Both grade 4 and 8 can be used in the temperature range from -40°C to 200°C without any reduction in working load. With a reduced working load, grade 4 can be used up to 475°C and grade 8 can be used up to 400°C.

The upper terminal of single and multi-leg chain slings is usually an oval link big enough to fit onto a crane hook of similar working load. For general purpose applications the lower terminal fittings are usually a hook with a safety latch. Also available are self-locking hooks which are opened by releasing a latch but close automatically under tension. Another option are C hooks. These do not have a safety latch but have a turned in tip which reduces the likelihood of detachment when not under load. They also have a beak or projection at the top of the hook which, in combination with the turned in tip, prevents the hook from snagging when being pulled under or through a load. These features and their general robustness make them popular in many applications, particularly on construction sites.

Most sling system manufacturers also offer terminal fittings for particular applications. Pipe hooks engage over the end of a pipe or hollow box. Foundry hooks are shaped to fit sand box trunnions. Bale hooks are pointed so as to dig into a bale. Can hooks are shaped to engage with the lip of a drum lying on its side.

Wire rope
Wire rope offers an economical alternative to chain for many applications and also has advantages of its own. It is easier to feed under a load as it can often be pushed through. Slings made from galvanised rope and thimbles are more tolerant of marine or similar environments.

Wire rope slings can tolerate temperatures down to -40°C without de-rating but performance may be affected depending on the effectiveness of the lubricant. The upper temperature limit varies according to several factors including the material the ferrule is made from. Generally advice should always be sought for applications above 100°C and the upper limit is 200°C.

Wire rope slings are at their most advantageous when the legs are in a straight pull such as when suspending a spreader beam. If wrapped around a load, they inevitably become permanently set to the shape of the load unless a large radius can be maintained. Packing may be required to provide an adequate radius and to protect the surface of the load from the wire rope.

The length of a wire rope sling cannot be adjusted by the user. However, a two-leg arrangement, utilising a continuous length of wire rope and a special top fitting, does allow one leg to be shortened as the other is lengthened. This is very useful if adjustment is required to match the centre of gravity of the load.

The harmonised European Standard for wire rope slings is EN 13414-1. To make a sling, the wire rope is terminated with an eye. At one time these were always hand spliced, a relatively slow process which also produces a long tapered termination. Now virtually all eyes are ferrule secured. The ferrule is squeezed onto the rope by shaped dies in a hydraulic press causing it to grip the rope very firmly.

The simplest eye is a turned back loop secured by the ferrule. A Flemish eye, where the rope strands are undone then re-laid to form the eye with half the strands going round the eye in one direction and half in the other and the tails secured within the ferrule, is more efficient but also more complex to make.

Many wire rope slings are single-leg with a large soft eye at each end. One or more, possibly of different lengths and working loads, can be used in combination with shackles to make a temporary assembly for a particular job. Permanently assembled multi-leg wire rope slings usually have an upper terminal link and hooks or other lower terminal fittings similar to a chain sling. When assembled with links and fittings, the wire rope will be terminated with a small hard eye. The hard eye includes a thimble, which prevents wear on the rope and maintains the shape of the eye to ensure that the terminal fittings can articulate properly.