Buyer’s guide to lifting accessories16 December 2009
In the first of a new series of articles, Derrick Bailes, technical consultant, Lifting Equipment Engineers Association, advises those buying and using lifting accessories.
They were really intended as an introduction for people new to the lifting industry although I found they had been read with interest by a wide range of people. From time to time I get reminded that there are always people using lifting equipment for the first time and also that, as new equipment comes onto the market, there are some ‘old hands’ who need updating. This is the first in a new series of articles which revisit and update the subject.
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 to provide an overview of the range of equipment available.
I have used the term ‘lifting accessories’ because that is the term used in modern legislation. 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 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 persons 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 harmonised 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, harmonised 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.
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.
I hope that the above has set the scene by giving an overview of the responsibilities of those who select, specify and purchase lifting accessories, the information required about the application to start the process and an outline of the equipment available. In subsequent articles I shall expand on the process and fill in more of the detail.
About the author
Derrick Bailes is technical consultant (formerly chief executive) for the Lifting Equipment Engineers Association, 3 Osprey Court, Kingfisher Way, Hinchingbrooke Business Park, Huntingdon, PE29 6FN, Tel: +44 (0)1480 432 801, Fax: +44 (0)1480 436 314, Email: [email protected]