Chain sling inspection

It should go without saying that lifting equipment must be kept safe to operate at all times. However, anyone involved in the test, maintenance or inspection of lifting equipment is likely to have seen examples of neglected and abused lifting equipment still in regular use. At best this is an unnecessary drain on resources leading to costly repairs or prematurely ending the life of the equipment. At worst it poses a direct threat to health and safety.

Although a degree of harmony is being achieved within the EC, there are still differences in the legislation on lifting equipment and lifting operations in the member states. This is equally true of countries across the world. Whatever the prevailing regulations, a rigorous inspection regime is essential to ensure that health and safety conditions are maintained and that any deterioration in equipment can be detected and remedied in good time. Furthermore, to be effective, such regimes require a combination of levels and frequency of inspection appropriate to the equipment and the conditions in which it is used and stored.

In the UK, the highest level of inspection is called a ‘thorough examination’ – the requirements for which are spelt out in LOLER (Lifting Operations and Lifting Equipment Regulations 1998) and accompanying code of practice. However, whatever regulations are applicable, such high level inspection does not obviate the need for more frequent, but less extensive in-service inspections. These generally involve a visual check supplemented, if appropriate, by simple operational tests.

In-service inspections should be done by a responsible person with sufficient knowledge and training to enable them to recognise obvious defects. This person may be distinct from the slinger or operator of the lifting machine but in practice it contributes significantly to safety if the slinger or operator is properly trained to inspect the equipment he or she uses. In broad terms, an effective in-service inspection will identify the signs of damage, wear or other deterioration that might affect a piece of equipment’s fitness for use. It can also have the benefit of identifying bad practice in the use of the equipment as will be seen below.

Unlike a lifting machine such as an electric overhead travelling crane, where relatively little can go wrong in the short term unless it is overloaded or deliberately misused, a sling is exposed to the possibility of damage every time it is used. Even when used well within its safe working load, there are a lot more opportunities for an error which might leave the sling less safe or even dangerous the next time it is used. This is because the sling may connect to the load by wrapping around or passing through it, and may be used at an angle or in choke.

Therefore slings should always be checked every time before use. This does not have to be a bureaucratic or time-consuming nightmare. An experienced slinger should be able to cast their eye over a sling in seconds, and there is no need for records of such inspections to be kept. However, if a defect if found, there should be a procedure to withdraw the sling from service immediately, thereby avoiding the risk of anyone else using it.

Inspection checklist

Before starting the inspection ensure that the sling is in a reasonably clean condition and there is adequate lighting. Be methodical and try to follow a regular routine so that it becomes automatic. It is a good idea always to work from the top down.

Look at:

(1) The shape of the master link. Because this link has large internal dimensions to accommodate a crane hook, it tends to be the first component of a sling to collapse and elongate if the sling has been overloaded. Check also for twisting and distortion in other directions.

(2) The integrity of the components coupling the chain to the master link. Most modern chain slings are mechanically assembled using coupling components. There are two basic designs. One is a U-shaped forging with a clevis and pin at the open end, the pin going through the first chain link. The other design comprises two forged half links with a pin to connect them. Both designs depend upon having the correct pin and pin retainer in good condition and properly fitted. Corrosion can render the pin retainer ineffective. With the half link design, the two halves should articulate about the pin but corrosion can cause them to seize. If they were allowed to seize when flexed and then straightened under load, the pin or the forgings can fail. Check for any seizure, damage or substituted components.

(3) The condition of the chain. Modern chain wears well so the most likely defects arise from misuse. Normal wear occurs at the interlink seats but slings which have been dragged along the ground can have significant wear on the outsides of the links. When overloaded, the chain elongates, resulting in a lack of articulation between the links and, in extreme cases, the chain becomes rigid. Check that it flexes freely. On a multi-leg sling, compare leg lengths. Local stretch in a section of leg can occur if the sling has been abused by the so-called practice of battening down a choke hitch. Look for bent or notched links which can arise from such abuse or from loading over corners without adequate packing. Check also for permanent twist which can occur if the leg was loaded when twisted.

(4) The chain shorting device or chain clutch. One of the advantages of chain slings is the ease with which the leg length can be adjusted if the leg is fitted with a chain clutch. However, misuse can damage both clutch and chain. Some designs prevent the chain being inserted incorrectly but others do not. Incorrect use can distort the forging and cause localised damage to the chain. Irrespective of the design, back hooking into the chain loop above the clutch is a thoroughly bad practice, but nevertheless sometimes seen. It can cause damage. Check also the integrity of the connection between the clutch and the top link. It will be similar to that connecting the chain.

(5) The lower terminal fittings. These are usually some form of hook but can also be links. Hooks can be distorted at well below their safe working load if they are loaded on the tip instead of in the bowl. Reject any which show signs of twist or opening out. For hooks with a safety catch, an obvious indication of damage is the catch not fitting. Check also that the catch itself is not damaged or ineffective. Self locking hooks rely on a latch mechanism which can be affected by deposits such as cement. On some designs, wear of the latch will allow the hook to unlock if it is tapped sharply on the back. Hooks are connected to the chain by either a clevis and pin or a coupling component similar to that which connects the chain to the top link. Check that the correct pin is properly fitted and retained, is in good condition and that the coupling articulates.

The above covers the main mechanical defects which may be found, but the inspector should keep an eye out for damage arising from excessive heat or exposure to chemicals, particularly acids which can cause embrittlement. Last but not least, check that the sling identification and safe working load markings are present and legible. These are usually on a tag fixed to the top link or stamped directly into the top link. If any of the above defects are found, withdraw the sling from service.