Slinging is the term used for lifting loads with the use of a sling, a slinger is the term used for the person who carries out the slinging. Slinging is an operation which is frequently carried out on a daily basis in many industries, often using chain slings or web slings, but it can also be a practice which is used only every now and again, whichever applies does not matter, safe slinging practices are fundamental for the safety of the lift, the item being lifted, the surrounding environment and personnel and the slinger him/herself.
It can take time for a novice slinger to become proficient at slinging, because good slinging practices cannot be learned from a manual, only the basic knowledge ofthe do’s & don’ts; good safe slinging practice is learned through experience, this is because no two lifts are usually the same, and the balancing of the load is crucial to the lifts safety, this is sometimes difficult to determine, where to place the slings to get an even balance, this is often therefore estimated, but a far out estimate could result in serious injury or damage, a competent slinger with lots of experience will rarely guess wrong, and usually be fairly accurate at detecting the centre of gravity to evenly balance the load; however even the most competent slinger can get it wrong and so will always carry out a slow test lift first.
Any good slinger will always follow certain standards of slinging, so next we will look at the most important principles of safe slinging and also the most important mal-practices to avoid at all costs.
Evaluating The Load; This is most important, everything possible should be done to correctly determine the weight of the load, an estimate of the weight is not acceptable.
Load Stability; A competent slinger may guess where the centre of gravity is likely to be, subsequently the slings can be positioned around this point, ensuring the centre of gravity is directly beneath the lifting points / hook, if this is not precisely possible then the centre of gravity should be inside these points. At this point a test lift needs to be performed, this is where the load is lifted barely clear of the ground to see if the load tilts or seems unevenly balanced in any way, if it does then the slings will need to be placed to a more suitable position and then tested again, this method should be continued until the load is completely stable, only then can the full lift be completed.
Lifting On the tip of the hook; any hooks used for any kind of lifting application are designed to hold the load well in the base/bottom or bowl of the hook, never on the tip as this can lead to the hook being stressed and possible failure. Slingers should ensure the hook of the sling engages freely in the bowl of the lifting point, this is the point that should always take the weight of the load, never the tip.
Shock Loading Slings; shock loading can break a chain sling even when the load is well within the safe working load limit. Fast acceleration forces or shock loads is often the result of sudden movement of the crane or lifting hoist by not taking up the slack of the excess chain prior to total lifting or sometimes from a sudden impact of a falling load. Lifting and also lowering any load must always be carried out at a slow and gradual pace, checking constantly.
Miss-using Shortening Clutches; If a shortening clutch is used it is important that the chain which is lifting the load comes out underneath the clutch at all times, it should never lead out of the top of the clutch, as this can cause the front part of the clutch to come off and subsequently the load will be released.
Battening down; This is a serious mal-practice and should never be tried, it is extremely dangerous. battening down is where a choke hitch is tried to be made secure be means of striking the hook, link or neighbouring chain to try to force the bight into closer contact with the load. The bight must be permitted to assume its natural angle which is usually 120 degrees.
Tag lines; Tag lines are attached to long loads to help to correct any rotational movement.
Hooking back un-used legs; This is where a multi-leg chain sling is used to lift a load, but not all of the legs will be needed, the un-used leg or legs must be hooked back into the master link or master assembly.
Code of signals; The slinger and other operators such as the crane driver must use an approved code of signals prior to any lift, the slinger is in charge of giving any signals and all ather signals should be disregarded except for the emergency stop signal.
Landing the load; Prior to lifting any load the landing place should be prepared, i.e. timber battens placed to land the load on so the chain can be removed easily, never land a load directly on the chain.
Angles of use; Using chain slings at the correct angle is imperative to safe slinging. A multi-leg chain sling exerts a horizontal force that will increase as the angle from the vertical becomes greater. Chain slings must not be used if the angle from the vertical point is bigger than 60 degrees, because the forces in the legs will greatly increase after this point. Angles of less than 15 degrees must be avoided as the load will become unstable.
Slings should also be stored correctly to keep them in good working order, they should be removed from the lifting device, i.e. crane or hoist and placed on a suitable rack, they should never be left on the ground.