How to use steel wire rope slings
What to do before starting a lifting operation:
Be sure that the load can be lifted with a steel wire rope sling.
The same must not cause damage to the load or to itself. If the steel wire rope sling must be attached directly to the load, be sure that the attachment points are in the right condition in order to satisfy the loading operation.
The load and the precise weight of the load must be always determined. Many information can be taken from documents such as delivery notes, manuals and drawings. If these informations are not available the total bulk of the load must be determined by a competent person responsible for lifting operation.
Once the correct way to lift the load has been decided, an adequate sling with suitable capacity or working load limit (WLL) should be determined. If it is possible, accessories diameter, usually placed in the ending eyes of the sling, must not be inferior more than two times the steel wire rope diameter.
Be sure steel wire rope sling is in good condition. If some steel wire rope slings are found damaged and not enough safe they must be immediately removed from service.
È necessario assicurarsi che la braca sia in buone condizioni. Le brache trovate danneggiate o deteriorate al punto da essere ritenute poco sicure per l’uso devono essere eliminate immediatamente.
Be sure load is correctly balanced. Steel wire rope sling must be fixed to the appropriate attachment points. If these points are not mentioned, the position of the centre of gravity must be determined.
Steel wire rope sling type and it’s correct use must guarantee that the load does not turn upside down or slide down and hook must be placed exactly at the centre of gravity, if this is not possible the load must be lifted with care.
Be sure load does not include loose parts. If loose parts are found it must be tightly fastened. Steel wire rope sling must not be attached directly to fiber slings, if not specified.
How to install a steel wire rope sling
Before installing a steel wire rope sling be sure that:
a) sling length does not bend;
b) ending parts of the sling are correctly positioned;
c) angle of the sling must not be superior to the one arranged;
d) sling must not be winded up around dangerous edges in order to avoid damages that can reduce its effectiveness.
Note 1 – The edge is sharp when the bending radius of the steel wire rope is inferior to its diameter.
Note 2 – When a steel wire rope is bended on it’s diameter it looses 50% of it’s original capacity.
Loading and Unloading
During loading and unloading operations be sure that
a) international codes and norms are used;
b) nothing hampers the movement of the load;
c) steel wire ropes or pipes does not hamper load movements;
d) all the people working in the lifting operation can communicate
e) Operators must be safe during lifting operation
Note – Particular attention must be paid by operators working near the load.
f) load must be balanced;
g) load must be lift-up and let down very slowly;
h) steel wire rope sling does not entangle under the load, if necessary put a bar so that the load can be leaned down without causing damages.
Following precautions must be taken:
a) load must not go over a person without paying the greatest attention
b) a lifted load must not be left unguarded
c) load must not be dragged on the floor
d) steel wire rope slings must not be exposed to liquid substances.
e) steel wire rope sling has been produced to guarantee a full load capacity when used in an environment with temperatures between -40°C
Inspection operations and unloading principles
During service steel wire rope sling is subjected to particular conditions that influence it’s safety characteristics
Be sure sling quality permits it’s use during the time.
Sling must be inspected in order to evaluate eventual damages before every use, and must be subjected to frequent inspections during the time.
Every inspection must be carried out by a competent person.
If doubts regarding sling safety characteristics arise it must be absolutely changed.
An inspection is a visual examination of sling condition in order to detect eventual damages dangerous for its use, such as:
a) broken wires
b) steel wire rope distortions
c) buckles and accessories distortions
d) excessive wear and tear
e) damages caused by high temperatures
A complete examination must be carried out by a competent person in order to detect sling safety conditions.
A complete examination must be carried out every twelve months, but it can be reduced in special cases.
Examination results must be registered on special books.
Evaluation sling conditions and discarding values
Broken wires are dangerous because:
a) they can hurt workmen hands
b) they reduce steel wire rope capacity
Broken wires are usually caused by mechanical damages even if corrosion is one of the main reason.
Presence of broken wires along steel wire rope sling does not always affect it’s capacity, but it can be considered as a reason for corrosion or mechanical damages.
If total number of visible broken wires in a steel wire rope length exceeds the 5% of the total quantity, steel wire rope sling must be removed and consigned to a competent person’s care.
If three or more broken wires are detected in a very short length, steel wire rope sling should be removed from use.
Excessive Wear and Tear
If the excessive wear and tear reduces the diameter of the steel wire rope up to 90% of the nominal diameter, the steel wire rope sling should be removed.
Corrosion can occur when steel wire rope slings have not been properly stored up or have been used in precarious conditions such as operations in acid or alkaline baths.
The effect is clearly visible in the loss of flexibility and surface roughness.
Superficial layer of rust do not destroy steel wire rope strength, but can prognosticate an internal corrosion.
If suspect exists steel wire rope sling must be immediately removed from service.
Significant steel wire rope distortion
Steel wire rope slings must be removed in case of bending, crushing, or in presence of knots.
Sling capacity can be not reduced also if some deformations occur.
If the distinction between dangerous and acceptable distortion is not very clear, steel wire rope sling should be removed and checked properly.
Loss of lubrication, wear and tear of wires caused by high voltage may be dangerous.
Steel wire ropes subjected to high temperatures for a long period reduce their working capacity.
In this case steel wire rope slings must be removed from service and checked properly.
Deteriorated or Defective Lifting Accessories:
Pay attention to
a) unexpected opening of hooks
b) distortion or wear and tear of eyes or thimbles
c) buckle breakage
d) buckle strong abrasion or crushing
e) buckle expulsion
f) concentration of broken wires near the buckle
g) unusual effects in the sling eye due to an excessive pin or uncorrect thimbles
h) broken wires on the superficial layer of the sling eye, when used, for example, with a too small pin
Conditions mentioned at points a) and b) are usually determined by overloading operations and for these reasons they must be removed.