Wire rope slings are one of the commonly used rigging gears in various industries. Slings are an important part of rigging mechanism in cranes, hoists, derricks etc. Certain loads require the use of specific types of slings. Sling types can be endless, single, two, three or four leg. Shipbuilding and heavy construction industries use wire rope slings to lift and move metal beams, plates, steel pipes, wood and concrete piling.
Wire rope slings are known for their abrasion resistance, durability, strength. Also the fact that they can adjust easily to the shape of the load that is lifted by the rigging equipment, makes them popular. Another advantage of wire rope slings is that they are ideal for lifting hot materials(heat resistant 400 degree F).
Wire rope slings are flexible and durable, but sometimes they tend to get damaged by the corners or edges of the load they are rigged to. Also, rigging activities taking place at higher temperatures will require slings that can withstand these temperatures. Hence, it is necessary that these slings should be protected from prolonged damage so that they can deliver better service.
Choosing the right sling as per your requirement
Follow the manufacturers' charts and tables on sling types, angles, and rope diameters and select a proper sling which suits the load and the slinging method that you are going to use. Follow the OSHA guidelines for choosing the proper sling type. They call open employers to use wire-rope slings that have permanently affixed and legible identification markings as prescribed by the manufacturer, and that which indicate the recommended safe working load, along with other parameters.
While choosing a wire rope sling for an application, you must ensure that the sling can withstand wear and tear, and can be used in all weather conditions, it can resist distortion, and is perfectly suited for your needs and requirements. It is always recommended that you buy equipment from a authorized and trusted manufacturer to avoid any failure.
The following best practices can help you protect the wire rope slings for a longer time.
- If it is likely that wire rope slings might be out of use for some time, they should be cleaned, and protected from corrosion regularly, i.e lightly oiled.
- When not in use, the wire rope slings should be stored properly so they do not form any twists or knots resulting in damage later.
- Keep them in a properly designed rack. They should not be left lying on the ground where they may be damaged.
- The maximum load capacity for wire rope, natural fiber rope and synthetic fiber rope slings is set out in a series of charts in the OSHA regulation, based on size, construction, etc. Follow it.
- The capacity of a wire rope sling is based on the strength of the wire rope, the load and factors affecting the overall strength of the lifting mechanism. These factors include, type of hitch, number of rope parts in the sling body, diameter around which the sling is bent, and diameter of the pin or hook over which the sling eye is placed.
- Every lift uses three basic lifts, Vertical, Choker and Basket. These will allow you to use the full capacity of the sling, but never under any circumstances shock load the sling.
- Sling angles have a direct and dramatic affect on the rated capacity of a sling. Exceeding these angles can damage the sling for ever. Angles less than 45 degrees are not recommended and those below 30 degrees should be avoided whenever possible.
- Ensure the load is balanced and there is no tilt while lifting the load.
- It is important to clear the area while lifting or suspending the load to avoid accidents.
- Do not drag a loaded sling along the ground or pull it from under a resting load.
Lubrication and Protection
- Lubrication prevents or reduces corrosion and wear due to friction and abrasion. However, before applying any lubricant, the sling user should make sure that the sling is dry and moisture free. Applying lubricants to a wet or damp sling traps moisture against the metal and increases the risk of corrosion.
- Protect the slings using corner saddles, padding’s or wood blocks. Because of the round shape of the wires, very few protectors have been developed for defending the wires and strands from load edges.
- Wires are often ripped or shredded resulting in some loss of strength and this condition can cause hazardous accidents to employees who handle the slings. Such slings should be removed as soon as possible.
- Use of encased plastic rods that help create a barrier between the sling and load can reduce damage to the slings. Some sling protectors are made from super high density synthetic fibers cases which provide exceptional resistance to cutting.
- Use non-acidic lubricants. Slings can be coated with neoprene or a rubberized compound to help fight abrasion and repel foreign matter like metal shavings.
- The sling must be inspected by a competent examiner for any obvious signs of damage before each use. If in doubt of the safety condition of the sling, it must be withdrawn from service and subjected to a thorough examination.
- If the tag or label identifying the sling and its working load limit is detached and the necessary information is not marked on the master link, the sling must be withdrawn from service until it is repaired.
- While inspecting the sling, you must also pay attention to common damage caused due to heat, rope corrosion, broken wires and cuts amongst various others.
- Chain slings must be cleaned prior to each inspection, as dirt or oil may hide damage. The maintenance personnel must inspect the total length of the sling, periodically looking for stretching, binding, wear, or dents.
- If a wire rope sling shows any sign of significant damage, that sling must be removed until it is examined by a person who is qualified to determine the extent of the damage.
- Check the slings both before and after use to detect any damage or defect.
It can be understood that these are not the only factors that should be kept in mind while using slings. But by using the above guidelines to proper sling use and maintenance, it is possible to extend a sling's useful service life.
It is important to select the appropriate sling for the job. Specify your needs to the manufacturers while purchasing them; this will help you choose the perfect sling for your job. Once in use, make it a point to perform regular inspections on these slings to ensure safety. It is advisable that inspection should be conducted by a competent examiner.