Know your Industrial Lifting Slings
Lifting is an everyday operation in pretty much any industry. Not only is it a vital and unavoidable task, but also prone to risk and accidents. It is very important that a user understands the different type of lifting slings that are available and the benefits and drawbacks of each. A good knowledge of the slings will ensure that the right product is chosen for a job.
Lifting slings are broadly classified into three categories.
1. Wire Rope Slings (https://www.liftek-intl.com/steel-wire-rope-slings) 2. Chain Slings (https://www.liftek-intl.com/chain-slings-grade-80-fittings) 3. Synthetic Slings (https://www.liftek-intl.com/polyester-flat-webbing-slings-endless-round-slings)
1. Wire Rope Slings
Wire rope slings are fabricated by terminating eyes on the ends of the steel wire ropes using steel or aluminum sleeves, also called as ferrules. These can be fabricated in single-leg and multi-leg systems or into an endless sling called cable laid grommet. They can be used in straight, basket or choker hitch configurations.
Benefits of Wire Rope Slings
• Ideal for heavy-duty and tough operations. • Excellent properties of strength, durability resistance to abrasion, and flexibility • Extensive range of capacities possible depending on the steel grade and wire rope diameter • Available in single-leg and multi-leg assemblies. • Can be used to lift loads in high temperature environments • Easy availability of wide range of standardized end fittings to suit different lifting scenarios.
Drawbacks of Wire Rope Slings
• Inferior strength-to-weight ratio compared to other types of slings, especially synthetic slings. This adds to transport costs, rigging up time, effort, and costs especially in heavy-lift operations. • Wire rope slings are difficult to inspect especially for internal defects/damages like corrosion and broken wires. • Very low possibility for repair in case of damage beyond the normal inspection acceptance criteria. Rejection and discarding the sling is the only option.
2. Chain Slings
Chain slings are one of the most common types of lifting slings used around the world. Chain slings are made up of lengths of high tensile alloy steel chain, with a variety of fittings attached. Alloy steel used for manufacturing lifting chain is of specific tensile grade and suitable chemical and physical properties. The chain is heat treated for tensile strength, resistance to wear and shock absorption. These can be fabricated in single-leg, multi-leg and endless configurations.
Benefits of Chain Slings
Ideal for heavy-duty, harsh and tough lifting operations.
Resistant to high and low temperatures, chemical exposure, and physical damage.
In case of damage, it’s easy to repair and replace specific lengths of chain and the associated fittings. Need to be re-certified by competent person after any such repair or change.
Comparatively easier to inspect.
Easy availability of wide range of standardized end fittings to suit different lifting scenarios.
Drawbacks of Chain Slings
Expensive sling when compared to other options in the market.
Bulkier and more difficult to handle than synthetic slings. Very sensitive to kinks and knots in the chain.
May damage load being lifted due to bulky nature of sling, especially sensitive and/or delicate loads.
3. Synthetic Slings
Synthetic slings are one of the most common pieces of lifting equipment. They come as Web bing slings which is a flat webbing sewn together in single or multiple plies or as Round Slings which is endless loop of yarns, covered by a woven tubular cover/jacket. The material is typically polyester or nylon. Synthetic slings are ubiquitous in lifting operations due their low cost, ease of availability and wide range of sizes. These can be used in straight, basket or choker hitch configurations.
High performance round slings made from HMPE(high modulus polyethylene) is an increasingly popular option for heavy lifting jobs and engineered lifts.
Benefits of Synthetic Slings
Economical, easily available, lightweight, and wide range of sizes.
The soft and flexible polyester/nylon material grips and conforms to the shape of the load.
Superior strength-to-weight ratio especially for HMPE slings. They are strong enough to lift heavy loads but soft enough to not damage sensitive and delicate loads from scratching and crushing.
Synthetic slings are non-sparking, non-conductive and can be used safely in hazardous environment having a risk of explosion.
Drawbacks of Synthetic Slings
In comparison to wire rope slings and chain slings, synthetic slings are more prone to damage due to cuts and abrasions.
Users must consider the adverse effects of acid and/or alkalis on synthetic slings in applications involving exposure of the slings to chemicals.
Medium- and long-term exposure of synthetic slings to UV rays will lead to strength reduction.
Synthetic slings are not to be used in applications involving elevated temperatures since it has low resistance to heat.
The drawbacks listed above are negated to a large extent in high performance HMPE slings. But such slings are much more expensive than conventional synthetic slings and wire rope and chain slings.
Very low possibility for repair in case of damage beyond the normal inspection acceptance criteria. Rejection and discarding the sling is the only option.
Conclusion
Before selecting a lifting sling, it is good to consider and answer the below questions to zero-in on the best option.
Does the load have sharp edges and corners that may adversely impact the sling?
Is the load valuable and/or fragile and susceptible to scratches and damage on contact with the sling?
Is the load regular shaped or irregular shaped with an off-center CoG?
What is the temperature and chemical environment in which the load is being lifted and will it impact the sling?
What are the sling angles, height of lift, end attachments, number of lift points and type of hitch needed for the lift?
We hope that the answers to the above questions and the pros and cons of various types of slings listed above, will provide the user with a good guidance of the correct sling for the job.
Liftek has a long standing reputation for providing high quality lifting and rigging equipment and technical support for jobs that range from routine and repetitive lifts to complex and engineered heavy-lift operations .
Feel free to contact us at [email protected] for your industrial lifting sling requirements and our team of specialists will be happy to assist you.