Flat woven webbing slings, also commonly known as Polyester Webbing Slings or Lifting Belts, are used for variety of lifting purposes. They are a form of textile sling which is soft and easy to handle whilst offering rigidity across their width. These qualities make them ideal for handling loads which require some support when being lifted as the load is spread across the full width of the webbing, thus avoiding point contact as in case with chains or ropes. They are therefore less liable to damage finished surfaces than ropes, wire rope or chain sling. However, they are less robust and more easily damaged than equivalent capacity wire rope and chain sling.
The WLL (Working Load Limit) of a webbing sling is based on the minimum breaking load of the sewn webbing component and is calculated on the basis of Factor of Safety.
Colour coding is often used in standards to relate to WLL of the Sewn Webbing Component. However standards prior to current standards permitted, but did not require colour coding, hence colour coding is not universal so a reference to label is always made to ascertain WLL of a sling.
The Webbing Slings are normally made for Multiple Filament High Tenacity Yarns of Polyester/Nylon/Polypropylene and same can be identified by colour of Identification tag, which should be Blue for Polyester, Green for Polyamide (Nylon) and Brown for Polypropylene (as per EN-1492-1 standard, which is normally followed for colour codings)
The webbing slings are sewn with thread of same materials of webbing and normally are of different/contrasting colour for easy inspection of sewn component of the webbing sling.
FREQUENTLY ASKED QUESTIONS ABOUT WEBBING SLINGS
Can I use webbing sling in a chemical environment (Specially Acidic Environment)?
If the webbing sling is for use in chemical environment, Always consult the supplier for advice, However Man-Made Fibres offer a high resistance to chemicals and can, subject to correct material selection, be used in certain chemical environment without detriment.
A) Polyester is resistance to moderate strength acids but is damaged by Alkalis.
B) Polyamide (Nylon) is virtually immune to the effect of alkalis but is attacked by moderate strength acids. Attention is also drawn to its loss of strength on wetting which can be in the order of 15%.
C) Polypropylene is little affected by either acids or alkalis but is damaged by some solvents, tars, paints, etc. It is suitable for applications where the highest resistance to chemicals, other than solvents, is required.
In what temperature range can the Webbing Slings used?
Webbing Slings manufactured from polypropylene are suitable for use in temperature range of -40°C to 80°C, whilst those produced from polyester or polyamide (Nylon) are suitable for the -40°C to 100°C. These temperatures may vary in a chemical environment and should be checked by references to the supplier. Under no circumstances should webbing slings be used at temperature outside of the range advised by the manufacturer.
How can I protect webbing slings for damage from sharp edge and abrasive surface of object being lifted?
A webbing sling should be selected which is fitted with a protective sleeve or moulded wear pod, or proper steps should be taken to ensure suitable protective packing is available. Care must also be taken to protect the sling from edges and corners that might damage the sling. Protective wear sleeves are normally used for this purpose and the sleeves can be replaced upon damage immediately to ensure long service life of the webbing sling.
What is Protective Sleeve?
A Protective Sleeve is a tubular sleeve, either fixed or movable, which may be of woven fabric, moulded polymer or other material placed over the webbing sling to provide extra protection to the webbing. It has no effect on the strength of the sling. Similar type of protection is also used in soft eyes of webbing sling.
What is normal testing practices for webbing slings and manufacture’s test certificate?
Webbing slings are not subject to proof load testing, as this could be detrimental to the sling and will not reveal any additional information. They are however subject to strength tests made on representative slings during manufacture. A manufacturer’s test certificate is supplied with each sling, which confirms complaince with the manufacturing standard and certifies that such manufacturing and sampling tests as are required have been completed. In the case of slings with integral fittings, this will also contain details of the verification of the fitting.
However before taking a webbing sling into application in a factory, a certificate (Normally Form-10 Prescribed under Rule 60) is required as per Factory Act (applicable in India) and this certificate issued by a Competent Person appointed by the Chief Inspector of factories of the state. (Please refer to section 29 of The Factories Act 1948 in this regard)
What is the difference between a Webbing Sling and Round Sling?
A webbing sling has two eyes at two winds and has a flat construction. It is a very popular design, but it has one major disadvantage. The fibers which provide the strength to lift the load are also the ones which come in contact with the load. Therefore, in case of damage to the yarns, the sling has to be taken out of service.
However, A Round Sling is an endless hank of yarn wound without any break and is a far better designed sling. The inner core yarn (which provides strength to lift the load) is protected by the outer casing, which comes into contact with load. Also the (load) bearing points (the points which go on the crane hook) keep changing, whilst on a webbing sling the points are fixed (at the “eyes” of the sling) and open to wear and tear. If these points are not inspected regularly, they could lead to potential “weak spots” in the sling.
What is Safety Factor/Factor of Safety?
Safety factor is Ratio of Minimum Breaking Strength (MBS) aka Minimum Breaking Load (MBL) to Safe Working Load (SWL) aka Working Limit Load (WLL) of a sling. The higher the safety factor is, the more safe is the sling.
The safety factor usually ranges between 4 and 8 for lifting equipment’s.
As Such,
SAFETY FACTOR = MINIMUM BREAKING LOAD/WORKING LOAD LIMIT
(SWL is no longer use to identify the maximum capacity of equipment as it being too vague and leaving it open for legal issues.)
What care should be taken for storage and Handling of Webbing Slings?
When not in use, webbing sling should be returned to proper storage. The storage area should be dry, free from injurious pollutants and extreme of temperature, together with following :
1) Prior to placing in storage, the sling should be inspected for any damage which may have accrued in use.
2) Store webbing slings on a suitable rack.
3) Store slings away from acids, alkalis and solvents etc.
4) Store at ambient temperatures, away from any source of heat.
5) Webbing slings are affected by ultra-violet rays and should not be stored in direct sunlight or sources of ultra-violet radiation.
6) Slings which have been in application with chemicals should be thoroughly washed in clean water or otherwise neutralised prior to storage.
7) Slings which are wet can be hung up and allowed to dry naturally, provided that chemicals are not involved as drying process may concentrate the chemical to an air acceptable level. Do not apply heat air any other means of forced drying.
8) Wet slings which have become frozen should not be returned to storage but should be allowed to thaw and dry naturally.
Can Webbing Slings be repaired, if damaged?
No, Webbing Slings have to be taken out of service if damaged or cut.
How do I inspect Webbing Slings?
Webbing Slings must be checked physically by the user every day while taking into use for first application. Inspecting webbing slings is easy and only visual. Follow the simple steps:-
1) Lay down the sling in a well lit area, on a flat surface (table or ground).
2) inspect the entire body along with the length of sling. Observe for cuts, abrasions and damage to the surface of webbing. If there are any cuts or abrasions damage to yarn, the sling must be taken out of use immediately.
3) Inspect the webbing sling eyes for any visible damage, also check if there is any damage to stitching or puncture in webbing, if nay such damage is found, take sling out of use immediately.
4) Inspect for identification tags and ensure that matches the capacity and length of the slings. If identification tag is missing or illegible it must be taken out of use immediately.
What are the disadvantages of using Webbing Slings?
The disadvantages of using a webbing sling are :-
1) Can be easily cut or damaged if used unprotected over sharp edges.
2) Can not be used in temperatures exceeding 100°c.
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