Use of textile slings
Use in adverse environments or hazardous applications
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The chemical resistance of round slings and webbing slings depends on the materials they are made from. The effects of various chemicals on synthetic fibers are summarized below: a) Polyester (PES): Resistant to most mineral acids but damaged by alkalis. b) Polyamides (PA): Highly resistant to alkalis but vulnerable to mineral acids. c) Polypropylene (PP): Largely unaffected by acids or alkalis, making it suitable for applications requiring maximum chemical resistance, except against solvents. d) Dyneema®: Offers excellent resistance to both acids and alkalis. ATTENTION Solutions of acids or alkalis that are harmless in low concentrations can become sufficiently concentrated through evaporation and cause damage. Slings that become contaminated should be removed from service immediately, soaked in cold water, allowed to dry naturally, and inspected by a competent person. If in doubt, always contact CERTEX Deutschland GmbH for guidance. Important Note: Slings with grade 8/10/12 fittings and multi-leg slings with grade 8/10/12 master links must not be used in acidic conditions. Exposure to acids or acidic fumes can cause hydrogen embrittlement in grade 8/10/12 materials. If chemical exposure is anticipated, consult CERTEX Deutschland GmbH for further advice. |
Temperature Effects
Round slings and webbing slings are suitable for use and storage within the following temperature ranges:
a) Polyester and Polyamide: -40°C to +100°C
b) Polypropylene: -40°C to +80°C
c) Dyneema®: -50°C to +70°C
At low temperatures, ice may form if moisture is present. Ice can act as a cutting or abrasive agent, potentially causing internal damage to the sling. Additionally, ice reduces the sling’s flexibility, which, in extreme cases, can render it unfit for use. These temperature ranges may vary when slings are exposed to chemical environments. In such cases, advice from CERTEX should be sought.
For drying slings, limited indirect ambient heating is acceptable within these temperature ranges.
Note: Dyneema® does not absorb water, unlike other materials such as polyester and polyamide
Affects of ultra-violet radiation
The man-made fibres from which the roundsling is produced are susceptible to degradation if exposed to ultra-violet radiation. Roundslings should not be stored in direct sunlight or sources of ultraviolet radiation
Before first use
Before first use of the sling it should be ensured that:
a) the sling corresponds precisely to that specified on the order;
b) the manufacturer’s certificate on hand;
c) the identification and WLL marked on the sling correspond with the information on the certificate;
d) the sling has been maintained.
e) the sling is suitable for intended lifting.
Safe Use
Preparation
When selecting and specifying round slings and webbing slings, the following factors should be carefully considered:
- The required working load limit (WLL), accounting for the mode of use and the characteristics of the load to be lifted.
- The size, shape, and weight of the load, along with the intended method of use, working environment, and the nature of the load, as these all impact the correct selection of the sling.
The chosen sling must be both strong enough and of the appropriate length for its intended mode of use. If multiple slings are used to lift a single load, they should be identical. Additionally, the material of the roundsling should be resistant to any adverse effects caused by the environment or the load itself.
Consideration must also be given to ancillary fittings and the lifting appliance, which should be compatible with the sling(s). The sling's end design should also be assessed, ensuring end fittings or soft eyes are appropriate for the task.
When using slings with soft eyes alongside a hook or fitting:
- The minimum length of the soft eye should be at least 3.5 times the maximum thickness of the hook or fitting.
- The angle formed in the eye must never exceed 20° under any circumstances.
When connecting a sling with a soft eye to a lifting device:
- The part of the device in contact with the sling’s eye must be straight if the sling’s bearing width is less than 75 mm.
- In such cases, the device must have a bend radius of at least 0.75 times the sling's bearing width.
- For wide slings, the hook’s inner radius may impact the sling, as an overly sharp bend can prevent uniform load distribution across the sling’s full width.
Usage
Round slings and webbing slings must not be overloaded. The appropriate mode factor should be applied (refer to the table). Some WLL values for specific modes may be provided on the label. For multi-leg slings, the maximum permissible angle to the vertical must not be exceeded.
Protection
Slings must be shielded from sharp edges, friction, and wear caused by either the load or the lifting appliance. If reinforcements or protective measures against corner damage and/or abrasion are provided as part of the sling, they must be correctly positioned. Additional protection may also be required to ensure safe use.
Method of Connection: Basket Hitch, Choke Hitch, and Symmetry
Method of Connection
Adhering to good slinging practices is essential. The slinging, lifting, and lowering operations should be planned in advance to ensure safety.
Round slings and webbing slings must be correctly positioned and securely attached to the load. Slings should be placed on the load in a way that allows them to adopt a flattened form, ensuring the load is distributed evenly across their width. Slings must never be knotted or twisted. Stitches must never be placed over hooks or other lifting appliances; instead, they should always rest on the standing part of the sling. Labels should be protected from damage by keeping them away from the load, the hook, and choke angles.
The load must be secured by the sling(s) in a manner that prevents it from toppling or falling out during the lift. Slings should be arranged so that the lifting point is directly above the load’s center of gravity, ensuring balance and stability. If the center of gravity is not below the lifting point, the sling may shift during the lift.
Basket Hitch
When using a basket hitch, the load must be secured, as there is no gripping action like that of a choke hitch, and the sling may roll through the lifting point. When using slings in pairs, a spreader is recommended to ensure the sling legs hang as vertically as possible and to distribute the load evenly between the legs.
Choke Hitch
When a sling is used in a choke hitch, it should be positioned to allow the natural 120° angle to form, avoiding the generation of heat through friction. A sling should never be forced into position or tightened artificially. For additional security and to prevent the load from sliding, a double choke hitch can be used.
Symmetry of Loading
For multi-leg slings, the working load limit (WLL) is determined assuming the load distribution is symmetrical. This means: When lifting, the sling legs must be symmetrically arranged in plan and subtend equal angles to the vertical. In three-leg slings, if the legs are not symmetrically positioned, the greatest tension will occur in the leg where the sum of the angles to the adjacent legs is greatest. For four-leg slings, the same effect applies, but the rigidity of the load must also be considered. With a rigid load, the majority of the weight may be borne by only three or even two of the legs, with the remaining legs serving merely to balance the load.
Safety of Lifting, Landing the Load, and Storage
Safety of Lifting
Ensure the safety of all personnel during lifting operations. People in the danger zone must be warned, and if necessary, evacuated from the immediate area.
Hands and other body parts must be kept away from the sling to prevent injury as the slack is taken up.
A test lift should be performed: Take up the slack until the sling is taut. Raise the load slightly to check that it is secure and assumes the intended position. This is particularly important with basket hitches or other loose hitches, where friction retains the load.
If the load tilts, it should be lowered, and the attachments re-positioned. Repeat the trial lift until the load’s stability is ensured. During the lift, ensure the load is controlled to prevent accidental rotation or collision with other objects.
Avoid snatch or shock loading, as this will increase the forces acting on the sling. Never drag the load or the sling over the ground or rough surfaces.
Landing the Load
Lower the load in the same controlled manner as it was lifted. Avoid trapping the sling when lowering the load. The load should not rest on the sling if this could cause damage. Do not attempt to pull the sling out from beneath the load while it is resting on it.
Storage of Slings
After the lifting operation, slings should be returned to proper storage. Store slings in a clean, dry, and well-ventilated area, at ambient temperature, on a rack, away from: Heat sources Chemicals or fumes Corrodible surfaces Direct sunlight or other sources of UV radiation Inspect slings for any damage before storing them.
Damaged slings must never be returned to storage. If slings have been exposed to acids or alkalis: Dilution with water or neutralization with suitable agents is recommended before storage.
Depending on the sling material and the chemicals involved, consult CERTEX Deutschland for additional cleaning recommendations.
Slings that have become wet through use or cleaning should be hung up and allowed to dry naturally.
