Care & Use of Synthetic Web Slings
- Determine weight of the load.
- Select sling having suitable characteristics for the type of load, hitch and environment.
- Slings shall not be loaded in excess of the rated capacity. Consideration should be given to sling angles, which are discussed below.
- Slings with fittings used in a choker hitch shall be of sufficient length to assure that the choking action is on the webbing.
- Slings used in a basket hitch shall have the load balanced to prevent slippage.
- Slings shall not be dragged on the floor or over an abrasive surface.
- Slings shall not be twisted or tied into knots, or joined by knotting.
- Slings shall not be pulled from under loads when the load is resting on the sling.
- Slings shall always be protected from being cut by sharp corners, sharp edges, protrusions or abrasive surfaces.
- Do not drop slings equipped with metal fittings.
- The opening in fittings shall be the proper shape and size to insure that the fitting will seat properly in the hook or other attachment.
- Slings should be stored in a cool, dry, and dark place, and should not be exposed to ultra-violet light (sunlight).
- Chemically active environments can affect the strength of synthetic web slings in varying degrees ranging from none to total degradation. The sling manufacturer should be consulted before using slings in chemically active environments.
a) Nylon is subject to degradation in acids, ranging from none to total degradation.
b) Polyester is resistant to many acids, but is subject to degradation ranging from none to moderate in some acids.
a) Polyester is subject to degradation in alkalis, ranging from none to total degradation.
b) Nylon is resistant to many alkalis, but is subject to degradation ranging from none to moderate in some alkalis.
- See chart below for effects of other chemicals on web slings.
Chemical Resistance of Web
Acids Alcohols Aldehydes Strong Alkalis Bleaching Agents Dry Cleaing Solvents Ethers Halogenated HydroCarbons HydroCarbons Ketones Oils Crude Oils Lubricating Soap & Detergents Water & Seawater Weak Alkalis Nylon No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Polyester • Yes No •• Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes
**Degraded by strong alkalis at elevated temperatures
- Nylon and polyester slings shall not be used at temperatures in excess of 194 degree F (90 degree C), however, they may be used in temperatures as low as -40 degree F (-40 degree C).
- Slings incorporating aluminum fittings shall not be used where fumes, vapors, sprays, mists or liquids of alkalis and/or acids are present.
- Environments in which synthetic web slings are continuously exposed to ultra-violet light (sunlight) can affect the strength of synthetic webbing in varying degrees, ranging from slight to total degradation. The degradation is also cumulative.
Sling angles have a direct and oftentimes dramatic affect on the rated capacity of a sling. This angle, which is measured between a horizontal line and the sling leg or body, may apply to a single leg sling in an angled vertical or basket hitch, or to a multi-legged bridle sling. Anytime pull is exerted at an angle on a leg, the tension or stress on each leg is increased. To illustrate, each sling leg in a vertical basket hitch absorbs 500 lbs. of stress from a 1,000 lb. load. The same load, when lifted in a 60 degree basket hitch, exerts 577 lbs. of tension on each leg.
It is critical therefore, that rated capacities be reduced to account for sling angles. Angles less than 45 degrees are not recommended and those below 30 degrees should be avoided whenever possible. Use the formula and chart shown below to calculate the reduction in rated capacities caused by various sling angles.
|Sling Angles in Degrees||Factor||Sling Angles in Degrees||Factor|