16.5.5 Adverse Conditions
The selection of webbing slings for use in adverse conditions should be carefully considered. Their use in high temperatures is more limited than that of slings of other materials, however they have selective resistance to chemicals and can be used in some applications where other materials cannot or require special measures to be taken.
16.5.5.1 Temperature
Flat woven webbing slings manufactured from polypropylene are suitable for use in the temperature range -40°C to 80°C whilst those produced from polyester or polyamide (nylon) are suitable for the range -40°C to 100°C. These temperatures may vary in a chemical environment and should be checked by reference to the supplier. Under no circumstances should webbing slings be used at temperatures outside of the range advised by the manufacturer.
Care must be taken when selecting slings for use at low temperatures. Although the qualities of the materials used for flat woven webbing slings makes them suitable for use at temperatures as low as -40°C, if moisture is present, ice will be formed. Ice will both act as an abrasive and cutting agent and will damage the sling. Slings selected for use at low temperatures should be dry and steps must be taken to prevent ice forming on or, more importantly, between the woven strands of the webbing.
16.5.5.2 Chemicals
If the webbing sling is for use in a chemical environment, consult the supplier for advice. Man-made fibres offer a high resistance to chemicals and can, subject to correct material selection, be used in certain chemical environments without detriment.
Polyester is resistant to moderate strength acids but is damaged by alkalis.
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%.
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.
Consideration must be given to the suitability of the material from which terminal and connecting fittings are made. Certain grades of steel are susceptible to hydrogen embrittlement as the result of contact with acids. This can seriously reduce the ductility and load-bearing capacity, cause cracking and catastrophic brittle failures at stresses below the yield stress of the material. Other metals may be subject to corrosion. The advice of the supplier should always be sought when selecting flat woven webbing slings and/or fittings for use in chemical environments.