14.5.3 Adverse Environments
In adverse environments, the SWL must be reduced from a value equal to the working load limit in accordance with the following recommendations.
14.5.3.1 High temperature conditions
As the temperature which a sling attains in service increases, its strength decreases. Care must be taken to account for the maximum temperature which can be reached by the sling in service. This may be difficult to determine in practice, but under-estimation of the temperature involved must be avoided. The effect of increasing temperature on the strength of the various grades of slings is indicated in Table 1.
Grades 60, S, T, 8 Temperature of Sling | Strength of Sling |
|---|---|
Up to 200º C | Nominal strength rating |
*200º to 300º C | 90% of strength rating |
*300º to 400º C | 75% of strength rating |
Over 400º C | Not recommended – refer to manufacturer |
Grades 40, M, 4 Temperature of Sling | Strength of Sling |
Up to 300º C | Nominal strength rating |
*300º to 350º C | 85% of strength rating |
*350º to 400º C | 75% of strength rating |
*400º to 475º C | 50% of strength rating |
Over 475º C | Not recommended – refer to manufacturer |
*For grades not listed refer to the manufacturers specific instructions
The use of a sling within these temperature ranges does not imply any permanent reduction in strength when the sling is returned to normal temperatures. If slings are accidentally exposed to temperatures in excess of the maximum permissible temperatures indicated above, they should be withdrawn from service and referred to a Competent Person and/or the manufacturer.
14.5.3.2 Low temperature conditions
Chain slings covered by most standards will not be adversely affected by temperatures down to minus 40°C (see note below) and no reduction from working load limit is therefore necessary on this account. Where slings are to be used at temperatures below minus 40°C, the manufacturer should be consulted.
Depending on the manufacturing processes some grades of chain can only be used as low as minus 20°C. Care must therefore be taken to ensure the correct chain is selected and advice sought from a Competent Person and manufacturers literature.
14.5.3.3 Acidic conditions
Chain slings manufactured to Grades S, T, 8 (or 80), 10 (or 100) and 12 (or 120) should not be used either immersed in acid solutions or exposed to acid fumes, as this can cause and phenomena known as hydrogen embrittlement or hydrogen cracking, that can seriously reduce the ductility and loadbearing capacity, cause cracking and catastrophic brittle failures at stresses below the yield stress of sling material.
Attention is drawn to the fact that certain coating processes, i.e. galvanizing, give rise to these conditions. Slings of Grade S, T, 8 (or 80), 10 (or 100) and 12 (or 120) should not therefore be used in such an environment nor should they be subjected to such processes themselves without the express approval in writing from the manufacturers.
Chain slings of Grade 40, M or 4 may be used in such an environment subject to the following precautions:
The SWL of such a sling should not be greater than 50% of the working load limit.
The sling should be thoroughly washed in clean water immediately after use.
The sling should be given a thorough examination by a Competent Person prior to use each day.
In other conditions in which the sling is likely to be subjected to chemical attack, the manufacturer should be consulted.