TECHNote™
WORKING LOAD LIMIT
Working
Load Limit (also known as Safe Working Load or Recommended Working Load) is defined
as the maximum load that may routinely be applied to an assembly or component in
straight tension. The other
strength term is ultimate strength (or tensile strength).
Ultimate Strength is the load at which a component or assembly will fail
in a test.
We
have chosen to use the NFPA ratio of 15:1 for ropes and the American engineering
standard of 10:1 for critical use hardware and auxiliary equipment.
We realize that these ratios may exceed proposed standards, but have
selected them because they best apply to the rescue community.
We
show the Working Load Limit (WLL) because the ultimate strength may change
during the life of the product. Whereas,
the WLL remains valid during the normal life of the product.
For example, a 9,000 lbf. rope will lose strength as it is used.
The WLL will remain 600 lbs. throughout the normal service life of the
rope.
Additionally,
rescue products should be chosen and matched based upon their WLL. The item with the lowest WLL limits the system working load
limit. Remember, a chain is only as
strong as its weakest link.
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TECHNote™
WORKING LOAD LIMIT
Working
Load Limit (also known as Safe Working Load or Recommended Working Load) is defined
as the maximum load that may routinely be applied to an assembly or component in
straight tension. The other
strength term is ultimate strength (or tensile strength).
Ultimate Strength is the load at which a component or assembly will fail
in a test.
We
have chosen to use the NFPA ratio of 15:1 for ropes and the American engineering
standard of 10:1 for critical use hardware and auxiliary equipment.
We realize that these ratios may exceed proposed standards, but have
selected them because they best apply to the rescue community.
We
show the Working Load Limit (WLL) because the ultimate strength may change
during the life of the product. Whereas,
the WLL remains valid during the normal life of the product.
For example, a 9,000 lbf. rope will lose strength as it is used.
The WLL will remain 600 lbs. throughout the normal service life of the
rope.
Additionally,
rescue products should be chosen and matched based upon their WLL. The item with the lowest WLL limits the system working load
limit. Remember, a chain is only as
strong as its weakest link.
|