Dear Readers,
SWL is very important and essential for rigging & hoisting works during construction activities and sometimes stated as the Normal Working Load (NWL).
SWL is very important and essential for rigging & hoisting works during construction activities and sometimes stated as the Normal Working Load (NWL).
It is the mass or the
force a piece of lifting equipment, lifting device or
accessory can safely utilize to lift, suspend, or lower a mass without fear of
breaking. Usually marked on the equipment by the manufacturer and is often 1/5 of
the Minimum Breaking Strength (MBS) although other fractions may be
used such as 1/4, 1/6 and 1/10.
The SWL is determined by dividing the minimum
breaking strength (MBS)
of a component by a safety factor assigned to
that type and use of equipment. The safety factor generally ranges from
4 to 6 unless a failure of
the equipment could pose a risk to
life; in that instance the safety factor would be a 10.
For example, if a
line has an MBS of 1,000 pounds and a safety factor of 5, then the SWL would be
200 pounds. 1000/5 = 200.
Thumb Rule for Determination of SWL of Wire rope slings:
SWL = 8*D2; in Tons; Where D diameter of rope
in inches.
Example:
1 Inch diameter rope 1*1*8 = 8 Tons
½ inch diameter rope 0.5*0.5*8 = 2 Tons
Other way to calculate the SWL of any wire rope by
- Obtained the Breaking strength of the wire rope as per the class.
- Consider the Safety factor (Generally taken 5 for wire rope, except taken 10 while use for lifting person)
- Divided the breaking Strength by Factor of safety.
