Safe work load calculation of hoisting wire rope and hoist chains

 Hoisting wire rope and hoist chains are the important part of the hoist which are closely bound up with the safe work load, now let’s talk about the formula or rule of thumb to calculate the SWL of ropes and hoist chains.

Basic:

All diameters are measured in millimeters (mm).
All weight are calculated in Kilograms(kg).

Formula SWL-Fiber Rope

Diameter in mm squared=The weight in kg.
(Diameter)²=SWL Kg
Example: For a 12mm diameter rope.....
SWL=12*12=144Kg

Formula Size-Fiber Rope

Choosing the correct rope for the load
Fiber Rope Square root of weight
Example:900Kg load
Rope diameter=√90=30mm

Hoisting wire rope Construction

6*19 (6 strands*19 wires)
6*24 (6 strands*24 wires)
6*37 (6 strands*37 wires)

Electric hoisting wire rope drawing

Electric hoisting wire rope drawing

Formula SWL-Steel Hoisting wire rope

SWL=8D²
8 times stronger than Fiber
(Diameter)²*8=SWL Kg
Example: For a steel Hoisting wire rope of 15mm diameter
SWL=15*15*8=1800Kg

Formula Size-Steel Hoisting wire rope

Square root of the load divide by 8
Example:5000kg load
Ø=√5000÷8
=√625
The diameter of steel Hoisting wire rope=25mm
SWL=8D²

Steel Hoisting wire rope discarding factor

10% of the wires broken in a length of eight times the diameter
Example:6*19 construction 20mm Diameter
6*19=114 wires
10% of 114 wires=11
8*20mm=160mm
11 wires broken over a length of 160mm discard sling

Electric hoisting wire rope drawing

Electric hoisting wire rope drawing

Formula SWL-Hoist chains grade 30

Nine times stronger than Fibre
(Diameter)²*9=SWL (Kg)
Contoh: Garispusat=18mm
SWL=18*18*9
=2916Kg
SWL=9D²

Formula SWL-Rantai Gred Peblagai

Grade 30 hoist chains=9 times stronger than fiber rope
Grade 40 hoist chains=12 times stronger than fiber rope
Grade 60 hoist chains=18 times stronger than fiber rope
Grade 80 hoist chains=24 times stronger than fiber rope

Formula for different grades

0.3*diameter²MM*Grade of Hoist chains
Or SWL=0.3*D²*Grade

Formula Size-Hoist chains of different grade

Square root of the weight (Kg) divide by the grade of China
Example: Weight=5400Kg & Grade=40
Diameter of Hoist chains=√Weight÷(0.3*Grade)
=√5400÷(0.3*40)
=21.2 mm
W=12D²

Load factor 2 slings at an angle
Sling angle 30° 60° 90°
Load factor 1.93 1.73 1.41

Comparative Methods of Wire Rope Slinging

Wire rope slings

Full Wrap

Hoisting wire rope safe working load drawing

Hoisting wire rope safe working load drawing

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