Cable Maximum Pulling Tension

Where a cable is to be pulled in using a winch and steel wire rope, the rope may be secured to the cable by any of the following:

1. A cable stocking of steel wire braid 
2. A pulling eye attached to the cable conductor 
3. A pulling eye over the complete cable end 
4. A pulling eye formed from the armour wires 

The maximum tension which may be used is limited by the tensile strength of the conductors or armour wires, or by the gripping capability of the cable stocking, depending on the method used.

Stress Limits for Cable Materials

Material	Maximum Safe Tensile Stress (S) kN/mm²
Stranded Copper Conductor	0.07
Stranded Aluminium Conductor	0.05
Solid Aluminium Conductor	0.03
Galvanised Mild Steel Armour	0.13
Aluminium Wire Armour	0.04

Method of Calculation 
Using values of S from the table above:

Limited by Conductor 
TC = N * AC * S 
Where TC = Maximum Pulling Tension (kN), N = No. of Conductors, AC = Cross-sectional Area of one Conductor (mm²), and S = Maximum Safe Tensile Stress for Conductor (kN/mm²).

Limited by Armour 
TA = 2.47 * da * (Da + da) * S 
Where TA = Maximum Pulling Tension (kN), S = Maximum Safe Tensile Stress for Armour (kN/mm²), da = Nominal Diameter of Armour Wire (mm), and Da = Nominal Diameter under Armour (mm).

Limited by Stocking 
TS = 0.120 * D 
Where TS = Maximum Pulling Tension (kN), and D = the Overall Diameter of the Cable (mm).

Overall Limiting Tension

Cable OD (mm)	Maximum Pulling Tension (kN)
0 to 15	5
15 to 25	10
25 to 50	15
50 and over	25

The safe pulling tension is the smallest of the calculated values.