Cables are usually prestretched in the workshop, to remove initial inelastic deformation due to the helical structure of the cables and to stabilize the elastic modulus.
Prestretching is made usually with the pulling force ranging from 5% to 50% of the minimum breaking load of the cable for 5 or more cycles. After the last prestretching cycle,
the load is adjusted to the axial force required for the marking of cables.
The prestretching operation is executed on a special prestetching line, with a maximum capacity of 5000 kN where the cable is anchored and pulled, the load cycles and the
measuring force are automatically controlled.
Cables are then measured and marked for cutting and positioning of intermediate clamps, when required.
The measurement method allows for the automatic compensation of thermal elongation, and it is performed in monitored thermal condition.
The length tolerance (mm) after the prestretching and assembly with the sockets is:
where L is the length of the cable in meters.
The length tolerance can change according to specific requirements of the client.