Dynamic, Semi Static or Static?
Ropes used for industrial access, climbing and fall arrest can be classified as three types:
Dynamic = elongation at break above 40%
Semi-static = elongation at break 35-40%
Static = elongation at break below 35%
As nylon <Actinic:Variable Name = 'polyamide'/> is the most stretchy rope it is used almost exclusively as semi static and dynamic lines. But Nylon in its yarn state will only stretch 16-27% so extra stretch is added by braiding and by special heat treatments to ensure a 40% stretch is achieved.
The stretch is an important safety factor as the G force of a falling object can be roughly calculated by the fall distance divided by the arrest distance. Therefore a person falling 2 m being arrested by a nylon rope which stretch 200 mm would be subjected to a G force of 10 but if the rope was dyneema with just a 2 mm stretch, the G force would be 1000 and possibly fatal.
Dynamic and Semi Static lines are classed as PPE [Personal Protective Equipment] Category 3, C type inspection. They must be made by a ISO 9001 registered company.