This is a difficult question. I have some praktical experience with cranes with electromagnets to pick up steel plates. I did maintenance and new istallations.

Lifting steel plates has a high load as a result, because when you lift plates you always lift more plates than you want, so the initial load is always around the maximum of the crane. From this experience I know that in two shift 6 days a week operation the steel wires had to be exchanged twice a year.

Things to be taken into acount are:

1. Lubrication of the wires is important.

2. The sheave diameter / rope diameter is very important. Bending of the cabel on a too small sheave will reduce the life very much.

3. The cable will break slowly. The inside will break first, especially when you use Plastic sheaves. So during inspection the cable must be twisted open for inspection and a certain amount or broken wires on a certain length is allowed. But in our case we then exchanged the cables.

4. The constructyion of the cable is important. there are cables that dont rotate when loaded and other do rotate. The cables free from rotation need a larger safety margin. (in our case a safety margin on rupture of 5)

5. Low temperatures are bad for the cables. we had most ruptures or damages in winter.

The situation descibed above is one of the worst case loading situations that can occur, so in many cases the life of the cables will be much longer.

J.H. Brinker thank you for sharing your valuable experience of cranes. Im looking for a data where readings are taken for some time so that i can compare its results with theoretical values and validate my model.

When you are looking for praktical information you could contact for instance Mennens Groningen in the Netherlands. They deliver all part for lifting and do a lot of testing in their shop and on site.

Otherwise i would advise a manuacturer, they will shurely do a lot of testing and have data.

Good luck.

J.H. Brinker thanks for advising. im writing to your recommended and other possible sources to hope get find something to start my work.