Service Life of Steel Wire Suspension Ropes

The life of a suspension rope system depends on a number of factors: the overall maintenance of the ropes in terms of sufficient lubrication and tension, but more importantly the initial system design. An analysis of the EN81-1+A3 (2009) Annex N safety factor equation on four case studies was performed on a number of lifts with 2:1 reeving ratios to determine the minimum and actual safety factors for the suspension rope system. By using equations that are generally used within the wider steel wire rope industry for ropes ‘running over sheaves’, the actual performance of bending cycles was assessed for the four cases studied and converted into an expected number of trips. The paper will show from the case study results that the number of bending cycles performed varied greatly for each lift with exchange periods of between 3.5 and 11 years. The results show that small changes in various parameters will raise the number of bending cycles significantly. The result of adjusting parameters to reduce the tensile load on the ropes, the increase in traction sheave diameter and using a traction sheave groove that reduces fatigue on the rope is to have ropes that will last significantly longer, with a larger number of bending cycles being performed. High use lifts that are reeved at 2:1 or more, especially in low rise applications should consider increasing the suspension rope safety factor in order that reasonable service time is given to reduce costs to the end client.