Lift Report

The service life of steel wire ropes in traction sheave elevators is affected by a variety of factors. In all applications in which ropes travel over pulleys, they are subject to tensile and compressive stress which results in material fatigue and in wear of the wires, both on the surface of the rope and also internally. For technical reasons, other application-specific loads are also applicable in traction sheave elevators which exacerbate the reduction of rope service life. These additional life-affecting factors include rope slip, high compressive stress in the shaped grooves of traction sheaves and changing ovalization of ropes.

As elevator systems undergo ever more sophisticated further development and cost pressures become increasingly pronounced, elevator dimensions are continuously pushing out the boundaries of technical feasibility. Alongside aspects such as weight saving and reduction of the necessary design volume, and importantly also the debate surrounding the energy efficiency of elevator installations, from the viewpoint of the rope manufacturer any such changes are bound to prompt a complex analysis of possible consequences.

Passenger service level in an elevator system depends on the group control and cannot be calculated directly. With conventional control, waiting times and interval have a correlation in up-peak. With a destination control system (DC), interval and waiting times do not have a similar correlation as with conventional full collective control. Therefore, simulation has become important in determining passenger waiting times with DC. Passenger arrivals follow a Poisson distribution, and simulation results vary depending on the random seed number of the simulation. In this article, different simulation procedures and consistency of the simulation results are studied.

The mechanical characteristics of suspension ropes used in traction sheave lifts are required to comply with ever more stringent mechanical requirements, due partly to the height of modern buildings and consequent increases in the required vertical rise. An important aspect here is rope elongation under load, and consequently the spring rate of the elevator car during operation and during loading and unloading. In order to describe these spring rates, the rope elongation module must be known relative to safety factors typical for the elevator in question. This is particularly significant, given that the rope stresselongation curve is non-linear in shape and the rope elongation module is not constant.

The new STX Family track ropes were designed by Pfeifer Drako especially for elevators using smaller traction sheaves. With diameters of just four to five millimeters, the ropes are integral to a comprehensive system that enables thin ropes to be used safely in traction sheave elevators outside established standards. The elevator rope specialists will be presenting the innovation at this year’s Interlift in Augsburg, Germany, 13 to 16 October.