Lift Report

The conference was headlined “Innovative Ropes and Accessories – A Demonstration of 175 Years of Wire Rope”. All the world’s rope professionals had been invited to attend. The subjects explored by 19 internationally renowned lecturers during the two days of the conference required a great deal of concentration on the part of the lecturers, the interpreters and the listeners. Any unanswered questions could be aired in a panel discussion at the end of each day.

In so far as they are especially relevant to the field of elevators, the speeches delivered in English will be published in Lift- Report and translated.

In his role as the conference initiator and director Prof. K. H. Wehking, CEO of ift Stuttgart, opened the meeting and greeted the participants, who came from 29 countries. In memory of the victims of the killing spree that had taken place shortly before in Winnenden (near Stutt- gart), the audience rose for a minute of silence.

Prof. Wolfram Ressel, President of the University of Stuttgart, greeted the participants on behalf of the University, introducing the university itself and the fields of activity pursued by the ift within the academic community. To be emphasized here in particular is that more than half of the financing for the work of the seventy ift employees is by way of thirdparty funding. Research and technical development are closely linked and particularly successful, are recognized both inside and outside Germany. Eight endowed professorships are the result.

Prof. Wehking, as director of the ift and member of the University Executive Board, delved further into the institute’s activity. He thanked the employees involved in the organization and conduct of the conference for their excellent work, which had been significant for the success of the event.

The ift was founded in 1927 and in the person of Prof. Richard Woernle had an outstanding scientist as its first director. The directors who followed were named and particular attention was drawn to the achievements of Prof. Klaus Feyrer, a pioneer in the field of rope bending and service life. His findings have been cited in international professional literature and have found worldwide acclaim.

Further assignments were mentioned and it was possible to document new findings in regard to the dependency of multi-layer rope designs. The results of additional basic research were mentioned such as, for instance, successful work on magnetic-inductive rope testing. It has been possible to translate the development results into practice and today automatic evaluation of bridge suspension cables and the fixed track ropes in aerial trams can be carried out at speeds of from 0.1 to 3.0 m/s. Information was also provided in regard to successful examinations of rope terminal connectors. Another item mentioned was the testing of cables specially engineered for offshore use at depths of up to 3,000 m. It was also possible to conduct successful examinations of the ropes, up to 128 mm in diameter, used on transport ships. Information about the behavior of the interior layers in rope has been insufficient and could be augmented with the help of finite element analysis. Additional work included and includes topics on high-strength fiber ropes, elevator ropes, ropes for high-rise warehouses etc.

A commission to examine hybrid designs was awarded in December 2008. Five professors are involved in conducting this study at the University of Stuttgart.

Also in progress are examinations in regard to new materials to be used in rope applications and, finally, investigations on adaptive shell structures. Sensors are used to detect changes in wind and snow loads and the resultant forces on the ropes and their supports are monitored.

As the co-sponsor for the event and President of the OIPEEC, Roland Verreet introduced that organization. Today it has 151 active members in 30 countries and devotes itself to the manufacture and use of ropes. The make-up of the Executive Board and the Management Committee was outlined. German interests are represented by Prof. Klaus Feyrer and Prof. K. H. Wehking.

With the conclusion of this introduction and explanation of the ift’s work Prof. Wehking declared the professional part of the conference to be opened and asked the first speaker to present his lecture.

The wide range of subjects covered made it necessary to subdivide discussion into six topical groups where the presentations prepared by 42 authors were delivered by 21 speakers. Unfortunately it is impossible to discuss the subject matter in detail within the scope of this report. As was previously mentioned, speeches relevant to elevator industry or of interest for rope technology in general will be reprinted in Lift-Report.

The following sessions were arranged for:

Session 1-  Rope history

Session 2 - News and innovations in rope production and rope applications

Session 3 - Dimensioning of rope drives and rope endurance calculation

Session 4 - Ropes in traction applications, rope terminations

Session 5 - Fatigue behavior and discard criteria for wire ropes

Session 6 - Non-destructive testing, finite element analysis, deterioration and damage mechanisms for wire ropes

A selection of topics discussed rather more extensively in the lectures is mentioned below in order to indicate the variety of problems associated with wire rope, the suspension means that was first put to use to bear a pedestrian bridge 50 cm wide over the River Rhone in the year 1822. The first suspension bridge had been built in Wales in 1808 and employed chains to carry the traffic surface. The thought of braiding wire came from the USA and England and various designs were introduced. In addition to use as a stationary load-bearing rope, there was increasing demand for hauling ropes used in conveyance operations such as mining and elevators. Since 1986 efforts have been undertaken to examine adopt plastics for ropes made of synthetic fibers or in combination with steel wires or strands in the form of a so-called fl at belt. Examinations on the further development of this use of plastics are being pursued at a number of institutes and the terminations for the ropes are the subject of special studies.

A report was delivered on a study focusing on the usefulness and uses of steel ropes made of stainless steel. How to determine the appropriate rope design was discussed, as were the special requirements associated with their use. Among these applications are use with lift winches for rescue helicopters (here the ropes have to be twist-resistant) or blackened ropes (19 x 7) for use on the theatrical stage, etc.

The application ranges for plastic ropes made of HMPE were discussed. These include marine tugs, drilling platforms and continuous loop belts. A particular advantage is that these ropes are virtually weightless in water, making them excellent for use in offshore technology at great depths. The stretch properties are identical to those of steel wire ropes and, what’s more, they are corrosion resistant.

The new findings generated at the ift in regard to the use of thin wire ropes (e.g. 4 mm diameter) in elevator construction were discussed. See also the Lift-Report article covering the 2009 Heilbronn Lift Conference. The increase in plastic rope use is also shown in the examination of use in multi-layer drum drives. In offshore operations, for example, ropes of up to 100 mm in diameter are used and the forces thus imposed on the drums have induced fissures and fracturing in the drum’s shell. The stiffness of the rope has an influence and a number of studies are now examining the behavior of the various rope designs, the idea being to achieve the most favorable D/d ratio. Ships offer only a limited amount of space for the drums and the diverter sheaves needed to lay ropes in deep waters.

Other investigations carried out at the various testing institutes around the world show that the discard time, the terminal connectors, the freedom from torsion effects, the bending properties and the influence of the rope design are subjects of ongoing interest since the further development of the materials quality and the manufacturing process necessitate continuous observation of the consequences. Here reliable determination of the service life and associated factors and dependable calculation procedures are indispensible components in our store of technical knowledge.

A report on the results of the investigations into the reasons behind the aerial tramway accident at Schilthorn Peak in Switzerland, on December 29, 2004, was given. All the trams using this rope design have been examined. The cause for the outside wires breaking was determined to be welding work carried out near the rope during repairs on the towers. De-icing procedures could also cause damage that is initially not visible. And, in general, damage due to lightning striking the rope systems (track ropes, hauling ropes) used for tramways cannot be excluded.

Also reported on was the damage at a mine pit conveyance unit in South Africa.

The specifications for this drum-type unit with 4-layer winding were: shaft depth 2,043 m; 2 drum drives with one drum each, drum diameter 4,270 mm; rope diameters 2 x 45 mm; carrying capacity 10.25 t; operating speed 15 m/s; weight of each of the round strand ropes 9.8 t.

The calculated number of trips came to 165,000 cycles but the system only achieved 38,000 cycles. The ropes were replaced with closed fl at-strand ropes, 2,500 meters long and 42 mm in diameter.

A description of the fi nite element method, a technique currently being used in any number of research projects, demonstrated the opportunities it offers, particularly in evaluating the fl at elements used in load-bearing structures. When this method is used one can essentially dispense with any assumptions and presumptions since the results are both unequivocal and reliable. It was noted that the calculations with 51 degrees of freedom for surfaces and 6 degrees of freedom for beams require a great amount of computing power and consume considerable amounts of time.

The next event, which will once again be a joint effort by ift and OIPEEC, is scheduled to take place from March 22 to 27, 2001, in Las Vegas.