The use of small steel wire ropes in traction sheave elevators
Higher, faster, further or, as the trend in the elevator construction business goes: smaller, thinner and lighter. Growing pressure on costs and a tougher competitive environment have led variously to technical solutions that are shaped solely by cost optimisation parameters. Yet amid all these cost-capping discussions, we should never ignore safety and reliability requirements - especially with traction sheave elevators which are of such safety-related and public-interest concern. The machine element steel wire rope is the core element in any elevator system, affecting performance characteristics and system costs. Smaller ropes, with the same diameter ratio of traction sheave to steel wire rope, D/d, lead to smaller guide sheaves and smaller drive units with lower (cost determining) output torques. However, smaller sheave diameters also permit smaller installation space and, consequently, reduced head room. Larger cabin floor areas are possible. But what about safety-related requirements when the steel wire rope is running, which are: service life and the point of wire rope discard? At Interlift 2007, Pfeifer DRAKO Drahtseilwerk GmbH presented small steel wire ropes from the STX series with nominal diameters of d = 4 mm and d = 5 mm that have been issued with product type test certificates by TÜV Süd, Germany. This certification applies to elevator systems using traction sheaves with V-grooves of ?? = 40° to ?? = 50° and guide sheaves with round grooves and a diameter ratio D/d = 40. In a further development, however, and for the above-mentioned reasons of cost, space requirement and useable cabin floor area, the sheave diameter ratios were reduced to D/d = 30. The following paper is a report about extensive development work on small steel wire ropes with rope diameter d = 4 mm, ropes deployed with V-grooves (D/d = 40) and guide sheaves (D/d = 30). Our development work always reflects “system thinking” - which means de facto that the rope manufacturer no longer delivers just the rope but additionally provides the elevator manufacturer and/or the distributor with a components and methods service in order to make these advanced and future-ready small steel wire ropes a safer and reliable system element.