The most common elevator rope constructions are shown in Figure 11. Many factors determine selection of a rope construction to perform one of the functions in the elevator system. It is best to follow the recommendation of the elevator manufacturer when replacing rope. In fact, replacement of governor ropes must conform to rules specified in ASME/ANSI National Standard A17, Safety Code for Elevators and Escalators.
Almost all rope furnished for elevator service contains a hard fiber core developed specifically for this application. Rope with independent wire rope core (IWRC) is used in some applications.
Elevator rope is furnished primarily in right regular lay and right Lang lay.
Elevator rope is produced in three basic grades:
Traction- traction, is the most common grade of elevator rope, is primarily used for hoist ropes which require a blend of ductility and strength.
Extra Height Strength Traction-extra high strength traction is primarily used where high speed or great height require a higher nominal breaking strength hoist rope. It may also perform better in more abrasive V-type groove applications.
Iron-iron is primarily used for elevator applications other than hoist rope.
From reel to reel, there are slight yet significant differences in the elastic stretch characteristics of wire rope. Because of such possible variations, it is strongly suggested that all rope for a given elevator be obtained from a single reel. Recognizing the need for such precaution, many codes and purchasing specifications make this a standard requirement.
As noted, it is beyond the scope of this publication to discuss, in depth, design and selection considerations for elevator rope. Information concerning sheave diameters, design factors (ratio of nominal strength to working load), groove contours, socketing and inspection can be found in the ASME/ANSI Code A17.
Compacted Strand Wire Rope
Compacted strand wire rope is a wire rope manufactured from strands, which have been compacted or reduced in diameter prior to laying strands around the core into a finished wire rope. There are various known methods for compacting; drawing the strand through a compacting die, roller reduction and rotary swaging are several examples. The compacting process flattens the surface of the outer wires and reforms internal wires of the strand to increase the metallic area of the strand. The result is a smoother bearing surface at the strand crowns and an increase in nominal strength over round strand rope of the same diameter and classification. Cross section diagrams of rope with compacted strands are found in Figure12.
Compacted strand rope strengths are commonly available in 6-strand rotation resistant rope. For information on the exact nominal strength available on particular rope, consult the manufacturer of the rope.
Compacted (Swaged) Wire Rope
The entire cross section of a rope is compacted or reduced in diameter following laying strands around the IWC to produce compacted or swaged wire rope. Rotary swaging is the most common process for compacted rope although other processes may be used. As illustrated in Figure 13 the wires and strands of the rope are flattened to produce a relatively smooth and wear resistant outer surface. Compacted rope generally has good wear resistance, crushing resistance and high strength; however, the compacting process may reduce bending fatigue life.
Flattened (Triangular) Strand Wire Rope
Flattened strand comprises a layer or layers of wire around a triangular shaped center. The center consists of either a triangular shaped wire element or wires in a triangular configuration. The triangular strand shape provides a high strength rope with high metallic areas, which is resistant to crushing. Abrasion resistance is enhanced by an increased bearing surface in comparison to round strand ropes. Various flattened strand constructions are illustrated in the figure below.
Plastic Coated Wire Rope
Various wire rope constructions are available with plastic coating applied to the exterior of the rope. Small diameter galvanized and stainless steel wire ropes with plastic coating are common. The plastic coating can provide protection against corrosion and in some cases reduce wear of the rope and other rigging components. Plastic coated ropes can be difficult to inspect. Nominal strengths for plastic coated ropes are based on the diameter and grade of the rope prior to coating.
Plastic Filled Wire Rope
Plastic filled wire ropes are wire ropes in which internal spaces are filled with a matrix of plastic. The plastic extends to, or slightly beyond, the outer circumference of the rope. Plastic filling may improve bending fatigue life by reducing internal and external wear. Nominal strengths for plastic filled ropes are based on the diameter and grade of the rope prior to plastic filling.
Plastic Coated IWRC Wire Rope
Plastic coated IWRC wire rope is wire rope, which incorporates a plastic coated, or plastic filled IWRC. The plastic coated or plastic filled IWRC reduces internal wear and may increase bending fatigue life. Nominal strengths for plastic coated and plastic filled ropes are based on the diameter and grade of the rope with an uncoated or unfilled IWRC.
Other Special Constructions
Specail Purpose Constructions
Table 2: Specail Constructions
|3x7||Guard Rail Rope|
|6x42||(6x6x7) Tiller Rope|
|Unit Lay||Parallel Lay|