Traction wire rope is an important suspension device of household elevator. It bears all the weight of car and counterweight, and drives the car to rise and fall by relying on the friction of traction wheel groove. During the operation of household elevator, the traction steel wire rope will bend unidirectionally or alternately around the traction wheel, guide wheel or reverse rope wheel, which will produce tensile stress. Therefore, the traction wire rope is required to have high strength and wear resistance, and its tensile strength, elongation and flexibility shall comply with the provisions of gb8903. It is precisely because the damage degree and bearing capacity of traction wire rope are directly related to the safety of human life and property. How to carry out correct periodic inspection and lubrication maintenance is particularly critical in the process of use.
1、 Types and specifications of steel wire ropes for household elevators
The steel wire rope of household elevator is generally a circular strand structure, which is mainly composed of steel wire, rope strand and rope core. Steel wire is the basic component of steel wire rope, which requires high strength and toughness. Steel wire rope strands are twisted by steel wires, generally 6-8 strands. The rope core is usually made of synthetic fibers of sisal or olefins.
2、 Factors affecting the service life of steel wire rope
1. External factors
Tensile load, radius of curvature, groove type, traction wheel groove material, corrosion, etc.
2. Internal factors
Performance of steel wire, diameter of steel wire, twisting type of steel wire, etc.
3、 Scrapping standard of steel wire rope
The service life of steel wire rope on traction wheel will be limited by wear and alternating stress of steel wire. In most cases, the replacement should be determined as long as obvious steel wire breakage is observed on the outside.
In order to ensure the normal operation of the household elevator, the main criterion for scrapping the steel wire rope is to check the number of visible steel wire breaks on a pre selected length, and the inspection length is 6D or 30d (d steel wire rope diameter). When the visible broken wire of the steel wire rope exceeds the specified number, it must be replaced.
For 6-strand and 8-strand wire ropes, wire breakage mainly occurs on the surface. The wire rope with multi-layer strands is different. Most of the broken wires of this kind of wire rope occur inside, so it is an "invisible" fracture. In addition, when the wire rope is broken at the end of the rope and the broken wire is locally concentrated, it shall also be considered to be scrapped. When the diameter of the steel wire rope is reduced by more than 7% relative to the nominal diameter, the steel wire rope shall be scrapped even if no broken wire is found.