A New Technique for Evaluating Disassembly and Maintenance Using an Example of Underground Escalator

Abstract

Few products are designed for disassembly or easy dismantling. As manufacturers recognize their responsibility for products at the end of their operational lives, the dismantling of products has emerged as a serious consideration in manufacturing. Disassembly is generally achieved by taking apart individual components or subassemblies of a large product. In situations involving integrated design principles, certain assembly procedures or joining techniques can make the disassembly of a product and separation of components into useful and non-useful groups very difficult. Designers are becoming steadily aware of the problem, and are employing techniques that allow them to design with greater responsibility - Design for Disassembly (DFD) is such techniques. In the case of a durable good with a long life cycle or a product with parts subject to wear, maintainability/serviceability may be more important than initial product acquisition cost, and the product must be designed for easy maintenance. The DFD principles identify the ease with which products can be fabricated, maintained, serviced, and recycled. This paper examines a special case of evaluation of escalator housing using DFD method. Escalator system plays an important role in transporting passengers safely between underground and station platforms. However, due to the complex working conditions such as uneven load, extreme weather etc. of the escalator system, maintenance is constantly needed and unexpected failure and repair also happens frequently. The escalators used in train subway/metro stations are exposed to some extreme operating conditions such as extreme weather/temperature, uneven loads and shock etc. that can greatly shorten their life span. The increase to labor and maintenance cost impedes the escalator’s ability to efficiently serve its riders and affects its overall stability. The failure and repair of the escalator systems take a significant amount of labor and cost, in addition to customer dissatisfactions. This paper examines and identifies different types of failure modes and defects that occur in the major components of escalator drive systems, such as the motor and its drive chain system, handrail and its drive system, bearings/lubrication systems that are in adjunct with the bearing shaft assembly. The normal maintenance and repair of these sub systems is time consuming. For evaluating the design of the in the escalator, a new approach involving Rating Chart is used. This paper examines various existing DFD techniques and compares them with the Rating Chart method to evaluate DFD efficiency. The paper concludes by showing the robustness of the new DFD methodology in an environment where the products are exposed to extreme working conditions.