Reliability modelling and performance analyses of an LHD system in mining

Coal mining in India has a history of over 225 years. The industry currently occupies a covetable third ranking in the world league table of hard coal production after China and the USA. Mechanization has made possible major breakthroughs in coal mining technology. The record of production and productivity of Indian underground coal mines over the years is dismal, to say the least. At the time of nationalization (1971) of the coal industry contribution of national coal production by underground and opencast mines was 77.4% and 22.5% respectively. By 2000, the share of coal production from opencast mines increased to 78.65% and from underground mines declined to 21.35%. The share of coal production by different methods may be stated thus: bord and pillar (conventional)—55.98%; mechanized (SDL/LHD)—34.01%; longwall (conventional)—0.6%; mechanized 7.44% and other methods 1.97%. Daily production in blasting gallery panel with an LHD is about 800 t. An average ton per day per machine (LHD capacity-3.5 m3) is about 1501. The mechanization trend in the bord and pillar method of coal mining introduced sophisticated automated side discharge loader (SDL) / load haul dumper (LHD) machines for loading of coal in place of manual loading. Among the face loading machines, the electric LHD is now the dominant machine in intermediate technology and plays an important role in district or overall mine production. To achieve targeted coal production and to survive the intense competition in the mining industry in recent years, it is imperative that an LHD machine as a system and its subsystems should be reliable and maintained effectively and efficiently to ensure its maximized availability. Reliability assessments of repairable machines have been explored in some papers2–9 . The basic methodology for reliability modelling to analyse the failure characteristics of a repairable machine is presented by Ascher et al.2 and Samanta et al. (2001(a,b) and 2002). Failures of a repairable machine have been modelled on the basis of a renewal process3–7,a homogenous or a nonhomogenous Poisson Process (NHPP)2–6,8, or a proportional hazard process9. In the renewal process, the time between failures(TBF) are assumed to be independent and identically distributed (iid) and failure data are characterized for modelling by a suitable probability distribution function. NHPP or the power law process is a time-dependent model. In the homogenous Poisson Process, TBFs are assumed to be exponentially distributed or have a constant failure rate. In this paper, the reliability as well as maintainability analysis of mining machines, based on the Markov process, has been proposed. In real life, failure of LHD subsystems are Reliability modelling and performance analyses of an LHD system in mining