Analysis of the Impact of Unscheduled Downtimes on their Availability in Machine Operations

Abstract

Unscheduled downtimes in machine operation are one of the main reasons behind their low availability. Such downtimes are caused by miscellaneous factors and remain difficult to identify in a number of cases. This particularly refers to enterprises that conduct their activities in changing external conditions, such as hard coal mines, where exploitation is carried out in extremely complicated, changeable and dangerous conditions. The process of coal production makes use of various machines that must be adapted to these conditions. The specificity of the working environment makes it necessary for these machines to exhibit high reliability, readiness and efficiency. These features, in turn, make the cost of the machines very high. It is therefore reasonable to make the best use of their capabilities, which translates into the effectiveness of the entire production process. The article concentrates on determining the availability of these machines. It has been assumed that availability is one of the fundamental parameters that define the effective utilisation of machines. The tests were conducted for a longwall shearer as well as an armoured face conveyor and a main haulage conveyor in one of the hard coal mines in Poland. Industrial automation systems were used to determine unscheduled downtimes in the operation of these machines, as well as their time structure and causes. The results obtained indicate that the number of unscheduled downtimes represents a serious problem in mining exploitation.