Abstract
Maintenance costs have risen steadily over recent years in proportion to total investment in thermal power stations, however lack of regular maintenance can result in serious equipment failure with catastrophic consequences. In general, the Nigerian power generation capability has nosedived to an abysmal level, particularly at the generation stations due to poor maintenance culture. This paper evaluated maintainability of steam and gas turbines components in a thermal power station. Data were obtained from a thermal power station in Nigeria; these raw data were extracted from the operation department, which represents records of plant generation capabilities as well as other inherent daily conditions that will enhance the success of this study. Various maintainability measures were used in analyzing the data, the study implemented log normal distribution considering that most turbines fails due to fatigue and other phenomenon that are caused by ageing or wear resulting in failure rates that increase with time. The estimated mean time to failure of turbine 2 reduced from 35744.5 hours to 33643.8 hours after the use of a condition based preventive maintenance policy. Mean Preventive Maintenance Time (MPMT) for Economizer Inlet non Return Valve and its effect on steam turbine 1 ranges from 77144hrs to 4296hrs for gas turbine 2. The station overall mean maintenance time showed that steam turbine 1 has a maximum hours (77144hrs), while its is minimum for gas turbine2 (4296 hrs). MPMT of sub-equipment is maximum up to 48717 hrs on Gear defect/Hood diaphragm for steam turbine 2; also maximum for the Economizer Inlet non Return Valve, while this was minimum about 48708 hrs for the water pump. For gas turbine 2 MPMT hours for seal leakages and air filters have a maximum value of about 4295.5 hrs, while it is very low on other equipment. The equipment maximum corrective maintenance time (MCMT) of various turbines is higher for steam turbine 2 (10.04 hrs), while minimum for gas turbine 2 (10.00 hrs). Conclusively, planned maintenance tasks can reduce the number of unplanned or emergency trips of these turbines.
Highlights
In the past, the maintenance practices of Nigerian industries has been learned through experience and rarely examined analytically
The total time of maintenance considering both corrective and preventive maintenance task is in the range of 4295.3-77141 hrs
Various measures used in maintainability analysis were adopted in evaluation of steam and gas turbines components in a thermal power station
Summary
The maintenance practices of Nigerian industries has been learned through experience and rarely examined analytically. Increased performance requirements have led to complex maintenance needs which necessitates adoption of more engineered decision support for maintenance of equipments. A lot of investment has been channelled to power generation process and automation to enhance the reliability of this systems, this requires adequate maintenance. Maintenance of process instruments and equipment play a major role in the smooth running of such process [1; 2]. Effective maintenance of turbines are obviously one of the most important aspects of modern thermal power station. Since the dawn of industrialization, people who were experts in maintenance, repairing, and diagnosing machines were entirely invaluable. Maintainability is defined as the probability of performing a successful repair action within a given time. The repair rate is a random variable since it is dependent on the nature of failure, ability to analyze the root cause of failure and expert human resources to carry out the
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