Fourth generation maintenance philosophy and Quality management system 9001:2015, emphasis on the concept of risk based thinking. And it is one of the challenging part of maintenance department to adopt these philosophy by quantifying all the activities of the department. Risk rating based on reliability is one of the techniques to quantify the maintenance activities for those organizations, whose reliability of goods and services matter in the market. Hydropower sector is also among them whose reliability matters highly in consumer life standard. So this paper approaches to rate the risk of hydropower based on the reliability of components for the implementation of Risk-based maintenance. From the study of data recorded in log book of a small hydropower plant located in western part of Nepal, it was found that the overall reliability score of the plant was 0.9819, which was low as compared to other hydropower of Nepal, where turbine section of both the units of the plant found a higher risk score than other systems. Study adopted two tools i.e. Analytical Hierarchical based Fault Tree Analysis and Critical Analysis Technique to find the critical assets and Failure Mode and Effect Analysis for the rest of all to quantifying the risk in component level. The analysis shows that the cooling system as the critical asset for both the units and it contributes 72% and 64% in the reliability of the turbine section. The critical assets thus obtained was validated through the critical analysis technique. From which the risk score of cooling system found 90% in both the units. To analyze the risk in component level, Failure Mode and Effect Analysis of different sub component of critical assets was done. Among the sub-components of the cooling system, radial tube filter gets the highest risk score. Its components; cartridge, tube, and joints have the risk score of 450, 192, and 96 respectively. And from the critical analysis of the rest of the subsystems of uint-I and unit-II, components such as bearings, breaker of the transmission system, transmission equipment, excitation system and transformer of unit-I and breaker of the transmission system, transmission equipment and excitation system of unit-II are found to have higher critical score, hence, it is recommended to apply preventive activities on these components as per the manufacturer to reduce the risk that could be caused by their failure.

Detailed engineering geological study is one of the basic requirement for the underground excavation and other infrastructural development works in the geotectonically active part of the Himalaya. Geological investigation directly relates with the sub-surface condition of rock and soil and their engineering properties. Underground excavation and construction of hydropower tunnels, dams, roads, irrigation canal and all foundation works without proper understanding of engineering geological parameters will not meet the requirements to design any safe, efficient and cost-effective infrastructure on and under the earth. In the Modi Khola Hydroelectric Project, a sound approach on geological condition is considered during construction. This paper deals with the details of the construction phase engineering geological study. It also explains the various geotechnical and geological study done to decide the Tunnel alignments and foundation of various structures in the project. As a result of study, previously designed structures and location of the Surge Tank and Penstock fixed at loose terrace and conglomerate deposit were shifted on the bedrock by designing a 40 m high vertical shaft and about 445 m long pressure tunnel. Previously designed long and curved tunnel alignment from vertical shaft is changed by a straight and better alternative alignment to reduce the tunnel length by about 35m. Similarly, detail geotechnical study of rock in the tunnel have direct impact on support design. Using the maximum advantage of self-supporting capacity of rocks, a big amount of cost in tunnel is also reduced by designing the tunnel support system based on Q-value of rocks. All such changes have provided safety to the project and also made more cost-effective.

Reliability engineering is emerging field which provides a tools to ensure the system is capable to deliver reliable product and service to the customer. Electricity is one of the most important human needs in this modern age. So reliability of such facilities plays important role in the quality of life and the economy of the county. Hydropower is one of the main source of energy in Nepal, whose reliability plays important role to successful transaction of traditional fuel to electricity to ensure the targeted energy consumption by government of Nepal in fifteenth five year plan. So this paper foster the way of improving the reliability of hydropower plant to ensure the reliability of power supply in National grid. As the study carried out in Bijayapur-I small Hydropower plant, the reliability and availability found as 0.876 and 0.793 only and insufficient flow seems the major contribution to decrease reliability as scheduled outage, whereby problem in turbine section plays important role to reduce the reliability in the electromechanical system of the plant whose contribution in reliability and availability is 79% so any failure in turbine section adversely affects the performance of plant. Due to this the maintenance strategy should be focused on turbine section. And the study recommended to increase the frequency of flushing of radial filter of cooling system, redundancy in filter system can increase the reliability, use of cyclone separator to separate the dissolved limestone and dissolved sand is the another option, and to use close loop cooling system instead of open system.