Abstract:
Kenya Electricity Generating Company Ltd (KenGen) is the leading power generator in Kenya, producing 69% of the electricity
from hydro, geothermal, thermal and wind sources. Geothermal is an abundant resource in the Kenyan rift with KenGen Olkaria
field being the largest commercial geothermal project in Africa. However, the lack of adequate and affordable energy in Kenya
remains a significant constraint to economic growth, thus, the government of Kenya seeks to accelerate geothermal energy
exploration. Drilling accounts for the highest portion of geothermal energy exploration costs. Random equipment failures, high rate
of wear and tear, and outright design failures on drilling rig equipment are critical contributors in rendering geothermal drilling a
costly exercise. To address these challenges, maintenance is vital to ensure equipment operability, reduced failures and ultimately
low maintenance costs. Due to the numerous equipment in an installation, the identification of the critical equipment and
subsequent selection of the appropriate maintenance policy to be employed to mitigate its failures is paramount. In this paper, we
propose risk assessment techniques that can be applied to structure equipment failure, assess and prioritize failure impact using
Pareto analysis to firstly identify critical subsystem and critical equipment under the subsystem, secondly, undertake root cause
analysis for the failures on critical equipment and eventually select the most feasible maintenance policies to address the root
causes.
The developed methodology is validated using data collected from two Olkaria drilling rigs, where the results show that the top
drive and drawworks are the most critical rig subsystems. Furthermore, robotics and electrical controls are the critical equipment
under top drive subsystem, while the clutch and brake under drawworks subsystem. The leading causes of rig equipment failure
were machine-related wear and tear, overheating and hitting by moving members. Other causes were wrong designs, bad
workmanship and poorly translated of manuals. The recommended maintenance actions for the policy framework were Time-based
maintenance (TBM), Condition-based maintenance (CBM) and Design out maintenance (DOM) complemented with close
supervision of personnel, retraining of staff, the proper translation of manuals and framework contracting for the supply of spare
parts.
