Identifying a Mathematical Model to Optimize Pump Maintenance Planning Decisions - A Case of Irrigation Asset Management in K.S.A

Abstract

With increasing investments being made by the Provincial Government in KSA's Eastern Province on irrigation water distribution projects, more focus is being placed on finding ways to reduce expenditure and restore the lost performance of irrigation assets due to planned or un-planned overhauls. This article presents a modeling approach to improve the repair schedule at the local water pump stations with an aim of minimizing total life-cycle cost of the pumps while maintaining eco-friendly standards. The case study used focuses on a Sanitary Wastewater Treatment Plant (SWTP) having centrifugal pumps running in parallel configuration to pump water from tanks to service reservoir. The opted methodology considers a realistic set of assumptions with the type of data available to identify four main parameters for maintenance decisions- the Hydraulic Model, Operation Model, Deterioration Model and Optimization Model. A hydraulic mode for the pumping system has been defined with performance measures like head-flow, power-flow and system curves and is used to compliment the deterioration model, which predicts the drop in pump performance with continuous use. Operational inputs such as the production schedules, pump schedules, duty specification, hydraulic output etc. are combined with deterioration mechanisms, namely the wear ring and internal surface deterioration, to identify an optimization model- an optimal pump overhaul schedule. While the hydraulic model is explained numerically using equations to approximate solutions, the optimization model is discussed as a linear integer programming problem using heuristics. Mathematically computed solutions to the models are finally applied to a system of three pump stations to forecast an appropriate number of overhauls for each pump station over the next four years with the subsequent costing involved. Thus, the described approach serves as a model-based decision support system tool (DSS) to assist planning engineers and asset maintenance managers in crucial pump overhaul planning and budgeting decisions.