Replacement of wastewater equipment is usually assumed to be a function of its structural and mechanical condition. Often, age is the sole criteria for replacement, which may lead to non-optimum replacement schedules when equipment is otherwise in sound condition and performing adequately. Conversely, equipment in severe service may require replacement well before a standard service life expectation has been reached because its condition may degrade rapidly. In addition to the ability of the equipment to operate (its condition), replacement must also take into account performance factors such as capacity relative to demand, reliability in service, operator and public safety, technological obsolescence, and the cost of operation and maintenance. Managers rarely have the data at their fingertips to make optimum replacement decisions taking all the above factors into account. Recognizing this need, the County of Maui engaged Brown and Caldwell to develop a tool to help capital and maintenance program managers make the decision to replace or renew equipment using a formalized assessment of both condition and performance. This tool is assisting the County to develop an equipment replacement schedule as required under a Consent Decree from the USEPA. Condition and performance grades are assigned by reviewing maintenance history, capacity relative to design and demand projections, safety standards, customer and regulatory agency expectations, the availability of spare parts, O&M costs, and other factors. The tool uses grades assigned by the user, the age of the equipment, standard industry expectation of service life adjusted by actuarial expectations, and the percentage of time the equipment is actually operating to compute the remaining useful life of specific equipment items. The computed schedule of replacement or major renewal is displayed for all items assessed.
Equipment Replacement Decision Support Tool
Authors: Raymond N. Matasci, Steve Merrill, Michael Ratte, Alan Souza