How can pump equipment reliability in wastewater treatment plants be measured and improved?
The reliability of pumps is often looked at by the number of failures in a given time as a starting point. This led to the use of the acronym MTBR (mean time between repair), which is an all-encompassing measure of the operating reliability that is typically stated as the average operating calendar time between required repairs for a pump due to malfunction or any other reason.
It includes repairs due to failures, planned maintenance or any other categorization of repair event. The MTBR is a tool for standardizing reporting, monitoring and then putting actions in place to improve the MTBR of the equipment, thereby limiting the downtime or outage of the equipment.
An example of calculating MTBR for a population of 3,000 pumps that has 670 repairs in one year would be calculated as follows:
MTBR = (3,000 pumps) / (670 pump repairs) × 12 months = 53.7 months
A reliability professional could review this against the expected design life of the equipment to determine if improvements could be made to the population. The MTBR is generally improved by implementing programs to review the bad actors within a population.
For example, in the above MTBR calculation, it would be worth knowing the specific units that require more frequent repairs and then further investigating the root cause of those failures. Implementing improvements in procurement, design, maintenance or operation as a result of failure analysis should result in an increasing MTBR number trended over time.
For more information on wastewater pump system reliability, refer to “Wastewater Treatment Plant Pumps: Guidelines for Selection, Application, and Operation” at www.pumps.org/standards.