Conference Agenda

Assessing the condition of pump stations can be a significant undertaking for many utilities, and the specific approaches and techniques of assessment can vary widely. Among the many working components within the pump station its namesake, the pump, is often a key focus. Significantly reduced capacity or excessive vibration are easily identifiable signs of a failed pump; however, quantifying the specific degradation of an individual pump can be difficult. If accurate quantitative data is available the useful life of a pump can be prolonged by targeted maintenance, and premature rebuild or replacement can be avoided.

Methodology for field testing pumps and the differing approaches in testing both flood control and wastewater pumps will be presented. The technical requirements and constraints and opportunities of instruments and data logging equipment will be reviewed. Some of the common and uncommon insights into centrifugal pump performance, implications for the health of the force main, and specific indicators of wear on various components will be discussed.

Two client case studies will be presented detailing how results from pump testing can be applied to assess equipment condition as well as make predictive maintenance and capital improvement decisions. The City of Spokane, WA, tested pumps at five wastewater pump stations to confirm condition and capacity. Multnomah County Drainage District in Portland, OR, has conducted a variety of condition assessments for its 13 flood control pump stations and has performed testing to confirm the flood control pumping capacities and remaining useful life of most of the pumps it maintains. The specifics of testing wastewater and flood control pumps will be covered, in addition to how the resulting test data, in combination with operational data, can be used to perform targeted rebuilds and prioritize replacements.

With continual improvement of computer processing and software algorithms, there is an ever-growing number of applications for computational fluid dynamics (CFD) to improve the design operation of wastewater treatment facilities. However, the costs of CFD modeling studies are significant, not all applications warrant a detailed study, and some studies are not realistic in addition to being unwarranted.

CFD studies are warranted when 1) their cost can be recovered by savings in capital or operations and maintenance 2) an overall reduction in project risk can be achieved 3) the added benefit of flow visualization warrants the added expense. An example is the utilization of CFD studies for contact tanks. These studies can provide an accurate estimate of baffle factor and result in tanks with smaller footprints than would be allowed using empirical equations or design charts. Reduced footprint size and/or reduced disinfection byproducts justify the cost of CFD studies for contact tanks, storage tanks, settling basins, etc.

CFD studies of pump stations that do not require physical models can be used to evaluate pre-swirl and velocity distribution in the pump throat and develop modifications to improve approach conditions to the pumps. However, CFD has yet to advance to where it can be used to evaluate the potential for vortices or for accurate estimation of turbulence entering the pump. Some consultants and software providers may claim that they can, but buyer beware.

Successful studies require proper application and experienced CFD consultants who can both properly execute a model study and interpret/present the results to design engineers and stakeholders. Attendees will gain an understanding of CFD as a tool that can be useful when properly applied and when the design team understands how close to reality the results are.