Old man river keeps falling and falling making it harder and harder to efficiently produce electricity.
A unique floating pump station has solved a major pumping dilemma at the New Madrid Power Plant operated by Associated Electric Cooperative (AECI). Over the past few years, increasingly low water levels at this Missouri facility had presented a major technical dilemma for the utility’s engineers. Lower river levels meant less available cooling water, which led to a reduction in power production. A pumping solution that would maintain the 450,000gpm flow to the two 600MW power units during periods of low river levels needed to be found. Whatever the solution was, it would have to be portable, reliable,easily deployed and and, most importantly, affordable.
AECI’s New Madrid Power Plant is located on the Mississippi River just south (downstream) of the Ohio River. The facility has two intake tunnels feeding water from the river into two independent pump stations, each of which is fitted with dropping vertical turbine pumps providing 200,000 GPM of cooling water per station. When river water levels drop below the level of the intake structure, the pumps begin to cavitate, experiencing excessive vibration and motor amp swings. The 1200-MW coal-based units are AECI’s lowest cost producers. According to a senior engineer witrh AECI, it is critical that these units operate efficiently, as power deratings force the utility to either purchase replacement power from the power marketplace to serve its customers’ needs or shut down the production and face severe financial penalties. Either case is illustrative of the economic importance of maintaining power production. “AECI’s mission is to provide an econimical and reliable power supply and support services to our members”
Over the past several years, river levels have been dropping below the critical point. From 1980 to 1999, there had been only one such occurance-the drought stricken year of 1988. However, each year since 1999 has seen muyltiple below-critical-level occurances, reaching lower and lower levels. Data, including that contained in a recent report by the Army Corps of Engineers, suggest that the new lower river levels at the New Madrid plant may become common and should be expected in the future.
To complicate matters even further, the Mississippi River has a tendency to rise or fall drastically with little warning. River levels can change rapidly over a period of a few days, making AECI engineers as much river-level forecasters as power-generation specialists. AECI’s project engineers admit that can make for some tense situations.They points out that published river forecasts can change drastically due to unforeseen rain upstream or when the Kentucky and Barkley Lake discharges are cut back with no notice. The river has risen as much as 10 feet in a 24-hour period and drop 5 feet in the same period.
Seeking A Solution
Since low water levels had emerged as a real threat to power generation, AECI engineers began to search for a solution to the recurring problem. Initially, temporary pump systems were utilized to serve each immediate crisis, but these temporary systems were not only cumbersome, they were expensive to install and operate. As a long-term solution, complex, time-consuming installation procedures and high operating costs were less than ideal. In an effort to identify a feasible, long-term solution – one that would ensure the New Madrid plant’s ability to remain productive and efficient during periods of low water levels – an extensive engineering study was conducted.
A consulting firm was contracted to study the possibility of intake-structure or pumps-station modifications as viable long-term solutions. A model was built to simulate current and possible future operating conditions. Unfortunately, the conclusions drawn from this study offered no guarantee that modifications to the intake structure or pump station would resolve current and future water supply problems.
Convinced that low water levels were going to be part of any future operation of the New Madrid Power Plant, AECI's engineers continued to search for a practical – and lasting – solution.
The engineers evaluated a number of strategies, even to the point of renting pumps and keeping them on standby in anticipation of lower levels, a very costly proposition. Other alternatives investigated included wet-well modifications, a replacement of the intake structure through the wet-well sumps, a semi-permanent pumping station to augment the existing intake structure, and installation of cooling towers.
After a complete analysis, coupled with site visits, a
Morrison "Floating Solution" pump system was recommended to AECI's engineers. The Floating Solution is a highly portable, complete, floating pump station that can deliver more than 60,000 GPM per pump. For the purposes of the New Madrid Power Plant, it could be staged quickly on the Mississippi River, would require no civil work and, because it would be free-floating, would not be affected by water-level fluctuations. Four units could be coupled together and supply over 200,000 GPM to each intake tunnel. Moreover, in light of their reasonable price, AECI could afford to own these pumps – i.e. purchase, maintain, handle and operate them cost-effectively.
The Mississippi River has A Tendency To Rise Or Fall Dramatically
Each of these independent, self-contained pump stations consists of a high-efficiency axial-flow pump and a diesel-engine driver, fully integrated within a steel frame (equal to an ISO 20-ft. cargo container) and completely self-buoyant. Once afloat, these units can be joined together, thus creating a single, multiple-unit pump station. Its low-velocity intake design allows the Floating Solution to operate in less than 6 feet of water, and the submerged discharge permits clean, attractive and quiet operation. With the sectored model, at the New Madrid facility, each unit could deliver in excess of 57,000 GPM at rated head, making the two four-unit stations compact and stable. To simplify the process even further, these units could be stored in water at a nearby bay until needed.
AECI elected to have eight 42" Floating Solution pump units with Caterpillar diesel engines remain on-site at the New Madrid Plant, ready for staging to the Mississippi River whenever forecasts show that river levels may drop to critical levels. When river levels do drop, the Flowing Solution pump units are put into operation, filling the existing water intake tunnel and supplying full capacity to the vertical cooling pumps. These pumps allow continuous and full-capacity power generation.
All eight of these Floating Solutions, along with discharge piping and accessories, were manufactured and delivered by August last year, less than four months from the time the order was placed.
Within one week of delivery, the first pump was lowered onto the river where it met and/or exceeded all pump-performance specifications.An outside contractor, Specialty Diving of Owensboro, KY, has been engaged to manage these units.
So far, the plant has not experienced river levels low enough to require pumping. Those involved with the project have still been busy. "We have spent the past few months improving the operational set up of the pumps specific to our plant" explains the lead engineer on the project.
When water levels do fall again, AECI's engineers know that with the Floating solutions, they'll be able to keep the New Madrid Power Plant up and running as efficiently as ever. As one of the senior project engineers says, "The addition of these pumps allows us to meet that mission."
The Floating Solution Pump Station
The unique Morrison Floating Solution is designed for continuous and severe-duty applications, yet its versatility and portability are ideal for temporary or emergency high-volume pumping requirements. It brings a fresh, new look to a conventional industry:
With its horizontal shaft, it is highly stable
The pump unit is fully integrated into an all-encompassing frame equal to a 20-foot ISO container
All elements of a complete pump station are contained within the outer frame
Floatation is foolproof as a result of maintenance- and corrosion-free fiberglass shells filled with non-absorbent closed-cell foam
The Floating Solution can be maintained easily. The only true maintenance item is the engine (the unit can be driven by an electric motor), as the transmission and gear reduction is accomplished with a conventional, time-tested belt and pulley design. But the Floating Solution's pulley design is also somewhat revolutionary. It creates no cantilever loads on the driver or pump shafts, reducing the only ill effect related to belt drives – excessive side loads. Once properly tensioned, the belts need only periodic inspection and preventative-maintenance replacement every 4,000 – 5,000 hours.
The pump discharge is submerged, minimizing the static head. Piping is High density Polyethylene (HDPE) – an especially resilient and durable material. This pipe's neutral buoyancy and flexibility allows the Floating Solution pump station to float freely, adjusting to both water-level fluctuations and wave action, while its strong, thick walls ensure unit stability.