The City of Houston has selected planning, engineering and program management firm Lockwood, Andrews & Newnam Inc. (LAN) to develop...
It is never an ideal situation to have to bypass a pump station or a process in a treatment plant. However, the bypass that is a planned portion of an upgrade or rehabilitation is always more welcome than that middle-of-the-night emergency. There are several ways to make planned bypass events easier to deal with and more cost-effective with a little “outside-of-the-box” thinking. One strategy that is becoming more popular is the use of an electric drive bypass pumpset in place of a diesel drive pumpset.
The first advantage to using an electric drive pump as opposed to a diesel driven pumpset in a planned bypass operation is that there is no fuel to purchase. Obviously this cost depends on the size of the bypass and the number of times the pumpset will cycle during a typical day; however, considering current diesel prices, fuel is always a large factor during a job. This also means no checking fuel levels over a holiday or weekend when a contractor would charge a premium for his labor force. Additionally, there are no environmental concerns regarding fuel spills that require the purchase of fuel berms. Finally, in many remote stations there are logistical challenges to simply getting fuel to
a temporary pumpset.
The second advantage is noise reduction. Often there are noise ordinances at the site that are strictly enforced. Furthermore, a noisy pump gets the attention of delinquent passersby looking for things to break or turn off. While there has been progress in reducing the noise of a diesel driven pump, and the noise-reducing canopy also offers the security of locking doors, there is a cost associated with all the technology. An electric drive pumpset is just as quiet as the pumps that are permanently installed in the station. It draws no attention and requires no large canopy to appease neighbors
of the station.
A third advantage of electric motors is that less service is required. If the pump station requires a temporary diesel driven pumpset to cycle often, or the pumpset runs constantly, there are costs associated beyond fuel. Most suppliers require their diesel engines to be serviced every 250 hours. During a 24-hour run application, that equates to service every 10 days. If the organization renting the bypass does not have the expertise or manpower to perform the service, then in addition to the cost of filters and fluids, one must add the cost of hiring a supplier’s mechanic every 10 days or so. Even if the bypass is the responsibility of a contractor, that cost will be passed back to the owner at some point. Electric motors can run constantly without any service requirement.
While there are many advantages to using an electric pumpset during planned rehab on a station, it is not practical for every situation. An electric pumpset is most effective during a long-term bypass because the cost of an electrician for installation would offset the other associated costs for only one or two days at most. Also, the electric pumpset is most advantageous when the correct power voltage and amperage is on site, available and already in the operating budget for the installed pumps that are being rehabilitated or replaced. Nevertheless, an electric drive primary pumpset is often a good alternative for cost reduction during rehabilitation at a pump station or inside a treatment plant.