July 11, 2018

Metropolitan Pump System Design: Environmental Factors & Energy Efficiency are Common Denominator from Project to Project

Pump System Design Environmental Considerations

We’ve said it before and we’ll probably keep saying it because it’s always seem to be true: No two jobs are exactly alike. Even “off the shelf” projects come with unique features or challenges. However, there are a few commonalities that exist from project to project and one of those that continues to gain momentum, from residential to municipal projects, is a focus on the environment. When working in the water industry, water use and conservation are immediate environmental factors that come to mind, and energy efficiency is close behind in importance.

Many building owners are already turning to various certifications and initiatives – including ENERGY STAR, LEED-EB certification (the LEED Green Building Rating System), and IEEE 519 standards – to demonstrate a commitment to the environment. Though building occupants certainly play a role in this effort, the construction of these buildings and the various technologies and systems they rely on make a big difference, too. Metropolitan understands the importance of these factors and continues to help customers develop more energy and water efficient buildings by offering products that meet changing demands. More specifically, in response to both code changes and customer needs, we’re focused on how variable speed drives (VSDs) can help better service both our customer and the environment.

VFD Systems Offer Many Advantages

Though there are several types of VSDs, the most common and most energy efficient is the variable frequency drive (VFD). As a result, several years ago, in pursuit of greater energy efficiency, commercial building codes changed to require that building booster pumps use VFDs. This change was a positive step toward more efficient energy use in larger buildings, earlier VFD technology was fairly expensive and less reliable, but today, VFD booster pump systems are more affordable and building owners are able to truly appreciate the benefits of these systems, which include

1. Energy savings as great as 30%-50% percent when compared to traditional constant speed pumps.
2. Improved system control as a result of easily adjusting to variations.
3. Improved system reliability and decreased maintenance as a result of reduced wear to the pump.
4. Reduced noise due to higher velocities through piping and “water hammer”.

In short, VFDs eliminate most of the shortcomings and risks associated with single speed pumps. From added flexibility in equipment, reduced energy costs, the elimination of water hammer and the ability to maintain accurate and appropriate system pressure, VFD’s or VSD’s are, in a way, the perfect solution.

Naturally, as experts in the world of pump systems, Metropolitan knows all about the benefits of these systems and, most importantly, how to make them work for our customers.

The Metropolitan Way

From water booster systems to lift stations, the engineers at Metropolitan can assess your needs and help you settle on the optimal system. Our variable speed controls help you save energy and money while also simplifying overall system costs. As an added feature, the boost mode in our system takes things one step further by minimizing pump usage during off-peak periods. When minimal demand is on the system, our controls automatically increase the pressure to charge a hydropneumatics tank that stores and then supplies water during low usage times, allowing the pump to remain off during this time. Thanks to Metropolitan’s patented Load-Sharing Technology, we also manufacture specialized variable speed systems to maximize the efficiency of systems containing pumps with dissimilar flow capacity, pressure capability, and motor size.

Applications

Storm Water Pumping – Wet well storage capacity can be reduced in storm water lift stations by matching the pump capacity to the incoming storm water flow and infiltration. Large pumps are often required to handle the “100-year flood”. When these pumps turn on at full speed, they pump the wet well down before more water can come in. Some larger installations have sluice gates that take time to open. Before this can all happen, the wet well is emptied, and the pumps shut off. Then the cycle starts again. With proper control tuning and variable speed operation of the pumps, a smooth evacuation pump down can occur at the rate of the rain water entering the wet well.

Sewage Lift Station With Long Force Mains – By pumping at a slower flow rate matching the incoming sewage flow rate, the friction loss can be minimized, and all the water evacuated at a lower kilowatt usage. Friction increases with the volume of water through the pipe. The added friction loss in force mains that are a half a mile or more, requires more HP and VFDs allow for a more efficient system.

Municipal Water Tower Filling Application – Water Towers must be kept from freezing in the winter. We put summer and winter modes of operation into our controls for water tower fill applications. During the summer, the tower is kept full (and system pressure is constant)and chlorine residual is maintained by turning over the water in the tower per EPA requirements. During the winter, less water is typically used, and the water levels are adjusted to allow for faster turnover and to keep the water from freezing, while still keeping pressures from varying too much.

Multi-Story Buildings – A remote pressure transducer can be in the top of the building and pressure can be controlled based on this pressure or local system pressure. Metropolitan has engineered hundreds of variable speed pump systems over the past 60 years. The key to our success has been taking system responsibility for pumps, VFDs, logic controls, etc. This allows Metropolitan technicians to precisely adjust the variable speed controls to meet exacting system conditions.

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