A: Basically what you’re doing on flood control, is you’re watching the level in the detention systems around the city. There’s usually large-volume pumps that are designed to pump it into a city main, a sewer main, or for us—a bayou that flows into the Gulf of Mexico.
So really what you’re looking at is the current levels. They’ll be a multitude of different styles of liquid level controls; floats or sensors telling that pump when it’s time to turn on.
Usually, there’s an alarm with that. If the pump can’t catch up, there’s another backup sensor that will have an alarm that goes off. That’s how they maintain the flood control systems.
When designing a flood control system, there are many choices you must make in terms of design and different components. Whether it be for municipal, residential, or agricultural applications there is one key component of any system—the pumping station.
We’ll cover some basic considerations that will factor into your flood control pump station design. Additionally, we’ll touch on some general design practices as well. Keep in mind this is no substitute for consulting the direction of a certified engineer. It is meant simply as a guide to give you an idea of where to start and what to expect.
Considerations For Flood Control Pump Stations
Carefully going through this list of things to consider when building, we will build a solid base for success. Additionally, it will help you from overspending and keep costs within a realistic budget:
- Review the calculations you’ve gathered for the head and flow. Note your average as well as your peak and expected minimum flows. You’ll also need to determine if the head requirement will be static or vary. This will have a significant impact on the pump’s duty point.
- Check the site and surrounding area to confirm head and flow—especially if this is to replace an old flood control pump station. Circumstances and topography may be different than it was when the station was initially designed.
- Determine how many pumps you need based on the calculated flow and head requirements.
- Based on gathered information, determine what type of pump to use in your situation.
Choosing The Right Pump
Typically, you want to use propeller pumps when you have a low-head application. For medium-head applications, you need a mixed-flow pump. With submersible pumps, you gain a significant advantage over other pump types when you install them in columns. This is evident in applications like using long-shaft turbine pumps for flood control. The advantages of this installation include:
- Reduced costs to the municipality
- No shaft alignment issues
- Less expensive and more efficient installation
- Smaller footprint
- Silent
- Flood proof
- Increased reliability;
- A smaller superstructure is needed
- Less maintenance and cheaper to maintain
- More flexible
- Better Efficiency
Flood Control Pump Installation Options
The best installation option usually is the one that offers flexibility for lower construction expenses. Column-type installation offers flexibility for anything from free outflow to pressurized setups. They also offer the option to install at an incline.
A sump design can have a serious impact on the life of the pump. If the sump design is not optimal, it leads to poor performance and undue strain. This is due to cavitation and vibrations at the pump inlet. A poor design of this nature also leads to excessive sedimentation of rags and sand which leads to even more problems with vibration.
The main requirement to consider when going with a sump design is to ensure optimal conditions for the pump inlets. The flow to the pump needs to be consistent, steady, and not be full of swirls or entrained air design requirement for a sump design is to provide optimal inlet conditions for the pumps. The flow being delivered to the pump units should be uniform, steady, and free of swirls or air bubbles.
Pumps that are column-installed offer high volume which makes them sensitive to varying conditions in the suction chamber. You must take caution to ensure optimal performance to extend the life span. Specifically, the dividing walls and pump positioning needs to be executed in a way that avoids air ingestion, turbulence, and surface vortices.
Installation Factors To Consider
- The velocity and fluid distribution within the inlet channel need to be consistent. The bottom angle should be inclined at about 10-15 degrees for optimal performance.
- The velocity of water flow in the inlet channel needs to be less than 1.2 meters per second (m/s).
- The overall velocity of water within the pumping station is best between 0.3 and 0.5 m/s.
- The effects of disturbances of the flow need to dissipate as far from the pump intake as possible.
- Stagnation zones must be avoided. If the design incidentally creates stagnation zones, fill them with concrete before operating.
- Be diligent in avoiding suction vortices in regards to pump immersion. The general rule is, pump immersion should be at least 1x to 2x the diameter. That number is also dependent on the flow rate, so go with the manufacturer’s recommendations.
- There should be a free distance between your pump and the bottom of the sump. This distance should always be half the diameter of the pump or more for cavitation avoidance.
- Pump and column installation need to be situated symmetrically in the sump. Additionally, make sure there’s enough distance from the outer diameter of the pump to all sump walls. Again, at least half of the pump diameter is the distance you want.
- When you have several pumps in parallel, separator walls are recommended so they don’t interfere with each other. This ensures water is channeled to each pump uniformly.
- When the design is completed, subject it to a thorough analysis. Pay special attention to screens and see if there’s a need for a sludge pump as well.
Consult Your Flood Control Pump Supplier
Flood control pumps are serious investments and the maintenance and repairs can be expensive. Even with a well-designed system with high-quality pumps—wear and breakdown are expected eventually.
Pump stations require frequent monitoring and upkeep to ensure longevity and proper performance. You can glean a lot of knowledge and assistance from the certified technicians here at Gulf Coast Pump & Supply.
Contact us today so we can guide you in building the best flood control system for your needs.