To determine which pump is best for your situation, evaluate the jobsite conditions carefully. "By knowing the application completely, a contractor can choose a pump from a particular family, which has many different sizes and capacities," says Belli. "Focus on application first, size of pump second."
"Many of today's pumps are designed to be as effective as possible in wide-ranging jobsite conditions," notes Cooper. But there are factors that can influence your choice of pump, including the availability, or lack of, power; the condition of the intended discharge area; and whether or not the pump can be safely placed near the water or material being removed. "Obstructions are another concern," he continues. "Ask yourself what obstructions exist along the pathway of the discharge hose or pipe."
Belli cites a few additional factors, including the location of the pump, type of fluid being pumped, noise concerns and desired output/expected results.
The height of the pump in relationship to the liquid being pumped can affect suction lift -the vertical distance from the top of the free state of water to the eye of the impeller. Be especially mindful of this at higher elevations, where physics and atmospheric pressure limit the maximum amount of suction lift. If the liquid being pumped is located a long way from the pump and you can't move the pump any closer, you may want to consider using a submersible pump. It can be inserted directly into the water to eliminate any suction lift limitations.
Different types of fluid being pumped also affect which type of pump is the best choice. "Handling clear water vs. solids and fibrous and stringy materials may mean the difference between a solids-handling trash pump or a non-solids-handling pump," says Belli. "Acidic or salty fluids may require the use of a pump made from a material other than that which is standard." Fluids with higher temperatures can also be a concern because they can cause cavitation due to the vapor pressure of the fluid's high temperature.
While noise concerns relate more to heavily populated residential areas, business districts, hospitals and school zones, the Contractor's Pump Bureau has instituted an unofficial standard for acceptable noise levels for pumps and pumping equipment. "Studies have shown that prolonged exposure to high decibel levels of noise can damage your hearing," says Belli. "More and more cities across the United States are demanding additional sound attenuation on construction equipment to reduce the noise levels when they are in operation. The same goes with pumps."
If time is of the essence, you will want to evaluate the desired output/expected results to ensure you have a large enough pump to move fluid in a timely fashion. Belli relates that a 3-in. diaphragm pump moves about 90 gpm (129,600 gal./day), while a 6-in. wet prime trash pump moves about 1,500 gpm (2,160,000 gal./day). "The diaphragm pump will take longer to dewater than the wet prime trash pump and may not be suitable to meet the deadline," he points out. "It also raises the question of budgetary monies secured for a job. Using a pump that produces less capacity and takes longer to dewater may overdraw the fuel budget."
To help in sizing the pump to the job, each pump manufacturer publishes detailed performance data on its equipment models. Cooper encourages evaluating these specifications against your requirements. Factors you will need to know include viscosity of the material and the desired flow rate. You will also want to know how much distance exists between the pump and the discharge point, and the change in elevation between the material being pumped and the discharge point. Other factors include the amount of water that needs to be removed (expressed as gpm), the static head in feet (i.e., the difference between the current water level and the desired water level) and the type and amount of power available.
When selecting an electric submersible pump, check the power available from the source -either grid or generator. It must be powerful enough to start and run the pump(s) motor. Also make sure that the pump motor voltage rating matches the power source voltage.
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