Getting pumped

Whether you're selecting an irrigation pump to replace the one in your existing system or a new-install system, you'll first need to understand the different types available. While there are pumps designed to fit each irrigation system, don't be fooled into thinking that you can randomly select one and it will automatically fit the needs of your system. Unless you've calculated the amount of flow your system needs and determined how much pressure it will take to achieve the desired flow, you've still got some homework to do. If you're still not sure how to select a pump, call a dealer and discuss your options. A dealer will be able to direct you to the type of pump you need, and may suggest an option you didn't even know about. Listed below are some of the pumps available for irrigation systems. If you need more information, or would like to contact the manufacturer directly, use the circle numbers provided at the end of each product description.

Who: Flowtronex PSI Inc.

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What: FloBoy RC Series

Description: The easy-to-install FloBoy RC Series Pumping System offers flow rates up to 60 gpm at pressures of up to 60 psi. Available in 1-, 2- and 3-hp models, the constant-speed units are fully prefabricated pump and control packages specifically designed for residential and commercial applications. The FloBoy product line of skid-mounted, fully prefabricated systems includes variable- and fixed-speed systems with flows ranging up to 1,200 gpm at pressures up to 130 psi. The new online pump station Configurator offers fast access to system drawing, specifications and a budgetary price estimate.
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Who: Kifco Irrigation

What: Kifco-Caprari pump

Description: Kifco-Caprari centrifugal PTO pumps come in a wide selection to fit many different irrigation applications and requirements. Rugged, efficient and easy to handle when mounted on the two-wheeled cart, a fully fitted pump has a PTO shaft, weld-on companion flanges, priming valve, primer, pressure gauge and suction adapter.
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Who: Pumpex, Inc.

What: K507 pump

Description: Pumpex pump model K507 provides a 20- × 20-inch discharge capable of producing flows of more than 18,000 gpm and head of up to 100 feet. Pumpex offers a variety of materials of construction that include a standard cast and ductile iron as well as tailor-made stainless steel, bronze and a choice of chemically compatible, duty-specific materials. The pumps also feature a modular construction designed to be maintenance-free and protect from dry-running failure.
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Who: Watertronics

What: Vertical Turbine system

Description: Watertronics offers landscape and irrigation pumping systems with comprehensive controls-software. Every station is custom engineered and built to meet individual job requirements, which means no “off-the-shelf” stations. The systems include: Vertical Turbine (VT) and Horizontal Centrifugal (HC) stations as well as Super Sports Turf (SST), Landscape Sports Turf (LST) and Residential Landscape Turf (RLT) self-enclosed stations.
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BY DEFINITION

Gpm — Gallons per minute of flow.

Psi — Pounds per square inch.

NPSH — Net positive suction head. This is the pressure a pump requires for cavitation-free operation. For example, to prevent cavitation, water must enter and exit a pump at the same pressure so that it enters and exits at the same speed. This prevents vaporization of the water as it enters the pump, thus preventing cavitation. Available NPSH is the pressure that exists at the suction inlet of the pump (which is dictated by the site, not the pump). Required NPSH is the pressure needed for pump operation (it varies by pump model). For a pump to operate correctly, available NPSH must be greater than the pump's required NPSH.

Cavitation — A condition that occurs if the pressure acting on a stream of liquid falls to or below the vapor pressure of that liquid. When cavitation occurs, bubbles appear spontaneously. The pumped water level fluctuates and it induces noisy sounds as if rocks are passing through the pump. Your system will show erratic electric-load consumption, and ampere-meter readings will fluctuate wildly. Cavitation causes wear and pitting on the impeller's vanes (especially at the entrance) and bowl casing. To remedy the cavitation problem, you must replace the bowl(s) and ensure proper submergence if the bowls are installed in a deep-well pump.

Total dynamic head — This is the total pressure, in feet, that the pump must overcome to perform its work as designed. Numerically, it is the sum of the discharge head, suction head and the friction head in the suction pipe.

Source: Grounds Maintenance, “Keeping pumps pumping,” October 1996.

NO PRESSURE

When selecting an irrigation pump, no relationship is more important than that of pressure and flow. The performance of a pump depends on it. How much water the pump is moving directly affects the pressure it is creating, and is the determining factor as to whether the pump is suitable for your irrigation system. It is important to understand that pressure and flow have an inverse relationship: As flow increases, pressure in the pump decreases.

THE FORCE

Almost all turf-irrigation pumps are centrifugal pumps. These types of pumps use centrifugal force (hence the name) to push water out. Water entering the pump hits an impeller that imparts circular motion to the water, causing it to spin, and forces it outward to the pump wall. As this happens, the water picks up speed, which becomes pressure as the water exits the pump. Some centrifugal pumps are “multi-stage,” meaning that they have more than one impeller and casing. In these pumps, pressure increases each time water is passed from one impeller to another (at each stage). There are generally two categories of centrifugal pumps:

Horizontal centrifugal pumps are designed with the motor and pumping units installed horizontally at ground level. You would typically use this kind of centrifugal pump for shallow-well or short-suction-lift pumping.

Vertical centrifugal pumps are designed with the motor at ground level and the pump in the water or near the water surface. They are used for deep-well pumping.

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© 2014 Penton Media Inc.

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