Introduction
Understanding water supplies and the pumps that manage them is essential for anyone working in the field. From wells and ponds, to rivers, streams and lagoons, various water sources require different types of irrigation pumps to ensure efficient and effective water management. In this blog post, we will explore the workings of different pump types, including floating pumps, submersibles, and line shafts, and examine their applications, benefits, and potential challenges. Whether you’re dealing with the hassles of priming or selecting the right pump for your specific needs, this guide aims to equip you with the knowledge to make informed agriculture irrigation pump decisions.
What are Agricultural Irrigation Pump Options?
Let’s explore agricultural water supplies and irrigation pumps, covering their various types and operations to help you, the grower, understand what you might encounter in the field. Many different water sources are available to agricultural producers. There are different types of pumps for each water source, with pros and cons for each.
What is a floating irrigation pump?
A floating pump is commonly used for irrigation ponds, manure lagoons, and rivers with sufficient depth. This model is short coupled to a centrifugal pump and driven by an electric motor. The advantage of this setup is its self-priming capability. Alternative options involve placing the pump and motor on the shore, with a screen in the water, requiring priming each time you start it—a significant hassle for an agricultural irrigator. To avoid pump priming issues, we prefer floating pumps. This example is a centrifugal floating pump, but we also use line shaft or short set pumps for higher pressure and flow needs, combining them with floating setups. For more information on floating pumps, check out https://www.canfieldcustompumps.com/ (The centri-float is the centrifugal floating and the turbi-float is the turbine floating pump).
Most pump setups installed by NutraDrip Irrigation are three-phase, 480-volt power. If you have single-phase power, our team converts it to three-phase using either a rotor phase or preferably a Variable Frequency Drive (VFD). A VFD converts single phase to three phase and adjusts the motor speed to maintain optimal irrigation system pressure, functioning like a throttle on a tractor. It ensures smooth startups and efficient motor operation, reducing stress on the motor and extending its life. VFDs enhance motor efficiency and protect the system from water hammer when opening and closing valves or flushing filters. They adapt the pump speed to match water usage, maintaining the desired system pressure. It’s crucial to note that three-phase systems are rotation-specific. If two legs are switched, the pump’s rotation reverses, reducing pressure. Always check pump rotation on irrigation startup, especially after electrical work, to ensure proper operation.
Submersible Pumps
The second type of pump we’ll discuss is the submersible pump. In a submersible setup, commodity producers typically see an elbow emerging from the ground and a wire leading into it. There’s almost nothing visible on the surface, as the submersible pump operates deep underground. These pumps can be large and can be used in deep wells, such as those in southern Missouri, which can reach depths of 1,200 feet.
Submersible pumps can deliver small or large volumes, with ranges from 100-1,5100 gallons per minute. They are generally less expensive than line shaft pumps, which we’ll discuss next. However, a key disadvantage is that the electric motor is located deep underground in the well shaft. If there’s an electrical issue, such as an electrical short from a lightning strike, servicing the submersed pump requires pulling out a pump from the bottom of a thousand feet of well column, which can be costly.
Despite the challenges, we find submersible pumps to be quite common in agricultural irrigation wells, accounting for about 60% of our work. Line shaft pumps make up about 30%, and centrifugal pumps around 10%. The electric motor in a submersible pump is located in the lower half, immersed in cool water, ensuring it remains cooled by the water.
Line Shaft Pumps
The third option is the line shaft pump. In this setup, an electric motor or engine is attached to a shaft that drives the bowls or impeller deep in the irrigation well. The depth of your water and the required pressure determine the number of bowls. For higher pressure, more bowls are stacked, with each bowl boosting the pressure to the next one.
Line shaft pumps are highly durable and are the most common in Nebraska irrigation and western Kansas irrigation. They come in two lubrication types: water-lubricated and oil-lubricated. For oil-lubricated systems, a small oil reservoir sits beside the pump, ensuring the bearings are properly lubricated. It’s crucial to maintain this oil level to avoid damaging the bearings, which can lead to costly repairs. Water-lubricated systems are more common but can create a wet environment around the wellhead due to constant water flow.
What is a Pump Curve
Every pump will have a pump curve. This is an important document to have, as it is calculated specifically for your irrigation pump.
Pump curves can look slightly different, but they all should contain the same information. The numbers on the top graph on teh left hand side indicate the feet of head, which is the “pump language” for pressure. There is a direct calculation between feet of head to PSI: 2.3 feet of head in every 1 PSI. The numbers along the curves indicate efficiency. You can follow the pump curve to peak efficiency – 80% efficiency or above is the “sweet spot” for that pump to operate at. Along the right hand side, you can see the amount of horsepower (hp) that will be needed to operate the pump at that level. The red mark indicated the designed operating capacity. The numbers along the very bottom of the graph show how many gallons of water per minute that well will be pumping. The bottom graph shows the suction or negative head pressure that a pump will have.
A VFD will help the pump be more efficient and hit that “sweet spot” on a regular basis.
Air Aspiration Cavitation: Be Aware
Another critical point about pumps is the issue of air aspiration cavitation. Cavitation can be a pump killer, especially in systems with suction. If there’s any air leak on the suction side, air can enter the pump, causing cavitation. These tiny air bubbles, when drawn into the pump, implode under the vacuum, acting like a sandblaster inside the pump and eroding its internal components.
To prevent this, it’s crucial to ensure that the suction side is airtight, particularly with centrifugal pumps that rely on suction to draw water in. Even small air bubbles can cause significant damage over time, so maintaining the integrity of the suction side is essential for the longevity of the pump. Read more about cavitation here.
Conclusion
These three pump types—submersible, line shaft, and centrifugal—are all ones we work with regularly. While well drillers typically handle the supply and servicing of line shaft and submersible pumps, floating pump options often come from NutraDrip. We also offer expertise in supplying and servicing these pumps based on your location.
The world of irrigation pumps is diverse, with each type offering unique advantages and addressing specific challenges. Floating pumps excel in self-priming and efficiency, making them ideal for ponds and rivers. Submersible pumps, though cost-effective, come with the complexity of deep well servicing. Line shaft pumps, commonly used in heavy irrigation areas, provide long-lasting performance with careful maintenance. Understanding pump curves and the role of VFDs can optimize your system’s efficiency and lifespan. By considering these insights and choosing the right pump for your water source, you can ensure reliable and effective water management in your irrigated crop field.
