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This publication explains how to maintain irrigation pumps, motors, and engines for peak efficiency. The publication includes descriptions and diagrams of recommended installations, checklists for maintenance tasks, and a troubleshooting guide. Each system component is treated separately and maintenance tasks are broken down by how frequently they need to be done. References and resource listings follow the narrative.
Efficient irrigation begins with properly installed and maintained pumps, motors, and engines. Equipment problems and management problems tend to go hand in hand. Equipment that is badly designed or poorly maintained reduces the irrigator's degree of control over the way water is applied. Problems like patchy water distribution and inadequate pressure make it impossible to maintain correct soil moisture levels, leading to crop stress, reduced yields, wasted water, runoff, soil erosion, and many other problems.
![]() Figure 1. Ideal and Poor Installations (Adapted from Saving Energy on Montana Farms and Ranches, Montana Department of Environmental Quality.) |
The term "pumping plant" refers to the irrigation pump and motor or engine, considered together. If you have an older system, the pumping plant might look like Fig. 1, Poor, on the discharge side. The next time you rebuild the pump, replace the fittings so that your system will look like Fig. 1, Ideal. An ideal installation should also have:
Fig. 2 shows what your pumping plant should look like when pumping from a surface source such as a river or canal. The pumping plant should also have:
![]() Side View |
![]() Top View Figure 2. Recommended Pump Installations (Adapted from Energy Efficient Pumping Standards, Utah Power & Light Company.) |
On the Suction Side of Pump:
On the Discharge Side of Pump:
![]() Figure 3. Deep Well Turbine Pump (Adapted from Energy Efficient Pumping Standards, Utah Power & Light Company.) |
Refer to the left half of Fig. 3 for a properly installed turbine pump in a well; many of these same principles apply to turbine pumps in sumps. The properly constructed well should also:
The poorly constructed well in the lower right half of Fig. 3 shows a well casing that is not centered in the well. Vertical slotted pipe perforations are above the minimum water level, creating cascading water.
The importance of a properly installed control panel cannot be overemphasized for personal safety and for protecting your investment in your pump and motor. Your control panel should:
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Your control panel should include the following controls at a minimum:
Every irrigation system needs regular maintenance in order to run efficiently and reliably. Poorly maintained systems waste energy and money, and are prone to breakdowns that cause crop losses and yield reductions.
Caution: The recommendations below are not comprehensive and may not be correct for all systems. Consult your owner's manual for recommended maintenance procedures and always follow the manufacturer's instructions if they differ from the ones in this guidebook.
General
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Make a habit of checking that the motor is securely bolted to its platform. Mounting bolts can vibrate loose. Check to see that rotating parts aren't rubbing on stationary parts of the motor, causing damage to the motor.
Remember that an electric motor is an air-cooled piece of equipment and needs all the ventilation it can get. Excessive heat is a main cause of reduced motor life.
Motors also like to be dry. Keep motor windings dry by keeping pump packing in good condition. Even if windings are protected from moisture, minerals in the pumped water can attach to the windings and cause early failure. Motors that operate at 3600 rpm experience twice as much wear as motors operating at 1800 rpm. Regular maintenance is especially critical for 3600 rpm motors and pumps.
Maintenance Tasks
At season startup:
Periodically:
At end of season shutdown:
Motor Electrical System
Wide temperature fluctuations during the year can cause electrical connections (especially in aluminum wire) to expand and contract, loosening connectors. Loose electrical connections cause heat buildup and arcing at electrical terminals. The voltage drop across loose connections will cause the motor to operate at less than its rated voltage, increasing internal motor temperature. Increased heat will break down motor winding insulation, resulting in electrical shorts and motor failures. A loose or broken connection can also unbalance the phases of three-phase power and damage the motor windings.
Caution: Before conducting these tasks, be sure power is off at the utility disconnect switch. It may be necessary to have the utility company shut the power off.
Maintenance Tasks
At season startup:
Twice a year:
Motor Bearings
Lubricate the motor according to the manufacturer's instructions. Intervals between lubrication will vary with motor speed, power draw, load, ambient temperatures, exposure to moisture, and seasonal or continuous operation. Electric motors should not be greased daily. Bearings can be ruined by either over- or under-greasing.
Fill a grease gun with electric motor bearing grease and label it so it won't be confused with other types of lubricating grease.
Caution: Lubrication instructions in owner's manuals should be followed if they differ from these. Newer motors may have sealed bearings that cannot be lubricated.
Recommended Re-greasing Periods for Motors | |||
Horsepower Range |
|||
Type of Service |
1-9 |
10-40 |
50-150 |
Normal Duty (8-hour day) |
8 mos. |
6 mos. |
4 mos. |
Heavy Duty (24-hour day) |
4 mos. |
3 mos. |
2 mos. |
Maintenance Tasks
Change the grease at recommended intervals to remove any accumulated moisture:
Caution: If old grease is not expelled as the new grease is pumped in, stop adding grease and have your motor checked by a qualified repair person. Adding new grease without old grease being removed could blow the seals and push grease into the motor windings, causing the motor to overheat and reducing its service life. Do not over-grease your motor.
Control Panel Safety Precautions
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Never use the main disconnect to start or stop your motor. It is not intended for this purpose. Using the main disconnect to start and stop the motor will cause excessive wear of the contacts and arcing can occur. Use the start and stop button.
If the overhead lines to your control panel's service are obstructed by tree branches or other items, have the utility company clear the lines.
Have an electrician inspect your panel to ensure that:
General Maintenance
Have your electrician or pump maintenance person do a Megger check on the control panel, motor, conduits, and other electrical connections. The Megger device applies a small amount of voltage to an electrical component and measures the electrical resistance. A Megger test can also detect potentially harmful moisture in windings.
Any time the main disconnect switch has been left open or off, operate it several times before leaving it closed or on. Copper oxide can form in a few hours and result in poor contact and overheating. Any type of corrosion can cause poor contact, poor grounding, and direct or high-resistance shorts.
Caution: After opening the control panel but before touching the controls inside, use a voltmeter to be sure that the incoming power is disconnected or turned off. If necessary, have your utility disconnect the power. If you have any doubts about the safety of your control panel, WALK AWAY AND CALL A QUALIFIED ELECTRICIAN. Even a current of 15 milliamps (one milliamp is one one-thousandth of an amp) can cause serious injury or death. Always play it safe!
Maintenance Tasks
At season startup:
At end of season shutdown:
Make a habit of checking that the engine is securely bolted to its platform; mounting bolts can vibrate loose. Regularly check coolant, oil levels, fuel, and fan belts. If coolant or oil is down, check lines for leakage. On diesel engines, check injectors and fuel lines for leaks.
Engine power is affected by altitude and air temperature. Derate engine power output by 3.5 percent for every 1,000-foot increase in altitude over 500 feet above sea level. Derate output by 1 percent for each 10-degree increase in air temperature above 85 degrees F.
Engine Startup
(Beginning of Season)
Maintenance Tasks
Engine power is affected by altitude and air temperature. |
Engine Air System
Always replace disposable air filters with new ones. Cleaning can distort the filter and allow more dirt to enter.
Maintenance Tasks
Engine Electrical System
If you have a natural gas engine, be aware that natural gas has a higher octane value than automotive gasoline. You can increase engine efficiency and reduce fuel consumption by setting the ignition timing to take advantage of the higher octane. Consult the engine manufacturer for recommendations on how to do this.
Maintenance Tasks
At season startup:
Twice a year:
Engine Oil and Lubrication
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Have a sample of engine oil analyzed for contaminants, which signal abnormal wear. Intervals between analyses will depend on the engine, and analysis may be cost-effective only for larger engines. Equipment dealers should know where the oil can be analyzed and how often this should be done.
Use only the oil recommended by the manufacturer. Tag each engine with a label identifying the proper oil.
Maintenance Tasks
Twice a year:
Engine Fuel and Coolant
Maintenance Tasks
Engine Shutdown (End of Season)
Maintenance Tasks
Do not store batteries directly on concrete. |
Centrifugal Pump Startup
(Beginning of Season)
Maintenance Tasks
![]() Figure 4. Centrifugal Pump and Motor |
General
To avoid water leaks, make sure that all gaskets are the correct ones for the coupling or flange. Eliminate air leaks in your pump's suction line by coating threaded connections with pipe cement or white lead and drawing them tight. Also examine suction line welds for cracks, which will allow air leaks.
Choosing Gaskets |
If your pump isn't delivering water, verify that the pump shaft is turning in the direction of the arrow on the pump casing. As viewed from the motor end, the rotation is usually clockwise, but check the startup instructions that came with the pump. On three-phase motors, swap any two power leads to change rotation. It is recommended that a qualified electrician perform this task.
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If the pump doesn't prime, check for air leaks on discharge valves. Many all-metal gate-type valves won't seal properly to create a vacuum. Sand or other debris lodged between the rubber flap and the valve seat will prevent check valves from sealing and forming a tight joint. See if the rubber face is cracked or chipped and not seating. Replace the gate valve or check valve. Check connections between pump and primer. On a hand primer, if grass or other debris is lodged in the check valve, air is pulled back into the pump at every stroke and the pump won't prime. After proper priming, fill the system slowly.
Maintenance Tasks
Twice a year:
Servicing Impeller and Wear Rings
If you suspect that your pump impeller is clogged or damaged, or that the wear rings are worn, you can dismantle the pump. This will take some work and is best done in the shop. Or have a qualified pump repair shop undertake this procedure. Always follow the directions in the manufacturer's manual, if available, instead of the following simplified directions.
Net Positive Suction Head (NPSH) and Cavitation Many people are surprised to learn that centrifugal pumps don't pull water through a suction pipe; they can only pump water that is delivered to them. When air is removed from the suction pipe by a primer pump, the weight of the earth's atmosphere forces water to rise into the pipe, delivering water to the pump. Even in the best of circumstances (including a near-perfect vacuum), the maximum water column that can be forced by atmospheric pressure never exceeds about 33 feet in height. As elevation, water temperature, and pipe friction increase, the height of the water column that can be forced drops. The maximum column of water that can be created in a pipe under a given set of conditions is known as Net Positive Suction Head or NPSH. Insufficient NPSH often occurs at startup. Since the pump is working against low pressure, it pumps a larger volume than in normal operation. This larger volume creates friction losses in the suction line, reducing NPSH. Too little available NPSH can result in vaporization of water in the eye of the impeller, causing cavitation, a noisy condition where vapor bubbles collapse violently in the pump. To stop cavitation, close the discharge valve. If cavitation is allowed to continue, the impeller and pump casing can become pitted and damaged, reducing pump capacity. To eliminate cavitation as well as water hammer, and to prevent high amperage draw on demand meters, open the discharge valve slowly to fill the mainline whenever you start up the pump. Caution: Don't let the pump run more than two minutes with the discharge valve closed. |
Servicing the Pump Packing
A pump with shaft sleeve and packing in good condition and properly adjusted shouldn't require constant re-adjustment, but should be checked daily. Unless proper leakage (about 8 to 10 drops per minute) is running through the packing box, the packing will become overheated and dry out, eventually burning and scoring the shaft sleeve. Excessive dirt, silt, or sand in the water can also score the sleeve.
Check for an improperly greased or worn rotary shaft seal by running the pump and squirting oil on the shaft just outside the seal. Oil drawn into the seal indicates a leak.
If the pump has been out of service, the packing may be dried and hardened. Air can leak into the pump through the packing box and the pump can lose prime.
Maintenance Tasks
![]() Figure 6. Pump Packing |
Grease the packing box annually with a proper pump packing grease. Less frequent maintenance causes grease to harden, making this task very difficult.
Replacing the Packing
Old packing should be replaced completely if leakage cannot be reduced by adding a new packing ring to the old packing, or if the packing is burned (dried up and scorched) or has leaked excessively during the season.
Once the packing is burned and the shaft sleeve is scored, no amount of adjustment will maintain proper leakage for any length of time. |
Caution: This task is difficult. Have a qualified pump repair shop do it if you are in doubt. If you are attempting the procedure yourself, do it in the shop rather than in the field.
Caution: Don't stop leakage entirely.
Centrifugal Pump Shutdown
(End of Season)
In cold climates, it is critical that all water be drained from pumps prior to freezing weather.
Maintenance Tasks
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General
![]() Figure 7. Oil-Lubricated Turbine Pump |
Some of the instructions below also apply to submersible pumps.
Make a habit of periodically checking that discharge piping is firmly supported in the area near the pump. Make sure the pump is securely bolted to the platform.
If your turbine pump is installed over a well and you've experienced water supply problems, check the static level and drawdown in the well. A deeper pump setting might be required.
Maintenance Tasks
At season startup:
Periodically:
Annually:
Mobil DTE 797
Lubriplate HO-0
Chevron Turbine Oil GST32
Shell Turbo T Oil 32
Maintain bearing oil at the proper level. Overfilling the oil reservoir can cause oil to overflow when the motor heats up during operation. The excess oil will adhere to the motor and to ventilation screens, collecting dirt and debris and reducing the motor's ability to dispel heat.
Maintenance Tasks
At season startup for oil-lubricated pumps:
At season startup for water-lubricated turbine pumps:
Periodically:
Annually (or according to manufacturer's recommended interval) adjust the head shaft nut on short-coupled turbine pumps:
Caution: If you are unable to turn the shaft by hand, and you have raised the shaft by five or more turns of the nut, remove the pump, disassemble, and inspect for damage or debris. If you have any questions about this procedure, consult your pump dealer.
Shaft adjustment needs to be more precise for deep well turbines. Shaft stretch needs to be considered. Refer to the manufacturer's instructions or consult a qualified pump dealer.
Maintenance Tasks
At season startup for oil-lubricated pumps:
Periodically:
Submersible Pumps A submersible pump is a turbine pump that is close-coupled to a submersible electric motor. Since both pump and motor are suspended in the water, the drive shaft and bearings required for a deep well turbine pump are eliminated. The pump is located above the motor and water enters the pump through a screen located between the pump and motor. Submersible pumps use enclosed impellers. The motors are smaller in diameter and longer than turbine pump motors. Inadequate circulation of water past the motor may cause it to overheat and burn out. The riser pipe must be of sufficient length to keep the bowl assembly and motor completely submerged at all times and the well casing must be large for water to easily flow past the motor. Electrical wiring from the pump to the surface must be watertight with sealed connections. |
This section identifies symptoms and possible causes under Suction, System, and Pump. Find the Symptoms and then look across to the left to see possible causes. Most often, suction problems are the cause. Contact your pump repair shop for additional help.
Caution: This troubleshooting guide is general and does not cover all the possible system configurations or problems that might be encountered.
See Troubleshooting Tables. [PDF/57K]
Black, Richard D., and Danny H. Rogers. 1993. Evaluating Pumping Plant Efficiency Using On-Farm Fuel Bills. Kansas State University Cooperative Extension Service, Manhattan, Kansas. 4 p.
Loftis, J.C., and D.L. Miles. 2004. Irrigation Pumping Plant Efficiency. Colorado State University Cooperative Extension Service, Fort Collins, CO. 4 p.
NCAT Publications
The Montana Irrigator's Pocket Guide. 2003. By Mike Morris, Vicki Lynne, Nancy Matheson, and Al Kurki. National Center for Appropriate Technology, Butte, MT. 161 p.
A take-to-the-field reference to help irrigators save energy, water, and money; includes guidelines for water management, equipment maintenance, and handy conversions and formulas. Get a free printed copy by calling 800-346-9140 (toll-free).
Other Publications and Web sites
Extending Electric Motor Life. Hansen, Hugh J. and Walt L. Trimmer. PNW 292. Oregon State University, Corvallis, OR. 4 p.
Available from Oregon State University Extension Service. Cost $0.25.
Order from 541-737-2513, 800-561-6719, or puborders@oregonstate.edu
Irrigation Water Pumps. 1993. By Thomas F. Scherer. Publication AE1057. North Dakota State University Extension Service, Fargo, ND. 12 p.
Covers basic operating characteristics of centrifugal, deep well turbine, submersible, and propeller pumps, as well as pump power requirements and selection criteria.
Maintaining Electric Motors Used for Irrigation. [PDF/304K]
2000. By Richard F. Beard and Robert W. Hill. Utah State University Extension Service, Logan, UT. 5 p.
Describes factors that affect electric motor performance and service life and describes procedures for controlling internal motor heat.
Irrigation Engineering Publications
University of Nebraska Institute of Agriculture and Natural Resources.
Dozens of publications on irrigation management and hardware.
Wateright
Center for Irrigation Technology at California State University, Fresno.
A "multi-function, educational resource for irrigation water management." Includes an energy use/cost calculator, guidelines for estimating fuel requirements, options for reducing energy use and costs, and discussions
of various other energy-related topics.
Maintaining Irrigation Pumps, Motors, and Engines
By Mike Morris and Vicki Lynne
Paul Driscoll, Editor
Sherry Vogel, HTML Production
IP299
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This page was last updated on: August 28, 2014