Preseason pivot checkup

A preseason inspection of pivots is particularly important for those who experienced frequent and heavy rainfalls last year, since the pivots may have seen little use. Whether the system uses electric or hydraulic drive, it's best to start with the basics. Following are a few inspection pointers derived from Valley, Reinke, and the University of Nebraska.

• Make sure tires are inflated to the specifications in the owner's manual. Also check that wheel lug nuts are tight.
• Change the engine oil and all filters on pump engines. Also, check engine hours and refer to the service interval on valve adjustments and other service that may be needed. Finally, drain, flush, and refill the cooling system.
• Check the system for worn U-joints, and ensure that driveshaft shields are in place.
• Check the condition of the water-carrying conduit, as well as the boots, clamps, and gaskets.
• Check for broken or worn sprinkler and replace them as necessary. As a general rule, sprinkler packages should be replaced at least every 10,000 to 12,000 hours of operation.
• Inspect the pivot pad and anchor bolts.
• Be sure to grease all moving parts, including the pivot point bearing, towable hubs, and corner rollers.
• Check hydraulic fluid levels and look for any leaks on hydraulically driven units.

Micro-Switches Have a Limited Life

Check the alignment of the system and ensure the tower box microswitches are set properly. Improper settings can cause pivot misalignment, which results in shutdowns. Keep in mind that the microswitches used on many electrical systems for both the alignment and safety circuits have a recommended 10-year service life.

• Be sure to power down the equipment before checking any electrical connections. Once the power is off, check for loose connections or loose cord grips in tower boxes. Also, check for frayed wires on the pump drive motor, as well as the pivot itself, and inspect for damage by rodents.
• Drain any water that has accumulated in the gearbox and center drive, making sure the gear lubricant is at the proper level.
• When applicable, check the chemigation pump and related safety equipment operation. Check hoses and replace if cracking is noticeable.
• Refill the drip oil reservoir and allow oil to drain into the drip line based on pump column length.
• Remove the sand trap and thoroughly flush the system with water.
• If possible, examine yield maps to help identify possible irrigation issues. The impact of a single sprinkler problem, such as being plugged, can be significant in yield reduction.
• Start up the unit and bring it up to pressure to check the system for leaks and operation of the sprinklers. If the system is on rolling or hilly terrain, regulators are also needed for uniform application and definitely should be checked. If you find water squirting from the side of any regulators, it's a sign that the rubber bladder has failed.

Record Pressures

Going forward, it's a good idea to keep a record of the outlet pressure, flow rate, and energy use on a regular basis (at least once per month) to evaluate pump and motor performance throughout the season and identify when maintenance is needed on the pump or power supply.