Irrigation System Maintenance Tips
All modern irrigation systems are made up of common componentry. Depending on the system, there might be all or some of these components present, or the size and complexity of them may differ. The only major difference between modern irrigation systems is whether it moves (mobile) across the irrigated area or it is stationary.
In the Pump shed:
The pump is the heart of any irrigation system. The irrigation systems efficiency is reliant on the pump producing the required pressure and flow characteristics for it to be able to apply the right amount of water. Periodic testing (post commissioning) of pump performance is a great way to ensure that your pump is operating efficiently and effectively. This can be done by yourself or your service company.
Mobile Pumping units, these can be either electric or diesel powered:
- If electric, ensure weather protection shields are in place. The electric motors and cables/leads must be tested by a qualified person at least once a year to ensure electrical safety.
- Diesel motors should be services regularly to ensure reliable operation. Ensure all guards and covers are fitted before operation.
- If mobile units are mounted on a trailer, ensure to annually check the condition of the trailer hitch, wheel bearings and vibration mounts.
Most irrigation systems have filtration, whether this is before the pump as a suction filter or after the pump as a screen, disc, sand, or hydro-cyclonic filter or both. Filter maintenance is critical for the irrigation system to operate properly. Many costly failures within an irrigation system can be traced back to poor filtration.
- Suction filtration – generally this consists of a coarse screen fitted to the end of the suction line. Leaves, sticks, and other organic material are common causes of blockages for suction screens. Rivers screens are a floating variation of this and are fitted with a rotating screen and cleaning jets. River screens require additional cleaning if high organic matter and/ or algae levels are in the water.
- Screen/Disc filtration – This type of filter is usually installed on the pressure side of the pump and consists of finer screens. Multiple units can be installed in series or in parallel to increase the level of filtration. These filters require regular flushing and maintenance. Typically, a pressure variation of 35 kPa (5 Psi) across the filtration system should trigger flushing or the cleaning cycle.
- Sand filters – These use a sand medium of differing coarseness to strain particles from the water. These filters require regular “back-flushing” to clean the sand medium. Depending on the type of material and quantity being cleaned, the sand medium should be replaced regularly.
- Hydro-cyclonic – These filters use a water vortex to drop heavy sediments to the bottom of the sediment chamber. They require flushing to push out the build up of heavy solids from the sediment chamber.
Pipework comes in all sizes and materials. In irrigation, pipework can mean mainlines, sub-mains, and lateral pipework in vineyards and orchards. All pipework requires maintenance and some more than others.
- Larger mainlines and submains require yearly or half yearly flushing depending on the amount of sediment in the irrigation water.
- Lateral lines require more regular maintenance as seasonal activities can cause damage to them. Lateral lines should be checked before the irrigation starts to ensure proper operation.
Control valves and pilot solenoids come in all shapes and sizes. Control valves and pilot solenoids should be checked periodically throughout the season and serviced at least annually to ensure proper operation. A build-up of sediment or organic material inside pilot solenoids and frost/mechanical damage are the most common issues with them.
Nozzles/ Emitters/ Sprinklers:
Nozzles, emitters, and sprinklers are a critical component in metering the required volume of water to be applied. These are sized according to pressure, flow, and application depth characteristics. They should be tested against original performance factors periodically to ensure accurate operation.
- Modern nozzles and sprinklers are made from a variety of materials which have varying wear rates. For example, thermal plastic nozzles have an effective operating life of around 8-10 years. The same nozzle in brass would have an effective operating life of 2 years.
- Emitters (drippers) have a very long operating life expectancy providing they are kept free of sediments and organic materials that could clog them. Flushing emitter lines should be carried out at least seasonally. If organic material is present, then an acid or chlorine injection may be required.
- Always replace worn nozzles/ emitters/ sprinklers with the exact size and characteristics of the original. Changing sizes changes the overall efficiency of the irrigation system.
Mobile systems (Specific)
Mobile systems are governed by three parameters – Pressure, Flow, and Speed of travel. How fast a system is travelling determines how much irrigation is being applied. Recent studies have shown inconsistent speed calibration results in poor application depth performance. In some instances, up to +/-50% of the desired target depth. Lateral move, centre pivots, hard hose guns, and other mobile system should have a speed calibration check annually to ensure consistent operation. Common issues with speed calibration include:
- Wear and tear of motors and gearboxes
- Deterioration of electrical components
- Incorrect speed calibration at commissioning
- Flat tyres
Wheel ruts are a significant maintenance issue. Not only do deep wheel ruts pose a health and safety issue with on farm vehicles, they greatly reduce the operating life of gearboxes by placing excessive torque forces on output shafts. Some soils are more prone to wheel rutting, but over watering or high application intensities are usually the main causes. Solutions to rutting include:
- Ensure that application depths are within your soils infiltration rate curve.
- Boombacks and directional nozzles greatly reduce the instance of wheel ruts
Irrigator Lane Spacing or Set Spacing:
Travelling irrigators, long laterals, spray-line, and hard hose guns are all designed with ‘Overlap’ – this ensures irrigation is even across the paddock. If the correct ‘Overlap’ is not used the intermediate area between lane spacings will be under or over watered. Solutions for getting lane or set spacing right include:
- The use of lane markers at either end of the paddocks or along fence lines.
- The use of GPS guidance technologies ensures accurate and repeatable placement.