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ChemigationChemigation
Guy Fipps – Extension Agricultural Guy Fipps – Extension Agricultural EngineerEngineer
• Administrative Rules of the Texas Administrative Rules of the Texas Department of Licensing and Department of Licensing and Regulation (TDLR):Regulation (TDLR): Chapter 76 – Chapter 76 – Water Well Drillers and Pump InstallersWater Well Drillers and Pump Installers
Requirements - Chemical Requirements - Chemical Injection, Chemigation, and Injection, Chemigation, and Foreign Substance SystemsForeign Substance Systems
TDLR Chapter 76.1007TDLR Chapter 76.1007
All irrigation distribution systems All irrigation distribution systems … into which any type of … into which any type of chemical … or other foreign chemical … or other foreign substances will be injected into substances will be injected into the water pumped from wells the water pumped from wells shall be equipped with an in-line, shall be equipped with an in-line, automatic quick-closing check automatic quick-closing check valve capable of preventing valve capable of preventing pollution of the ground water.pollution of the ground water.
Check ValveCheck Valve
• Body constructed of:Body constructed of:– Cast ironCast iron– Stainless steelStainless steel– Cast aluminumCast aluminum– Cast steelCast steel– Material and design of sturdy integrityMaterial and design of sturdy integrity
• Materials should be corrosion Materials should be corrosion resistant or coated to prevent resistant or coated to prevent corrosioncorrosion
Check ValveCheck Valve
• Valve working pressure rating Valve working pressure rating shall exceed the highest pressure shall exceed the highest pressure to which the valve will be to which the valve will be subjectedsubjected
• Valve shall be installed between Valve shall be installed between the pump discharge and the point the pump discharge and the point of chemical/foreign substance of chemical/foreign substance injectioninjection
Other Required Devices Other Required Devices Installed between the pump Installed between the pump
discharge and the check valvedischarge and the check valve
An irrigation system which adds An irrigation system which adds any chemical with any kind of any chemical with any kind of injection device associated with injection device associated with it has a potential for introducing it has a potential for introducing toxic substances into the water toxic substances into the water supply and is, therefore, supply and is, therefore, considered to be a "high health considered to be a "high health hazard" installation. hazard" installation.
Proposed RevisionProposed Revision
Such an irrigation system must not Such an irrigation system must not be connected to any potable be connected to any potable water supply except through an water supply except through an industry-approved "high health industry-approved "high health hazard" backflow prevention hazard" backflow prevention device, such as an appropriate device, such as an appropriate pressure-type vacuum breaker pressure-type vacuum breaker backflow preventor or a reduced backflow preventor or a reduced pressure principle backflow pressure principle backflow prevention assembly.prevention assembly.
Proposed RevisionProposed Revision
The backflow prevention The backflow prevention assembly must be tested assembly must be tested upon installation and, at upon installation and, at least, annually, thereafter, in least, annually, thereafter, in accordance with §290.44(h)accordance with §290.44(h)(4) of this title (relating to (4) of this title (relating to Water Distribution).Water Distribution).
• Protects against back-Protects against back-siphonage & back-pressuresiphonage & back-pressure
• Can be under constant pressureCan be under constant pressure• Must be 12 inches above gradeMust be 12 inches above grade• Must be tested upon Must be tested upon
installation and annually if in installation and annually if in high hazard applicationshigh hazard applications
RPBARPBA
• Installed horizontallyInstalled horizontally• 4 test cocks4 test cocks• 2 shut off valves2 shut off valves• At least 2 (psi) zone pressure At least 2 (psi) zone pressure
The process of injecting an The process of injecting an approved chemical into approved chemical into irrigation water and applying it irrigation water and applying it through the irrigation system through the irrigation system to a crop or field.to a crop or field.
Advantages of Advantages of ChemigationChemigation
• Uniformity of applicationUniformity of application• Precise applicationPrecise application• EconomicsEconomics• TimelinessTimeliness• Reduced soil compaction and Reduced soil compaction and
Disadvantages of Disadvantages of ChemigationChemigation
• High managementHigh management• Additional equipmentAdditional equipment
The US EPA’s Label The US EPA’s Label Improvement Program Improvement Program
(LIP)(LIP)• Effective April 1988Effective April 1988• Labels must state whether Labels must state whether
product is approved to be applied product is approved to be applied through the irrigation systemthrough the irrigation system
• Application instructions are Application instructions are providedprovided
• Requires use of specific safety Requires use of specific safety equipment and devices designed equipment and devices designed to prevent accidental spillsto prevent accidental spills
Example LabelsExample Labels
Summary of Summary of Chemigation Equipment Chemigation Equipment
RequirementsRequirements
1. Irrigation Pipeline1. Irrigation Pipeline
• Check valve between well and Check valve between well and injection points*injection points*
• Vacuum relief valve between Vacuum relief valve between check valve and wellcheck valve and well
*Alternative safety equipment may be *Alternative safety equipment may be substituted substituted approved by EPA, March 1989.approved by EPA, March 1989.
• Normally closed solenoid valve Normally closed solenoid valve between injection pump and between injection pump and chemical tank*chemical tank*
• A metering type injection A metering type injection pump*pump**Alternative safety equipment may be *Alternative safety equipment may be substituted substituted approved by EPA, March 1989.approved by EPA, March 1989.
3. Power Interlock3. Power Interlock
• Interlock injection pump and Interlock injection pump and water pump powerwater pump power
• Interlock normally closed Interlock normally closed solenoid valve and injection solenoid valve and injection pump powerpump power
Management Practices Management Practices for Chemigationfor Chemigation
• Flushing injection systemFlushing injection system• Flushing irrigation systemFlushing irrigation system• MonitoringMonitoring• Calibration checkCalibration check• Chemical compatibilityChemical compatibility• Prevent runoffPrevent runoff• Prevent application to surface Prevent application to surface
Discharge flow rate will not change Discharge flow rate will not change as the irrigation pipeline pressure as the irrigation pipeline pressure variesvaries
• Flow rates cannot be adjusted Flow rates cannot be adjusted while operating while operating
• Used to inject fertilizerUsed to inject fertilizer• Not easily adjusted for insecticides, Not easily adjusted for insecticides,
fungicides and herbicidesfungicides and herbicides
Diaphragm PumpsDiaphragm Pumps
Discharge flow rate not constant Discharge flow rate not constant with significantly varying with significantly varying
discharge pressuredischarge pressure
• Easy to adjust flow rate while Easy to adjust flow rate while operating operating
• Zero leakageZero leakage
Venturi MetersVenturi Meters
Variations in flow rate from the water Variations in flow rate from the water supply will change the rate of supply will change the rate of
injectioninjection
• Reduced diameter throat tubeReduced diameter throat tube• Velocity changes in throat create Velocity changes in throat create
vacuum to pull chemical into streamvacuum to pull chemical into stream• Requires additional hardware for Requires additional hardware for
injectioninjection
Important Important CharacteristicsCharacteristics
Chemigation Pumps & Chemigation Pumps & ComponentsComponents• Accuracy to within + or – 0.5 Accuracy to within + or – 0.5
percentpercent• Calibration tubeCalibration tube• Adjustable while runningAdjustable while running• Durable – stainless steel valve ballsDurable – stainless steel valve balls
– Niton seals – Niton seals • Agitation capabilityAgitation capability• Accessibility of repairsAccessibility of repairs• Appropriate size chemical Appropriate size chemical
tank/tankstank/tanks
Calibration of Calibration of EquipmentEquipment
• Small differences in injection Small differences in injection rates make large differences in rates make large differences in total amount of chemical appliedtotal amount of chemical applied– Results in insufficient or excessive Results in insufficient or excessive