CHEMIGATION CALIBRATION - KEEP IT SIMPLE
Franklin Laemmlen
 Calibrating chemigation applications into irrigation systems can be accurate and easy when using the correct components. Use the chart below to select the TeeJet Orifice Plate for the desired GPH. The only change for different applications will be the acres treated and total amount of material added to the solution.
Avoid the lower GPH rates, as the orifice opening is smaller and prone to plugging, and requires the solution be concentrated, making the flow meter hard to see. Needle valves are supposed to make adjustments easy, but they require constant adjustment to keep the rate the same.
Here’s a list of common calibration components when doing a chemigation application:
- 80 to 100 gallon tank
- Diaphragm pump with filter and with good return flow for by-pass agitation
- Pressure regulator with by-pass and pressure gauge (high side) with an on/off valve
- TeeJet Nozzle Body for strainer and orifice plate. Note: Always insert the orifice plate with the side marked with number facing the outlet
Optional: By-pass route around nozzle body to quickly rinse tank into the irrigation system when application is completed.
- Pressure gauge (low side) on irrigation side: high side minus low side equals operating psi
- Flow meter to check flow rate at any moment - "look and see"
Open needle valve wide open, if one is installed.
Equivalent
| GPM | GPH |
| 0.333 | 20.0 |
| 0.417 | 25.0 |
| 0.500 | 30.0 |
| 0.833 | 50.0 |
| 1.000 | 60.0 |
| 1.250 | 75.0 |
TeeJet Calibration Chart - Adjust PSI to Obtain GPH
| Selected Orifice Plate No. | 20 psi | 30 psi |
| GPM | GPH | GPM | GPH |
| CP4916-61 | 0.330 | 19.8 | 0.404 | 24.2 |
| CP4916-68 | 0.405 | 24.3 | 0.496 | 29.8 |
| CP4916-75 | 0.491 | 29.5 | 0.601 | 36.1 |
| CP4916-95 | 0.808 | 48.5 | 0.990 | 59.4 |
| CP4916-107 | 1.040 | 62.4 | 1.270 | 76.2 |
| CP4916-120 | 1.260 | 75.6 | 1.540 | 92.4 |
Be sure to install appropriate chemigation equipment as specified on the label. Use the sequential injection method as recommended for materials applied. Remember: Uniformity and Placement.
Always read and follow product label recommendations.
Information is reprinted from a bulletin distributed by Ed Ishida, Bayer Corporation.
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