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Dripping Nozzles: Diagnosis and Troubleshooting
A nozzle drips when the pressure in the tubing is in a range where it is too low for the nozzles to atomize the fluid through the orifice but too high for the check valve in the nozzle to close.
How it should work:
At the end of a mist cycle, when the controller stops the motor (and pump), the pressure in the line is relieved by a small amount of fluid flowing back through the auto-drain elbow into the tank. Because the fluid is incompressible, not much fluid has to leave the lines for the pressure to fall. The pressure should decay very quickly and minimize the time spent in the pressure range that causes nozzle dripping.
Scenarios that can induce dripping:
- The check valve in the nozzle is working as it should, but the pressure in the nozzle circuit isn’t decaying quickly. Something is restricting the fluid from traveling back into the misting unit through the auto-drain valve to relieve the pressure. The most common causes are:
- There is a kink in the line between the unit and the dripping nozzles
- The drum cover causes kink a in the nozzle circuit line that restricts flow
- The agitation valve closed if HOLD time is too short
- The agitation valve has failed and is only partially opening. If this is the cause, the unit would mist while in agitation mode.
- A check valve has been installed in the line (not necessary with our system).
- The pressure in the nozzle circuit is decaying quickly, but there is something wrong with the internal check valve of the nozzle, causing it to stay open at a pressure that it is designed to close at. Possible causes for this phenomenon are:
- The valve is not aligned with the orifice and cannot seal it. This can be due to grit/dirt getting jammed internally or swelling/distortion of the check valve (caused by incompatibility between the insecticide and the seal material).
- The spring of the internal check valve is too light
The best way to test is to install an in-line pressure tester next to a dripping nozzle and mist the unit. When the unit ends the mist cycle, observe the pressure decay on the gauge at the same time you watch the nozzle. The pressure in the line should drop from an operating mist pressure (230 – 250 psi) to around 30 psi within 1 – 2 seconds. Visibly, the nozzle should go from atomizing to off during that period. From there, it should take a further 5 seconds for the pressure to decay to 5-10 psi.