Fluid is dripping from nozzles
Unist spray systems use a variety of different nozzles and methods to carry air and fluid from a pump to the nozzle. One common way to deliver fluid and air to a nozzle is coaxially with a small hose (capillary), which carries fluid inside of a larger hose that carries the air separately to the nozzle where they are mixed at, or just before, the nozzle tip. There are different design nozzles, but most of them work under the same/similar principles.
In normal operation, the fluid in the capillary will remain in place as long as the capillary has no cuts/tears/abrasions, and it is properly sealed to the barb fitting on the outlet of the pump. If the capillary has even a minor cut or tear or is not properly sealed on the pump barb fitting, then fluid will drain from the capillary and eventually the nozzle tip. Typical causes of capillary issues stem from disconnecting and reconnecting and/or shortening coax hose. Care must be taken not to nick or damage the capillary tube. If it is being reinstalled onto the barb fitting on the pump, it is highly recommended that the end of the capillary that had been installed on the barb fitting be trimmed off so a clean new section of capillary can be installed onto the barb.
The brass barb fitting on the pump outlet can also accidentally be damaged when removing capillary from it. It is never recommended to use a blade to cut along the axis of the capillary to remove it from the barb. Doing so can damage the barb and not allow the capillary to seal properly. The barb can also be damaged if pliers are carelessly used to pull the capillary from the barb fitting.
Helpful tips for working with coaxial tubing can be found in the related video.
If the capillary is determined to be in good condition and there are no issues with the seal on the pump barb fitting, then the next possible cause of fluid dripping from a nozzle is a compromised outlet check seal internally in the pump. This can occur from either dirt/debris getting onto the outlet check seal, a damaged outlet check seal, or if the face that the check seal seals is damaged. Any of these conditions will require full pump disassembly. Contact Unist support for further assistance with this condition.
One other potential cause for fluid dripping from a nozzle is if the system is fed from a pressurized fluid supply with excessive pressure. The pumps can be supplied with 5-10 psi of pressurized fluid. Excessive fluid pressure can push the outlet check seal of the pump open and force fluid out of the pump without the pump running.
Due to their construction, it is normal to observe a few drips from a Coolubricator™ nozzle after it has been shut off especially if the nozzle is oriented downward.