Maintaining spray nozzle performance

by Christian Canzano

Spray nozzles, like any other equipment, need routine maintenance in order to properly do their job. A consistent spray pattern and complete and uniform spray coverage is very important to the quality of your product.

Frequent inspection of nozzle orifices for clogging is probably the biggest maintenance factor that affects the consistency of spray patterns. Nozzle wear is another important issue that needs to be consistently monitored. Brass, steel and stainless steel nozzles are candidates for corrosion. Plastic nozzles (polypropylene, PVDF, PVC) that carry abrasive materials will wear, but their usefulness can be extended with the proper care.

When spray pattern has degraded
Visual inspection can point to malfunctioning nozzles. An example would be uneven or missing spray patterns where the consistency of the spray (flat fan, full cone or hollow cone) can be seen.

In flat fan nozzles, poor performance will most likely be from a change in spray angle. In hollow cone nozzles, it is common to see a missing pattern in the center or no pattern at all. In full cone nozzles, the nozzle often becomes completely plugged. The most common problems resulting in poor spray patterns include the following.

The worn nozzle
If it’s obvious to the eye that the spray pattern is uneven or incomplete, there’s a good chance the nozzle orifice is worn. A worn nozzle may also be the cause of an unwanted increase in the flow rate, which could be accompanied by a drop in the system pressure and poor spray pattern performance farther from the pump. In extreme situations you could see your electrical costs rise.

To fix
Replace the nozzle.

Prevention suggestions
• Check your fluid temperature. It may be too hot for plastic spray nozzles. Maximum temperature for polypropylene is 175 degrees; 300 degrees for PVDF.
• Reduce spraying pressure to reduce the liquid velocity.
• Minimize the abrasive particle content.
• Consider a different type of nozzle material.

The damaged orifice
An abused and damaged orifice can also result in an irregular spray pattern that can affect product quality and/or waste materials.

To fix
Replace the nozzle

Prevention suggestions
• Do not use metallic objects to clean the nozzle; use fiber brushes, even a toothbrush or toothpick.
• Always remove the nozzle to clean it.

Excessive leaking
Some dripping is normal and usually acceptable in most applications. Check for incorrect connections between the nozzle and the pipe fitting or manifold that could be the fault of an incorrect size being used during nozzle replacement.

If you’re using clip-on plastic nozzles, make sure all components are snapped into place securely. Worn O-rings occasionally cause leaking. Drilling an incorrect size hole will cause substantial leakage, also.

Re-alignment of nozzles
Many quality and efficiency problems are due to nozzles incorrectly aimed after they were removed for cleaning or other maintenance. Few people take the time inside a parts washer or coating compartment to make sure that the orientation of the nozzle is aligned exactly the way it should be, especially if it is in a hard-to-reach area.

With newer quick-disconnect spray nozzles, such as the Bex Zip-Tip, positive re-alignment of the tip is automatic since they are simply twisted into the body until the tip locks into place.

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