Spray tips wear out and need to be replaced. Although there is a cost in replacing worn spray tips, many contractors continue to use worn spray tips and spend more money on unnecessary waste of the coating.
Four things to consider when it comes to airless spray tip wear.
As the spray tip wears more coating passes through the tip. Unless the operator moves quicker, coating cost per metre has increased.
As the spray tip aperture gets bigger through wear, more pressure is required to create atomisation. More pressure means further increase in flow rate and therefore further increasing the coating cost per metre.
As the spray tip wears the spray fan width reduces. Therefore, more coating is being applied to a smaller area. Again, unless the operator moves quicker, coating cost per metre has increased.
As the spray tip wears the aperture size increases allowing more paint to flow through the tip, at the same time the fan width reduces. Therefore, using a worn tip applies more paint over a smaller area. You will also require more spray passes to cover the same area.
Can we quantify the cost of airless spray tip wear?
Example: – Let’s suppose we are using an airless spray unit; the spray tip is a new 17 thou 50 degree spray angle. Using the known flow rates of the spray tip we could be applying 90 microns coating wet film thickness. As the spray tip wears the flow rate increases. If the spray
tip wears and the aperture becomes 21 thou, without increasing the fluid pressure the coating wet film thickness is now 138 microns.
The spray tip wear from 17 thou to 21 thou represent a 23% increase in aperture. The increased flow rate takes the coating film thickness from 138 microns this represents an increased coating wet film thickness of 53%. Also remember you will need to increase the fluid pressure when the spray tip is worn to achieve atomisation. Therefore, the previous stated 53% becomes 65%. Imagine paying 65% more for your coatings?
Monitoring spray tip wear
Monitoring tip wear can be done by producing an elliptical pattern with a new tip. The optimal spray distance is 12″ from the template. After a few hours of normal production repeat the test. Keep the results to compare the two patterns. If the spray fan pattern has reduced by 20% you need to change the spray tip.
75-100 gallons of paint is about the average life of a spray tip. This is dependent on the abrasive nature of the paint and the fluid pressures being used.
