Powder Booth Maintenance

By J.R. Rogers

When it comes to a powder coating application system, I think of the powder booth as the heart of the system. Everything else works around it and with it, and if it is not functioning properly neither will any of the other components. It is important to complete preventive maintenance to keep it functioning as designed.

Let’s review the basics of how a booth functions, the components of the booth, and which components need regular inspection/maintenance.

The first and main function of any powder booth is powder containment, regardless of its type. Whether a simple small open face lab booth, an enclosed batch booth, or an in- line fast color change booth, the booth is designed to contain the powder within its enclosure. Maintenance is key!

So, how does a powder booth contain the powder within its walls? Essentially the powder booth is a large vacuum. The enclosure is connected to a powder collection system which creates negative pressure (vacuum) within the enclosure— typically 100-150 feet per minute at the openings. If the booth doesn’t contain the powder within the enclosure, in most cases it is the result of lack of maintenance which can cause the filters to plug up and not pull the correct amount of air from the booth.

Now let’s break the booth down into the components.

Enclosures
Regardless of type, the enclosure design should include smooth walls with no ledges and smooth floors that are easy to clean. Both minimize powder accumulation.

Booths without self-cleaning floors need to have scheduled powder removal, typically every hour or two depending on how many guns are spraying. In booths with self-cleaning floors, the floor should be kept clean automatically, although small accumulations are not uncommon. If you see a buildup of powder on the floor, or a section of floor with more powder than the other sections, it is time find out why. Two common reasons are, a solenoid is not working correctly, or there is something on the floor that the powder is sticking to.

The walls and floor should be smooth in a non-conductive booth. Over time these surfaces can become scratched, which can cause powder to build. Polishing to smooth the surface will help eliminate powder build. However, please take caution when choosing a polishing compound to prevent a contamination issue.

Lighting should be bright so the operator can see the target, allowing efficient coating of the part, both in the automatic and manual application areas of the booth. Causes for poor lighting include powder accumulation between the light fixture and booth as well as the polycarbonate light fixture becoming frosted. Regular housekeeping is required along with some maintenance to keep lighting in good shape. In addition, bulbs or fixtures that are not working properly need to be replaced.

Powder Collection Systems
All powder collection systems will include a powder filtration/separation system, fan, and motor. The powder filtration/separation system is where the powder is separated from the air. There are typically three types of filtration systems used.

Pocket filters, which are not self-cleaning, require a great deal of maintenance to keep them functioning as designed. In many cases there is a 2:1 ratio of spray time to maintenance time to keep the booth functioning properly.

To clean the filters, they must be removed and blown/ vacuumed to remove the collected powder. This is both time consuming and messy. Having a second set of filters on hand allows you to switch out dirty filters with clean ones and enables cleaning while the booth is operating. It is not uncommon for powder to get past this style of filtration system, which can lead to powder contamination of the area.

Cartridge collectors (open faced or enclosed) are self- cleaning and a great choice for powder coating as they are able to continuously maintain the desired static pressure of the filter and the airflow within the enclosure with very little maintenance (see Figure 1). Only pressure monitoring is required. Once the maximum recommended static pressure is reached, replace the filters. Attempting to clean is not recommended and can cause damage to the filters which will lead to powder leaking through.

Pulse valves or solenoids that are not working as designed can cause poor to no cleaning of the filters. Listen as the filters are pulsed; if you hear one or more pulses that are weak or missing, it is time to maintain them.

If your static pressure is too low and new filters were recently installed, they must be seasoned before they begin operating within the designed range. Also check for a damaged filter which may be allowing powder to leak through and contaminate the area.

Cyclones are used in conjunction with enclosed cartridge collectors. The cyclone separates the powder from the air prior to reaching the cartridge collector (see Figure 2). By doing so it can greatly increase the life of the filter as the collector and filters are separating less powder. It is very important that the collector is operating as designed as the airflow through it impacts the efficiency with which the cyclone separates the powder from the air.

There is very little maintenance required for the cyclone itself. There is a powder pump at the bottom of the cyclone to remove the powder and send it to the reclaim system. Maintain the pump as recommended by the manufacturer.

All of the collection systems need to have filtration monitoring gauges. They provide an indication of the static pressure (resistance across the filter) as a minimum. In many cases the system will have automatic monitoring that will shut the system down if the static pressure is too high or too low. Be sure to refer to the manufacturer recommended static pressures for normal operations.

If the static pressure is higher than designed, the airflow within the booth will be reduced, enabling powder to escape the booth. If the static pressure is low, there may be an issue with a missing or damaged filter that will allow powder to pass through the filter and contaminate the area.

The last component is compressed air as it is used to fluidize the powder, pump the powder, and clean the cartridge filters. If it has any particle contamination, moisture, or oil, it will dramatically reduce the filter life and negatively affect your powder coating system. It is extremely important to have a good air dryer with a coalescing filtration system for any powder coating system.

Please treat preventive maintenance as the heart of your powder system—just as you should for you own heart. Skipping preventive maintenance will have a negative impact on the function of your entire system.

J.R. Rogers is engineered systems national sales manager, industrial solutions at Wagner Systems Inc.