Powder Coating Q&A: What are my Powder Booth Options?

Q. We just began to look at powder coating booths and other equipment. I see a lot of different styles of powder booths and I am not clear on how to compare them. We do not see a lot of volume in powder, but we want to handle large parts. Some of the booths we have looked at have fairly simple filtration and look similar to our liquid paint booths. Others have cartridge systems and do not appear to exhaust out of the building. Can you tell me a little about what to look for and what might be best?

A. Some booths are designed for batch operations and some are designed for a conveyorized system where a rail runs above the booth and the parts pass through for coating. You do not anticipate a lot of volume, so let’s consider batch options first. The simplest batch booth uses three layers of filtration. Inside the booth there is a blanket filter with a pocket-type filter behind it. The blanket catches most of the powder and the pocket filter makes sure that very little particulate passes up to the fan area. The final layer of filtration is on the discharge of the fan housing. That filter is a high efficiency particulate arrestor (HEPA)-type filter, which is designed to ensure that powder is not discharged back into the plant. The booth itself is a sheet metal shell that provides an enclosure around the application space. A fan pulls air toward the filters and then returns that air into the plant through the HEPA filters. This is the least expensive option. The downside is that the filters build up with powder and have to be changed and the frequency of change depends on the volume of powder sprayed in the booth. This is not a good option for higher production rates because the filters have to be replaced often.

The next step in the batch world is a booth shell with cartridge modules for powder containment and capture. Instead of the three-stage filtration described above, the air is pulled through a fine-media cartridge that captures the powder particles and then the air is discharged back into the plant through a HEPA filter. The advantage is that the filters are continuously cleaned with compressed air pressure, so they do not load up quickly, and the airflow remains sufficient for a long time. Though these booths cost more, the filters will last for 6 to 18 months, depending on use. Both batch systems can collect powder, but neither is designed for powder recovery and reuse.

Systems designed for conveyorized operation may also use a cartridge module to reclaim powder. The shell can be sheet metal or some type of thermoplastic material. All of the overspray is captured for scrap or reuse, but the limitation is that a roll away module is required for every color you choose to recover. One module is good for one color or a non-recovery operation where all powder is scrapped.

Another option adds a cyclone to the air extraction system. The fan pulls the powder-laden air into a duct and spins it centrifugally in the cyclone. Most of the powder is reclaimed in a hopper at the foot of the cyclone. A small percentage (usually 3 to 5 percent) is pulled through the cyclone and into the cartridge collector at the end of the duct run. That powder is scraped. The cyclone pulls some powder to waste, but it does not need additional modules to recover additional colors. It can also be fitted with specialized features to facilitate faster color change. It is typically more expensive than a cartridge system unless several modules are needed with the module system for recovery of powder for reuse. 

 

Originally published in the May 2016 issue.