Fire Detection

Do I need fire detection for my manual powder gun and booth?

Every company must comply with the local authority having jurisdiction and follow the local codes and laws in place. For most companies, the local authority relies upon the National Fire Protection Agency (NFPA) guidelines as a source of information. According to NFPA 33 Standard For Spray Application Using Flammable or Combustible Materials, 2003 Edition, when automatic powder spray guns are used, whether liquid or powder, optical flame detection is required. Furthermore, this equipment must activate several devices within 0.5 sec of detecting the presence of a flame. This process is further described in NFPA 33, Chapter 9. However, your question is regarding manual powder coating. When manual powder coatings guns are used, optical flame detection is not required. The logic is that when the operator sees any presence of a flame, the natural instinct is to release the trigger and stop coating. By releasing the trigger, the supply of powder is stopped and the flame cannot be sustained unless a specific powder-to-air concentration exists. Powder accumulated on the booth floor and walls will not burn unless it becomes airborne in the right concentration of powder and air.

Additionally, some spray gun manufacturers sell equipment that has been approved by Factory Mutual Research (FM), an independent testing agency that puts equipment through a series of tests, to ultimately receive FM approval as a non-incendive device. This means that these powder coating guns cannot generate enough energy to produce a spark that would ignite the powder coating material. Guns with the FM approval are considered very safe to use in a powder coating environment.

In any case, you should follow the recommendations of the local authority having jurisdiction, and, if necessary, consult with the manufacturer of your spray gun and booth for more information.

Automation Options

We currently feed fresh powder to our hopper by hand with a scoop. We would like to automate the process and we were wondering what options are available for transfer of powder from the box to the feed hopper?

Most powder equipment companies offer units for moving powder from the shipping container into the powder process. You can contact your equipment supplier and they will be able to provide you with information on their particular models. To help you understand what is generally available, I will review the typical units sold.

First you need to decide if you are going to manually or automatically activate the transfer process. Although the powder will be transferred using the fresh feed unit, manual activation requires a person to flip a switch or turn a valve to complete an electrical or pneumatic circuit. Once this occurs, the unit will transfer powder until the container is empty or the operator turns off the unit. Typical problems are: forgetting to turn the unit on and running the hopper empty or the opposite forgetting to turn the unit off and overfilling the hopper. Either way, manual intervention is required.

The other method is to automate the replenishment of your fresh powder by using level sensors in the hopper. These sensors will determine the level of powder in the fluidized hopper and at the appropriate time activate and turn off the fresh feed unit.

One of the more common designs for fresh feed units utilizes a vibratory table to activate the powder, and transfer pumps that incorporate a fluidizing air at the suction tube pickup point. No matter what kind of container - 300 lb. drum, 1,500 lb. box or 2,000 lb. bag - each equipment manufacturer has a unit designed to transfer the powder into your coating process.