Powder Sticking to Safety Glass

Question:

I have a question regarding powder sticking to safety glasses. Many of our sprayers prefer not to wear glasses while they are manually spraying powder because the powder is drawn to the glasses and they cannot see. They also build up static, which could cause sparks and then perhaps a fire in the booth. I am wondering if there are any special glasses that powder coat sprayers can get. Maybe some kind of anti-static or something. I’ve checked at a lot of National Safety Glass Manufacturers and I couldn't find anything. D. M.

Answer:

Plastic safety glass lenses are non-conductive and should not attract much powder. Charged powder particles are primarily attracted to grounded surfaces, although they can be attracted to ungrounded surfaces to some extent. Some spray cleaners will neutralize the surface of the safety glass lens and should reduce the problem. Check with your safety glass supplier for an appropriate cleaner.

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As for the static buildup, I would worry more about the operators being properly grounded. Normally they are grounded through the touch-up gun handle. However, if they wear gloves, this source of ground is not present. In the cases where the gun handle cannot be used as the primary ground, I recommend using leather-soled shoes or in some instances grounding straps. In any case, the operators must be grounded as required by NFPA 33 rules and guidelines.

I would not worry about the safety glasses discharging as a point of ignition for the powder within the booth. For that to happen, the operator’s face would have to be directly in the powder stream from the gun (where there is enough powder to ignite). That situation is not very likely during normal operations unless your operators coat parts with the gun in their mouth pulling the trigger with their tongue. If that is the case, you have more serious problems with your plant personnel than powder buildup on their safety glasses.

However, if the operators are ungrounded, the situation could be much worse. They could discharge in the vicinity of a powder cloud and cause a fireball. This is definitely an unpleasant experience. That’s why there is no substitute for proper operator grounding while spraying.

Since powder coatings can cause eye irritation, I would recommend that your operators still use their safety glasses and just clean them frequently. If that becomes too bothersome, look into face shields. However, considering the weight and restricted vision of face shields, I suspect that they will still use their safety glasses. Oh by the way, don’t forget to insist that the operators use dust masks when spraying powder coating.