Technical Answers

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Powder Coating Safety

Powder Coating Safety

Virtually every industrial process involves some hazard to persons and property. Solvents used in conventional paints present a fire hazard. The possibility of organic dust fires and explosions exist in powder coating. (organic)

 

Safe and efficient operation of an electrostatic powder coating system is based on these fundamental rules.

  1. Maintain a powder-air concentration (M.E.C.) of the powder being sprayed.

    1. Air flow through a powder coating booth and recovery system should be sufficient to ensure that the maximum powder concentration will never exceed 50% of the M.E.C. (Organic)

  2. Eliminate all potential sources of ignition.(organic)

    1. Do not permit smoking in the vicinity of any component of a powder coating system.

    2. Guns should have a built in safety device which positively limits their output current and simultaneously folds back current when that limit is reached.

    3. All equipment, spray booth, conveyor, hangers, work pieces, ducting and powder recovery units must be permanently grounded to prevent the build up of static charge.

    4. Codes dictate that the resistance to ground of conveyors and hangers to be one megohm or less.

    5. Lights should be located outside the coating booth. Any lights or electrical equipment located inside the booth or within 3 feet of an opening of the booth must be explosion proof.(organic)

    6. Do not store combustible materials near any portion of the powder systems.

      3.  Incorporate and maintain appropriate safety features in the system.

  1. Powder recovery units, such as filters and cyclones, should be pressure relief vented.

  2. All powder recovery filters should be equipped with differential pressure instruments.

  3. Exhaust fans should be of spark proof and dust ignition proof construction.

 

  1. An infrared fire detection system is recommended. Fire detection is mandatory with automatic guns.(organic)

  2. All systems should have interlocking controls so that the malfunction of any component will shut down the entire system.


Notes

  1. Air flow through the coating booth should be sufficient to prevent the drift of powder from the booth.

  2. Spilled powder should be cleaned up immediately.

  3. Check air line filters and traps regularly to insure good air quality.

  4. Check system safety devices regularly to insure proper function.

  5. Inspect electric motors to make sure they are not overheating.

 

 SUMMARY

 

 Safe operation of a powder coating system is based on recognition of the possible hazards and a common sense approach to system operation and maintenance.

 

 The following “Do’s and Don’ts” are offered as a guide to operators and supervisors.

DO:

  1. Check operation safety devices and interlocks regularly.

  2. Check for leaks and abnormal pressure drops across filters.

  3. Check sieve in the automatic recovery system.

  4. Check ground connections regularly, including ground between workpiece and hangers.

  5. Lubricate electric motors regularly and check for overheating.

Rough clean booth daily with squeegee and vacuum cleaner. Clean thoroughly every week.

  1. Clean and drain compressed air filters regularly. Replace as necessary.

  2. Strip hangers regularly.

  3. Remove foreign objects which may fall into the booth immediately.

DON’T:

  1.   Spray powder with booth exhausters off.

  2.   Let spray guns approach grounded objects.

  3.   Permit foreign objects to remain in the booth.

  4.   Permit smoking in the area.

  5.   Let powder accumulate anywhere.

  6.   Permit fan motor bearings to become contaminated with powder.

  7.   Use recovery system hoppers to be used as storage reservoirs.

  8.   Clean spray booth with rags and brushes.

Powder Coating Terms

Back Ionization

  • An excessive build up of charged powder particles which may limit further powder being deposited on the substrate.  The electrical charge on the surface layer may be reversed, repelling additional powder.

Bulk Density

  • Mass per unit of volume in powder form including the air trapped between particles

Cartridge Filter

  • A cylindrical filter unit used to separate over-sprayed powder from air for recovery and reuse

Corona Charge

  • The process of inducing a static electric charge on powder particles by passing the powder through an electrostatic field generated by a high voltage device.

Cure Schedule

  • The time/temperature relationship required to properly fuse a powder coating

Cyclone

  • A type of recovery unit using a centrifugal process to separate over-sprayed powder particles from air flow.

Delivery

  • The process of moving the powder through the application equipment to the end product

Edge Coverage

  • ​A powder's ability to flow over, build and adhere to sharp corners, angles, and edges

Faraday Cage Effect

  • A condition that may exist on a substrate due to its geometric configuration that may inhibit the electrostatic deposition of powder particles at a specific localized area.

Film Formation

  • The forming of a continuous film by melting powder particles and fusing them together by the application of energy.

Fluidizing

  • The process of suspending  the powder in a continuous stream of air giving it "Fluid" characteristics.  Used to facilitate transfer of the powder to the application device.

Fusion

  • The melting and flow of individual  powder particles when heated to form a continuous film.

Grounding

  • The reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.​

Impact Fusion

  • The combining of powder particles to form a solid mass during the delivery and application process.

Lower Explosive Limit (LEL)

  • The lower point for a range of concentrations of organic particles suspended in air which can be ignited  by a sufficient energy source.

Micron/Mils

  • Common unit of measurement of coating thickness.  25.4 μ (microns or micrometers) = 1 mil (one thousandth of an inch)

Particle Size

  • Average diameter of an individual, irregular powder particle

Recovery

  • The process of removing non-deposited powder from the air prior to reclaiming it for reuse.

Spray Booth

  • A specially designed enclosure in which powders are introduced, contained and recovered during the coating process.

Surface Appearance

  • Generally refers to the smoothness and gloss of powder coating films and the presence and degree of surface defects.

System Utilization or System Efficiency

  • The combined efficiency of each component in the powder coating system resulting in total material usage compared to the amount of material entered into the system.

Transfer Efficiency

  • The ratio of the powder deposited on the work-piece compared to the amount of powder sprayed during a fixed time period.

Tribo Charging

  • Process of creating a static electrical charge on powder particles by creating friction between them and a non-conductive material.

Virgin Powder

  • Powder that has not been previously sprayed as opposed to reclaim powder.

Wrap

  • A characteristic of electrostatic application for the powder to seek out and adhere to parts of sight of the delivery point.