Thermal Spray or Metalizing is a group of coating processes which deposits finely divided metallic or non-metallic materials in a molten or semi-molten condition on a surface/substrate to form a coating. The coating material may start out in the form of a powder, ceramic rod, wires, or even molten materials. The process has the potential to generate very small particulate often referred to as “fume”. This thermally generated fume can be smaller than one micron in diameter, and uniform in size making collection a challenge.
Thermal Spray Coating Process
dust collectors are in hundreds of thermal spray applications worldwide. Our advanced Ultra-Web®
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Processes Involving Thermal Spray
The thermal spray processes involves such heat that the process produces a very fine dust (fume), typically sub micron in size and very uniform. Some of the materials used in thermal spray applications have associated adverse health effects, and defined minimum exposure limits set for them, which necessitates effective dust collection.
Following are terms for typical thermal spray processes that produce fumes needing to be controlled;
||Powder Flame Spray|
|Wire Flame Spray
High Velocity Oxy/Fuel Spraying (HVOF)
||Plasma Arc Spray|
|Electric Arc Spray
related processes producing contaminants—surface preparation and finishing operations
Many metal fume dusts are combustible and those operations generating or handling metal fumes can require special mitigation efforts to minimize fire and explosion risks. Standards such as NFPA 654 can provide guidance for those who generate and handle these types of dusts. See the Donaldson Dust Collectors and Combustible Dust Strategies brochure.
Metal fume dusts may also have identified adverse health impacts, and special mitigation strategies may be required to limit occupational exposure below levels OSHA or other health organizations have established for these materials.
LEGISLATION (OTHER FEDERAL AND LOCAL LEGISLATION MAY APPLY)
Particulate Matter (PM):
- PM 2.5 = 15 µg/m3 (annual), and 35 µg/m3 (24-hour)
- PM 10 = 150 µg/m3 (24-hour)
National Emissions Standards for Hazardous Air Pollutants for Plating and Polishing Operations contains language related to thermal spray processes containing cadmium, nickel, lead, manganese, and/or chromium.
- Directive CPL 03-00-013: National Emphasis Program – Primary Metal Industries May 19, 2011
- Directive CPL 02-02-076: National Emphasis Program – Hexavalent Chromium Feb 23, 2010
- Directive CPL 03-00-008: Combustible Dust National Emphasis Program (Reissued) Mar 11, 2008
- 29 CFR 1910.1000 - Air Contaminants
NOTE: Twenty-five states, Puerto Rico and the Virgin Islands have OSHA-approved State Plans and have adopted their own standards and enforcement policies. For the most part, these States adopt standards that are identical to Federal OSHA. However, some States have adopted different standards applicable to this industry or may have different enforcement policies.
Industrial Ventilation Manual
NIOSH Publication No. 76-179