In powder coating areas, high humidity causes improper particle deposition,
irregular film thickness, operational problems in spray guns, caking
or agglomeration (clustering) of the powder particles and has a measurable
negative effect on powder resistivity. In severe cases, powders exposed
to high humidity, cannot deposit at all.
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Powder Coating have opened a new horizon in the product finishing
industry all over the world providing the user improvements in coating
quality, efficiency and economy. Powder coating permits the paining
of objects by spraying a dry product with no solvent, thereby avoiding
pollution of the water or the atmosphere. From an economical standpoint,
overspray or excess powder can be reclaimed through a recovery system
and reused.
The Process
Efficiency and reliability of
Powder Coating is mainly a function of the compulsory control of
the interactions between the product to be applied i.e. its chemical
composition and the various elements e.g. charge decay of the equipment
operating under the surrounding conditions of the application.
Relative Humidity and temperature directly
affect the practical application achieved. However, in most powder
coating spraying facilities, these surrounding conditions are not
controlled.
Effects of Humidity
Humidity has a direct relationship with ion charge decay, particle
deposition, regularity of deposited thickness, adjustments required
of the operating conditions of the spray guns, caking or agglomeration
(clustering) of the powder particles and have a measurable negative
effect on powder resistivity. High humidity may cause the powder
particles to stick to the corona electrode and thus quench the corona.
In severe cases, powders have been exposed to high humidity, cannot
deposit at all.
Bry-Air Solution
Utilization of Bry-Air Dehumidifiers and environmental systems accomplishes
complete control over both relative humidity and temperature within
the powder spray booth area and often the entire coating room.
The advantages stem from two
basic points-
- Lower humidity will provide the ideal environment for the powder
particles to sustain their charge prior to impact with the target.
- Since most powders are hygroscopic to varying degrees, high
humidity will cause agglomerates to form on the walls of the recovery
duct, filters and tubing. The filter bay house becomes less efficient
requiring frequent attention.
The Advantages
- Upto 15% less powder is required - due to uniform control
of film thickness and reduced losses from powder coating buildup
and agglomerates.
- Increased control over film thickness-
by controlling the electrostatic field more precisely, the ability
to coat the target more uniformly is achieved (particle deposition
coupled with long term ion decay)
- Increased system fluidising
- the recovery system works nearer its peak performance level
due to reduced powder buildup in the duct, filter and tubing.
- Reduced Agglomeration - dehumidified
air reduces the powder's ability to adhere to the inside surfaces.
- Reduced spray gun buildup - a
noticeable, marked improvement in quality
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