It is quite important that the air or gas used for Cold
Spray be clean and dry. This is mainly necessary to
maximize the life of the high-power heater core. It also
ensures that there is no clumping of the feedstock
powder due to moisture. Clean carrier gas also reduces
the chance that the deposition efficiency will be
negatively impacted by feedstock powder contamination
such as oil, oxides, or rust. It also ensures that the
applied coating or the substrate will not become
contaminated during the spraying process.
Our recommendation is
that a 2 micron filter be used and that the carrier gas
has a -40°C
dew point. This is a little drier than the standard -33
°C rating
common air preparation equipment might have. Because
commercially available compressed gas such as Nitrogen
(N2) is substantially under this dew point
there is no issue with contamination or dew point as
long as contaminants are not introduced into the system
downstream of the bottle or tank.
Cartridge filters
Cartridge filters are comparatively low cost but they
require maintenance. Usually a pre-filter of between 20
and 5 microns is used to remove the bulk of moisture and
contamination. This improves the service life of the
cartridge filter. As the filter cartridge becomes
burdened with contamination the output flow rate will
decrease. Routine maintenance is necessary to ensure
that the process efficiency will not be impacted by the
flow rate decline.
Membrane filters
Membrane filters require less maintenance than cartridge
filters because the membrane does not trap
contamination, it isolates it from the downstream
system. Typically, these devices are self-cleaning by
either gravity or an active process. It is common for
membrane filters to consume about 5 m3/h (3
SCFM).
Refrigerated Drier
It is possible to also use a refrigerated compressed air
drier to eliminate moisture from the incoming air. You
may already have a refrigerated drier as part of your
air compressor system but, if you check you may find
that the drier wouldn’t be set, or perhaps capable, of
getting the air dry enough.
To eliminate a
lot of hassle with putting such a package together,
CenterLine offers an Air Preparation Package that
consists of
20 and 2 micron filters,
plus two 22 SCFM membrane filters in parallel. These
components are mounted on a cart with a 20 gallon surge
tank. Please contact CenterLine for additional
information or with your requirements so that we can
tailor equipment to your specific application.
|
|
