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UNI-COAT®—Limitations
Fume
Exhaust Systems
Some
engineers specify polyvinyl-chloride-coated ductwork for fume exhaust
applications. McGill AirFlow suggests caution in specifying UNI-COAT ductwork
for any fume exhaust applications. The coated steel is delivered in large
coils, which are made into duct and fittings using conventional sheet
metal fabrication methods. The resulting products are not free of scratches
and other small areas of exposed metal. Because the edges of the coil
and sheet metal are not coated, all leading edges of duct and fittings
expose the base metal to the corrosive environment. McGill AirFlow offers
other materials that are more suitable for fume exhaust systems, for example,
types 304 and 316 stainless steel, type 3003-H14 aluminum, and fiberglass-reinforced
plastic (FRP). Designers must determine the suitability of the UNI-COAT
product and associated sealants based on known chemical exposure of the
application. Installing contractors are responsible for coating any exposed
metal surfaces of the UNI-COAT ductwork after the duct system has been installed.
Exposed
Duct Systems
UNI-COAT ductwork is not suggested for exposed duct systems unless the
owner and engineer are willing to accept the kinds of natural surface
defects described under “Fume Exhaust Systems” above. Instead,
McGill AirFlow recommends SilverGuard™ paintable galvanized steel,
painted after the duct system is installed.
Temperature
The practical temperature range for using UNI-COAT ductwork is -30°F
to +200°F.
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