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SPRAY PAINTING EQUIPMENT The following suggestions are intended only as
a guide to the selection of spray painting equipment and are
based on limited Plastiglas de Mexico laboratory experience.
Consult the manufacturer of the equipment for recommendations for
specific applications. SPRAY GUN The DeVilbiss Type MBC gun or equivalent can be
used with suitable nozzles and air caps. An air cap with the
maximum number of jets generally gives the best atomization.
Consult the spray gun manufacturer or the paint supplier for the
specific nozzle and air cap required. If a siphon feed is used, it should be adjusted
to give a wide pattern with a low feed rate. The siphon feed
system should be equipped with a No. 30 air cap and an FF nozzle
on the MBC spray gun. A pressure feed system is best for spray
painting. This will produce good atomization with half the volume
of air required for a siphon feed system. Using less air means
there will be less over-spray, and a larger pattern of spray will
be developed, giving more uniform coverage. The MBC gun can be
used with the DeVilbiss No. 765 air cap and an FX nozzle set to
deliver a fluid flow of 3 to 4 oz./mint. Pressure tanks should be
equipped with air operated stirrers for continuous operation
during spraying. When the paint is mixed to the correct
viscosity, the spray gun atomizing pressure should be in the
range of 50 to 60 psi. Regardless of the feed system used, the paint
should be applied in light coats. When seen by reflected light,
the paint should appear wet. For uniform light transmission, at
least 8 mist coats should be applied. The Chemcast® GP should be
back lighted while spraying to judge the tube hiding ability of
the paint coat. Only explosion proof lighting fixtures should be
used in the spray booth. The spray gun should be cleaned after
each day's use. COMPRESSOR AND HOSE The air compressor should have sufficient
capacity to maintain the required air pressure for the type and
number of guns used. A DeVilbiss Type UBP air compressor will
maintain maximum pressure for two Type MBC spray guns with No. 30
air caps. The same spray guns with No. 765 air caps would require
a DeVilbiss Type VBT compressor. The air hose should be about 25
feet long and at least 5/~6/' inside diameter to limit the amount
of pressure drop. STIRRERS If pressurefeed tanks are used, they must be
equipped with continuously operating airdriven stirrers.
Constant stirring is necessary to prevent pigment settling. Hand
stirrers are unsatisfactory because they offer only intermittent
operation. STRAINERS AND WATER TRAPS Metal screen strainers should be used both at
the pressure tank and at the spray gun. The DeVilbiss strainer
Type VS510 is suitable for attachment to the spray gun fluid
inlet. Spray paint pots, filters, and strainers in the paint
lines leading to the guns should be thoroughly cleaned at least
once a week. The metal screens in the strainer should be cleaned
at least once a day. The air delivered to the spray gun must be free
of moisture. Moisture can be removed from the air by a
combination of condensers and transformers in the air line.
Transformers of the DeVilbiss Types HL, HLC, or HLD are
satisfactory. Auxiliary condensers should be installed in the
line, and should be drained frequently to prevent accumulation of
water. The frequency of draining will vary with atmospheric
conditions. The air transformers should be equipped with
automatic water drains to prevent contamination of the air
supplied to the gun. DeVilbiss automatic drain Type DOD is
available with adapters for attaching to Type HL or HLC
transformers. SPRAY BOOTH Spray booths should be large enough to
accommodate the largest size Chemcast® GP panels to be painted.
A floor type hood about 8 feet high by 12 feet wide is usually
large enough. The ventilating system on the hood should be
designed to remove vapors from the floor area as well as from the
higher areas. The booth should also include an explosionproof
light box for back lighting. |
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Copyright © Plastiglas de Mexico 1999
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