Ransburg MMA-303 Direct_Ind Charge Atomizer A12870 - Manual (Page 46)

MMA-303 Direct/Indirect Charge - Installation
43 LN-9269-11.3
EQUIPMENT GROUNDING AND
SAFETY RECOMMENDATIONs
(Continues)
6. The spray area is kept free of accumulated
coating deposits.
7. All combustible liquids in the spray area
(outside of automatic delivery systems) are
kept to minimum and are kept in fire safe,
grounded containers. (See NFPA-30 and
chapter 6 of NFPA-33.)
8. Proper ventilation is provided.
9. Personnel must thoroughly understand the
equipment, its operation and maintenance,
and all safety precautions.
AIR HEATER REQUIREMENTS
Turbine drive air expands as it moves through
the turbine wheel cavity and as it exits the tur-
bine from the exhaust port. This expansion will
cause cooling of the exhaust air and the sur-
faces it contacts. This same expansion cool-
ing car occur across the shaping air exit ports.
This cooling affect can cause surface tempera-
tures to fall below the dew point of the booth,
which will result in condensation on the interior
and exterior of the atomizer, machine, and its
components. It is even possible that the tem-
perature of the supply air may be below the
booth dew point, even without additional ex-
pansion cooling.
Condensation is especially probable in water-
borne applications when booth temperature
and relative humidity levels are typically main-
tained very high. This condensation will allow
sufficient conductivity of the surfaces such that
they act as an erratic ground source potential.
This can cause damage to the equipment.
It is therefore, a requirement that turbine ex-
haust air temperature be maintained above
the booth dew point to prevent condensation
from forming on atomizer surfaces. Doing so
will eliminate moisture as a potential defect in
painted surfaces as well as extending equip-
ment life. Thus, it is recommended that air
heaters be installed into the atomizer air sup-
ply lines, i.e. turbine drive air, shaping air, and
seal air. The air heaters must be of sufficient
capacity, capable of raising the incoming air
temperature at least 40°F (4.4°C) at a flow
rate of 60 SCFM per applicator.
The actual air heater process setting depends
on applicator fluid flow rate load, booth condi-
tions, turbine airflow settings, and incoming air
temperature. The heater should be set as low
as possible, sufficient to maintain the applica-
tor surface temperatures above the dew point
in the booth.
Example: With the incoming air temperature
at 72°F (22.2°C), and MMA-303 with 65mm
bell cup rotating unloaded at 60 krpm has a
turbine outlet temperature drop of approxi-
mately 28°F (-2.2°C) @ 40 krpm unloaded,
∆
~14°F (-10°C). Referring to the ASHRAE
Psychrometric chart, the saturation
temperature range (dew point) of a spray
booth maintained at 70-75°F/65-70% RH is 62
-68°F (21.1-23.9°C/65-70°RH is 16.7-20°C).
Thus it is almost certain that the surface
temperatures of the applicator will fall below
the dew point of the booth, and an air heater
will be needed in this case.
To prevent condensation, an Ransburg Air
Heater Assembly (A11065-05) should be
assembled after the air filters. (Reference the
current “Air Heater Assembly “ service manual
for further information.)