Ransburg RMA-560 Single_Dual Purge Direct A13364 - Manual (Page 28)

AIR HEATER REQUIREMENTS
Turbine drive air expands as it moves through the
turbine wheel cavity and as it exits the turbine from
the exhaust port. This expansion will cause cool-
ing of the exhaust air and the surfaces it contacts.
This same expansion cooling can occur across the
shaping air exit ports. This cooling affect can cause
surface temperatures 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
temperature of the supply air may be below the
booth dew point, even without additional expan-
sion cooling.
Condensation is especially probable in waterborne
applications when booth temperature and relative
humidity levels are typically maintained 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 exhaust
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 equipment life. Thus, it is
recommended that air heaters be installed into
the atomizer air supply 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 conditions,
turbine airflow settings, and incoming air tempera-
ture. The heater should be set as low as possi-
ble, sufficient to maintain the applicator surface
temperatures above the dew point in the booth.
Example: With the incoming air temperature at
72°F (22.2°C), and RMA-560 with 65mm bell cup
rotating unloaded at 60 krpm has a turbine outlet
temperature drop of approximately 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, a Ransburg air heater
assembly should be assembled after the air filters
and volume booster. (See heater and filtration
options later in this manual).
SAFE GROUNDING IS A MATTER OF PROPER
EQUIPMENT MAINTENANCE AND INSTAL-
LATION, CORRECT OPERATION AND GOOD
HOUSEKEEPING. Daily inspection of grounding
apparatus and conditions, however, will help pre-
vent hazards that are cause by normal operations.
BE SURE THAT:
1. All objects in the spray area are grounded.
2. Personnel in the spray area are properly
grounded. (Conductive safety shoes and
coveralls.)
3. That the target object is properly grounded
(less than 1 megohm resistance).
4. That the high voltage is off except during
normal application.
5. That the high voltage is off and applicators
are grounded during maintenance opera-
tions.
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.
RMA-560 Single/Dual Purge Direct Charge - Installation
Ransburg
LN-9278-13 25