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The
spray gun and support equipment represent a substantial dollar
investment. The best method of protecting that investment
is a planned maintenance program which should include a supply
of spare parts and daily maintenance checks.
RECOMMENDED
SPARE PARTS FOR EACH GUN
- Air
nozzle, needle and tips
- Packing
and gaskets
- Hoses
and fittings
- Gauges
- Proper
lubricants
- Filter
screens
- Diaphragms
for pressure regulators
RECOMMENDED
EQUIPMENT MAINTENANCE
Daily
clean-up all parts with proper cleaners/solvents. Re-lubricate
where lubricant is washed away by cleaning. Moisture traps
and compressor tanks must be drained daily.
CALIBRATION
Catalyst
injection spray equipment must be calibrated as polyester
resins require the addition of exact amounts of catalyst
for working and production requirements in order to attain
their proper physical and chemical properties. One of the
most important keys to successful Gel coat application is
making sure that spray equipment is operating at the proper
catalyst to Gel coat ratio. In order to stay within the
proper working range, calibration of the spray equipment
is necessary. Calibration of any dual feed spray gun follows
the same basic procedures. Set the Gel coat for proper flow
rate and atomization, then adjust the catalyst for the proper
delivery rate (ratio of catalyst to Gel coat).
CALIBRATION
PROCEDURES FOR AIRLESS AUTOMATION
1.
Before starting the calibration procedure, make sure that
adequate safety precautions are observed.
2.
Make sure all air to gun and catalyst pots are turned off,
hose connections are tight and that the gun is grounded.
The gun should not be pointed at yourself or anyone else
at anytime.
3.
Be sure that all mechanical parts of the gun are in good
working condition; clean and lubricate where necessary.
Filters, screens and tips should be clean and air regulators
backed out to zero pressure.
4.
Once the proper tip is installed, the air should be turned
on and the air motor regulator adjusted until good break-up
is observed and no tails are present in the fan.
5.
A 12-inch piece of rubber hose should be placed over the
gel coat tip and sprayed into a previously weighed container
for 15 seconds. The material should be weighed (don't forget
to subtract the weight of the container) and multiplied
by 4. If weight is in grams, divide by 454. This gives you
pounds per minute.
6.
Air supply to gel coat spray air motor should be turned
off and the gun triggered to relieve remaining pressure.
7.
It is important to make sure the catalyst pot is full
and in good working order. The flow rate of the catalyst
should be set according to manufacturer's instructions.
The ideal catalyst setting is in the range of 1.5 - 2.0%
MEKP.
8. Flow Rate in grams per minute X (Desired Percent
Catalyst) = Grams per minute of 100catalyst needed. When
working with diluted catalyst, a dilution factor must be
included in the calculation.
- 100
grams at 1:1 dilution contains 50 grams of catalyst
- 100
grams at 2:1 dilution contains 33.3 grams of catalyst
- 100
grams at 3:1 dilution contains 25.0 grams of catalyst
- For
100 grams of catalyst using a 1:1 dilution, 200 grams
of solution are needed.
- For
100 grams of catalyst using a 2:1 dilution, 300 grams
of solution are needed.
- For
100 grams of catalyst using a 3:1 dilution, 400 grams
of solution are needed.
9.
Once flow rate is set, a clean 12' hose should be connected
to the catalyst tip and sprayed for 30 seconds into a pre-weighed
container. Catalyst weight X 2 is flow rate (grams) per
minute of catalyst.
10.
Once catalyst and gel coat rates are set, the ball setting
on the catalyst should be noted and the number of pump strokes
per minute counted. These parameters are useful for noting
any deviations in calibration but are not a substitute for
the calibration procedure.
CALIBRATING
AIR-ATOMIZED EQUIPMENT
For
calibration of an air-atomized system, the same principles
apply as for airless spray calibration. The gun is set for
the desired delivery rate and proper atomization, then the
catalyst delivery system is set so that the proper amount
of catalyst is delivered.
1.
Make sure air supply to the equipment is clean and free
of oil, water or rust. The gun and catalyst delivery system
should be clean and in good working order.
2.
With catalyst delivery and atomization air off, the pump
or pot pressure should be adjusted to deliver desired flow
rate of material. Collect in a weighed container for 15
seconds and calculate delivery rate. See Procedure 5
above.
3.
The desired catalyst flow rate should be calculated and
the delivery rate set. The delivery rate should be verified
by collecting and weighing the catalyst as described in
Procedures 8 and 9 above. Actual collecting and weighing
of catalyst is not practical for some pieces of equipment.
Catalyst should be set according to recommended ball settings
and verified by spraying material on a piece of cardboard,
collecting some in a cup and measuring gel time.
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