BNP PRESSURE BLAST CONVERSION KIT Page 11
it may be necessary to change media more often, or
install an aftercooler or air dryer.
8.5.4 Absorption. Some media tends to absorb
moisture from the air, especially fine-mesh media in high
humidity areas. Empty the media and store it in an
airtight container when cabinet is not in use.
8.5.5 A vibrator mounted either on the blast machine
leg or on a bolt on the media metering valve may help
prevent bridging of fine-mesh media
8.6 Neither Media Nor Air Comes Out The Nozzle
When The Foot Pedal Is Pressed
8.6.1 Depressurize the blast machine, and check the
nozzle to see if it is plugged. See Section 8.4.
8.6.2 Check that the blast machine pressurizes when
the foot pedal is pressed. If it does not, see Section 8.11.
8.6.3 Check that the media metering valve and the
choke valve are open.
8.7 Blast machine Will Not Depressurize Or
Depressurizes Too Slowly
8.7.1 Check for blockage in the 4-way valve mufflers.
8.7.2 Check that the 3-way valve in the foot pedal
exhausts air when pedal is released. If it does not, check
the line for blockage, and check the switch for defect.
8.7.3 Check the outlet muffler for blockage.
8.7.4 Check 4-way air valve for jamming. See Section
8.10.4 and 8.10.5.
8.8 Heavy Media Flow
8.8.1 Make sure the choke valve is open.
8.8.2 Media metering valve open too far. Adjust per
Section 5.2. If adjusting the media valve does not
regulate media flow, empty the machine, depressurize
the machine, and inspect the internal parts of the valve
for wear.
8.9 Media Surge: A small amount of surge is
normal at start-up.
8.9.1 Heavy media flow. Adjust per Section 5.2
8.9.2 Empty, and depressurize the blast machine, and
inspect the internal parts of the metering valve for wear.
8.10 Air Only (no media) Comes Out The Nozzle
8.10.1 Make sure the machine contains media.
8.10.2 Check that the media metering valve is not
closed.
8.10.3 Check for minor blockage in the media metering
valve by fully opening the metering valve, and closing
the choke valve. Activate the foot pedal to blow out
obstructions. If this procedure fails, depressurize the
machine, open the metering valve clean out cap and
check for foreign objects.
8.10.4 Check the muffler on the 4-way air valve. Air
should exhaust from the muffler when the foot pedal is
pressed. If air does not exhaust, remove the muffler and
try again. If air exhausts now, the muffler is blocked. If
air still does not exhaust, the 4-way valve may be faulty.
8.10.5 Check the 4-way valve as follows: Depressurize
the air supply line. Remove the tubing leading to either
the media metering valve or diaphragm outlet valve.
Pressurize the air supply line. No air should exhaust
from the tube adaptor. Press the foot pedal, air should
start exhausting at the adaptor, and stop when pressure
on the pedal is released. If it does not operate
accordingly, the 4-way valve is probably faulty.
8.11 Blast Machine Will Not Pressurize
8.11.1 Make sure that the air compressor is on and air
supply valves are open.
8.11.2 Check that pressure regulator is not turned
down. Minimum pressure is 40 psi. See Section 5.1.
8.11.3 Inadequate air supply. Check table in Figure 3.
8.11.4 Inspect the diaphragm in the outlet valve for
wear.
8.11.5 Inspect pop-up valve and seat for wear and
alignment.
8.11.6 Blocked or leaking control line. Check all fittings
and urethane tubing for blockage or leaks.
8.11.7 Foot pedal valve malfunction. Check foot pedal
for alignment, and inlet and outlet lines for pressure.
8.11.8 Make sure the lines are not reversed on the foot
pedal or pilot regulator. See schematic in Figure 4.
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