Troubleshooting Loss Of Color - MAGUIRE MPA-6 Series Installation Operation & Maintenance

M P A 
S e r i e s

TROUBLESHOOTING LOSS OF COLOR

1. Check that color supply is adequate by tipping drum of color slightly or observing level of
color. Consider that if color level is nearing the bottom of the drum, air may have been
sucked in momentarily and a considerable length of time would have passed before the
loss of color would be evident at the process machine.
2. Check that the motor is rotating the proper number of revolutions per cycle. 10 counts
equals about 1 turn of the motor. Remember that the Range Switch can alter this
relationship so that 10 counts will equal 1/10 revolution or 10 revolutions.
An incorrect relationship between counts and revolutions may indicate an internal electronic
problem. See Controller problems.
In 6-Roller Pumps, contamination of the roller set from liquid color will most probably result
in slipping of the drive roller and a corresponding lack of color output. If you suspect
slippage is the problem, disassemble and clean the pump head and rollers with soap and
water. DO NOT LUBRICATE ANY PUMP HEAD PARTS. Reassemble and recheck for
proper pump rotation.
3. Check that pump tube is not permanently flattened. Replace if necessary. Very short tube
life may indicate a chemical compatibility problem.
4. Check for vacuum leaks on the inlet side of the pump head. Be sure that TEFLON TAPE
was used on all pipe thread connections on the suction side of the pickup assembly. A
vacuum leak is indicated if the pump pumps air out of the outlet without sucking liquid into
the inlet. Place a moist finger over the outlet end of the pump tube to feel for escaping air.
Bubbles in the liquid color output may also indicate an air leak. If an air leak is indicated, re-
tape and re-tighten all threaded connections. Check for obstructions at the inlet end of the
pump tube. Disconnect brass fittings and check for blockage at this point. Alternating
suction and pressure, or pulsating, at the output end indicates a blocked tube. Check for
blockage and reprime pump if necessary.
5. Pump speed may exceed the flow characteristics of the liquid being pumped. Pump suction
alone is used to draw liquid into the pumping unit and only normal atmospheric pressure of
15 PSI is available to push liquid into the inlet end of the pump tubing assembly. Higher
viscosity liquids do not flow as fast as lower viscosity liquids and may not be capable of
flowing through pump tubing as rapidly as pumping speed would dictate. To determine if
the maximum possible flow rate is being exceeded, reduce counter setting by 50%. If
output does not drop proportionally, viscosity is a problem. To solve this, you may:
1. Locate color closer to the pump head using larger diameter supply lines to reduce
flow restrictions where possible.
2. Use a larger diameter pump tube.
3. Specify a larger capacity pump.
4. Reformulate liquid color for lower viscosity.
M A G U I R E P R O D U C T S , I N C .
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