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CIP System Troubleshooting Guide 309
meet the same needs and much more. Operation problems may involve high-level
and low-level control points and alarm messages.
High Level
When the water supply tank at high level alarm is noted, it is not a“circuit” failure
but an indication of an equipment maintenance or calibration issue, which may
include
& aslow acting water supply shut-off valve;
& acalibration issue with the water supply tank level sensor (if analog, rather than
aprobe).
The analog level sensor provides arange of set points and is usually not
responsible for reporting ahigh-level alarm; the duty of the high high-level sensor,
usually adiscrete level element from which the active input spurs the alarm. The
shut-off valve is controlled by the level element, and aslow to close valve can
result in ahigh high-level alarm, and the valve troubleshooting should be as
previously described.
Afield investigation at the water supply tank will aid in determining if there
is alevel element calibration issue, or if the valve simply failed to promptly close.
The water supply valve is typically interlocked to close when the high-level probe
input is noted, but if thereisamechanical failure of the valve, an overflow condition
of short duration can result. This overflow condition is also an obvious indication of
alevel instrument calibration error if the valve promptly closed when commanded.
If the tank is not overflowing, avisual check will enable the investigator to determine
if perhaps the level sensor calibration is in error, and ahigh-level condition
does not in fact exist. If the sensors are inorder, the next consideration is the water
supply valve.
If the field examination reveals the water supply valve actuator slow to
respond, the problem may be with any number of valve components. As previously
described, the troubleshooter should start at the valve, and work back to the
solenoid and I/O to resolve the problem.
Low Level
When the water supply tank—low level alarm is provided,itmay be considered aCIP
circuit failure ifthe CIP supply operations must be suspended until asufficient
water volume can be accumulated. Alow-level alarm is an indication of either an
equipment or water supply issue, the most common being
& aslow to open water supply shut-off valve;
& awater supply tank level sensor calibration issue;
& insufficient water supply.
The suggested order of action includes the following field investigations
& the water supply valve should be fully open when alow-level condition is
noted;
& investigate the actual water tank level to determine if there isalevel element
calibration issue;
& the water supply valve should be commanded open and closed. If the
examination finds the water supply valve actuator is slow to open the valve,