Problem in Water Level Control System

This water level control system (for a municipal water supply operation) is supposed to maintain constant water level in the filter and in the clearwell. Unfortunately, it has a problem. Operators call you urgently to determine why the clearwell is completely empty:

Water Level Control System

Your first step is to ask the operator if they have actually inspected the clearwell to verify that it is empty. They have, and it is. They also point to the display for level controller LIC-30 and show you that it reads 0% level.

Identify the likelihood of each specified fault for this water filtration system. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for all measurements and symptoms in this system.

Also identify the below mentioned faults are possible or impossible?

• Transmitter FT-21 failed with low output
• Transmitter FT-21 failed with high output
• Transmitter LT-25 failed with low output
• Transmitter LT-25 failed with high output
• Transmitter FT-28 failed with low output
• Transmitter FT-28 failed with high output
• Transmitter LT-30 failed with low output
• Transmitter LT-30 failed with high output
• Effluent pump turned off

Finally, identify the next diagnostic test or measurement you would make on this system. Explain how the result(s) of this next test or measurement help further identify the location and/or nature of the fault.

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Read Next:

• Instrument Maintenance
• Water Level Control Logic
• Turbine Control System
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• Terms in Water Supply System

Credits: Tony R. Kuphaldt