Equipment Operation, Maintenance, and Troubleshooting
Core Concepts
Operators must understand the operation, maintenance, and troubleshooting of equipment such as pumps, valves, blowers, mixers, clarifiers, filters, chemical feed systems, and disinfection units. Key concepts include preventive maintenance (PM) schedules, vibration analysis, lubrication, seal maintenance, and pump curves. Centrifugal pumps operate on a performance curve; cavitation occurs when NPSH available is less than NPSH required. Positive displacement pumps deliver constant flow regardless of pressure (within limits). Valves (gate, globe, butterfly, check) have specific applications. Blowers supply air for aeration; diffusers can foul. Chemical feed pumps require calibration and maintenance of check valves and diaphragms. Traps include confusing series vs. parallel pump operation (series adds head, parallel adds flow), misdiagnosing cavitation as a mechanical issue, and overlooking check valve failures. Lubrication over-greasing can damage bearings. VFDs (variable frequency drives) require proper tuning and can cause harmonics. Another trap: filter press cycle optimization; membrane fouling signs (increased pressure drop, decreased flux).
Worked Example
A centrifugal pump loses flow and pressure and makes a rattling noise. The most likely cause is cavitation due to a blocked suction strainer. Rule of thumb: cavitation sounds like gravel in the pump; check suction conditions first. This shows the trap of assuming impeller wear without checking NPSH.