12.5 Maintenance Management, Work Orders, Asset Management & Plant Air Systems

Why Maintenance Management Is Tested

An operator who can rebuild a pump but cannot say how often it has failed, what it cost, or which asset should be replaced first is not managing a plant. The Class II criteria explicitly list complete equipment maintenance and repair records, including work orders, perform corrective, preventative, and predictive maintenance, and conduct asset management as distinct job tasks. These are exam content in their own right.

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The Four Maintenance Strategies

Corrective maintenance is not automatically a failure of planning. Run-to-failure is a legitimate, deliberate strategy for assets where the consequence of failure is trivial and redundancy exists. It becomes a problem only when it is the default for everything, including critical assets.

Predictive Techniques in a Water Plant

• Vibration analysis on pumps and motors detects imbalance, misalignment, bearing wear, and looseness, each of which has a characteristic frequency signature. Rising bearing-defect frequencies give weeks of warning before failure.
• Infrared thermography on motor control centers, breakers, and connections finds loose or corroded terminations as hot spots long before they arc or fail.
• Oil analysis on gearboxes and large bearings detects wear metals, water ingress, and additive depletion.
• Motor current signature analysis detects rotor bar and winding problems without taking the motor out of service.
• Ultrasonic testing detects compressed air leaks, steam trap failures, and early bearing distress.

The economic case is straightforward: a planned bearing change during a scheduled outage costs a fraction of a catastrophic failure that also destroys the shaft, seal, and coupling and takes the unit down during peak demand.

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Work Orders and Equipment Records

What a Work Order Captures

A usable work order records the asset identifier, the request and its priority, the problem description, who performed the work, labor hours, parts and materials consumed with costs, the failure cause, the corrective action taken, and the completion date and downtime.

The failure cause field is the one most often left blank and the one that carries the most value. Without it, an equipment history is a list of expenses; with it, the history reveals that a pump has been re-packed eleven times in two years because it is misaligned, which is a proactive maintenance finding worth far more than the eleven repairs.

Work Order Types

• Planned / scheduled: generated automatically by the maintenance system on a time or runtime interval.
• Corrective: written against a known defect, scheduled into normal work.
• Emergency: unplanned, immediate, and the type whose frequency measures how well the rest of the program is working.

The Equipment History and the CMMS

A computerized maintenance management system (CMMS) holds the asset register, PM schedules, work order history, parts inventory, and cost accounting. Practical benefits:

• Automatic PM generation so scheduled work is not forgotten.
• Equipment history by asset, which exposes bad actors.
• Parts inventory linkage, with reorder points and usage by asset.
• Cost accumulation, which supports the repair-versus-replace decision.
• Documented compliance for records a sanitary survey will ask to see.

The repair-versus-replace decision is normally made on accumulated life-cycle cost: when cumulative repair cost approaches a defined fraction of replacement cost, or when the failure interval shortens below an acceptable threshold, replacement wins.

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Asset Management

Asset management is the practice of delivering a required level of service at the lowest life-cycle cost, at an acceptable level of risk. EPA frames it around five core questions:

1. What is the current state of my assets? An asset inventory with condition, age, remaining useful life, and value.
2. What is my required level of service? The performance the system has committed to — pressure, quality, reliability, and regulatory compliance.
3. Which assets are critical to sustained performance? Criticality ranking.
4. What are my minimum life-cycle costs? The lowest total cost of ownership across operation, maintenance, renewal, and disposal.
5. What is my best long-term funding strategy? Rates, reserves, and capital planning that actually fund renewal.

Criticality

Criticality = consequence of failure × likelihood of failure.

Consequence includes public health impact, regulatory violation, service interruption, safety hazard, environmental damage, and repair cost. Likelihood reflects age, condition, and failure history.

The result frequently surprises people. A $900 chemical metering pump with no installed spare, feeding the only corrosion-control chemical, can rank far above a $90,000 high-service pump that has two identical redundant units. Criticality drives where PM effort, critical spares, and redundancy investment go — not asset cost.

Remaining Useful Life and Renewal Planning

Each asset has a design life, but condition assessment matters more than age. A pump in clean, cool service may exceed its nominal life; the same pump feeding abrasive lime slurry will not. Renewal planning aggregates remaining useful life across the asset base to forecast capital needs and avoid the common failure mode in small utilities: a large share of the plant reaching end of life simultaneously, with no reserve funded.

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Plant Air Systems

Compressed air is an easily overlooked utility that several critical processes depend on.

Uses in a Water Plant

Compressors and Blowers

Positive displacement compressors — reciprocating and rotary screw — trap and compress a fixed volume and deliver high pressure. Centrifugal compressors accelerate air with an impeller. Blowers deliver high volume at low pressure, which is precisely what filter air scour requires; using a high-pressure compressor for air scour is both wasteful and ineffective.

Air Quality: Moisture Is the Enemy

Compressing air concentrates its moisture. As the compressed air cools downstream, that moisture condenses into liquid water, which causes rust in the piping, valve actuator malfunction, erratic instrument readings, and freezing in outdoor lines.

Controls:

• Aftercoolers and moisture separators downstream of the compressor.
• Automatic condensate traps on receivers and drip legs — and these must be verified, because a failed trap is silent.
• Air dryers for instrument air. The key specification is dewpoint, which must be below the lowest temperature the air line will ever see. Instrument air delivered at a dewpoint above ambient will condense inside the transmitter or positioner and produce exactly the kind of drifting, erratic readings operators waste days chasing.
• Filtration to remove compressor oil carryover, which fouls instruments and degrades elastomers.

Routine Compressor Maintenance

Drain the receiver, check and change lubricating oil, clean or replace intake filters, inspect belts and couplings, verify the pressure relief valve, check unloader operation and cycle frequency, and survey for leaks. Compressed air leaks are a substantial and largely invisible energy cost, and ultrasonic leak detection pays for itself in most plants.

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Facility and Process Control Water Meters

Metering is how a plant knows what it produced, what it used, and what it lost. The criteria call out both maintain facility and process control water meters and interpret facility and process control water meters.

Meter Types

Accuracy and Straight-Run

Most in-line meters require a straight, unobstructed run upstream and downstream — commonly on the order of ten pipe diameters upstream and five downstream, with the exact requirement set by the manufacturer. Installing a meter immediately downstream of an elbow, a partially closed valve, or a pump discharge puts swirl and an asymmetric velocity profile through the element and produces a persistent, invisible error.

Meters are verified against a known standard on a defined schedule and recalibrated when they drift. A propeller meter with worn bearings reads low, which flatters the plant's apparent efficiency while quietly hiding production.

Water Audits and Non-Revenue Water

Comparing master meter production against billed consumption yields non-revenue water. The gap has three components: real losses (leaks and main breaks), apparent losses (meter under-registration, data handling errors, unauthorized consumption), and unbilled authorized consumption (flushing, firefighting, plant process water).

A chronically rising non-revenue percentage is a leak detection trigger. But before concluding the distribution system is leaking, the operator should confirm the master meter itself is accurate — an under-registering customer meter population and an over-registering master meter produce the identical symptom, and the meter is far cheaper to check than the mains.