Maintenance Fundamentals & Work Planning

Maintenance keeps water and wastewater equipment available, reliable, and safe to operate. A good maintenance program does more than repair equipment after it fails. It identifies important assets, plans work, schedules preventive tasks, responds to failures, tracks recurring problems, and verifies that equipment performs correctly after maintenance.

Operators and maintenance personnel should work together. Operators often recognize developing problems first, while maintenance personnel perform inspection, adjustment, repair, and replacement work that requires specialized skills or tools.

What Is Maintenance?

Maintenance includes activities used to preserve or restore equipment condition and function.

Examples include:

• inspection;
• cleaning;
• lubrication;
• adjustment;
• calibration;
• repair;
• component replacement;
• overhaul;
• testing.

Why Maintenance Matters

Poor maintenance can lead to:

• equipment failure;
• process interruption;
• reduced treatment capacity;
• higher energy use;
• poor water quality;
• permit or compliance problems;
• unsafe working conditions;
• higher repair cost.

Maintenance Is Part of Operations

Operations and maintenance are closely connected.

Operators provide information such as:

• abnormal noise;
• changing vibration;
• reduced flow;
• higher temperature;
• frequent alarms;
• increasing leakage;
• longer equipment run time.

These observations can identify maintenance needs before complete failure occurs.

Preventive Maintenance

Preventive maintenance, often called PM, is planned work performed before failure.

Examples include:

• scheduled lubrication;
• bearing inspection;
• belt inspection;
• filter replacement;
• valve exercising;
• generator testing;
• instrument calibration.

Goals of Preventive Maintenance

Preventive maintenance is intended to:

• reduce unexpected failures;
• extend equipment life;
• maintain efficiency;
• identify deterioration early;
• improve reliability;
• reduce emergency repair work.

Corrective Maintenance

Corrective maintenance is work performed to correct a known defect or restore equipment to acceptable condition.

Examples include:

• replacing a leaking seal;
• repairing a failed actuator;
• replacing a worn bearing;
• repairing a damaged pipe;
• correcting instrument drift.

Corrective Does Not Always Mean Emergency

A defect may be discovered before equipment fails completely.

If the equipment can remain safely in service until a planned repair window, the corrective work can be scheduled instead of treated as an emergency.

Emergency Maintenance

Emergency maintenance requires immediate or rapid response because failure threatens:

• public health;
• treatment performance;
• permit compliance;
• worker safety;
• critical service;
• major equipment damage.

Examples of Emergency Maintenance

Possible examples include:

• major water-main break;
• failed critical pump with no available standby;
• wastewater lift-station overflow risk;
• major chlorine leak;
• failed electrical equipment affecting critical treatment;
• large process pipe rupture.

Planned Versus Unplanned Work

Planned maintenance is prepared before work begins.

Planning may include:

• scope of work;
• labor requirements;
• parts;
• tools;
• safety requirements;
• equipment shutdown;
• operational coordination.

Unplanned work begins with little preparation, often after unexpected failure.

Reduce Avoidable Emergency Work

A strong maintenance program attempts to shift work from emergency response toward:

• planned preventive maintenance;
• planned corrective maintenance;
• condition-based maintenance.

Some failures are unavoidable, but repeated emergencies involving the same equipment indicate a maintenance or reliability problem that should be investigated.

Condition-Based Maintenance

Condition-based maintenance uses actual equipment condition to determine when maintenance is needed.

Useful condition indicators include:

• vibration;
• temperature;
• motor current;
• oil condition;
• seal leakage;
• pump efficiency;
• differential pressure.

Predictive Maintenance

Predictive maintenance uses condition data and trends to estimate when deterioration may lead to failure.

Examples include:

• vibration analysis;
• oil analysis;
• infrared inspection;
• motor-condition monitoring;
• performance trending.

Equipment Criticality

Not all equipment is equally important.

Criticality describes the consequence of equipment failure.

Factors may include:

• effect on public health;
• effect on permit compliance;
• loss of treatment capacity;
• availability of standby equipment;
• safety impact;
• repair time;
• replacement cost.

Critical Equipment

Examples of potentially critical equipment include:

• high-service pumps;
• raw-water pumps;
• wastewater lift-station pumps;
• disinfection equipment;
• critical blowers;
• emergency generators;
• major process controls.

Actual criticality depends on facility design and available redundancy.

Redundancy Reduces Consequence

If a facility has several identical pumps and one can fail without reducing required capacity, the immediate consequence may be lower than for a single pump with no standby.

However, losing one redundant unit also reduces the remaining safety margin.

Work Priority

Maintenance work should be prioritized according to risk and operational importance.

Factors may include:

• safety hazard;
• public-health impact;
• compliance risk;
• equipment criticality;
• likelihood of further damage;
• availability of backup equipment;
• effect on production or treatment.

High-Priority Work

High-priority work may include conditions such as:

• immediate safety hazard;
• critical equipment unavailable;
• active major leak;
• process failure developing;
• risk of overflow or service loss.

Low-Priority Work

Lower-priority work may include:

• minor cosmetic repair;
• noncritical equipment issue with full redundancy;
• planned improvements that do not affect current operation.

Low priority does not mean the work should be forgotten.

Work Orders

A work order documents maintenance work that needs to be performed.

A useful work order may include:

• asset identification;
• location;
• problem description;
• priority;
• requested work;
• safety requirements;
• parts needed;
• labor used;
• work performed;
• completion date.

Write Clear Problem Descriptions

A useful work request describes the symptom clearly.

Weak description:

Pump bad.

Better description:

Pump P-204 discharge flow dropped from approximately 750 gpm to 520 gpm while discharge pressure increased from 48 psi to 61 psi.

Specific information helps maintenance personnel prepare for the correct problem.

Asset Identification

Every significant piece of equipment should have a consistent asset identification system.

An asset record may include:

• equipment number;
• manufacturer;
• model;
• serial number;
• location;
• capacity;
• motor data;
• maintenance history.

Maintenance History

Maintenance history helps identify:

• recurring failures;
• high-maintenance equipment;
• frequent parts replacement;
• increasing repair cost;
• equipment approaching end of useful life.

Planning a Maintenance Job

Before planned work begins, consider:

• what work is required;
• which equipment must be shut down;
• what process capacity will remain;
• what tools are needed;
• what replacement parts are needed;
• what safety controls are required;
• how long the equipment may be unavailable.

Define the Work Scope

The work scope should explain exactly what needs to be accomplished.

A clear scope reduces:

• misunderstanding;
• unnecessary work;
• missing parts;
• repeat shutdowns.

Parts Planning

Before equipment is taken out of service, verify availability of required parts such as:

• bearings;
• seals;
• gaskets;
• belts;
• lubricants;
• fasteners;
• instrument components.

Tool Planning

Maintenance planning should consider special tools such as:

• lifting equipment;
• alignment tools;
• torque tools;
• electrical test equipment;
• calibration equipment;
• special manufacturer tools.

Labor Planning

Some work requires specialized personnel.

Examples include:

• electrician;
• instrument technician;
• mechanic;
• welder;
• contractor;
• manufacturer technician.

Coordinate Maintenance with Operations

Before shutting down equipment, operations and maintenance should agree on:

• shutdown time;
• required standby equipment;
• process limitations;
• expected work duration;
• return-to-service procedure.

Maintenance Windows

A maintenance window is a planned period when equipment can be removed from service with acceptable operational impact.

Good maintenance timing may consider:

• low-demand periods;
• tank levels;
• weather;
• process loading;
• availability of backup equipment.

Do Not Remove Too Much Capacity

Before maintenance begins, verify that remaining equipment can handle expected demand.

Taking multiple units out of service at the same time can eliminate required redundancy or capacity.

Safety Planning

Maintenance planning should identify hazards before work begins.

Possible hazards include:

• electrical energy;
• hydraulic pressure;
• rotating equipment;
• chemicals;
• confined spaces;
• fall hazards;
• lifting operations.

Lockout/Tagout

When maintenance exposes workers to hazardous energy, required lockout/tagout procedures must be followed.

Energy sources may include:

• electrical;
• mechanical;
• hydraulic;
• pneumatic;
• gravity;
• stored pressure.

Operational Isolation

Equipment may also need process isolation.

This can include:

• closing valves;
• draining piping;
• relieving pressure;
• blocking flow;
• removing chemical supply.

Isolation must be verified before work begins.

Scheduled Maintenance

Scheduled maintenance is assigned to a specific time based on:

• priority;
• labor availability;
• parts availability;
• equipment availability;
• process conditions.

Maintenance Backlog

The maintenance backlog is work that has been identified but not yet completed.

A backlog is normal, but it must be controlled.

Backlog should be reviewed for:

• priority;
• age;
• risk;
• parts status;
• repeated deferral.

Old Work Orders

An old open work order may indicate:

• low priority;
• missing parts;
• lack of labor;
• poor planning;
• work that is no longer needed.

Open work orders should be reviewed rather than left indefinitely without explanation.

Deferred Maintenance

Deferred maintenance is work intentionally postponed.

Deferral may be reasonable when:

• risk is low;
• equipment remains safe;
• standby capacity is available;
• repair is scheduled for a better operating window.

Document Why Work Is Deferred

If important maintenance is postponed, document:

• reason;
• risk;
• temporary controls;
• planned completion date.

Temporary Repairs

A temporary repair may restore limited service until permanent work can be completed.

Temporary repairs should be:

• safe;
• authorized;
• documented;
• inspected;
• tracked until permanent repair.

Do Not Let Temporary Become Permanent by Accident

Temporary repairs can remain in service longer than intended if they are not tracked.

The maintenance system should keep the permanent repair visible until completed.

Break-In Work

Unexpected high-priority work that interrupts the planned schedule is sometimes called break-in work.

Too much break-in work can indicate:

• poor preventive maintenance;
• aging equipment;
• inadequate planning;
• insufficient spare parts;
• poor condition monitoring.

Maintenance Schedule Compliance

Scheduled PM tasks should be completed within appropriate intervals.

Repeatedly missed preventive maintenance can increase future corrective and emergency work.

Post-Maintenance Testing

Work is not complete simply because parts were replaced.

Equipment should be tested before normal service is restored.

Checks may include:

• correct rotation;
• normal flow;
• normal pressure;
• acceptable vibration;
• normal temperature;
• normal motor current;
• no abnormal leakage;
• correct controls and alarms.

Return to Service

Before returning equipment to normal operation, verify:

• maintenance work is complete;
• tools and temporary materials are removed;
• guards are installed;
• valves are correctly positioned;
• locks and tags are removed according to procedure;
• control mode is correct;
• alarms are normal.

Close the Work Order

A completed work order should record what actually happened.

Useful information includes:

• problem found;
• repair performed;
• parts used;
• labor;
• test results;
• follow-up needed.

Failure Coding

Some maintenance systems classify failures by cause or type.

Examples include:

• bearing failure;
• seal failure;
• electrical failure;
• corrosion;
• blockage;
• operator damage.

Consistent failure coding can help identify recurring problems.

Root-Cause Analysis

Repeated or significant failures should be investigated beyond the immediate failed part.

Example:

• failure: pump bearing failed;
• immediate repair: replace bearing;
• possible root cause: chronic misalignment.

If the root cause is not corrected, the replacement bearing may fail again.

Ask Why the Failure Occurred

Useful root-cause questions include:

• Was lubrication correct?
• Was equipment aligned?
• Was the equipment overloaded?
• Was operation outside the design range?
• Was preventive maintenance missed?
• Was the replacement part correct?

Spare Parts

Critical spare parts reduce downtime when equipment fails.

Possible critical spares include:

• bearings;
• mechanical seals;
• motors;
• VFDs;
• instrument transmitters;
• valve actuators;
• special gaskets.

Do Not Stock Every Part

Spare-parts decisions should consider:

• equipment criticality;
• failure frequency;
• supplier lead time;
• cost;
• storage life;
• availability of substitutes.

Contract Maintenance

Some maintenance may be performed by contractors when:

• special expertise is required;
• special equipment is needed;
• staff resources are limited;
• manufacturer service is required.

Plan Contractor Work Carefully

Contract work may require coordination of:

• site access;
• safety orientation;
• lockout/tagout responsibilities;
• equipment shutdown;
• permits;
• post-work testing.

Computerized Maintenance Management System

A Computerized Maintenance Management System, or CMMS, can be used to manage:

• assets;
• work orders;
• PM schedules;
• spare parts;
• maintenance history;
• backlog;
• labor records.

CMMS Data Quality

A maintenance system is useful only if information is entered accurately.

Poor descriptions and incomplete work-order closure reduce the value of maintenance history.

Maintenance Performance Indicators

Facilities may track measures such as:

• PM completion;
• emergency work;
• backlog;
• equipment downtime;
• repeat failures;
• maintenance cost.

Too Much Emergency Work

A high proportion of emergency maintenance may indicate:

• weak preventive maintenance;
• aging assets;
• poor planning;
• insufficient staffing;
• lack of condition monitoring.

Priorities Can Change

Maintenance priorities should be reviewed when:

• equipment condition worsens;
• standby equipment becomes unavailable;
• process demand changes;
• a safety hazard develops;
• compliance risk increases.

Communication Between Shifts

Maintenance-related information should be included in shift handoff.

Examples include:

• equipment out of service;
• temporary repairs;
• manual control;
• bypassed equipment;
• maintenance scheduled for the next shift;
• restricted operating capacity.

Common Maintenance Planning Mistakes

• Waiting for critical equipment to fail before planning maintenance.
• Assigning priorities without considering equipment criticality.
• Writing vague work orders.
• Taking equipment out of service before verifying parts and tools.
• Removing too much process capacity at one time.
• Ignoring safety and isolation requirements during planning.
• Allowing temporary repairs to remain untracked.
• Allowing old work orders to remain open indefinitely.
• Closing work orders without recording what was found and repaired.
• Replacing failed parts repeatedly without root-cause investigation.
• Failing to test equipment after maintenance.
• Failing to return controls and valves to normal after work.

A Practical Maintenance Planning Sequence

1. Identify the maintenance need.
2. Describe the symptom or required work clearly.
3. Identify the correct asset.
4. Assign priority based on safety, compliance, and operational risk.
5. Define the work scope.
6. Identify required labor, tools, and parts.
7. Identify safety and isolation requirements.
8. Coordinate equipment shutdown with operations.
9. Select an appropriate maintenance window.
10. Perform the work.
11. Test equipment before return to service.
12. Restore normal valve and control configuration.
13. Document findings, parts, and work performed.
14. Close the work order.
15. Investigate root cause when failure is significant or recurring.

What to Remember for the Exam

• Maintenance includes inspection, adjustment, lubrication, repair, replacement, testing, and other work used to preserve equipment function.
• Preventive maintenance is planned work performed before failure.
• Corrective maintenance restores defective equipment to acceptable condition.
• Corrective maintenance does not always have to be emergency work.
• Emergency maintenance addresses conditions requiring immediate or rapid response.
• Condition-based maintenance uses actual equipment condition to determine maintenance need.
• Equipment criticality is based on the consequence of failure.
• Maintenance priority should consider safety, compliance, process impact, and available redundancy.
• A work order should clearly identify the asset, problem, priority, and work performed.
• Good maintenance planning includes labor, parts, tools, safety, shutdown, and operational coordination.
• Do not remove equipment from service before confirming that adequate process capacity remains.
• The maintenance backlog should be reviewed for priority, age, and risk.
• Deferred and temporary repairs should be documented and tracked.
• Post-maintenance testing is required to verify that equipment performs correctly.
• A work order should not be considered complete until findings and corrective actions are documented.
• Repeated failures should trigger root-cause investigation.
• Critical spare-parts decisions should consider failure consequence and supplier lead time.
• A CMMS can manage assets, PM schedules, work orders, spare parts, history, and backlog.
• Required lockout/tagout and process isolation must be planned before maintenance involving hazardous energy.
• Operations and maintenance should communicate equipment status, temporary conditions, and reduced capacity between shifts.