Preventive Maintenance, Troubleshooting, and Diagnostics

Introduction to the Industrial Mechanic's Role in Maintenance

The industrial mechanic (millwright) is not just a machine installer; you are the guardian of equipment reliability. In Canada, the Red Seal exam evaluates your ability to plan, execute, and document preventive maintenance (PM) activities, as well as to diagnose complex breakdowns under pressure. This chapter covers the fundamental principles, measurement techniques, tolerance calculations, and regulatory requirements you must master.

The distinction between preventive maintenance (planned, before failure) and corrective maintenance (after failure) is crucial. The Red Seal tests your judgment in choosing the right strategy based on equipment criticality and downtime costs.

Types of Maintenance and Strategies

Systematic Preventive Maintenance

This is performed at fixed intervals (calendar-based or operating hours). Examples: oil changes every 2,000 hours, belt replacement every 6 months, lubrication every 500 hours. The advantage is predictability; the disadvantage is waste if components are not worn.

Condition-Based Maintenance (Predictive)

This relies on machine condition monitoring. You only intervene when thresholds are exceeded. Techniques include:

Vibration Analysis: measurement of overall vibration (mm/s RMS) and frequency spectra.

Infrared Thermography: detection of hot spots on bearings, motors, and electrical connections.

Oil Analysis: spectrometry to detect metallic particles (abnormal wear), viscosity, and acidity (TAN).

Ultrasonics: detection of compressed air leaks or low-speed bearing defects.

Reliability-Centered Maintenance (RCM)

This is a systematic approach that analyzes failure modes (FMEA) to determine the best strategy. The exam may ask you to justify why a critical pump uses condition-based maintenance rather than systematic maintenance.

Comparative Table of Strategies

Strategy	Implementation Cost	Fault Detection	Failure Risk	Labor Required
Corrective	Low	None	High	Low (but urgent)
Systematic Preventive	Medium	Partial	Medium	High (planned)
Condition-Based	High	Early	Low	Medium (analysis)
Advanced Predictive	Very High	Very Early	Very Low	Specialized

Planning and Executing Preventive Maintenance

Lockout/Tagout Procedures

Before any intervention, lockout/tagout is mandatory under federal and provincial legislation (Canada Labour Code, Part II). The steps are:

23.Identify all energy sources (electrical, pneumatic, hydraulic, gravity, spring, steam).

24.Notify affected operators.

25.Shut down the equipment safely.

26.Isolate energy sources (open disconnects, close valves).

27.Apply locks and tags (one lock per worker).

28.Dissipate residual energy (discharge capacitors, bleed hydraulic accumulators, verify absence of pressure).

29.Verify isolation by attempting a start-up (zero-energy test).

Exam Trap: A hydraulic accumulator can store dangerous energy even after the pump is stopped. You must always bleed it or mechanically block it.

Work Orders and Documentation

A good work order (WO) contains: problem description, required tools, spare parts, work permits (hot work, confined space), and safety instructions. Traceability is essential: record measurements (clearances, temperatures, vibrations) to compare trends.

Lubrication: Principles and Pitfalls

Quantity: Over-greasing is as damaging as under-greasing. The general rule is to fill the bearing to approximately 30-50% of its cavity for high speeds, and up to 70% for low speeds.

Grease Type: Never mix incompatible greases (lithium soap vs. calcium soap). Use manufacturer specifications (base oil viscosity, NLGI 0 to 3).

Interval: Approximate calculation based on speed (N) and bore diameter (d): Interval (hours) = K × (140,000 / (N × d))^0.5 for ball bearings. K is a service factor (0.5 to 2).

Alignment and Tolerances

Coupling alignment is a key task. Typical tolerances for parallel and angular alignment are:

Normal speed (1,800 rpm): 0.05 mm (2 mils) parallel, 0.05 mm/mm angular.

High speed (3,600 rpm): 0.03 mm (1 mil) parallel, 0.03 mm/mm angular.

Low speed (< 600 rpm): 0.10 mm (4 mils) parallel.

Use dial indicators or a laser system. Thermal expansion is a critical factor: a hot machine expands, so cold alignment must compensate for expected thermal growth (e.g., 0.10 mm intentional offset for a pump at 80 °C).

Diagnostic Techniques and Troubleshooting

Systematic Troubleshooting Methodology

46.Observe: Listen, look, feel (vibrations, odors, abnormal noises).

47.Identify symptoms: Do not confuse cause and effect. Example: a hot bearing can be caused by misalignment, over-greasing, or excessive load.

48.Isolate: Divide the system into subsystems (motor, coupling, gearbox, load).

49.Measure: Use instruments (vibrometer, infrared thermometer, tachometer, ammeter).

50.Analyze: Compare to reference values.

51.Correct: Perform the repair.

52.Verify: Restart and confirm the symptom has disappeared.

Vibration Analysis: Essential Concepts

Vibrations are expressed in velocity (mm/s RMS) for the 10 Hz to 1 kHz range, and in acceleration (g) for high frequencies (bearing defects). ISO 10816-3 standards provide thresholds:

Zone	Machine Condition	Velocity (mm/s RMS)
A	New machine	< 1.8
B	Acceptable	1.8 to 4.5
C	Tolerable (alarm)	4.5 to 11.2
D	Dangerous (shutdown)	> 11.2

Characteristic Frequencies:

Unbalance: 1× rotational speed (1X).

Misalignment: 2× speed (2X), often with harmonics.

Mechanical Looseness: multiple harmonics (1X, 2X, 3X...).

Bearing Defect: high frequencies (BPFO, BPFI, BSF, FTF) non-synchronous with speed.

Thermography and Limitations

Thermography detects abnormal heat buildup. A bearing running 10 °C above ambient temperature is suspect. Watch out for false readings: reflective surfaces (polished steel) and variable emissivity. Set emissivity (ε) from 0.95 for matte paint to 0.10 for polished aluminum.

Oil Analysis: Quick Interpretation

Viscosity: A decrease indicates dilution (fuel, water) or degradation.

Acid Number (TAN): A rapid increase indicates oxidation.

Metallic Particles: Iron (bearings, gears), Copper (bushings), Lead (bearings). Particle size and quantity (PPM) determine severity.

Water: Above 0.1% (1,000 PPM), the oil must be changed.

Troubleshooting Hydraulic and Pneumatic Systems

Hydraulic: If pressure is low, check the relief valve, pump (internal wear), and clogged filters. Cavitation produces a gravel-like noise and high temperature.

Pneumatic: A pressure drop may indicate a leak. Use an ultrasonic detector. Check the air dryer and dew point (maximum 10 °C below ambient temperature).

Specific Calculations and Measurements

Power and Torque Calculation

For a shaft rotating at N rpm, torque T (N·m) is related to power P (W) by:

P = T × ω, where ω = 2πN / 60.

Therefore T = (P × 60) / (2πN) = (9,548 × P) / N (with P in kW).

Example: A 15 kW motor at 1,750 rpm delivers a torque of (9,548 × 15) / 1,750 = 81.8 N·m.

Fit Tolerance Calculations

Clearance and interference fits are defined by ISO 286 standards. For a bearing mounted on a shaft, the typical fit is k6 (light interference). The internal clearance of a radial ball bearing is classified as C2 (reduced clearance), CN (normal), C3 (increased clearance). C3 clearance is required for high temperatures or tight fits on both rings.

Resonance Frequency Calculation

The natural frequency of a mass-spring system is f = (1/2π) × √(k/m). If the excitation frequency (rotational speed) coincides with the natural frequency, resonance occurs and vibrations are amplified. The solution is to modify the mass or stiffness, or change the speed.

Belt Tension Verification

The deflection method: measure the distance between pulleys (L). The deflection at the center should be approximately 1/64 of L per inch of span (i.e., 1.5 mm per 100 mm). Use a frequency tensiometer for synchronous belts.

Applicable Canadian Standards and Codes

Canadian Electrical Code, Part I (CE Code), Chapter V

The Canadian Electrical Code, Part I (CE Code) (CSA C22.1) governs electrical installations. Although the industrial mechanic is not an electrician, you must know safety clearances and lockout requirements. Rule 8-200 covers wiring methods for industrial machinery. Rule 2-024 requires that work be performed by qualified persons.

CSA B149.1 (Natural Gas and Propane Installation Code)

If you work on gas-fired equipment (boilers, furnaces), CSA B149.1 applies. Rule 5.4 requires adequate ventilation. Rule 6.2 specifies minimum clearances around appliances. You must verify supply pressure (typically 7 inches of water column for residential natural gas, 11 inches for commercial).

CSA Z432 (Safeguarding of Machinery)

This standard defines requirements for guards and safety devices. Fixed guards must only be removed with a tool. Interlocking devices must stop the machine before access to the danger zone.

ISO 10816 (Mechanical Vibration)

Already mentioned, this standard is the reference for evaluating vibration on rotating machinery. It classifies machines into categories (I: small machines, II: medium machines, III: large machines on rigid foundations, IV: large machines on flexible foundations).

OSHA/CSA for Lockout/Tagout

CSA Z460 is the Canadian reference standard for the control of hazardous energy. It requires a written program, machine-specific procedures, and annual worker training.

Diagnostic Tools and Their Uses

Tool	Measurement	Typical Application	Limitation
Portable Vibrometer	mm/s, g	Overall monitoring	No frequency analysis
FFT Analyzer	Spectrum	Precise diagnosis	High cost, training required
Infrared Thermometer	°C	Surface temperature	Emissivity, distance
Thermal Camera	Thermal image	Electrical panels, bearings	Reflection, viewing angle
Stroboscope	rpm	Non-contact speed	Ambient light
Ultrasonic Detector	dB	Air leaks, bearings	Limited range
Inside Micrometer	mm	Bore measurements	0.001 mm precision
Dial Indicator	mm	Axial play, runout	Rigid mounting required

Pitfalls to Avoid

101.Confusing cause and effect: A noisy bearing is not always the cause; it may be the victim of misalignment or unbalance. Diagnose before replacing.

102.Ignoring thermal expansion: Aligning cold without compensating for thermal growth leads to rapid failure. Use manufacturer growth values.

103.Over-greasing bearings: The cavity should be filled to 30-50%, not 100%. Over-greasing causes temperature rise and premature failure.

104.Forgetting to check residual energy: A capacitor can remain charged, a hydraulic cylinder can fall by gravity. Always perform the zero-energy test.

105.Using the wrong vibration unit: Velocity (mm/s) is for low frequencies, acceleration (g) for high frequencies. Comparing values of different natures is an error.

106.Neglecting lockout/tagout standards: Each worker must have their own lock. A group lock is not a valid alternative.

107.Mixing incompatible greases: This can liquefy the grease and destroy the bearing. Check the soap type.

108.Ignoring alarm thresholds: A vibration of 4.5 mm/s is acceptable for a Category III machine, but dangerous for a small Category I pump. Know your machine's category.

109.Not documenting measurements: Without history, you cannot detect trends. Condition-based maintenance relies on comparison over time.

110.Working on a pressurized system: Always bleed accumulators and verify zero pressure with a reliable gauge.

Summary

Preventive maintenance is planned; condition-based maintenance is based on the actual machine condition. The choice depends on criticality and costs.

Lockout/tagout (CSA Z460) is non-negotiable: isolate, dissipate, verify.

Alignment tolerances depend on speed: 0.05 mm at 1,800 rpm, 0.03 mm at 3,600 rpm. Compensate for thermal expansion.

Vibration analysis uses ISO 10816 standards: Zone D (> 11.2 mm/s) = immediate shutdown. Frequencies 1X, 2X, and harmonics indicate faults.

Thermography and oil analysis are powerful complements. A 10 °C deviation or a rise in TAN are alarm signals.

Torque calculations (T = 9,548 × P / N) and resonance frequency (f = 1/2π × √(k/m)) are exam essentials.

Canadian standards (CE Code Part I, CSA B149.1, CSA Z432, CSA Z460) define safety and installation requirements.

Document everything: trends are more important than absolute values.

Self-Assessment Questions (Red Seal Type)

123.A bearing rotates at 3,600 rpm. The measured vibration is 12 mm/s RMS. According to ISO 10816-3, what action should you take?

a) Continue production, it's acceptable.

b) Plan a shutdown in 3 months.

c) Shut down the machine immediately.

d) Increase lubrication.

128.What is the characteristic frequency of unbalance on a rotating machine?

a) 0.5× speed

b) 1× speed

c) 2× speed

d) Random frequency

133.A hydraulic accumulator must be:

a) Isolated by a valve and left pressurized.

b) Bled and verified at zero before intervention.

c) Removed without precautions.

d) Filled with nitrogen before shutdown.

138.The cavity of a bearing should be filled with grease to:

a) 100%

b) 70% for high speeds

c) 30-50% for high speeds

d) 10% for all speeds

143.A 30 kW motor at 1,750 rpm transmits a torque of approximately:

a) 100 N·m

b) 164 N·m

c) 250 N·m

d) 50 N·m

Answers: 1-c, 2-b, 3-b, 4-c, 5-b (T = 9,548 × 30 / 1,750 = 163.7 N·m).

Preventive Maintenance, Troubleshooting, and Diagnostics