Mechanical Engineering: Strand 10 — Maintenance and Safety (Teaching Notes)

Maintenance

Set of activities used to keep equipment able to perform its required function, including inspecting, servicing, adjusting, repairing, and replacing parts.

Safety

Preventing harm from failures and from the maintenance work itself.

Reliability and uptime

Keeping systems available for production or service.

Life-cycle cost

Reducing the total cost of owning and operating equipment.

Failure mode

The specific way something fails, such as bearing pitting or corrosion thinning.

Degradation

The period where condition worsens before functional failure.

Early detection

Condition monitoring that allows for the timely identification of potential failures.

Corrective maintenance

Fixing or replacing an item after it fails, used when failure has low consequence.

Preventive maintenance (PM)

Scheduled work at set intervals to prevent wear-out before it occurs.

Condition-based maintenance (CBM)

Maintenance that triggers work based on measured condition of the equipment.

Proactive maintenance

Focuses on eliminating the causes of degradation instead of treating symptoms.

Reliability-centered maintenance (RCM)

A systematic method to select maintenance tasks based on functions and failure modes.

Total productive maintenance (TPM)

Emphasizes operator involvement and overall equipment effectiveness.

MTBF (Mean Time Between Failures)

The average time between failures in repairable systems.

MTTR (Mean Time To Repair)

The average time to restore function after a failure has occurred.

Availability

A measure of the reliability of a system, expressed by the formula A = MTBF / (MTBF + MTTR).

Exponential failure model

A model that approximates failures as a constant failure rate process.

Job Safety Analysis (JSA)

A tool to identify hazards step-by-step and define controls.

Work order

A formal instruction and record for a maintenance task.

Job plan

A reusable template for recurring maintenance work to reduce variability.

Post-maintenance testing (PMT)

Testing performed after maintenance to catch defects before returning equipment to service.

Condition monitoring

Repeated measurement to detect changes in equipment condition over time.

Nondestructive testing (NDT)

Methods to detect cracks or flaws without cutting parts apart.

Vibration monitoring

Analyzing vibration patterns to detect faults in rotating machinery.

Thermography

Using infrared imaging to detect temperature patterns and identify overheating components.

Oil analysis

Test to reveal wear metals and contamination in lubricants.

Friction

The resistance that one surface or object encounters when moving over another.

Wear mechanisms

Processes that cause material removal or degradation, such as abrasive wear or adhesive wear.

Lubrication regimes

Different states of lubrication based on film thickness, such as hydrodynamic and elastohydrodynamic lubrication.

Hierarchy of controls

A system for prioritizing risk controls from elimination to PPE.

Lockout/Tagout (LOTO)

A safety procedure to ensure that dangerous machines are properly shut off and not started up again prior to the completion of maintenance.

Emergency stop

A safety device used to stop machinery quickly in case of emergency.

Management of Change (MOC)

A process to ensure any changes to the system are reviewed for safety and reliability impacts.

Human factors

Elements that influence human behavior in a work environment, affecting safety and performance.

Ergonomics

The study of people's efficiency in their working environment.

Near miss

An event that could have resulted in harm but did not.

Root cause analysis (RCA)

Systematic investigation aimed at identifying the underlying cause of a problem.

Repeat failure rate

The frequency at which repairs need to be repeated over a specified period.

Performance metrics

Quantitative measures used to assess and manage improvement in maintenance and safety.

Rigging safety

Safety practices and calculations used when lifting and moving heavy loads.

Sling angle

The angle that sling legs make with the vertical, affecting tension distribution.

Hazard identification

The process of recognizing hazards that could cause harm in the workplace.

High-risk work permits

Formal permissions required for maintenance tasks that involve significant hazards, like hot work or confined spaces.

Contamination control

Methods used to prevent contamination in lubricants and components.

Visual inspection

A systematic examination of equipment to identify any visible signs of wear or potential failure.

Condition monitoring data

Data collected over time to assess the health and performance of equipment.