Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Apply a systematic fault-finding process.
• Perform basic maintenance procedures like lubrication and cleaning.
• Explain different types of preventative maintenance.
• Select appropriate tools and work safely.
• Document your work accurately.

Lesson summary

Fault finding and maintenance procedures are essential skills for any mechanical technician. In a country like South Africa, where industries ranging from mining to manufacturing heavily rely on machinery, the ability to diagnose and repair faults quickly and efficiently is crucial. This directly impacts productivity, safety, and the overall economy. For example, a broken-down conveyor belt in a gold mine can halt production, costing the company and the country significantly. Similarly, properly maintained agricultural machinery contributes to food security. Effective maintenance also prolongs the lifespan of equipment, reducing the need for costly replacements.

Lesson notes

2. 1.

Systematic Fault Finding: Fault finding should not be a haphazard process. A systematic approach saves time and increases the chances of identifying the root cause of the problem.

Common systematic approaches include: Observation: This involves carefully examining the machine or system, listening for unusual noises, smelling for burning odours, and visually inspecting for damage, leaks, or misalignment. For example, observing excessive vibration in a pump could indicate bearing failure or imbalance.

Gathering Information: Collecting information from the operator, maintenance logs, and technical manuals is crucial. The operator might have noticed warning signs or unusual behavior prior to the failure. The technical manual provides specifications and troubleshooting guides. 5 Whys: This technique involves repeatedly asking "why" to drill down to the root cause of a problem.

For example: Problem: The machine stopped working. Why? The motor overheated. Why? The cooling fan was not working. Why? The fan motor was burned out. Why? There was insufficient lubrication in the fan motor bearings. Why? The maintenance schedule for fan motor lubrication was not being followed. (Root Cause) Cause-and-Effect Diagram (Ishikawa/Fishbone Diagram): This tool helps identify potential causes of a problem by categorizing them into major areas such as manpower, methods, materials, machinery, environment, and measurement.

Half-Splitting: In a long system, dividing the system in half and testing at the midpoint can quickly isolate the faulty section. For example, in a long pipe run with low flow at the end, testing the pressure at the midpoint can determine whether the blockage is in the first or second half. 2.

2. Basic Maintenance Procedures: Lubrication: Applying lubricants (oil or grease) reduces friction between moving parts, minimizing wear and tear and preventing overheating. Different types of lubricants are used for different applications. Consider a wheel bearing on a bakkie. Grease is essential to reducing friction and preventing premature failure. A lack of grease or using the wrong type of grease can lead to bearing failure.

Cleaning: Removing dirt, dust, and debris prevents components from overheating, corroding, or malfunctioning. Cleaning also allows for better visual inspection. Imagine a tractor engine covered in mud; it will overheat more easily and prevent the operator from noticing potential leaks or cracks.

Tightening Fasteners: Loose bolts and screws can cause components to vibrate, misalign, or even detach, leading to failures. Regular tightening to specified torque values is essential. Consider the consequences of loose wheel nuts on a minibus taxi – a serious safety hazard.

Visual Inspections: Regular visual inspections can identify potential problems before they become major failures. Look for cracks, leaks, wear, corrosion, and misalignment. For example, regularly inspecting the condition of V-belts on agricultural machinery can prevent unexpected breakdowns during harvest season. 2.

3. Types of Preventative Maintenance: Time-Based Maintenance (TBM): Maintenance is performed at predetermined intervals, regardless of the condition of the equipment. For example, changing the engine oil in a car every 10,000 km or replacing air filters in an air conditioning system every six months.

Condition-Based Maintenance (CBM): Maintenance is performed based on the actual condition of the equipment, as determined by monitoring parameters such as vibration, temperature, oil analysis, and pressure. For example, using vibration analysis to detect bearing wear in a large electric motor and scheduling maintenance before the bearing fails completely.

Predictive Maintenance (PdM): Uses advanced techniques such as infrared thermography, ultrasonic testing, and oil analysis to predict when a component will fail, allowing maintenance to be scheduled proactively. This is similar to CBM but focuses on predicting future failures rather than reacting to current conditions. Think of using infrared cameras to detect hotspots in electrical panels, indicating loose connections that need to be tightened before they cause a fire. 2.

4. Tools and Equipment: Selecting the right tools for the job is crucial for safety and efficiency. Common tools used in fault finding and maintenance include: Multimeter: Used to measure voltage, current, and resistance in electrical circuits.

Torque wrench: Used to tighten fasteners to specified torque values.

Feeler gauges: Used to measure clearances between parts.

Vernier calipers: Used to measure internal and external dimensions accurately.

Infrared Thermometer: Used to measure temperature without contact. 2.

5. Documentation: Accurate and complete documentation is essential for tracking maintenance activities, identifying trends, and improving maintenance procedures.