Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Identify common faults and their causes.
• Apply a systematic fault-finding approach.
• Explain and perform preventative maintenance.
• Use measuring instruments for maintenance tasks.
• Apply safety precautions during maintenance.

Lesson summary

Fault finding and maintenance procedures are absolutely crucial in the field of Mechanical Technology. In South Africa, where industries like mining, manufacturing, agriculture, and transport are significant employers, understanding how to identify and rectify faults, and how to proactively maintain equipment, is a highly valuable skill. Think about the impact of a broken-down tractor on a Free State farm during harvest season, or a malfunctioning conveyor belt in a Gauteng factory – downtime is costly and can impact livelihoods. This week we delve into the essential processes that keep machines running smoothly and efficiently, minimizing disruptions and maximizing lifespan.

Lesson notes

2. 1. What is Fault Finding? Fault finding is the systematic process of identifying the root cause of a malfunction or defect in a mechanical system. It involves a logical approach to pinpointing the source of the problem, allowing for effective repairs. Think of it like a detective solving a case - clues are gathered, analyzed, and pieced together to arrive at the culprit. 2.

2. A Systematic Approach to Fault Finding: A systematic approach is vital to avoid guesswork and wasted time. A common and effective approach includes the following steps: Observation: Carefully observe the machine in operation (if possible) or examine the faulty component. Note any unusual noises, vibrations, smells, leaks, or visible damage. For example, if a belt drive system is making a squealing noise, observe the belt's condition, tension, and alignment with the pulleys.

Questioning: Gather information from the operator or anyone familiar with the machine. Ask about the history of the problem, recent maintenance, and any unusual occurrences. This is particularly important in a workshop environment where communication between operators and technicians is key.

Testing: Use appropriate testing methods and equipment to verify your suspicions. This might involve using multimeters to check electrical circuits (if applicable), pressure gauges to measure fluid pressures, or vibration analyzers to detect imbalances.

Measurement: Take precise measurements of critical components using instruments like vernier calipers, micrometers, and feeler gauges. Compare these measurements to the manufacturer's specifications to identify any deviations. For example, measuring the thickness of brake pads to check for wear.

Deduction: Based on your observations, questioning, testing, and measurements, logically deduce the most likely cause of the fault. Consider all possibilities and eliminate those that don't fit the evidence.

Repair/Replacement: Once the fault is identified, repair or replace the faulty component according to the manufacturer's instructions.

Testing after Repair: After the repair, thoroughly test the machine to ensure the fault has been rectified and that the machine is operating correctly. 2.

3. Common Mechanical Faults: Wear and Tear: Gradual degradation of components due to friction, stress, and environmental factors. Examples include worn bearings, brake pads, gears, and belts.

Misalignment: Incorrect alignment of components, leading to increased friction, vibration, and premature wear. This is common in shaft couplings and belt drive systems.

Looseness: Loose fasteners (bolts, nuts, screws) can cause components to vibrate, shift, and eventually fail.

Lubrication Failure: Insufficient or incorrect lubrication can lead to increased friction, heat, and wear. Examples include dry bearings and insufficient oil in engines.

Overload: Operating a machine beyond its design capacity can cause stress, deformation, and failure.

Corrosion: Degradation of materials due to chemical reactions with the environment. This is a significant problem in coastal areas of South Africa.

Contamination: Dirt, dust, and other contaminants can enter mechanical systems and cause wear and blockages. 2.

4. What is Preventative Maintenance? Preventative maintenance is a proactive approach to maintaining mechanical systems by performing regular inspections, servicing, and repairs to prevent breakdowns and extend the lifespan of equipment. It's about being proactive rather than reactive. A well-maintained machine runs more efficiently, lasts longer, and is less likely to experience unexpected failures. 2.

5. Preventative Maintenance Procedures: Lubrication: Applying lubricants (oil, grease) to reduce friction and wear between moving parts. Different lubricants are required for different applications – understand the manufacturer's recommendation. Consider the types of grease used in a wheel bearing versus the oil used in an engine.

Cleaning: Removing dirt, dust, and other contaminants that can damage mechanical components. Regular cleaning of air filters is essential for engine performance.

Inspection: Visually inspecting components for signs of wear, damage, or leaks. This can include checking belts for cracks, hoses for leaks, and bearings for play.

Tightening: Regularly checking and tightening fasteners to prevent looseness.

Adjustment: Adjusting components to maintain optimal performance. Examples include adjusting valve clearances in engines or chain tension in chain drives.

Replacement of Consumables: Replacing parts that have a limited lifespan, such as filters, belts, and hoses. 2.

6. Measuring Instruments for Maintenance: Vernier Calipers: Used to measure internal and external diameters, depths, and thicknesses with high accuracy.

Micrometers: Used to measure very small distances with even higher accuracy than vernier calipers.

Feeler Gauges: Used to measure small gaps between surfaces, such as valve clearances or spark plug gaps.