Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Apply systematic fault-finding techniques.
• Use diagnostic tools and measuring instruments.
• Perform preventive maintenance procedures.
• Evaluate the effectiveness of maintenance.
• Follow safety procedures during maintenance.

Lesson summary

Fault finding and maintenance procedures are critical skills in Mechanical Technology. They form the backbone of ensuring the efficient, safe, and reliable operation of machinery and equipment. In the South African context, these skills are particularly valuable. They lead to reduced downtime in industries, contribute to the longevity of vital equipment in communities (like water pumps and agricultural machinery), and create job opportunities for skilled technicians. Neglecting maintenance can lead to costly repairs, accidents, and ultimately hinder economic productivity.

Lesson notes

Fault finding is the process of systematically identifying the cause of a malfunction in a system or piece of equipment. Maintenance procedures are actions taken to prevent malfunctions, extend the life of equipment, and ensure its reliable operation. These are intertwined - good maintenance reduces the frequency of fault-finding, and effective fault-finding informs improved maintenance practices.

A. Systematic Fault Finding: The foundation of effective fault-finding is a systematic approach. A recommended method includes the following steps: Define the Problem: Clearly identify the symptoms and conditions under which the fault occurs. Be specific. For example, instead of "The engine is making a noise," describe it as "The engine makes a knocking noise when accelerating between 2000 and 3000 RPM." Gather information from operators, maintenance logs, and your own observations.

Gather Information: Collect all relevant data, including operating manuals, schematics, maintenance records, and the equipment's history. Understand the normal operation of the system.

List Possible Causes: Based on the symptoms and information gathered, generate a list of potential causes. Prioritize the most likely causes based on experience and available evidence. This is where your knowledge of the system's components and their interactions becomes critical.

Test and Verify: Systematically test each potential cause, starting with the most likely. Use appropriate measuring instruments (e.g., multimeter, pressure gauges, vibration analyzers) to gather data. Conduct visual inspections for damage, wear, or leaks. Isolate components to narrow down the source of the fault.

Repair or Replace: Once the cause is identified, repair or replace the faulty component according to manufacturer's specifications.

Test and Verify Repair: After the repair, thoroughly test the system to ensure the fault is resolved and the equipment is operating correctly.

Document: Record the fault, the cause, the repair action taken, and the results of the testing. This information is valuable for future troubleshooting and for improving maintenance schedules.

B. Maintenance Procedures: Maintenance can be classified into two main types: Preventive Maintenance: Scheduled maintenance tasks performed to prevent breakdowns and extend the life of equipment. Examples include lubrication, filter changes, belt tensioning, and visual inspections.

Corrective Maintenance: Maintenance performed to repair a malfunction that has already occurred. This is often unplanned and can be more costly than preventive maintenance. Key maintenance procedures related to mechanical systems include: Lubrication: Proper lubrication reduces friction and wear, extending the life of moving parts. Use the correct lubricant type and application method as specified by the manufacturer. Consider the operating temperature, speed, and load when selecting a lubricant. In South Africa, consider the availability and cost of different lubricants when creating a maintenance plan.

Inspection: Regular visual inspections can identify potential problems early. Look for signs of wear, damage, leaks, corrosion, and misalignment. Use checklists to ensure that all critical components are inspected.

Tightening: Loose fasteners can cause vibration, wear, and even catastrophic failure. Regularly check and tighten bolts, nuts, and screws to the specified torque.

Cleaning: Dirt and debris can interfere with the operation of mechanical components. Keep equipment clean to prevent overheating, contamination, and premature wear.

Alignment: Misalignment can cause excessive vibration, wear, and energy loss. Use precision alignment tools to ensure that shafts and couplings are properly aligned.

C. Measuring Instruments and Diagnostic Tools: Multimeter: Used to measure voltage, current, and resistance in electrical circuits, which can be related to mechanical systems (e.g., solenoid valve operation).

Pressure Gauges: Used to measure the pressure of fluids in hydraulic and pneumatic systems.

Torque Wrench: Used to tighten fasteners to the specified torque.

Feeler Gauges: Used to measure small gaps and clearances.

Dial Indicators: Used to measure runout and misalignment.

Vibration Analyzer: Used to detect and analyze vibration patterns, which can indicate problems with bearings, gears, or shafts.

Stroboscope: Used to visually "stop" rotating parts for inspection.

Infrared Thermometer: Used to measure the temperature of components without contact, which can indicate overheating.

D. Worked

Examples: Example 1: Identifying a Fault in a Belt Drive System A conveyor belt system in a maize milling plant is experiencing slippage.

Problem Definition: Conveyor belt is slipping under load, reducing throughput.

Information Gathering: Belt is relatively new (6 months old). Ambient temperature is high (35°C). Belt tension was checked 3 months ago.

Possible Causes:

1. Belt is loose.

2. Belt is worn.

3. Pulleys are worn. 4.