Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Identify five common causes of bearing failure.
• Apply a systematic fault-finding procedure.
• Describe the importance and procedure of lubrication.
• Perform basic alignment checks on a shaft coupling.
• Explain the role of vibration analysis in maintenance.

Lesson summary

This week, we delve into the crucial aspects of fault finding and maintenance procedures in mechanical systems. Understanding these concepts is not just theoretical; it's profoundly practical. In a country like South Africa, where infrastructure and machinery are vital for industries ranging from mining to agriculture to manufacturing, the ability to quickly diagnose problems and implement effective maintenance is essential for economic productivity, safety, and sustainability. Preventative maintenance can save businesses (and individuals) significant costs by averting catastrophic failures and extending the lifespan of valuable equipment.

Lesson notes

2.1 Common Causes of Bearing Failure Bearings are critical components in rotating machinery, facilitating smooth and efficient operation. Their failure can lead to significant downtime and costly repairs. Understanding the common causes of bearing failure is crucial for effective fault finding and preventative maintenance.

Contamination: This is a leading cause of bearing failure. Dirt, dust, grit, metal particles, and moisture can enter the bearing, acting as abrasives and causing wear and damage to the rolling elements and raceways. In South Africa, dust from mines and agricultural activities is a common contaminant.

Lack of Lubrication: Lubrication reduces friction and wear between moving parts. Insufficient lubrication, using the wrong type of lubricant, or lubricant degradation (due to age or contamination) can lead to metal-to-metal contact, generating excessive heat and ultimately causing bearing failure. Consider the climate in certain regions; high temperatures require lubricants with specific viscosity.

Overloading: Exceeding the bearing's load rating can cause premature fatigue and failure. This can be due to excessive weight, misalignment, or shock loads. In industries like mining, heavy machinery is often subjected to extreme loads.

Misalignment: Misalignment occurs when the shaft or housing is not properly aligned. This can create uneven loading on the bearing, leading to increased stress and wear. Types of misalignment include angular misalignment (shafts are at an angle) and parallel misalignment (shafts are offset).

Improper Installation: Incorrect installation techniques, such as using excessive force during mounting or improper seating, can damage the bearing and reduce its lifespan.

Corrosion: Exposure to corrosive environments (e.g., coastal regions with high salt content or industrial environments with chemical fumes) can cause corrosion of the bearing components, leading to weakening and failure. 2.2 Systematic Fault-Finding Procedure A systematic approach to fault finding is essential for efficiently diagnosing problems in mechanical systems. This involves a logical and structured process to identify the root cause of the issue.

Identify the Problem: Clearly define the problem. What are the symptoms? What is not working as expected? Gather information from operators, maintenance records, and observations.

For example: "The pump is making a loud grinding noise and the flow rate is significantly reduced." Gather Information: Collect all relevant information about the system, including operating conditions, maintenance history, and any recent changes.

Develop a Hypothesis: Based on the information gathered, formulate a hypothesis about the potential cause of the problem. This should be a specific and testable explanation.

For example: "The grinding noise could be due to a damaged bearing in the pump motor." Test the Hypothesis: Perform tests and inspections to confirm or refute the hypothesis. This may involve visual inspections, measurements, and functional tests.

For example: "Inspect the pump motor bearing for signs of wear, damage, or excessive play. Measure the bearing temperature." Analyze the Results: Evaluate the results of the tests and inspections. Does the evidence support the hypothesis? If not, revise the hypothesis and repeat the testing process.

Implement the Solution: Once the root cause of the problem is identified, implement the appropriate solution. This may involve replacing a component, making adjustments, or performing repairs.

Verify the Solution: After implementing the solution, verify that the problem has been resolved and that the system is operating correctly. Monitor the system for any recurrence of the problem. 2.3 Lubrication of Bearings Proper lubrication is critical for extending the lifespan of bearings. Lubrication reduces friction, removes heat, and protects against corrosion.

Types of Lubricants: Common lubricants include grease and oil. Grease is a semi-solid lubricant that is typically used in bearings that operate at low to moderate speeds and temperatures. Oil is a liquid lubricant that is used in bearings that operate at high speeds and temperatures. Selecting the correct lubricant type and viscosity is crucial for specific applications. Considerations include operating temperature, speed, load, and environmental conditions.

Lubrication Procedure: Identify the lubrication points. Consult the equipment manual or lubrication chart. Clean the lubrication fitting. Use a grease gun or oil can to apply the lubricant. Apply the correct amount of lubricant. Over-lubrication can be as detrimental as under-lubrication. Refer to the manufacturer's recommendations. Wipe away any excess lubricant. 2.4 Shaft Coupling Alignment Shaft couplings connect two shafts, allowing them to transmit power while accommodating some degree of misalignment. Proper alignment is essential for preventing premature wear and failure of the coupling and connected equipment.