Maintenance engineering questions and answers

Maintenance engineering is a crucial job in industrial plants, manufacturing facilities, utilities, oil and gas, HVAC systems, and heavy equipment operations. A well-designed maintenance program provides dependability, safety, uptime, and cost-effective operation. Whether you're a maintenance engineer, technician, student, or job seeker preparing for an interview, knowing real-world maintenance engineering questions and answers boosts your confidence.

In this blog article, we break down the most often requested maintenance engineering problems and provide practical, industry-oriented solutions. This resource is useful for rapid reference for interviews, competitive tests, and workplace problems.

1. What's the difference between preventive maintenance (PM) and predictive maintenance (PdM)?

Preventative Maintenance (PM):

• PM is a method of doing scheduled maintenance at regular intervals (daily, weekly, monthly, and annual). It seeks to avoid equipment failure by inspecting, lubricating, replacing worn parts, and cleaning.

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Predictive Maintenance (pdM):

• PdM is condition-based maintenance. It employs sensor and monitoring data—such as vibration analysis, thermography, oil analysis, and ultrasonic testing—to forecast equipment failure before it happens.

• The primary distinction between PM and PdM is that PM is time-based, while PdM is condition-based.

2. What are the MTBF and MTTR? How are they used?

• MTBF (Mean duration Between Failures) refers to a machine's average operating duration before failure. A higher MTBF suggests more dependability.

• MTTR (Mean Time To Repair) refers to the average time it takes to repair a breakdown and return equipment to operation.

Significance:

• The MTBF is a useful tool for measuring dependability.

• The MTTR helps to assess the maintainability and efficiency of repairs.

• They work together to make judgments on spare parts planning and maintenance budgets.

3. Why does equipment vibration rise, and how do you address it?

• Increased vibration is a reliable warning of mechanical issues in rotating equipment such pumps, motors, fans, gearboxes, and turbines.

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Common reasons include:

• Imbalance

• Misalignment

• Bearing wear

• Loose components

• Bent shafts

• Gear tooth damage.

• Resonance

Troubleshooting Method:

• Conduct a visual assessment.

• Examine for looseness or foundation concerns.

• Align using laser alignment equipment.

• Inspect the bearings for noise or temperature increase.

• Perform vibration analysis to locate frequencies.

• Balance spinning components if necessary.

4. What is Root Cause Analysis (RCA), and why is it important?

• RCA identifies the underlying reason of a failure rather than addressing the symptoms. Maintenance crews employ RCA to prevent recurring malfunctions.

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Common root cause analysis tools:

• 5 Why Analysis

• Fishbone (Ishikawa) Diagram.

• Fault tree analysis (FTA)

• Pareto Chart

Benefits of RCA include reduced downtime, prevention of reoccurring failures, and increased equipment safety and dependability.

5. What are the many kinds of maintenance practices in industries?

• Corrective maintenance is the process of repairing following a failure.

• Preventive maintenance is time-based periodic service.

• Predictive maintenance is based on condition monitoring.

• Reliability-Centered Maintenance (RCM) is a strategy that focuses on criticality and failure modes.

• Proactive Maintenance - Removes the fundamental causes of failure.

• Breakdown Maintenance - Run-to-failure technique (for non-critical components).

6. How do you choose an appropriate lubricating technique for mechanical equipment?

Lubrication relies on:

• Operating temperature

• Speed (rpm)

• load and pressure.

• Environment (dusty, corrosive, and humid)

• Equipment type (bearings, gears, couplings, and chains)

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Common Lubrication Methods:

• Grease lubrication (low-speed bearings).

• Oil bath or splash lubrication (gearboxes).

• Mist lubrication (for high-speed rotating equipment).

• Automatic lubrication systems (for huge industrial systems)

7. What is the use of a CMMS in maintenance engineering?

A Computerized Maintenance Management System (CMMS) helps to digitize and simplify maintenance activities.

Key Functions:

• Job scheduling and tracking.

• Storing equipment history

• Spare parts inventory management

• Preventive Maintenance Planning

• Work Order Management

• Downtime analysis

8. Why does a pump lose prime, and how can you fix it?

Pump priming concerns are most common with centrifugal pumps.

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Common Causes:

• Air leak in the suction line

• Low liquid level in the tank.

• Blocked foot valve.

• Incorrect pump rotation.

• Vapor formation (cavitation).

Solutions:

• Maintain airtight suction lines.

• Fill the pump's casing with liquid.

• Clean and fix the foot valve.

• Check the rotation direction.

• Maintain the correct Net Positive Suction Head (NPSH).

9. What causes bearing failure and how is it prevented?

Common Causes:

• Over or under-lubrication

• Contamination (dust and wetness)

• Misalignment

• Overloading

• Poor installation.

• Electrical Fluting in Motors

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Prevention:

• Follow a correct lubrication routine.

• Use the suitable bearing type and size.

• Ensure shaft alignment.

• Control contamination using seals and filters.

• Use insulated bearings for motors that are susceptible to electrical discharge.

10. Why is torque tightening necessary in maintenance?

Bolt torque determines clamping force. Joints loosen if they are under tightened, whereas bolts may fail if they are overtightened.

Importance:

• Prevents mechanical breakdown.

• ensures structural integrity.

• Improves safety.

• protects spinning equipment against imbalance and vibration.

• Torque wrenches, hydraulic tensioners, and pneumatic torque tools were employed.

Maintenance engineering questions and answers