Top 20 Mechanical Engineering Interview Questions in Oil & Gas Industry

The oil and gas industry is one of the most demanding yet rewarding sectors for mechanical engineers. Whether you're aiming for a role in upstream, midstream, or downstream operations, interviewers will test your technical know-how, industry awareness, and problem-solving skills. To help you prepare, we’ve compiled a list of the top 20 mechanical engineering interview questions commonly asked in oil and gas job interviews.

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🔧 Technical Questions

1. What is the difference between a pipe and a tube?

Answer: Pipes are generally used to transport fluids and are specified by their nominal diameter and schedule (wall thickness). Tubes are used for structural purposes and are defined by their actual outer diameter and wall thickness.

2. Explain the difference between API 5L and ASTM standards.

Answer: API 5L is specific to line pipes used in oil and gas transportation, while ASTM standards cover a wide range of materials and applications beyond oil and gas.

3. What is a Piping and Instrumentation Diagram (P&ID)?

Answer: A P&ID is a detailed schematic that shows piping, equipment, instrumentation, and control systems in a process plant.

4. What is the significance of ASME B31.3?

Answer: It is the American Society of Mechanical Engineers code for Process Piping, widely used in oil and gas industries for designing and constructing piping systems.

5. What are the types of corrosion encountered in pipelines?

Answer: Common types include uniform corrosion, pitting corrosion, galvanic corrosion, and stress corrosion cracking.

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🛠 Equipment and Systems

6. How do you select a pump for oil and gas applications?

Answer: Selection depends on flow rate, pressure, fluid type, viscosity, temperature, and specific process requirements.

7. What’s the difference between a reciprocating and centrifugal compressor?

Answer: Reciprocating compressors are suitable for high pressure and low flow applications, while centrifugal compressors are ideal for high flow and moderate pressure.

8. What is a heat exchanger and where is it used in oil & gas?

Answer: A heat exchanger transfers heat between fluids. It's used in refineries, LNG plants, and offshore platforms for cooling or heating process streams.

9. What is NPSH in pumps?

Answer: Net Positive Suction Head (NPSH) is the absolute pressure at the suction port of the pump. It’s crucial to avoid cavitation.

10. What is a pressure safety valve (PSV) and how does it work?

Answer: A PSV prevents overpressure by releasing excess pressure once a set limit is exceeded, ensuring safe operation.

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🛡 Standards, Safety & Reliability

11. What is HAZOP?

Answer: Hazard and Operability Study is a structured method to identify potential hazards and operability issues in processes.

12. What are the types of maintenance used in oil & gas?

Answer: Preventive, predictive, and corrective maintenance are most common. Condition-based monitoring is also widely applied.

13. What is the difference between stress and strain?

Answer: Stress is the internal force per unit area within materials, while strain is the deformation caused by stress.

14. What is fatigue failure and why is it critical in offshore structures?

Answer: Fatigue failure occurs due to cyclic loading over time. In offshore environments, wave and wind loads make fatigue a significant concern.

15. What is the role of a mechanical engineer in a shutdown/turnaround?

Answer: Responsibilities include inspection, repair planning, equipment overhauling, and coordination with contractors to ensure smooth execution.

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🎯 Behavioral & Scenario-Based Questions

16. Describe a challenging project you worked on in the oil and gas industry.

Tip: Use the STAR method (Situation, Task, Action, Result) to structure your answer.

17. How do you prioritize tasks during an emergency breakdown?

Answer: Focus on isolating the fault, ensuring safety, coordinating with operations, and using risk-based prioritization.

18. What would you do if a safety-critical component failed during operation?

Answer: Isolate the system, report immediately, follow emergency protocols, and support root cause analysis.

19. How do you stay updated with industry standards and practices?

Answer: Mention reading standards (e.g., ASME, API), attending conferences, online training, or technical communities.

20. Have you ever disagreed with a team member about a technical issue? How did you handle it?

Answer: Highlight your ability to communicate professionally, validate data, involve subject matter experts, and find solutions collaboratively.

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📘 Final Tips

• Know the codes: Familiarize yourself with ASME, API, ISO, and NACE standards.

• Understand equipment fundamentals: Be ready to talk about compressors, valves, pumps, and exchangers.

• Demonstrate safety mindset: Oil and gas places a high value on HSE awareness.

• Prepare your experience stories: Tailor your achievements to reflect leadership, problem-solving, and engineering judgment.