Importance of Technical Interviews for PSU Jobs & M.Tech Admissions
Technical interviews are a key step in identifying an engineering candidate’s abilities beyond written exams. A strong GATE score shows good conceptual knowledge, but the interview reveals how well a student can apply those concepts in real situations, think logically, and handle practical challenges.
In PSU selections, technical interviews are extremely important because engineers in these organizations work directly with plant operations, safety systems, troubleshooting, and process optimization. The interview helps assess whether a candidate can convert theoretical understanding into sound decisions in real industrial environments.
For M.Tech admissions, the technical interview allows faculty to evaluate a student’s research potential, depth of subject knowledge, clarity in fundamentals, and readiness for advanced academic work. It helps institutions choose students who are not only good in exams but also show analytical ability, creativity, and genuine interest in specialized fields.
In summary, technical interviews ensure that candidates selected for PSUs or top institutes like IITs and NITs are skilled, confident, and capable of performing effectively—whether in professional roles or research-oriented studies.
GATE/ PSUs CHEMICAL ENGINEERING INTERVIEW QUESTION
1. Fluid Mechanics & Bernoulli’s Principles
- State Bernoulli’s equation and explain its assumptions and industrial applications.
- Is Bernoulli’s equation applicable to liquids, gases, or both? Under what conditions?
- Define cavitation, vapor-lock, and vapor binding. Causes, effects, and remedies.
- What is NPSH (Available & Required)? How can NPSH be increased without changing tank level or pump?
- Explain priming. How is priming done practically?
- How do you start a centrifugal pump?
- What happens when the discharge valve of a centrifugal pump is closed?
- Which pump is suitable for dirty or solid-laden fluids?
- Which pump is used when no solid particles are present?
- How to eliminate cavitation without changing head?
- Explain choke flow. How do you recover from choked flow?
- What is a nominal pipe size?
- What is Reynolds number? Significance?
- Explain friction factor and its dependence on Reynolds number and pipe roughness.
- Continuity equation for compressible and incompressible fluids—statement and applications.
- Bulk modulus of fluid—definition, dependency, and applications.
- Terminal settling velocity—factors affecting it.
- How is roughness of a surface estimated? Formula?
- Drag force on a body—formula and significance.
- Effect of pressure on reaction and flow systems.
2. Pumps, Compressors & Turbomachinery
- Draw and explain a pump characteristic curve, head curve, efficiency curve, and power curve.
- What are shut-off, BEP, and run-out points?
- Difference between PD and centrifugal pumps.
- PD pump vs PD compressor.
- Flow regulation techniques in PD pumps.
- Compressor surging—definition, causes, consequences, and multiple methods to prevent it.
- Stone wall limit and surge point.
- Compressor pressure is rising—what are possible reasons?
- Maximum suction lift of a centrifugal pump (≈ 34 ft for water)—explain why.
- Different types of turbines and their applications.
- Methods for moving a rotor (electric motor, turbine, hydraulic motor, etc.).
3. Heat Transfer & Heat Exchangers
- Modes of heat transfer—explain with examples.
- Fourier’s law of heat conduction—statement and application.
- Types of heat exchangers (S&T, plate, finned, double-pipe, etc.).
- Which heat exchanger is most efficient and why?
- Which heat exchanger should be used when a fluid is at boiling point?
- LMTD and correction factor—why needed?
- Fouling factor—definition and role.
- Heat transfer area calculation from tubes.
- Adiabatic vs isothermal flow—differences and significance.
4. Thermodynamics & Thermodynamic Cycles
- State the laws of thermodynamics with examples.
- Draw and explain basic thermodynamic cycles (Carnot, Rankine, Brayton, Refrigeration).
- Explain the refrigeration cycle.
- What is adiabatic flame temperature?
- Adiabatic saturation temperature—meaning & industrial relevance.
- Difference between evaporation and vaporization.
- Gas laws: Boyle’s, Charles’, General Gas Law—applications in industry.
- Humidity, RH, DBT, WBT—definitions, relations, and impact of temperature on humidity.
5. Distillation, Absorption & Mass Transfer
- Absorption—definition, factors affecting absorption, and effect of flow rate.
- Adsorption—mechanism, isotherms, and industrial applications.
- Difference between absorption and adsorption.
- Distillation basics: reflux ratio, flooding, weeping, entrainment.
- If heavy components go to the top of a column—how to control (multiple methods).
- Ways to reduce weeping in a distillation column.
- Packed vs tray column—advantages and limitations.
- Azeotropic distillation: role of entrainers.
- Nernst distribution law & eutectic point.
- Types of mass transfer equipment (spray dryer, packed tower, cyclone, etc.).
- Dimensionless numbers in mass transfer: Sherwood, Schmidt—significance.
6. Chemical Reaction Engineering
- Compare Batch, CSTR, PFR, PBR, FBR—applications & advantages.
- Activation energy—its significance.
- Effect of pressure on reaction rate.
- How to increase reactor productivity?
- Fixed bed reactor—working and applications.
- Catalyst—function, examples, and deactivation.
7. Process Safety, Plant Operation & PSI
- Occupational safety vs process safety—difference.
- Fire triangle—elements and mitigation.
- LEL & UEL—importance in plant safety.
- Flash point, fire point, auto-ignition temperature.
- PSV vs PRV—working, use cases, and gagging.
- Ensuring boiler safety—standard procedures.
- What happens when a gas heater runs in a closed room? Why deaths occur? (CO vs CO₂ toxicity).
- Maintaining inert atmosphere using nitrogen (for explosive grinding).
8. Process Control & Instrumentation
- Types of controllers: P, PI, PID, cascade, feed-forward, master-slave—applications.
- Types of sensors and their uses.
- Level control in boiler—what if the level transmitter fails?
- PNID vs PFD—differences and interpretation.
- Symbols used in PNID (valves, instruments, equipment).
- How to detect if particulate matter is removed after straining? Which sensor is suitable?
9. Environmental Engineering
- Greenhouse gases—examples and impact.
- Effluents in a chemical plant—major types.
- Methods to clean oil spills—hydrocyclone, decantation, skimming.
- Difference between flocculation and coagulation.
- Water hardness: P, M, PM values—measurement.
- Ion exchange method: exhaustion and regeneration.
10. Mechanical Operations & Particle Technology
- Volume, surface, and linear mean diameters—formulas.
- What is a 200-mesh screen? Opening size?
- Types of nucleation—primary, secondary, spurious; crystal growth modes.
- Sphericity and shape factor—definitions.
- Methods to determine equivalent particle diameter practically.
- Emulsion and emulsifiers—examples.
- Colloids, suspensions, aerosols, tinctures, amalgams—definitions & examples.
11. Petroleum Refining
- Petrol chemical formula.
- What is isomerization?
- Octane number—importance, and why branching increases it.
- Market octane number (petrol) & cetane number (diesel).
- Difference between 1-ton and 2-ton AC.
- Barrels to liters and gallons—conversion.
12. General Chemical Engineering Knowledge
- Why did you choose this final year project (FYP)?
- Difference between tube and pipe.
- How to design a pipeline from point A to B? Factors to consider.
- What is fugacity?
- Meaning of Oleum.
- Maximum concentration of H₂SO₄, HNO₃, HCl.
- What is surging?
- Let-down station—purpose and components.
- What happens in cooling towers during rain?
- Types of heat loss and gains in industrial processes.
15 high-quality subjective questions (collected from our Students) of Recent PSUs Recruitment process. These questions test practical, industrial, and concept-oriented knowledge of core Chemical Engineering subjects. These questions are suitable for interviews, viva, or advanced assessments for upcoming vacancies/recruitment/M.Tech program.
PSUs BARC, BIS, NPCIL Subjective Interview Questions (Industrial + Basic Concepts)
Meet our Technical Experts @ +91-9990357855
1. Fluid Mechanics / Pumps
Q1. In a running centrifugal pump, if the discharge valve is gradually closed, explain what happens to the pump head, flow rate, power consumption, and chances of cavitation.
Q2. A process line has high suspended solids. Explain how you would select a suitable pump and justify the choice with operating principles.
Q3. You observe abnormal vibration in a pump. List five industrial causes and how you would troubleshoot each cause.
2. Heat Transfer / Heat Exchangers
Q4. In a shell-and-tube heat exchanger, the process side fluid shows sudden drop in outlet temperature. Mention likely operational faults and methods to diagnose them on-site.
Q5. Explain why condensers prefer horizontal orientation while reboilers are often vertical. Relate your answer to drainage, heat transfer coefficient, and fouling.
Q6. How do fouling factors affect the design and long-term performance of heat exchangers? Provide two real industrial examples.
3. Mass Transfer / Distillation
Q7. You notice weeping at multiple trays in a distillation column. Describe the step-by-step method an operator should follow to minimize weeping without shutting down the column.
Q8. In an absorber removing SO₂ from flue gas, what happens to absorption efficiency if gas flow increases suddenly? Explain based on mass-transfer driving force and contact time.
Q9. A distillation column is giving off-spec top product purity. Name at least five process parameters you would check first and describe why each affects separation.
4. Thermodynamics / Energy
Q10. Explain why adiabatic flame temperature is lower in industrial furnaces compared to theoretical values. Describe at least three practical reasons.
Q11. Why does increasing pressure sometimes decrease the reaction rate in gas-phase reactions? Explain using concepts of rate law and collision frequency.
5. Mechanical / Safety / Process Equipment
Q12. What is compressor surge? Describe how an operator can detect it in real time and what immediate corrective actions are taken.
Q13. A storage tank shows rapid pressure rise during nitrogen blanketing. What operational faults might be responsible? How can you prevent such incidents?
6. Process Control / Instrumentation
Q14. A level transmitter in a reactor suddenly fails during continuous operation. Describe at least three alternative ways (operational or instrumentation) to maintain safe level control temporarily.
Q15. Explain the practical difference between feed-forward and feedback control in a distillation column. Provide one real industry example for each.
5 high-quality technical interview questions covering Thermodynamics, Heat Exchangers, Convection, Mass Equilibrium, Refinery, Paper–Pulp, Sugar, Polymer, and Process Control. These are application-oriented and suitable for PSU & industry interviews.
PSUs/GATE Chemical Engineering Technical Interview Questions (Mixed Industrial Topics)
1. Thermodynamics
Q1. Explain the difference between reversible and irreversible processes. Why are most industrial processes irreversible?
Q2. In a gas compressor, why does discharge temperature rise with pressure? Derive the relation for polytropic compression.
2. Heat Exchangers
Q3. Why is counter-flow heat exchange more efficient than parallel flow? Give one industrial example where counter-flow is preferred.
Q4. What factors lead to fouling in a shell-and-tube heat exchanger, and how does fouling influence overall heat-transfer coefficient?
3. Convection / Heat Transfer
Q5. Explain natural vs forced convection with one example each from a process plant.
Q6. How does increasing flow velocity affect the convective heat-transfer coefficient? Link your answer to Reynolds and Nusselt numbers.
4. Mass Equilibrium / Separation Processes
Q7. In a liquid–liquid extraction unit, how does the distribution coefficient influence the number of equilibrium stages?
Q8. Define “azeotrope.” How does azeotropic composition affect design of distillation columns in industry?
5. Refinery / Petrochemical
Q9. What is cracking in refinery operations? Compare thermal cracking and catalytic cracking with respect to temperature, pressure, and product quality.
Q10. What is the purpose of hydrotreating in petroleum refining? Name the main impurities removed and why.
6. Paper & Pulp Industry
Q11. Why is the Kraft process widely used in pulp manufacturing? Explain its chemical advantages and energy recovery benefits.
Q12. What is “black liquor,” and how is it treated or utilized in pulp mills?
7. Sugar Industry
Q13. Explain the concept of multiple-effect evaporators used in sugar manufacturing. How does it save steam compared to a single-effect unit?
8. Polymer / Polymeric Processes
Q14. Distinguish between step-growth and chain-growth polymerization with suitable industrial examples.
Q15. What factors affect the molecular weight of a polymer during polymerization? Discuss initiator concentration, temperature, and reaction time.
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