Interview Questions.

Chemical Engineering Interview Questions and Answers - Jul 16, 2022


Chemical Engineering Interview Questions and Answers

Q1. Explain the 1/3 regulation of thermodynamics.

Ans: The third regulation states that 'As a machine tactics absolute 0, the entropy of the machine tactics a minimal cost'.

Q2. What is the Driving force for fluid float?

Ans: Driving pressure for fluid flow is Energy in line with unit mass or general head available on the point of vicinity.

Q3. What are a few factors to recall while attempting selecting between a dry screw compressor and an oil-flooded screw compressor?

Ans: Screw compressors utilize a couple of “meshing” helical screws to compress gases. These forms of compressors a usually appropriate for a float range of eighty five-170 m3/h (3000-6000 acfm) and discharge pressures inside the range of 2070-2760 kPa (three hundred-400 psig). As the call implies, dry screw compressor run dry while oil-flooded compressors use oil for bearing lubrication as well as to seal the compression chamber. The oil additionally consists of the warmth from the compression far from the compressor. This heat is usually rejected to an outside warmness exchanger. Some elements to take into account while deciding on among the two varieties of screw compressors consist of

Q4. What are a few not unusual reasons of fuel pipeline vibration 20 Carbon Steel line?Chemical interview questions.Docx

Ans: The upper stress variety and /or the smaller pipe diameters prompts me to analyze the possibility that the gas is achieving critical float someplace downstream in the pipe. When a gas gets to critical glide, sonic booms (producing vibration) are expected. In truth, one of the most important means by using which the extra pressure within the pipe is misplaced.

If the  source is a compressor, search for surging.

If the source is a tower, search for stress cycling inside the tower

Look at critical waft thru any manage valve that may be inside the line.

Are there any vapors within the line, which can condense and produce -phase flow? Two-section waft can purpose vibration.

In chemical plant layout, if we suspect -section glide, we educate the piping designers to provide unique anchoring.

Q5. What is entropy?

Ans: Entropy is a degree of disorderliness. It explains the device's closeness to equilibrium.

Q6. Pressure drop equation for horizontal pipe line in laminar waft situation?

Ans: In fluid dynamics, the Hagen–Poiseuille equation is a physical law that gives the stress drop in a fluid flowing thru a protracted cylindrical pipe. The assumptions of the equation are that the float is laminar viscous and incompressible and the glide is thru a steady round move-phase this is extensively longer than its diameter. The equation is likewise called the Hagen–Poiseuille regulation, Poiseuille law and Poiseuille equation.

The governing equation is,

Q7. Under what situations are vortex flowmeters the most correct?

Ans: The accuracy of vortex flowmeters can be within 1% so long as they’re being working inside their recommended waft range, have a consistent stream, and you've got 10 pipe diameters of straight pipe at the back of the in front of the flowmeters. Outside of those parameters, these flowmeters are not accurate.

The vortex flowmeter is used for measuring the float velocity of gases and liquids in pipelines flowing full. The measuring precept is primarily based at the develo.Ent of a Karman vortex shedding road within the wake of a body constructed into the pipeline.

Q8. While there, are many assessments to be had to stumble on leaks on vessels, is there a generation available to quantify the leak, or degree the glide via a leak?

Ans: The RheoVac air in-leak screen via Intek, Inc. In Westerville, OH is a feasible meter that gives the real air in-leakage glide charge. It additionally gives you exhauster capacity and a vacuum excellent analyzing.

Q9. Draw the willing manometer diagram?

Ans: Inclined manometer may be built in lots of approaches in line with our motive.

Most commonplace one is as proven inside the diagram

HubSpot Video

Q10. What is Gibbs loose electricity?

Ans: It is the to be had strength or the best amount of mechanical paintings performed by means of a device at consistent temperature and stress.

Q11. Is there any manner to repair a valve this is passing leaking internally with out taking our method offline?

Ans: A six hundred psig, three" steam line is experiencing "passing" or inner leakage. If you order to update the valve, the technique could must be taken offline. A temporary option to the problem is sought to get the plant to their next scheduled close down ANSWER Research on-circulation leak sealing offerings. This trouble is quite common. What they could do in this example is drill a hollow into the skip valve at the upstream aspect however no longer completely into the line. They would then tap the hollow and set up considered one of your injection fittings, which is like a small plug valve. They might then take an extended 1/8" drill bit and drill via the open injection becoming and into the pressurized line. The drill bit is then eliminated and our injection equipment is then connected. Sealant (heavy fibers and grease) is pumped into the road and caught within the go with the flow, so that it will bind up against the leaking seat at the skip valve. If performed nicely, this method can be each powerful and safe.

Q12. What are the advantages and drawbacks of the use of equipment pumps?

Ans: Gear pumps are a sort of wonderful displacement pump which can be appropriate for pumping particularly excessive pressures and occasional capacities. Advantages consist of the potential to deal with a wide range of viscosities, much less sensitivity to cavitation (than centrifugal fashion pumps), relatively simple to keep and rebuild. Disadvantages can encompass a confined array of materials of creation because of tight tolerances required, excessive shear located at the liquid, and the fluid ought to be free of abrasives. Also, note that gear pumps should be managed via the motor pace. Throttling the release isn't a suitable way of manage.

Q13. At what temperature does water have most density?

Ans: At four deg C the density of water is 1000 kg/cu.M.

Q14. Definition of NPSH? 

Ans: NPSH is an acronym for Net Positive Suction Head. In any pass-section of a common hydraulic circuit, the NPSH parameter suggests the distinction among the real pressure of a liquid in a pipeline and the liquid's vapor pressure at a given temperature.

NPSH is an important parameter to consider while designing a circuit: each time the liquid pressure drops underneath the vapor pressure, liquid boiling occurs, and the final impact might be cavitation: vapor bubbles can also reduce or stop the liquid flow, in addition to damage the device.

Considering the circuit proven in the photograph


hL is the head loss among zero and 1

p0 is the strain at the water floor

pv is the vapour strain (saturation stress) for the fluid at the temperature T1 at 1

Δz is the difference in top z1 − z0 (shown as H on the diagram) from the water surface to the place 1

ρ is the fluid density

g is gravitational acceleration

Q15. When the usage of a pumping loop to mix two miscible fluids in a tank, while can the content are considered properly blended?

Ans: A rule of thumb is to show the tank over three (three) times and then sample the tank for combination residences. By "turn the tank over”, we mean to pressure the whole volume of the tank via the pump at least three times. More turnovers can be essential, however three times is a superb place to begin.

Q16. How can one estimate how the friction thing modifications in warmness exchanger tubes with a alternate in temperature?

Ans: Seider and Tate encouraged the following for determine friction factors inner warmth exchanger tubes with varying temperatures: First, determine the average, bulk imply temperature in the processing line. For example if the fluid enters the line at three hundred °C and leaves at 280 °C, use 290 °C to decide the bodily homes and friction factors. As for corrections: Laminar Flow If the liquid is cooling, the friction aspect obtained from the suggest temperature and bulk residences is divided with the aid of (bulk viscosity/wall viscosity)0.23 and for heating, it’s divided by (bulk viscosity/wall viscosity)zero.38. Here, the bulk and wall viscosity are decided on the mean temperature over the duration of the road. Turbulent Flow If the liquid is cooling, the friction component received from the mean temperature and bulk residences is split via (bulk viscosity/wall viscosity)zero.Eleven and for heating, it’s divided by way of (bulk viscosity/wall viscosity)0.17.

Q17. What is the significance of the minimum waft required by way of a pump?

Ans: The minimum flow that a pump requires describes the waft beneath which the pump will enjoy what is referred to as “shutoff”. At shutoff, most of the pump’s horsepower or paintings is converted to warmth that could vaporize the fluid and cause cavitations with the intention to seriously damage the pump. The minimal waft of a pump is especially essential within the layout of boiler feed pumps wherein the fluid is close to its boiling factor.

Q18. What is an isochoric procedure?

Ans: It is a thermodynamic system at consistent extent. Also referred to as isovolumetric manner

Q19. What is a CSTR and what are its primary assumptions?

Ans: Continuous Stirred tank Reactor. Assumptions are regular nation, regular density, constant temperature, one irreversible first-order reaction.

Q20. Should slurry pipes be sloped during horizontal runs?

Ans: If feasible, slurry lines must certainly be sloped. Generally, to slope the pipes 1/2 inches for every 10 feet of pipe is usually recommended.

Q21. List the benefits and downsides of a PFR.

Ans: Advantages: Continuous operation, high conversion charge, less price for operation. Disadvantages: temperature gradients, excessive protection cost.

Q22. What is the great way to configure a bypass line in slurry offerings?

Ans: Bypass traces have to be positioned ABOVE the control valve in order that the slurry can not settle out and increase in the line all through bypass.

Q23. Explain the functioning of a 3-way catalytic converter. 

Ans: Carbon monoxide oxidation, Nitrogen oxide discount, uncombusted hydrocarbon oxidation.

Q24. What styles of valves are encouraged for slurry services?

Ans: Typically instantly-thru diaphragm, clamp or pinch, and complete-port ball valves with hollow space fillers are the favored sort of slurry valves. In preferred, gate, needle, and globe valves are NOT encouraged for slurry services.

Q25. Explain worldwide warming from a commonplace man's and an engineer's angle.

Ans: In a not unusual man's attitude, the increase in world temperatures is international warming. In an engineer's angle, it's miles the average temperature growth within the floor temperature of the earth, specifically due to multiplied awareness of greenhouse gases. The greenhouse gases seize the heat radiated by way of the earth, in the environment, enabling the increase in temperature.

Q26. What is a great estimate for the absolute roughness for epoxy coated carbon metal pipe?

Ans: The unique roughness for welded, seamless metal is .0002 ft. PVC has a particular roughness of zero.000005 feet. You may additionally want to remember using the Hazen-Williams formula, which lists a coefficient of a hundred thirty-140 for cement-lined forged iron piping. You need to decide that is extra conservative for your utility.

The applications for epoxy-based substances are massive and consist of coatings, adhesives and composite materials which include those the usage of carbon fiber and fiberglass reinforcements (even though polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic)

Q27. What is carbon sequestration?

Ans: A method for taking pictures carbon dioxide for a long time with a purpose to reduce its consequences on international warming.

Q28. How are you able to determine the largest impeller that a pump can manage?

Ans: The motor amperage must be measured in the subject with the pump discharge valve extensive open. Subtract approximately 10% from the pumps maximum rated amperage. Then the maximum impeller  length can be determined from A2 =” A1 (d2/d1)3 A2 =” Maximum amperage minus 10% A1 =” Current operating amperage d2 =” Maximum impeller diameter d1 =” Current impeller diameter.

Q29. What are the greenhouse gases in earth's ecosystem?

Ans: Water vapor, carbon dioxide, ozone, methane, nitrous oxide and CFC.

Q30. How does a cyclone separator paintings? 

Ans: It works as gas-stable separation device the use of vortex formation.