Technical interview Questions

1. What is Definition of Distillation?

Distillation is a procedure in which 

vaporization is followed by condensation to separate out components of fluid mixture 

with help of thermal energy.

2. What is Unit operation & Unit process?

Unit Operation - 

Unit Operation is defined as operation in which mass & concentration of  component is changed from inlet to outlet with external sources

Example - Distillation Drying, Evaporation, Drying, Mixing, Crystallization, Leaching, in all this mass and concentration of components are changed but no change in  chemical

Unit Process - 

Unit Process is defined as when two chemicals proceed and formed another chemical product.

Example - Nitration, Halogenation, Hydrogenation, Amination, Sulphonation, Chlorination in which products are chemically changed

3. What are types of valves?

1. Globe valve

2. Gate valve

3. Ball valve

4. Butterfly valve

5. Diaphragm valve

6. Plug valve

7. Needle valve

8. Angle valve

9. Pinch valve

10. Slide valve

11. Flush bottom valve

12. Solenoid valve

13. Control Valve

14. Flow regulating valve

15. Back pressure regulating valve

16. Y-type valve

17. Piston valve

18. Pressure regulating valve

19. Check valve

Read in details

4. What are types of Pumps?

Classification of Pumps

Pumps are Classified in 2 categories

• Centrifugal Pump
• Positive Displacement Pump

Positive displacement pumps are further sub divided in 2 categories

• Rotary Pumps
• Reciprocating pump

Rotary pumps are further classified in following 3 categories

• Screw pump
• Gear pump
• Mono pump

Reciprocating pump is further classified in 2 categories

• Piston Pump
• Plunger pump

Piston pumps are Simplex Piston pumps & Duplex Piston Pump

Plunger Pumps are metering pump & Diaphragm pump 

Read more

5. Types of Distillation

• Flash Distillation
• Batch Distillation
• Continuous Distillation 
• Steam Distillation
• Extractive Distillation
• Azeotropic Distillation

Read in details Distillation types discussed here

6. What is LMTD ? Why we use LMTD to calculate overall heat transfer co efficient in shell & tube heat exchanger than arithmatic average?

As we seen heat transfer co efficient 

U = Qt / ( At* LMTD )

In heat exchanger hot fluid is losing heat and cold fluid is receiving heat this is not linear.

This is the reason why LMTD is used rather than Trial and error method. 

7. Which factors affecting heat transfer between fluids?

A. Types of fluid
Gas can transfer more heat comparison to liquid, and liquids can transfer more heat comparison to solid.

B. Types of material
Conductive material can easily transfer heat in comparison of resistivity material & Non metals.

C. Thickness of material
Equipment's with less thickness can easily transfer against higher thickness material.

D. Surface area
Heat transfer rate is directly proportional to surface material.
More active surface area more heat transfer.
Fourier's law
Q = - k A dt/dx

E. Liquid pressure

Liquids with high pressure can transfer more heat.
In high pressure molecules of fluid is more closer so vibration of heat can easily transfer atom to atom.

F. Turbulence of fluid
Fluid turbulence is directly proportional to turbulence of fluid.
Turbulence flow has high tendency of transfer heat than laminar flow.
This is the reason baffles are provided in heat exchanger.

G. Temperature difference between fluids.
High Temperature difference between two fluid can transfer more heat.

H. Thermal conductivity of equipment material of construction [MOC]
Each metal has unique conductivity to transfer heat. Copper has high thermal conductivity then Iron So, Copper can easily heat respect to Iron.

I. Velocity of fluids in heat exchanger
High velocity fluids prevent scaling and chocking in heat transfer equipment's so more heat transfer takes place in high velocity fluids.

J. Direction of Flow of fluids in exchange.
There are three flow patterns
Co current flow - Both fluids flowing in parallel stream
Split flow - Both fluids flow in right angle
Counter current flow - Both fluids are flowing in opposite direction

Heat transfer rate in fluids patterns
Co current flow < Split flow < Counter current flow

K. Amount of liquids

Heat exchanger gives more output when more amount of flow given.

7. What is Head & Pressure in Centrifugal pump? How to convert pressure to head?

Click here

Centrifugal Pump Head Complete understanding

8 State operational problems in distillation column

Mainly there are four problems occurring

•  Flooding
•  Weeping/Dumping
•  Entrainment
•  Foaming

In Packed bed column there are main three problems

•  Channeling
•  Loading
•  Flooding

8.1: What is flooding?

Flooding is brought about by excessive vapour flow, causing liquid to be entrained in the vapour up the column. 

The increased pressure from excessive vapour also backs up the liquid in the down comer, causing an increase in liquid holdup on the plate above.

Depending on the degree of flooding, the maximum capacity of the column may be severely reduced. 

Flooding is detected by sharp increases in column differential pressure and significant decrease in separation efficiency.

8.2: What is weeping in distillation column?

Answer: This phenomenon is caused by low vapour flow. 

The pressure exerted by the vapour is insufficient to hold up the liquid on the tray. Therefore, liquid starts to leak through perforations. 

Excessive weeping will lead to dumping. That is the liquid on all trays will crash (dump) through to the base of the column (via a domino effect) and the column will have to be re-started. 

Weeping is indicated by a sharp pressure drop in the column and reduced separation efficiency.

8.3: What is Entrainment in distillation column?

Entrainment refers to the liquid carried by vapour up to the tray above and is again caused by high vapour flow rates. 

It is detrimental because tray efficiency is reduced: lower volatile material is carried to a plate holding liquid of higher volatility. 

It could also contaminate high purity distillate. Excessive entrainment can lead to flooding.

8.4: What is Foaming in distillation column?

Foaming refers to the expansion of liquid due to passage of vapour or gas.

Although it provides high interfacial liquid-vapour contact, excessive foaming often leads to liquid buildup on trays. 

In some cases, foaming may be so bad that the foam mixes with liquid on the tray above.

Whether foaming will occur depends primarily on physical properties of the liquid mixtures, but is sometimes due to tray designs and condition. Whatever the cause, separation efficiency is always reduced.

8.4: What is channeling in distillation column?

In packed column, misdistribution is detrimental to packing efficiency and turndown. 

Misdistribution occurs at low liquid and /or vapour flow, or if the liquid feed is not distributed evenly over the packing Misdistribution delivers less liquid to some area than to others, resulting in reduced mass transfer. 

For example, the column wall directly under the distributor is poorly irrigated.

Down in the bed, the liquid tends to flow toward the wall. 

This condition is also known as channeling. At very low flow rates, there may be insufficient liquid to wet the surface of the packing.

8.5: What is loading in distillation column?

It means the actual flow quantities up and down through the equipment. 

The "loadings" are then compared with the maximum allowable quantities as determined by the physical size of the equipment as well as the operating P and T and properties of the flowing fluids.

 For example, through a section of fractionating trays, that comparison would be expressed as "percent of flood". Typical design is 80 to 85 percent of flood for a fractionator.

Q: Which valve is used for unidirectional flow?

Check Valve ensures unidirectional flow and prevents backflow automatically.

Check Valve (Non-return Valve) is used for unidirectional flow.

Key Points:

Allows flow in one direction only and automatically prevents reverse flow.

Operates without external control — opens with forward flow, closes with backflow.

Common types:

Swing Check Valve – used in large pipelines with low flow resistance.

Lift Check Valve – used for high-pressure services.

Ball Check Valve – simple design, used in slurry or viscous fluids.

Wafer Check Valve – compact and lightweight, used in limited-space installations.

Widely used in pumps, compressors, and pipeline systems to protect equipment.

9: What is pervaporation?

Pervaporation is one of the membrane separation processes which are now days for the liquid-liquid separation. 

In this process, liquid mixture is directly brought into contact with a membrane and the permeate is removed as vapour by applying Vacuum

10: What is reverse osmosis?

Reverse osmosis is a filtration process typically used for water. 

It works by using pressure to force a solution through a membrane retaining the solute on one side and allowing the pure solvent to pass to the other side.

11. What is dew point ? Why it is important in instrument air?

Dew point is a temperature beyond this there is no vapour form of fluid exists in air. When air is condensed below its dew point then all moisture present in air will be condensate and air becomes completely dry.

Instrument air used in costly instruments to operate. If we use moist air then it will harm to devices. This is the reason dew point is maintained in air around -40°C

12. What is difference between PFD and P&ID?

PFD - Process flow diagram.

PFD - Process flow diagram.

P&ID - Process and Instrument diagram.

P&ID - Process and Instrument diagram.

PFD is showing process flow diagram while P&ID is showing Valves, Pumps, Compressors and Instruments.

13. What is Floculation & Coagulation?

Floculation

• Floculation is physical operation.
• Any Fluid has solid waste particles or sludge then flocal agent convert into lump by making low to medium polymer chain and settle it down.
• Examples - METAC, Megnafloc

Coagulation

• Coagulation is chemical process.
• It is reacting with waste chemically with poly ionic materials
• Example - Aluminium sulphate, Aluminium Chloride, Hydrochloric acid, Alum,

14. What is difference between Bubble point and Boiling Point? What is Different between dew point & Freezing?

Definitions

Dew Point -

It is the temperature where first bubble of vapour formed in liquid.

When we are boiling water at 100℃ we can see vapour formed from bottom from where heat is applied. when first bubble is generated it is bubble point of water.

Boiling  Point - 

It is a temperature at which the vapour pressure of a liquid at which the vapour pressure of the liquid is equal to atmospheric pressure.

When temperature increased and at specific temperature at which Vapour generated by fluid is 1 atmospheric pressure

If we have binary fluid mixture and we are increasing temperature then Boiling point of less volatile component is change with respect to High volatile component.

When Fluid mixture initial boiling is started then less volatile fluid start vaporizing is started and in more volatile liquid its vaporize later.

Now we see Dew point & Freezing point of fluid

Dew point

Dew point of fluid is the temperature below that there is no vapour present in atmosphere

Example - Dew point of water is 16℃. There is no water vapour present below 16℃

Calculate Dew point - Calculate now

Freezing point

Freezing point of fluid is temperature at which liquid phase is completely convert into solid phase.

Freezing point of water is 0℃

15. What is relative volatility of fluids? How it impact distillation?

Answer: The relative volatility is the ratio of the K values for two components. It is denoted by ‘α’

               

                                α = k₁ /k₂

In distillation if relative volatility is high then it is easy to separate fluid mixture and few numbers of trays required but if relative volatility is near 1 then it’s difficult to distillate fluid mixture.

Relative volatility is reduced if column pressure is increased.

16. What is molecular sieve?

Molecular sieve means a solid micro porous alumina silicate with uniform pore geometry it is called as zeolite

17. What is definition of Pervaporation?

• It is membrane separation technique for liquid-liquid separation technique.
• Permeate liquid is brought in contact to vacuum and extracted as vapour

18. What is RO – Reverse Osmosis?

• Solution is subjected to Membrane.
• Membrane allow to pass solvent from one portion to another
• This is method used to separate water.

19.How to use Gate Valve, Globe Valve & Ball valve?

• Gate Valve – Fully on or off condition.
• Globe Valve – Throttling purpose design.
• Ball valve – Quick On or off valve.

20. Why cyclone separator has tangential entry?

• When laden gas enters in cyclone it forms swirl.
• This swirls separate dust and light particles.
• If there is straight entry these swirls not form and separation doesn’t takes place.
• This is the reason why tangential entry is in Cyclone separator.

Watch video in Hindi -

21. What is surging in compressors and how it can be prevented?

In centrifugal and axial compressors when the suction volume falls below a certain limit 

i.e. when the compressor is not getting enough volume of gas to compress, the gas from discharge side will flow back to the compressor( which would reduce the speed of compressor )and join together with the suction side to increase the volume input.

Thereafter the speed of compressor picks and it come to normal operation. But meanwhile such revere in flow will cross huge pressure gradient across the compressor and vibration thus may damage the impeller. 

This momentary reverse flow lapses for very short time

To prevent surging we need to install an anti-surging system. The anti-surging system shall have a mechanism to measure the suction flow and discharge flow time to time along with a control valve. 

When the suction volume falls below a certain set value a part of discharge gas will be directed towards the suction to maintain the minimum suction volume.

As normally compression leads to increase in temperature the gas recycle sis taken after the “after cooler” to ensure the discharge temperature is within control.

22. Distinguish between latent heat & sensible heat.

Latent heat

Latent heat is the enthalpy change associated with temperature change of a body along with phase change.

Sensible heat 

The enthalpy change associated with temperature change of a body in the same phase.

23. What is crystallization? Give Name of crystallizers.

Crystallization

It is the unit operation in which purification and producing  the  crystal from liquid mixture.

Name of crystallizers

• Vacuum crystallizer
• Agitated tank crystallizer
• Swenson-walker crystallizer
• Draft tube crystallizer

24. Why Earthing is provided in Solvent line?

When fluid flows, the static charge will produce. It is enough to ignite solvent.  So there is chance of explosion. To avoid this, earthing is provided in solvent line.

25. What is ISO & kaizen?

ISO

ISO (International Organization for standardization) is an international standards- setting body composed of representatives from various national standards organizations.

Kaizen

It is Japanese word that refers to activities that continuously improve all functions & involve all employees from the CEO to the assembly line workers.

26. Write the name of strong acid and strong, Give examples of weak acid and weak base.

Strong Acid

HClO4 - Perchloric Acid

HCl - Hydrochloric Acid

H2SO4- Sulfuric Acid

HNO3 - Nitric Acid

Strong Base

NaOH - Sodium Hydroxide
KOH – Potassium Hydroxide
Ca(OH)2 - Calcium Hydroxide
Ba(OH)2 – Barium Hydroxide

Weak acid

HCOOH        (formic acid)

CH3COOH (acetic acid)

HF(hydrogen fluoride)

H2S (hydrogen sulfide)

Weak Base

NH3 (ammonia)
C5H5N (pyridine)
NH4OH (ammonium hydroxide)
N(CH3)3 (Trimethyl ammonia)

27. Give Boiling Point of …

Methanol

64.7° C

Ethanol

78.3° C

Benzene

80.1° C

Toluene

110.6° C

Isopropyl alcohol

82.6 °C

Ethyl acetate

77.1° C

28. Define Write the name of one equipment use for measuring humidity.

Humidity is the amount of water vapour in the

Relative Humidity

It’s the ratio of the amount of moisture in the air to the maximum amount of moisture that could exist in the air at a specific temperature.

Specific Humidity

It’s the  ratio  of the mass of moisture  in  the mixture  to mass  of moisture in air.

Measuring equipment

Hygrometer

Hydrometer

A hydrometer is an instrument that measure the specific gravity (relative density) of liquid.

29. Differentiate compressors, fans and blowers?

• Fans, blowers and compressors are differentiated based on the method used to move the air and specific ratio (specific ratio= discharge pressure/suction pressure). 

• As per the American Society of Mechanical Engineers (ASME) the compression ratio for fans is up to 1.11, blowers‑ 1.11 to 1.2 and for compressors above 1.2

30. What is dew point and why it is important in instrument air?

The Dew Point is the temperature at which water vapor starts to condense out of the air (the temperature at which air becomes completely saturated). 

Above this temperature the moisture will stay in the air.

Electronic instruments uses instrument air received from instrument compressors must be free of any moisture. 

Small amount of moisture may condensate & it may harmful to instruments So the instrument air should be free of moisture. This is ensured by keeping the dew point below ‑400 C or below.

31.  What is pervaporation?

Pervaporation is one of the membrane separation processes which are now days for the liquid-liquid separation. 

In this process, liquid mixture is directly brought into contact with a membrane and the permeate is removed as vapour by applying Vacuum

What is definition of Pervaporation?

It is membrane separation technique for liquid-liquid separation

32.  What is reverse osmosis?

Reverse osmosis is a filtration process typically used for water.

It works by using pressure to force a solution through a membrane retaining the solute on one side and allowing the pure solvent to pass to the other side.

This is the reverse process of normal operation

33. What is dew point and why it is important in instrument air?

• The Dew Point is the temperature at which water vapor starts to condense out of the air (the temperature at which air becomes completely saturated). Above this temperature the moisture will stay in the air.

• Electronic instruments uses instrument air received from instrument compressors must be free of any moisture. Small amount of moisture may condensate & it may harmful to instruments So the instrument air should be free of moisture. This is ensured by keeping the dew point below  400 C or below. 

34. What are the color codes for cylinders of Oxygen, Carbon dioxide, and Chlorine?

Oxygen – White
Carbon dioxide – Grey
Chlorine – Yellow

35. Please give a comparison between orifice meter and venturi meter

Orifice meter

Venturi meter

1. The orifice plate can easily be changed to accommodate widely different flow rates, whereas the throat diameter of a venturi is fixed, so that its range of flow rates is circumscribed by the practical limits of Dp.

2. The orifice meter has a large permanent loss of pressure because of the presence of eddies on the downstream side of the orifice plate; the shape of the venturi meter prevents the formation of these eddies and greatly reduces the permanent loss.

3. The orifice is cheap and easy to install. The venturi meter is expensive, as it must be carefully proportioned and fabricated. Homemade orifice is often entirely satisfactory, whereas a venturi meter is practically always purchased from an instrument dealer.

4. On the other hand, the head lost in the orifice for the same conditions as in the venturi is many times greater. 

The power lost is proportionally greater, and, when an orifice is inserted in a line carrying fluid continuously over long periods of time, the cost of the power may be out of all proportion to the saving in first cost. 

Orifices are therefore best used for testing purposes or other cases where the power lost is not a factor, as in steam lines.

5. However, in spite of considerations of power loss, orifices are widely used, partly because of their greater flexibility, because installing a new orifice plate with a different opening is a simpler mater. 

The venturi meter cannot be so altered. Venturi meters are used only for permanent installations.

6. It should be noted that for a given pipe diameter and a given diameter of orifice opening or venturi throat, the reading of the venturimeter for a given velocity is to the reading of the orifice as (0.61/0.98)2, or 1:2.58.(i.e. orifice meter will show higher manometer reading for a given velocity than venturi meter).

36. Definitions: Partial pressure, Vapour pressure, Diffusivity

Partial pressure
The pressure of component gas that is present in mixture of gases.
The total pressure of mixture of gases = partial pressure of the component gas which are present in mixture of gas.

Vapour pressure
The pressure exhibited by vapour on liquid or solid surface is known as vapour pressure.

Diffusivity
The ratio of the flux to corresponding concentration gradient. Unit is m2/sec.

37. Difference : H2SO4 vs HNO3

H2SO4

H2SO4 is contain 2H+ ion. When H2SO4 dissolve in water it’s give 2H+ ion due to the ionization it’s get acidic.

38. Which gas was leak in Bhopal? Chemical structure of gas.

The name of gas methyl isocyanate (MIC)

H3C-N=C=O

39. Difference between batch process & continuous process
  

Batch process	Continuous process
Concentration of Feed is decreasing with time	Concentration of Feed is remain constant with time
Feed will not continuously charge.	Feed is continuously charge
Labor requirement is more.	From one side and come out
Time must be require.	From other side.
Generally used for small scale production.	Time is not requiring.
Manually operate.	Labor requirement comparatively less Automatically operate.

40. What is the difference between evaporation and boiling?

Evaporation happens at any temperature whereas boiling occurs only at a single temperature for a single component like water. For example the water at sea surface evaporates everyday.

It may happen either at 300C or 350C, whereas water boils only at 1000C when the vapor pressure becomes equal to atmospheric pressure.

41. What is the difference between vapor and gas?

A vapor is formed by heating any liquid and it can be condensed at atmospheric conditions either by reducing temperature or be increasing pressure.

But a gas has already above the critical temperature and can’t be condensed by application of above methods. First  it has to be brought below critical temperature. Then only it can be condensed.

42. What is wax?  What is salt?  What is osmosis process?

• Wax is form of liquid substance. it is made from long chain hydrocarbon compound.

• Salt is chemical compound which is obtained by neutralization of acidic and basic substance.

• The process by which solvent molecules of solution move from higher concentration to lower concentration through a semipermeable membrane.it is called osmosis

43. What is shear stress and shear strain?

Shear stress
shear stress is stress (external force) acting on an object or surface parallel to the slope or plane.

τ = F/A

F= force applied       
A= cross sectional area of material

Shear strain: - 

Deformation of solid due to stress.

ε = di/Io

di = change  of length        
Io = initial length

44. What is corrosion inhibitor?

A substance that decreases the rate of metal oxidation called inhibitor.

45. What is difference between mild steel and stainless steel?

The most basic difference between mild steel and stain less steel is in their composition.

• Mild Steel is made from a combination iron and carbon. It is most suitable in the construction industry and for making heavy equipment.

• Stainless steel made from a combination of chromium and iron. The resulting metal is noncorrosive and resistant to rusting.

46. Define Exothermic & Endothermic reaction.

• Exothermic reaction: - a reaction which release the heat energy.

• Endothermic reaction: - a reaction which absorb the heat energy.

47. How hard water can be softened?

• by zeolite process
• ion exchanger requires
• lime softening
• reverse osmosis
• on boiling

48. What is cloud point & pure point?

Cloud point
Cloud point refers to the temperature below which wax in diesel or biowax in biodiesels form a cloudy appearance.

Pour point
The pour point of a liquid is the temperature at which it becomes semi solid and loses its flow characteristics.

49. Define elementary reaction & non-elementary reaction.

Elementary reaction
It is chemical reaction in which one or more chemical species react directly to form of products in single step & with single transition state.

Non-elementary reaction
A reaction  that  can be broken down  into  a number  of steps. the rate of reaction will be determined only by the reactants involved in the slowest steps.

50. Define leaf filter and  plate filter.

Leaf filter

• These  filters provide large  surface  area by using varieties of filter leaves and do not require complete disassembly for cleaning  that  is  necessary  with  plate  end  frame filter press.

• The filter leaf in general consist of a heavy wire drainage screen mounted in  a tubular frame which acts as support and filtrate  conduit.  The  slurry  to be filtered  fills  the space around the leaf  by applying  pressure  on the  slurry  or vacuum  within  the  leaf.

• In either case  the  filter  cake builds  upon  the  outside  of leaf  and  filtrate  passes from  within the leaf to the filtrate discharge system.

Plate filter

• Slurry to be filtered is pumped through  the  feed  channel.  If runs  into  the chamber and fills the chamber completely the pressure goes on increase.

• The solid are deposited  on the  filter  cloth.  The  two  cake is  formed  simultaneously  in  chamber.

• The press is  then dismantled  and  the cake of solid  scrapped off from  each plate  and dropped to a conveyor or strange bin.

• Than it is washing simply and discharge the filtrate.

51. Name any four type of pipe fitting & it’s application.

Name of pipe fitting	Application
Valve	to regulate flow
Elbow	to change the direction of flow
Tee & cross	to combine or divide fluid flow
Plugs	to terminating flow
Nipple	to join two tubes
Reducers	to change the diameter of pipe (to reduce the diameter of Pipe)

52. What is the function of Manometer?

Manometers are simplest pressure measuring device. They are used for measuring Low Pressure or Pressure Difference.

53. What are inert gases? Why they are inert? Give the names of 4 inert gases.

• An inert gas is a gas which does not undergo chemical reactions under a set of given conditions.

• Inert gases are generally used to avoid unwanted chemical reactions degrading the sample. These undesirable chemical reactions are often oxidation & hydrolysis with oxygen and moisture in air.

• Examples

1. Purified ARGON
2. NITROGEN 
3. NEON
4. HELIUM
5. CO2.

54. Define : Corrosion and erosion

Corrosion
It is natural process in  which  degraded the  useful  property of material  such as strength, structure. It occurs in metal but sometimes in polymer.

Erosion
It is action of surface process that removes soil, rocks or dissolves  material from the one location to another.

55. Define : Saponification

When an oil or fat is boiled with a solution of caustic  soda, the resultant product are soap and glycerin. The chemical reaction is called saponification.

Oil + NaOH -------- > Soap + Glycerin

56. Give difference between aromatic and aliphatic hydrocarbons.

Aromatic Compound	Aliphatic Compound
They are containing aromatic ring or benzene ring.	They are organic chemical compound without benzene ring.
They are always cyclic.	They are linear and cyclic.
They are always unsaturated.	They are saturated and unsaturated.
They are conjugated due to the presence of alternating double bond.	The majority of aliphatic compound are not conjugated.

57. Write difference between Forward feed and Backward feed evaporation.

Forward Feed Evaporator	Backward Feed evaporator
Flow of solution and steam is in parallel direction.	-Flow of solution and steam is in counter current direction.
-It’s not required pump.	-It’s required pump.
-In this process heating of feed in first effect.	-In this process heating of feed in each effect.
-Maintenance cost and power cost is less.	-Maintenance charge and power cost is high.
-Get less thick liquor.	-Get thick liquor.

58. Write difference between single effect and multiple effect evaporator.

• In multiple effect evaporator vapour coming out from  1st evaporator  is  use  as feed  for 2nd While in single effect evaporator vapour coming out from evaporator  is  going to condenser and discard.

• Cost of multiple effect evaporator is higher than single effect

• Multiple effect evaporator is use in large scale

Single effect evaporator

Multiple effect evaporator

59. Name any four dryers along with one application in each

Tray Dryer

Used in dyes and pharmaceuticals

Spray Dryer

Used in detergent and food

Watch video - 

Fluidized Bed Dryer (FBD)

Used in pharmaceuticals

Fluidized Bed Dryer (FBD)

Fluidized Bed Dryer (FBD) cross section

Rotary Dryer

Used in Cement industry

Roto Cone Vacuum Dryer (RCVD)

Used in Pharmaceuticals

Roto Cone Vacuum Dryer(RCVD)

Roto Cone Vacuum Dryer(RCVD) cross section

60. Difference between drying and evaporation.

DRYING	EVAPORATION
-Small amount of solvent removed.	-Large amount of solvent removed.
-Remove solvent below boiling point.	-Remove solvent at boiling point.
-Main purpose to get dried product	-Main purpose to increasing concentration of product.

61. Write driving force in Mass transfer operation, Heat transfer operation, Momentum transfer operation.

• Mass transfer operation: – Transfer of mass from higher concentration to lower
• Heat transfer operation: – Transfer of heat from higher temperature to lower
• Momentum transfer operation: – Transfer of fluid from higher velocity to lower
• Momentum  – Mass × Velocity

62. Define Enthalpy.

Enthalpy is defined as thermodynamic state function denoted by letter “H”, that consists of internal energy system (U) plus product Pressure (P) & Volume(V) of the system.

H = U + pV

Unit - Joule, Calories

63. What is difference between Bubble point & Boiling Point? What is difference between Dew point and freezing point?

Bubble point : It is temperature at which first bubble of liquid is formed.

Boiling Point : It is a temperature of liquid at which vapour pressure of liquid is equal to atmospheric pressure [1 atm, 1.03323 Kg/cm²].

Explanation:

We have 2 chemicals mixture.

1. Less volatile chemical

2. High Volatile chemical

Volatility of fluid : Capability of liquid to convert into vaporize.

When initial phase of boiling starts less volatile chemical starts to vaporize.

At last high volatile chemical starts vaporizing.

Dew point : When any chemicals temperature is dropping, Whole vapour phase starts converting to liquid phase. At certain temperature there will no traces of chemical in vapour phase. This is dew point of Chemical.

Freezing point: When any liquid is converted into solid phase at 1 Atmospheric pressure. This temperature is Freezing point of fluid.

64. What is Avogadro number? What is its importance?

Numbers of molecules present in 1 mole.

Value : 6.023 * 10²³ / mole

65. What is Pressure test?

Pressure test is carried When any new Piping system or Pressure vessel is installed 

For Piping system it should be capable to hold double pressure then maximum operating pressure for certain time.

For vessels and reactors it should be handle up to 1.5 times of maximum pressure for certain temperature.

If piping system is designed to 10 kg/cm² then pressure test should be carried to 20 kg/cm² [Some times this is carried on 15 kg/cm² it not recommended]

Reactor and vessel designed to 10 kg/cm² then pressure test should be carried to 15 kg/cm²

66. Which gas occupied maximum percentage in air?

Nitrogen-  78%
Oxygen- 21% 

Other gases-1%

67. Which catalysts are used in Chlorination and Hydrogenation?

AlCl3, FeCl3 and ZnCl2 is used in Chlorination 

Pt, Fe and raney Ni is used in Hydrogenation

68.Define - Specific Heat. Latent heat and sensible heat

Specific Heat: The amount of heat required for rise one degree temperature per unit mass.

Latent Heat Is energy absorption or release by substance during phase change at same temperature.

Latent heat of Fusion: When energy exchange during Melting Solid of Freezing liquid.

Latent heat of Vaporization: When energy exchange during Vaporization of liquid
Latent heat of Condensation: When energy exchange during Condensate of vapour

Sensible Heat: is heat transfer of system till phase change.

69. What is Ton of refrigeration?

Ton of refrigeration (TR)

Cooling capacity of an air conditioner or refrigerator equal to 12,000 British thermal units (Btu) per hour 200 Btu per minute and denotes the amount of heat required to melt one ton of ice in 24 hours.

 1 TR = 12,000 Btu/hr

70. Pressure drop equation for horizontal pipe line in laminar flow condition?

 In fluid dynamics, the Hagen–Poiseuille equation is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. 

The assumptions of the equation are that the flow is laminar viscous and incompressible and the flow is through a constant circular cross-section that is substantially longer than its diameter.

The equation is also known as the Hagen–Poiseuille law, Poiseuille law and Poiseuille equation.

The governing equation is,

71.Define Potential flow,Ideal fluid, definition

Ideal fluid is incompressible and it is having zero viscosity. 

Flow of Ideal fluid is known as potential flow. 

Potential flow is highly developed flow.

Main characteristics of potential flow are
 No eddies, no circulations within the fluid flow. So potential flow is irrotational flow.
 No friction is developed in the fluid. Therefore there is no dissipation of mechanical energy into heat.

Therefore: Potential flow is incompressible, irrotational, highly developed and having zero viscosity.

72. Pressure drop equation for horizontal pipe line in laminar flow condition?

 In fluid dynamics, the Hagen–Poiseuille equation is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. 

The assumptions of the equation are that the flow is laminar viscous and incompressible and the flow is through a constant circular cross-section that is substantially longer than its diameter. 

The equation is als known as the Hagen–Poiseuille law, Poiseuille law and Poiseuille equation.

The governing equation is,

73. What is application of atomizer in Spray dryer?

Atomizer converts liquid in tiny droplets.

74. What are the units of Dynamic Viscosity?

Dynamic viscosity has the units of cP (Centi Poise), Poise(P) or in M.K.S units it has the units Kg/m.s.

75. What is Elutriation ?

Elutriation: It is a separation method, which depends on the settling velocity of the particles in the fluid.

In this process of separation, the material is placed in a rising fluid having a fixed upward velocity, particles whose normal falling velocity is less than the velocity of the fluid will be carried upward and out of the vessel. 

If fractions obtained from a series of fluid velocities are collected and weighed, a complete size analysis may be obtained.

76. What is jigging and where it is used ?

Jigging:

Jigging is a separation method in which the particle are separated by using the density difference between them.

Jigging is a method of gravitational preparation of natural resources, based on separation of mineral mixture on density in vertically oscillating water stream.

Usually it is used to separate metal slag form metals.

77. What is Intensive and Extensive properties?

Intensive property:

It is defined as one which doesn't depends on the quantity of matter present in the system.

Examples: 

Temperature, pressure,Molar enthalpy, molar volume

Extensive property: 

Is defined as one which depends on quantity of matter specified in the system.

Examples: 

Total mass, volume, Energy, enthalpy,

78. What are differences between pipe and tube?

Pipes and tubes are specified in terms of their diameter and wall thickness.

Pipes:

Heavy walled
Relatively large in diameter
comes in moderate lengths (20 to 40 ft)
Threading is possible
Pipe walls are rough
Lengths of pipes are joined by screwed, flanged and welded fittings
Made by welding , casting, or piercing a billet in a piercing mill
The wall thickness of the pipe is indicated using schedule number
Size of the pipe is indicated as nominal diameter

Tubes:

Thin walled
Less diameter
available in the form of coils also, several hundred meters
Can not be threaded
Tube walls are smooth
These are joined by compression fittings, flare fittings, or soldered fittings
These can be cold drawn
Tube thickness is indicated using BWG (Birmingham wire gauge)
Size of the tube is indicated as outside diameter

79. What is liquid and its properties?

Liquid is defined as a material which will take the shape of the container. It is one of the three classical states of matter.

Examples: 

water, ethanol, most of the organic solvents.

Properties:

Liquids tend to have better thermal conductivity than gases, and the ability to flow makes a liquid suitable for removing excess heat from mechanical components. 

The heat can be removed by channelling the liquid through a heat exchanger, such as a radiator, or the heat can be removed with the liquid during evaporation

Liquid is the primary component of hydraulic systems, which take advantage of Pascal's law to provide fluid power. 

Devices such as pumps and waterwheels have been used to change liquid motion into mechanical work since ancient times. 

Oils are forced through hydraulic pumps, which transmit this force to hydraulic cylinders. Hydraulics can be found in many applications, such as automotive brakes and transmissions, heavy equipment, and air-plane control systems. 

Various hydraulic presses are used extensively in repair and manufacturing, for lifting, pressing, clamping and forming

Mechanical properties:

Volume: Commonly liquids are measured in the units of volume. SI units for volume are m3.

Pressure:
Hydrostatic head is the main property of the liquid. This hydrostatic head is calculated as P= h*rho*g. h = height of the liquid column, rho = density of the liquid, g = acceleration due to gravity.

80. Convert 1 atm pressure terms to other units?

1 atm pressure 

= 760 torr

= 760 mmHg

= 101.325 kPa

=101.325 kN/m2

= 1.103 bar

= 1.103 kg/cm2

= 14.7 psi ( pressure per square inches)

81. What is chemistry?

Chemistry is the study of the composition of matter.

82. What is a chemical change?

A change, in which a new substance with different properties is formed, is known as chemical change.

83. Give example of physical change?

Dissolving sugar in water

84. What are the forms in which matter exists?

Elements Compounds and Mixture of elements and compounds.

85. What is element?

Elements are the organic materials from which all substances like solid, liquid and gas is made. It is the simplest form of matter.

86. What are the more abundant elements in the earth's crust?

O2 49.6%

Sodium 2.6%

Silicon 25.8

Aluminum 22.0

87. What are the major elements in the Human body?

Oxygen 65%

Carbon 18%

Hydrogen 10%

Nitrogen 3%

Calcium 2.4%

Phosphorus 1.0%

88. What is a compound?

Compounds are pure substances formed from the chemical reaction of elements. They have same composition and same properties, cannot be broken down except by chemical reactions.

89. What is an atom? What is it made up of?

Atoms are smallest particles of elements which can exist with the properties of the element. Different atoms of the same elements are alike in always, atoms of different elements are unlike. 

It consists of a nucleolus composed of proton and neutrons with electrons around the nucleus, protons are positively charged, electrons are negatively charged and neutrons are neutral.

90. What is Atomic number ? What is Atomic weight?

Atomic number is the number of protons in the atom of an element, which is equal to the number of electrons.

Oxygen as a standard to the weight of the atoms of elements, which are too small to be measured or to mean any thing. Oxygen is given a number 16 as it is a atomic weight. Atomic weight of all other elements is relative to this figure.

91. What is Valancy? What is the valance of carbon atom?

Valancy is combining capacity of an atom. The number of electrons, gained, lost or shared by an atom is the valance. Carbon atom has a valance of four.

92. What is Radical?

A radical is a group of atoms different elements are linked together in chemical reactions. A radical behaves like a single atom.

93. What is a molecule?

Molecules are the smallest parts of compounds, some elements like Hydrogen, Nitrogen, Oxygen, etc., exist as molecules of two atoms.

H2, N2, O2

94. What is organic compound?

Organic compounds are obtained directly or indirectly from living organisms,. Since carbon compounds are the most important compounds of plants and animals, organic chemistry is the chemistry of carbons compounds.

95. What is inorganic compound?

Inorganic means 'no life' and inorganic chemistry concerns itself with the elements and compounds other than those of carbon.

96. What is Crude oil composed of?

Crude oil is mainly a mixture of hydrocarbon compounds of carbon and hydrogen. It also contains relatively small quantities of sulfur, oxygen and nitrogen.

97. How many different types of crude are there in the world?

There are hundreds of different crude oils, perhaps even thousands. Some crude oils have lighter specific gravities than others, some have lower total sulfur content than others, some can be refined to produce more gasoline than others, and some have lower pour points than others. 

The physical properties of any specific crude oil are obtained by a series of laboratory tests which result in what is called a "crude oil assay". 

Some people classify crude oils as: paraffin base; naphthene base; aromatic base; asphalt base; or mixed base. 

The general elementary composition of crude oil falls within these approximate weight percent ranges: Carbon = 80 to 87, Hydrogen = 11 to 14, Nitrogen = 0.2, and Sulfur = 0 to 3.

98. What is the basis of classifying hydrocarbon?

On the basis of Chemical structure.

99. What the major hydrocarbon families’ deal within refinery/petrochemical processing mainly?

• PNAO
• Paraffins,
• Naphthenes,
• Aromatics and
• Olefins.

(Of these all but Olefins are found in natural crude)

100 . How we are getting petro products? What are main fractionation products from Petroleum?

The manufacture of petroleum product is the separation of crude oil into the main fractions by distillation.

Fractionation products from Petroleum

• Gas
• Naphtha (benzene)
• Kerosene (paraffin)
• Diesel
• Lubricant
• Fuel oil

101. What is a chemical reaction?

It is a chemical change in which elements combine to form compounds or breaking out compounds to recombine to form new compounds.

102. What is exothermic reaction? What is Endothermic reaction?

A chemical reaction in which heat is liberated is called exothermic reaction

Example: union fining reaction

A chemical reaction in which heat is absorbed is call endothermic reaction

Example: pacol reaction

103. What is DPK? Where Return kerosene is used?

DPK: Duel purpose kerosene. Return kerosene used as Jet A, B, JP & JPB)

104. What is paraffin?

Carbon atoms connected in a straight chain by single bond (normal) Butane C-C-C-C

105. What are iso paraffins?

Carbon atoms having branched chain, single bond arrangement is called Iso-parafins (non-normals).

Iso-butane C- C - C

|

C

106. Why kerosene selected for Normal Paraffin production?

Normal paraffin is rich in kerosene carbon range, almost about 18.5% with C10-13 range. Average Molecular Weight of heart cut is about 165.

107. What are the characteristics of straight chain paraffins?

• Saturated compounds with a general formula CnH2n+2 Good natural stability. 
• Natural high Viscosity Index (V.I) lubricating oils. 
• Good source of waxes.
• Poor for manufacture of Gasoline.
• Hard carbon deposits.
• High pour point
• Found particularly in paraffin crude.

108. What changes in properties occur when paraffin are isomerizes?

• Boiling point is lowered.
• Octane number is increased.

109. What are the properties of Naphthenic hydrocarbons?

• They are cyclo paraffin
• They are saturated with a genera formula CnH2n+2
• Low VI
• Low pour point
• Better octane rating than corresponding paraffin.
• Naphthenic Motor oils form sort, fluffy carbon deposits.

110. What are the properties of olefins?

• They are unsaturated.
• Readily react with oxygen to form sludge.
• Possess good anti-knock properties.

111. What are the properties of Aromatics?

• They are not very reactive in spite of the presence of double bonds.
• They behave more like saturated compounds.
• Excellent anti-knock properties.
• Used as commercial solvents due to their high solvent power.
• Poor VI components.
• Produces smoky flames

112. What is cracking?

Heavier hydro carbons are cracked or broken into smaller molecules to produce more valuable lighter products from the low priced heavier hydrocarbons.

113. What is Alkylation?

It is the process of combing two dissimilar hydrocarbons. A catalyst is used in this reaction of saturated compounds with unsaturated.

114. What is Polymerization?

Similar to Alkylation, except that in this case two un saturates are combined over a catalyst.

115. What is Hydrogenation or Hydro finishing reaction?

In this reaction hydrogen combines with unsaturated hydrocarbon make them a saturated compound over a catalyst.

116. What is Hydro De-sulfurization?

A reaction over a catalyst to remove sulfur by converting it to H2S with addition of hydrogen.

117. What is the reaction involved in decoking of furnace & regeneration of catalyst?

It is Oxidation. Using oxygen from the air the coke is burnt to CO2.

118. What is temperature? What is freezing point? What is the freezing point of kerosene?

It is a measure of how hot something is.

The temperature at which crystals first appear when a liquid is cooled under specified conditions.

Kerosene freezing point -47oC.

119. What is Dew point?

The temp at which condensation of water vapor from the air begin the temp of the air water vapor mixture falls.

120. What is Dry bulb temperature? What is Wet bulb temperature?

It is an indication of the sensible heat content of air water vapor mixtures

It is measure of total heat content or enthalpy. It is the temperature approached by the dry bulb and the dew point as saturation occurs.

121. What is Dew point temperature?

It is a measure of the latent heat content of air-water vapor mixtures and since latent heat is a function of moisture content, the dew point temperature is determines by the moisture content.

122. Write difference between density and Specific gravity?

Fuel density: mass of the fuel to the volume at specified temperature.

Specific gravity of fuel: density of fuel, relative to water is called specific gravity. Higher the sp gravity, higher will the heating values.

123. What is Calorific value (CV)?

Energy content in an organic matter (CV) can be measured by burning it and measuring the heat released. The heating value of fuel is the measure of the heat released during the complete combustion of unit weight of fuel. 

It is expressed as Gross Calorific Value (GCV) or Net Calorific Value (NCV).

124. What is the difference between GCV and NCV?

The difference between GCV and NCV is the heat of vaporization of the moisture and atomic hydrogen (conversion to water vapor) in the fuel. 

Typical GCV and NCV for heavy fuel oil are 10500 kcal/kg and 9800 kcal/kg.

125. How does define a "barrel"? How many liters and Gallons in a US barrel of crude oil?

The "barrel" is a volumetric unit.

1 barrel is equivalent to 42 U.S. gallons or 34.97 Imperial gallons or

158.99 liters or 5.615 Cubic feet.

How many liters and Gallons in a US barrel of crude oil?

159 Liters, 42 Gallons

126. What is specific gravity?

Specific gravity is used to measure liquid density

127. What is the relation between Sp. Gravity and API gravity?

Heavier hydrocarbons will have higher specific gravity and low API gravity.

128. How do you calculate API Gravity?

129. How do you convert Sp. Gravity (0.8020) to API gravity?

130. How do you calculate Sp.gravity of a crude oil at a given API 45?

141.5/131.5 + 45 = 0.8017

131. Why do we treat lowers API gravity crude to meet product specification?

Lower API crude requires high temperature and longer retention time to meet proper oil product specification.

132. What is heat?

It is an energy associated with the motion of molecules in a substance.

133. What is the basic principle of heat transfer?

Heat transfer is the transfer of heat from hot place to cold place.

134. What is the effect of boiling point in relation with pressure?

Boiling point increases at high pressure and decreases at low pressure.

135. What happens to vapor pressure when it reaches to boiling point?

At boiling point vapor pressure of a liquid equalizes to the pressure of the surrounding atmosphere.

136. What is the purpose of a hazardous area classification drawing? Give examples of Zone 0, Zone 1 and Zone 2

Hazardous areas are classified as

• Zone 0 (Class 0)
• Zone 1 (Class 1)
• Zone 2 (Class 2)

Examples of Zone 0, Zone 1 and Zone 2

Zone 0 = Always air fuel mixture is continuously present.

Example: Tank vents, Sump vents, Drains etc.

Zone 1 = Air fuel mixture is present during normal operations.

Example: Pipe line flanges, Inlet manifold areas. (Flange joints are the weaker areas in a process system that may cause leak during abnormal Operation).

Zone 2 = Air fuel mixture is may present during abnormal operations.

Example: Welded pipelines where there are no flange joints. This area reduces the chances of leaks. Flare lines, welded hydrocarbon pipelines where there are no flanges.

137. What is a natural gas?

Natural gas is produced from organic compounds or hydrocarbons during the process of crude oil / gas production operations from an oil reservoir.

138. Why do we consider methane is the lightest gas?

Methane has only one carbon atom.

139. What is viscosity?

Viscosity is the resistance of a liquid to flow.

140. What is pressure? How do you calculate pressure of 100 pound block measuring 25 Square inches on each side?

Pressure is the measure of force applied to a unit area. 

Pressure = Force/Area

100/25 = 4 psi.

141. Why do we use vacuum scale?

Vacuum scale is used to measure pressure in vessels which are below atmospheric (Absolute).

142. What reading on a mercury vacuum gauge corresponds with the Atmospheric pressure?

Zero in Vacuum gauge is equal to the atmospheric pressure.

143. What is a perfect vacuum?

Zero pressure absolute Psia equals the pressure in a perfect vacuum.

144. What is RTD?

RTD is resistance Temperature Detector. (Heat creates by Electrical Resistance). Increase the heat means increases the resistance.

145. What is the unit of electrical resistance?

Unit of electrical resistance is Ohms at 0 oC .

146. Expand the P&ID abbreviations?

• FSH Flow switch high,
• FR Flow recorder
• FRC Flow recorder Controller
• FIC Flow indicating Controller
• PR Pressure recorder
• PRV Pressure Relief Valve
• TSV Temperature safety valve
• ESD Emergency Shut Down
• PDIC Pressure differential indicating controller
• PCV Pressure control valve
• FCV Flow control valve
• TCV Temperature control valve
• LCV Level control valve
• PSHH Pressure switch high high
• FSHH Flow switch high high
• TSHH Temp. Switch high high
• PSLL Pressure switch low low
• LO Lock open
• LC Lock closed
• TIC Temperature indicating controller
• CSO Car Seal Open (valve sealed and kept in OPEN position)
• CSC Car Seal Closed (valve sealed and kept in CLOSED condition)

147. Find the following from P&ID?

• Pipe line specifications
• Fail open valves
• Fail closed valves
• Restricted orifice plates
• Lock open valve
• Lock closed valves
• Piping insulation
• Pneumatic inst. Signal lines
• Level controller
• Level relay switch
• Pressure control valves
• Reducers
• Shutdown valves
• Spectacle blinds
• Reciprocating pump
• Pulsation damper

148. What is a mixture? Give two examples.

Mixture is a composition of two or more molecules of an element that are not chemically bonded and can be physically separated.

149. What happens to the volume of gas from one stage to the next stage?

Volume reduces when compressed gas move out from one stage to the next stage.

150. At what temperature the movement of molecules completely stops?

At absolute zero temperature.

151. What is difference between deposition and sublimation?

What is difference between melting and freezing?

What is difference between vaporization and condescension?

Overall conversion

Solid into liquid called Melting.

Liquid into solid called freezing.

Liquid into gas called vaporization.

Gas into liquid called condensation.

Gas into solid called deposition.

Solid into gas called sublimation.

152. How much power required for agitation?

It is a function of RPM.

It is also depends on 

• Viscosity of fluid
• Density of fluid.
• Dimensions of vessels and Impeller

It is related by dimensionless form as:

Where

P=power required for agitation

n = rotational speed of impeller

Da= diameter of impeller

९= density of fluid

μ=viscosity of fluid

For baffled vessels, Power number (Np) does not depend on the value of Froude number (Nfr). and it is only a function of Reynolds number (NRe).

Empirical correlations and charts are available with the dimensional groups to get Np. from which power required for agitation is calculated. This required power is supplied by means of electrical drive / gearbox assembly and transmitted to the vessels by the impeller attached with the shaft coupled to the drive.

The mechanical design of agiated vessel is calculated as per pressure vessel design codes such as ASME Section VIII Division 1 or IS 2825.

153. Difference between Absorption and Adsorption

In absorption, one substance (matter or energy) is taken into another substance. But in adsorption only the surface level interactions are taking place.

154. Difference between Liquid and Aqueous solution.

• Liquid is a state of matter, while aqueous is a special type of liquid formed by dissolving a compound in water

• All aqueous solutions are liquids, but not all liquids are aqueous solutions

155. State Laws of conservation of energy? 

According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”

156. Define Reynolds number.

Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless number. It determines the type of fluid flow.

157. What is a Newtonian fluid?

A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

158. Difference between Strainer and Filter

Strainer for coarse size, Filter is more accurate than Strainer.

159. What are differences between Welding & Brazing?

In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together.

In Brazing involves significantly lower temperatures and does not entail the melting of base metals. 

Instead, a filler metal is melted and forced to flow into the joint through capillary action.

160. What is the difference between Blower and Fan?

Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.

When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.

161. Is gate valve used for Throttling?

Gate valves are not suitable for throttling because the control of flow is difficult for the valve’s design, and the flow of fluid slapping against a partially open gate can cause extensive damage to the valve.

162. Why is the Suction pipe of Vapour Compression Refrigeration system insulated?

1. It prevents the suction line from sweating and dripping water inside the house.

2. The insulation also prevents the suction line attracting heat from the outdoors on its way to the condenser coil.

163. What is molecular sieve?

Answer: Molecular sieve means a solid micro porous alumina silicate with uniform pore geometry it is called as zeolite

165. What are the various graphical methods for the calculation of number of plates in distillation column?

There are three methods

• Mccabe thiele method
• Ponchon sevrit method
•  Lewis sorel method

166. What is normal tray spacing (Distance between two plates) in distillation column?

As per thumb rule. Normal tray spacing is 2 ft. or 0.6m. Height should not exceed 30m. 

Hence maximum numbers of try is about 50 trays due to fabrication limit diameter of column should be less than 7m and height less than 35meter.

167. What are the different types of tray efficiencies?

Answer:

There are three types of tray efficiencies

•  Local or point efficiencies
•   Murphee plate efficiencies
•   Overall efficiency

In most of cases overall plate efficiencies is used which is founded by

Overall plate efficiency = No of ideal trays required / No of actual trays required

168. Distinguish between liquid-liquid extraction and leaching?

Answer: In liquid-liquid extraction solvent is used as solvent to separate liquids and in leaching (also known as solid-liquid extraction) solute is using to separate like separate oil from oil cake using hexane.

169. What is Gauge pressure?

Gauge pressure, also called overpressure, is the pressure of a system above atmospheric pressure.

Gauge pressure is zero-referenced against atmospheric air pressure, so gauge pressure readings include the pressure from the weight of the atmosphere. 

What this means is that gauge pressure varies according to height above sea level as well as to weather conditions. 

170. What is atmospheric pressure?

The atmosphere of the Earth has weight and creates pressure. Also called barometric pressure or ambient pressure, atmospheric pressure is subject to weather-dependent fluctuations. 

171. What is the relationship between gauge pressure and absolute pressure?

A pressure measurement based on a reference pressure of zero, or no pressure at all, is known as absolute pressure. 

172. What is the relationship between gauge pressure and absolute pressure?

Zero pressure exists only in a perfect vacuum, and outer space is the only place where this occurs naturally. 

Therefore, an absolute-pressure reading is equal to atmospheric (ambient) pressure plus gauge pressure. That means gauge pressure is equal to absolute pressure minus atmospheric (ambient) pressure. When the absolute pressure is greater than the atmospheric pressure, the condition is called positive overpressure; when the absolute pressure is less than the atmospheric pressure, it is referred to as negative overpressure.

173. Various thermodynamic cycles.

Thermodynamic cycles are processes that involve the transfer of heat and work between a system and its surroundings.

Carnot cycle is a theoretical cycle that is the most efficient possible engine cycle

Rankine cycle is used in steam power plants

Brayton cycle is used in gas turbines

Otto cycle is used in spark-ignition engines

Diesel cycle is used in compression-ignition engines

174. How to calculate cooling tower capacity?

Cooling tower capacity is the heat removed from the circulating water. The basic heat-balance formula is:

Q = ṁ × Cp × ΔT

where

Q = heat removed (kW or BTU/hr)

ṁ = mass flow rate of water (kg/s)

Cp = specific heat of water ≈ 4.186 kJ/kg·K

ΔT = temperature drop (hot water in − cold water out) in °C (or °F if using imperial formulas)

You then convert Q to the unit you want (kW, BTU/hr, or Tons of Refrigeration).

Common unit formulas (easy to use)

Metric (m³/h or L/s, ΔT in °C):

Q (kW) = 1.163 × flow (m³/h) × ΔT (°C)

(since 1.163 = 4.186/3.6)

or Q (kW) = 4.186 × flow (L/s) × ΔT (°C)

Convert to tons of refrigeration (TR):

TR = Q (kW) / 3.517 (1 TR = 3.517 kW)

Imperial (GPM, ΔT in °F):

Q (BTU/hr) = 500 × GPM × ΔT (°F) (approximation: 1 GPM × 1°F ≈ 500 BTU/hr)

TR = Q (BTU/hr) / 12,000 = (GPM × ΔT) / 24

175. What are important cooling-tower terms?

Range = Hot water temp in − Cold water temp out (ΔT used above)

Approach = Cold water temp out − Ambient wet-bulb temperature (how close tower can get to wet bulb)

Design wet-bulb = wet-bulb temp used for selection (affects achievable cold water temp)

Safety factor — include 5–15% extra capacity for fouling, future loads, seasonal variation

176. What are cooling tower selection steps (short description)?

1. Calculate process heat load Q using one of the formulas above.

2. Convert Q to the vendor’s unit (kW or TR).

3. Decide design wet-bulb and required cold-water temperature (check approach).

4. From tower manufacturer curve pick a tower that meets Q at chosen wet-bulb and desired approach.

5. Add safety margin (5–15%) and check for flow balancing, pump head, and water treatment needs.

177. What is anti sihon valve?

An anti-siphon valve is a safety device designed to prevent contaminated water or fluids from flowing backward into clean supply lines due to siphoning effects. 

It is commonly used in plumbing, irrigation, and fuel systems, combining a control valve and atmospheric backflow preventer. 

By allowing water to flow only in one direction, it protects drinking water from potential pollutants, especially in residential irrigation and fuel storage systems. 

Proper installation above ground is crucial for its effectiveness.

178. How can give earthing in PTFE pipe lines?

Earthing in PTFE pipe lines is essential to safely discharge static electricity. 

The recommended methods are:

Use earth studs or lugs welded to the steel part of the PTFE-lined pipe, then connect them with bonding wires to ground.

Install star washers or Spikey earth continuity washers at pipe joints to maintain electrical continuity across flanges.

Use antistatic PTFE (with carbon added) for the liner, but always ensure the steel housing is earthed too.

Regularly check earth continuity; the resistance to ground must be less than 10 Ω

179. What is the difference between purity and assay?

Purity measures the degree to which a substance is free from impurities or contaminants, usually expressed as a percentage. 

Assay, on the other hand, is a quantitative analysis that determines the actual amount or concentration of the main component, like the active ingredient in a drug.

In short, purity answers “How clean is it?” while assay answers “How much of the main component is present?” 

Both are crucial in quality control, but serve different analytical purposes

180. How does a water ring vacuum pump work?

It uses a rotating water ring to create suction and discharge, producing vacuum efficiently.

A water ring vacuum pump is a rotary positive displacement pump used to create vacuum.

Construction: It has an impeller mounted eccentrically inside a casing, partially filled with sealing liquid (usually water).

Working principle:

When the impeller rotates, the water forms a rotating ring along the casing due to centrifugal force.

The eccentric position creates variable spaces between impeller blades and water ring.

As blades rotate, these spaces expand (suction phase) drawing in gas, and then compress (discharge phase) expelling gas out.

Applications: Widely used in chemical, pharma, and power industries for vacuum generation.

181. What are the advantages and limitations of a water ring vacuum pump?

Advantages:

Simple and robust design with easy maintenance.

Can handle wet, dirty, or saturated gases/vapors without damage.

Provides steady, pulse-free vacuum.

Operates safely in explosive or hazardous environments (no metal-to-metal contact).

Cooling effect of water reduces gas temperature during compression.

Limitations:

Vacuum level limited to ~25–30 mmHg absolute (not very deep).

Requires continuous supply of sealing liquid (usually water).

Efficiency decreases with temperature rise of sealing liquid.

Higher power consumption compared to dry pumps.

Corrosion possible if aggressive gases or poor-quality sealing water is used

182. What is a barometric leg?

Definition:

A barometric leg is a long vertical pipe (≈10–12 meters) used to discharge liquid from equipment operating under vacuum.

Working Principle:

The liquid column in the leg creates a hydrostatic seal.

This prevents air from entering the vacuum system while allowing continuous liquid discharge.

Typical Application:

Common in barometric condensers and other vacuum systems.

Handles hot condensate and non-condensables without using a pump.

Key Requirement:

Length of the leg must be greater than the height of a water column equal to atmospheric pressure (~10.3 m).

183. Can you give a real-life example of a barometric leg?

Power Plants:

In steam surface condensers or barometric condensers, cooling water and condensed steam are discharged through a barometric leg.

The leg ensures continuous removal of condensate without breaking the vacuum.

Evaporators (Chemical):

In multi-effect evaporators under vacuum, barometric legs help remove concentrated liquid products.

They avoid the need for pumps at high temperature (reducing cavitation risk).

Key Benefit in Practice:

Simple, no moving parts, reliable for handling hot condensate.

Saves on vacuum pump load since air leakage is minimized.

184. How to provide earthing in Glass Lined Reactors (GLR)?

Earthing in GLR is done by external lugs for the steel shell and special conductive earthing devices inside to safely discharge static charges from the reactor contents.

Purpose of Earthing:

To safely discharge static charges generated during mixing, charging, or solvent handling.

Prevents sparking and ensures safe operation in flammable environments.

Methods of Providing Earthing:

1. External Earthing Lug:

A metallic lug welded on the reactor’s steel shell is connected to the plant’s earthing system.

Ensures the outer body is grounded.

2. Internal Earthing Device (Special Design):

Since glass is non-conductive, special conductive devices (like platinum-tipped earthing rods) are installed inside.

These pass through the glass lining and connect liquid contents to ground.

3. Static Dissipation Paths:

Earthing of agitator shaft, nozzles, manways, and accessories with conductive paths.

Use of antistatic PTFE liners or conductive gaskets if required.

185. What are precautions to be taken in earthing?

Earthing must be checked periodically for continuity.

Multiple earth connections are recommended for redundancy.

Avoid damaging the glass lining during installation.

186. Why is earthing extra critical in Glass Lined Reactors (GLRs)?

Earthing in GLRs is critical because glass is insulating and the reactor is often used with flammable solvents—making static electricity a major ignition source if not safely discharged.

Non-conductive Glass Lining:

Glass does not conduct electricity → static charges can accumulate on liquid or vapor inside.

Flammable Solvents:

GLRs are widely used in pharma/chemical industries with solvents (ethanol, acetone, toluene, etc.) that are highly flammable.

Even a small static discharge can cause fire/explosion.

Agitation Effect:

Mixing and pumping increase static charge build-up in the contents.

Without proper earthing, risk of sparking is high.

Powder Charging:

When powders are charged into GLR, triboelectric charging happens → more static risk.

Operator & Equipment Safety:

Prevents hazards to operators and protects expensive glass lining from thermal/mechanical shock due to ignition accidents.

187. What is steam economy and efficiency?

Steam economy = Output (water evaporated) per unit steam input.

Steam efficiency = Effectiveness of steam energy usage.

Steam Economy:

Defined as kg of water evaporated per kg of steam used.

Commonly used in evaporators and boilers.

Formula:

Steam Efficiency

Steam Efficiency:

Measures how effectively heat energy of steam is converted to useful work/evaporation.

Formula (general):

188. What is the formula for calculating volume of a tank?

Tank volume is calculated using geometry formulas of its shape (rectangular, cylindrical, or spherical).

Depends on tank shape:

Rectangular tank:

(Length × Breadth × Height)

Cylindrical tank:

(π × radius² × Height)

Spherical tank:

(4/3 × π × radius³)

Horizontal cylindrical tank (partially filled):

Requires segment area formula based on liquid height.

Units: Convert results into liters, m³, or gallons as per requirement.

189. How does an ejector create vacuum?

Ejector creates vacuum by using a high-pressure jet to generate a low-pressure zone, which pulls gases/vapors from the system.

Uses high-pressure motive fluid (steam, air, or water).

Fluid passes through a converging-diverging nozzle, converting pressure energy into high velocity jet.

The jet creates a low-pressure zone at the nozzle outlet.

This sucks in gases/vapors from the system (vacuum creation).

The entrained gases mix with the motive fluid.

Mixture slows down in a diffuser, converting velocity back into pressure for discharge.

Q: How do you decide the temperature for any process?

Temperature is decided based on the process requirements to achieve the desired reaction rate, product quality, and efficiency.

It is determined by studying the material properties (e.g., boiling point, melting point, stability, etc.).

Consider the kinetics and thermodynamics of the process — the optimum temperature should maximize yield without degrading the product.

Equipment capability and design limits are checked to ensure safe operation.

Follow process validation data, SOPs, and manufacturer’s recommendations for accurate temperature selection.

Safety and energy efficiency are also evaluated to prevent hazards and reduce operational costs.

Temperature is usually optimized through trials, past data, or scale-up studies before finalizing for routine use.

Q: What are the types of coupling?

Coupling is a mechanical device used to connect two shafts together at their ends to transmit power, torque, and motion.

Coupling selection depends on alignment, torque, speed, vibration, and operational conditions.

It also helps in absorbing misalignment, vibration damping, and shock load reduction.

Main types of coupling:

1. Rigid Coupling – Used when shafts are perfectly aligned.

Examples: Sleeve coupling, Clamp coupling, Flange coupling.

2. Flexible Coupling – Allows slight misalignment and absorbs shocks.

Examples: Bushed pin-type, Oldham, Universal (Hooke’s joint).

3. Fluid Coupling – Uses hydraulic fluid to transmit power smoothly, often in heavy machinery.

4. Gear Coupling – Uses gear teeth for high torque transmission and slight misalignment compensation.

5. Disc or Diaphragm Coupling – Thin flexible discs handle misalignment and high-speed applications.

Q: What is the composition of natural gas?

Natural gas is mainly methane, with small amounts of other hydrocarbons and impurities, making it a highly efficient and cleaner-burning fuel.

Natural gas is a fossil fuel mixture of light hydrocarbons found underground, mainly used as a clean energy source for power, heating, and industrial processes.

Its composition varies slightly depending on the source, but it is primarily made up of the following:

Typical composition:

Methane (CH₄): ~70–90% – Main component and primary energy source.

Ethane (C₂H₆): ~5–15% – Used as petrochemical feedstock.

Propane (C₃H₈) & Butane (C₄H₁₀): ~1–10% – Used as LPG components.

Carbon Dioxide (CO₂): ~0–8% – Non-combustible impurity.

Nitrogen (N₂): ~0–5% – Inert gas.

Hydrogen Sulfide (H₂S): Trace – Removed during processing (toxic).

Other gases (e.g., Helium, Hydrogen): Trace – Occur in small quantities.

Q: Which tools are used for a company energy audit?

Energy audit tools measure and analyze energy use, guiding companies toward efficiency improvements and cost savings.

Definition: Energy audit tools are instruments used to measure, monitor, and analyze energy consumption in different systems to identify saving opportunities.

Common Tools Used:

Power Analyzer / Energy Meter: Measures voltage, current, power factor, and total energy consumption.

Infrared Thermometer / Thermal Imaging Camera: Detects heat losses, insulation faults, and hot spots.

Anemometer / Air Flow Meter: Measures air velocity and flow in HVAC and ventilation systems.

Lux Meter: Checks lighting levels to optimize lighting efficiency.

Combustion Analyzer: Analyzes flue gases to assess boiler and furnace efficiency.

Ultrasonic Flow Meter: Measures liquid and steam flow without cutting the pipeline.

Data Logger: Continuously records energy parameters over time for trend analysis.

Purpose: These tools help identify energy wastage, optimize equipment performance, and reduce operating costs.

Q: What precautions are needed while handling solvents?

Always prioritize personal protection, ventilation, fire safety, proper storage, and safe disposal when handling solvents.

Use Proper PPE: Always wear gloves, safety goggles, face shield, apron, and safety shoes to prevent skin and eye contact.

Ensure Good Ventilation: Work in a well-ventilated area or fume hood to avoid inhalation of harmful vapors.

Avoid Ignition Sources: Keep solvents away from sparks, flames, and hot surfaces as many are flammable.

Label and Store Properly: Store solvents in approved, clearly labeled containers and in cool, dry, well-ventilated areas.

Use Grounding and Bonding: Prevent static charge buildup while transferring flammable solvents.

Avoid Direct Contact: Never touch solvents directly; use tools or dispensers.

Handle Spills Immediately: In case of a spill, ventilate the area and follow spill cleanup procedures promptly.

Dispose Safely: Follow environmental and company guidelines for solvent waste disposal.

Q: Why is pH scale from 0 to 14 and not more than 14?

The pH scale is 0–14 because it’s based on the ionization constant of water, where at 25 °C. This defines the natural limits for acidic and basic strength in water-based systems.

Definition: pH is the negative logarithm of hydrogen ion concentration in a solution:

Reason 1 – Based on Water Ionization:

The pH scale is derived from the auto-ionization of water:

Maximum [H+] ≈ 1 mol/L → pH = 0

Minimum [H+]≈ 10^{-14} mol/L → pH = 14

Reason 2 – Neutral Point at 7:

When , pH = 7, which is neutral.

Below 7 = acidic, above 7 = basic.

Reason 3 – Water-based Limitation:

The 0–14 range is valid for aqueous solutions at 25 °C.

In extremely concentrated or non-aqueous solutions, pH can be <0 or >14, but that’s rare and not typical in standard chemistry.

Q: What is Inert Gas?

Inert gases are crucial where chemical stability and safety are required in industrial and laboratory applications.

Definition: 

Inert gas is a gas that does not readily react chemically with other substances under normal conditions.

Reason for Inactivity: 

It has a complete outer electron shell, making it chemically stable and unreactive.

Examples: 

Noble gases like helium, neon, argon, krypton, xenon, and some industrial gases like nitrogen (in many conditions).

Purpose/Use:

Used to create a non-reactive atmosphere in processes such as welding, chemical reactions, metallurgy, and food packaging.

Helps in preventing oxidation, explosions, or unwanted chemical reactions.

Q: What are types of steam and its applications?

Selection of steam type depends on process requirements — heating needs, energy efficiency, equipment design, and product quality considerations.

Types of Steam and Their Applications – Interview Answer:

1. Saturated Steam:

Definition: Steam in equilibrium with water at the same temperature and pressure (contains no water droplets).

Application: Widely used for heating, sterilization, cooking, and industrial process heating due to its high heat transfer efficiency.

2. Wet Steam:

Definition: Steam containing moisture or water droplets mixed with vapor.

Application: Used in processes where condensate is acceptable or can be separated, like some heating systems or turbines with moisture separators.

3. Dry Saturated Steam:

Definition: Steam that is fully vaporized with no water content, just at the boiling point.

Application: Ideal for precise heating, sterilization, drying, and power generation where moisture must be avoided.

4. Superheated Steam:

Definition: Steam heated beyond its saturation temperature at a given pressure, with no moisture and higher energy content.

Application: Commonly used in turbines, power plants, and mechanical drives where expansion and high energy output are needed.

5. Flash Steam:

Definition: Steam produced when hot condensate is depressurized and part of it evaporates.

Application: Utilized in heat recovery systems to improve energy efficiency.

Q: What are the types of dryers used in industries?

Dryers are used in industries to remove moisture from solids, liquids, or gases to achieve the desired dryness level for further processing or storage. The main types are:

1. Tray Dryer

Batch type dryer with multiple trays.

Hot air circulated by fans for uniform drying.

Used for pharmaceuticals, food, and chemicals.

2. Fluidized Bed Dryer (FBD)

Hot air fluidizes the solid particles for fast and uniform drying.

High drying efficiency and reduced drying time.

Commonly used in pharma granules and powders.

3. Spray Dryer

Converts liquid or slurry into dry powder by spraying into hot air.

Provides fine, uniform powder with controlled particle size.

Used in milk powder, enzymes, and chemical industries.

4. Rotary Dryer

Continuous cylindrical drum that rotates while hot air passes through.

Suitable for large-scale drying of bulk solids.

Used in minerals, fertilizers, and biomass industries.

5. Drum Dryer

Rotating heated drum dries a thin film of liquid or slurry.

Quick drying and continuous operation.

Used for pastes, slurries, and food products.

6. Vacuum Dryer

Drying under reduced pressure to lower boiling point.

Ideal for heat-sensitive or solvent-rich materials.

Common in pharmaceuticals and fine chemicals.

7. Freeze Dryer (Lyophilizer)

Removes moisture by sublimation under vacuum.

Preserves structure and quality of sensitive products.

Used in biotech, pharmaceuticals, and food.

8. Belt / Conveyor Dryer

Material moves on a belt through zones of controlled temperature.

Suitable for continuous drying of granules, pellets, or sheets.

Used in food, chemical, and textile industries.

Q: How many types of steam traps are used in industries?

There are three types — Thermodynamic, Mechanical, and Thermostatic — are selected based on pressure, load, and process requirements to ensure efficient steam and condensate management.

Steam traps are mainly three types, based on their working principle:

1. Thermodynamic Steam Trap:

Works on the difference in dynamic properties of steam and condensate.

Simple, compact, and suitable for high-pressure and superheated steam.

Common type: Disc trap.

2. Mechanical Steam Trap:

Operates based on the density difference between steam and condensate.

Types include float type and inverted bucket type.

Ideal for continuous condensate discharge and process heating applications.

3. Thermostatic Steam Trap:

Works on the temperature difference between steam and condensate.

Uses bimetallic or bellows element to open or close the valve.

Suitable for start-up applications and tracing lines.

Q: What is the maximum vacuum that can be achieved by a vacuum pump (in mmWC)?

In industrial practice, the maximum achievable vacuum is around 10,300–10,332 mmWC, which corresponds to near absolute vacuum (99.9%), depending on the pump type and system condition.

The maximum vacuum depends on the type and design of the vacuum pump.

Vacuum is often expressed as mmWC (millimeters of water column) — where 1 atmosphere ≈ 10,332 mmWC.

Typical ranges by pump type:

1. Liquid Ring Vacuum Pump:

Achieves up to 9,700–10,000 mmWC vacuum (≈ 97–98% vacuum).

Commonly used in pharma, chemical, and process industries.

2. Rotary Vane Pump (Mechanical):

Achieves up to 10,200–10,300 mmWC vacuum (≈ 99% vacuum).

Suitable for dry and clean gas applications.

3. Roots + Rotary Combination:

Can reach 10,320 mmWC or more (≈ 99.9% vacuum).

Used for high vacuum and critical applications.

Q: What is the meaning of Azeotrope?

An azeotrope is a mixture of two or more liquids that boils at a constant temperature and retains the same composition in both liquid and vapor phases during boiling.

It behaves like a single pure substance, making separation by simple distillation impossible.

Formed due to specific intermolecular interactions between the components.

There are two main types:

1. Minimum Boiling Azeotrope: 

Boils at a lower temperature than either component (e.g., Ethanol–Water).

2. Maximum Boiling Azeotrope: 

Boils at a higher temperature than either component (e.g., Hydrochloric acid–Water).

Special separation methods like azeotropic distillation, extractive distillation, or pressure-swing distillation are used to break them.

Q: How can you do Material Balance?

Answer:

✅ 1. Definition:

Material Balance (or Mass Balance) is the process of accounting for all input, output, accumulation, and loss of materials in a system to ensure mass conservation.

✅ 2. Basic Principle:

> Input = Output + Accumulation + Loss

(For steady-state: Input = Output)

3. Steps to Perform Material Balance:

1. Define the system boundary – select process unit or plant section.

2. Collect process data – flow rates, compositions, densities, etc.

3. Draw a flow diagram – mark all inlets and outlets.

4. Write material balance equations for total and individual components.

5. Apply conservation of mass – no material is lost or created.

6. Solve equations to find unknown flows or compositions.

7. Verify the balance with actual plant data (error < 5% acceptable).

4. Types of Material Balance:

Total mass balance (overall flow).

Component balance (for each chemical species).

Steady-state or unsteady-state depending on process condition.

5. Importance:

Ensures process efficiency and yield optimization.

Helps in design, troubleshooting, and cost control.

Essential for energy balance and environmental compliance.

Q: What is the difference between a Fan, Blower, and Compressor?

Fan → Blower → Compressor

Increasing order of pressure and energy requirement.

1️⃣ Function:

Fan: Moves air or gas at low pressure; mainly for circulation.

Blower: Delivers air/gas at moderate pressure; used for forced draft or suction.

Compressor: Compresses air/gas to high pressure; used for storage or transmission.

2️⃣ Pressure Ratio (Outlet / Inlet Pressure):

Fan: Up to 1.1

Blower: Between 1.1 – 1.5 (sometimes up to 2.0)

Compressor: Above 1.5 (can go up to hundreds)

3️⃣ Energy Conversion:

Fan: Converts mechanical energy → velocity energy

Blower: Converts mechanical energy → pressure & velocity energy

Compressor: Converts mechanical energy → pressure energy

4️⃣ Typical Applications:

Fan: Cooling, ventilation, exhaust systems

Blower: Pneumatic conveying, furnace air supply, filtration systems

Compressor: Refrigeration, air tools, gas storage, process industries

5️⃣ Flow & Pressure Characteristics:

Fan: High flow, low pressure

Blower: Medium flow, medium pressure

Compressor: Low flow, high pressure

Q: If pressure increases, how does velocity react as per Bernoulli’s theorem?

According to Bernoulli’s Theorem:

The total energy (Pressure head + Kinetic head + Potential head) of a steady, incompressible, frictionless fluid remains constant along a streamline.

Relationship between Pressure and Velocity:

Pressure (p) and Velocity (v) are inversely related.

If pressure increases, velocity decreases, and vice versa — to keep total energy constant.

Reason:

Higher pressure means more potential energy in the fluid.

To maintain energy balance, kinetic energy (velocity) must reduce.

Practical Example:

In a converging nozzle, area decreases → velocity increases → pressure drops.

In a diverging section, area increases → velocity decreases → pressure rises.

Q: Which pump is used for high head requirement?

Multistage centrifugal pump is ideal for high head — pressure increases stage by stage while maintaining steady flow.

Key Points:

Consists of multiple impellers mounted in series within the same casing.

Each stage adds energy to the fluid, thereby increasing total discharge head.

Suitable for low to moderate flow rate but high-pressure (high head) duties.

Commonly used in boiler feed water systems, reverse osmosis plants, and high-pressure cleaning systems.

Delivers smooth, continuous flow and is efficient for large pressure rise.

Q: What is the role of module factor in filter integrity testing?

Definition:

The module factor is a correction or scaling factor used in filter integrity testing to account for the total effective filtration area (EFA) of a filter module or system.

Role & Importance:

Normalizes test results:

It converts the integrity test values (like diffusion flow or bubble point) from single filter element data to multi-filter systems.

Ensures accurate comparison:

Allows comparison between different filter sizes or configurations by relating results to a standard unit area.

Used in calculations:

Actual test limit = (Single cartridge limit) × (Module factor).

Ensures product integrity:

Helps confirm that all filters in the system meet the same integrity standard as validated individually.

Critical in validation & scaling:

Maintains consistency during scale-up from lab filters to production-scale systems.

Q: How does a Rotary Vacuum Dryer work?

Rotary Vacuum Dryer dries material by indirect heating under vacuum with gentle rotation — ensuring uniform, efficient, and low-temperature drying.

Working Principle:

Rotary Vacuum Dryer (RVD) works on the principle of heat conduction under vacuum.

The material is dried by indirect heating while being continuously rotated under vacuum to ensure uniform drying and prevent overheating.

Step-by-Step Working:

1. Loading:

Wet material is loaded into a sealed horizontal cylindrical drum.

2. Heating:

The jacket around the drum is supplied with hot water, steam, or thermal oil, which transfers heat through conduction to the product.

3. Vacuum Application:

A vacuum pump reduces pressure inside the drum, lowering the boiling point of moisture for faster drying at low temperatures.

4. Rotation:

The drum rotates slowly, ensuring continuous mixing and uniform heat transfer to all particles.

5. Moisture Removal:

Vaporized moisture is drawn out through the vacuum line and condensed in a receiver.

6. Discharge:

After drying, the dry product is discharged through a valve.

Advantages:

Suitable for heat-sensitive materials.

Ensures uniform drying and no oxidation.

Efficient moisture removal at low temperature.

Applications:

Used in pharmaceuticals, chemicals, food, and dye industries for drying powders, granules, and crystals.