Technical Questions

Technical Questions:
PUMP
Q 1.) How can you increase the head of a pump without adding another pump?
A) The head of a pump can be increased by adding another pump in series but if you
have to use the same pump, we can add stages/impellers but we have to modify
the housing of the pump. Another method is by increasing the rpm or diameter of
the impeller.
Q 2.) What is NPSH? Should NPSH required be greater than available NPSH?
A) NPSH is the net positive suction head. Available NPSH should always be higher
than required NPSH by almost 10 percent or 3ft otherwise cavitation may occur.
Q 3.) What is the difference between shut off head and free delivery?
A) Shut off head is the pressure heat at the discharge side of the pump when
discharge valve is closed. Free delivery is the maximum head achievable by a
pump at which flowrate drops to zero.
Q 4.) What is cavitation in pump?
A) Cavitation is the absence of film. In pumps, it is the absence of liquid medium i.e.,
presence of vapour medium.
Q 5.) When is a compressor used and when is a pump used?
A) A pump is used when the medium is liquid and compressor is used when medium
is gas.
Q 6.) Draw the efficiency curve of a pump?
A)
FLUID MECHANICS
Q 7.) How can you find the pressure drop of a horizontal piece of pipe? Show
mathematical steps.
A) For a horizontal piece of pipe, pressure drop can be calculated by the Bernoulli’s
equation. For a horizontal pipe, elevation head is zero. For constant velocity
system, kinetic head is zero. Pressure drop is now equal to head loss. For a piece
of pipe only major head loss is present calculated by the formula f (l/d) v2/2g.
THERMODYNAMICS
Q 8.) What is the difference between chiller, cooler and condenser?
A) Condenser removes the latent heat; cooler removes the sensible heat and chiller is
a cooler but operates at lower temperatures as compared to ambient temperature.
Q 9.) What is a refrigeration cycle?
A) Refrigeration cycle is a thermodynamic cycle in which work is done on the system
to remove heat from the system. An example is reverse Carnot cycle.
Q 10.) What is Carnot Cycle? Explain its graph.
A) Carnot cycle is an ideal cycle in which energy is converted into work. The V-P
Graph has 4 processes. Two are adiabatic and other two isothermal one after the
other. First isothermal expansion with heat in then adiabatic expansion with work
out. Second isothermal compression with heat out then adiabatic compression
with work in.
Q 11.) What is fugacity?
A) Fugacity is the measure of how much a gas deviate from standard state under
variation of pressure and mole fraction.
Q 12.) Define the compressibility factor of a gas.
A) Compressibility factor of a gas is the ratio of volume of real gas to volume of ideal
gas. For ideal gas it is one. For real gas, it is less than one.
FLOWMETER
Q 13.) What is a flow meter? What is the industrial use of pitot tube?
A) Pitot tube is not used for high flowrate conditions because of its lesser accuracy.
Mostly it is used for water operations like ETP etc.
Q 14.) How does a flowmeter work?
A) Flowmeter works by measuring the pressure difference to calculate the flowrate.
CONTROLLER
Q 15.) What is PID Controller? How and where it is used?
A) PID controller is Proportional Integral Derivative Controller. It works on feedback
control loop and most accurate regulator but not feasible for time delay or slow
disturbance processes.
WATER TREATMENT
Q 16.) What is the difference between coagulation and flocculation?
A) In coagulation, liquid phase starts to convert into precipitates (these are small and
do not settle down). In flocculation, the precipitates accumulate more mass to
become flocks (flocks settle by gravity).
DISTILLATION COLUMN
Q 17.) How would you control the change in pressure in a distillation column?
A) By changing the condenser duty, we can control the pressure in our distillation
column.
Q 18.) Which type of distillation column trays have the highest pressure drop?
A) Bubble cap trays.
Q 19.) Which type of distillation column trays have the lowest pressure drop?
A) Sieve trays.
VALVES
Q 20.) Which type of valves have the lowest pressure drop?
A) Butterfly valves have the lowest pressure drop.
Q 21.) Which type of valve has the highest pressure drop?
A) Globe valve has comparatively highest pressure drop.
HEAT TRANSFER
Q 22.) Why is Ft factor needed for LMTD in an exchanger?
A) Ft factor is a correction factor used when there is a cross flow. If exchanger is
double pipe, Ft factor will not be needed. If flow is both parallel and counter at the
same time, Ft factor will be calculated.
My name is hadeed ilyas, Im a polymer engineer who graduated last year from ned
university. Since then ive been working at pakarb Pakistan , which is a plastic pipe
manufacturing company and specializes in PVC and hdpe pipes for local and
commercial use. Since I joined ive developed a great understanding of the
extrusion process and all the underlying responsibilities that come wit it. Im
currently incharge of all the production and planning activities across both Pvc and
HDPE division of the company. Since I joined ive tried to significantly reduce
downtimes after small, continuous improvements. Im in charge of all the human
resource. My final year project was based on reducing carbon waste by recycling
Expanded polystyrene incorporating bio filler in them. We managed to make a
methodology where we can properly incorporate bio filler in EPS such so that It
can be used for various applications.

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