Skip to main content

Part -5 Most commonly asked Mechanical Interview Questions



Most commonly asked Mechanical Interview Questions with answer


1. Why the Centrifugal Pump is called High Discharge pump?
Ans. Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is given in the following formulae:
Centrifugal force F= (M*V2)/R.
Where,
M-Mass
V-Velocity
R-Radius

2. How Cavitation can be eliminated by Pump?Ans. Cavitation means bubbles are forming in the liquid.
  • To avoid Cavitation, we have to increase the Pump size to One or Two Inch
  • To increase the pressure of the Suction Head
  •  Decrease the Pump Speed.
3. Why Cavitation will occur in Centrifugal Pump and not in Displacement Pump?Ans. The formation of cavities (or bubbles) is induced by flow separation, or non-uniform flow velocities, inside a pump casing. In centrifugal pumps the eye of the pump impeller is smaller than the flow area of pipe. This decrease in flow area of pump results in increase in flow rate. So pressure drop happened between pump suction and the vanes of the impeller. Here air bubbles or cavities are formed because of liquid vapour due to increase in temperature in impeller. This air bubbles are transmitted to pump which forms cavitation.

4. Which Pump is more Efficient Centrifugal Pump or Reciprocating Pump?Ans. Centrifugal pump. Because flow rate is higher compared to reciprocating pump. Flow is smooth and it requires less space to install. Lower initial cost and lower maintenance cost.

5. Why Centrifugal Pump is not called as a Positive Displacement Type of Pump?Ans. The centrifugal has varying flow depending on pressure or head, whereas the Positive Displacement pump has more or less constant flow regardless of pressure.
Likewise viscosity is constant for positive displacement pump where centrifugal pump have up and down value because the higher viscosity liquids fill the clearances of the pump causing a higher volumetric efficiency. When there is a viscosity change in supply there is also greater loss in the system. This means change in pump flow affected by the pressure change.
One more example is, positive displacement pump has more or less constant efficiency, where centrifugal pump has varying efficiency rate.

See related more FAQs <<<< Click Here >>>>


Labels:

Popular posts from this blog

Part -7 Most commonly asked Mechanical Interview Questions

Most commonly asked Mechanical Interview Questions What are the different types of fits? Explain? On the basis of Indian standards fits can mainly be categorised into three groups: > Clearance Fit : These types of fits are characterised by the occurrence of a clearance between the two mating parts. The difference between the minimum size of the hole and the maximum size of the shaft is called the minimum clearance, the difference between the maximum size of the hole and the minimum size of the shaft is known as maximum clearance. > Interference Fit : In these types of fits the size of the mating parts are predefined so that interference between them always occurs. The tolerance zone of the hole is completely below the tolerance zone of the shaft. > Transition Fit : As the name suggests these type of fit has its mating parts sized limited to allow either clearance or interference. The tolerance zone of the hole and the shaft overlaps in case of such fits. For a shaf...
Read more

Part -2 Most commonly asked Mechanical Interview Questions

Most commonly asked Mechanical Interview Questions 1. What is the difference between Critical Speed and Whirling Speed? Ans. In Solid mechanics, in the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites the natural frequency of a rotating object, such as a shaft, propeller or gear. As the speed of rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases system vibration. The resulting resonance occurs regardless of orientation.Whirling Speed is due to the unbalanced forces acting on a rotating shaft. 2. How a Diesel Engine Works as Generator? Ans. Diesel engine is a prime mover, for a generator, pump,and for vehicles etc. generator is connected to engine by shaft. mostly in thermal power plat ,there is an engine is used to drive generator to generate power. 3. Explain Second Law of Thermodynamics? Ans. The entropy of the universe increases over tim...
Read more

ULTRASONIC TEST

ULTRASONIC TEST INTRODUCTION This method is used to test a variety of both metallic & non metallic products such as welds, forgings, castings, sheets, etc. It has an advantage of detecting sub-surface discontinues with accesses to only one side of the specimen. In this method beams of high frequency sound waves are introduced into the material being tested. The sound waves travel through the material with some loss of energy & are reflected back . This is detected & analysed to detect the presence of flaws. This test employs ultrasonic waves. These waves are mechanical waves that consist of oscillations or vibrations. METHOD TRANSMISSION SYSTEM This method employs two Transducers, one for sending & other for receiving the pulses. These may be short or continuous & are transmitted through the material. The result gets displayed on the CRO connected. The settings of the CRO can be adjusted with respect to time & distance. Prior to testing couplant is used to prov...
Read more