Mechanical Engineers Placement Interview Questions

What is the difference between Fan and Blower?

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.

What is Heat Rate of Power Plant?

Heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the Turbine divided by the electrical energy output

What is Hydrodynamic Cavitation?

Hydrodynamic cavitation describes the process of vaporization in a constrained channel at a specific velocity.

Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure.

What is Difference between Hardness and Toughness?

Toughness is the ability of a material to absorb energy.

Hardness is the ability of a material to withstand wear.

What is the hottest part of Refrigerant in Refrigeration?


What does F.O.F Stand for Piping Design?

Face of Flange, The F.O.F (Raised face and Flat face) is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipe lines.

Where Multi stage Pump is Used?

Pressure washing of Aircraft, Trains, Boats and Road vehicles as well as Spray washing of industrial parts and Electronic components.

What does pump develop:- (a) Flow (b) Pressure

A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.

How to measure temperature of Bearing?

Normally the temperature range from 80 degree to 110 degree Celsius. So the following temperature measurement devices are used.

Dial Type Bearing Temperature Detector

Stator Winding Temperature Detector

Resistance Bearing Temperature Detector (Bearing RTD)

Specialized in Pin type RTD

Difference between Performance and Efficiency?

The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance.

Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.

What is the difference between Technology and Engineering?

Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is laws of force/load distribution.

How to Measure Temperature in Wet Bulb Thermometer?

Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

What are the Advantages and Disadvantages of using LPG in Car?


1. Complete combustion

2. Fuel saving

3. Homogenous combustion


1. As complete combustion is occurring ,more heat liberated,not advised for long journey, engine will be over heated

2. Installation is difficult

3. Reduce engine life efficiency

What is the difference between Speed and Economic Speed?

The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but the economical speed means the speed limit at which the machine works efficiently with least consumption of normal bikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers to drive such bikes at around 60 kmph to have maximum mileage.

What is Powder Technology?

Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed and compressed to make an alloy.

State all the laws of Thermodynamics?

There are three laws of the thermodynamics.

First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.

Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

State the difference between Unilateral and Bilateral Tolerance?

A unilateral tolerance is tolerance in which variation is permitted only in one direction from the specified direction.e.g. 1800 +0.000/-0.060

Bilateral tolerance is tolerance in which variation is permitted in both direction from the specified direction.e.g. 1800 +0.060/-0.060

What is the abbreviation of welding rod 7018?

7018 =

70=tensile strength 70000psi

1= welding position

8=current flux

What is difference between Welding and 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.

Which has more Efficiency Diesel Engine or Petrol Engine?

Diesel engine has the better efficiency out of two.

What is Sentinel Relief Valve?

It’s a special type valve system. The valve will open when exhaust casing pressure is excessive (high). The valve warns the operator only; it is not intended to relieve the casing pressure.

What is the difference between Specification,Codes, Standards?

Specification is describing properties of any type of materials.

Code is procedure of acceptance and rejection criteria.

Standard is accepted values and compare other with it.

Which is heavier 1kg Cotton or 1kg Iron?

Both of them have same weight.

What is Auto Dosing?

Auto dosing is an automated system of feeding the equipment with liquid products. It is the ideal way to ensure the correct calibrated dose at the right time every time in auto.

What is the difference between Sudden Force and Impact Force?

An impact is a high force or shock applied over a short time period when two or more bodies collide.

A force which applies on the body (material) suddenly is known as sudden force.

What is Geyser Pressure Valve?

To release the pressure created inside due to evaporation of water.

What is difference between Corrective actions and Preventive actions?

Corrective actions are taken on discrepancies noticed during inspection of products/documents/process whereas preventive actions are taken to eliminate the possibility of discrepancy in future.

How do you know air is fully saturated?

In its Dew point. (100% relative humidity condition)

What is the function of scoop in BFP (Boiler Feed water pump) in Thermal Power Station?

The Function of Scoop tube is regulating the varying amount of oil level in the coupling during operation of infinite variable speed.

What is Operating Pressure?

The amount of pressure nearest the point of performing work at the output end of a pneumatic system. The system operating pressure is used to specify the capability of valves and actuators.

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