Mechanical Placement Interview Question November 23, 2011 1. What is Sentinel Relief Valve? Ans. 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. 2. What is the difference between Specification,Codes, Standards? Ans. 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. 3. Which is heavier 1kg Cotton or 1kg Iron? Ans. Both of them have same weight. 4. What is Auto Dosing? Ans. 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. 5. What is the difference between Sudden Force and Impact Force? Ans. • 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. 6. What is Geyser Pressure Valve? Ans. To release the pressure created inside due to evaporation of water. 7. What is difference between Corrective actions and Preventive actions? Ans. Corrective actions are taken on discrepancies noticed during inspection of products/documents/process whereas preventive actions are taken to eliminate the possibility ofdiscrepancy in future. 8. How do you know air is fully saturated? Ans. In its Dew point. (100% relative humidity condition) 9. What is the function of scoop in BFP (Boiler Feed water pump) in Thermal Power Station? Ans. The Function of Scoop tube is regulating the varying amount of oil level in the coupling during operation of infinite variable speed. 10. What is Operating Pressure? Ans. 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. Mechanical Placement Questions December 8, 2011 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 time and moves towards a maximum value. 4. Compare Brayton Cycle and Otto Cycle? Ans. The heat addition and rejection processes in Otto cycle are of constant volume, whereas in Brayton cycle, they are of constant pressure. -Otto cycle is the ideal cycle for spark ignition engines. -Brayton cycle is the ideal cycle for gas power turbines. 5. What is the purpose of Scrapper Ring? Ans. scrap the excess lube oil from the cylinder walls. there by preventing oil from entering combustion zone. 6. What is DTSI Technology? Ans. DTSI stands for Digital Twin Spark Plug Ignition. The vehicles with DTSI Technology use 2 spark plugs which are controlled by digital circuit. It results in efficient combustion of air fuel mixture. • Digital - Since the spark generation will be initiated by a microchip. • Twin - Since two spark plugs will be used. • Spark ignition - Since the ignition will be done via a spark. 7. How to Find, Ductile-Brittle Transition Temperature in Metals? Ans. The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming. 8. What is the importance of Thermodynamics? Ans. All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers. 9. What is the difference between P11 and P12 Pipes? Ans. P11 the chromium molybdenum composition that is 1% ofchromium and 1/4% of molybdenum P12 the chromium molybdenum composition that is 1% ofchromium and 2% of molybdenum 10. State difference between AnitiFriction Bearing and Journal Bearing? Ans. Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rolls over each other. 1.)Why condenser is needed in steam power plant? Ans.-The function of the condenser is to condense exhaust steam from the steam turbine by rejecting the heat of vaporization to the cooling water passing through the condenser. 2.)What is absolute humidity and relative humidity? Ans.-Absolute humidity is the mass of water vapor divided by the mass of dry air in a volume of air at a given temperature. The hotter the air is, the more water it can contain.Relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity. 3.)What is viscosity? Ans.-The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of thickness. For example, honey has a higher viscosity than water. 4.)What is difference between power cycles and heat pump cycles? Ans.-Any thermodynamic cycle functions in a similar way. There are basically 3 interlinked energy sources at play: 1. A reservoir of heat energy at high temperature Eh 2. A reservoir of heat energy at low temperature Ec 3. Mechanical (driving) energy P. The power cycle provides high temperature heat energy Eh, harvests mechanical P and throws away low temperature energy into Ec. Whereas, The heat pump provides P, harvests Eh and throws away into Ec. 1.)Why Entropy decreases with increase in temperature? Ans. ds=dQ/T Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases. 2.)Definition of Octane Number and Cetane Number? Ans. Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine. Cetane No.- Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine. 3.)Which Mechanism is used in Automobile gearing System? Ans. Differential mechanism. 4.)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, or • Decrease the Pump Speed. 1.)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. 2.)Compare Brayton Cycle and Otto Cycle? Ans.The heat addition and rejection processes in Otto cycle are of constant volume, whereas in Brayton cycle, they are of constant pressure. -Otto cycle is the ideal cycle for spark ignition engines. -Brayton cycle is the ideal cycle for gas power turbines. 3.)What is the purpose of Scrapper Ring? Ans. Scrap the excess lube oil from the cylinder walls. there by preventing oil from entering combustion zone. 4.)State difference between AnitiFriction Bearing and Journal Bearing? Ans. Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have larger contact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rolls over each other. 1.)What does pump develop:- (a) Flow (b) Pressure Ans.A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow. 2.) Difference between Performance and Efficiency? Ans.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. 3.)What is Sentinel Relief Valve? Ans.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. 4.) What is the difference between Specification,Codes, Standards? Ans. 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. 1.)What is difference between Corrective actions and Preventive actions? Ans.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. 2.)What is Operating Pressure? Ans.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. 3.)What are the Advantages and Disadvantages of using LPG in Car? Ans.Advantages 1. Complete combustion 2. Fuel saving 3. Homogeneous combustion. Disadvantages 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. 4.)What is difference between Welding and Brazing? Ans. 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.
Posted on: Thu, 22 Jan 2015 11:09:46 +0000