all interview queston

8/11/2019 All Interview Queston

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QUESTION:Whats the difference between welding and soldering?

ANSWER: # 1Welding is joint between the two metals with high temp &

Mostly used in the hard metals

Soldering is a two or more metals joined together by a Melting& used in the light metals______________________________________________________________

QUESTION:What are the supports using in critical pipe line and what are the types of support using oil gas,

power plantANSWER: # 2First of all critical pipelines is classified based on

Thermal limits or vibration limitsfor thermally critical pipes we generally use springSupports, guides for allowing expansion of pipefor vibration we use snubbers or expansionloops, anchors

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QUESTION:What is npsh and how to calculate it for a centrifugal pump?

ANSWER: # 2NPSH is the acronym of Net Positive Suction Head, there r 2 NPSH one is NPSH (a) and

NPSH i.e. , NPSH available and required Always NPSH (a) should be higher than theNPSH this NPSH will be determined by the pump manufacturer

ItselfTOcalculate NPSH (a)NPSHa = Atm pressureacting on the liquid + static head - vapour pressure of the liquid-

pressureLoss in the suction piping - pressure loss due to the suction strainer

QUESTION:What is the effect of rust on seet metal?

ANSWER: # 2DUE TO CORROSION THIS RUSTING OCCURS & RESULTS ARE

1 WEIGHT LOSS2 STRENGTH OF METAL (LOAD CARRINNG CAPACTY)3 WILL AFFECT OTHER METAL IN CONTACT WITH THAT METAL

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QUESTION:What is the difference between four strokes and two strokes IC ENGINE?

ANSWER: # 1in four stroke engine two revolution crank shaft one power stroke will be produced in twostroke engine one revolution crank shaft one power stroke will be produced


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QUESTION:What is the difference between four strokes and two strokes IC ENGINE?

ANSWER: # 2

In 4 stroke engine crank revolute two times and one powerStroke be produced that to in 2 stroke engine one revolution made bye the crank

Shaft and one power stroke is occurred

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QUESTION:What is the difference between four stroke and two stroke ic engine

ANSWER: # 32 Stroke engines are reversible rotation but 4 strokes are not

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QUESTION:Difference between strainer and filter.

ANSWER: # 3Strainer for coarse size, filter is more accurate than

Strainer.

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QUESTION:Why screw pumps are used instead of centrifugal pump?

ANSWER: # 1Give more pressure at exit fluid

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3/19

QUESTION:Why screw pumps are used instead of centrifugal pump?

ANSWER: # 2Screw pump is positive displacement type pump and when we

Require high pressure screw pump is used, where as centrifugal pump is non-positive type andused for high flow less pressure________________________________________________________ ___

QUESTION:why screw pumps are used instead of centrifugal pump?

ANSWER: # 3Screw pumps r +ve displacement with high pressure and low

Discharge

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QUESTION:what is the difference between impulse and reaction turbines ?

ANSWER: # 5

The main difference between reaction and impulse turbine isthat reaction turbine operates on Newtons third law of motion that is when steam leaves the

rotor blades at an angle the turbine is pushed towards opposite direction and to a certain extent

static pressure impulse is also utilized for the movement Where as in impulse turbine onlykinetic head of steam is responsible for movement of turbine that is movement of turbine takesplace in direction of impact and not opposite to the impact as was the case with reaction turbines

QUESTION:Difference between performance and efficiency?

ANSWER: # 1

every machine are meant to convert one form of energy toother, now performance means whether machine is able to convert it or not & efficiency meanshow effectively it is able to convert

QUESTION:difference between steam hammering and water hammering

ANSWER: # 1


4/19

Actually the main difference between steam hammering and

water hammering is, In a steam pipe if there is some water accumulation it is carried over by thehigh pressure and high temperature steam and it creates hammering this is known as water

hammering in steam pipes Similarly in a water pipe is steam enters it will create some sound this

is known as steam hammering

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QUESTION:difference between steam hammering and water hammering

ANSWER: # 3Consider a pipe line with a regulating valve, carrying water

from a reservoir to some sumpInitially the valve is imagined to be fullyopened and water will be freely flowing Suppose we shut the

valve suddenly, The Water coming the upstream will besubjected to impact the Valve shutter , causing severe boostin water pressure and produces vibrations in

pipeline ,known as water hammerSteam Hammer may be attributed to the similar

effect caused by working steam

QUESTION:Which one is more efficient? A four stroke engine or a two stroke and why?

ANSWER: # 14 Stroke engine is more efficient primarily because of the

presence of valves which precisely control the flow of

charge into the chamber and exit the exhaust gases with

proper timing which is hard to achieve by ports in a 2stroke engine________________________________________________________ ___

QUESTION: Which one is more efficient? A four stroke engine or a two stroke and why?

ANSWER:

# 2 Four stroke engine is more efficient than two stroke engineas the fuel consumption is four stroke is less and the

combustion power in four stroke engine is greater there byreducing the emission of smellier gases

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ANSWER: # 3A four stroke is more efficient There are two revolutionsof the crankshaft for every complete cycle, whereas the two

stroke rotates the engine only once________________________________________________________ ___


ANSWER: # 4For the same size of cylinder, Some of the power and

compression stroke get wasted due to the presence of portsImproper combustion due to the mixing of burnt gases with

fuel________________________________________________________ ___


ANSWER: # 5A four stroke engine is more efficient than 2-stroke due thefollowing reasons:-

1)For the same size of cylinder, Some of the power andCompression stroke get wasted due to the presence of ports

Improper combustion due to the mixing of burnt gases withFuel2)The fuel consumption is four stroke is less and theCombustion power in four stroke engine is greater there byreducing the emission of smellier gases

3 )presence of valves which precisely control the flow ofcharge into the chamber and exit the exhaust gases with

proper timing which is hard to achieve by ports in a 2

stroke engine________________________________________________________ ___

QUESTION: Which one is more efficient? A four stroke engine or a two stroke and why?

ANSWER: # 64s engine is more efficient than 2s as compared with the

following:

load: 4s more load carrying capacity


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2s less load carrying capacity

efficiency: 4s more efficient2s less efficient

power :4s more

2s less

the reasons being ,the presence of valves in 4s helps it totake in fresh charge and drive out the exhausts more

effectively then in 2s

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ANSWER: # 74 strokes is more efficient than 2 stroke in terms of fuelconsumption and emission

But in terms of power, 2 stroke is more efficient itproduces power in 1 revolutions of crankshaft than 4 strokesin which 2 revolutions requiredMoreover, the worlds most powerful engine is turbocharged

2 stroke diesel engine of around 1,00,000 hp developed by

Aioi works, Japansome one had made a mistake in the answers shown aboveInforming 4 strokes is better in power

QUESTION: How will we know in which direction a liquid is flowing in a pipe?

ANSWER: # 1Depending upon the direction of delivery and towards the

end flow direction

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ANSWER: # 2IN THE DIRECTION WHERE THE PRESSURE OF FLUID IS LOW (I efrom high to low pressure region)

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ANSWER: # 3flow of liquid depends upon the pressure, so the liquid flow


7/19

from high pressure to low pressure_________________________________________________________


ANSWER: # 4from High pressure region to low pressure region always

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ANSWER: # 5Fluid will not always flow from high pressure region to low

pressure region The correct answer: is fluid flows fromhigh head to low head

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ANSWER: # 6The Direction of flow inside a pipe can be rightly judged

with the help of touching on the pipe The vibration wouldrightly be able to understand the direction and also the

quantity of flow________________________________________________________ ___


ANSWER: # 7The fluid always not depend on the direction, the correct

ANSWER: is a fluid flow from high head to low head in thisregion________________________________________________________


ANSWER: # 8by visual inspection

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QUESTION: what is discharge? how is measured?

ANSWER: # 2Q = A x Vwhere A is the area in which liquid passing

V is the velocity of the liquid in that system


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so it is in m^3/sec

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QUESTION: why the exhaust temp of gas turbine is more than steam turbine

ANSWER: # 1Steam, unless it is super-heated, is less because CO2 can

achieve much hotter temperatures at a gas state Steamjust reaches 212 degrees_______________________________________________________________

QUESTION: types of pipes

ANSWER: # 1Seamless pipe

Electric resistance welded pipe

cast pipes

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QUESTION: what is the exact requirement of priming?

ANSWER: # 1To remove the air from pump cavities________________________________________________________

QUESTION: what is the exact requirement of priming?

ANSWER: # 3priming is done in pumps to remove the entrapped air from

the suction pipe thus aiding in smooth operation and

avoiding in excess load on the pump

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QUESTION: what is the exact requirement of priming?ANSWER: # 4

in case of positive displacement pumps (ex :reciprocating Pump) the piston or mechanical

member directly creates the vacuum or lower pressure such that the water or liquid is

sucked in case of centrifugal pumpsthe impeller just displaces the water due to the centrifugalforce as the water at center of impeller is displaced to the


9/19

casing partial vacuum gets created at the eye of impeller and hence suction of new water takesplaceif there is no water around impeller only air is present and it cant be displaced by thepump impeller as air is compressible the pump impeller is designed to handle water or liquidtherefore to remove the air and fill the casing with water the priming is carried out there is noneed of priming if there is an foot valve and its working well

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QUESTION: In a Steam Turbine, where does the maximum loss of efficiency occur?

ANSWER: # 1Heat lost through cooling water in condenser

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QUESTION: can we say all tapered pipes as nozzle?ANSWER: # 1Yes, if the diameter reduces uniformly from a larger Diameter to

a smaller Diameter laminar flow________________________________________________________ ___

QUESTION: can we say all tapered pipes as nozzle?

ANSWER: # 2based on the formula [dA/A=(m^2-1)*dv/v]

if mach number and change in area known, what ever the signwe get -ve or +ve we will decide

if dA=+VE and m>1 then dv=+ve hence nozzle

if dA=-VE and m>1 then dv=-ve hence diffuser

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QUESTION: can we say all tapered pipes as nozzle?ANSWER: # 3No, Not all tapered pipes are nozzlesIt may be diffuser or simply a pipe depending upon the flow

conditions like mach number and pressure drop________________________________________________________ ___


10/19

QUESTION: can we say all tapered pipes as nozzle?

ANSWER: # 4no based on direction we say diffuser also , and also basedon purpose thats use only pipe

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QUESTION: What are all the possibilities discharge will be low in the pumps?

ANSWER: # 11 Internal Leakages in pumps2 Lesser speed of a motor due to electrical power supplyProblems3 High load on pumps4 Chocked output filter5 Chocked input filter6 External leakages from the pump7 Change in viscosity of the fluid________________________________________________________ ___


ANSWER: # 2DUE TO SLIP OCCURED IN THE PUMP

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ANSWER: # 3also design defects matter in discharge if there is bending inthe pipe then losses will be more that affect the

discharge


ANSWER: # 5also checked the direction of rotation of pump due to

wrong electrical connection________________________________________________________ ___


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ANSWER: # 6may be due to lack of proper venting in suction and

discharge lines

QUESTION: exactly how a vapor bubble can destroy impeller?

ANSWER: # 1normally vapour bubbles are formed in an impeller due tothe phenomenon of turbine cavitations the vapour bubblesbeing low pressure points raise to the surface hitting the

impeller ,get ruptured between the high pressure fluid andthe impeller body and eventually burst damaging the

impeller body

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ANSWER: # 2vapour bubble is one which cause damage the pump is

not a pressure developing device ,due to rotation of

impeller speed a centrifugal force is created in case ofcentrifugal pump where vacuum is created at centre which

air may mix with fluid to form bubbles ,where rotation of

impeller which strikes the bubbles which the oxidation

effect damage the pump casing & impeller________________________________________________________ ___


ANSWER: # 3In certain point in fluid the pressure of localized pointor area decreases below vapour pressure this causes theevaporation of fluid and vapour bubbles are formed Thesebubbles rise in the fluid and at certain point, where the

pressure is above vapour pressure, the bubbles blast If itoccurs our surface (Turbine blade or any other), it causesthe pressure to effect the surface too And the surfacecomes under stress After that stress is relived thisprocess continues I e stressing and reliving this cause


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development of fatigue load, which inturen cause the

failure of the impeller

QUESTION: how a centrifugal pump is working?ANSWER: # 1

fluid is enter in center of the impeller, and is picked up by

impeller, fluid move radically due to centrifugal forceNodemand of fluid in centrifugal pump so does t need

pressure relief valveIn this used only High volume & low pressure condition________________________________________________________ ___

QUESTION: how a centrifugal pump is working?

ANSWER: # 2Pump is adding energy to a fluid The energy addition is

achieved by means of centrifugal force in centrifugal

pump When fluid enters into the impeller eye (Center of theimpeller where vacuum exists because of pumping), the fluidwill be thrown out of impeller eye by a centrifugal force

which adding the velocity to the fluid The volutesurrounding the impeller guides the fluid to the discharge

and it converts the velocity energy to pressure energy(head) when u keeps the discharge valve closed, it willattain the shut off head once the discharge valve isopened the fluid will start to flow and head will startdecreases since the energy addition is shared by pressure

energy and velocity energy________________________________________________________


ANSWER: # 3

Centrifugal pump basically work on the principal ofPressure difference The pump causes the decrement in thepressure so that fluid flows from high pressure to lowpressure zoneIt has no doubt that centrifugal force also plays there

roles, but the majority portion of picking the fluid isdone by Pressure difference only

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13/19


ANSWER: # 4 centrifugal pumps work by converting the kinetic energy ofa liquid into pressure energy it does this by means of twomajor components, i.e. the impeller and the diffuser as the

impeller is rotated by means of a motor or engine, a lowpressure region is created at the impeller eye causing the

liquid to be sucked into the eye as the impeller rotatesthe sucked fluid is thrown out with force through the

periphery of the impeller now the diffuser comes intoaction the diffuser due to its shape of varying x sectionalarea causes the liquid to slow down and from Bernoullisprinciple, a reduction in kinetic head will be compensated

by an increase in pressure head thats basically how itworks

QUESTION: IN A THERMAL POWER PLANT, WHY IS THE USED STEAMCONDENSED INTO WATER AND THEN SENT BACK TO THE BOILER, WHY NOT

DIRECTLY REHEATING THE SAME STEAM??

ANSWER:

# 1 because to avoid erosion

________________________________________________________ ___1 No

QUESTION: IN A THERMAL POWER PLANT, WHY IS THE USED STEAMCONDENSED INTO WATER AND THEN SENT BACK TO THE BOILER, WHY NOT

DIRECTLY REHEATING THE SAME STEAM??

ANSWER:

# 2 Because the specific volume of steam is more for steamcompared to water so if we are not condensing it, theentire power generated by the turbine will be utilized only

to pump the steam Also as per second law ofthermodynamics, there must be a source and a sink Hereboiler acts as a source and condenser as a sink

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QUESTION: IN A THERMAL POWER PLANT, WHY IS THE USED STEAMCONDENSED INTO WATER AND THEN SENT BACK TO THE BOILER, WHY NOTDIRECTLY REHEATING THE SAME STEAM??

ANSWER:

# 3 for pumping the steam from the turbine to boiler requires

more energy this energy consumes nearly 75% of turbine itreduces efficiency of plant________________________________________________________

QUESTION: which case we will find maximum pressure and flow in centrifugal pump-circular casing or volute casingANSWER:

# 1 Volute Casing

QUESTION: if in centrifugal pump suction, discharge and impeller size constant and motor

rpm increasewhatis the effect on pressure and flow

ANSWER: # 1Pressure increase and flow remain constant

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rpm increasewhatis the effect on pressure and flowANSWER:

# 2 Both the flow and the pressure will increase based on theAffinity law which say if the RPM increase by a factorOf 2 the new flow increase also by a factor of 2 whereasThe pressure or head of the pump will increase by a factorOf 4

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rpm increasewhatis the effect on pressure and flow

ANSWER:

# 3 As RPM will increase, it will cause increase in VelocityOf Impeller, as diameter is fixedThis increase velocity will inturen cause increase in

Velocity of fluidSo discharge: Q =AV

Will increase


15/19

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QUESTION: If I import a steam boiler from USA and want to install it in India, will it work ?

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QUESTION: If I import a steam boiler from USA and want to install it in India, will it work ?

ANSWER:

# 2 generally it will not work because of normal and boilingTemperature in India and US will vary due as atmospheric

Temperature of India and US r differentHowever if the steam boiler is designed to meet the

Specification of both the countries then itll work!!!!________________________________________________________

QUESTION: IN THERMAL POWER PLANT WHY WE ARE USING SINGLE SHAFTFOR THE COUPLING OF HP, IP&LOW PRESSURE TURBINES WE CAN USEINDIVIDUAL SHAFT FOR EACH TURBINE ?ANSWER: # 1

However 3 turbines are having individual shafts onlyMay be in some designs HP & IP are in single shaft and LP

Only in another shaft for 110 MW BHEL designFor any 500MW, All 3 turbines are coupled with individualShafts onlyThis concept is bases on Torque and Steam pressure

QUESTION: In a thermal power plant: Why the Dearator is placed at height and mostly at 15

5mtr?

ANSWER:

# 1 so as to net positive suction head (NPSH) for the boilerFeed pump (BFP) in conjecture with booster pump

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QUESTION: In a thermal power plant: Why the Dearator is placed at height and mostly at 15

5mtr?

ANSWER:# 2 for net positive suction head for feed pump

QUESTION: suppose that there is a gas turbine of 110MW having 3 stages, and compressorhaving 17 stages what will happened when the stages of turbine increases to 6


16/19

ANSWER:

# 1 there is no any effect of increasing the stages of turbine

QUESTION: how will effect of water injection on turbine load and corresponding MW output(not water washing)

ANSWER:# 1 I think the concept of governor is the ANSWER: Iewhen loadIs increased speed decreases and governor increases theSupply of water and vice versa

QUESTION: what is the difference between technology and engineering?

ANSWER:

# 1 Engineering is cause and technology is the effectI mean to say that engineering is the art of using

Scientific principles to create new technologies

Hope u get the point

QUESTION: what are the supports using in critical pipe line and what are the type of supportusing oil gas, power plantANSWER:

# 1 dead load support, Tie rod type supports are generally usedFor critical pipe lines

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QUESTION: what are the supports using in critical pipe line and what are the type of supportusing oil gas, power plantANSWER:

# 2 first of all critical pipeline is classified based onthermal limits or vibration limitsfor thermally critical pipes we generally use springsupports, guides for allowing expansion of pipefor vibration we use snubbers or expansion loops, anchors

QUESTION: Which type of impeller has highest speed Backward, Forward ,Straight?

ANSWER:# 1 the backward curved has the highest speedIf we plot the outlet cure diagram for these three

condition, we found that absolute velocity and flow

velocity remains constant, only the relative velocitycomponent changes with the curvation of vaneIn the backward curve vane, it has highest value of U (as


17/19

per the diagram)

QUESTION: why more extractions are restricted in steam turbine

ANSWER:

# 1 it decreases the efficiency of the turbine

basically, steam extractions is done in the steam turbineto recover the part of the heat loss in the condenserat the same time we are loosing work done alsoif we extract more steam from turbine, work done by the

steam turbine will reduce________________________________________________________ ___

0 Akm

QUESTION: why more extractions are restricted in steam turbine

ANSWER:

# 2 This extraction is some times useful to usBy extract some steam at the last state of L P turbine, wecan reduce the back pressure and it enhances the vacuum

function in condenserBut as extraction are increases, the main rotation ofturbine decreases due to insufficient pressure

QUESTION: difference between antifriction bearing and journal bearing

ANSWER:

# 1 anti friction bearings are also called roller bearingswhich is having a point contact hence it has less friction

as compared to journal bearing

QUESTION: How can we calculate BOILER capacity

ANSWER:

# 1 Based on the super heated steam raising capacity per hourof the boiler

QUESTION: What is the difference between head & total head in pump

ANSWER:

# 1 Total head is the sum of pressure head and suction headPressure head refers to the height unto the pump can suck

the water and the pressure head refers to the height whichthe pump can force the water________________________________________________________ ___



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ANSWER:

# 2 Total head = suction head + Discharge head or delivery headsuction head means from how much depth the pump can suck theliquid

Delivery head means how much height it can deliver the liquid

________________________________________________________ ___ 1 Yes


ANSWER:

# 3 The discharge head of the pump is equal to the summation of

static head and friction head in the discharge pipeHowever ; the pump total head is equal to the summation ofstatic head and the friction head in the suction anddischarge pipeN B Static head = Is the vertical distance between thewater level in the suction and discharge tanksfriction head = is the head loss due to pipe friction and

fittings

QUESTION: What is the vane diagram in centrifugal pump

ANSWER:# 1 VANE diagram drawn between flow and rpm of pump

QUESTION: what is the function of nozzle? what happened when the fluid flow through ataper pipe I e what about inlet and outlet velocity, pressure,ANSWER:

# 1 nozzle is a device which converts (high pressure and lowvelocity fluid) at inlet into (high velocity fluid and low

pressure) at exit

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QUESTION: what is the function of nozzle? what happened when the fluid flow through ataper pipe I e what about inlet and outlet velocity, pressure,ANSWER:

# 2 nozzle is the device which is used for converting fluidspressure energy into kinetic energy if a fluid is passedthrough a tapered pipe its velocity is higher at the outlet

as compared to inlet


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QUESTION: What is difference between Installation and Commisioning ????

ANSWER:

# 1 installing means just install any device or machine inwithout working condition

and commissioning means to run that same machine or devicethat was installed to convert that dead machine intoworking condition properly according to the desiredparameters on safe condition is known as commissioning

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QUESTION: What is difference between Installation and Commissioning ????

ANSWER:

# 2 installation means just we place the machine ideallycommissioning means we have to make to machine to run

that means we have to check whether the machine is runningproperly or not otherwise is there any leaks or whetherwe are getting our desire parameters or not

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