The excess of the sum of pressure & velocity heads over the vaporpressure of the liquid at the suction is called the(A) Static submergence(B) Net positive suction head (NPSH)(C) Cavitation sensitivity(D) Priming

The excess of the sum of pressure & velocity heads over the vaporpressure of the liquid at the suction is called the
(A) Static submergence
(B) Net positive suction head (NPSH)
(C) Cavitation sensitivity
(D) Priming
by

1 Answer

Answer :

(B) Net positive suction head (NPSH)
by

Related questions

The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the (A) Discharge (B) Suction (C) Suction minus vapor pressure of the liquid at suction temperature (D) Discharge minus vapor pressure of the liquid at the discharge temperature

Description : The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the (A) Discharge (B) Suction (C) Suction minus vapor ... of the liquid at suction temperature (D) Discharge minus vapor pressure of the liquid at the discharge temperature

Last Answer : (C) Suction minus vapor pressure of the liquid at suction temperature

The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the (A) Discharge (B) Suction (C) Suction minus vapor pressure of the liquid at suction temperature (D) Discharge minus vapor pressure of the liquid at the discharge temperature

Description : The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the (A) Discharge (B) Suction (C) Suction minus vapor ... of the liquid at suction temperature (D) Discharge minus vapor pressure of the liquid at the discharge temperature

Last Answer : (C) Suction minus vapor pressure of the liquid at suction temperature

Net positive suction head (NPSH) of a centrifugal pump must be (A) Greater than the vapour pressure of the liquid (B) Less than the vapour pressure of the liquid(C) Equal to the vapour pressure of the liquid(D) Less than barometric pressure

Description : Net positive suction head (NPSH) of a centrifugal pump must be (A) Greater than the vapour pressure of the liquid (B) Less than the vapour pressure of the liquid (C) Equal to the vapour pressure of the liquid (D) Less than barometric pressure

Last Answer : (A) Greater than the vapour pressure of the liquid

Circulation pump is located below the evaporator to (A) Avoid cavitation (B) Avoid frequent priming (C) Create more suction head (D) None of these

Description : Circulation pump is located below the evaporator to (A) Avoid cavitation (B) Avoid frequent priming (C) Create more suction head (D) None of these

Last Answer : (C) Create more suction head

A centrifugal pump loses prime after starting. The reason of this trouble may be (A) Incomplete priming (B) Too high a suction lift (C) Low available NPSH and air leaks in the suction pipe (D) All (A), (B), and (C)

Description : A centrifugal pump loses prime after starting. The reason of this trouble may be (A) Incomplete priming (B) Too high a suction lift (C) Low available NPSH and air leaks in the suction pipe (D) All (A), (B), and (C)

Last Answer : (D) All (A), (B), and (C)

Cavitation occurs in a centrifugal pump when the suction pressure is (A) Less than the vapour pressure of the liquid at that temperature (B) Greater than the vapour pressure of the liquid at that temperature (C) Equal to the vapour pressure (D) Equal to the developed head

Description : Cavitation occurs in a centrifugal pump when the suction pressure is (A) Less than the vapour pressure of the liquid at that temperature (B) Greater than the vapour pressure of the liquid at that temperature (C) Equal to the vapour pressure (D) Equal to the developed head

Last Answer : (A) Less than the vapour pressure of the liquid at that temperature

Pick out the wrong statement about cavitation. (A) Sudden reduction of pressure in a fluid flow system caused by flow separation, vortex formation or abrupt closing of valve leads to cavitation (B) Cavitation may be caused due to boiling of liquid by decreasing the pressure resulting in formation & collapse of vapor cavities (C) Cavitation begins at higher static pressure and lower velocity in larger diameter pipelines resulting in audible noise(D) Large scale cavitation cannot damage pipeline, restrict fluid flow anddamage steam turbine blades

Description : Pick out the wrong statement about cavitation. (A) Sudden reduction of pressure in a fluid flow system caused by flow separation, vortex formation or abrupt closing of valve leads to cavitation ... (D) Large scale cavitation cannot damage pipeline, restrict fluid flow and damage steam turbine blades

Last Answer : (D) Large scale cavitation cannot damage pipeline, restrict fluid flow and damage steam turbine blades

The main drawback of centrifugal pump is a)necessity of priming b) discharge from pump varies with the load of water c) For high heads efficiency is low up to 50% d) the suction lift is limited to 6 metre e) all of the above*

Description : The main drawback of centrifugal pump is a)necessity of priming b) discharge from pump varies with the load of water c) For high heads efficiency is low up to 50% d) the suction lift is limited to 6 metre e) all of the above*

Last Answer : e) all of the above*

What causes cavitation in centrifugal pump? (A) High suction pressure (B) Low barometric pressure(C) Low suction pressure(D) High suction velocity

Description : What causes cavitation in centrifugal pump? (A) High suction pressure (B) Low barometric pressure (C) Low suction pressure (D) High suction velocity

Last Answer : (C) Low suction pressure

Cavitation can be prevented by (A) Suitably designing the pump (B) Maintaining the suction head sufficiently greater than the vapour pressure (C) Maintaining suction head = developed head (D) Maintaining suction head lower than the vapour pressure

Description : Cavitation can be prevented by (A) Suitably designing the pump (B) Maintaining the suction head sufficiently greater than the vapour pressure (C) Maintaining suction head = developed head (D) Maintaining suction head lower than the vapour pressure

Last Answer : (B) Maintaining the suction head sufficiently greater than the vapour pressure

What type of pump may be appropriate for a liquid near saturation, a low flow rate, and very limited NPSHa (net positive suction head available)?

Description : What type of pump may be appropriate for a liquid near saturation, a low flow rate, and very limited NPSHa (net positive suction head available)?

Last Answer : This application is nearly perfect for a turbine regenerative type of pump. Factors that immediately identify your application and pump type are the small flowrate, low NPSHa, and high temperature. The ... in pressure. You can visit the site below to learn more about these types of pumps.

In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature. (A) Lower than (B) Higher than (C) Equal to (D) None of these

Description : In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature. (A) Lower than (B) Higher than (C) Equal to (D) None of these

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Foot valves are provided in the suction line of a centrifugal pump to (A) Avoid priming, every time we start the pump (B) Remove the contaminant present in the liquid (C) Minimise the fluctuation in discharge (D) Control the liquid discharge

Description : Foot valves are provided in the suction line of a centrifugal pump to (A) Avoid priming, every time we start the pump (B) Remove the contaminant present in the liquid (C) Minimise the fluctuation in discharge (D) Control the liquid discharge

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Conversion of dynamic velocity head into static pressure head in a centrifugal pump is the result of : (a) Increasing area of flow between adjacent vanes from inlet to outlet (b) Difference in pressure between suction and delivery ends (c) Radial thrust in pumps (d) Stuffing Box

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Last Answer : (b) Difference in pressure between suction and delivery ends

What you mean by cavitation and NPSH?

Description : What you mean by cavitation and NPSH?

Last Answer : Cavitation: Bubbles form in the liquids whenever there is pressure reduction inside the pump. These bubbles collapse when they approach high-pressure areas damaging pump internals. This is called the cavitation. ... . It is the head available at the eye of the impeller corrected to vapour pressure. 

Function of air vessel provided in a reciprocating pump is to (A) Reduce discharge fluctuation (B) Reduce the danger of cavitation (C) Avoid the necessity of priming (D) Increase the pump efficiency

Description : Function of air vessel provided in a reciprocating pump is to (A) Reduce discharge fluctuation (B) Reduce the danger of cavitation (C) Avoid the necessity of priming (D) Increase the pump efficiency

Last Answer : (A) Reduce discharge fluctuation

Consider a centrifugal pump having a specific impeller diameter, fixed impeller speed pumping a liquid of constant density at a particular discharge capacity. With decrease in the capacity of the pump, the __________ decreases. (A) NPSH required (B) BHP required by the pump (C) Head of the liquid pumped (D) All (A), (B) and (C)

Description : Consider a centrifugal pump having a specific impeller diameter, fixed impeller speed pumping a liquid of constant density at a particular discharge capacity. With decrease in the capacity of the pump, the __________ decreases. (A) ... the pump (C) Head of the liquid pumped (D) All (A), (B) and (C)

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Good design of the casing of a centrifugal pump aims at minimising the (A) Cavitation (B) Frictional losses (C) Kinetic energy loss (D) Static head

Description : Good design of the casing of a centrifugal pump aims at minimising the (A) Cavitation (B) Frictional losses (C) Kinetic energy loss (D) Static head

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Piezometric head is the sum of the __________ heads. (A) Elevation & kinetic energy (B) Elevation & pressure (C) Kinetic energy & pressure

Description : Piezometric head is the sum of the __________ heads. (A) Elevation & kinetic energy (B) Elevation & pressure (C) Kinetic energy & pressure

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Pick out the wrong statement: (A) Greater is the kinematic viscosity of the liquid, greater is the thickness of the boundary layer (B) Blowers develop a maximum pressure of 2 atmospheres (C) Friction losses in pipe fittings are generally expressed in terms of velocity heads (D) Fanning friction factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number

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In case of unsteady fluid flow, conditions & flow pattern change with the passage of time at a position in a flow situation. Which of the following is an example of unsteady flow? (A) Discharge of water by a centrifugal pump being run at a constant rpm (B) Water flow in the suction and discharge pipe of a reciprocating pump (C) Water discharge from a vertical vessel in which constant level is maintained (D) Low velocity flow of a highly viscous liquid through a hydraulically smooth pipe

Description : In case of unsteady fluid flow, conditions & flow pattern change with the passage of time at a position in a flow situation. Which of the following is an example of unsteady flow? (A) ... level is maintained (D) Low velocity flow of a highly viscous liquid through a hydraulically smooth pipe

Last Answer : (B) Water flow in the suction and discharge pipe of a reciprocating pump

The main draw-back of centrifugal pump, is (A) Necessity of priming (B) Discharge from pump varies with the load of water (C) For high heads, efficiency is low up to 50% (D) All the above

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Last Answer : (D) All the above

Priming in a distillation column (A) Results from very low gas velocity (B) Is desirable from point efficiency consideration (C) Is characterised by the presence of foam throughout the space between trays (D) Reduces the overall pressure drop

Description : Priming in a distillation column (A) Results from very low gas velocity (B) Is desirable from point efficiency consideration (C) Is characterised by the presence of foam throughout the space between trays (D) Reduces the overall pressure drop

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In fluid flow, cavitation is caused, if the (A) Fluid velocity decreases to zero (B) Total energy decreases (C) Both (A) and (B) (D) Flow pressure approaches its vapor pressure at the prevailing temperature

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Last Answer : (D) Flow pressure approaches its vapor pressure at the prevailing temperature

In centrifugal pumps, cavitation occurs, when pressure of the impeller eye or vane becomes (A) Less than atmospheric pressure (B) More than liquid vapor pressure (C) Less than liquid vapor pressure (D) More than atmospheric pressure

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Horsepower requirement for given pump capacity depends upon the (A) Specific gravity of the liquid (B) Suction lift (C) Discharge head (D) All (A), (B) and (C)

Description : Horsepower requirement for given pump capacity depends upon the (A) Specific gravity of the liquid (B) Suction lift (C) Discharge head (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Cavitation is caused by (A) High velocity (B) High pressure (C) Weak material (D) Low pressure

Description : Cavitation is caused by (A) High velocity (B) High pressure (C) Weak material (D) Low pressure

Last Answer : Answer: Option D

Which of the following is not a result of the excess of impurity in boiler-feed. a) Scale and sludge formation b) Decomposition c) Corrosion, priming and foaming d) Caustic embrittlement

Description : Which of the following is not a result of the excess of impurity in boiler-feed. a) Scale and sludge formation b) Decomposition c) Corrosion, priming and foaming d) Caustic embrittlement

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Cavitation will begin when (A) The pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid (B) Pressure becomes more than critical pressure (C) Flow is increased (D) Pressure is increased

Description : Cavitation will begin when (A) The pressure at any location reaches an absolute pressure equal to the saturated vapour pressure of the liquid (B) Pressure becomes more than critical pressure (C) Flow is increased (D) Pressure is increased

Last Answer : Answer: Option A

Assume that water vaporizes at an absolute pressure of 1.5 m, barometric pressure head is 9.5 m and cavitation coefficient is 0.1 A turbine operates under a head of 40 m. the safe height of the runner above the tail water level, in meters, is : a) 6 b) 4 c) 3 d) 2

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Last Answer : b) 4

Which of the following pairs are correctly matched? 1. Piezometric head : Sum of datum head and pressure head 2. Dynamic head : Sum of datum head and velocity head 3. Stagnation head : Sum of Piezometric head and velocity head 4. Total head : Sum of Piezometric head and dynamic head (a) 1, 2 & 3 only (b) 1, 3 & 4 only (c) 2, 3 & 4 only (d) 1, 2, 3 & 4

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Probability of cavitation occuring becomes very high, when the local __________ resulting in water bubbles formation, which on rupture cause cavitation (A) Pressure falls below the vapour pressure (B) Pressure becomes very high (C) Temperature becomes low (D) All 'a', 'b' & 'c'

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Last Answer : (D) All 'a', 'b' & 'c'

Self-priming centrifugal pump can be used for (A) Booster service (B) Pumping liquid fertilisers (e.g. liquid NH3 ) (C) Pumping industrial wastes (D) All (A), (B) and (C)

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. A special type of liquid transporting device is the diffuser pump, in which __________ are minimised. (A) Bearing losses (B) Disk friction (C) Shock losses (D) Cavitation

Description : . A special type of liquid transporting device is the diffuser pump, in which __________ are minimised. (A) Bearing losses (B) Disk friction (C) Shock losses (D) Cavitation

Last Answer : (C) Shock losses

The phenomenon occuring during pumping of a liquid solution containing dissolved gases, which may come out of the solution giving rise to gas pockets, is termed as (A) Evaporation (B) Cavitation (C) Sublimation (D) Stripping

Description : The phenomenon occuring during pumping of a liquid solution containing dissolved gases, which may come out of the solution giving rise to gas pockets, is termed as (A) Evaporation (B) Cavitation (C) Sublimation (D) Stripping

Last Answer : (B) Cavitation

The major reason of hydrodynamic noise (i.e., noise resulting from liquid flow) is (A) Pipe vibrations (B) Cavitation (C) Boundary layer separation (D) Fluctuation in liquid flow

Description : The major reason of hydrodynamic noise (i.e., noise resulting from liquid flow) is (A) Pipe vibrations (B) Cavitation (C) Boundary layer separation (D) Fluctuation in liquid flow

Last Answer : (B) Cavitation

Suction lift of a pump depends upon (A) Atmospheric pressure (B) Water temperature (C) Velocity of water in suction pipe (D) All the above

Description : Suction lift of a pump depends upon  (A) Atmospheric pressure  (B) Water temperature  (C) Velocity of water in suction pipe  (D) All the above 

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Last Answer : Answer: a, c, d Because most surgical infections are polymicrobial, specimens should be cultured for aerobic and anaerobic bacteria, as well as fungi. Although aerobic and aerotolerant ... fold increase over MIC during the peak serum level have been demonstrated to be clinically efficacious

Consider the following statements: The total head against which a pump has to work must include, besides any other items, 1. the suction lift. 2. the delivery head. 3. the head lost due to friction at entrance in the rising main. 4. the head lost due to friction at exit in the rising main. Which of these statements are correct? (a) 1, 2 & 3 only (b) 2 & 3 only (c) 1, 2, 3 & 4 (d) 3 & 4 only

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Last Answer : (c) 1, 2, 3 & 4

The formation of pockets of gas in a liquid is called: w) absorption x) cavitation y) adsorption z) dissolving

Description : The formation of pockets of gas in a liquid is called: w) absorption x) cavitation y) adsorption z) dissolving

Last Answer : ANSWER: X -- CAVITATION

Which of the following statement is wrong? (A) A flow whose streamline is represented by a curve is called two dimensional flow. (B) The total energy of a liquid particle is the sum of potential energy, kinetic energy and pressure energy. (C) The length of divergent portion in a Venturimeter is equal to the convergent portion. (D) A pitot tube is used to measure the velocity of flow at the required point in a pipe.

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With increase in pump speed, its NPSH requirement (A) Decreases (B) Increases (C) Remains unaltered (D) Can either increase or decrease; depends on other factors

Description : With increase in pump speed, its NPSH requirement (A) Decreases (B) Increases (C) Remains unaltered (D) Can either increase or decrease; depends on other factors

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Volute of a centrifugal pump should be designed in a fashion, such that the (A) Kinetic head gets converted into static head (B) Moving stream gradually reduces velocity (C) Mean velocity remains constant (D) None of these

Description : Volute of a centrifugal pump should be designed in a fashion, such that the (A) Kinetic head gets converted into static head (B) Moving stream gradually reduces velocity (C) Mean velocity remains constant (D) None of these

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Flow of air from one place to the other is caused due to (A) The sum of elevation (B) Pressure head (C) Velocity head (D) All of the above

Description : Flow of air from one place to the other is caused due to (A) The sum of elevation (B) Pressure head (C) Velocity head (D) All of the above

Last Answer : (D) All of the above

Buoyant force (A) For non-symmetrical bodies is not vertical (B) Depends on the depth of the submergence of the floating body (C) Depends on the weight of the floating body (D) None of these

Description : Buoyant force (A) For non-symmetrical bodies is not vertical (B) Depends on the depth of the submergence of the floating body (C) Depends on the weight of the floating body (D) None of these

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Foaming and priming in boiler operation can be reduced by reduction in __________ in feed water. (A) Turbidity (B) Color (Hazen) (C) Total solids (D) All (A), (B) & (C)

Description : Foaming and priming in boiler operation can be reduced by reduction in __________ in feed water. (A) Turbidity (B) Color (Hazen) (C) Total solids (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

Priming of a centrifugal pump is done to (A) Increase the mass flow rate of fluid (B) Develop effective pressure rise by the pump (C) Avoid chances of separation inside the impeller (D) None of these

Description : Priming of a centrifugal pump is done to (A) Increase the mass flow rate of fluid (B) Develop effective pressure rise by the pump (C) Avoid chances of separation inside the impeller (D) None of these

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Cavitation in a pump creates so many undesirable effects. Out of the following, which is not an undesirable effect created by cavitation? (A) Decrease in effect(B) Increase in thrust(C) Develops noise(D) Develops high pressure

Description : Cavitation in a pump creates so many undesirable effects. Out of the following, which is not an undesirable effect created by cavitation? (A) Decrease in effect (B) Increase in thrust (C) Develops noise (D) Develops high pressure

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Cavitation in a centrifugal pump can be avoided by keeping the (A) Inlet pressure high (B) Outlet pressure low (C) Inlet pressure low (D) Outlet pressure high

Description : Cavitation in a centrifugal pump can be avoided by keeping the (A) Inlet pressure high (B) Outlet pressure low (C) Inlet pressure low (D) Outlet pressure high

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