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单选题
Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.
A
positive displacement
B
ejector
C
centrifugal
D
air compressor
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更多 “单选题Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.A positive displacementB ejectorC centrifugalD air compressor” 相关考题
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Which of the following terms is used to identify the pressure of the liquid entering a pump?A.Suction headB.Pump headC.Discharge headD.Total head
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第二组Displacement pumps are those where the volume of the pump chamber is alternately increased to draw the liquid in from the suction pipe and then decreased to force the liquid out into the delivery pipe. Centrifugal pumps are those wherein an impeller rotating at high speed throws the liquid by centrifugal force from the center to the periphery of the impeller where the liquid is discharged through the delivery outlet.Gear pump consists of two or more meshing gears (spur, single or double helical teeth) enclosed m a close-fitted housing. These are used extensively for pumping fuel oil, lubricating oil and hydraulic oil. When gears are unmeshed on the inlet side, a pressure drop occurs that helps the atmospheric pressure acting on the surface of the oil in the reservoir to force it up the pipe to fill the void, the oil is then transferred around the periphery of the pump housing. As the gear teeth mesh again on the outlet side, they form. a seal that prevents oil from backing up to the inlet, the oil in the void is then be forced out into the discharge line.All vane pumps have a rotor driven within a ring (cam ring) by a drive shaft coupled to a prime mover. A cylindrical rotor with sliding vanes, generally in radial slots, rotates within the ring. The center of the rotor is offset from the center of the ring. In a simple vane pump, as the rotor turns, the vanes are forced outward against the inner surface of the cam ring by centrifugal force. This outward radial movement of the vanes and turning of the rotor causes the chamber between the vanes to increase as the vanes pass further away from the inlet port. This increase in volume results in a lowering of pressure until the atmospheric pressure is sufficient to force oil from the reservoir into the inlet chamber. Oil from the inlet is swept away by the vanes toward the outlet port through a decreasing series of chambers until it is forced through the outlet port. A vane pump of balanced design has an elliptical cam ring so that two pumping chambers are formed. This pump is in hydraulically balance, since the two intake and two outlet ports are diametrically opposed to each other. Therefore the side loads exerted on the rotor cancel out, thereby increasing bearing lift and permitting high operating pressure.According to the last sentence of paragraph 1, from where the liquid is discharged through the delivery outlet?A.from the eye of the impellerB.from passage of impellerC.from the periphery of the impellerD.from the impeller
考题
Which statement is NOT true?A.In a simple vane pump, the rotor and cam ring are exactly concentricB.Balanced vane pump has an elliptical cam ringC.Liquid in both gear pump and vane pump are forced out to the outlet.D.Balanced vane pumps can work at a higher pressure than the simple vane pump
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单选题A positive displacement pump is that where the volume of the pump chamber is alternately increased to （） and then decreased to （）.A
draw the liquid in；force the liquid outB
force the liquid out；draw the liquid inC
suction；drawD
deliver；outlet
考题
单选题The heat generated by a fire will be transferred through a bulkhead or dock, as a result of （）.A
conductionB
radiationC
convectionD
advection
考题
单选题Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?（）A
Oil is discharged from the impeller through the outletB
Gravity causes the oil to flow toward the dischargeC
The self-priming feature of the centrifugal pump enables it to draw its own suction as it startsD
The discharge capacity varies directly with the speed of the impeller
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单选题While flowing through the volute in a centrifugal pump, part of the （） energy of the liquid is converted to （） energy.A
kinetic；pressureB
kinetic；essentialC
pressure；kineticD
pressure；height
考题
单选题The function of a centrifugal pump double volute casing is to （）.A
reduce radial thrust to the impellerB
double the liquid velocity through the pump when compared to a single voluteC
reduce hydraulic end thrustD
provide the effect of multi-staging
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单选题A multistage centrifugal pump can be BEST described as having （）.A
two or more impellers housed together in one casing and mounted on a single shaftB
a single stepped impeller mounted in a progressively staged casingC
a large radial clearance between the impeller and casing to prevent overheating due toD
an increase in the discharge velocity of the liquid with a corresponding decrease in pressure through the stages
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单选题Which of the following statements about pump operations is NOT a correct statement?（）A
In order for a fluid to be pumped, a fluid must be made to flowB
A substance must be cold in order for it to be pumpedC
The kinetic energy imparted by the pump can be used to force a liquid through a hydraulic systemD
A pump must receive its energy from an external source
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单选题Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （） (1) reciprocating (2) rotary (3) centrifugalA
（1）onlyB
（1）and（2）C
（1），（2）and（3）D
（2）and（3）
考题
单选题Before liquid can flow into a pump, the air in the suction line must be （） sufficiently to cause the liquid to flow into the suction chamber.A
filledB
evacuatedC
compressedD
charged
考题
单选题The static suction lift of a pump is the difference in elevation between the （）.A
centerline of the pump and the level of the liquid in the suction well when the source of liquid is below the pumpB
centerline of the pump and the suction liquid level when the source of liquid is above the pumpC
centerline of the pump and the level of the discharge liquidD
liquid levels of the suction and discharge
考题
单选题If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.A
capacity will increaseB
capacity will decreaseC
suction pressure will increaseD
suction pressure will decrease
考题
单选题A pump is said to have "negative suction head" when the pump is located （）.A
between the suction and dischargeB
below the liquid supplyC
above the liquid supplyD
any of the above
考题
单选题A positive displacement pump is that where the volume of the pump chamber is alternately （） to draw the liquid in and then （） to force the liquid out.A
increased；decreasedB
decreased；increasedC
decreased；decreasedD
increased；increased
考题
单选题A pump is defined as device that（）A
produces pressureB
imparts energy to a fluid to move it from level ‘A’ to level ‘B’C
creates a vacuum to move a liquid in all installationD
is to develop a pressure differential
考题
单选题To absorb the wear resulting from impeller rotation and abrasives in the liquid, a centrifugal pump is usually fitted with （）.A
lantern ringsB
bearingsC
easing volutesD
wearing rings
考题
单选题If an emergency pump control is used as the emergency shutdown on a tank vessel，it must（）.A
stop the flow of oil at the main deck manifoldB
prevent the oil from leaving the shore facilityC
prevent the oil from siphoning through the pumpD
None of the above
考题
单选题The fuel is supplied to the pump through ports or openings in the （） or cylinder of the pump.A
bottleB
injectorC
pistonD
barrel
考题
单选题The basic function of the centrifugal pump impeller is to （）.A
directly increase the pressure of the liquid being pumpedB
directly increase the velocity of the liquid being pumpedC
convert the potential energy of the liquid to kinetic energyD
separate air from the liquid being pumped
考题
单选题“Flooding back” is a condition where the liquid refrigerant （）.A
vaporizes in the condenserB
reaches the compressor through the suction lineC
flashes in the liquid lineD
condenses in the receiver
考题
单选题If an emergency pump control is used as the emergency shutdown on a tanker，it must（）.A
stop the flow of oil at the main deck manifoldB
prevent the oil from leaving the shore facilityC
prevent the oil from siphoning through the pumpD
None of the above
考题
单选题A （） pump is that where the volume of the pump chamber is alternately increased to draw the liquid in and then decreased to force the liquid out.A
injectorB
positive displacementC
centrifugalD
centripetal
考题
单选题A centrifugal pump vibrates excessively during operationUpon disassembling the pump it is found that the impeller is out of balanceWithout an available spare, you should （）.A
drill holes through the heavy side of the impeller until it balancesB
weld counterweights to the light side of the impellerC
remove metal from the heavy side by machining in a latheD
acid wash and serape the heavy side until it balances
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