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单选题
Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）
A
The pump delivers full capacity when started, but gradually slackens off toan abnormally low flow
B
The pump packing gland overheats after short operating periods
C
The motor over-current protective device continually shuts the pump down
D
Pounding noises can be heard at the pump suction chest
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更多 “单选题Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）A The pump delivers full capacity when started, but gradually slackens off toan abnormally low flowB The pump packing gland overheats after short operating periodsC The motor over-current protective device continually shuts the pump downD Pounding noises can be heard at the pump suction chest” 相关考题
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If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at theA.fuel line connections to the cylinder injection valvesB.gasket surfaces of the fuel oil filtersC.discharge fittings of the fuel injector pumpsD.suction side of the fuel oil transfer pump
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The main propulsion diesel engine jacket water temperature rises above normal, with the raw sea suction and the expansion tank water level being normal. Which of the following problems is most likely the cause?A.Faulty thermostatic bypass valveB.Eroded zinc pencils in the heat exchangerC.Steam formation in the expansion tankD.Excessive leakage from jacket water pump seals
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To add refrigerant to the low side of an air conditioning system, the refrigerant should be introduced through the_______ .A.suction service valve as a vaporB.suction service valve as a liquidC.discharge service valve as a vaporD.charging valve as a liquid
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If a centrifugal pump is driven by a constant speed electric motor and produces a discharge pressure less than designed, the cause is probably ______.A.excessive pump speedB.excessive suction headC.worn wearing ringsD.gross pump misalignment
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An increase in the heat load to a refrigeration system will cause ______.A.the suction pressure to decreaseB.the suction temperature to increaseC.increased ice formation on the evaporator coilD.excessive short cycling of the compressor
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单选题Excessive lube oil consumption by a reciprocating air compressor can be caused by （）.A
using a slightly dirty air filterB
using oil having an excessive viscosityC
intercooler or after-cooler leaksD
carrying the oil level higher than normal
考题
单选题What is a function of the wearing rings used in most centrifugal pumps?（）A
Absorb erosion of high velocity discharge streamB
Seal pump shaft against entry of airC
Isolate the discharge side from the suction sideD
Dampen the turbulent discharge flow
考题
单选题A double suction centrifugal pump impeller has been installed in the reverse direction, and will （）.A
have a greater head capacityB
operate with increased impeller efficiencyC
discharge through the suction side of the pump casingD
require more power to run the shaft
考题
单选题Reduced capacity, accompanied by vibration and noise at the suction of a centrifugal pump is a result of （）.A
cavitationB
water hammerC
fluid frictionD
steam knock
考题
单选题Where is the cooling water from the compensating tank in the cooling water system of main engine lead to?（）A
discharge side of the centrifugal pumpB
suction side of the centrifugal pumpC
the lowest point of the cooling water systemD
inlet of the main engine
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Where are the zinc plates located?（）A
saltwater side of the condenserB
refrigerant side of the condenserC
in the evaporator coilsD
in the suction strainer
考题
单选题Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.A
cavitationB
electrolysisC
abrasionD
corrosion
考题
单选题Increasing the speed of a centrifugal pump will result in an increase in its capacity Another means of increasing the capacity of a centrifugal pump is to increase the （）.A
diameter of the discharge piping, with all other factors remaining the sameB
diameter of the suction piping, with all other factors remaining the sameC
width of the impeller onlyD
diameter of the impeller
考题
单选题All of the following steps are taken in starting a centrifugal pump，EXCEPT to（）.A
set the relief valveB
check the lubrication systemC
vent the pump casingD
open the pump suction and discharge valves
考题
单选题The usual symptoms of cavitation in a centrifugal pump is （）.A
noise and vibrationB
an increase in discharge pressureC
an increase in suction pressureD
lifting of the relief valve
考题
单选题To operate a centrifugal fire pump at reduced capacity, you should （）.A
readjust the relief valveB
throttle the suction lineC
throttle the discharge valveD
open the priming line
考题
单选题An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.A
oil foaming in the compressorB
higher than normal suction and discharge pressures with a higher box temperatureC
higher than normal discharge pressure with a normal box temperatureD
the compressor to run continuously
考题
单选题In order to properly remove air from the casing of a centrifugal pump when starting, the pump should have a （）.A
positive headB
negative suction headC
mechanical sealD
vent valve attached to the casing at the top of the volute
考题
单选题Operating a rotary pump at speeds in excess of design requirements could cause（）.A
decreased clearances between rotating partsB
decreased slippage to the suction side of the pumpC
air binding in the discharge portsD
erosion and excessive wear
考题
单选题When installed for bilge pumping or ballast duty, centrifugal pumps require a （） to remove air from the suction pipe.A
air chamberB
head lankC
primerD
prime mover
考题
单选题Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）A
The pump delivers full capacity when started, but gradually slackens off toan abnormally low flowB
The pump packing gland overheats after short operating periodsC
The motor over-current protective device continually shuts the pump downD
Pounding noises can be heard at the pump suction chest
考题
单选题Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be （）.A
one size smaller than the pump suction nozzleB
the same size as the pump suction nozzleC
one size larger than the pump suction nozzleD
installed with a short radius elbow at the pump
考题
单选题Air leakage between the shaft and stuffing box packing in a centrifugal pump is prevented by （）.A
a compressed packing glandB
lantern tings between the packing ringsC
a liquid sealD
the stuffing box gland
考题
单选题The sensing line for the low pressure cutout switch to a refrigeration system is located （）.A
in the chill boxB
before the receiverC
on the suction side of the compressorD
on the discharge side of the compressor
考题
单选题To thoroughly pump out the bilges using a horizontally mounted centrifugal pump, the （）.A
pump must always be primedB
volute must impart a radial and rotary motion of the water suction sideC
connection must guide the liquid to the lantern ringsD
stuffing box should not be allowed any water leakage
考题
单选题If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at the （）A
fuel line connections to cylinder injection valvesB
gasket surfaces of the fuel oil filtersC
discharge fitting of the fuel injector pumpsD
suction side of the fuel oil tran
考题
单选题In the suction stroke air is induced into the cylinder （）In the compression stroke the air is compressed.A
by an fuel valveB
through an inlet valveC
with an exhaust valveD
from an outlet valve
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