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单选题
Impurities from the boiler water surface can be removed through the （）.
A
safety valve
B
blow down valve
C
scum valve
D
feed check valve
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In a()boiler the hot gases from the furnace pass gases from the furnace pass water is on the outside.
A.water-tubeB.fire-tubeC.exhaust gasD.composite
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In a ______boiler the hot gases from the furnace pass through the tubes while the water is on the outside.A.water-tubeB.fire-tubeC.exhaust gasD.Composite
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The boiler water alkalinity in a coil-type auxiliary boiler should be maintained at the pH recommended by the boiler manufacturer to______.A.precipitate(使沉淀) silica （硅石）from solutionB.reduce corrosion in the heating coilC.prevent clogging and erosion in the coilD.maintain zero water hardness
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The separation of impurities and water from ______is essential for good combustion of diesel engines.A.lube oilB.fuel oilC.turbine oilD.grease
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共用题干
第一篇Water Resources on the EarthThe second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.Liquid water only exists________.A: in the center of the earthB:on the surface of our planetC:in the coastal areas of the earthD:in a very narrow range of temperatures
考题
单选题The concentration of total dissolved solids in the water of an auxiliary boiler can increase as a result of （）.A
seawater contaminationB
frequent surface blowsC
dissolved oxygen deaerationD
frequent bottom blows
考题
单选题A shallow dish positioned at the normal water level is connected to the（）This enables the blowing down or removal of scum and impurities from the water surface.A
main stern stop valveB
auxiliary steam stop valveC
scum valveD
blow down valve
考题
单选题The water level of an exhaust gas boiler which is independent of the auxiliary boiler and just as the extra heating surface of it （）A
will be modulated in proportionB
will be modulated in proportion and integralC
will be modulated in proportion and differentialD
will not be modulated at all
考题
单选题What is NOT a function of the steam drum of a marine water-tube boiler（）.A
Receives saturated steam from the generating tubesB
Serves as a reservoir of boiler feed waterC
Holds internal fittings for separation of moisture from steamD
Collects steam exhausted from the turbines
考题
单选题Black smoke coming from a boiler can be caused by （）.A
low water levelB
high water levelC
excessively high fuel pressureD
low oil temperature
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单选题Due to excessive water in the fuel, a diesel engine fails to startBefore the engine can be started, the water must be removed from the （）.A
fuel pumpsB
cylindersC
fuel strainersD
all of above
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单选题The rate of heat transfer in a water-tube auxiliary boiler can be increased by （）.A
operating the boiler at less than normal water levelB
installing fins on the firesides of water-tubesC
increasing the amount of excess air to the burnersD
treating the boiler water with chemical oxygen scavengers
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单选题In readying an auxiliary water-tube boiler for a routine hydrostatic test, which of the following procedures should be undertaken prior to filling the boiler with fresh water?（）A
The safety valve escape piping should be disconnected from the valve body and a blank insertedB
The boiler vent valves should be openedC
All handhole/manhole covers should be tightened up as much as possible to preclude any leaksD
All of the above
考题
单选题Moisture is removed from a refrigeration system by（）.A
bleeding refrigerant from the condenserB
opening a drain petcock on the oil separatorC
condensing the water in the heat exchangerD
using a dehydrator cartridge
考题
单选题Bottom blow valves are installed on auxiliary water-tube boilers to （）A
remove suspended and precipitated solids from the boiler waterB
completely drain the boiler in an emergency situationC
prevent hardened scale deposits in the water drumD
remove floating impurities from the oily water surface
考题
单选题A diesel engine fails to start due to excessive water in the fuelBefore the engine can be started, the water should be removed from the（）A
fuel linesB
lube oil filterC
crank case pumpD
rocker arm reservoir
考题
单选题The emulsion of the oil is mainly caused by （）.A
the solid impurities of large particleB
the solid impurities of fine particleC
the water contentD
both water and solid impurities
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单选题The separation of impurities and water from （） is essential for good combustion of diesel engines.A
lube oilB
fuel oilC
turbine oilD
grease
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单选题A centrifuge arranged to separate impurities and small amounts of water from oil is known as （）.A
an oily water separatorB
a purifierC
a centrifugal compressorD
a clarifier
考题
单选题Water level controllers of the boiler must be kept operable to protect external steam-using plant from water “（）” danger.A
carry offB
carry downC
carry onD
carry over
考题
单选题The boiler water alkalinity in a coil-type auxiliary boiler should be maintained at the pH recommended by the boiler manufacturer to（）A
precipitate silica from solutionB
reduce corrosion in the heating coilC
prevent clogging and erosion in the coilD
maintain zero water hardness
考题
单选题Excessive alkalinity of the water in an auxiliary boiler can cause （）.A
caustic embrittlement of the boiler metalB
acidic corrosion of the boiler metalC
hard scale deposits on the boiler tubesD
etching of the heat exchange surfaces
考题
单选题Bottom blow valves are installed on auxiliary water-tube boilers to （）A
completely drain the boiler in an emergencyB
prevent sludge from forming in the drumC
remove floating impurities from the boiler water surfaceD
remove settled solids from the water drum
考题
单选题Black smoke coming from a boiler can be caused by （）.A
low water levelB
low oil pressureC
excessively high fuel pressureD
an improper air/fuel ratio
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