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单选题
Low pressure air is usually taken through （） or pressure regulators to a low pressure reservoir supplying a ring main through driers.
A
globe valves
B
butterfly valves
C
gate valves
D
reducing valves
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更多 “单选题Low pressure air is usually taken through （） or pressure regulators to a low pressure reservoir supplying a ring main through driers.A globe valvesB butterfly valvesC gate valvesD reducing valves” 相关考题
考题
Forces other than damaging winds are also at work inside tornadoes (龙卷风) . Sometimes,as the wind passes a house, the walls and ceiling burst apart as if a bomb had gone off inside. This explosion is caused by the low air pressure at the center of a tornado.The pressure at the center of a tornado is usually 13 pounds per square inch. However,inside the house the air pressure is normal, about 15 pounds per square inch.The difference of 2 pounds per square inch between the inside and outside pressure may not seem like much. But suppose a tornado passes over a small building that measures 20 by 10 by feet. On each square inch of the building, there is 2 pounds of pressure from the insidethat is not balanced by air pressure outside the building. On the ceiling, that adds up to an unbalanced pressure of 57600 pounds. The pressure of the four walls adds up to 172800 pounds.If windows are open in the building, some of the inside air will rush out through them.This will balance the pressure inside and outside the building.But if the windows are shut tightly, the huge inside pressure may cause the building to burst.Unfortunately, heavy rain often occurs in the storms that later produce tornadoes,so people often shut their windows. This may cause far worse damage later.21、 What did the paragraph before this passage most probably discuss?A、 Measuring rainfall from a stormB、 The kinds of damage caused by explosionsC、 The powerful winds of tornadoes22、 Which of the following is the main topic of the passage?A、 How tornadoes can be preventedB、 When tornadoes usually occurC、 Why tornadoes cause so much damage23、 Tornadoes can destroy buildings because the()A、 force of a tornado increases the air pressure in a buildingB、 air pressure inside a tornado is less than the air pressure inside a buildingC、 air pressure at the center of a tornado is over 172000 pounds24、 What is the difference per square inch between the air pressure inside a building and the air pressure inside a tornado?A、 2 poundsB、 13 poundsC、 15 pounds25、 What would happen if the windows are shut tightly in the stormy weather?A、 Tornadoes may be formedB、 The house may be apartC、 There may not be any pressure inside the building
考题
When adding oil to a refrigeration system, precautions must be taken to ensure thatA.the compressor suction pressure is not too highB.all air is purged from the pump and charging fittingsC.the high pressure cutout switch is held open to prevent accidental startingD.the condenser is completely shutdown first
考题
A barometer showing falling pressure indicates the approach of a ______.A.high pressure systemB.low pressure systemC.high dew pointD.low dew point
考题
A low in a marine weather report is an air pressure system the pressure at the center of which is ______.A.the highest over the areaB.the lowest over the areaC.higher than 1013 HPAD.lower than 1013 HPA
考题
Good weather is usually associated with a region of ______.A.low barometric pressureB.high barometric pressureC.falling barometric pressureD.pumping barometric pressure
考题
单选题The fresh air coming in through the inner air ports, is compressed by（） to a higher pressure.A
the cylinder headB
the cross-headC
the moving pistonD
the stationary piston
考题
单选题Which of the listed problems can be a cause of low compression pressure in a diesel engine?（）A
clogged air filterB
compression strokeC
burned exhaust valvesD
all of the above
考题
单选题When adding oil to a refrigeration system, precautions must be taken to ensure that （）.A
the compressor suction pressure is not too highB
all air is purged from the pump and charging fittingsC
the high pressure cutout switch is held open to prevent accidental startingD
the condenser is completely shutdown first
考题
单选题In an air conditioning system, low head pressure associated with a reciprocating compressor can be the result of （）A
broken valve springsB
tight drive beltsC
high line voltageD
air in the system
考题
单选题Two well-developed high pressure areas may be separated by a（）.A
Hill of low pressureB
Trough of low pressureC
Valley of low pressureD
Ridge of low pressure
考题
单选题Compared to a low pressure system，generally the air in a high is（）.A
warmer，less dense，and less stableB
cool，more dense，and drierC
muggy and cloudyD
extremely moist with high relative humidity
考题
单选题Which of the following methods is used to prevent throttling of compressed air through the diesel engine air starting valves?（）A
Holding the valve open for a long periodB
Increasing the starting air pressure usedC
Opening the stating air valve quicklyD
Reducing the starting air valve size
考题
单选题Cast irons weakness in tension and under shock loading limits its use to low pressure steam, air, oil and low speed water fittingsThe above sentence, most probably means （）.A
cast iron has weaknessB
cast iron can stand up shock loadingC
cast iron fittings are only suitable in low pressure situationD
east iron fittings are not suitable in low pressure situation
考题
单选题The loss of the diesel engine cylinder air charge through leaky valves, piston rings, worn or scored liners, would be indicated by which of the following sets of conditions?（）A
Low compression pressure and high exhaust temperatureB
Low firing pressure and high exhaust temperatureC
Low compression pressure and low exhaust temperatureD
Low firing pressure and low exhaust temperature
考题
单选题On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.A
splash methodB
mechanical force feed lubricatorsC
detached sump methodD
internal cooling passages in the crankshafts and connecting rods
考题
单选题An air mass is termed warm if（）.A
it is above 70°FB
the ground over which it moves is cooler than the airC
it originated in a high pressure areaD
it originated in a low pressure area
考题
单选题Broken valve strips in an operating low pressure, air compressor will cause （）.A
an immediate crankcase explosionB
oil contamination in the compressed airC
a decrease in compressor capacityD
no immediate loss of the compressed air capacity
考题
单选题Each cylinder has one starting valve which is usually opened by air pressure and closed by （）A
nuts and boltsB
new jointsC
spring forceD
sealing rings
考题
单选题The direction of the surface wind is（）.A
directly from high pressure toward low pressureB
directly from low pressure toward high pressureC
from high pressure toward low pressure deflected by the earth's rotationD
from low pressure toward high pressure deflected by the earth's rotation
考题
单选题The pressure of pilot air is usually （） than that of starting air.A
higherB
lowerC
lowD
high
考题
单选题The greater the pressure difference between a high and a low pressure center，the（）.A
dryer the air mass will beB
cooler the temperature will beC
greater the force of the wind will beD
warmer the temperature will be
考题
单选题The diurnal variation of pressure is most noticeable（）.A
above the polar circlesB
in a low pressure areaC
during periods of low temperaturesD
in the doldrums
考题
单选题麻醉机APL阀的意义（）。A
APL是auto pressure lock的简写B
APL是adjustabLe pressure limiting的简写C
APL是air pressure lock的简写D
APL是air pressure lift的简写E
APL是auto pressure lift的简写
考题
单选题An un-loader is installed on an air compressor to （）.A
bypass the high pressure stage to the low pressure stage on 100% of the air compressors in serviceB
prevent excessive inter-stage pressure buildupC
control compressor discharge pressureD
remove all but the frictional load during starting
考题
单选题Bad valves operation of the reciprocating air compressors can be detected by observation of （）.A
the discharge temperature lowB
the discharge temperature highC
the discharge pressure riseD
the inter-stage pressure low
考题
单选题An indication of a diesel engine air intake being partially clogged, is （）.A
low firing pressure and low exhaust temperaturesB
low firing pressure and normal exhaust temperaturesC
high firing pressure and low exhaust temperaturesD
high firing pressure and high exhaust temperatures
考题
单选题Excessively low air pressure occurring in the intercooler of a reciprocating air compressor is caused by（）.A
leaky discharge valves on the LP cylinderB
leaky discharge valves on the HP cylinderC
insufficient intercooler coolingD
low ambient air pressure
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