Which of the following may hardness of the boiler water cause?（）
(1) scale formation
(2) tube failure
(3) corrosion
A.（1）and（2）
B.（1）and（3）
C.（2）and（3）
D.（1），（2）and（3）
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A.higher than the actual drum water level
B.equal to the actual drum water level
C.increasing due to steam condensation in the glass
D.lower than actual drum water level
A.no combustion
B.deposits in the fuel
C.excessive air in the fuel
D.cold fuel oil
A.swell
B.shrinkage
C.flash off
D.lack of water
A.Water Head Register
B.Water Heater Re-circulating
C.Waste Heat Recovery
D.Waste Handle Reference
A.yellowish flame
B.golden yellow flame
C.milky flame
D.brilliant white flame
As for an oil-fired boiler if at a normal steaming condition and water goes out of sight in gauge glasses the action you should take is: （）
(1) secure oil to fires
(2) increase feed pump pressure
A.（1）
B.（1）and（2）
C.（2）
D.neither（1）nor（2）
A.latent heat of condensation
B.latent heat of vaporization
C.latent heat of saturation
D.sensible heat of condensation
A.physical state
B.temperature
C.atmospheric pressure
D.sensible pressure
A.The blow down valve
B.The scum valve
C.The air release cock
D.The soot-blower
A.an diesel oil heater
B.a waste heat boiler
C.a fresh water generator
D.all the above
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The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
The general purpose of a heat exchanger is to （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
A salinity indicator is used to determine the （）.
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
A pressure drop through the refrigerant liquid line may cause （）.