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
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