为了防止因积灰而造成堵塞，焦炉斜道的倾斜角应小于（）度。
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为提高炉头温度，进入炉头的空气过剩系数应为（）
A. 1.25
B. 1.15
C. 1.3以上
D. 1.15以下
（）aremountedinpairstoprotecttheboileragainstoverpressure.
A. Safetyvalves
B. Watertubes
C. Steamstopvalves
D. Blowdownvalves
Chainslingsaresuitableforheavyslenderarticles，suchas（）.
A. timberorsteelrails
B. locomotivesorboilers
C. railwaypassengercoaches
D. motorvehicles
Whensteamisbeingraisedonaboiler,thewaterlevelwillnormally（）.
A. dropastheboilerwarmsup
B. riseastheboilerwarmsup
C. remainunchangeduntiltheboilerishotenough
D. riseandfallwiththesteamdemand
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