单项选择题
A.too little seal water
B.improper gravity disc
C.oil discharging pump not working very well
D.low water level of the working water
单项选择题 When separating fuel oil in oil separator, the separating quantity is（） of the real quantity.
单项选择题 When separating lube oil separator, the optimal separating quantity is（）of the rated quantity on name plate.
单项选择题 One of the reasons that cause oil flowed from sludge outlet of a self-cleaning separator is（）