单项选择题 As for a oil-fired boiler too much air would indicated by （）.

单项选择题 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

单项选择题 The amount of heat released by steam when it changes to water at the same temperature is called（）.