单项选择题
A.bypass exhaust gas at high loads to prevent excessive back pressure
B.bypass a portion of the exhaust gas at peak loads for better efficiency
C.recycle exhaust gas to the turbocharger
D.minimize moisture condensation in the boiler gas passages at low loads
单项选择题 Which of the following actions should be taken if during a routine maintenance inspection of a centrifugal pump, localized scoring on a pump shaft sleeve is detected?（）
单项选择题 Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service?（）
单项选择题 For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should remain constant regardless of load changes?（）