Absa: 4th Class Part B - Comprehensive Exam 4

An engine that has one power stroke every second rotation of the crankshaft is a: Select one: a. two-stroke diesel engine b. four-stroke natural gas engine c. two-stroke gasoline engine d. double-acting engine {Ans: b}What is the purpose of the high limit control on a hot water boiler? Select one: a. To shut down the burner if the water temperature exceeds 121 degrees Celsius. b. To stop the boiler if the water level control fails. c. To act as a emergency stop for the operator d. To prevent the boiler pressure from rising above 1100 kPa gauge. {Ans: a}Air washers can achieve dehumidification when Select one: a. the return air is more humid than the outside air. b. the specific humidity of the air is greater than the relative humidity. c. the spray water is cooled to below the dew point. d. the water temperature is greater than the dry bulb temperature. {Ans: c}A water sample taken from the service outlet of an ion-exchange softener shows 20 ppm hardness. The operator should: Select one: a. Regenerate the softener. b. Add salt to the brine tank. c. Backwash the softener. d. Rinse the softener. {Ans: a}When starting