BOILERS AND GENERATION OF STEAM 327 



20. Describe an injector. State the principle on which it works. 



21. Describe a water injector. 



22. Describe a water heater. 



23. What is a damper regulator? 



24. Why is it necessary to clean a boiler? How is it cleaned? 



25. Describe the steps in starting a fire in a new boiler. 



26. Describe the steps in firing a boiler. 



27. What is a chimney? 



28. Explain the theory of combustion and smoke. 



29. Define the following terms : saturated steam ; wet stearn ; dry 

 steam; supersaturated steam; heating surface of a boiler; horse- 

 power of a boiler ; priming. 



