Stationary Engineering Exam Questions with Complete Solutions

Stationary Engineering Exam Questions with Complete Solutions What are drum internals? - CORRECT ANSWER Drums internals comprise all apparatus with in a drum, including all baffles that quiet or separate the steam and water, the various devices that may be used for affecting the separation of the steam and water, and the various chemical and feed water admissions piping and blow down lines What do scrubbers remove? - CORRECT ANSWER They remove the entrained moisture in the steam. The scrubber is not highly effective in removing small amounts of fine steam mist, but it suffices to eliminate most of the usual spray and splatter as well as to break up and eliminate any dry foam After passing through a washer, the moisture droplets in the steam are enlarged. This increases the effectiveness of the scrubber and helps reduce the carry-over. Explain how a scrubber works? - CORRECT ANSWER The steam passed between closely fitted corrugated plates or screens on which the mists are deposited in an action comparable to filtration. The velocity is low to avoid re-entrainment. The collected water is dripped by gravity to the boiler water below. The efficiency of the scrubber depends upon the following variables. a. Surface area b. Low steam velocity c. Steam passage irregularities d. Time of contact Name different types of water walls - CORRECT ANSWER Bare-Plate Walls- All internally fired, portable or integral fire box boilers, such as scotch marine or locomotive boilers. Bare-Tube Wall- They may be constructed of plain tubes, fin tubes or studded tubes, with a firebrick or refractory backing. Covered-Tubed Walls- Consist of tubes protected either by integral blocks or attached blocks. Blocks may be integral blocks of metal or attached blocks of metal, refractory or metal-enclosed refractory. The purpose of the protection is to eliminate erosion and corrosion by the combustion products of waste heat, assist combustion, prevent escape of molten slag and provide a chill for a moving fuel bed What types of valves are found on a water wall header? - CORRECT ANSWER Blow-off connections are provided in each of the lower water wall headers for the removal of sludge. Care must be taken in making use of these blow downs. To avoid upsetting the circulation of water in the water wall, the water wall should never be blown down while the boiler is steaming. What is a forced circulation boiler? - CORRECT ANSWER Forced circulation is what makes controlled circulation possible. In the C & E design it involves the use of a pump or pumps to force water through all the steam-generating circuits. Thus insuring a positive flow in one direction at all times, regardless of the rate of heat application.