A
THE HONGKONG GOVERNMENT GAZETTE, MARCH 11, 1910.
145
207.
In an engine with three cranks, which of the three is subject to the greatest torsional stress (1) in going ahead (2) in going astern?
208.
Is it usual to make the crank shaft of a triple or quadruple expansion engine in one piece ?
And is the diameter of the shaft uniform from end to end? Give your reasons for the practice which obtains
In a of shaft?
209.
"built” crank shaft how are the webs rigidly secured to the pins and to the body
210.
There are various descriptions of donkey engines in use on board ship for pumping purposes. Some pumps are fitted with escape-valves, some are not. Why should this be?
211.
Make rough hand
Explain the function of an air-vessel fitted to a feed pump. sketches of (1) a satisfactory vessel, (2) an unsatisfactory vessel, where, say, the air-spring has been destroyed by carelessness, or has never been properly provided.
212.
Should cocks or escape-valves be fitted to air-vessels? Why, or why not?
213.
Where, by preference, should the escape-valve of a feed pump be placed? Why?
214.
Scum cocks are sometimes fitted to boiler-shells at a height convenient for Engineers to manipulate when standing in the stokehold; the scum pipes in such cases are led upward, inside the boiler, to a little above the combustion chamber tops. What danger may arise from this arrangement?
215.
Cocks for testing the water level of boilers are sometimes fitted within reach of the Engineer who is standing in the stokehold. These may have internal pipes leading upward and terminating at various levels. Under what circumstances may these become misleading?
216.
Why should the pipe which leads from the bottom of the water-gauge column to the bottom of the boiler-front, or back, be covered with non-conducting material? Why also should it never have lengthy horizontal bends?
217.
In your own experience, how frequently is this pipe removed and cleared ?
218.
Why, even with the best of water-gauges, is it advisable to occasionally use the drain- cock ?
219.
Steam loops have sometimes been inadvertently made in the length of piping leading from the top of the water-gauge column to the top of the boiler. Roughly sketch such a loop and explain the danger arising from its existence.
220.
Describe your method of thoroughly testing the water-gauge system to satisfy yourself that all the cocks and pipes are clear. Your answer can be written on a supplementary sheet of foolscap, which the Examiner will hand you. Hand sketches, mere lines indicating pipes, and circles indicating cocks, should be made. Identify the cocks and pipes by letters or numerals.
221.
Describe the construction of a water-tube boiler, mentioning the type selected.
222.
In a water-tube boiler, how is an economiser fitted, and what is its duty ?
223.
How is the water-gauge fitted? Are glass-gauges used?
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