Second: In seeing to it that in apparatus provided with an overflow leading to the ash-pit, the water should flow constantly but without exceeding the proper amount.
Third: In keeping down temperature in the scrubber by properly regulating the feed of the wash-water. This apparatus may be slightly warm at its lower part, but must be quite cold at the top.
The manual tending to be done is limited to the regular filling up of the generator with fuel and to the removal of ashes and clinkers. The charging is effected at regular intervals, which, according to the various types of anthracite-generators, vary from one to six hours. Charging the apparatus at short intervals entails unnecessary labor, while charging at too long intervals will often interfere with the uniform production of the gas.
It will be obvious that the amount of fuel introduced will be the larger, the greater the intervals between two fillings. This fuel is cold and contains between its particles a certain amount of air; furthermore, the layer of coal which covers the incandescent zone has become relatively thin. The excess of air impoverishes the gas, and the fresh fuel lowers the temperature of the mass undergoing combustion, so that again the gas in process of formation is weakened. Experience seems to show that as a rule it is best to fill up the generator at intervals of from two to three hours, according to the work done by the engine. It should be noted that the level of the fuel in the generator should not sink below the bottom of the feed-hopper.
The author wishes again to emphasize that in order to prevent the harmful entrance of air, the charging operations should be carried out as quickly as possible; and for this reason the fuel should be introduced not by means of the shovel, but by means of a pail, scuttle, or other appropriate receptacle.
Care should be taken to fill the charging box to its
upper edge and to adjust its cover accurately before operating the device which closes the feed-hopper (valve, cock).
The removal of the ashes and clinkers should be accomplished as infrequently as possible, since opening the doors of the ash-pit and of the combustion-chamber necessarily causes an inward suction of cold air which is harmful.
As a rule with generators employing anthracite coal, it is sufficient to empty the ash-pit twice daily; this should be preferably done during stoppages. However, the cleaning of the grate by means of a poker passed between the grate-bars or over them in order to bring about the falling of the ashes, should be attended to every two to four hours, according to the type of the generator and the nature of the fuel. In order that this cleaning may be done without opening the doors, the latter should be provided with apertures having closing devices.
This cleaning has for its chief object to allow the free passage of the air for supporting combustion and to keep the incandescent zone in the apparatus at the proper height. The accumulation of ashes and clinkers at the bottom of the retort will shift this zone upward and impair the quality of gas.