DIFFICULTIES OF PURIFYING WATER FOR LOCOMOTIVES.
The nostrums offered to railroad managers for purifying feed-water are legion, but it is doubtful if a single remedy has proved entirely successful. In most instances, the material or means used have been worthless or impracticable; but, in other cases, the appliances have not received justice from those attending their application. Most people underrate the magnitude of the task involved in undertaking to render the impurities of feed-water innocent in locomotive boilers. The case of a learned professor who undertook to doctor the feed-water for locomotives on a prominent road, where he made his arrangements for each engine using one thousand gallons of water a day, is representative. When provision has to be made for some engines using double that quantity each hour, the difficulty of the transaction becomes apparent. As has already been said, I believe that obtaining soft surface-water is the proper way to avoid trouble with locomotive boilers; but, where this is impracticable, considerable saving can be effected by “doctoring” the water if the operations are intelligently conducted.
MUD.
Mud is the most universal impurity of feed-water; and, in many cases, it causes the destruction or injury of sheets, particularly the crown-sheets of fire-boxes. Where the water of a road is habitually muddy, it would pay to filter the water, or to have two tanks at each water station, so that a system could be followed of letting the water settle in one tank while the other was in use. The settled mud, by this means, could be washed out regularly before a tank were refilled.
CARBONATE OF LIME.
Dr. Clark, inventor of the soap-test, recommended a method of purifying water containing carbonate of lime, which has been successfully followed in many places, especially in England. It consists of adding caustic lime to water containing carbonate of lime. By this process, 28 grains of caustic lime result in the precipitation of 100 grains of lime carbonate. Or, to put it in a practical shape, where a tank contains 30,000 gallons of water, each gallon being impregnated with 30 grains of lime carbonate, 36 pounds of caustic lime will be sufficient to precipitate the whole of the impurity, making a total deposit of 164 pounds.
SULPHATE OF LIME.
Where the water impurity is principally sulphate of lime, the caustic lime remedy will not work; but a precipitate of the objectionable compound can be made by treating the water with caustic baryta or caustic soda. In the first case, the baryta takes possession of the sulphuric acid holding the lime in solution, allowing the latter to fall down as mud: when the soda cure is applied, the sulphuric acid deserts the lime, and combines with the soda, for which it has greater affinity, leaving the lime to precipitate, unless it be preserved in solution by the carbonic acid that accompanied the soda.
Where the water contains a mixture of lime sulphate and carbonate, the soda treatment may be advantageously used in combination with the caustic lime system.
Attempts have frequently been made to purify water by putting chemicals into the locomotive tenders, the impurity being precipitated in the boiler. The leading objection to this system is, that it leads to enormous quantities of sediment being deposited inside the boiler; since, in some instances, the purifying substance is as bulky as the original impurity. In other cases, the chemical introduced into the boiler causes foaming. Let us take the case of water that contains fifteen grains of sulphate of lime to the gallon, and is treated with sulphate of baryta. To do so properly, one grain of the chemical will be required for each grain of lime. A freight engine uses seventy-five gallons of water to the mile, and runs one hundred miles a day. This is light service, both for water and mileage; yet, within ten days, nearly three hundred pounds of solid matter is injected into the boiler. To purify water by injecting chemicals into locomotive boilers, and prevent the boiler filling up rapidly with mud, or giving trouble from foaming, the blow-off cock and surface cock must be used so frequently as to be felt on the consumption of coal. Where purifying of feed-water must be done, the right place to carry on the process is in the station tanks, or in special appliances beside them. By carefully watching the character of the impurities in the water, and treating them with their proper precipitants, labor and expense devoted to the purification of feed-water may bring in good returns: where attempts are made to improve the water over a whole road by one method of treatment, failure is certain.