Both the tank and the cooling-tower pumps should be installed in accessible places in the plant. The common practice of put ting the pumps in out-of-the-way corners has nothing to commend it. The various water lines can be painted in different colors; this enables the operator to trace out a line with a minimum of difficulty.
Effects of Bad many Western and Southwestern states bad water is one of the serious problems confronting the Diesel operator. The organic matter in suspension as well as certain mineral salts tend to deposit in the cylinder jacket and cylinder head. These deposits must be removed if the required cooling effect is to be maintained. Many oil engines have had the cylinders badly distorted as a result of heavy scale forma tions. Deposits are especially dangerous when formed on the heads of horizontal engines. The expansion and contraction of the metal causes the scale to flake off, exposing a red-hot iron surface to the cooling water. Local fractures result, later develop ing into cracks across the cylinder head.
When the water scales, a periodic inspection of the jackets is necessary. It is impossible to reach all the scale with a scraper; consequently a muriatic acid solution should be left in the jacket for a few hours, followed up by a thorough flushing with water. If the deposits are heavy, a 50-50 solution of acid and water may be used, though ordinarily a 10 per cent. solution is amply strong.
Practically all mineral salts will not settle at a temperature lower than 150°. If the discharge temperature of the cooling water is maintained below this point but little scale will occur. This low temperature affects the engine's efficiency, but not to any marked extent.
Purification of Water a plant is of considerable size, it is of advantage to install a water purification plant. The type of purification system to be used depends on the results desired.
Sediment. Mud. the water is taken from a stream holding much mud or sand in suspension, a large settling basin with a filter on the cooling-water suction line is all that is nec essary to secure a satisfactory cooling medium.
Bicarbonates of Lime and removal of these salts requires a purification system involving the employment of chemical reagents. The character of the supply water must be analyzed and the correct system installed. The proper course is to purchase a system from one of a number of well-known manufacturers. This guarantees a certain performance of the apparatus installed. A fair estimate of the cost of a purifier is approximately $7.50 per horsepower of station engine capacity. The majority of purifiers are based on the lime and soda process where either lime or soda is used as the reagent, at times in combination with other chemicals.
Exhaust Distiller.—The logical method of water purification is the employment of an exhaust distiller. This heater is placed in the engine exhaust line and absorbs part of the heat contained in the exhaust gases. The engine cooling water ordinarily loses 3 per cent. of its volume in being cooled. The make-up water necessary to balance this loss is first circulated through the heater and is converted into steam at atmospheric pressure. This steam is then led to a closed heater where it is condensed by cooling water from the source of supply. The heater is, in form, nothing but a steel tank filled with 2-inch tubes through which the water circulates. The heater in Fig. 172 has both heads flanged, which feature allows the tubes to be bored out with a hydraulic turbine tube cleaner.
To raise the temperature of the feed water before it enters the tank, the feed line can easily be passed through the engine exhaust pot. This will raise the temperature to about 150°. In computing the size of heater required for any given plant, 1 sq. foot of heater surface per horsepower will be amply large to absorb all available exhaust heat. The heat wasted by the engine will average 3000 B.t.u. per horsepower, and the heater will abstract 2000 B.t.u. This will give roughly 2 pounds of make-up water per horsepower. Since the cooling loss will not exceed 3 per cent., this amount of make-up water is sufficient even when the quantity of water used exceeds the usual 60 pounds per brake horsepower. Figure 173 is a schematic layout of a make-up water system. The advantage of this method of water supply lies in the absolute purity of the engine cooling water.
A distiller should be made of cast iron rather than steel plate to better resist the corrosive action of the exhaust gases. No foundry can build such an article at an attractive price if the pattern cost is assessed against one distiller. To date no manufacturer has attempted to standardize this accessory. A very serviceable one can be obtained by adapting the S. and K. Oil Cooler to distilling purposes. This is of cast iron throughout with the exception of the tubes and baffle plates.
Temperature of Cooling Lines.—Each engine possesses in dividual characteristics that preclude any set rules as to the tem peratures that should exist in the discharge cooling lines from the various parts. Table II is the schedule that is followed in a plant containing three 500 h.p. vertical Diesels. These values give the best possible operating results as applied to these particular units.