This device, where it can be used at all, is economica! in that it not only feeds the boiler, but also heats the

water without the use of live steam. But it will not force the water against a pressure much above 75 lbs.

to the square inch, and if the initial temperature of the water is much above 75° F. the exhaust injector will not handle it. Heaters which use live steam direct from the boilers heat the feed water to a much higher temperature, so that they act as purifiers by removing a large portion of the scale-forming impurities before the water enters the boiler. Live steam heaters, however, are not to be considered as economizers of heat.

Provisions for Testing. While considering feed pipes and other apparatus necessarily appertaining to the feeding of boilers, it is well to devote a short space also to the fittings and other devices required for successfully conducting tests of the boiler and furnace. This subject is mentioned here for the reason that the author considers that the necessary fittings and appliances for making evaporative tests properly belong to, and in fact are a part of, the feed piping, and can be put in while the plant is being erected at much less cost and trouble than if the matter is postponed until after the plant is in operation.

Beginning then at the check valve, there should be at tee located in the horizontal section of the feed pipe, as near to the check valve as practicable, and between it and the feed pump; or a tee can be used in place of an ell to connect the vertical and horizontal sections of the branch pipe where it rises in front of the boiler. One opening of this tee is reduced to 3% or 1⁄2 in. to permit the attachment of a hot water thermometer. These thermometers are also made angle-shaped at the shank, so that if desired they can be screwed into a tee placed in vertical pipe and still allow the scale to stand vertical. The thermometer is for the purpose of showing at what temperature the feed water enters

the boiler during the test, and therefore should be as near the boiler as possible. After the test is completed the thermometer may be taken out and a plug inserted in its place.

The next requirement will be a device of some kind for ascertaining the weight of water pumped into the boiler during the test. In some well ordered plants each boiler is fitted with a hot water meter in the feed pipe, but as this arrangement is hardly within the reach of all, a substitute equally as accurate can be made by placing two small water tanks, each having a capacity of eight or ten cubic feet, in the vicinity of the feed pump. These tanks can be made of light tank iron, and each should be fitted. with a nipple and valve near the bottom for connection with the suction side of the pump. The tops of the tanks may be left open. If an open heater is used, and it is possible to place the tanks low enough to allow a portion of the water from the heater to be led into them by gravity, it will be desirable to do so. A pipe leading from the main water supply, with a branch to each tank, is also needed

for filling them. One of the feed HOT WATER THERpumps, of which there should always

MOMETER.

be at least two, as already stated, is fitted with a tee in the suction pipe near the pump to receive the pipe

leading from the tanks. During the test the main suction leading to this pump from the general supply should be kept closed, so that only the water that passes through the tanks is used for feeding the boiler. If the plant be a small one, with but one or two boilers and only a single feed pump, the latter can be made to do duty as a testing pump, because during the test there will be no other boilers to feed besides the ones under test.

If metal tanks are considered too expensive, two good water-tight barrels, can be substituted. Fig. 10 will give the reader a general idea of what is needed. for obtaining the weight of the water by the method just described. If a closed heater is used and no other boilers are in service during the test, the cold water can be measured in the tanks and pumped directly through the heater, but if it is necessary to feed other boilers besides those under test, then either a separate

feed pipe must be run to the test boilers, or else hot water meters will have to be put into the branch pipes.

In cases where a separate feed pipe must be put in for the test boiler and the water which is used for testing cannot be passed through a heater, there should be a 3/4 or 1 in. pipe connected to the feed main or header and leading to the testing tanks, in order to allow a portion of the hot feed water to run into and mix with the cold water in the tanks as they are being filled, thus partially warming the water before it goes to the boiler.

Heating Surface.

In a

The heating surface of a boiler consists of that portion of the boiler which is exposed to the heat on one side and water on the other. horizontal boiler of either the flue or tubular type, the available heating surface is, first, the lower half of the shell; second, the area of the back head below the water line minus the combined cross sectional area of all the tubes or flues; third, the inside area of the flues; fourth, the area of the front head minus the sectional area of the flues.

For a fire-box boiler of the vertical type, the area of the flue sheets minus the sectional area of the flues, plus the area of the fire-box plus the inside area of the flues constitutes the heating surface. If the boiler is a horizontal internally fired boiler, the heating surface will consist of, first, area of three sides of the firebox; second, area of the crown sheet; third, area of flue sheets minus sectional area of flues; fourth, inside area of the flues.

In estimating the area of the fire-box, the area of the fire door should be subtracted therefrom. If the firebox be circular, as in the case of a vertical boiler, the area may be obtained by first finding by measurements