In constructing pipes several important rules must be observed. In making a change of direction of 90 degrees the elbows should be made of not less than 5 pieces, and the radius of the inside of the bend should not be less than the diameter of the pipe, as shown in Fig. 55.

Fig. 55. Heating Pipe Elbows.

Fig. 56. Heating Pipe Y.

Fig. 57. Heating Pipe Reducer.

Where a main pipe is divided, the construction should be as shown in Fig. 56, the pieces A A being the frustum of a cone whose diameter at the base and whose height are equal to the diameter of the main pipe, and whose smaller end is equal to the diameter of the branch pipe, as shown in Fig. 57. This pipe is then cut to the proper form to fit its counterpart, as shown in Fig. 56.

Where branches are taken off from a main or leading pipe they should be so arranged as to leave the larger pipe at an angle of not over 45 degrees, and the inside radius should be not less than their diameter, as shown in Fig. 58. The contraction of the leading pipe, due to the taking off of this branch, should be made by the next sheet, the sheets being usually 30 inches wide.

This reduction of area should not be quite as much as the area of the branch pipe.

The further the air travels from the fan, the less force it has, and this should be compensated for, as far as may be, by slight allowances in area as the various branches are taken off, bearing in mind that this allowance should finally lead up to 25 per cent excess of outlet areas over the area of the main pipe at the fan.

In offices and comparatively small rooms the outlets are usually in the form of rectangular registers placed in the side walls near the ceiling. The area of these should be from two to three times the area of the pipe leading to them.

Fig. 59 shows the plan of the arrangement of the heating system of the machine shop and Fig. 60 a cross-section of the same, giving the diameters of the pipes at various distances from the heaters; and the number, direction, diameter, and location of the openings, not only for the machine shop proper but for the carpenter shop, wash rooms, etc.

The heating apparatus consists of a rectangular iron case containing a large number of steam pipes of practically U-shaped form, inverted and connected to a cast iron base in such a manner that one leg of the pipe connects with the space through which the steam is admitted and the other leg connects with the space from which the drip is taken. These pipes should be located as close to each other as practicable, the rows of pipes being set "staggering" so as to break up the currents of air. The casing which surrounds them and connects with the inlet of the fan should also be formed as closely to the pipes as may be, in order that all air which is drawn through may come into close contact with the heating surfaces of the pipes.

It is customary to allow one foot of 1-inch pipe, or its equivalent, to each 100 to 150 cubic feet of contents of the building to be heated, when all the air is taken from out-of-doors. In the case under consideration, with one half or more of the air from within the building the higher figure would probably be ample. At the end opposite the fan are located dampers for regulating the amount of air supply. One of these may be connected with a cold-air duct from out-of-doors, where necessary.

Referring to Figs. 59 and 60 the location of the apparatus is seen to be in the gallery floor, near the center of the building. The fan has two discharge openings, one downward for warming the side wings of the first floor, and one at an upward angle for the same service on the gallery floor. The returning currents of air flow into the central portion of the building and warm that portion in their upward course.

Branch leading from Main Heating Pipe.

Fig. 58. Branch leading from Main Heating Pipe.

Plan of Heating System for Machine Shop.

Fig. 59. Plan of Heating System for Machine Shop.

Cross Section through Machine Shop.

Fig. 60. Cross Section through Machine Shop.

Two sets of apparatus are used, for the reason that the traveling crane over the central portion of the shop prevents convenient connections between the two sides; and further, that the space to be heated is so large that the questions of convenience and economy are best met by this arrangement.

The apparatus on the side nearest the power house will require a fan with a wheel say 100 inches diameter by 52 inches wide, and running at about 185 revolutions per minute. This will supply from its downward opening the pipes for the main floor, including that leading to the carpenter shop and to the wash room on the first floor; and from its upward opening it supplies the pipes from the gallery floor, including one for the wash room on the second floor.

The apparatus on the opposite side of the shop should have a fan with a wheel say 90 inches diameter by 48 inches wide, running at about 205 revolutions per minute. The pipe connections are similar to the first apparatus, except that there are no long branch pipes to be provided for. Hence, while a 36-inch pipe is necessary for the side toward the power house, in order to warm the carpenter shop and the wash rooms, one of 29 inches diameter wall be quite sufficient for the opposite side. It should be said that the dimensions given on the drawings are from actual calculations, taking into consideration all the circumstances of the form and dimensions of the buildings, and they will probably be found correct in practice as in theory.