This section is from the "Modern Machine Shop Construction, Equipment, And Management" book, by Oscar E. Perrigo. Also see Amazon: Modern Machine Shop Construction, Equipment, And Management.
Various heating systems. Leaking steam pipes. The condensation nuisance. Hot water heating. Hot air furnace. Of heating and ventilation. General requirements of a heating system. Form, size, and location of pipes. Construction of elbows, tees, Ys, and branches. The heating apparatus for the machine shop. Plan and cross-section. Heating surface required. General plan of the system. Location of the heating apparatus. Power for driving fans. Steam for heating. Heating apparatus for the foundry. Plans and cross-sections. Heating the office building. Plans and longitudinal sections. The proper temperatures for the different buildings.
The construction of our several buildings being now completed and all arranged with proper consideration of the existing conditions and the expected circumstances by which we shall be governed, it is necessary that we should arrange for their proper and efficient heating and lighting. In this article the first of these questions, that of heating, will be considered.
There are many systems of heating buildings, among which are: By means of exhaust steam or of live steam, in lines of pipe arranged overhead or along the walls; by coils or radiators; by hot water utilized in a similar way; by air heated by furnace arrangements or by contact with pipes through which steam flows. All these systems have their good and bad features, both as to their warming qualities and their cost, as well as the expense of operating them. The hundreds of feet of steam pipes, with their numerous fittings, furnish at each joint opportunities for leaks, and special arrangements must be made to keep them clear of water. The distance from the boiler to the further end of long systems frequently requires much time to force enough steam to these points to warm the rooms so that they will be endurable to workmen.
The hot-water system works slowly and the temperature of the surrounding air rises gradually, so that the hour for beginning work in the morning must be anticipated by such a length of time as to be a serious drawback to complete success. The hot-air furnace gives air from which much of the moisture is evaporated and which is therefore unwholesome, aside from the fine dust so often brought along with it. In all these systems heating is the only end gained, ventilation being left largely to chance.
The ideal system of warming and ventilation would seem to be that in which fresh air, warmed by steam heat, is distributed by a suitable mechanical process, as evenly as possible to every part of the building, and one in which this can be done in the shortest time (as in most shops the heat is not maintained during the night except at sufficient temperature to prevent freezing of water pipes, etc.), and in which cold air may be readily introduced whenever needed.
This seems to be best accomplished by drawing fresh air from without the building,'passing it through a heating apparatus consisting of an iron case containing a large number of steam pipes, and, by means of a fan and suitable pipes, distributing this warmed air to every part of the building by numerous outlets. The whole should be controlled by proper dampers, by which a due proportion of warm and cold air may be furnished as needed, so that proper ventilation as well as warming may always be maintained.
In the warming of such large buildings as those under consideration it is not necessary to draw cold air from the outside atmosphere to any great extent. The number of cubic feet of air contained in the building is largely in excess of that required for each person; and, moreover, cold air comes in through frequently opening large doors, while the swinging windows at the roof may be opened when necessary to permit the vitiated air to pass out, thus providing ample ventilation.
Many pages might be written on this subject, but space permits only a few general requirements which are practically indispensable, and may be summed up as follows:
The heating apparatus should be located near the center of the building so as to distribute the warm air to all points with the least amount of piping.
Openings should be so arranged as to be not over 30 feet apart, and to open toward the outer walls of the building. They should not be less than 8 feet above the floor, nor less than 5 inches diameter, and usually incline downward at an angle of about 10 degrees. The aggregate area of openings should exceed the area of the main pipe at the fan by about 25 per cent.
About 6 square inches area of openings should be allowed to every thousand cubic feet of space contained in the building - or room, where the building is so divided. The velocity of air should not be less than 1,500 feet per minute, and a sufficient quantity should be supplied to change the air every 15 to 20 minutes.
The pipes are preferably circular, as less material is required to make them of this form; furthermore, the circular pipes are stronger, and there is less friction of air in passing through them. For instance, a circular pipe 5.65 inches in diameter will have an area of 25 square inches and its circumference will be 17.88 inches. A square pipe 5 inches each way will also have an area of 25 square inches, but the sum of its four sides will be 20 inches. A rectangular pipe 2 × 12.5 inches will be of equal area, but the sum of its sides will be 29 inches, or about 1.6 times greater than the circular pipe.
Nevertheless it often happens that square or rectangular pipes are necessary, on account of lack of space. When such is the case this area of cross-section must be increased accordingly, so as to avoid undue friction. Galvanized iron is the most desirable material for these pipes and is almost universally used where pipes separate from the building construction are employed. In factory buildings having several floors, proper flues and air ducts are arranged in the walls, and in the basement, where the heating apparatus is usually located.