Maxims and Instructions for the Boiler Room / Useful to Engineers, Firemen & Mechanics; Relating to Steam Generators, Pumps, Appliances, Steam Heating, Practical Plumbing, etc.

by N. Hawkins

STEAM AND HOT WATER HEATING.

The heating by means of pipes through which are conveyed hot water and steam is a science by itself and yet one claiming some degree of familiarity by all engineers, steam users, and architects.

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In practice it requires a knowledge of steam, air and temperatures, of pressure and supply; a familiarity with heat and heating surfaces and with all contrivances, appliances and devices that enter into the warming and ventilation of buildings. So long as factories, public and private buildings are erected, so long will warming and ventilation keep progress with steam engineering and remain a part of the general mechanical science required of the supervisory and practical engineer.

In what is called the system of open circulation, a supply main conveys the steam to the radiating surfaces, whence a return main conducts the condensed water either into an open tank for feeding the boiler, or into a drain to run to waste, the boiler being fed from some other source; the system of what is called closed circulation is carried out either with separate supply and return mains, both of which extend to the furthest distance to which the heat has to be distributed, or else with a single main, which answers at once for both the supply and the return, either with or without a longitudinal partition inside it for separating the outward current of steam supply from the return current of condensed water.

In either case suitable traps have to be provided on the return main, for preserving the steam pressure within the supply main and radiators. These two systems, in any of their modifications, may also be combined, as is most generally done in any extensive warming apparatus.

The system of closed circulation requires the boiler to be placed so low as will allow all the return pipes to drain freely back to it above its water-level. This condition has been modified mechanically by the automatic “trap,” a device frequently employed for lifting from a lower level, part or all of the condensed water, and delivering it into the boiler; it is, in fact, a displacement pump.

The same result has been attained by draining into a closed tank, placed low enough to accommodate all the return pipes, and made strong enough to stand the full boiler pressure with safety, and then employing a steam pump, either reciprocating or centrifugal, to raise the water from this tank to the proper level for enabling it to flow back into the boiler, the whole of the circulation being closed from communication with the atmosphere.

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There are two systems of steam heating, known as the direct and the indirect system.

Direct radiating surfaces embrace all heaters placed within a room or building to warm the air, and are not directly connected with a system of ventilation.

Indirect radiation embraces all heating surfaces placed outside the rooms to be heated, and can only be used in connection with some system of ventilation.

For warming by direct radiation, the radiators usually consist of coils, composed of ³⁄₄-inch and 1-inch steam pipes, which are arranged in parallel lines and are coupled to branch tees or heads. In a few exceptional cases, radiators of peculiar shapes are specially constructed. In all cases the coils must have either vertical or horizontal elbows of moderate length, for allowing each pipe to expand separately and freely. Sometimes short lengths of pipe are coupled by return-bends, doubling backwards and forwards in several replications one above another, and forming what are called “return-bend coils,” and when several of these sections are connected by branch, tees into a compact mass of tubing, the whole is known as a “box-coil.”

Steam and Hot Water heating have long been acknowledged as altogether most practical and economical in every way—and their universal adoption in all the better class of buildings throughout the country is positive proof of their superiority.

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The heat from steam is almost exactly identical with that from hot water, and few can distinguish between the two systems when properly erected.

They are both healthful, economical and satisfactory methods of warming. They give no gas, dust nor smoke; are automatically regulated, and therefore allow of an even and constant temperature throughout the house, whatever be the condition of the weather outside.

The circulation of the steam through the warming pipes is effected in an almost unlimited variety of ways, and the cause producing the circulation throughout the pipes of the warming apparatus is solely the difference of pressure which results from the more or less rapid condensation of the steam in contact with the radiating surfaces.

A partial vacuum is formed by this difference of pressure within the radiating portions of the apparatus, and the column of steam or of water equivalent to this diminution of pressure, constitutes the effective head producing the flow of steam from the boiler, at the same time the return current of condensed water is determined by the downward inclination of the pipes for the return course.