Steam-Heating Systems

70. Equipment for Steam Heat. A steam-heating system consists of a boiler, a fire pot, pipes from the boiler leading to the radiators, and radiators (Fig. 35). On some systems, return pipes are provided to carry condensed steam or water back to the lower part of the boiler. A safety valve (Fig. 36) is attached to steam-heating systems instead of an expansion tank. This keeps the pressure of the steam in the boiler from becoming too great, and thereby prevents an explosion. The pressure gage (B, Fig. 35) must be set, and, when set, should only be changed by a person understanding it. Build and manage the fire for a steam boiler the same as for any stove or furnace. Keep water in the boiler at 212 degrees Fahrenheit, so steam may form, for without it, the radiators will not be heated. Small valves are attached to most steam radiators. Their purpose is to let out air, which accumulates in the radiator. As soon as the steam begins to come into the radiator, it forces the air out of the valve. When it reaches the valve, the heat in the steam causes part of the valve to expand and close the outlet, which is small. When the radiator is hot, steam should not escape, provided the valves are in good working order. There is a gage (Fig. 37) furnished with each boiler which shows how much water is in it.

Keep enough water in the boiler to come within certain lines on the indicator. The top of one of these lines is usually six or eight inches from the top of the boiler. There is always some variation in the amount of water in steam furnaces on account of the formation and condensation of the steam in pipes and radiators. See that the boiler is never empty, but do not put in fresh water except when necessary.

The space above the water in the boiler is left for steam. The loss of water from a boiler in good working order is thru the air valves in the radiators. If the furnace is properly managed, very little water should be lost during the course of a year, so there is little need for adding water.

Some furnaces have two pipes to the radiators. When steam is shut off from a radiator, the valve leading to the pipe which carries off the water from condensed steam must be closed, also, to prevent the pressure of the steam in the boiler from forcing water from the boiler up this pipe. This may happen because the pipe draining the water from the radiators enters the furnace near the bottom of the boiler. The steam being retained in the furnace presses down on the water and so may force water up the drain pipe, if it is not closed, instead of raising the safety valve.

Carelessness of this kind may work much damage, for by this means all the water from the furnace can be forced up into the radiators, leaving the boiler empty. This makes it important that every woman should understand the steam-heating system in her home.

Some steam-heating systems have a check valve in the pipe which returns water to the boiler. This valve permits water to flow thru it in but one direction; that is, toward the boiler. This prevents a rush of water from the boiler to the radiators.

Steam furnaces, also, are often equipped with another safety-valve device, which is a plug of metal which melts at a rather low temperature and is placed in the boiler directly over the fire. If the water line in the boiler falls low, this plug melts and steam from the boiler puts out the fire, thus saving the furnace from damage.

However, melting out the plug makes much work both in replacing the plug and in cleaning the fire box to rebuild the fire, so that it should not be depended upon to regulate the heat in the boiler.

Knocking in steam radiators occurs most often in those systems using the inlet steam pipe for the return of the water which has formed as a result of condensation. It is caused by water accumulating at some point and the steam coming up the pipe, violently forcing it back into the radiator. This only reaches a danger point in systems which do not have pipes of the proper size, or when the pipes do not slope gradually downward, so that all the water may flow back to the furnace. On cold days, there will be some knocking in a steam radiator when it is being heated in the morning. A two-pipe system, while it is somewhat more expensive, is less subject to this trouble.

71. Steam Gages. Steam gages (B, Fig. 35) are devices for indicating the pressure of steam within an inclosure. They are a kind of spring balance. When the pressure of the steam increases, it pushes up on the spring, and this turns the hand of the indicator, which shows the number of pounds of pressure that the steam is exerting on the inside of the boiler or container.

72. Safety Valve. A safety valve (Fig. 36 and A, Fig. 38) consists of a small opening to a boiler over which is a weight. When steam is developed until it makes enough pressure on the inside of the valve to raise this weight, some of the steam escapes, thus lowering the pressure on the inside until the weight falls back into place. Never let anything interfere with the action of safety valves.

Most safety valves have the weight attached to a lever which has a movable weight on it so that the position of the weight on the lever makes a difference in the number of pounds of pressure required to open the valve. By means of this device, the temperature of the inside of the boiler can be kept at one heat or another as desired, since this temperature increases or decreases with the pressure under which the steam is held.

Thus, fifteen pounds pressure means a different temperature from ten pounds pressure. Be sure to adjust the weight for the temperature desired. Pushing the weight toward the valve lessens the amount of pressure needed to open the valve. There is usually a steam gage on boilers to indicate the temperature and pounds of pressure inside. When the indicator reaches the point desired, the safety valve may be set so that all steam in excess of the desired amount will escape. When this is done, the temperature will be held constant in the boiler so long as a good fire under it is maintained.