The collapsing of range boilers and explosion of water fronts may occur from several different causes. If the connections-between the range and the boiler on a pressure system should be frozen, there would be serious danger of an explosion.
If the pipes were thus frozen, expansion would be cut off and steam would be generated, resulting in the explosion of the boiler if the range fire should be started under the circumstances. If the supply to the boiler on a tank system, and the expansion pipe should be frozen, a fire built in the range would be liable to burst the boiler, especially as tank boilers are not constructed to withstand such high pressures as pressure boilers. Even though the boiler were full of water, with the boiler supply frozen, the contents of the boiler would not flow to the water front, for the reason that the frozen section of the pipe would prevent the action of atmospheric pressure from above on the water in the boiler.
It is well in the winter season, whenever the range fire is allowed to go out at night, to open faucets before building the kitchen fire, in order to make sure that the pressure is on and no freeze-up has occurred during the night. The workman, in making repairs to the piping on pressure work, such as repairing faucets, etc., when the range fire is going, should open a hot-water faucet as soon as the boiler valve is closed, in order that any expansion may have a vent.
When the cold-water supply for any reason is shut off from the water front, and the latter becomes very hot, the moment water is allowed to enter it again steam will be generated the instant the cold water comes in contact with the hot surface of the water front, the expansive force of the steam being very great, and in danger of bursting the water front, unless there is a vent for it. For this reason it is a dangerous matter to use valves on the range connection. They are sometimes used in multiple connections, and also sometimes on the ordinary single range connection, as a matter of convenience. It will be seen that the use of such valves would allow the water front to be cleaned out without drawing off the boiler, and in sections where the water is full of lime and the water front must be cleaned from time to time, it is very convenient to use these valves. Their use is accompanied with danger, however. For instance, the valves may be forgotten when the water front is put back, and there is liable to be enough moisture present to form steam, which without outlet is liable to be a dangerous factor. Then, again, one valve may be opened and the other through carelessness allowed to remain closed. The choking of water pipes with deposits of lime, rust, and sediment is another cause of water-front explosions.
In addition to the collapsing of boilers due to the siphonage of the contents of the boiler, there is another way in which the same result may occur. To produce a collapse of the boiler, it is necessary to create a vacuum inside it, the collapse being just opposite in action to the bursting of the boiler. Therefore, anything causing a vacuum to be formed within the boiler, will result in its collapse, if the boiler is not strong enough to withstand the strain. It is comparatively common to find the boiler collapsed, owing to the ignorance of the inmates. For instance, the supply to the boiler may be found frozen in the morning after the range fire has been started. To obtain water for the use of the household, it may be drawn out of the sediment cock. Meanwhile the water front is heating the boiler and filling it with steam. When the pipe supplying the boiler thaws out, the cold water rushes in, instantly condenses the steam, thus causing a vacuum, and the boiler collapses if not sufficiently strong to withstand the outside pressure. The collapse occurs, owing to the fact that when the vacuum exists inside there is no pressure to hold the sides of the boiler out, and they are crushed in by atmospheric pressure, which is approximately 15 lbs. to the square inch. It is very rarely that a galvanized wrought iron boiler collapses, as it is of sufficient strength to withstand the pressure of atmosphere against a vacuum. It is not an uncommon occurrence for copper boilers, however, to suffer from this cause, unless strengthened inside. A collapsed copper boiler may often be forced back by turning on the pressure, and sometimes this can be done so effectively that almost no trace is left on the sides of the boiler of its collapse. A collapsed boiler should never be struck with a mallet or hammer, however, as the marks and indentations thus made will not be taken out when the boiler is forced back into shape. If the pressure is insufficient to force the boiler into its original shape, the head must be taken off and the side forced out from the inside. The use of safety valves on range boilers is seldom seen, and their use is not necessary if the boiler is properly provided for.
Fig. 259. - The Two Common Styles of Bibbs.
There are three kinds of bibbs or faucets used in connection with the water supply: compression work, Fuller work, and self-closing work, the two first named being most common. From a glance at the compression and Fuller faucets shown in Fig. 259, it will be seen that the latter works with a cam motion, and that when the faucet is closed, it is closed very quickly, whereas, in order to close the compression faucet, the handle must be turned several times, and a much longer time thus taken in shutting off the water. Water, as is well known, is almost incompressible, and will not compress sufficiently to take up a sudden shock. Therefore, in the use of Fuller work, much trouble is caused due to the rattling of pipes when faucets are closed, a feature entirely lacking in compression work. Therefore, even though Fuller work is more expensive than compression, and used very extensively on high-grade work, compression work will in general be found to give much more satisfactory results. Not only is the hammering of pipes disagreeable, but such action is necessarily harmful to pipes and valves.