Automatic Water Level Control for Tanks
A new device known as the Johnson Tank Level Controller and made by Edward E. Johnson, Inc., St. Paul, Minn., automatically regulates the level of the water in the tank and avoids all danger of overflow. This is accomplished by the rising and lowering of mercury in a tube, counterbalanced by the pressure of the water in the tank. As this pressure varies by the rise and fall of the water level so does the height of the mercury column in the controller. The controller regulates by this means the start and stop buttons of the electric motor actuating the pumps.
As the water lowers in the tank, the mercury contact tube approaches contact. When this occurs an electric circuit is closed, thereby energizing the relay, starting the motor, cutting out the red low water signal, and lighting the green signal, indicating that the tank is above the predetermined low level. When the mercury reaches the high level contact the other relay is energized, which opens the pilot circuit in the automatic motor controller, thus stopping the motor and pump.
Due to the rclavs and their hook-up, the motor will not cut in or out, except at predetermined high and low levels. 1 his means that once the high level of the tank has been reached, and the motor and pump shut off, there will he no start until the low level has been reached, and that when once the motor has been started at the low level, it will not stop before the high level has been attained.
Another advantage claimed for the controller is the saving in repair of the tank. When water is allowed to overflow, the incrusting solids in it will rapidly corrode the paint, whereas if the overflow is avoided the expense of repainting is avoided.