To regulate the pressure, place weights on the float until sufficient gas flows to the burners to give a good flame.
MERCURY GAS GOVERNOR
In a governor of this style, the gas from the main line passes through the upper pipe, down through the internal tube, and escapes between the end of this tube and a column of mercury in the mercury tube, passing up behind the internal tube, and out through the lower pipe to the burners.
To prepare the governor for use, remove the adjusting rod and pour in mercury until it rises in the mercury tube almost to the lower end of the internal tube, which can be seen through the glass disk at the side of the governor. When the metal in the pot reaches the proper temperature, the surface of the mercury stands at the lower end of the internal tube, but a notch in the side of this tube above the mercury permits a flow of gas sufficient to prevent shutting the gas entirely off underneath the pot. When the temperature falls, the mercury in the holder and column will be cooled, and its surface lowered in the tube. This will allow an increased flow of gas to the burner until the temperature of the pot is raised to the proper point.
The regulation of the governor is effected by moving the adjusting rod in or out. If the temperature in the pot is too high and the mercury fails to close the tube, the adjusting rod must be moved in until the mercury raises in the tube. If the temperature in the pot is too low, the mercury closes the tube before the proper temperature is reached in the pot. Thus the rod must be moved out until the mercury is lowered from the top of the tube to the proper extent.
THERMOSTAT GAS GOVERNOR
The supply of gas at the burners is controlled by the expansion and contraction of rods immersed in the molten metal in the crucible at the left-hand side of the metal pot. These rods are of a special alloy, which is extremely sensitive to variations of heat. No mercury is used, so that the governor is not affected by the pressure of the gas at any time.
The principle upon which the thermostat is built, is the difference in expansion of two metals under heat.
The part of the thermostat which is immersed in the metal is made of cast iron and has a hole or pocket in which the rod of composition metal sets. The upper end pushes against a hinged lever; the other end of this lever operates a valve plunger. The expansion of the thermostat rod being greater than cast iron, raises the valve lever, which forces down the valve plunger, seating the plunger nearer the valve seat. This cuts down the flow of gas to the burners. The rod contracts as the metal cools, and allows the valve spring to open the valve.
Underneath the valve rod cap and encircling the valve rod, is a spiral spring which raises the valve rod as the expansion rod contracts, which opens the gas inlet, and also keeps the expansion rod pushed to the bottom of the pocket.