Level control valves maintain a constant level in a liquid supply such as a reservoir or vessel or distillation column. These are used to manage the filling of tanks and vessels by means of a mechanical float that operates a small pilot valve to control the main valve. The main valve allows water to flow down and impulse line to the pilot valve at the float. When the tank is full and the float is level, the pilot valve is closed and this prevents the main valve from opening. As soon as the level drops and the pilot valve opens, the main valve also opens and a small quantity of the liquid from the pilot line releases into the tank to maintain the open position of the main valve until the float is again level and both the pilot and main valves shut.
This is similar in principle to the altitude control valve, more often used for supplying water to elevated tanks and reservoirs. With the altitude control valve, a float is not used and instead a sensitive diaphragm responds to changes in pressure to determine whether the main valve should open or not.
Level Control
Application :
- Closes when a water tank reaches a required level.
- Opens when the water head falls below the inertia of the altitude pilot.
- The valve controls filling of a tank to an adjustable level.
- Altitude pilot senses the level in the reservoir in terms of pressure and which will open and close as per the minimum and maximum set level.
Working Principle :
- The altitude pilot is located on the main valve at the bottom of the reservoir.
- In the altitude pilot we can manually set the level required on the reservoir in terms of pressure.
- The pilot is connected with the reservoir with a sensing line, which will transmit the current level to the pilot.
- The valve will close when the water tank level reaches desired level.
- Valve opens to fill reservoir when level drops to the minimum level depending on pilot range.
