Fluid handling – Liquid level responsive or maintaining systems – By float controlled valve
Reexamination Certificate
1999-02-16
2001-03-20
Walton, George L. (Department: 3753)
Fluid handling
Liquid level responsive or maintaining systems
By float controlled valve
C137S426000, C137S429000, C251S065000
Reexamination Certificate
active
06202676
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a liquid level control unit that has particular application in regulating the level of water in a feedwater receiver of a boiler system. The liquid level control unit is adapted to translate changes in the level of a liquid of several inches into small displacements of 3 or 4 thousandths inch. In the preferred embodiment, the translated displacement operates an air valve that controls an air-operated, water control valve for adding make-up water to the feedwater receiver.
The liquid level control unit of this invention is suitable for isolated liquid systems. In a feedwater receiver for a boiler system, the water in the receiver is circulated to a boiler in a circuit that avoids contact with air. In order to translate movement of a internal water displacer device within the receiver tank to an external air valve actuator, the control unit utilizes a magnetic motion transfer mechanism. With this mechanism the internal displacement apparatus is isolated from the external actuator apparatus. The unit does not utilize seals or diaphragms that wear and may eventually leak. Also, the unit is entirely mechanical in operation. In this manner the unit is suitable for use in systems such as a boiler systems where auxiliary components must have a high degree of reliability. It is desirable that the control system be operable during a temporary electrical power failure. Therefore, the unit utilizes a mechanical permanent magnet actuation mechanism to actuate changes in a pressurized air circuit which regulate the water control valve of the boiler system supply water.
SUMMARY OF THE INVENTION
This invention relates to a liquid level control unit that in its preferred embodiment regulates a water supply valve for make-up water in a boiler system. The preferred embodiment of the liquid level control unit includes an actuator mechanism with an air valve to regulate an air-controlled water valve. The air-controlled water valve operates when the water level in a receiver tank for the boiler feedwater drops below a predetermined level. During such state the water valve opens to connect a water supply source to the receiver tank and supplies water until the water level rises and the liquid control unit determines that the appropriate level has been reached, causing the water valve to close.
In a boiler system the feed water receiver tank provides for storage of treated water supplied to the boiler. The receiver tank is partially filled with conditioned and deaerated water that is returned to the tank from the boiler as condensate. During continuous cycling of water to and from the boiler, losses occur that necessitate replenishment as make-up water from a supply source. In order to provide for deaeration of the make-up water and to accommodate for surges in the water supply, the receiver tank is not filled to capacity and the water level is maintained at an optimized level during operation.
The liquid level control unit of this invention includes a displacer element that is suspended in the receiver tank and partially immersed in the water. The displacer element is preferably made of a sinkable material, although a floatable material may be suitable in certain environments.
The preferred displacer element is a cylindrical weight suspended by a rod that is connected to a spring. The rod and spring connection preferably places the spring in compression. The rod has a distal end with a permanent magnet assembly that includes a pair of annular magnets that sandwich a Teflon® guide washer. The guide washer has a slightly greater diameter than the annular magnets and allows displacement of the magnet assembly in a stainless steel tube. The tube has an open end in communication with the receiver tank through which the rod and magnet assembly are installed and a closed end that isolates the displacer components from the external environment.
The cylindrical tube projects from the receiver tank with the closed end contained in a housing. The housing also encases a magnetic actuator mechanism with an external permanent magnet assembly having a pair of annular magnets mounted on a displacement plate and concentrically positioned over the cylindrical guide tube at the location of the pair of magnets within the tube.
The displacement plate functions as a cantilevered balance beam with linear displacements of the immersed displacer element translated into small arcuate displacements of the displacement plate. The displacement plate is supported on a pair of spaced springs against a pivot and acts as an actuator lever against an air release valve.
The air release valve forms part of a pressurized air circuit that includes an air supply, a constricted flow orifice, a pressure gauge, and an air regulated water control valve.
In the preferred embodiment the housing has a base plate with two alternate locations for mounting the air release valve, so that the system can be used with a direct acting or reverse acting valve. The liquid level control unit includes an adjustment mechanism for limited adjustment of the flow rate of the makeup water by altering the applied force of the displacement plate on the air release valve. These and other features will become apparent on a consideration of the detailed description of the preferred embodiment that follows.
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Peterson Richard Esty
Walton George L.
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