Fluid handling – Liquid level responsive or maintaining systems – By float controlled valve
Reexamination Certificate
1999-11-24
2001-06-05
Walton, George L. (Department: 3753)
Fluid handling
Liquid level responsive or maintaining systems
By float controlled valve
C137S085000, C137S269000, C137S416000, C251S282000
Reexamination Certificate
active
06240955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to fluid level sensing systems and which the level control is accomplished through the use of a float whose motion is transmitted to a pneumatic or electric controller which is connected to a valve and, specifically, to an improved liquid level controller having a pilot valve for sending an output signal pressure to a pneumatically operated process valve for controlling the valve.
2. Description of the Prior Art
The oil and gas, chemical and other industries utilize process valves for the control of process fluids which are operated by means of a pneumatic or electrical control signal. The pneumatic control for such valves typically includes a pilot valve whose function is to send an output signal pressure to the pneumatic controller, which either opens or closes the process valve. In the typical prior art system, the level of liquid in a tank or other container is sensed with a sensing element or float that is in communication with the liquid in the container and which transmits a force or movement to a control device that is situated outside the container. The force or displacement so sensed is a measure of the change in liquid level.
For instance, in the case of an oil and gas separator tank, a liquid level controller is provided which uses a float or displacement type sensor to transmit changes in the liquid level in the tank to a pilot valve outside the vessel. The pilot valve signals a process control or discharge valve in the discharge outlet from the vessel to open or close the discharge valve in response to the liquid level within the vessel.
Supply gas pressure was generally taken from the production gas and routed to the pilot valve. When the liquid level in the vessel is within the desired limit, the supply gas is vented through the pilot valve to the atmosphere. When the liquid level rises sufficiently to change the position of the float, the flapper applies a force to the pilot valve so that the supply gas is diverted within the pilot valve to thereby provide a control signal to the discharge valve which allows liquid to flow from the vessel.
Many of the prior art liquid level controllers require right or left hand mounting which requires that both mountings be available in inventory. Also, their conversion between such mountings requires extensive reworking of the mounting and the components. Liquid level controllers are described as “direct” and “throttling” in operation if an increase in level in the tank results in a proportional increase in outlet pressure from the controller. Controllers were described as “indirect and throttling” in operation if an increase in level within the tank resulted in a proportional decrease in outlet pressure from the controller. Controllers which operated in the “snap-on or snap-off” mode featured a sudden increase in output pressure with level increase in direct mode and a sudden decrease in output pressure with level increase for indirect operating mode.
The prior art devices were difficult to reconfigure for either direct or indirect signal operation and for snap-on and snap-off or throttling mode and lacked a convenient mechanism for varying the sensitivity of the devices. It was often difficult to reach the internal components of such devices for repair and reconfiguration. Conversion of the prior art devices from “snap-on and snap-off” to “throttling” mode of operation generally required disassembly and substitution of alternative parts. Where a supply gas filter was installed, the filter was difficult to access and clean.
An object of the present invention is to provide an improved liquid level controller which can be easily and quickly converted between direct and indirect action and which has a full range of sensitivity adjustment in both settings.
Another object of the invention is to provide a liquid level controller having an improved pneumatic pilot which is simply and easily switchable between a snap-on and snap-off and a throttling type action.
Another object of the invention is to provide an improved liquid level controller which utilizes an easily adjustable spring counterbalance to accept displacement sensors of various configurations.
Another object of the invention is to provide such a liquid level controller having a supply gas filter housing with an improved filter arrangement which facilitates maintenance or replacement of the filter element.
Another object of the present invention is to provide an improved liquid level controller which is simple in design, economical to manufacture and which is dependable in operation.
SUMMARY OF THE INVENTION
An improved liquid level controller is shown which includes a housing having a rear wall. A shaft has a first end which extends through the rear wall of the housing to a liquid displacement member and has a second end which joins a pair of oppositely extending arms. Each of the oppositely extending arms is rotatably mounted on the housing generally parallel to the rear wall by means of a pair of spaced apart bearings. Vertical forces responsive to changes in liquid level act on the displacement member and are transmitted as a force tending to rotate the oppositely extending arms within their respective bearings. A lever is pivotally mounted to the housing. A torque bar is connected to the oppositely extending arms of the shaft. Means are provided for interconnecting the torque bar and the lever for transmitting forces exerted on the shaft to the lever. A valving assembly is also provided which is acted upon by the lever to produce an output signal for controlling a liquid level. The means engaging between the lever and the valving assembly includes an adjustment member which is slidably mounted on the torque bar and engageable with the lever.
Movement of the adjustment member along the torque bar from one end to the opposite end thereof changes the output for controlling liquid level from direct to indirect acting output. The movement of the adjustment member along the torque bar also varies the sensitivity of the output for controlling liquid level.
Preferably, the valving assembly is a pneumatic pilot which includes a pressurized source of supply gas and means for conducting a signal pressure away from the pneumatic pilot as a control signal for controlling liquid level. The pneumatic pilot is mounted on the wall of the housing above the lever and has a contact point which is engageable by a pin carried by the lever. Slight movement of the torque bar is transmitted through the adjustment member to the lever pin, whereby movement of the lever actuates the pneumatic pilot. An output pressure gauge is mounted on the housing on one side of the pneumatic pilot. A supply pressure gauge is mounted on the housing on an opposite side of the pneumatic pilot and a cylindrical supply filter is located in a filter housing upstream of the supply pressure gauge. The supply filter housing includes an input for supply gas and an output and an internal flow path, flow of supply gas being from the inside of the filter to the outside thereof. A spring is arranged on the housing to counterbalance movement of the torque bar. The spring is preferably mounted for lateral movement toward and away from the housing rear wall to change the moment the spring force exerts counterbalancing the torque of the float arm.
Additional objects, features and advantages will be apparent in the written description which follows.
REFERENCES:
patent: 2649771 (1953-08-01), Parks
patent: 2653623 (1953-09-01), Hippen et al.
patent: 2944562 (1960-07-01), Glasgow et al.
patent: 3052254 (1962-09-01), Parks
patent: 3078716 (1963-02-01), Winters
patent: 3088485 (1963-05-01), Hanssen
patent: 3120241 (1964-02-01), Parks
patent: 3128784 (1964-04-01), Parks
patent: 3840044 (1974-10-01), Harris et al.
patent: 4436109 (1984-03-01), Taylor
patent: 4542765 (1985-09-01), Glasgow et al.
patent: 4543973 (1985-10-01), Ho
patent: 4700738 (1987-10-01), Frese et al.
Anderson R. David
Winfrey Carl Wayne
Winfrey Randal Alan
Anderson Controls, L.C.
Gunter, Jr. Charles D.
Walton George L.
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