Fluid handling – With cleaner – lubrication added to fluid or liquid sealing... – Cleaning or steam sterilizing
Reexamination Certificate
2002-12-20
2004-12-21
Walton, George L. (Department: 3753)
Fluid handling
With cleaner, lubrication added to fluid or liquid sealing...
Cleaning or steam sterilizing
C073S001720, C134S16600C, C137S240000, C137S312000, C137S625220, C137S625470, C251S315120, C251S315130
Reexamination Certificate
active
06832621
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to flow control valves of the quarter-turn ball valve type, and more particularly, to ball valve assemblies used in isolating electronic level transmitters operatively connected to fluid storage tanks.
BACKGROUND OF THE INVENTION
Electronic liquid level transmitters are utilized extensively with fluid storage tanks in the chemical and pulp and paper industries to monitor the volume of fluid contained in a tank. Liquid level transmitters have diaphragm faces that are placed in fluid communication with the bottom of a fluid storage tank, which measure the head pressure caused by changes in the liquid level and transmit an electronic output signal proportional to the measured head pressure. The output signal produced by an electronic level transmitter is then used to monitor the liquid level and volume in the storage tank or the density of the material stored in the tank where the volume of material in the tank has been determined by another means. In many manufacturing environments, level transmitters provide a continuous level indication that is one of several variables monitored in a complex process control system. For such systems, maintaining the level transmitter in proper working order is critical to maintaining safe and normal process operations. Reliable and accurate electronic level transmitters are relied upon to avoid hazardous and costly operational upsets, such as tank overflows.
Electronic level transmitters are typically of the flange-mounted type, which connect to outlet piping located at or near the bottom of a fluid storage tank. In many cases, liquid storage tanks are provided at the bottom with a three inch pipe and flanged outlet for attaching the level transmitter. Such flange-mounted transmitters are therefore typically sized for use with three inch outlet piping, and a three inch, class 150 ANSI pipe size flange connector. The level transmitter may be provided with a diaphragm face for sensing the liquid head pressure that is flush mounted to the flange, that is, a planar diaphragm face mounted flush with gasket surface of a three inch, class 150 ANSI flange.
A transmitter isolation valve is required between the tank outlet piping and the level transmitter to allow the transmitter to be removed without having to drain the tank or otherwise disrupt process operations, such as for repairs, cleaning, re-calibrating or replacement of the transmitter. One of the largest users of level transmitters is the pulp and paper industry, and it is well known in the prior art to utilize three-inch sized knife gate valves for transmitter isolation. For this application, level transmitters of the knife gate type have the benefit of being narrow-body, which allows the isolation valve to be mounted as close to the liquid storage tank as possible. This saves valuable space in crowded manufacturing environments and provides for greater access to the transmitter for maintenance workers and equipment. Additionally, storage tanks in the pulp and paper industry are often used to store aqueous liquids that contain varying degrees of sedimentation and pulp fibers that settle at the bottom of storage tanks. Level transmitters mounted closely to a storage tank eliminate excess piping space for the buildup of sediment and pulp fibers.
But there are many limitations associated with the use of transmitter isolation valves of the knife gate type. For instance, because these valves are mounted close to the storage tanks to which they are operatively connected, there is not enough room to utilize a typical round handwheel to open and close the valve. To open and close such valves, operators are required to rely on a ratchet-type device with a piece of pipe, or ratchet wrench, as a handle. This requires an excessive number of strokes of the handle to open and close the valve. On account of the corrosive nature of the fluids utilized with these valves, another limitation is the valves often corrode and fail to function effectively. An additional limitation of knife gate valves is difficulty associated with preventing leakage through the gate seat area because the valve stays open for long periods of time.
Additional difficulties associated with the use of knife gate transmitter isolation valves pertain to the manner in which the gate, or blade, of the valve must be sealed as it extends and retracts through the packing gland during use. Because of the wide, flat, and thin dimensions of typical blades, as well as the blades having four sharp and square corners, the pressing of the packing material against the blade to prevent leakage from the valve into the atmosphere can be problematic. For instance, tightening the packing gland of such valves can render the valve inoperable due to excessive levels of force being required to move the blade up or down. Loosening the packing gland to allow the valve to readily open and close may result in the problem of external leakage. As the result of increasingly stringent leak prevention performance standards for industrial valves issued by such agencies as the Environmental Protection Agency (EPA) and Occupational Health and Safety Administration (OSHA), these problems have become more significant and costly.
On account of the limitations of knife gate valves for use in isolating level transmitters, valves of the ball valve type have begun being used in this service. These valves are quarter-turn valves wherein an internally mounted ball member rotates between a ninety degree arc to open or close the valve. These valves are typically teflon-seated to allow for leak-tight shutoff and are manufactured of stainless steel, hastelloy, or titanium for corrosion resistance. There has been a reluctance to accept valves of the ball valve type as a suitable replacement for knife gate valves. One reason is in order to be a direct replacement for narrow knife gate valves, conventional ball valves for use in isolating transmitters have had narrow flow-through ports in conjunction with a recess machined into the transmitter side of the valve body to provide a three inch sensing area for the diaphragm of the level transmitter. Narrow flow-through ports increase the likelihood that the isolation valve will be plugged by sedimentation and pulp fibers, creating operating problems. Further, there is a need to provide conventional transmitter isolation valves of the ball valve type with improved backflushing means, which would reduce the need for costly removal of the level transmitter for maintenance or replacement of the level transmitter.
From the foregoing it may be seen that heretofore, no one has adequately provided a ball valve for use in isolating level transmitters. A need exists for a corrosion resistant, quarter-turn ball valve for use in isolating a level transmitter that provides bubble-tight shutoff, that may be easily installed as a replacement for knife gate or other flanged valves and that addresses the limitations of the prior art transmitter isolation valves of the knife gate and ball valve type.
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide an improved ball valve which is superior to those presently used to isolate electronic level transmitters.
A further object of the present invention is to provide a transmitter isolation ball valve that provides means for flushing the diaphragm face of an electronic level transmitter operatively connected thereto.
Another object of the present invention is to provide a transmitter isolation ball valve having a full port for enhancing the accuracy of level transmitter readings and the backflush capabilities of the valve.
A still further object of the present invention is to provide a transmitter isolation ball valve that may be readily used for replacing transmitter isolation valves of the knife gate type.
Another object of the present invention is to provide a transmitter isolation valve having means for flushing the diaphragm face of a level transmitter when the valve is in an open position and means for calibrating the level
Bush Kenneth M.
Bush IP Law Group, LLC
Trans-Valve, Inc.
Walton George L.
LandOfFree
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