Fluid handling – Systems – Flow path with serial valves and/or closures
Reexamination Certificate
1998-10-27
2001-02-06
Ferensic, Denise L. (Department: 3753)
Fluid handling
Systems
Flow path with serial valves and/or closures
C137S613000
Reexamination Certificate
active
06182696
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to valves, and relates more specifically to dual-isolation valves.
BACKGROUND OF THE INVENTION
Valves are common components of almost any piping system. Although they can be constructed in many different configurations and sizes, a typical valve will include a few basic elements. These include: a valve body that houses internal components within an internal cavity; inlet and outlet ports leading to and from the valve body; one or more valve members positioned within the cavity of the valve body with passageways for fluid flow; inlet and outlet seats that seal the contact points between the inlet and outlet ports and the valve member(s); and a valve stem or other structure or mechanism that extends outside the cavity for turning the valve member(s) within the valve body cavity. These components are attached such that fluid entering the valve through the inlet pipe is either allowed to flow through the valve member to the outlet pipe or prevented from such flow based on the orientation of the valve member passageway relative to the valve body.
One specialized valve configuration is the “dual isolation” valve (sometimes also referred to as a “double block-and-bleed” valve), which includes a pair of valve members positioned in series within the valve cavity. Dual isolation valves are typically employed in piping systems in which any leakage through the valve when closed would be extremely detrimental, if not catastrophic. Exemplary uses. include situations in which (a) two very volatile materials are separated by the valve, (b) a downstream operator is protected by the valve, (c) cross-contaminination of two materials is prevented by the valve, and (d) potable and nonpotable water streams are separated by the valve.
An example of a dual isolation valve is illustrated in U.S. Pat. No. 5,669,415 to Trunk (the Trunk valve). The Trunk valve has two frustoconical plugs, each of which is inverted (i.e., the narrower end of the plug extends upwardly). Of course, the volumetric flow of the valve is dependent on the size and shape of passageways in the plugs; however, the size of the passageways is limited by the size of the plug itself, as sufficient structure must surround the passageway to prevent the plug from fracturing or collapsing during use. Typically, and as illustrated in Trunk, valves having frustoconical plugs include trapezoidal flow passageways in the plugs that match the trapezoidal cross-sectional shape of the plugs in an effort to maximize the cross-sectional surface area of the passageway.
Some dual isolation valves having two frustoconical plugs are configured such that one plug is inverted as described above and the other is not (i.e., the narrower end of the plug extends downwardly). This configuration (exemplified in British Patent No. GB 2 305 713 B) is employed in an attempt to reduce the cavity volume and overall length of the valve; because the plugs are oriented 180 degrees apart about the flow axis, they can be positioned closer together without interfering with one another than is the case for identically oriented plugs.
Unfortunately, the reverse orientation of one plug within a dual isolation valve can create reduction in volumetric flow when trapezoidal cross-section flow passageways are employed. Because the perimeters of the flow passageways are not aligned with each other (as can be the case for dual isolation valves like the Trunk valve), a fluid flowing through the valve is redirected somewhat from its flow path, thereby increasing the turbulence in the flow and reducing flow efficiency. This shortcoming has led to some valves having aligned circular flow passageways; however, such passageways provide less cross-sectional area for flow and, thus, also suffer from reduced volumetric flow.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a dual isolation valve with plugs that are oriented 180 degrees apart from each other about the flow axis, but which do not suffer from considerably reduced volumetric flow.
It is also an object of the present invention to provide such a valve with high flow efficiency.
These and other objects are satisfied by the present invention, which is directed to a dual isolation valve with improved flow characteristics. The dual isolation valve comprises: a valve body with opposed inlet and outlet ports that defines an inner cavity; a first valve member; and a second valve member. The first valve member (preferably a frustoconical plug) has a narrower first end and a wider second end and is rotatably mounted within the valve body cavity for rotation about a first axis of rotation substantially perpendicular to the flow axis defined by the inlet and outlet ports. The first valve member includes a substantially rectangular flow passage. The first end of the first valve member extends away from the second end along the first axis of rotation in a first direction, and the first valve member is rotatable between an open position, in which the flow passage is oriented to be generally aligned with and located on the flow axis to enable fluid entering the inlet port to pass through the flow passage, and a closed position, in which the flow passage is oriented to be generally perpendicular to the flow axis to prevent fluid entering the inlet port from passing through the flow passage. The second valve member also has a narrower first end and a wider second end and is rotatably mounted within the valve body cavity for rotation about a second axis of rotation substantially perpendicular to the flow axis. The first end of the second valve member extends away from the second end along the second axis of rotation in a second direction opposite the first direction (such that the first and second valve members are oriented in opposed directions). The second valve member, which also has a substantially rectangular flow passage, is rotatable between an open position, in which the flow passage is oriented to be generally aligned with and located on the flow axis to enable fluid exiting the first valve member to pass through the flow passage to the outlet port, and a closed position, in which the flow passage is oriented to be generally perpendicular to the flow axis to prevent fluid exiting the first valve member from passing through the flow passage to the outlet port. In this configuration, the flow of fluid through valve can be disturbed less than with prior art dual isolation valves while permitting extensive flow through the valve.
In a preferred embodiment, the flow passageways are constructed such that their perimeters are substantially aligned along the flow axis. In this configuration, fluid flow is typically disturbed no more than for prior art valves having circular passageways; however, the volume of flow can be greater than for circular passageway valves because the rectangular shape of the passageways permits greater flow volume.
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Rainwater Edward L.
Spears Ricky E.
Ferensic Denise L.
Kim Joanne Y.
Myers Bigel & Sibley & Sajovec
Nordstrom Valves, Inc.
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