Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-03-23
2001-06-12
Fox, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C251S127000
Reexamination Certificate
active
06244297
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fluid energy dissipation devices and, more particularly, to anti-cavitation fluid pressure reduction devices including multiple stacked plates for liquid flows.
BACKGROUND OF THE INVENTION
Fluid pressure reduction devices are commonly used in valves. One well-known type of fluid pressure reduction device includes a stack of annular disks mounted within a fluid control valve. The stack of disks, often referred to as a “valve trim” or a “valve cage”, defines a plurality of flow passages between a hollow center and an outer periphery. A valve member is movable through the hollow center to connect more or fewer of the flow passages between the valve inlet and outlet. Such devices have utilized changes in flow direction and increases in the cross-sectional area of the flow passages to reduce pressure. However, prior art fluid pressure reduction devices have not effectively applied the principles of fluid mechanics to the design of the fluid flow passages to prevent the static head from reaching the vapor pressure of the fluid, while achieving substantial pressure reduction.
A stacked valve trim which uses identical hole patterns and which creates a diagonal radial flow path is described in U.S. Pat. No. 3,529,628, issued Sep. 22, 1970 to Cummins. However, the openings in the disks were highly irregular and created between them an unpredictable resistance path. The flow paths were not designed using effective principles of fluid mechanics. Furthermore, Cummins disclosed no way to pressurize the annular area between the plug and the annular bore to avoid damage between a radial pressurized path and the next unpressurized path.
U.S. Pat. No. 4,125,129, issued Nov. 14, 1978 to Baumann also discloses a multi-plated valve trim with identical annular disks, which when angularly offset, create a vertical flow path, as shown in FIG.
14
.
FIGS. 18 and 19
also show identical plates which are angularly offset from each other to form a vertical flow path. However, using round holes as throttling orifices greatly reduces the flow capacity and creates a high amount of contraction due to the sharp entrances to the holes, leading to excessive pressure recovery. Similar identical plates selectively overlapped and having radial, rectangular flow slots for throttling in the horizontal direction and in one plane are disclosed in U.S. Pat. No. 4,356,843, issued Nov. 2, 1982 to Baumann.
U.S. Pat. No. 5,769,122, issued Jun. 23, 1998 to Baumann et al. discloses fluid pressure reduction devices including plates having restrictions with streamlined inlets followed by long and wide settling chambers after each contraction and providing radially outward flow paths in two planes. The configuration shown in
FIGS. 10 and 11
and orifices
62
shown in
FIG. 7
, for example, permit a gradual decrease in velocity, corresponding to high pressure recovery, which may be suitable for gases in order to obtain supersonic velocities, but is detrimental for liquids which are prone to cavitate. The '122 patent also teaches several restrictions within one horizontal plane, allowing for unhindered pressure recovery of at least 50%.
U.S. Pat. No. 5,687,763, issued Nov. 18, 1997 to Steinke discloses a fluid flow control device having tortuous turns within radial flow paths created between openings of a pair of identical plates. The pressure drop is created through abrupt turns rather than by the use of orifices. Furthermore, there is no provision for gradual pressure reduction along the gap between the valve plug and the cage bore.
All of the known prior art fluid pressure reduction devices have exhibited one or more disadvantages, including but not limited to cavitation, insufficient pressure reduction, failure to provide for gradual pressure reduction along the gap between the valve plug and the cage bore, low flow capacity and difficulty in manufacturing. Accordingly, there is a need for new and improved fluid pressure reduction devices.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, a fluid pressure reduction device is provided. The fluid pressure reduction device comprises a stack of annular plates having a hollow center, a fluid inlet at a first perimeter thereof and a fluid outlet at a second perimeter thereof. Selected ones of the plates each define at least one pressure reduction stage comprising an orifice having a well-rounded or well-tapered inlet and an abrupt discharge, and a communication passage coupled to the discharge. Each pressure reduction stage communicates with another pressure reduction stage in an adjacent one of the annular plates in the stack. Two or more of the pressure reduction stages are coupled in series to define a pressure reduction flow path from the fluid inlet to the fluid outlet.
The fluid pressure reduction device is used with a movable plug engaged within the hollow center. The annular plates preferably define at least one axial flow path through the stack for a gradual reduction of fluid pressure at different axial levels in the stack of annular plates. The axial flow path may open onto the hollow center of the stack of annular plates or may be located radially outwardly of the hollow center.
In one embodiment, the pressure reduction flow path is defined by a plurality of pressure reduction stages in series, and includes radial and axial flow components which alternate between adjacent plates in the stack of annular plates. The stack of annular plates preferably defines two or more pressure reduction flow paths in parallel. In another embodiment, the pressure reduction flow path is defined by a plurality of pressure reduction stages in series, and includes radial and axial flow components through successive plates in the stack of annular plates. The stack of annular plates preferably defines two or more pressure reduction flow paths in parallel. In this embodiment, the number of annular plates defining each pressure reduction flow path is equal to the number of pressure reduction stages in the pressure reduction flow path.
The number of orifices and/or the flow areas of the orifices discharging into the communication passage may increase along the pressure reduction flow path. Preferably, the annular plates define a plurality of pressure reduction flow paths in parallel between the fluid inlet and the fluid outlet. Preferably, each pressure reduction stage is characterized by a velocity head loss greater than 75% and by a corresponding pressure recovery of less than 25%. Preferably, the communication passage has a width that is at least 3.5 times the width of the orifice. Where two or more orifices discharge into a single communication passage, the communication passage preferably has a width that is at least 3.5 times the combined widths of the orifices.
According to another aspect of the invention, a fluid control valve is provided. The fluid control valve comprises a valve body having a fluid passageway, a valve seat in the fluid passageway, a valve plug that is movable with respect to the valve seat for controlling the flow of fluid through the fluid passageway, and a fluid pressure reduction device mounted in the fluid passageway for reducing fluid pressure. The pressure reduction device is configured as described above.
REFERENCES:
patent: Re. 31105 (1982-12-01), Bates, Jr.
patent: Re. 32197 (1986-07-01), Self
patent: 1243134 (1917-10-01), Binckley
patent: 1650196 (1927-11-01), Demuth
patent: 2126991 (1938-08-01), Griswold
patent: 3133557 (1964-05-01), Gongwer
patent: 3316936 (1967-05-01), Gongwer
patent: 3323550 (1967-06-01), Lee, II
patent: 3375855 (1968-04-01), Deeks
patent: 3513864 (1970-05-01), Self
patent: 3514074 (1970-05-01), Self
patent: 3529628 (1970-09-01), Cummins
patent: 3532126 (1970-10-01), Boothe
patent: 3631891 (1972-01-01), Brumm
patent: 3678963 (1972-07-01), Betts et al.
patent: 3688800 (1972-09-01), Hayner et al.
patent: 3722854 (1973-03-01), Parola
patent: 3780767 (1973-12-01), Borg et al.
patent: 3802537 (1974-04-01), White
patent: 3813079 (1974-05-01), Baumann et al.
patent:
Fisher Controls International Inc.
Fox John
Wolf Greenfield & Sacks P.C.
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