Tank bottom diaphragm valve

Abstract: A diaphragm valve which mounts directly on a tank bottom provides positive isolation between the vessel and downstream piping. When closed, the diaphragm seals against the valve body weir to seal the valve, and when opened, the valve provides a smooth, crevice free, drainable passageway to the downstream piping.

Description: Background of the Invention This invention relates to diaphragm valves, and more particularly to diaphragm valves which are designed to mount to tank bottoms of sterile vessels. Similar devices include ball valves, quarter turn valves which have a ported sphere and a pair of seats in a housing. When open, fluid flows from one end of the valve through the ball and out the other end. Rotating the ball 90 degrees closes the valve and prevents fluid flow. The ball may be fixed or floating Plunger valves are linear motion valves which create a seal by forcing an elastomeric boot into a seat area. When the valve opens, the boot convolutes on itself to provide fluid flow. A ram valve is a linear motion valve which consists of a spindle/ piston combination. The seal is typically metal to metal. Another linear motion valve similar to a ram valve is the kettle valve, but a molded elastomer seal, mushroom shaped, is on the end of the shaft. The foregoing valves are not ideally suited to process fluids in the pharmaceutical/bioprocessing industries. These valves have many limitations including too large in size, they generate a large sump at the vessel bottom and generate crevices in which bacteria can grow, they trap fluid in ball cavity which requires cavity fillers and steam ports to clean, they have poor interior finish and have non-streamlined fluid passages, they do not isolate the working parts from the line fluid, they do not provide positive closure and are not autoclavable, and they contain welds, i.e. mounting flange is normally welded to valve body. The state of the art of diaphragm valves are known from the following U.S. patents: 1,497,275 3,250,511 2,186,833 3,349,795 2,605,991 3,623,700 2,616,164 3,628,770 2,725,211 3,631,882 2,892,613 4,505,451 3,134,286 4,596,268 3,134,571 The state of the art for valves used in connection tanks are known from the following U.S. patents: 2,679,860 3,665,946 3,895,651 3,918,678 4,836,236 In addition WO-A-9014539 shows a valve body for fixedly attaching to a tank bottom, having a drain thru passage and exit passage with a transverse weir there between and means angularly mounted with respect to said drain thru passage for movement of a diaphragm and away from said weir to effect closure and opening of said drain thru passage. The problem here is the occurrence of zero pockets which prevent a total drainage. The tank bottom diaphragm valve according to the invention overcomes the problems by employing the inherent design features of the diaphragm valves which include positive closure, zero pockets, minimal contact surfaces, streamlined fluid passage, bonnet isolation, and ease of maintenance. The tank bottom diaphragm valve of the invention provides a clean, totally drainable means to isolate the vessel from downstream process piping, and the overall dimensional envelope is minimal and all materials of construction are FDA compliant and autoclavable. Summary of the Invention : An object of the invention is to provide a tank bottom diaphragm valve which mounts directly on a tank bottom and provides positive isolation between the vessel and downstream piping with minimal dead space. According to the broader aspects of the invention when closed, an elastomer or plastic diaphragm seals against a body weir contour to seal the valve. Opening the valve creates a smooth, crevice free passageway to downstream piping. The valve is drainable, which prevents contaminants resulting from trapped fluids. A feature of the invention is that the valve body/flange is one piece, machined from either bar stock or a forging, and can be welded directly to the tank. Other designs are multi-piece, using bolted fasteners or weldments. The elimination of additional welds improves the valve body integrity and reduces sources of contamination. The diaphragm seal area is very close to the bottom of the tank and a smooth transition insures proper solution mixing. Brief Description of the Drawings : Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims, and the accompanying drawings in which: Fig. 1 is a cross-sectional view of the tank bottom valve in the open position; Fig. 2 is a cross-sectional view of the tank bottom valve shown in Fig. 1 in the closed position; Fig. 3 is a top view of the valve body; Fig. 4 is a cross-sectional view of the valve body of Fig. 3 taken along lines A-A; and Fig. 5 is a bottom view of the valve body as viewed from lines B-B of Fig. 4. Detailed Description of the Embodiment : Referring to Fig. 1, a diaphragm valve designed to mount in a tank bottom 10 is illustrated. The stainless steel valve body 11 is normally welded about its periphery 11a to the tank bottom. A tube extension 12 which may include a flange 12a is welded at the buttweld lip, point 11b at the exit passage 11c. In addition to the valve body 11, the diaphram valve includes a elastomer or TFE diaphragm 13, a steel or stainless steel finger plate 14, a zinc, iron, or coated iron compressor 15, a stainless steel pin 16, a steel or stainless steel thrust bearing 17, a steel or stainless steel set screw 18, an iron, or coated iron handwheel 19, a stainless steel spindle 20, a plastic shim washer 21, a brass or stainless steel bushing 22, and a bonnet 23 made of iron, coated iron, bronze, steel, or stainless steel. Bonnet 23 is fixed to the valve body 11 by studs and nuts (not shown) in a normal manner. Typical coating materials are nylon and PVDF. Turning of hand wheel 19 will cause movement of spindle 20 along axis 25. Referring additionally to Fig. 2, the spindle 20 has moved the diaphragm 13 into a closed position in which the diaphragm 13 closes against concave seat 11d to close drain thru passage 11f. Although a hand wheel is shown, other means such as pneumatic or electrical actuators may be used to move the spindle. Referencing Fig. 3, it can be seen that the drain thru port centerline 11g is as close to the body centerline 11h as possible This minimizes the dead space from the tank bottom to the valve diaphragm seal. In many tank applications, the fluid must be continually mixed and kept in solution. A minimum dead space is crucial to insure continuous mixing. The valve body must have a smooth, crevice-free exit passageway. Figure 4 shows several key geometry relationships which exist in the valve body. Centerline 26 of exit port 11c is perpendicular to axis 25. A typical tank bottom has a slope angle of 15 to 20 degrees and the valve body angle 11i matches this slope to insure a smooth transition from the tank to valve body as shown in Figs. 1 and 2. A second transition (11j) occurs on some valve sizes to blend the valve body toward the diaphragm seal area. This reduces the vertical dead space and insures proper mixing of process fluid within tank. Drainability is the key to a successful tank valve application and the valve body is designed to insure drainability. The body's bonnet mounting face 11k has an angular relationship to the top planar surface 11m. The angular relationship is established from a combination of the valve stroke and diaphragm geometry in the open position. In the preferred embodiment angle ϑ is approximately 30 degrees from the horizontal plane which is parallel to surface 11m. The orientation is such that the surface 13a of diaphragm 13 at its lowest point (shown in Fig. 1) in the full open position is equal to or higher than the high point of the connection surface 11e to the downstream passage 11c. It is of great importance that no pockets exist in which fluids can be trapped. Also, the valve minimum wall thicknesses must insure adequate strength to withstand pressure up to 150 PSI within the tank. Also critical to the design of the body are the drain passages. The passage 11f from tank to valve and the passage 11c from the valve to downstream piping must be sufficiently large so as not to restrict flow. A tank must drain quickly to avoid rings in the tank on which contamination can grow. Another feature of the valve body is the ability to have a buttweld tube extension 12, tri-clamp, or other end available on the downstream side. The body 11, being unitary and cylindrical in shape, may be welded to the tank bottom throughout a 360 degree potential rotation to accommodate the downstream piping. Fig. 5 shows a bottom view of the valve taken along lines B-B of Fig. 4. It shows the valve body 11 less the bonnet and diaphragm assembly. The tank drain passage 11f, the weir centerline 25, centerline 26 of exit passage 11c which connects to the downstream piping are illustrated. The bonnet mounting face 11k has a plurality of tapped holes 27 for mounting the bonnet.

Claims: A diaphragm valve for a tank bottom comprising: a valve body (11) for fixidely attaching to said tank bottom (10), said body having a drain thru passage (11f) and exit passage (11c) with a transverse weir there between; means angularly mounted with respect to said drain thru passage (11f) of said body (11) for movement of a diaphragm (13) against and away from said weir to effect closure and opening of said drain thru passage (11f); characterised in that said diaphragm (13) in an open position, away from said weir, has its lowest surface point equal to or higher than the high point of the connection surface (11e) to the exit passage (11c). A diaphragm valve according to claim 1, wherein said means for movement of said diaphragm (13) is isolated from said drain thru passage (11f) by said diaphragm. A diaphragm valve according to claim 1, wherein said valve body (11) is a unitary formed body in which the surface mounted to the tank body (10) is at an angle of approximately 30 degrees with respect to the surface for mounting said means (20) for movement of said diaphragm (13). A diaphragm valve according to claim 3, wherein said body (11) having a first planar surface for securing to said tank bottom (10) and a second planar surface formed at an angle to said first surface and a bonnet (23) being secured to said second surface and having mounted therein compressor means (15); A diaphragm valve according to claim 1 wherein the axis (11h) of the drain thru passage (11f) is perpendicular to said first surface. A diaphragm valve according to claim 5, wherein the axis (26) of said exit passage (11c) is angularly displaced with respect to the axis (11h) of the drain thru passage (11f). A diaphragm valve according to claim 1 wherein said angle is approximately 30 degrees. A diaphragm valve according to claim 1 wherein the drain thru passage (11f) has an initial slope of approximately 15 to 20 degrees from said first surface. A diaphragm valve according to claim 1, wherein a tube extension (12) is welded to said body (10) at the exit passage. A diaphragm valve according to claim 1, wherein said drain thru (11f) has an axis (11h) perpendicular to said tank bottom (10). A diaphragm valve according to claim 1, wherein the axis (26) of said exit passage (11c) is perpendicular with respect to the axis (25) of said means (20). A diaphragm valve according to claim 1, wherein the drain thru passage (11f) has an initial slope of approximately 15 to 20 degrees from said first surface. A diaphragm valve according to claim 12, wherein a secondary slope greater than said initial slope is provided.

Inventors: BUTLER RONALD G, HOUCK WAYNE R, RANDALL RICHARD D, BUTLER, RONALD G., HOUCK, WAYNE R., RANDALL, RICHARD D.
Applicants: ITT, ITT INDUSTRIES, INC. (A DELAWARE CORPORATION)
Application year: 1992
Main classification: F16K51
IPC codes: F16K7, F16K51