NON-RISING STEM VALVE ASSEMBLY AND METHOD OF REPLACING A PERMANENT SEAL

Abstract: A non-rising stem valve assembly (2) is disclosed including a valve body (4) having an inlet (3) and an outlet (5) and is capable of accommodating a non-rising stem valve (14). The non-rising stem valve includes a bonnet member (8) securely attached to the valve body (4) and forms a tubular passageway. A valve stem (14) extends through this tubular passageway and has a lower valve portion (20) axially displacable relative thereto, with the lower valve portion (20) being positioned between the inlet (3) and outlet (5). A retaining ring (16) is provided for securing the valve stem (14) against inward movement relative to the bonnet member (8) and an inwardly projecting flange on the bonnet member is provided for securing the valve stem against outward movement relative to the bonnet member. A packing nut (24) is removably secured to the bonnet member for sealing the valve assembly. The packing nut has an interior surface and an exterior surface with a first O-ring seal (26) being provided on the interior surface and a second O-ring seal (28) being provided on the exterior surface. A third axially displacable seal (36) is provided which rests on an upper surface of the lower valve portion (20) and is axially movable with the lower valve portion. The first and second O-ring seals form permanent seals and seal the valve assembly during normal use, while the third seal forms a temporary seal which may be selectively formed between the valve stem and the bonnet member for temporarily sealing the valve assembly and, allowing the permanent seals to be replaced when necessary without decommissioning the valve assembly. A method of replacing the permanent seals is also disclosed.

Description: This invention relates to a non-rising stem valve assembly as set forth in the preamble of claim 1 for use in a fluid distribution system, and more particularly this invention relates to a novel non-rising stem valve which facilitates the replacement of the valve stem seal without the need of decommissioning the valve. Non-rising stem valves for use in distribution systems are known in the prior art. These non-rising stem valves are provided with a stem packing which, by compression and internal pressure, effects a seal and contains the product under pressure therein. To replace this stem packing, the valve and the subsequent distribution system must be taken out of service to avoid any major loss of product. One solution to the problem of downtime is set forth in US-A-3,912,221 to Fenster et al issued on October 14, 1975, which discloses a stem seal and retainer for a gate valve. This gate valve is of the non-rising type with a seal being provided between the stem and bonnet of the valve. A cartridge type seal unit is held in place by the operating nut and the stem and gates are held in the raised position by a snap ring. The cartridge type seal unit may be removed by removing the operating nut and lifting out the seal cartridge. The non-rising valve described above includes a secondary seal to prevent loss of product while the primary seal is being replaced. This allows the primary seal to be replaced while the valve is in the operating condition. This redundant secondary O-ring seal is continuously in effect by way of compression between the non-rising stem and the bonnet, and internal pressure exerted by the product line. These forces which continuously act on the secondary O-ring seal subject this seal to constant wear during the opening and closing of the valve, and when such secondary seal requires replacement due to the stresses which are continuously applied thereto, the valve and distribution system must be decommissioned to avoid loss of product during this replacement. GB-A-546,772 and EP-A-355,301 describe improvements on the above form of valve assembly as acknowledged in the preamble of claim 1 herein, but they do not fully attain the aim of the present invention which is to provide a non-rising stem valve assembly wherein replacement of sealing means may be accomplished without the decommissioning of the non-rising stem valve and the associated distribution system. According to the present invention, this aim is achieved through the features set forth in the characterised portion of claim 1. A non-rising stem valve assembly incorporating the features of claim 1 can be retrofitted into already-existing valve bodies. In one particular stem valve assembly according to the invention, a non-rising stem valve assembly includes a valve body having an inlet and an outlet that is capable of accommodating a non-rising stem valve. The non-rising stem valve includes a bonnet member securely attached to the valve body which forms a tubular passage way. A valve stem extends through this tubular passageway and has a valve closure member axially displacable relative thereto, with the valve closure member being positioned between the inlet and outlet. A retaining ring is provided for securing the valve stem against inward movement relative to the bonnet member and an inwardly-extending radial flange is provided for securing the valve stem against outward movement relative to the bonnet member. A packing nut is provided for sealing the valve assembly. The packing nut has an interior surface and an exterior surface with a first O-ring seal being provided on the interior surface and a second O-ring seal being provided on the exterior surface. A third axially displacable seal is provided which rests on an upper surface of the valve closure member and is axially movable with the valve closure member. The first and second O-ring seals form permanent seals and seal the valve assembly during normal use, while the third seal forms a temporary seal. This temporary seal may be selectively formed between the valve stem, the bonnet member and the valve closure member for temporarily sealing the valve assembly. This allows the permanent seals to be replaced when necessary without decommissioning the valve assembly. This third seal is not under compression during normal operation of the valve assembly but is only compressed when the valve closure member is drawn upwardly and backseated to compress the third seal against the bonnet. Two valve assemblies in accordance with the invention are illustrated in the accompanying drawings by way of example. In the drawings: Figure 1 is a sectional elevational view of one form of non-rising stem valve assembly according to the present invention, in a normal open operating condition; Figure 2 is a sectional elevational view of the non-rising stem valve assembly of Figure 1 in the replacement position; and Figure 3 is a sectional elevational view of a non-rising stem valve assembly according to a second embodiment of the present invention. Referring to Figures 1 and 2, there is shown a valve assembly 2 including a valve body 4 and a valve assembly 6. The valve body has valve ports 3 and 5, and the flow of fluid or other material between these valve ports is controlled by the valve assembly 6. The valve body also includes an internally threaded valve receiving opening 7 which is longitudinally aligned with the valve port 3. The valve assembly 6 includes a bonnet 8 having external threads 10 thereon which cooperate with internal threads 12 of the valve receiving opening 7 to secure the valve assembly 6 therein. A non-rising valve stem 14 passes through a central opening 11 in the bonnet 8 and is rotatable relative to the bonnet but maintained in a fixed axial position by a retaining ring 16. The non-rising valve stem 14 is provided with an externally threaded lower end portion 18 which cooperates with a separate, internally threaded valve closure member 20. The lower end portion 18 is threaded into a central threaded passage 21 in the valve closure member 20; the cooperating threads being indicated in broken lines at 23. The valve closure member 20 is non-rotatably maintained within a lower open end 25 of the bonnet 8 and is axially movable relative to the non-rising valve stem upon rotation of the valve stem 14. Rotation of the valve closure member is prevented by a key and groove arrangement with the bonnet at 27, or by any known means found in the art. The valve closure member 20 is additionally provided with a disc seal 22 embedded in its lower portion which engages a seat 29 in the valve body to close the port 3 when the valve assembly 2 is in a closed or shutoff condition. A packing nut 24 having a central opening 31 through which the non-rising valve stem 14 passes, is provided for forming a replacable packing seal between the bonnet 8 and the non-rising valve stem 14. The packing nut is threaded into an open end 33 of the bonnet 8, and the non-rising stem valve passes through the packing nut and into the bonnet. The replacable packing seal includes first and second O-ring seals 26, and 28. The first O-ring seal 26 is accommodated within a recess 30 on the internal surface of the packing nut 24, thereby forming a fluid-tight seal between the non-rising stem valve 14 and the packing nut 24. The second O-ring seal 28 is provided on the external surface of the packing nut 24 within a recess 32 provided therein. This second O-ring seal 28 forms a second fluid tight seal between the bonnet 8 and the packing nut 24. The packing nut 24 is threadedly secured within the bonnet 8 by threads 34 so as to compress the O-ring 28 between the packing nut 24 and the bonnet 8. The first O-ring seal 26 is subjected to stress during the opening and closing of the valve due to the rotation of the stem 14. Because of such stress, periodic replacement of O-ring seal 26 is required. In order to replace the O-ring seal 26 without decommissioning the valve, a resilient washer 36 is provided around the valve stem 14 and between the valve closure member 20 and the bonnet 8. The washer 36 rests on an upper portion 35 of the valve closure member 20 and upon rotation of the valve stem 14, and the complete raising of valve closure member 20 to a backseated position, the washer contacts a flange 38 of the bonnet 8, and is compressed to form a temporary seal between the valve stem 14, the valve closure member 20 and the bonnet 8, as shown in Figure 2. With the valve closure member 20 in the completely raised state and the washer 36 forming the temporary seal, a bolt 40 threaded into the upper end of the valve stem may be removed and a knob 42 which it holds may be lifted off to gain access to the packing nut 24. Since the temporary seal is made, the packing nut 24 can be removed and the O-ring 26 replaced without the loss of any product nor the need to decommission the valve itself for any period of time. During normal operation of the valve assembly 2, the resilient washer 36 is not compressed or subjected to internal fluid pressure which would cause the washer to wear and require replacement. Rotation of the stem 14 by the knob 42 in one direction causes the valve closure member 20 to move upwardly due to the threads 23 and to move the disc seal 22 away from the seat 29 to open the valve. However, to open the valve, there is no need to rotate the valve stem 14 until the valve closure member 20 moves all the way to the backseated position where the washer 36 is engaged and compressed. This never occurs during normal valve operation. To close the valve, the valve stem 14 is rotated in the opposite direction until the disc seal 22 engages the valve seat 29. Illustrated in Figure 3, is a variation of the valve disclosed above with reference to Figures 1 and 2, but the principle of its use is identical. Like reference numerals will be used in Figure 3 for structural elements which are identical in structure and function to those shown in Figures 1 and 2. The valve of Figure 3 includes a valve stem 14 having a radially extending flange 44 positioned below the flange 38 of the bonnet 8. Therefore, when the valve closure member 20 is completely raised, the resilient washer 36 contacts flange 44 and is compressed to form a temporary seal between the valve stem 14 and the bonnet 8. The combination of the flange 38 and flange 44 positively prevents the valve stem 14 from rising relative to the bonnet 8.

Claims: A non-rising stem valve assembly (6) comprising a bonnet (8) adapted for attachment to a valve body (4), the bonnet (8) including an upper end, a lower end and a central passageway (11) extending through the bonnet (8) between the upper and lower ends thereof, a non-rising valve stem (14) extending through the upper end of the bonnet (8) into the passageway (11) and having a stem lower end (18) with means for securing the valve stem (14) within the bonnet (8) for rotational movement but against axial movement, a replaceable permanent seal means (26, 28) between the bonnet (8) and the valve stem (14), a valve closure member (20) and means mounting that valve closure member (20) on the stem lower end (18) for axial movement relatively to the valve stem (14) between a valve closed position and a valve open position and between the valve open position and a backseat position, the backseat position being closest to the upper end of the bonnet, the valve closure member (20) having an upper extremity (35) which extends into the passageway (11) at the lower end thereof and a lower extremity for movement outwardly beyond the lower end of the bonnet, characterised in that a sealing means (36) is positioned at the upper extremity (35) of the valve closure member (20) between the valve stem (14) and the bonnet (8), the sealing means (36) being normally uncompressed and in non-sealing engagement with the bonnet (8) when the valve closure member (20) is in the valve closed and valve open positions but being compressed into simultaneous sealing engagement with the bonnet (8), the valve stem (14) and the upper extremity (35) of the valve closure member (20) when the valve closure member (20) is moved to the backseat position so as to create a temporary seal between the valve stem (14) and the bonnet (8). The non-rising stem valve assembly of claim 1, wherein the sealing means (36) is movable axially of the bonnet (8). The non-rising stem valve assembly of claim 1 or claim 2, wherein the sealing means (36) is positioned above the upper extremity of the valve closure member (20) between the valve stem (14) and the bonnet (8). The non-rising stem valve assembly of any one of claims 1-3, wherein the passageway (11) is widened adjacent the lower end of the bonnet (8) to receive the valve closure member (20) which engages the bonnet (8) within the passageway (11), the passageway (11) being narrowed to form a radially-extending flange spaced a distance above the valve closure member (20) to create a space between the valve stem (14) and the bonnet (8) below the radially-extending flange, the sealing means (36) being mounted in that space. The non-rising stem valve assembly of claim 4, wherein the upper extremity of the valve closure member (20) moves into the space where the valve closure member (20) is moved to the backseat position to engage and compress the sealing means (36) between the radially-extending flange, the bonnet passageway (11) and the valve stem (14) to create a temporary seal between the valve stem and the bonnet. The non-rising stem valve assembly of claim 4, wherein the valve stem (14) includes an outwardly-projecting stem shoulder which extends beneath the radially-extending flange in the bonnet (8), the sealing means (36) being mounted in the space beneath the stem shoulder, the upper extremity of the valve closure member (20) moving into that space as the valve closure member is moved to the backseat position to engage and compress the sealing means (36) between the stem shoulder, the bonnet passageways (11) and the valve stem (14) to create a temporary seal between the valve stem and the bonnet. The non-rising stem valve assembly of claim 6, wherein the stem shoulder is in engagement with the radially-extending flange. The non-rising stem valve assembly of claim 1, wherein the passageway (11) is widened adjacent the lower end of the bonnet (8) to receive the valve closure member (20) which engages the bonnet (8) within the passageway, the valve stem (14) including an outwardly-projecting shoulder formed a distance above the valve closure member (20) to create a space between the valve stem (14) and the bonnet (8) below the outwardly-projecting shoulder, the sealing means (36) being mounted in that space. The non-rising stem valve assembly of any of claims 1-8 which includes a packing nut (24) removably secured within the passageway (11) at the upper end of the bonnet (8), the packing nut having an exterior surface and a central channel defined by an interior surface, the central channel extending through the packing nut and the valve stem (14) extending through the central channel, the packing nut (24) including a first seal means (26) on the interior surface to create a seal between the valve stem (14) and the packing nut and a second seal means (28) on the exterior surface to create a seal between the bonnet (8) and the packing nut. The non-rising stem valve assembly of claim 9, wherein the packing nut (24) includes a first radial recess (30) on the interior surface for receiving the first seal means (26) and a second radial recess (32) on the exterior surface for receiving the second seal means. The non-rising stem valve assembly of claim 9, wherein the bonnet (8) includes an inwardly-extending radial flange (38) in the passageway (11) below the packing nut (24) and spaced a distance above the valve closure member (20) to create a space between the valve closure member and the bonnet (8) below the radially-extending flange, the means for securing the valve stem (14) within the bonnet (8) against movement in the axial direction of the valve stem (14) including lateral projecting means projecting outwardly from the valve stem (14) between the inwardly-extending radial flange and the packing nut. The non-rising stem valve assembly of claim 11, wherein the lateral projecting means include a retaining ring secured to the valve stem (14) and engaging the inwardly-extending radial flange (38). The non-rising stem valve assembly of claim 11, wherein the sealing means (36) is mounted in that space. The non-rising stem valve assembly of claim 13, wherein the upper extremity of the valve closure member (20) moves into the space when the valve closure member is moved to the backseat position to engage and compress the sealing means (36) between the radially-extending flange, the bonnet passageway (11) and the valve stem (14) to create a seal between the valve closure member (20), the bonnet (8), and the valve stem (14). The non-rising stem valve assembly of claim 13, wherein the valve stem (14) includes an outward-projecting stem shoulder which extends beneath the radially-extending flange in the bonnet (8), the sealing means (36) being mounted in the space beneath the stem shoulder, the upper extremity of the valve closure member (20) moving into the space as the valve closure member (20) is moved to the backseat position to engage and compress the sealing means (36) between the stem shoulder the bonnet passageway (11) and the valve closure member (20) to create a temporary seal between the valve closure member and the bonnet. The non-rising stem valve assembly of claim 15, wherein the stem shoulder is in engagement with the radially-extending flange. A method of replacing permanent seal means (26, 28) in a non-rising stem valve assembly (6) having a bonnet (8), a valve seat (29) adjacent a first end of the bonnet (8), a valve closure member (20, 22) operative to seat on the valve seat (29), to move from the valve seat (29) to a valve open position and to move from the valve open position to a backseat position, and a non-rising valve stem (14) extending into a second end of the bonnet (8) and connected to operate the valve closure member (20, 22), the permanent seal means (26, 28) serving to create a seal between the valve stem (14) and the bonnet (8) adjacent the second end of the bonnet (8), which method is characterised by : (a) creating a temporary fluid seal (36) between the bonnet (8) and the valve stem (14) positioned between the first end of the bonnet (8) and the permanent seal means (26, 28) when the valve closure member (20, 22) moves from the valve open position to the backseat position; (b) removing and replacing the permanent seal (26, 28) while the valve closure member (20, 22) is in the backseat position to create a new permanent seal; and (c) moving the valve closure member (20, 22) towards the valve open position to remove the temporary fluid seal (36).

Inventors: CRATER, TIMOTHY G., PETERSEN, JAMES A.
Applicants: ENGINEERED CONTROLS INTERNATIONAL INC.
Application year: 1989
Main classification: F16K41
IPC codes: F16K41, F16K1, F16K43