MXPA05012964A - Seal for a valve - Google Patents

Abstract

The invention relates to a seal to be used as a valve stem seal in a valve for controlling flows containing solid material such as slurry flows with an actuator. The seal (4) is positioned outside of the valve body (10) so that the inside of the seal (4) and the valve body (10) form an essentially closed space for the flow to be controlled.

Description

SEAL FOR A VALVE Field of the Invention The invention relates to a seal that is to be used as a seal of a valve stem.

BACKGROUND OF THE INVENTION There are several methods to achieve a seal between the stem of a valve and the valve body, while still allowing the linear movement of the valve stem. It is common practice to use a control valve to control the flow of slurry. The flow is controlled in all the control valves by varying the orifice through which the slurry flows. One of the most common methods is to adjust the position of the valve plug relative to the valve seat in order to modify the size of the hole and thus the flow through the control valve. The force required to displace the valve plug is provided by an actuator, which is connected to the valve plunger by means of an actuator rod and the valve stem. The seal between the valve stem and the valve body is most commonly achieved by some type of sliding seal arrangement. Even though this arrangement is suitable for most liquids and gases, it usually fails with the grout. If the slurry penetrates the sliding seal, the solids within the slurry will result in abrasion of the seal which eventually results in seal failure and leakage of the process liquid or slurry out of the valve. Different types of arrangements for the seal between the valve stem and the valve body are described, for example, in United States of America patent number 6,182,684, where a bellows is used to balance the sliding portion of the seal. . A rotary valve sealed with bellows is also disclosed in U.S. Patent No. 5,090,658.

Objectives of the Invention The object of the invention is to eliminate some of the disadvantages of the prior art, as well as to achieve an improved seal between the valve stem and the valve body in order to avoid the sliding arrangement. The essential features of the invention are cited in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS: The invention is described in more detail and with reference to the accompanying drawings in which: Figure 1 illustrates a preferred embodiment of the invention as a side view of a partial cut, when the valve is in the position open, and Figure 2 illustrates the embodiment of Figure 1 as a side view of a partial cut, when the valve is in the closed position.

Detailed description of the invention. The seal of the invention is advantageously suitable for a valve arrangement, which is used to control flows containing solid material such as slurry flows. For purposes of this description, the slurry can be defined as an inhomogeneous liquid with a percentage of suspended solids. The valve contains a valve body and a valve seat is placed inside the body of this valve. The valve seat forms a hole between two containers within the valve body so that the flow of slurry that is fed into the valve body through an inlet penetrates into the first container in the direction of movement of the valve. grout. The flow of slurry from the valve body is discharged from the second container through an outlet. In order to control the amount of grout flow that is discharged from the valve body, the hole between the containers is provided with a valve plug. The valve plug is configured in such a way that when it is mounted in the hole it is possible to stop the flow of slurry from the first container into the second container. To control the flow of slurry between the containers the valve plug is connected to an actuator, which is preferably installed outside the body of the valve. valve. The valve body is provided with an opening for a valve stem, which is installed between means, which are additionally connected to the actuator, and the valve plug. The opening for the valve stem is dimensioned so that the valve stem can move freely in the opening without having any contact with the valve body. The stem of the valve thus emerges from the valve body through the opening. The valve stem is at the other end opposite the end having the valve plug attached to the means having contact with the actuator and the valve stem is moved within the movement defined by the actuator. In accordance with the present invention the valve stem is sealed so that the grout is maintained within the seal arrangement. In accordance with the invention, the seal of the valve stem is attached to the valve body at one end and at the other end to the means that have contact with the actuator. When attached to the valve body the seal is fixed around the opening whereby the valve stem is positioned so that a gap is created between the seal and the valve stem. The seal is attached to the means that contact the actuator so that the clearance between the seal and the valve stem is essentially created in a similar manner for the entire distance between the points of attachment in the body of the valve. the valve and on the means that have contact with the actuator. In addition, the seal of the invention is located outside the body of the valve. The seal of the valve stem is preferably, but not limited to, being located in the upper part of the valve body. Depending on the work circumstances the design may require that the valve stem seal be located on any other side of the valve body. In the preferred embodiment of the invention, the valve plug is installed so that when the orifice between the two containers of the valve body is fully closed the valve plug is in its lowest position relative to the body of the valve. valve and when the orifice between the two containers is fully open the valve plug is in its highest position relative to the valve body. When the valve stem is displaced between the open position and the closed position of the valve plug within the movement Defined by the actuator, the seal that surrounds the stem of the valve is displaced accordingly. When the valve is operated to control slurry flows and when the valve plug is at least partially in the open position the slurry will flow from the first container to the second container. During this flow the space formed between the seal and the valve stem may be at least partially filled with grout because the valve stem has no contact with the valve body. Because the stem of the valve is connected to the means having contact with the actuator, the actuator itself is isolated from the environment of the slurry in order to protect the actuator. The valve stem seal of the invention provides a reliable seal in the process fluid to prevent leakage of a valve, while still allowing the valve stem to move freely to work. The seal according to the invention is made flexible so that the seal is installed movably with the valve stem. The additional required properties for the seal of the invention, include, but are not limited to, the following: Flexibility to allow the required movement of the valve plug between the closed position and the open position. - Resistance to corrosion to prevent corrosion of chemical products that are inside the grout as well as the external environment. - Resistance to operating pressure; This property is required so that the seal of the valve is able to withstand the pressure of the grout. - Resistance to abrasion: this property is required so that the seal and the stem of the valve are capable of resisting the abrasion due to the flow of the grout. The materials that are considered for manufacturing the flexible seal of the valve for grout of the invention include, but are not limited to, the following: - Rubber, natural and synthetic. - Plastics, such as polyurethane and high density polyethylene (HDPE). - Composite materials, such as rubber / polyurethane or polyurethane reinforced with fiber or reinforced rubber compounds and compounds of different types of rubber. - Metal, such as steel.

Any combination to the aforementioned materials is also possible.

The flexible seal of the valve rod for slurry, according to the invention, can be used with various control valves. The flexible valve stem seal for grout is primarily designed for grout control valve applications, but the flexible valve stem seal for grout is not limited solely to control valve or grout applications. According to Figures 1 and 2, a valve body 10 is provided with an inlet 11 for the supply of slurry within the valve body 10 and an outlet 12 for discharging slurry from the valve 10. The valve body 10 is also provided with a division 8, which separates the interior of the valve body 10 into two containers; a grout feed container 13 and a grout discharge vessel 14. The partition 8 is further provided with a hole 15 through which slurry will flow from the container 13 to the container 14. In order to control the flow of the slurry the orifice 15 is provided with a valve seat 7 where a plug 6 valve is plugged when the flow from the container 13 to the container 14 is stopped as illustrated in Figure 2. In order to control the movement of the valve plug 6 between the open position in Figure 1 and the closed position in Figure 2 in the direction referenced 9, the valve body 10 is provided with an actuator 1 which has a connection with the valve plug 6. The actuator 1 is provided with an actuator rod 2, which is connected hydraulically, pneumatically or electrically with an actuator connection flange 3. The actuator connection flange 3 is connected to a bellows 4 which functions as the seal of the valve rod by means of a terminal plate 16. The bellows 4 is at another end opposite the actuator connection flange 3 attached to the body 10 of the actuator. valve by a terminal plate 17 provided with an opening 18. The valve body 10 has an opening 19 substantially similar in shape to the opening 18 of the end plate 17. A valve rod 5 is attached between the end plate 16 of the seal 4 of the valve stem and the valve plug 6 so that the valve rod 5 is partially in and partially out of the valve body 10. The valve rod 5 projects beyond the seal 4 of the valve stem within the valve body 10 through the openings 18 and 19 on the plate. terminal 17 of the seal 4 of the valve stem and in the valve body 10, respectively. According to the invention, the openings 18 and 19 are designed so that there is sufficient clearance between the valve stem 5 and the interior of the bellows 4 to allow free movement of the grout advancing through the openings 18 and 19. Therefore, the interior of the seal 4 and the valve body 10 form an essentially closed space for the flow to be controlled. The clearance between the valve stem 5 and the interior of the bellows 4 is critical for seal operation. The clear is designed to be large enough to avoid excessive abrasion of the interior of the bellows 4. Nowhere inside the flexible seal 4 of the valve stem for grout comes into contact with the valve stem 5. In order to achieve the control of slurry flow, the actuator 1 will displace the actuator connection flange 3 and additionally the valve rod 5 which is connected in order to displace the valve plug 6, essentially with a linear movement. The actuator connection flange 3 with the end plate 16 of the valve stem seal 4 are free to move with the valve rod 5 and the seal 4 as long as the end plate 17 of the seal 4 is fixed in position with the body 10 valve and has no freedom of movement. The result of the movement of the valve stem 5 is that the bellows 4 working as the seal will be compressed or extended. The purpose of the bellows 4 is to maintain a seal between the valve body 10 and the openings 18 and 19. The bellows seal 4 prevents the grout from escaping from the valve arrangement as the valve rod 5 moves. Although the invention has been described with respect to certain specific modalities, it will be understood that many modifications and changes can be made by those skilled in the art without departing from the spirit of the invention. It is, therefore, intended that the appended claims cover all such modifications and changes insofar as they fall within the real spirit and scope of the invention.

Claims (11)

1. Claims 1. A seal to be used as a valve stem seal on a valve for controlling flows containing solid material such as slurry flows with an actuator, characterized in that the seal (4) is positioned outside the body (10) of valve so that the interior of the seal (4) and the valve body (10) form an essentially closed space for the flow to be controlled. A seal according to claim 1, characterized in that the seal (4) is placed around a valve rod (5) connecting the valve plug (6) and the actuator (1). 3. A seal according to claim 1 or 2, characterized in that the seal (4) is installed in a mobile manner with the movement of the valve stem (5). 4. A seal according to claim 1, 2 or 3, characterized in that a mechanical contact between the seal (4) and the valve stem (5) is avoided. 5. A seal according to any of the preceding claims, characterized in that a mechanical contact between the valve rod (5) and the valve body (10) is avoided. 6. A seal according to any of the preceding claims, characterized in that the seal (4) is manufactured to be flexible. 7. A seal according to any of the preceding claims, characterized in that the seal (4) is in the form of a bellows. 8. A seal according to any of the preceding claims, characterized in that the seal (4) is made of rubber. 9. A seal according to any of claims 1-7, characterized in that the seal (4) is made of plastic. • A seal according to any of claims 1-7, characterized in that the seal (4) is made of steel. 11. A seal according to any of claims 1-7, characterized in that the seal (4) is made of a composite material.