MXPA06007991A - Integrated post-guided seat ring assembly - Google Patents

Abstract

A control valve (20) having a seat ring assembly (30) constructed from a unitary piece of material is disclosed. The seat ring assembly may include a base (44) which serves as a valve seat for the valve plug (36) of the valve, and which includes a plurality of exterior threads (46) adapted to rotatably attach to a plurality of interior threads (47) provided within the valve body (22). The seat ring assembly may also include a post-guided bearing surface (52) to maintain alignment of the valve plug to the valve seat. The seat ring assembly can be secured to the valve body simply by threadably attaching the elements. Moreover, by providing the valve seat (67) and the guide surface as integral parts of the seat ring assembly, manufacturing costs and maintenance requirements are reduced and subsequent seal leak performance is increased.

Description

ASSEMBLY OF GUIDED SEAT RING WITH INTEGRATED POST FIELD OF THE INVENTION The invention relates in general to valves and more in particular, is related to control valves of sliding post with bolted seat rings.

BACKGROUND OF THE INVENTION Slipper control valves are commonly used to control fluid flow within process control circuits. As is known to those skilled in the art, a slide pole control valve modulates the flow of fluid through the valve body with the use of an actuator, coupled through a cap assembly, to move the element of control or valve plug in a reciprocal movement relative to a valve seat. The seat ring provides an annular surface inside the valve body against which the valve plug engages to close the valve when desired. There are two important features of a slide post control valve which are that it must control or modulate the fluid in a predetermined manner, which includes providing a seal when closed, and which must have the ability to withstand the influences of pressure and process temperature.

In addition, the slide control valves provide some form of guidance for aligning the valve plug and the valve seat. A type of guide known to those skilled in the art is provided by a bushing or a guide surface positioned within the cap assembly. A reduced diameter of the valve plug rests on the bushing mounted within a journal in the cap assembly. This type of guide is known as a pole guide. As is known to those skilled in the art, standard manufacturing tolerances and conventional assembly procedures can result in misalignment of the center line of the valve seat relative to the valve plug guide. This misalignment or displacement in the concentricity does not allow the valve plug to be properly seated within the valve seat, which provides a substantial leakage path between the valve plug and the seat during valve closure or shutdown. In certain applications, the concentricity problem will reduce shutdown performance and may create high velocity flows that erode the valve seat, in addition to degrading valve operation. Another type of typical guide, known to those skilled in the art as a pole guide, is where the valve plug is guided by the valve chamfer (i.e., the internal components of the valve exposed to the process). In general, the seat ring retainer provides a internal guide surface within the fluid flow path where the valve plug moves through its entire travel. In such a valve construction, a separate seat ring retainer and the seat ring are typically fixed in place between the valve body and the cap. A package, such as a spiral wound package, is usually provided between the cap and the seat ring retainer in fixed chamfer designs. As is known to those skilled in the art, the fixed chamfer provides a pre-loading force, designed to compress the spiral wound package. Under compression, the spiral wound package provides an opposite spring force that creates a seal between the seat ring retainer and the cap and the seat ring and body. These designs are susceptible to seal failures as described in more detail below. Those skilled in the art will recognize three specific problems associated with conventional seals or seals. First, slip-post control valves are often used in process applications that reach temperatures above 282 ° C and pressure drops exceeding 150 psi. These extreme operating conditions create leakage problems of the valve assembly due to differences in the thermal expansion of the construction materials. With the use of different construction materials, valve manufacturers increase the operation and / or decrease the cost of assembling the valve. valve. For example, general process applications may employ a control valve that has a steel body and a stainless steel seat ring retainer. As is known, the body of the steel valve has thermal expansion characteristics different from those of the stainless steel seat ring retainer. In this way, an increase in the operating temperature can increase, consequently, the pre-loading force, so that the spiral wound package over-stretches or produces a permanent deformation. When temperatures return to ambient conditions, the packing can not return to its pre-stressed condition and a leakage path is created. Alternatively, when the valve body is constructed of a material that expands more than the material of the seat ring retainer, an increase in the operating temperature may cause a corresponding decrease in the pre-load force in the wrapped package. spiral which causes leakage between the seat ring and the valve body. Second, conventional slide pole valves that use spiral wound packages are subject to pressure limitations. The compatible nature of spiral wound packaging creates a robust seal for numerous applications, but as will be recognized by those skilled in the art, these packages are limited in pressure drop, or in differential pressure that can be adapted without losing integrity of the seal. For example, when the packaging Spiral wound on an unbalanced control valve can maintain a suitable edge clamping force up to a pressure limit of 300 psi, any differential pressure that exceeds this pressure limit will temporarily deform the packing and can create a leakage path. Third, the leaks are fixed in the conventional fixed design sliding valve control assemblies, by applying a large load at the bonnet joint. As is known to those skilled in the art, increasing the load of the bonnet joint increases the cost of the control valve, since it requires heavier structures within the valve body and the cap to support the increased load, as well as it requires greater union of the cap to apply the loads. Therefore, it should be noted that there is a need for an improved seat ring assembly for a sliding pole control valve that is manufactured from a few parts and that can be assembled and maintained in position with less equipment and structures than what is required. which is required at present.

BRIEF DESCRIPTION OF THE INVENTION In accordance with one aspect of the invention, a control valve is described which may comprise a valve body, a valve plug, a valve post and a guided seat ring assembly with integrated post. The valve body can Include an entrance, an exit and a camera between the entrance and the exit. The valve plug is slidably disposed in the seat ring assembly with the valve post connected to the valve plug. The seat ring assembly is arranged in the chamber. The seat ring assembly is screwed into the valve body. In accordance with another aspect of the invention, there is disclosed a method for assembling a control valve which may comprise inserting a seat ring assembly with integrated post guide into the body of the control valve, coupling the mounting of the control valve in a threaded manner. Seat ring with the body of the control valve and ensure the cap assembly with the body of the control valve. These and other aspects and features of the invention will become apparent upon reading the following detailed description together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of an unbalanced slide post control valve constructed in accordance with the teachings of the invention. While the invention is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described in detail. However, it must be understood that there is no intention to limit the invention to the specific form set forth, on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents that fall within the spirit and scope of the invention as defined in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, a slide post control valve constructed in accordance with the teachings of the invention, generally refers to the reference number 20. It should be understood that the term "sliding post control valve" is intended to encompass any control valve, wherein a valve plug mounted on a reciprocating post moves linearly or reciprocally relative to the valve seat mounted within the valve body, between an entrance and an exit of the body. In addition, persons skilled in the art will recognize that a sliding pole control valve can encompass a variety of control valves, such as globe valves or angle type valves. The example described is described in the context of an unbalanced control valve. It should be understood that unbalanced globe valves are those in which the slide control element, i.e., the valve plug, does not allow fluid communication through the control element. As a result, there may be a significant pressure differential in the opposite sides of the control element, which requires relatively high activation forces. An unbalanced control valve 20, guided with a post, is shown to include a valve body 22 defining an inlet 24 and an outlet 26. A chamber 28 is provided between the inlet 24 and the outlet 26 and houses an assembly 30 of seat ring. A cap assembly 32 is secured with the valve body 22 near the chamber 28 and provides an opening 33 for receiving a valve post 34 connecting the valve plug 36 with an actuator (not shown). The package (not shown) is provided within the cap 32 and around the valve post 34 to provide an adequate seal therebetween. The cap assembly 32 is secured with the valve body 22 by a plurality of fasteners (not shown). The seat ring assembly 30 is shown to be essentially cylindrical and to be made of a unitary piece of material, which can be provided in the form of molded steel, stainless steel or the like. Alternatively, the seat ring assembly 30 is not limited to a cylindrical shape only, provided that the seat ring assembly 30 can be physically accommodated by the internal volume of the control valve 20. A base 44 of the seat ring assembly 30 includes a plurality of threads 47 used to threadably engage the seat ring assembly 30 with the valve body 22. More specifically, the valve body 22 includes a plurality of threads 47 in a passage 53 at the base of the chamber 28. Accordingly, the seat ring assembly 30 is physically coupled with the valve body 22 by threadedly engaging the seat ring assembly 30 with the valve body 22 through the rotation of it. An inner diameter of the guide portion 45 of the seat ring assembly 30 extending over the base 44 is substantially greater than the outer diameter of the valve plug 36. Accordingly, the valve plug 36 engages with the guide portion 45 on an upper edge 48. This can be achieved by providing the upper edge 48 with a reduced diameter section with the use of a base metal as a bushing, or more efficiently, by providing a separate element such as a bushing 50, as shown, to provide a coupling and direct alignment of the valve plug 36. In the present embodiment, bushing 50 can be frictionally held within upper edge 48 or coupled with a variety of methods known to those skilled in the art. The bushing 50 provides a lower surface 52 such as a bushing or a guide surface which facilitates sliding. The surface 52 between the bushing 50 is nominally 0.025 cm larger in diameter than the valve plug 36 to facilitate assembly, restricted enough to provide guidance during the operation. The base 44 of the mounting 30 of the seat ring provides a valve seat 62 for coupling with a 64 beveled circumferential surface of the valve plug 36. Furthermore, it should be noted that the valve plug 36 includes a nose section 66 having a predetermined shape adapted to provide the desired flow characteristics of the control valve 20. Movement of the actuator (not shown) causes movement of the valve post 34, which in turn, causes movement of the valve plug 36 relative to the valve seat 62. The relative movement of the valve plug 36 with respect to the valve 62 provides an opening or closing of the control valve 20. Within the seat ring assembly 30, near the valve seat 62, one or more openings 70 can be provided. In Figure 1, two openings 70 are shown. As will be understood by persons skilled in the art, the opening 70 it can have a variety of shapes as long as it does not impede flow through the control valve 20. For example, as shown in Figure 1, the opening 70 may be provided in the form of a rectangular opening extending between the base 44 and the upper edge 48. As shown in FIG. Alternatively, a number of holes (not shown) can be provided in the seat ring assembly 30. As described above, unbalanced, conventional control valves with clamped fasteners (ie, valve components other than the valve body and cap) utilize the strength of the body-to-shell connection for provide a load to the spiral wound packaging to in turn fix the membrane parts together. The spiral wound package acts like a spring. Because spiral wound packaging is used as a spring, the different pressure and temperature capacities of the valve are limited. The temperature limits are due to the thermal expansion differential between the valve body and the chamfer parts. In other words, the chambered parts can expand more or less than the valve body, which can over-compress or limit the compression of the spiral wound package when the temperature limits are exceeded. The limits of the pressure differential are typically due to the pressure acting on the chamfer parts, which can limit the compression of the spiral wound package and cause leakage. Other unbalanced control valves known in the art have a separate guide bushing in the cap and an individual seat ring assembly to eliminate the above-described spiral wrapped / clamped packing problems. However, such valves are susceptible to concentricity problems. In other words, the alignment of the seating surfaces in the valve plug and the seat ring is affected by many machining concentricity tolerances in the body, the seat ring, the cap, the guide bushing and the valve plug. . The loss of concentricity between the valve components does not allow the valve plug to be Fit completely with the valve seat. This, in turn, can essentially reduce the performance of the control valve to shut off or when the control valve closes or causes erosion of the valve seat due to the high velocity flows created with incomplete shutdown. In the control valve 20 described, the seat ring assembly 30, which includes the valve seat 62, the bushing 50 and the base 44, is a single component and can be constructed of the same material as S31600SST. Accordingly, the control valve 20 described is less prone to the problems associated with temperature and pressure fluctuations.

Alternatively, the bushing 50 can be constructed of a material with higher wear resistance, such as an alloy of CoCr-A or S17400ST to decrease maintenance and wear of bushing 50 during operation. further, it can be seen that the seat ring assembly 30 not only provides the alignment of the valve plug, but also provides a seal between the inlet 24 and the outlet 26 without the use of a flat sheet packing or a spiral wound package , or other sealing mechanism. By threadedly coupling the seat ring assembly 30 with the valve body 22 and engaging the valve plug 36 against the valve seat r62 under sufficient pressure, an adequate seal is created between the inlet 24 and the outlet 26 without the use of packaging or other form of seal. In addition, by screwing the seat ring assembly 30 in a threaded manner with the valve body 22, and by avoiding the use of gaskets or seals, the cap 32 it can be manufactured with a less robust structure and can be coupled with the valve body 22 under less stress and still provide the proper operation and sealing of the valve 20. As described above, this is opposite to prior art valves They use gaskets, which only operate well when they are sufficiently compressed by the cap assembly. In accordance with the prior art valves, the cap assembly and the fasteners or bolts used to connect the cap assembly to the cushion, needed to have the measures to withstand the force necessary to provide adequate compression of the seal elements during the operation of the valve. The prior art designs do not solve the thermal expansion problems described and / or the operating pressure limitations. In accordance with this, the capacity of operation and seal of the valves of the prior art was affected. The guided seat ring assembly with integrated post is not affected by variations in thermal conditions and has no pressure limitations of conventional spiral wound packaging designs. With the use of the teachings of the present invention, such additional elements are removed, which makes the valve more applicable to such wide temperature ranges. During the operation, it can be seen that a valve constructed in accordance with the teachings of the invention can be easily constructed by fitting in a threaded manner an assembly of seat ring with a plurality of internal threads provided within the valve body. The manufacture and maintenance of such valves is greatly improved, since the number of parts is very small and the forces necessary to secure the cap with the valve body is greatly reduced as well. From the foregoing, it will be appreciated by those skilled in the art that the teachings of the invention can be used to construct an unbalanced pole-guided valve having a seat ring assembly that can be threadedly engaged with the body of the valve. By doing this, the sealing capacity is reached and also, the production costs, as well as the maintenance requirements are reduced.

Claims (15)

1. A control valve characterized in that it comprises: a valve body having an inlet, an outlet and a chamber between the inlet and the outlet; and a valve plug disposed in a sliding manner within the valve body; a valve post connected to the valve plug; and a seat ring assembly disposed within the chamber, the seat ring assembly has a first end and a second end and is threadedly fastened to the valve body, the seat ring assembly also includes an orifice to receive a valve plug at the first end and a bushing disposed within the first end; wherein the valve plug slidably engages the bushing and remains essentially concentric with the valve seat disposed within the second end.

2. The control valve according to claim 1, characterized in that the control valve is not balanced.

3. The control valve in accordance with the claim 1, characterized in that the seat ring assembly is held with the valve body without any packing between them.

The control valve according to claim 1, characterized in that the seat ring assembly includes at least one opening through a cylindrical wall of the valve. same.

The control valve according to claim 1, characterized in that the seat ring assembly includes a plurality of openings through a cylindrical wall thereof in a predetermined pattern.

The control valve according to claim 5, characterized in that the plurality of openings is provided with predetermined shapes.

The control valve according to claim 5, characterized in that the plurality of openings is provided as a plurality of bored holes.

The control valve according to claim 1, characterized in that the valve plug includes an essentially cylindrical base from which a nose extends, the nose having the shape to provide the desired flow characteristics.

9. A seat ring assembly for a valve, characterized in that it comprises: a housing having a hole, the housing having at least one opening therein, the housing having a first end and a second end; a valve seat formed on an interior surface of the second end; a plurality of threads formed on an outer surface of the second end, the seat ring assembly is formed integrated as a piece, wherein the diameter of the first end is smaller than the diameter of the second end, which forms a guide surface within the seat ring assembly.

The seat ring assembly and the seat ring assembly according to claim 9, characterized in that the diameter of the first end is reduced by placing a bushing inside the first end.

11. The seat ring assembly and the seat ring assembly according to claim 9, characterized in that the seat ring assembly includes a plurality of openings.

12. A method for assembling a control valve, characterized in that it comprises: inserting a guided seat ring assembly with integrated post into the body of the control valve; coupling threaded seat ring assembly with integrated post to the body of the control valve; and securing a cap assembly with the control valve body.

The method according to claim 12, characterized in that the control valve is an unbalanced globe valve.

The method according to claim 12, characterized in that the control valve is guided with a pole.

15. The method according to claim 12, characterized in that the cap assembly is secured with the Body of the control valve with the use of thread fasteners.