Seal Cartridge Control Valve

TECHNICAL FIELD

This invention is directed generally to sealing systems for valves anά more specifically Io a pressure balanced seal ring and a seal cartridge unit for a control valve,

BACKGROUND

A typical control valve has a linear motion closure member eom.rnor.ily referred io as a plug (or piston), one or more ports, and a body typically distinguished by a globular shaped cavity around the port, region. The body is the part of the valve x-vhich is the main pressure boundary. The body typically provides the pipe connecting ends and the fluid flow passageway, ϊn a control valve, the closure member is a movable part of the valve that is positioned m the flow path to modify die rate of flow through the valve.

The plug closure member is a part, often cylindrical in nature, which moves in the flow stream with linear motion to modify the flow rate. It may or may not have a contoured portion, to provide How characterization. It may also be a cylindrical or eonically tapered part, in other types of valves, the closure .member includes ball, disk and gate,

A flow orifice in the flow passageway (path) Interacts with the closure member to close the valve. The orirke may be provided with a seating .surface, to be contacted by or closely fitted io the closure member, to provide tight shuv-otf or limited leakage, i.e., to close the valve.

A cage, guide or liner is typically a part in a control valve thai generally surrounds the closure member to provide alignment and facilitate assembly of other pans of the valve trim. The cage may also provide How characterization and/or a seating surface. Control valve trim typically includes the interna! parts of a valve which WG in flowing contact with the controlled fluid. Examples of valve trim are the plug, seal ring and cage. The body is not considered part of the trim.

FIG I illustrates a standard prior art control valve KO manufactured and sold by Dresser, incλ Masondian® division. A valve stem 1 extends through a valve bon.net 7 to a valve plug 15. Valve plug i 5 is received in & cage 16. A seal 30 is disposed between the plug 15 and the inner wall of cage 16. FIGS, 2A and 28 illustrate different embodiments of the seal 30 between the plug (piston) 15 and the inner wall of cage 16. FIG. 2B shows a two-part seal with an inner member 31 that can be formed of Ni-R exist metal tmύ an outer member 32 that can be ibrraed of structural graphite, in this valve, the seai is located in a seal groove (gland) on the plug. In other variations, the seal may be located in a sea! groove on the cage wall.

TABU: I

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Table 1 includes information on the manufacturer's suggestions regarding selection of the particular type of seal depending on. the temperature range of the fluid fluwiϊig through the valve. In high temperature service, the prior art valves use rigid graphite seals. These rigid seals include a split or break in the circumference that allows the seal to conform to the diameter of the scaling surface. Such a split ring seai is similar to a piston ring used to seal an internal combustion engine piston m the

engine cylinder. Because the circumference of the seal ring is split, fluid leaks across the seal.

Other prior art high temperature seals may be formed of compressed flexible graphite. This flexible graphite prior art sea! results in a high sliding friction, and a high rate of wear makes it unsuitable for automated posϊtioning/lhrottlmg applications of control valves,

SUMMARY

In one aspect, a seal cartridge including a flexible seal ring provides high pressure sealing capabilities in high temperature environments using a pressure balanced seal The seal accommodates the manufacturing tolerances between the plug, the cage and ihe ring groove. hi one aspect, a seal cartridge includes a flexible seal ring disposed in a seal groove. The flexible seal ring includes a first front sealing face adapted for sealing contact with the outer surface of the plug, a rear face, at least one downwardly disposed upper race, said face being disposed between the front face and the rear face, at least one downwardly disposed lower face, and a second front sealing lace disposed upwardly between the downwardly disposed lower face and the first front sealing face. Some seal cartridges also include an upper retaining ring disposed adjacent to the flexible seal ring. The upper retaining ring can include at least one downwardly disposed lower face disposed proximal to the downwardly disposed upper lace of the flexible seal ring. The at least one upper face of the flexible seal ring can be adapted to flex away from the at least one downwardly disposed upper face of the upper retaining ring, and the lower face of the flexible seal ring can be adapted to flex downward, In one aspect, a flexible seal ring engages an outer surface of the plug to form a ^■ high temperature and high pressure sea! between the outer surface of the plug and a cage wall of ihe control valve. The flexible seal ring may be disposed in a seal groove (e.g., a seal groove in Ihe cage wall or a seal groove in the outer surface of the plug). The flexible seal ring has a first front sealing face adapted for sealing contact that is oriented towards an aperture of the sea! groove, a rear face, at least one downwardly

disposed upper face, said face being disposed between the front lace and the rear face The seal ring may include an upper face disposed between iron! face and face. Hie seal ring further includes at least (me downwardly disposed lower lace, and a second front seaHng lace disposed upwardly between the downwardly disposed lower face imά the first front sealing lace. The at least one upper face of the flexible sea! ring can be adapted to ilex downward, the lower face of the flexible seal ring can be adapted to flex downward, and Oie second front sealing face of the flexible sea! ring can be adapted to flex toward the aperture of the seal groove. The seal cartridge may include only flexible seal ring or may alternatively contain additional elements. in one aspect, a flexible seal ring for sealing ars outer surface of a plug io a cage wall in a control valve includes a first sealing face adapted for sealing contact with the outer surface of the plug, a rear face disposed opposite the first sealing face with the rear face axiaϊly offset relative to the first sealing face; and an upper face disposed between the first face and the rear face. The upper face extends from the reai lace towards the from face such that an interior angle between the upper face unά the rear iacc is greater than, 1 K) degrees.

The design of the seal maintains the flexible seal ring in compression. Materials used in the manufacture of the flexible seal ring for high temperature applications are typically brittle but have high compression strengths with lower tensile strengths. Therefore, the flexible seal ting design of the present invention maintains the flexible seal ring in compression through the torsional twisting (e.g., torsional rotation of the seal ring about a circumferential axis of the sea! ring) of the seal ring when it is pressure energized.

When assembled, the seal cartridge can be disposed into a ring groove of a cage wall and held in place by a locking ring. It will be understood that, in other embodiments, the sea! cartridge of the present invention may be disposed in a seal groove on the plug instead of in a seal groove on the cage wall. In. some embodiments, an inner surface of the seaHng ring comprises the front sealing face. The front seaHng face can be oriented towards the outer surface of the plug. In some embodiments, an outer surface of the sealing ring comprises the front seaHng face. The fπsnt sealing face can be oriented towards the inner wall of the cage.

In SiiϊTse embodiments, the cartridge seal is configured to be disposed in a seal groove in the wall of the cage and the second front sealing face of the flexible seal ring is adapted to flex toward the plug. In some cases, the cartridge seal also includes a spiit ring seal element disposed in a recess in a portion of the first, lower retaining ring that is disposed toward the plug, In some embodiments, She cartridge seal is configured to be disposed in a seal groove in the outer surface of the plug and the second front sealing face of the flexible seal ring is adapted to Oεx toward the wall of the cage. In some eases, the cartridge seal also includes a split ring seal element disposed in a recess in a. portion of the first lower retaining ring that is disposed toward the wall of the cage,

In some embodiments, sea! rings also include a lower surface including a second sealing face and a lower face, the second sealing face extending from the first sealing face to the lower face such that an interior angle between the first and second sealing faces JS greater than 140 degrees and the lower face extending from the second sealing face to the rear face.

The cartridge seal may further include an upper retaining ring disposed adjacent to the flexible seal dug. The upper retaining ring can include braided long strand carbon fibers.

^' flic cartridge seal may further include a first lower retaining ring disposed adjacent to the flexible sea! ring. The lower retaining ring cars include: at least one upper lace disposed proximal to the downwardly disposed lower face of the flexible seal ring, wherein said lower face of the flexible seal ring being adapted to flex toward the at ieast one upper face of the lower retaining ring. The lower retaining ring can include a upper lip that contacts the at least one upwardly disposed front face of the sealing ring.

The cartridge seal may, but is not required, to include a split ring seal element disposed m a recess in a portion of the first lower retaining ring.

In some embodiments, the flexible seal ring comprises a unitary ring. The flexible seal ring can include (e.g., he made of) pojyethεrefherkeione (PBEK), graphite, Ni -resist metal, and/or hard- faced metal (e.g. _* 347ss, 316ss, etc).

The details of one or more embodiments of the invention are set forth m the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRI PTlON OF DRAWINGS

PIG. \ is a cross-sectional view of a prior art control valve.

FIGS. 2. A arid 2B are enlarged partial cross-sections] views of seals used in Ae valve of FIG I .

FIG 3 is a cross-sectional view of a control valve with the seal cartridge of the present invention.

FIG. 4 is an enlarged partial cross-sectional view of the sea! cartridge, plug, and cage of the valve of FlG 3.

FIG 5 Is a further enlarged partial cross-sectional view of the seal cartridge, plug, and cage of the valve of. FlG 3. FIG f) is a partial perspective ol ^' tihe seal cartridge, plug and cage of the valve of Fig. ?.

F(GS. 7A and 7 B are, respectively, a perspective and a partial side view of the seal ring of the seal cartridge of FIGS. 5 and 6.

FlG. 8 is an enlarged partial cross-sectional view of the seal cartridge, ping, and cage of another embodiment of a valve.

Like reference symbols in the various drawings indicate like elements.

I) ETAILEB DESCRIPTION

Referring to FIG. 3, a control valve 100 includes inlet port i 10 and outlet port 120, Plug i 15 is movahly disposed in cage 1 16. As used herein, the term "cage" is intended to encompass a cage, liner, guide, and the structural and functional equivalents thereof. As used herein, the term "plug" is intended to encompass a plug or piston and the structural and functional equivalents. As used herein, the term "seal groove" is intended to encompass a groove, recess, gland, and the struciirral and

functional equivalents. As used herein, the term "fluid" includes gas, water, oil, particulate matter, and any combination thereof.

Referring to FIG, 4, pressure balanced seal cartridge 1 30 is disposed between plug, 1 1 5 and cage 1 16. Fluid travels through opening 1 1 1 in plug ! ! 5 and splits into o openings 1 12 and exits the plug. This can somewhat balance the pressure present on opposite sides of plug i 15 and, thus, can reduce the size of actuator required to operate the valve. It will be understood that the direction of Sow may be reversed in the valve 100, but if the flow is reversed the seal cartridge as described herein must be installed upside down in order for the fluid pressure to energize the seal properly. The 0 mechanisms by which the seal is energized to engage plug 1 15 and the wall of cage 1 16 are discussed in more detail below.

Referring to FIGS. 5, 6, ^" A ₅ and 7B, the cartridge seal 130 engages an outer surface of the ping 115 io form a high temperature and high pressure seal between the outer surface of the plug 1 15 and the wall of the cage 1 16 in the control valve 100 S (see FIG. 3). The cartridge seal 130 includes a flexible seal ring 131 disposed in a sea! groove 1.38 in the eage wall 1 16. The flexible seal ring 13 1 has a first front sealing Face 150 (e.g., on an inner side of the ring) adapted for sealing contact with the outer surface of the plug 1 i 5, a rear lace 156 (e.g., on an outer side of the ring), and at least one downwardly disposed first upper face 154, said face 154 being 0 disposed between the front lace 150 and the rear face i 56. The sea! ring may also include a second upper face 152 disposed between front face 1 50 and first upper face 154. The seal ring 131 further includes at least one downwardly disposed lower face 158, and a second front sealing i ^' aee 160 disposed upwardly between the downwardly disposed lower face 158 and the first front sealing face 150. 5 Referring to FiGS. 7 A and IB, seal ring can be a miliary ring formed as an annuius in plane P aboin a central seal axis As, First front sealing lace 150 is axial Iy offset from rear face 156 (e.g., front sealing face 150 is above plane P ami rear face ! 56 ss partially below plane P).

As used herein, ^iι ιιp" as used in reference io the seal ring indicates a direction 0 itom which energizing pressure is applied to the seal ring and ''down" indicates an

opposite direction. Thus, as valves can be oriented at various angles, up and down indicate relative rather than absolute directions.

Referring again to FIGS. 5 and 6, the cartridge seal 130 may, but is not required to, iurthcr Include ars upper .retaining ring ! 33 disposed adjacent to the flexible seal ring 131 , The upper retaining ring includes at least, one downwardly disposed lower face 162 disposed proximal to the downwardly disposed upper face 154 of the flexible seal ring 131 . The upper retaining ring 133 may include a front- face 164 and a rear face 166 and a lower face portion 168.

The cartridge sea! 130 may, but is not required to, further include a first lower retaining ring 135 disposed adjacent to the flexible seal ring 13 1 . The lower retaining ring 135 includes at leas! one upper face 170 disposed proximal Io the downwardly disposed lower face 158 of the flexible seal ring 131 . The retaining ring 135 further includes a face 172 disposed toward the plug 1 15. The cartridge seal 130 may. but is not required, to include a second lower retaining ring 137 (e.g.. a split ring seal deraenO disposed in a recess 140 in a portion of the first lower retaining ring 135. The retaining ring 135 may include faces 1 74 and 176 disposed toward the second Sower retaining ring 137.

When assembled, the seal cartridge 130 is disposed into ring groove OS of cage wall 1 16 and held in place by a locking ring 130, It will be understood that, in other embodiments, the seal cartridge 130 of the present invention may be disposed in a seal groove on the plug instead of in a sea! groove on the cage wall, it will be understood that the present cartridge seal unit 130 may be used in any type of control valve with a linear moving plug. The cartridge seal's use is noi limited to the valve embodiment illustrated in ibis specification. When in operation, the pressure of the fluid flowing through the valve results in torsional rotation R of flexible seal ring 131 about a circumferential axis Ae. The point of engagement between the sea! ring 131 and the plug 1 15 (e.g., front face 150) and the point of engagement between the seal ring 131 and the cage 1 16 (e.g., rear face 15(5) are not horizontal relative to the frame of reference in which up arid down are as described above.

In the illustrated embodiment, contact of sea! ring 131 with plug 1 15 and cage 1 16 as shown can provide an initial sea! that can be effective for low pressures. As pressures are increased, the energizing pressure applied to upper face 154 can cause rotation of the torsional rotation R of flexible seal ring 131 about a circumferential axis and pivoting of the seal ring 131 about the intersection between lower face 1 SS and second sealing face 160. IB some cases, as energizing pressure is applied to the upper side of the seal ring 131, the resulting compression can cause contact with the plug 1 ! S and /or the cage 1 16 and can cause rotation of the seal ring 131 to provide an interference ill of the sea! ring 131. with the plug 1 15 and the cage 1 16. The upper ia.ee i 54 of the flexible seal ring ! 31 rotates away from the downwardly disposed upper face 162 ol the upper retaining ring 133, and the lower face 158 of the flexible seal ring 131 rotates toward the upper face ! 70 of the lower retaining ring 135. The second front sealing face 160 contacts lip 136 of the first lower retaining ring 135. fluid pressure on face 154 causes the second scaling face 160 to move forward and contact the plug 1 15, hi some instances, rotation of the seal ring ! 31 can accommodate gaps between the plug 1 35 and the cage 1 16 due to engineering tolerances, Irt some instances, thy seal ring 13 ! can he a single continuous ring with an inner diameter sized to receive the plug 1 15 and to engage plug when energizing pressure is applied to the sea! ring 131. In some cases, this configuration can reduce the leakage associated with split ring seals.

It is important to understand thai cartridge seal 130 may comprise the single flexible seal ring 131 or may include both the seal ring 131 and retaining ring 133, Alternatively, retaining ring 135 may he added to elements 131 and 133 to form the cartridge seal 130. The cartridge seal 130 may further include split ring sea! clement 137.

The flexible sea! ring 131 and split ring sea! element 137 may be formed of material such as structural carbon graphite or polyetheretherketone (PEEK) or other material that preferably has properties to maintain structural integrity and strength at high temperatures. The rings 135 and 139 may he made of steel and retaining ring 133 may be formed from woven long strand braided carbon fibers. In some instances,

brittle materials with the desired strength at high temperatures can be used ϊO form the flexible seal ring 131 because the mechanism used to energize the seal can apply compressive forces io the seal ring 131 , In some cases, the compression of the seal ring 131 between the plug 1 15 and the cage 1 16 can exceed the pressure differential s between the upper and lower sides of the seal ring 131.

The angle (A) between the first sealing surface 150 and upper surface 152 is generally about 90 degrees, however, it may range from 80 to 1.00. The angle between faces i52 arid .154 (obtuse angle B) is about 148 degrees. In some embodiments. angle B can range from 110 to 170 degrees. The angle between faces 154 and 156 0 (angle C) is about 121 degrees. In some embodiments, angle C can range from 110 to 140 degrees. The angle between faces 156 and 158 (angle D) is about 102 degrees. In some embodiments, angle D can range from 95 to 130 degrees. The angie between faces 158 ami S 60 (angle H) is about 102 degrees. In some embodiments _* angle IE can range from 90 to 145 degrees. The angle between faces 160 and 1 50 (angle P) is 5 about 155 degrees. In some embodiments, angle F cars range from 140 to 1 75 degrees.

The angle between retaining ring face 170 and flexible seal ring face 158 (angle G) is approximately 12 degrees. IB some embodiments, angle G can range from 1 to 30 degrees (e.g., 5 to 30 degrees) prior to application of energizing pressure Q ι« the seal ring 131.

Cartridge seal 130 may be used in new valves designed expressly for this seal arrangement or may be used in existing control valve designs and used in lieu of other types of seal elements, including but not limited to those illustrated in FiGS. 2 A and 2B. Cartridge seal 130 may be used in newly manufactured valves and may be used as 5 a replacement for other types of seal elements in valves previously in service.

A number of embodiments of the invention have been described. Nevertheless, if will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the above angular dimensions are only intended to be representative of some embodiments of the 0 invention ami arc not intended to limit the configuration of the faces of the various elements of sea! cartridge 130 to the embodiments discussed. Additionally; it will be

understood that the cartridge seal 130 of the present invention may be disposed in a seal groove on the plug instead of in a seal groove on the cage waii. For example, referring to FIG. 8, cartridge seal 230 can engage an outer surface of a plug 215 to form a high temperature and high pressure seal between the outer surface of the plug 215 iixxά the wall of a cage 216 in a control valve. The cartridge seal 230 includes a flexible seal ring 23 ! disposed in a seal groove 238 in the wall of plug 216, The flexible seal ring 231 has a first front sealing face 250 (e.g.. a face on an outer .side of the ring) adapted for sealing contact with the inner surface of the cage 216, a rear face 256 (e.g., a face on an inner side of the ring), and at least one downwardly disposed first upper lace 254, said face 254 being disposed between the front face 250 and the rear lace 256. The seal ring may also include s second upper face 252 disposed between front face 250 and first upper face 254. The- seal ring 231 further includes at least one downwardly disposed lower face 25S. and a second irons, sealing face 260 disposed upwardly between the downwardly disposed lower face 258 and the first front sealing face 250. Cartridge seal 230 operates in a similar fashion to cartridge seal 130 except that directions of rotation and pivoting are reversed relative ic those in cartridge seal 130. Accordingly, other embodiments are within the scope of the following claims.

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