CA1234380A - Gate valve structure - Google Patents
Gate valve structureInfo
- Publication number
- CA1234380A CA1234380A CA000433626A CA433626A CA1234380A CA 1234380 A CA1234380 A CA 1234380A CA 000433626 A CA000433626 A CA 000433626A CA 433626 A CA433626 A CA 433626A CA 1234380 A CA1234380 A CA 1234380A
- Authority
- CA
- Canada
- Prior art keywords
- annular
- seat ring
- seat
- valve
- gate assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K3/00—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing
- F16K3/02—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor
- F16K3/16—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor with special arrangements for separating the sealing faces or for pressing them together
- F16K3/18—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor with special arrangements for separating the sealing faces or for pressing them together by movement of the closure members
- F16K3/184—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor with special arrangements for separating the sealing faces or for pressing them together by movement of the closure members by means of cams
- F16K3/186—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor with special arrangements for separating the sealing faces or for pressing them together by movement of the closure members by means of cams by means of cams of wedge from
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K3/00—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing
- F16K3/02—Gate valves or sliding valves, i.e. cut-off apparatus with closing members having a sliding movement along the seat for opening and closing with flat sealing faces; Packings therefor
- F16K3/0227—Packings
- F16K3/0236—Packings the packing being of a non-resilient material, e.g. ceramic, metal
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Ceramic Engineering (AREA)
- Sliding Valves (AREA)
- Magnetically Actuated Valves (AREA)
Abstract
GATE VALVE STRUCTURE
Abstract of the Disclosure An improved valve seat structure for an expanding gate valve.
The valve seat structure comprises a "floating" seat ring (60) which is loosely received in an annular seat pocket (52) surrounding the flow passage through the valve and is provided with an axial dimension which exceeds the depth of the seat pocket. The front seat face(61) of the seat ring is disposed ad-jacent the gate assembly (24, 26) and is provided with an annular groove (63) with an annular resilient sealing element (64) therein which protrudes beyond the face of the seat ring and forms a ring of sealing contact area encompassing the flow passage (14) when the gate assembly is expanded there-against. The rear face (66) of the seat ring (60) is also provided with an annular groove (63') and a second annular resilient sealing element (64') therein which protrudes beyond the rear of the seat ring. The two annular sealing elements are disposed coaxial and the inner diameter of the front seal-ing element (64) exceeds that of the rear sealing element (64') so that the front sealing element is therefore located a greater radial distance from the flow passage (14) than is the rear sealing element. Accordingly, when the gate assembly is expanded against the seat ring (60), the annular area of the front face of the seat ring which is exposed to flowline pressure exceeds the annular area of the rear face of the seat ring which is exposed to the flowline pressure whereby the seat ring is pressure energized towards the bottom (54) of the seat pocket (52). The annular resilient sealing elements (64, 64') and bottoms of the annular grooves (63, 63') are provided with cooperating wedg-ing surfaces (80, 94 and 80', 94') which act to wedge the front face sealing element (64) towards the gate assembly and the rear sealing element (67) towards the bottom (54) of the seat pocket. The sealing elements increasing the sealing ability of the valve seat in accordance with increasing flowline pres-sure and permit the valve seat structure to compensate for non-parallel condi-tions between the sealing surfaces of the gate assembly and valve seat and the valve body (12).
Abstract of the Disclosure An improved valve seat structure for an expanding gate valve.
The valve seat structure comprises a "floating" seat ring (60) which is loosely received in an annular seat pocket (52) surrounding the flow passage through the valve and is provided with an axial dimension which exceeds the depth of the seat pocket. The front seat face(61) of the seat ring is disposed ad-jacent the gate assembly (24, 26) and is provided with an annular groove (63) with an annular resilient sealing element (64) therein which protrudes beyond the face of the seat ring and forms a ring of sealing contact area encompassing the flow passage (14) when the gate assembly is expanded there-against. The rear face (66) of the seat ring (60) is also provided with an annular groove (63') and a second annular resilient sealing element (64') therein which protrudes beyond the rear of the seat ring. The two annular sealing elements are disposed coaxial and the inner diameter of the front seal-ing element (64) exceeds that of the rear sealing element (64') so that the front sealing element is therefore located a greater radial distance from the flow passage (14) than is the rear sealing element. Accordingly, when the gate assembly is expanded against the seat ring (60), the annular area of the front face of the seat ring which is exposed to flowline pressure exceeds the annular area of the rear face of the seat ring which is exposed to the flowline pressure whereby the seat ring is pressure energized towards the bottom (54) of the seat pocket (52). The annular resilient sealing elements (64, 64') and bottoms of the annular grooves (63, 63') are provided with cooperating wedg-ing surfaces (80, 94 and 80', 94') which act to wedge the front face sealing element (64) towards the gate assembly and the rear sealing element (67) towards the bottom (54) of the seat pocket. The sealing elements increasing the sealing ability of the valve seat in accordance with increasing flowline pres-sure and permit the valve seat structure to compensate for non-parallel condi-tions between the sealing surfaces of the gate assembly and valve seat and the valve body (12).
Description
Case 25~
:~343~
GATE VALVE STRUCTURE
Background of the Invention This invention rela~es generally to gate valves and more parfi-cularly to an improved valve seat structure for e:<panding gate valves"
Gute valves of the expanding gate type typically employ a 5 gate mechanism which is mounted in a valve chamber and is movable therein transversely of the flow passage to open and close the valve~ The gate as-sembly typically comprises a gate member and an attached adjacent segment member which, as the gate assembly approaches the open and closed positions, are expanded transversely of one another by means of cooperating cam sur-10 faces whereby they are forced into tight sealing engagement against seat ringsmounted in the valve body on opposite sicles of the gate assembly for effectingfluid-tight upstream and downstream seals. The outer sides of the ga~e assembly are sealing surfaces which are substaniially parallel to one another and main-tained in a parallel relation as the gate assembly expands in both the open 15 position and the closed position. Upon movement from the operl and closed positions, the gate assembly collapses from its expanded conditiorl to permit reciprocal movement of the gate assembly without developing excessive fric-tion forces between the gate assembly and the seat assemblies of the valve.
Most generally, the seat assemblies for exp~nding gate valves 20 are retained within seat recesses which àre formed within the valve body in -surrounding rela~ionship to the flow passage on each side of the gate assembly.
The valve seats are in the form of seat rings which in one widely used valve structure are pressed into the seat recesses so that the seat will be retained in a fixed position. Idea!ly, the seats provide essentially planar and paral-le! surfaces ~or the gate assembly to contact and seal against when it is in the expanded configuration regardless of whether the gate assembly is in Case 254 :~3~31~
the open position or the closed position. As a practical matter, however, the maintenance of parallelism between the outer sides of the ga~e assembly and the faces of the valve seats is frequently a problem which impairs the ability of the valve to achieve a seul. In addition, the seats do not always remain fixed and they may float or move inwardly toward the gate assembly under high differential pressure conditions. In doing so, the seats move to a position ti~3ht against the gate assembly and drag excessively thereon thus making the valve very difficult to open or close. An alternative construc-tion to the fixed press-fit seat ring is the floating seat arrangement wherein the seat member is designed to float in the seat pocket in the direction of the flow passageway so that it can be moved against the gate sides by ~he fluid pressure. Such floafing seats have the advclntage of being able to seal against the gate and segment members even if there is a lack of parallelism or if there are irregularities in the mating surfaces of the gate assembly and fhe valve seat. A potential disadvantage of ~his type design is that excessive drag can be created between the seat members and the gate assembly when the gate assembly is moved due to the upstream sea~ being forced against the gate assembly by fluid pressure.
Furthermore, under high pressure service conclitions in excess of 10,000 psi, there must be a smaller clearance between the seat ring and seat pocket to preclude damaging of the gate sealing surface by the misalign-ment of the metal seat ring Accordingly, a reduced ability of such a float-ing seat to compensate for non-parallelism is associated with the smaller clearances. In addition, the operating torques for expanding the gate assembly ~25 to achieve a seal under high pressure service conditions ~ecome extremely high so as to make valve operation very difficult.
It is therefore an object of the invention to provide a gate valve of the expanding gate type with a unique improved "floating" valve _ .
seat construction wherein the seat element tends to be retained by differential flowline pressure in the open and closed conditions of the valve ancl as the gate assembly begins its movement to its collapsed condition intermediate its open and closed positions and is able to compensate for non~parallelism be-tween the cooperating sealing surfaces of the valve seat and gate assembly, particularly in high pressure service conditions.
: ~
Case 254 ~;23~3~3~
It is a further object of the invention to provide a gate yalve of the type hving an expansible gate assembly and a novel valve seating means comprising a 1'floating" seat ring which under service conditions is urged by flowline pressure away from the gate assembly and towards the baclc 5 of the seat pocket to eliminate drag forces between the gate assembly and the valve seating means during movement of the gate assernbly between its open and closed positions and is able to compensa~e for non-parallelism condi-tions between the sealing surface of the gate assembly and valve seat and increases its sealing ability in accordance with increasing flowline pressure.
10 Summary of the Invention The invention is an improved valve seat structure for an ex-panding gat~ valve. The valve seat structure comprises a "floating" seat ring which is loosely received in the annular seat pocket and provided with an axial dimension which exceeds the depth of the seat pocket. The front 15 seat face adjacent the gate assembly is provided with an annular groove for accommodating an annular resilient sealing element therein which protrudes beyond the face of the seat ring and forms a ring of sealing contact area when the galie assembly is expanded thereagainst. The rear face oF the seat ring is also provided with an annular groove for accommodating a second 20 annular resilient sealing element which protrudes beyond the rear of the seatring. The two annular sealing elements are disposed coaxial and the inner diameter of the front sealing element exceeds that of the rear sealing element.
The front sealing element is therefore located a greater radial d;stance from the flow passage than is the rear sealing element. Accordingly, when the 25 gate assembly is expanded against the seat ring, the annular area of the front face of the seat ring which is exposed to flowline pressure exceeds the annular area of the rear face of the seat ring which is exposed to the flow-line pressure whereby the seat ring is pressure energi~ed towards the bottorQ
of the seat pocket. The sealing elements and l~ottoms of the annular grooves 30 are provided with cooperating wedging surfaces which act to wedge the front face sealing element towards the gate assembly and the seat face seal-ing element towards the bottom of the seat pocket when subjected to flow-I i ne pressure .
Case '`54 3~3 Brief Description of the Drawinys Fig. 1 is a side elevational view oF an expanding gate valve which is equipped with a pair of floating seats in accordance with a prs-ferred embodiment of the invention, with portions broken away for purposes of illustration;
Fig. 2 is wn enlarged perspective of a seat ring of the inven-tion with a portion broken away to show details of the sealing elements carried in the ring;
Fig. 3 is an enlarged fragmentary sectional view of the central portion of Fig. 1 with the portions of the upstream and downstream valve seat structures nearest the handwheel shown in an enlarged sectional view with the gate assembly expanded in the fully closed position and under fluid pressure from the flow passage; and Fig. ~ is an enlarged fragmentary sectional view similar to Fig. 3 showing the gate assembly in movement from the closed position towards - the fully open position and having just attained its collapsed condition'.
Referring more particularly to the drawings, there is shown in Fig. 1 an expanding type gate valve 10 which is provided with floating seats in accordance with tl-e invention, -The gate valve 10 includes a valve body 12 having an inlet passage 14 and an outlet passage 16. Flanges 18 and 20 are formed on body 12 at the outer ends of passages 14 and 16, respectivelyr to permit easy attachment of the valve body with a flowline (not shown). A
valve chamber 22 is formed in body 12 between the flow passages 14 and 16 and in communica~ion therewith to thereby provide a fluid flow passage through the body.
An expanding type gate assembly is mounted in valve chamber 22 for reciprocal movement therein between an open position and a closed position with respect to flow passages 14 and 16. The gate assembly includes, a gate 2~ located adjacent the downstreclm flow passage 16 and a segment 26 located adjacent the upstream flow passage 14. On the side facing seg-ment 26, gate 24 has oppositely inclined surFaces 28 and 30 on its respective upper and lower portions. Segment 26 has similarly inclined surfaces 32 and 34 on its respective upper and lower portions for cooperative contact with surfaces 28 and 30 of gate 24 to expand and collapse the gate assembly, as Case 25 ~ ;"3~3 !
will be explained in more detail. The outwardly facing sides of the gate and segment are planar surfaces which continually remain parallel to one another and perpendicular to the flow passage. A pair of curved springs 36 (Fig. 1) engage pins on opposite sides of gate 2~ and segment 26 in q manner to continuously urge gate 24 and segment 26 toward one ano~her fo bias the gate assembly toward its collapsed condition. Gate 24 is connected with stem 38 which extends upwardly through a valve bonnet 40 mounted on top of valve body 12. A handwheel 42 is mounted on top of stem 38 to effect up and down movement of gate 24 in a conventioncll manner. A lower stem 44 extends downwardly from the bottom of gate 23 to pressure balance the gate assembly.
When the gate assembly is moved upwardly in response to turn-ing of handwheel ~2, the top end of segment 26 contacts a stop 46 in the valve body to prevent further upward movement of the segment. Continued upward movement of gate 24 results in a lateral expansion of the gate assembly due to the camming action resulting from sliding contact between surfaces 3û
and 34. When the gate assembly is in its upper fully open position as shown in Fig. 1, it is fully expanded and ports 48 formed through the gate and segment members are in alignment with each other and with the flow passges 14 and 16. Movement of gate 24 downward!y from the fully open position causes surfaces 30 and 34 to slide against one another, with assistance from springs 36, until the gate and segment are in the collapsed or minimum width condition as shown in Fig. 4. The springs 36 are attached to opposite sides of the gate assembly and flexed about lugs provided on the gate and segmen.
members in a conventional manner to hold the gate assembly in its collapsed condition as it moves downwardly from the open position toward the closed position. As the gate assembly moYes downwardly, the bottom of segment 26 contacts a lower stop 50, thereby preventing further downward movement of the segment. Continued downward movement of gate 24 causes surfaces 2 and 32 to slide against one another in camming fashion such that the gate assembly is fully expanded when it reaches a lower foliy closed position wherein passages 14 and 16 are blocked. When the ga~e assembly is moved upwardly from the closed position toward the open position, sprin~as 36 urge the gate assembly to its collapsed condition in which it is maintained until Case "~
~ 39~3~
the open position is reached, at which time the gate assembly expands. In the manner described above, the gate assembly is actuated to a fully expand-`
ed condition in both the open and closed positions of the valve and main-tained in a fully collapsed condition when it is in transit between the open 5 and closed positions.
In accordance with the present invention, valve body 12 is provided with a pair of annular recesses 52 which are forrned around flow passages 14 and 16 at locations adjacent valve chamber 22 upstream and down-stream thereof. The recesses 52 are of identical configuration although their 10 orientations are opposite and each recess opens to valve chqmber 22. The annular recesses 52 forrn sea~ pockets in each of which the valve sea~ assemb3y of this invention is inserted. Each seat pocket 52 has a planar annular bottom surface 54 which is oriented perpendicular to the flow passage of the valve and a cylindrical side wall 56 which is formed subs~antially coaxial with the 15 flow passage through the valve.
The valve seat of this invention is shown in an enlarged per-spective view thereof in Fig. ~. The valve seat comprises a metallic sea~
ring 60, the central bore of which corresponds in diameter and configuration to that of the flow passage through the valve. The axial dimension of the ~20 ring 60 is slightly larger than the depth of a seat pocket 52, so that when the seat ring is fully seated in the pocket 52, the ring 60 protrudes into the valve chamber 22 and its front face 61 is disposed to engage a planar side wall of the gate assembly when the gate assembly is expanded thereagains~.
- Further, according to the invention, the external diameter of the seat ring 25 60 is slightly less than the diameter of the seat pocket so that a clearance exists between the external cylindrical wall 6~ of the seat ring 60 and the cylindrical side wall 56 of the seat pocket. Accordingly, the seat ring 60 is designed to fit looseiy in the seat pocket in a "floating" relationship therewith and can therefore orient, when necessary, to establish a face-to-30 face contact with the sealing surface of the gate assembly when the gateassembly is expanded thereagainst.
The front face 61 of the seat ring is Formed with an annular groove 63 therein which is concentric with the bore of the ring 60 and in surrounding relcttion to the valve flow passage. The groove 63 accommodutes 35 an annular resilient sealing member 64 which is adapted to establish a seal .
3~380 with the face of -the segment of the gate assembly when the gate assembly is in its expanded condition. Accordingly, the axial dimension of the annular seal 64 exceeds the depth of the groove 63 so the seal 64 protrudes beyond the face 61 of the seat ring 60. For low pressure and low tempera-ture service conditions, the resilient seal 64 may be of "Teflon"* or other similar deformable plastic material. Howeverr for high pressure service, generally pressures in excess of 10,000 psi, or at high operat-ing temperatures greater than 500F. (260C), a metallic sealing member is required to provide the necessary structural strength. In such instances, an aluminum bronze alloy or a soft stainless steel, such as 316 stainless steel, would be suitable material.
Also, as best seen in Fig. 2, the back face 66 of the seat ring 60 is provided with an annular groove 63' which corresponds in dimensions and configuration to the annular groove 63. A resilient sealing member 64', which is identical in radial cross section to the sealing member 64 and of the same material composition, is installed therein. Both of the annular sealing members 64, 64' are disposed in a coaxial relationship with the bore of the seat ring 60 and the flow passage through the valve.
However, the inner diameter of the annular sealing member 64 in the front face 61 of the seat ring exceeds the inner diameter of the annular seal-ing member 64' in the back face 66 and, therefore, the sealing member 64 is disposed a greater distance from the flow passage than the sealing member 64' for purposes to be hereinafter described.
It is also to be noted that the clearance between the seat ring and the circumferential wall of the seat pocket must necessarily be smaller than that which is permissible when using plastic annular sealing members since under high pressure conditions the edge of the seat ring tends to do damage to the surface of the gate element. In one embodiment of the invention, a typical diametrical tolerance between the seat ring and seat pocket is .013 inches. For purposes of illustration, the various clearances between the groove walls in the seat rings and the sealing elements have necessarily been exaggerated.
In the invention, the configuration of the annular grooves 63, 63' in the front and rear faces of the seat ring 60 is as shown in U.S. Patent No. 4r320,890 -to Meyer et al. The annular groove 63, for example, is provided with * Trade ~ark Case 25^~
:~2 3'~3~
a botlom 76 which includes a flat bottom portion 78 tha~ is generally per~
pendicular to and adjacent to the inner groove sidc 72 which is the side nearest the flow passage, and a frusto-conicai bottom portion 80 that is formed adjacent the outer groove side 74. The frusto-conical bottom portion 5 80 comprises between approximately twenty-Five percent (25%) and approxi-mately seventy percent (70%j of the width of the annular groove 63 and between approximately twenty percent (20%) and approxirnately fifty percent (50%) of the depth of the groove along the outer groove side 74. Accord-ingly, the frusto-conical bottom portion is disposed from the flat bottom portion 10 78 at an angle which is within a range between approximately thirty degr0es (30) and approximately sixty t60).
The annular sealing member 64 is loosely recei~ *d in the an-nular groove 63 For relatively unrestrained movement therein. The annular face seal 64 includes front and rear seal faces 84 and 86 joined by inner and 15 outer seal sides 88 and 90. The axial dimension of the face seal 64 is be-tween approximately 1.4 and 1.6 times the thickness thereof. The rear seal face 86 includes a flat rear portion 92 that is generally perpendicular to and adjacent the inner seal side 88 and a frusto-conical rear portion 94 that is formed adjacent outer seal side 90. The frusto-conical rear portion 94 is 20 disposed from the flat rear portion 92 at an angle in the range between ap-proximately thirty degrees (30) and approximately six~y degrees (60) but in conformity with the cone angle of the frusto-conical bottom 80 of the groove 63.
In a specific embodiment of an expancling gate valve of a ~5 standard commercial size, the front seal face 84, when the gate is in col~
iupsed condition, extends past the front seat face by a distance "E" in the range of between approximately 0.002 inches (0.0051 cm) and approximately 0.015 inches (0 0381 cm). With the face seal 64 sitting loosely in the annular groove 63 with its frusto-conical surface engaging the frusto-conical 30 bottom surface of the groove, the clearance between the groove side 74 and seal side 90 is in the range of 0.001 inches to 0 015 inches. The clearance between the seal side 88 and groove side 72 is approximately 0.021 inches which is the same as the clearance between the rear seal face 92 and the groove bottom 78.
Case '~54 3~23~3~3 _9 .
The seat ring illustrated in Fig. 2 is described with reference numerals applied to the seating assembly used on the upstream side Or the gate assembly. The seut ring and seat assembly used on the downstream side is identical to that shown in Fig. 2 and is installed in a reverse orientatic.n 3 fo the upstream seat assembly. For ease of description, elements of the downstrearn seat assembly which correspond to those in the upstream seat as-sembly are identified with the same reference numerals but with a subscript appended thereto.
When the gate assembly of the valve is moved to either the 10 open or closed position by operation of the hqndwheel 42, the gate assembly is expanded against the seat ring elements on both the ups~ream and down-stream sides of the gate assembly. As shown in Fig. 3 wherein the gate assembly is iilustrated in the closed expanded condition, the sealing element 64 is compressed by the segment 26 and establishes a fluid-tight seal between 15 the contacting faces of the seat ring 60 and the seament 26. The sealing element 64' also establishes a fluid-tight seal between the back face o6 of the seat ring 60 and the end wall 5~ of the seat pocl<et.
It is to be noted that the inner edge of the sealing element 64 is located a distance from the flow passage 14 which exceeds the distance ~0 of the sealing element 64' from the flow passage 14. Accordingly, on the upstream side, pressurized fluid from the passage 14 will flow between the face 61 of the seat ring 60 and the sealing face of the segment 26 to where it is blocked by the sealing element o4. Similar!y, pressurized fluid will flow between the back face 66 of the sea~ ring and the end wall 54 of the 25 seat poclcet to the inner edge of the sealing element 64'. ~herefore, the annuiar area of surface of the front face 61 which is exposed to fluid pressure exceeds the annular area of surface of the back face 66 which is exposed to fluid pressure and the resultant differential force acts to urge the seat ring 60 more tightly against the back of the sec~ pocket to establish an even 30 tighter seal at the back of the seat ring.
In addition, when there is initial movement of the gate assembly away from its fully open or fully closed position and the gate asscmbly begins to collapse, as shown in Fig. ~, this differential force resulting from the difference of exposed areas causes the seat ring 60 to be pressure actuated Case ~54 ~i~3~3~0 -1~
towards the end wall 54 of the seat pockef rather than iowards the gate as-sembly. This prevents the seat ring from being forced out of the pocl~et and `
following towards the gate element to impose a drag thereon.
Although it is usually only the upstream valve seat that presents 5 a problem with respect to dragging against the collapsed gate assembly, the downstream seat may in some cases pose a problem in this regard, particularly when reverse flow conditions are encountered. Accordingly, it is contem-lated that both the upstream and downstream seats will normally be constructed in accordance with the invention.
~0 While the relative locations of the annular sealing elements with respect to the flow passage results in pressure energizing of the seat ring 60 as to urge its retention in the seat pocket to serve the purposes of enhancing the seaiing effectiveness of the valve seat assembly and also avoid any drag-ging contact of the seat ring with the gate assembly, the particular structure 15 of the annular resilient sealing elements and the accommodating grooves in the front and rear faces of the seat ring enables the valve seats to compensate for out of paratlel conditions which may exist between the cooperating sealing surfaces of the gate assembly and valve seat and between the seat ring and the valve body even though there is a very small clearance between the seat 20 ring and the seat pocket. Furthermore, the cooperating wedging surfaces of the annular resilient sealing elements and the associated annular grooves in which they are received, act to establish more effective seals between the seat assembly and the valve body and gate assembly under pressure conditions and this effectiveness of the seais increases with increasing fluid pressure in 25 the flow passage as described below.
As the gate assembiy reaches its closed position, it expands against botil upstream and downstream annular face seals 64 and 64A so that they are axially compressed to form a fluid-tight seal between themselves and the gate assembly and their respective annular grooves 63 and b3A. Also, 30 the rear face seals 64' and 64A' in the upstream and downstream seat assem-blies are likewise axially compressed to establish seals between the seat rings and the seat pocket bottoms 54 and 54A.
With respect to upstream annular ~ce seal o4, fluid from inlet flow passage 14 then travels along the upstream side of segment 26 and into ,,:
Case 254 3g~3l~
upstream annular groove 63, and is contained within a space between inner groove side 72 and inner seal side 88. The fluid does not leak past either the front or rear seal faces of annular face seal 64 due to the above described seal created between it and the gate assembly and upstream annular grooye 5 63. As the fluid pressure builds within the space between the inner groove and seal sides, upstream annular face seal element bd, is forced to fravel on its frusto-conical rear portion M up frusto-conical bottom portion 8û. As upstream annular face seal 64 travels up frusto-conical bottom portion 80, it moves inwardly towards the gute assembly while the gate assembly simultaneous-10 Iy expands outwardly towards it. Fluid pressure built up in the space definedbe~ween flat bottom portion 78 of groove 63 and flat rear portion 92 of seal 64 also forces upstream annular face seal b4 to travel inwardly toward valve chamber 22 and the gate assembly. Thus, an effective sel which surrounds the flow passage is created between front seal face 84 and the gate assembly, 15 and between frusto-conical rear portion 94 and annular groove 63. Because fluid from the flowline actually forces the upstream annular face seal to wedge fowards the gafe assembly, the effectiveness of the seal created by the an-nular face seal increases with increasing flow passa~e fluid pressure. The inward travel of the annular face seal towards the gate assembly reduces the 20 distance the gate assembly must move against the direction of fluid flow in the flow passage. It can thus be seen that the ability of annular face seal 64 to move inwardly in response to fluid pressure in the flow passage faci-litates the formation of an effective seal on the upstream side of the gate assembly without the need for exerting operating torques on the gate assembly
:~343~
GATE VALVE STRUCTURE
Background of the Invention This invention rela~es generally to gate valves and more parfi-cularly to an improved valve seat structure for e:<panding gate valves"
Gute valves of the expanding gate type typically employ a 5 gate mechanism which is mounted in a valve chamber and is movable therein transversely of the flow passage to open and close the valve~ The gate as-sembly typically comprises a gate member and an attached adjacent segment member which, as the gate assembly approaches the open and closed positions, are expanded transversely of one another by means of cooperating cam sur-10 faces whereby they are forced into tight sealing engagement against seat ringsmounted in the valve body on opposite sicles of the gate assembly for effectingfluid-tight upstream and downstream seals. The outer sides of the ga~e assembly are sealing surfaces which are substaniially parallel to one another and main-tained in a parallel relation as the gate assembly expands in both the open 15 position and the closed position. Upon movement from the operl and closed positions, the gate assembly collapses from its expanded conditiorl to permit reciprocal movement of the gate assembly without developing excessive fric-tion forces between the gate assembly and the seat assemblies of the valve.
Most generally, the seat assemblies for exp~nding gate valves 20 are retained within seat recesses which àre formed within the valve body in -surrounding rela~ionship to the flow passage on each side of the gate assembly.
The valve seats are in the form of seat rings which in one widely used valve structure are pressed into the seat recesses so that the seat will be retained in a fixed position. Idea!ly, the seats provide essentially planar and paral-le! surfaces ~or the gate assembly to contact and seal against when it is in the expanded configuration regardless of whether the gate assembly is in Case 254 :~3~31~
the open position or the closed position. As a practical matter, however, the maintenance of parallelism between the outer sides of the ga~e assembly and the faces of the valve seats is frequently a problem which impairs the ability of the valve to achieve a seul. In addition, the seats do not always remain fixed and they may float or move inwardly toward the gate assembly under high differential pressure conditions. In doing so, the seats move to a position ti~3ht against the gate assembly and drag excessively thereon thus making the valve very difficult to open or close. An alternative construc-tion to the fixed press-fit seat ring is the floating seat arrangement wherein the seat member is designed to float in the seat pocket in the direction of the flow passageway so that it can be moved against the gate sides by ~he fluid pressure. Such floafing seats have the advclntage of being able to seal against the gate and segment members even if there is a lack of parallelism or if there are irregularities in the mating surfaces of the gate assembly and fhe valve seat. A potential disadvantage of ~his type design is that excessive drag can be created between the seat members and the gate assembly when the gate assembly is moved due to the upstream sea~ being forced against the gate assembly by fluid pressure.
Furthermore, under high pressure service conclitions in excess of 10,000 psi, there must be a smaller clearance between the seat ring and seat pocket to preclude damaging of the gate sealing surface by the misalign-ment of the metal seat ring Accordingly, a reduced ability of such a float-ing seat to compensate for non-parallelism is associated with the smaller clearances. In addition, the operating torques for expanding the gate assembly ~25 to achieve a seal under high pressure service conditions ~ecome extremely high so as to make valve operation very difficult.
It is therefore an object of the invention to provide a gate valve of the expanding gate type with a unique improved "floating" valve _ .
seat construction wherein the seat element tends to be retained by differential flowline pressure in the open and closed conditions of the valve ancl as the gate assembly begins its movement to its collapsed condition intermediate its open and closed positions and is able to compensate for non~parallelism be-tween the cooperating sealing surfaces of the valve seat and gate assembly, particularly in high pressure service conditions.
: ~
Case 254 ~;23~3~3~
It is a further object of the invention to provide a gate yalve of the type hving an expansible gate assembly and a novel valve seating means comprising a 1'floating" seat ring which under service conditions is urged by flowline pressure away from the gate assembly and towards the baclc 5 of the seat pocket to eliminate drag forces between the gate assembly and the valve seating means during movement of the gate assernbly between its open and closed positions and is able to compensa~e for non-parallelism condi-tions between the sealing surface of the gate assembly and valve seat and increases its sealing ability in accordance with increasing flowline pressure.
10 Summary of the Invention The invention is an improved valve seat structure for an ex-panding gat~ valve. The valve seat structure comprises a "floating" seat ring which is loosely received in the annular seat pocket and provided with an axial dimension which exceeds the depth of the seat pocket. The front 15 seat face adjacent the gate assembly is provided with an annular groove for accommodating an annular resilient sealing element therein which protrudes beyond the face of the seat ring and forms a ring of sealing contact area when the galie assembly is expanded thereagainst. The rear face oF the seat ring is also provided with an annular groove for accommodating a second 20 annular resilient sealing element which protrudes beyond the rear of the seatring. The two annular sealing elements are disposed coaxial and the inner diameter of the front sealing element exceeds that of the rear sealing element.
The front sealing element is therefore located a greater radial d;stance from the flow passage than is the rear sealing element. Accordingly, when the 25 gate assembly is expanded against the seat ring, the annular area of the front face of the seat ring which is exposed to flowline pressure exceeds the annular area of the rear face of the seat ring which is exposed to the flow-line pressure whereby the seat ring is pressure energi~ed towards the bottorQ
of the seat pocket. The sealing elements and l~ottoms of the annular grooves 30 are provided with cooperating wedging surfaces which act to wedge the front face sealing element towards the gate assembly and the seat face seal-ing element towards the bottom of the seat pocket when subjected to flow-I i ne pressure .
Case '`54 3~3 Brief Description of the Drawinys Fig. 1 is a side elevational view oF an expanding gate valve which is equipped with a pair of floating seats in accordance with a prs-ferred embodiment of the invention, with portions broken away for purposes of illustration;
Fig. 2 is wn enlarged perspective of a seat ring of the inven-tion with a portion broken away to show details of the sealing elements carried in the ring;
Fig. 3 is an enlarged fragmentary sectional view of the central portion of Fig. 1 with the portions of the upstream and downstream valve seat structures nearest the handwheel shown in an enlarged sectional view with the gate assembly expanded in the fully closed position and under fluid pressure from the flow passage; and Fig. ~ is an enlarged fragmentary sectional view similar to Fig. 3 showing the gate assembly in movement from the closed position towards - the fully open position and having just attained its collapsed condition'.
Referring more particularly to the drawings, there is shown in Fig. 1 an expanding type gate valve 10 which is provided with floating seats in accordance with tl-e invention, -The gate valve 10 includes a valve body 12 having an inlet passage 14 and an outlet passage 16. Flanges 18 and 20 are formed on body 12 at the outer ends of passages 14 and 16, respectivelyr to permit easy attachment of the valve body with a flowline (not shown). A
valve chamber 22 is formed in body 12 between the flow passages 14 and 16 and in communica~ion therewith to thereby provide a fluid flow passage through the body.
An expanding type gate assembly is mounted in valve chamber 22 for reciprocal movement therein between an open position and a closed position with respect to flow passages 14 and 16. The gate assembly includes, a gate 2~ located adjacent the downstreclm flow passage 16 and a segment 26 located adjacent the upstream flow passage 14. On the side facing seg-ment 26, gate 24 has oppositely inclined surFaces 28 and 30 on its respective upper and lower portions. Segment 26 has similarly inclined surfaces 32 and 34 on its respective upper and lower portions for cooperative contact with surfaces 28 and 30 of gate 24 to expand and collapse the gate assembly, as Case 25 ~ ;"3~3 !
will be explained in more detail. The outwardly facing sides of the gate and segment are planar surfaces which continually remain parallel to one another and perpendicular to the flow passage. A pair of curved springs 36 (Fig. 1) engage pins on opposite sides of gate 2~ and segment 26 in q manner to continuously urge gate 24 and segment 26 toward one ano~her fo bias the gate assembly toward its collapsed condition. Gate 24 is connected with stem 38 which extends upwardly through a valve bonnet 40 mounted on top of valve body 12. A handwheel 42 is mounted on top of stem 38 to effect up and down movement of gate 24 in a conventioncll manner. A lower stem 44 extends downwardly from the bottom of gate 23 to pressure balance the gate assembly.
When the gate assembly is moved upwardly in response to turn-ing of handwheel ~2, the top end of segment 26 contacts a stop 46 in the valve body to prevent further upward movement of the segment. Continued upward movement of gate 24 results in a lateral expansion of the gate assembly due to the camming action resulting from sliding contact between surfaces 3û
and 34. When the gate assembly is in its upper fully open position as shown in Fig. 1, it is fully expanded and ports 48 formed through the gate and segment members are in alignment with each other and with the flow passges 14 and 16. Movement of gate 24 downward!y from the fully open position causes surfaces 30 and 34 to slide against one another, with assistance from springs 36, until the gate and segment are in the collapsed or minimum width condition as shown in Fig. 4. The springs 36 are attached to opposite sides of the gate assembly and flexed about lugs provided on the gate and segmen.
members in a conventional manner to hold the gate assembly in its collapsed condition as it moves downwardly from the open position toward the closed position. As the gate assembly moYes downwardly, the bottom of segment 26 contacts a lower stop 50, thereby preventing further downward movement of the segment. Continued downward movement of gate 24 causes surfaces 2 and 32 to slide against one another in camming fashion such that the gate assembly is fully expanded when it reaches a lower foliy closed position wherein passages 14 and 16 are blocked. When the ga~e assembly is moved upwardly from the closed position toward the open position, sprin~as 36 urge the gate assembly to its collapsed condition in which it is maintained until Case "~
~ 39~3~
the open position is reached, at which time the gate assembly expands. In the manner described above, the gate assembly is actuated to a fully expand-`
ed condition in both the open and closed positions of the valve and main-tained in a fully collapsed condition when it is in transit between the open 5 and closed positions.
In accordance with the present invention, valve body 12 is provided with a pair of annular recesses 52 which are forrned around flow passages 14 and 16 at locations adjacent valve chamber 22 upstream and down-stream thereof. The recesses 52 are of identical configuration although their 10 orientations are opposite and each recess opens to valve chqmber 22. The annular recesses 52 forrn sea~ pockets in each of which the valve sea~ assemb3y of this invention is inserted. Each seat pocket 52 has a planar annular bottom surface 54 which is oriented perpendicular to the flow passage of the valve and a cylindrical side wall 56 which is formed subs~antially coaxial with the 15 flow passage through the valve.
The valve seat of this invention is shown in an enlarged per-spective view thereof in Fig. ~. The valve seat comprises a metallic sea~
ring 60, the central bore of which corresponds in diameter and configuration to that of the flow passage through the valve. The axial dimension of the ~20 ring 60 is slightly larger than the depth of a seat pocket 52, so that when the seat ring is fully seated in the pocket 52, the ring 60 protrudes into the valve chamber 22 and its front face 61 is disposed to engage a planar side wall of the gate assembly when the gate assembly is expanded thereagains~.
- Further, according to the invention, the external diameter of the seat ring 25 60 is slightly less than the diameter of the seat pocket so that a clearance exists between the external cylindrical wall 6~ of the seat ring 60 and the cylindrical side wall 56 of the seat pocket. Accordingly, the seat ring 60 is designed to fit looseiy in the seat pocket in a "floating" relationship therewith and can therefore orient, when necessary, to establish a face-to-30 face contact with the sealing surface of the gate assembly when the gateassembly is expanded thereagainst.
The front face 61 of the seat ring is Formed with an annular groove 63 therein which is concentric with the bore of the ring 60 and in surrounding relcttion to the valve flow passage. The groove 63 accommodutes 35 an annular resilient sealing member 64 which is adapted to establish a seal .
3~380 with the face of -the segment of the gate assembly when the gate assembly is in its expanded condition. Accordingly, the axial dimension of the annular seal 64 exceeds the depth of the groove 63 so the seal 64 protrudes beyond the face 61 of the seat ring 60. For low pressure and low tempera-ture service conditions, the resilient seal 64 may be of "Teflon"* or other similar deformable plastic material. Howeverr for high pressure service, generally pressures in excess of 10,000 psi, or at high operat-ing temperatures greater than 500F. (260C), a metallic sealing member is required to provide the necessary structural strength. In such instances, an aluminum bronze alloy or a soft stainless steel, such as 316 stainless steel, would be suitable material.
Also, as best seen in Fig. 2, the back face 66 of the seat ring 60 is provided with an annular groove 63' which corresponds in dimensions and configuration to the annular groove 63. A resilient sealing member 64', which is identical in radial cross section to the sealing member 64 and of the same material composition, is installed therein. Both of the annular sealing members 64, 64' are disposed in a coaxial relationship with the bore of the seat ring 60 and the flow passage through the valve.
However, the inner diameter of the annular sealing member 64 in the front face 61 of the seat ring exceeds the inner diameter of the annular seal-ing member 64' in the back face 66 and, therefore, the sealing member 64 is disposed a greater distance from the flow passage than the sealing member 64' for purposes to be hereinafter described.
It is also to be noted that the clearance between the seat ring and the circumferential wall of the seat pocket must necessarily be smaller than that which is permissible when using plastic annular sealing members since under high pressure conditions the edge of the seat ring tends to do damage to the surface of the gate element. In one embodiment of the invention, a typical diametrical tolerance between the seat ring and seat pocket is .013 inches. For purposes of illustration, the various clearances between the groove walls in the seat rings and the sealing elements have necessarily been exaggerated.
In the invention, the configuration of the annular grooves 63, 63' in the front and rear faces of the seat ring 60 is as shown in U.S. Patent No. 4r320,890 -to Meyer et al. The annular groove 63, for example, is provided with * Trade ~ark Case 25^~
:~2 3'~3~
a botlom 76 which includes a flat bottom portion 78 tha~ is generally per~
pendicular to and adjacent to the inner groove sidc 72 which is the side nearest the flow passage, and a frusto-conicai bottom portion 80 that is formed adjacent the outer groove side 74. The frusto-conical bottom portion 5 80 comprises between approximately twenty-Five percent (25%) and approxi-mately seventy percent (70%j of the width of the annular groove 63 and between approximately twenty percent (20%) and approxirnately fifty percent (50%) of the depth of the groove along the outer groove side 74. Accord-ingly, the frusto-conical bottom portion is disposed from the flat bottom portion 10 78 at an angle which is within a range between approximately thirty degr0es (30) and approximately sixty t60).
The annular sealing member 64 is loosely recei~ *d in the an-nular groove 63 For relatively unrestrained movement therein. The annular face seal 64 includes front and rear seal faces 84 and 86 joined by inner and 15 outer seal sides 88 and 90. The axial dimension of the face seal 64 is be-tween approximately 1.4 and 1.6 times the thickness thereof. The rear seal face 86 includes a flat rear portion 92 that is generally perpendicular to and adjacent the inner seal side 88 and a frusto-conical rear portion 94 that is formed adjacent outer seal side 90. The frusto-conical rear portion 94 is 20 disposed from the flat rear portion 92 at an angle in the range between ap-proximately thirty degrees (30) and approximately six~y degrees (60) but in conformity with the cone angle of the frusto-conical bottom 80 of the groove 63.
In a specific embodiment of an expancling gate valve of a ~5 standard commercial size, the front seal face 84, when the gate is in col~
iupsed condition, extends past the front seat face by a distance "E" in the range of between approximately 0.002 inches (0.0051 cm) and approximately 0.015 inches (0 0381 cm). With the face seal 64 sitting loosely in the annular groove 63 with its frusto-conical surface engaging the frusto-conical 30 bottom surface of the groove, the clearance between the groove side 74 and seal side 90 is in the range of 0.001 inches to 0 015 inches. The clearance between the seal side 88 and groove side 72 is approximately 0.021 inches which is the same as the clearance between the rear seal face 92 and the groove bottom 78.
Case '~54 3~23~3~3 _9 .
The seat ring illustrated in Fig. 2 is described with reference numerals applied to the seating assembly used on the upstream side Or the gate assembly. The seut ring and seat assembly used on the downstream side is identical to that shown in Fig. 2 and is installed in a reverse orientatic.n 3 fo the upstream seat assembly. For ease of description, elements of the downstrearn seat assembly which correspond to those in the upstream seat as-sembly are identified with the same reference numerals but with a subscript appended thereto.
When the gate assembly of the valve is moved to either the 10 open or closed position by operation of the hqndwheel 42, the gate assembly is expanded against the seat ring elements on both the ups~ream and down-stream sides of the gate assembly. As shown in Fig. 3 wherein the gate assembly is iilustrated in the closed expanded condition, the sealing element 64 is compressed by the segment 26 and establishes a fluid-tight seal between 15 the contacting faces of the seat ring 60 and the seament 26. The sealing element 64' also establishes a fluid-tight seal between the back face o6 of the seat ring 60 and the end wall 5~ of the seat pocl<et.
It is to be noted that the inner edge of the sealing element 64 is located a distance from the flow passage 14 which exceeds the distance ~0 of the sealing element 64' from the flow passage 14. Accordingly, on the upstream side, pressurized fluid from the passage 14 will flow between the face 61 of the seat ring 60 and the sealing face of the segment 26 to where it is blocked by the sealing element o4. Similar!y, pressurized fluid will flow between the back face 66 of the sea~ ring and the end wall 54 of the 25 seat poclcet to the inner edge of the sealing element 64'. ~herefore, the annuiar area of surface of the front face 61 which is exposed to fluid pressure exceeds the annular area of surface of the back face 66 which is exposed to fluid pressure and the resultant differential force acts to urge the seat ring 60 more tightly against the back of the sec~ pocket to establish an even 30 tighter seal at the back of the seat ring.
In addition, when there is initial movement of the gate assembly away from its fully open or fully closed position and the gate asscmbly begins to collapse, as shown in Fig. ~, this differential force resulting from the difference of exposed areas causes the seat ring 60 to be pressure actuated Case ~54 ~i~3~3~0 -1~
towards the end wall 54 of the seat pockef rather than iowards the gate as-sembly. This prevents the seat ring from being forced out of the pocl~et and `
following towards the gate element to impose a drag thereon.
Although it is usually only the upstream valve seat that presents 5 a problem with respect to dragging against the collapsed gate assembly, the downstream seat may in some cases pose a problem in this regard, particularly when reverse flow conditions are encountered. Accordingly, it is contem-lated that both the upstream and downstream seats will normally be constructed in accordance with the invention.
~0 While the relative locations of the annular sealing elements with respect to the flow passage results in pressure energizing of the seat ring 60 as to urge its retention in the seat pocket to serve the purposes of enhancing the seaiing effectiveness of the valve seat assembly and also avoid any drag-ging contact of the seat ring with the gate assembly, the particular structure 15 of the annular resilient sealing elements and the accommodating grooves in the front and rear faces of the seat ring enables the valve seats to compensate for out of paratlel conditions which may exist between the cooperating sealing surfaces of the gate assembly and valve seat and between the seat ring and the valve body even though there is a very small clearance between the seat 20 ring and the seat pocket. Furthermore, the cooperating wedging surfaces of the annular resilient sealing elements and the associated annular grooves in which they are received, act to establish more effective seals between the seat assembly and the valve body and gate assembly under pressure conditions and this effectiveness of the seais increases with increasing fluid pressure in 25 the flow passage as described below.
As the gate assembiy reaches its closed position, it expands against botil upstream and downstream annular face seals 64 and 64A so that they are axially compressed to form a fluid-tight seal between themselves and the gate assembly and their respective annular grooves 63 and b3A. Also, 30 the rear face seals 64' and 64A' in the upstream and downstream seat assem-blies are likewise axially compressed to establish seals between the seat rings and the seat pocket bottoms 54 and 54A.
With respect to upstream annular ~ce seal o4, fluid from inlet flow passage 14 then travels along the upstream side of segment 26 and into ,,:
Case 254 3g~3l~
upstream annular groove 63, and is contained within a space between inner groove side 72 and inner seal side 88. The fluid does not leak past either the front or rear seal faces of annular face seal 64 due to the above described seal created between it and the gate assembly and upstream annular grooye 5 63. As the fluid pressure builds within the space between the inner groove and seal sides, upstream annular face seal element bd, is forced to fravel on its frusto-conical rear portion M up frusto-conical bottom portion 8û. As upstream annular face seal 64 travels up frusto-conical bottom portion 80, it moves inwardly towards the gute assembly while the gate assembly simultaneous-10 Iy expands outwardly towards it. Fluid pressure built up in the space definedbe~ween flat bottom portion 78 of groove 63 and flat rear portion 92 of seal 64 also forces upstream annular face seal b4 to travel inwardly toward valve chamber 22 and the gate assembly. Thus, an effective sel which surrounds the flow passage is created between front seal face 84 and the gate assembly, 15 and between frusto-conical rear portion 94 and annular groove 63. Because fluid from the flowline actually forces the upstream annular face seal to wedge fowards the gafe assembly, the effectiveness of the seal created by the an-nular face seal increases with increasing flow passa~e fluid pressure. The inward travel of the annular face seal towards the gate assembly reduces the 20 distance the gate assembly must move against the direction of fluid flow in the flow passage. It can thus be seen that the ability of annular face seal 64 to move inwardly in response to fluid pressure in the flow passage faci-litates the formation of an effective seal on the upstream side of the gate assembly without the need for exerting operating torques on the gate assembly
2~ of such degrees as has been required in the past.
As regards the annular sealing element b4' in the rear lFace of the seat ring bO, fluid from the flow passage enters between the rear face 66 of the seat ring and the bottom 54 of the séat pocket fo be contained within the space between the inner groove side 72' ancl the inner seal side 88'. As 30 the pressure builds within this space between thé inner groove and seal sides, the sealing element 645 is forced to travel on its frusto-conical rear portion ~4' up the frusto-conical groove bottom 80', thus causing it to move towards the bottom wall 54 of the seat pocket. The resulting compression of the sealing element 64' enhances the effectiveness of the seal between its Case ~4 ~;~3~3 frusto-conical surface 94r and that of the seat ring 60 as well as the seal between the sealing element 64' and the bottom wall ~4 of the seat pocket.
With respect to the downstream annular face seal 6~A when the gate assembly is placed in its closed expanded position, the downstream 5 annular face seal 64A remains slightly axially compressed between frusto-conical bottom portion 80A of downstream annular groove 63~ due to the expansion of the ga~e assembly. ~lowever, because fluid does not flow into downstream annular groove 63A, downstream annulaJ face seal 64A, does not wedge inwardly towards the valve chamber 22.
Fig. 1 illustrates the gate assembly in its open position in whi~h it is also fully expanded and the ports ~8 through gate 24 and segment 26 are fully aligned. As the gate assembly reaches its open ,~osition, both the up-stream and downstream annular face seals 64 and 6~A are axially compressed to initially seal ag~inst the gate ssem~ly and thPir respective annular grooves15 in a manner similar to tha~ when the gate assembly reaches its closed position.
~lowever, because fluid from the flow passage has entered the valve charnber 22 during the movernent of the gate assembly the fluid pressure on both sides of the upstream annular face seals 64 and 64! j5 equal, and the upstream annular face seals are not axially compressed any Further by wedging cgainst 20 their frusto-conical groo~e bottoms 80 and 83'. ~he valve chamber pressure also precludes any further axial compression and wedging of the downstr0am seats 64A and 64A'.
With reference to Fig. 4, wherein the gate assembly is shown in transit from the closed position to the open position and has just assumed 25 its fully collapsed condition, the frusto-conical rear portion 9~ of the up-stream face seal 64 moves away from the frusto-conical bottom portion 80 of the groove 63 and fluid contained between the inner sicles and flat portions of the upstream annular groove 63 and the face seal 64 flows past these frusto-conical surfaces 94, 80 to the outer sides of the annular groove 63 30 and fslce seal 64 thereby equalizing the fluid pressure on both sides of the upstream annular face seal 64. Once the fluid pressure on both sides o the upstream annular face seGI 64 is equalized, the seal 64 moves into a wiping relationship with the gate assembly wherein the front seal face 84 is spaced apart a small distance from the gate assembly which reduces the 35 amount of contaminants that can enter the valve chan~ber 22. In like manner, .
Case 2 ~3~3 the àownstream seal 6~A assures a similar wipiny relationship with the gate assembly wherein the sealing elements 64, o4~ do not impede or bind the movement of the gate assembly.
The invention described herein is directed to floating seats for 5 expanding gate valves which are pressure energized in a manner to minimize "drag" between the valve seats and the gate assembly and are also adapted to compensate for conditions of non-parallelism between the gate assembly sealing surfaces and the seat rings and betweon the seat rings and the bottoms of the seat pockets. At the same time, this unique seat and seal ring as-10 sembly allows the valve to effect a fluid-tight seal with the application of lesser operational torque than is generally r~quired for conventional gate valves with floating seats and particularly so for operations under high pressure ser-vice conditions. Also, its sealing effectiveness increases with increasing pressure conditions.
While the invention has been illustrated with respect to a balanced stem gate vulve, the invention could be used as well with an un-balanced gate valve. Furthermore, it is to be understood that the foregoing description of the invention has been presented for purposes of illustration andexplanation and is not intended as limiting the invention to the precise forrn 20 disclosed as changes in details of construction may be made by those skilled in the art, within the scope of the appended claims, without departing frorn the spirit of the invention.
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.
As regards the annular sealing element b4' in the rear lFace of the seat ring bO, fluid from the flow passage enters between the rear face 66 of the seat ring and the bottom 54 of the séat pocket fo be contained within the space between the inner groove side 72' ancl the inner seal side 88'. As 30 the pressure builds within this space between thé inner groove and seal sides, the sealing element 645 is forced to travel on its frusto-conical rear portion ~4' up the frusto-conical groove bottom 80', thus causing it to move towards the bottom wall 54 of the seat pocket. The resulting compression of the sealing element 64' enhances the effectiveness of the seal between its Case ~4 ~;~3~3 frusto-conical surface 94r and that of the seat ring 60 as well as the seal between the sealing element 64' and the bottom wall ~4 of the seat pocket.
With respect to the downstream annular face seal 6~A when the gate assembly is placed in its closed expanded position, the downstream 5 annular face seal 64A remains slightly axially compressed between frusto-conical bottom portion 80A of downstream annular groove 63~ due to the expansion of the ga~e assembly. ~lowever, because fluid does not flow into downstream annular groove 63A, downstream annulaJ face seal 64A, does not wedge inwardly towards the valve chamber 22.
Fig. 1 illustrates the gate assembly in its open position in whi~h it is also fully expanded and the ports ~8 through gate 24 and segment 26 are fully aligned. As the gate assembly reaches its open ,~osition, both the up-stream and downstream annular face seals 64 and 6~A are axially compressed to initially seal ag~inst the gate ssem~ly and thPir respective annular grooves15 in a manner similar to tha~ when the gate assembly reaches its closed position.
~lowever, because fluid from the flow passage has entered the valve charnber 22 during the movernent of the gate assembly the fluid pressure on both sides of the upstream annular face seals 64 and 64! j5 equal, and the upstream annular face seals are not axially compressed any Further by wedging cgainst 20 their frusto-conical groo~e bottoms 80 and 83'. ~he valve chamber pressure also precludes any further axial compression and wedging of the downstr0am seats 64A and 64A'.
With reference to Fig. 4, wherein the gate assembly is shown in transit from the closed position to the open position and has just assumed 25 its fully collapsed condition, the frusto-conical rear portion 9~ of the up-stream face seal 64 moves away from the frusto-conical bottom portion 80 of the groove 63 and fluid contained between the inner sicles and flat portions of the upstream annular groove 63 and the face seal 64 flows past these frusto-conical surfaces 94, 80 to the outer sides of the annular groove 63 30 and fslce seal 64 thereby equalizing the fluid pressure on both sides of the upstream annular face seal 64. Once the fluid pressure on both sides o the upstream annular face seGI 64 is equalized, the seal 64 moves into a wiping relationship with the gate assembly wherein the front seal face 84 is spaced apart a small distance from the gate assembly which reduces the 35 amount of contaminants that can enter the valve chan~ber 22. In like manner, .
Case 2 ~3~3 the àownstream seal 6~A assures a similar wipiny relationship with the gate assembly wherein the sealing elements 64, o4~ do not impede or bind the movement of the gate assembly.
The invention described herein is directed to floating seats for 5 expanding gate valves which are pressure energized in a manner to minimize "drag" between the valve seats and the gate assembly and are also adapted to compensate for conditions of non-parallelism between the gate assembly sealing surfaces and the seat rings and betweon the seat rings and the bottoms of the seat pockets. At the same time, this unique seat and seal ring as-10 sembly allows the valve to effect a fluid-tight seal with the application of lesser operational torque than is generally r~quired for conventional gate valves with floating seats and particularly so for operations under high pressure ser-vice conditions. Also, its sealing effectiveness increases with increasing pressure conditions.
While the invention has been illustrated with respect to a balanced stem gate vulve, the invention could be used as well with an un-balanced gate valve. Furthermore, it is to be understood that the foregoing description of the invention has been presented for purposes of illustration andexplanation and is not intended as limiting the invention to the precise forrn 20 disclosed as changes in details of construction may be made by those skilled in the art, within the scope of the appended claims, without departing frorn the spirit of the invention.
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Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A gate valve comprising a valve body having a valve chamber therein and inlet and outlet flow passages defining a flow way communicating with the valve chamber, an expand-ing gate assembly mounted within said chamber for sliding movement transversely of the flow way between a first posi-tion wherein the valve is open and a second position where-in the valve is closed and including wedgingly engageable elements arranged for sliding relative movement trans-versely of the flow way to expand the gate assembly in the longitudinal direction of the flow way when the valve is in said open and closed positions, said body having an internal annular recess surrounding each said flow passage and being defined by an end wall and a generally cylindrical side wall opening into said chamber;
a metallic seat ring disposed loosely within each said recess, each seat ring having an axial dimension which exceeds the depth of the recess in which it is disposed to thereby extend into said chamber, each said seat ring having a planar front face disposed towards the gate assembly and a first annular groove provided in its front face in surrounding relation to the flow way, each said seat ring having an annular rear face adapted to contact with the annular end wall of the recess and being provided with a second annular groove in its rear face in surrounding relation to said flow way, each said annular groove being defined by a pair of generally parallel and cylindrical groove sides comprising an inner groove side and an outer groove side and a groove bottom joining said inner and outer groove sides, each said groove bottom having a first frustoconical bottom portion facing said inner groove side and joining said outer groove side, and a second frustoconical bottom portion facing said outer groove side and joining said inner groove side;
a first annular sealing member loosely received within the annular groove in said front face of each of the seat rings and protruding into said chamber beyond the front face of the seat ring to form a ring of sealing contact area when the gate assembly is expanded there-against;
a second annular sealing member in each of said seat rings being loosely received within the annular groove in the rear face of the seat ring whereby it is adapted to form a fluid-tight barrier and seal between the rear face of the seat ring and the valve body when the gate assembly is in its expanded condition, each said annular sealing member in each of said seat rings having front and rear seal faces joined by generally parallel inner and outer cylindrical seal sides, said rear seal face having a first frustoconical surface portion extending from said outer seal side in coaxial relation with said cylindrical seal sides and having a cone angle conforming to said first frustoconical bottom portion, said rear seal face having a second frustoconical surface portion extending from said outer seal side in coaxial relation with said cylindrical seal sides and having a cone angle conforming to said second frustoconical bottom portion, and each said annular sealing member having a length dimension between its front and rear seal faces which exceeds the depth of said annular groove in which it is received such that said front seal face extends from said annular groove beyond the front seat face when loosely seated in the groove with its gate assembly in the col-lapsed condition whereby expansion of the gate assembly to the open or closed position effects an axial compres-sion of the annular sealing member in each annular recess and fluid pressure in the flow way urges the annular seal-ing members in the upstream seat ring against said first frustoconical bottom portions of the grooves in the up-stream seat ring in a wedging movement toward the gate assembly to effect a tight seal therewith which increases with increasing fluid pressure and in the event of leakage past the upstream seat ring in the closed condition of the valve fluid pressure in the valve chamber urges the annular sealing members in the downstream seat ring against said second frustoconical bottom portions of the grooves in the downstream seat ring in a wedging movement toward the gate assembly to effect a tight seal therewith which increases with increasing fluid pressure.
a metallic seat ring disposed loosely within each said recess, each seat ring having an axial dimension which exceeds the depth of the recess in which it is disposed to thereby extend into said chamber, each said seat ring having a planar front face disposed towards the gate assembly and a first annular groove provided in its front face in surrounding relation to the flow way, each said seat ring having an annular rear face adapted to contact with the annular end wall of the recess and being provided with a second annular groove in its rear face in surrounding relation to said flow way, each said annular groove being defined by a pair of generally parallel and cylindrical groove sides comprising an inner groove side and an outer groove side and a groove bottom joining said inner and outer groove sides, each said groove bottom having a first frustoconical bottom portion facing said inner groove side and joining said outer groove side, and a second frustoconical bottom portion facing said outer groove side and joining said inner groove side;
a first annular sealing member loosely received within the annular groove in said front face of each of the seat rings and protruding into said chamber beyond the front face of the seat ring to form a ring of sealing contact area when the gate assembly is expanded there-against;
a second annular sealing member in each of said seat rings being loosely received within the annular groove in the rear face of the seat ring whereby it is adapted to form a fluid-tight barrier and seal between the rear face of the seat ring and the valve body when the gate assembly is in its expanded condition, each said annular sealing member in each of said seat rings having front and rear seal faces joined by generally parallel inner and outer cylindrical seal sides, said rear seal face having a first frustoconical surface portion extending from said outer seal side in coaxial relation with said cylindrical seal sides and having a cone angle conforming to said first frustoconical bottom portion, said rear seal face having a second frustoconical surface portion extending from said outer seal side in coaxial relation with said cylindrical seal sides and having a cone angle conforming to said second frustoconical bottom portion, and each said annular sealing member having a length dimension between its front and rear seal faces which exceeds the depth of said annular groove in which it is received such that said front seal face extends from said annular groove beyond the front seat face when loosely seated in the groove with its gate assembly in the col-lapsed condition whereby expansion of the gate assembly to the open or closed position effects an axial compres-sion of the annular sealing member in each annular recess and fluid pressure in the flow way urges the annular seal-ing members in the upstream seat ring against said first frustoconical bottom portions of the grooves in the up-stream seat ring in a wedging movement toward the gate assembly to effect a tight seal therewith which increases with increasing fluid pressure and in the event of leakage past the upstream seat ring in the closed condition of the valve fluid pressure in the valve chamber urges the annular sealing members in the downstream seat ring against said second frustoconical bottom portions of the grooves in the downstream seat ring in a wedging movement toward the gate assembly to effect a tight seal therewith which increases with increasing fluid pressure.
2. A gate valve structure as set forth in claim 1 wherein said first and second annular resilient sealing members of each said seat ring are metallic.
3. A gate valve structure as set forth in claim 1 wherein said frustoconical bottom portion has a cone angle in the range from thirty degrees to sixty degrees and is disposed coaxial with said inner and outer groove sides.
4. A gate valve structure as set forth in claim 1 wherein each said annular sealing member of each seat ring is provided on its rear face with an annular groove in coaxial relation to the seat ring and intermediate the first and second frustoconical surface portions of the rear face of the annular sealing member.
5. A gate valve structure as set forth in claim 1 wherein said first annular sealing member of each seat ring has an inner diameter which exceeds the inner diameter of the second annular sealing member of the seat ring and is disposed with its inner edge a greater distance from the flow way than the distance of the inner edge of the second annular sealing member from the flow way whereby the area of the front face of the seat ring which is exposed to fluid pressure from the flow way is greater than the annular area of the rear face of the seat ring which is exposed to fluid pressure from the flow way to thereby act to retain said seat ring in said recess and to enhance the seal between the seat ring and the end wall of the recess in the expanded condition of the gate assembly.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40420282A | 1982-08-02 | 1982-08-02 | |
| US404,202 | 1982-08-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1234380A true CA1234380A (en) | 1988-03-22 |
Family
ID=23598596
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433626A Expired CA1234380A (en) | 1982-08-02 | 1983-07-29 | Gate valve structure |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1234380A (en) |
| IT (1) | IT1169129B (en) |
| WO (1) | WO1984000593A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3006601A (en) * | 1958-03-28 | 1961-10-31 | Acf Ind Inc | Seat for gate valve |
| US3743244A (en) * | 1971-11-09 | 1973-07-03 | H Dickenson | Top and bottom gate valve for removing and replacing renewable seating elements |
| US4116419A (en) * | 1977-10-21 | 1978-09-26 | Acf Industries, Incorporated | Limited float seat construction for expanding gate valve |
| US4320890A (en) * | 1981-02-20 | 1982-03-23 | Acf Industries, Incorporated | Valve seat structure |
-
1983
- 1983-07-29 CA CA000433626A patent/CA1234380A/en not_active Expired
- 1983-08-01 WO PCT/US1983/001185 patent/WO1984000593A1/en unknown
- 1983-08-02 IT IT22398/83A patent/IT1169129B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| IT8322398A1 (en) | 1985-02-02 |
| IT8322398A0 (en) | 1983-08-02 |
| WO1984000593A1 (en) | 1984-02-16 |
| IT1169129B (en) | 1987-05-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |