GB2130345A

GB2130345A - Ball valve

Info

Publication number: GB2130345A
Application number: GB08322860A
Authority: GB
Inventors: Angel Jean-Marie Grazioli
Original assignee: Cameron Iron Works Inc
Current assignee: Cooper Industries LLC
Priority date: 1982-09-09
Filing date: 1983-08-25
Publication date: 1984-05-31
Also published as: GB8322860D0; FR2533010A1; DE3330967A1; JPS59197676A

Abstract

Sealing assemblies 22 for sealing against a ball valve 20 around the opening of the inlet and the outlet into and from the valve chamber, include a seat ring 30 having a pair of grooves 32, 38 facing the ball with a lip 36 therebetween. An anti-corrosion seal ring 34 preferably of PTFE is positioned in one of the grooves and held therein by the lip 36 being bent thereon.The seal ring 34 has an inner portion filling the groove and an outer portion extending normal to the surface of the ball and terminating in a flat sealing surface having a width less than the width of the seal ring in the groove. Springs 24 urge the assemblies 22 into engagement with the ball 20. Sealant may be introduced through passages 40. <IMAGE>

Description

SPECIFICATION Ball valve In prior ball valves the components which have needed the most improvement are the seals which engages the exterior of the ball. Such seals are preferred to have a long useful life and to withstand high pressures, rapid pressure variation, corrosion and erosion attacks, wear due to valve motion and rapid temperature changes. Prior to the present invention, the material oftheseal ring in ball valves subjecttotheabove-mentioned conditions has been a relatively hard, fiber-filled nylon. Seal rings of such material have not lasted more than a few cycles of opening and closing under such extreme conditions.

Some priorvalvestructures have suggested rolling a lip against a seal ring to retain the seal ring in its groove. (U.S. Patent No.3,765,647 and 4,135,545).

Other structures have suggested a combination of a seal ring with a sealant injected between the seat ring and the ball to aid in sealing. (U.S. Patent No. 3,752,178) The valve disclosed in theW.E. Lowrey U.S. Patent No.3,301,523 has a soft seal ring of rubber or polytetrafluoroethylene which is confined in a groove between two conical seating surfaces with the groove being largerthan the seal ring so that the ball engages the metal conical seats under high pressure. This valve is designed to operate a seal against both high and low pressure operating conditions. The W.E.

Lowrey Patent No.3,335,999 discloses another valve structure with a rubber or soft plastic seal ring which is triangular in section and is smaller than its groove so that it is not damaged during movement ofthe ball.

The R.J. Collins U.S. Patent No.2,858,847 discloses a seal in a valve with an O-ring set in a restricted groove which has a teardrop shape butthe seal would be highly prestressed and subject two accelerated wear.

The present invention relates to an improved ball valve and to an improved sealing assemblyfor sealing against the ball valve member. The sealing assembly includes a seat ring having a pair of grooves opening towardthe surfaceofthe ball, aseal ring which is resilient and corrosion resistant positioned in one of the grooves and held therein by the lip between the two grooves being bent into tight engagement with said seal ring, the seal ring having a generallytear drop shape with its enlarged portion within the groove, and resilient means biasing the seat ring in a direction to ensure the seal ring engages the exterior ofthe ball valve member. Sealant injection means is provided to inject sealant into the second groove.

An object ofthe present invention is to provide an improved ball valve having a long life under high pressure and with corrosive and erosive fluids through the valve.

Another object is to provide an improved sealing assemblyfor a ball valve which uses a soft seal ring that is not extruded even under rapid pressure fluctuations.

Afurther object is to provide an improved ball valve sealing assembly having low wear of the seal ring and also a structure which is relatively inexpensive to manufacture.

These and other objects and advantages ofthe present invention are hereinafter set forth and ex plainedwith respect to the drawings wherein: FIGURE 1 isasectionalviewoftheimproved ball valve of the present invention; FIGURE 2 is a partial sectional view of the improved sealing assembly ofthe present invention; FIGURE 3 is a partial sectional view to illustrate the machining of the grooves in the seat ring; FIGURE 4 is a partial sectional of the step of rolling of the center lip onto the seal ring; FIGURE 5 is a partial sectional view of the completed seat ring and illustrating the sealing injection passage into the second groove and the finishing of the machining of the seat ring.

The improved ball valve 10 of the present invention includes body 12 havingvalvechamber14with passages 16 and 18 extending into chamber 14, and ball or valve member 20 positioned in chamber 14to control flowthrough valve 10. Sealing assemblies 22 are positioned to seal against ball 20 around the opening of each of passages 16 and 18 into valve chamber 14. Springs 24 are positioned between body shoulders 26 and shoulders 28 on seat rings 30 to urge sealing assemblies 22 toward ball 20.

Sealing assembly 22 includes seat ring 30 having groove 32 facing ball 20 with seal ring 34 held in groove 32 by lip 36 which is bent over as hereinafter described into the position shown in FIGURE 2.

Second groove 38 in seat ring 30 also faces ball 20 and passages 40 comunicate therewith to conduct sealant from injection port 42 in body 12 to groove 38. This structure retains seal ring 34 in groove 32 with its outer portion extending normal to the exteriorof ball and having narrow sealing surface 44 and an enlarged inner portion filling groove 32.

It is believed that the improved seal life which has been achieved with this structure results from the distribution of sealing forces throughoutthe enlarged inner portion againstthe interior ofthe groove 32. This reduces stress in the outer portion of seal ring 34 to allow it to have much greater life. The preferred ratio of the width of the narrow sealing surface of seal ring 34to its width in groove 32 is one to two and one-half.

Also the retention of seal ring 34 by lip 36 prevents seal ring 34from blowing out of groove 32 by rapid pressure changes and provides adequate close support so that seal ring 34 is not extruded. Also seal ring 34 is inserted in groove 32 in a free state so there is not any static stress from assembly which allows seal ring 34to be exposed to higher stresses without reducing its effective life. The preferred material for seal ring 34 is virgin polytetrafluoroethylene.

Seat ring 30 is prepared as shown in FIGURES 3,4 and 5. Seat ring 30 is mounted on a suitable fixture 46 and tools 48 and 50 are used to form grooves 32 and 38, respectively, with lip 36 therebetween. With tear drop shaped seal ring 34 positioned in groove 32, roller52 is moved against lip 36to turn it into engagement with seal ring 34 as shown in FIGURES.

The outer portion of seal ring 34 is trimmed to provide the narrowsealing surface 44 of seal ring 34 which is to engage the outer surface of ball valve member 20.

Also, the interior of seat ring 30 beyond groove 38 is machined as shown at 54 in FIGURE 5 and passages 40 aresuitablyformed in seat ring 30.

The improved sealing assembly of the present invention has achieved a very substantial improved useful life when exposed to extreme conditions such as mentioned above as compared to prior sealing assemblies.

Claims

1. A ball valve having a body with a valve chamber therein and an inlet and an outlet communicating with said chamber, a ball valve member in said chamber, and a pair of sealing assemblies for sealing against the ball, each of said sealing assemblies including a seat ring having a groove facing said ball valve member and a lip beside said groove, a sealing ring positioned in said groove and retained therein by said lip and characterized by said seal ring having a narrow sealing surface for engaging said ball valve member and an enlarged portion filling said groove.

2. Aball valve according to claim 1 wherein the portion of said seal ring terminating in said sealing surface is normal to the exterior surface of said ball valve member.

3. A ball valve according to claim 1 or2wherein the material of said seal ring is resistant to corrosive fluids.

4. A ball valve according to claim 3 wherein the seal ring material is a polytetrafluoroethylene material.

5. A ball valve according to any of the preceding claims including spring means biasing said seat ring toward said ball valve member.

6. A ball valve according to claim 2 wherein said groove is substantially normal to the surface of said ball valve member so thatforces on said seal ring are transmitted uniformly to the portion of the seal ring within said groove.

7. A balivalve according to anyofthe preceding claims including means for introducing a sealant between said seat ring and said ball valve member.

8. A ball valve according to claim 1 wherein the width of said enlarged portion of said seal ring is approximately two and one-halftimesthewidth of said narrow sealing surface.

9. A ball valve substantially as hereinbefore described with reference to and as shown in the accompanying drawings.