WO2011066442A2

WO2011066442A2 - Polymer seat for ball valves

Info

Publication number: WO2011066442A2
Application number: PCT/US2010/058079
Authority: WO
Inventors: Robert A. Frenzel; Gregory L. Filipowicz
Original assignee: Bray International, Inc.
Priority date: 2009-11-25
Filing date: 2010-11-24
Publication date: 2011-06-03
Also published as: WO2011066442A3

Abstract

A polymer seat for insertion into a seat pocket of a ball valve is disclosed. The annular piece polymer seat has an inner diameter, an outer diameter, a front face and a back face. The outer diameter has a chamfer thinning the annular piece toward the back face. The front face has a chamfered edge to support a ball of the ball valve. And, the back face defines a concave surface and/or a surface with a radius.

Description

APPLICATION FOR PATENT

TITLE: POLYMER SEAT FOR BALL VALVES

INVENTOR(S):

1 . Frenzel, Robert

Citizenship: US

Residence: Waller, TX, USA

2. Filipowicz, Gregory L.

Citizenship: US

Residence: Houston, TX, USA

SPECIFICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of US Provisional Application No. 61/264,559 filed November 25, 2009.

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

[0003] Not Applicable.

REFERENCE TO A "SEQUENCE LISTING", A TABLE, OR

A COMPUTER PROGRAM

[0004] Not Applicable.

BACKGROUND

[0005] The present status of technology in polymer seats for ball valves utilizes a simple ring of polymer material (TFE, PEEK, reinforced TFE, etc) that is captured between the valve body, end piece and ball. Two such rings are required for sealing in both directions but the mechanism of sealing is the same for both sides. The seal functions as a crush type seal with the initial seal preload applied by the end piece(s). This configuration results in high torque at low pressures where the same preload is depended upon for both low and high pressure sealing. The preload must be sufficient to seal at high pressures and the low pressure performance must suffer the same high preload torque as at high pressure.

[0006] Referring to Fig.1 , a valve seat in a floating ball valve must accomplish multiple functions. The first and most obvious is to provide a seal between the ball and body which will block the flow of product through the valve. Several secondary, though no less important, functions are needed for successful operation. The seat must also prevent the ball from moving (floating) off of the stem centerline by too large an amount otherwise torque will become excessive. The seat must also provide for centering on the ball sufficient to provide even loading of the seal so that no local leakage occurs. This is important since sealability is directly related to contact loading against the seat. The seat should then be allowed to float some small amount to best affect an even seal. A large preload is applied to the seat and ball by the end piece(s) when the valve is assembled. This preload must be large enough to provide a seal at the highest rated pressure of the valve. The preload is stored in the elastic deformation of the metal parts at the time of assembly. The torque is correspondingly high at all operating pressures.

[0007] Some designs accomplish the low pressure preload by using auxiliary springs, gaskets or other components to provide the preload.

SUMMARY

[0008] There is a need for a seal configuration that has torque characteristics proportional to the service pressure without depending upon the pressure or additional components to energize the seal. The seal should adapt to the high pressure rather than requiring the pressure to function.

[0009] The principle objectives follow:

1 . The existing body should be used unmodified. The seat should be a drop-in retrofit to an existing polymer seat without additional components.

2. The design should function equally well at low as well as high pressure.

3. The operating torque should be proportionally lower at low pressures.

4. The seat should maintain control valve leakage class VI or better throughout the useful life. [0010] A polymer based ball valve seat has been developed that stores energy by torsional deflection of the seat section rather than by compressive loading. The energy storage can be characterized by a radius or chamfer added to the back face of the seat against the seat pocket and by a clearance taper on the outside diameter of the seat. These features result in a polymer seat that has low operating torque and superior sealing capability at low pressure.

[0011] To provide a low pressure preload, elastic energy must be stored somewhere. Typical polymer materials are not well known for their resiliency so another method to store elastic energy within the seal must be utilized. Yet, purely compressive preload dissipates quickly as the material "creeps" only a short distance.

[0012] The idea occurred to attempt to store energy in a unique manner. Upon reflection, such a manner is not unlike a Belleville washer. With this idea in mind it is was essential to determine whether it was possible to store energy in this manner using the materials typically found in a polymer seat while also characterizing the stored energy as a function of the operating pressure. Accordingly, a functional design for polymer seat operating within a valve body was required. Such a polymer seat design must be able to respond and adapt to the applied pressure, providing increasing resistance as the pressure increased, whilst distributing the load.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0013]

Fig. 1 is a sectional perspective view of a Prior Art ball valve.

Fig. 2 is a sectional view of one embodiment of a polymer seat mounted in the seat pocket of a ball valve shown in an unloaded position.

Fig. 3 is a sectional view of the embodiment of Fig. 2 shown in a pre-loaded position.

Fig. 4 is a sectional view of the embodiment of Fig. 2 and Fig. 3 shown in a high-pressure load position.

Fig. 5 is a cross-sectional view of one embodiment of a polymer seat. Fig. 6 is a detail break-away view taken from Fig. 5.

Fig. 7 is a perspective sectional view from the back face of an embodiment of a polymer seat

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

[0014] Referring to Figs. 2-4, a basic embodiment of the polymer seat 20 is represented. The polymer seat 20 is implemented into a floating ball valve 10. The floating ball valve has a stem 1 1, a valve body 12, and a ball 18. The valve body 12 has a seat pocket 14 and a flow chamber 16.

[0015] The polymer seat 20 is an annular piece 22 (see Figs. 5-7) and may be made by machining. The polymer seat 20 may, for example, be made of PEEK

(Polyetheretherketone), UHMPWE (Ultra High Molecular Weight Polyethylene), nylon and nylon family, or a high density filled material (polytetrafluorethylene) sold under the brand name "TEFLON" (e.g. such as that sold under the brand name "TEKFIL"). The polymer seat 20 is for insertion into the seat pocket 14 of the floating ball valve 10. The annular piece 22 has an inner diameter 24, an outer diameter 26, a front face 28 and a back face 30.

[0016] The outer diameter 26 has a chamfer 32, such as for example, an angular relief 34. The chamfer 32 is made such that the annular piece 22 becomes incrementally thinner as the chamfer 32 runs toward the back face 30 along the outer diameter 26. The angular relief 34 is at an angle within a range of about 0.5 to 6 degrees with respect to a plane perpendicular to the front face (when the polymer seat 20 is free from any load).

[0017] The front face 28 has a chamfered edge 36 to support a ball 18 of the ball valve 10.

[0018] The back face 30 defines a concave surface 38. The concave surface is at an angle within a range of about 0.5 to 6 degrees with respect to a plane parallel to the front face (or essentially equivalently, depending upon the design of a particular application, a radius within a range of about 30 to 60 millimeters) (when the polymer seat 20 is free from any load). The concave surface 38 may be conical, spherical or toroidal. A secondary inset surface 42 is preferably formed or bored in the concave surface 38. The secondary inset surface 42 has a smaller radius than the concave surface 38 and terminates at the inner diameter.

[0019] The polymer seat 20 is installed in the seat pocket 14 in a first position shown in Fig. 2. With the polymer seat 20 installed without the ball 18, the polymer seat 20 sits unloaded in the seat pocket 14. The point of contact 40 between the back face 30 of the polymer seat 20 and a first surface 14a of the seat pocket 14 is proximate or near the outer diameter 26. The chamfer 32 on the outer diameter 26 is offset or free of the second surface (inside diameter) 14b of the seat pocket 14. The concave surface 38 has a clearance from the first surface 14a of the seat pocket 14.

[0020] Referring to Fig. 3 in a second position, loading the polymer seat 14 with the ball 1 8 (represented by arrow 40), e.g. at chamfered edge 36 on front face 28, causes elastic energy to be stored in the seat 14 due to the rotational moment created (represented by arrow 42). The rotation of the polymer seat 14section also moves the support point 40 on the back face 30 inward toward the ball 18, increasing the resistance to seat compression (and the clearance of the concave surface 38 from the first surface 14a of the seat pocket 14 is reduced). The offset between the chamfer 32 on the outer diameter 26 and the second surface 14b of the seat pocket 14 is reduced.

[0021] By way of reference to Fig. 4 in a third position, at higher pressures

(represented by arrow 44) from the ball 18 and operating conditions, the polymer seat 20 provides increasing resistance as the rotation of the seat 20 section brings the seat pocket 14 contact line inward into alignment with the contact line of the ball 18. The clearance of the concave surface 38 from the first surface 14a of the seat pocket 14 is negligible. The point of contact between the back face 30 and the first surface 14a of the seat pocket 14 is distal from the outer diameter 26 as compared to the first position. The outer diameter 26 is supported and opposed by the second surface 14b of the seat pocket 14. The offset between the chamfer 32 on the outer diameter 26 and the second surface 14b is negligible. [0022] Functionally, the objectives are achieved by placing a load on the inside edge and supporting the outside edge. Beyond metal seat designing, two additional features were incorporated in the polymer seat 20 to characterize the response of the seat. The first is to place a radius on the back face 30 of the seat 20 so that as the seat deflects, the support point 40 moves inward, increasing the stiffness, hence load on the ball 18. The second is to place an angular relief 34 on the outside diameter 26 of the seat 20 so that it is free to deflect until the desired point is reached, then the seat pocket's 14 outer diameter or second surface 14b supports the seat 20 from deflecting any further. The actual dimensions of the chamfer or radius 38 and angular relief 34 work together as a whole to gradually increase the ball load with deflection and pressure then suddenly increases the seat resistance at full pressure to support the ball 18.

[0023] Referring back to Fig. 3, the resistance to rotation is low during this portion of the rotation, providing a relatively low preload. This stored energy provides the preload necessary for a low pressure seal while the low preload force maintains a low torque. The result is a reliable low pressure seal and proportionally low torque at low pressures.

[0024] Referring back to Fig. 4, the polymer seat 20 is in full contact with the seat pocket 14 inner diameter and is fully supported radially. No further rotation is possible and the ball 18 is fully supported at high pressure.

Claims

1 . An apparatus for insertion into a seat pocket of a ball valve, comprising: a polymer seat, wherein the polymer seat comprises an annular piece; wherein the annular piece has an inner diameter, an outer diameter, a front face and a back face; wherein the outer diameter has a chamfer thinning the annular piece toward the back face; and wherein the back face defines a concave surface.

2. The apparatus according to claim 1 , wherein when the ball is not in contact with the polymer seat, the polymer seat is in a first position wherein: a point of contact between the back face and a first surface of the seat pocket is proximate the outer diameter, the concave surface has a clearance from the first surface of the seat pocket, and the chamfer on the outer diameter is offset from a second surface of the seat pocket; and wherein when the ball is in contact with the front face, the polymer seat is in a second position wherein: the clearance of the concave surface from the first surface of the seat pocket is reduced, and the offset between the chamfer on the outer diameter and the second surface of the seat pocket is reduced.

3. The apparatus according to claim 2, wherein when the ball is in high pressure, fully loaded contact with the chamfered edge on the front face, the polymer seat is in a third position wherein: the clearance of the concave surface from the first surface of the seat pocket is negligible, the point of contact between the back face and the first surface of the seat pocket is distal from the outer diameter as compared to the first position, and the outer diameter is supported and opposed by the second surface of the seat pocket whilst the offset between the chamfer on the outer diameter and the second surface of the seat pocket is negligible.

4. The apparatus according to claim 1 , wherein the chamfer on the outer diameter is an angular relief.

5. The apparatus according to claim 4, wherein the angular relief is at an angle within a range of about 0.5 to 6 degrees with respect to a plane perpendicular to the front face.

6. The apparatus according to claim 4, wherein the concave surface is at an angle within a range of about 0.5 to 6 degrees with respect to a plane parallel to the front face.

7. The apparatus according to claim 1 , wherein the concave surface is a conical

surface.

8. The apparatus according to claim 1 , wherein the concave surface is a spherical surface.

9. The apparatus according to claim 1 , wherein the concave surface is a toroidal surface.

10. The apparatus according to claim 1 , wherein the concave surface has a secondary inset surface, the secondary inset surface having a smaller radius than the concave surface and terminating at the inner diameter.

An apparatus for insertion into a seat pocket of a ball valve, comprising: a polymer seat for insertion into the seat pocket; wherein the polymer seat comprises an annular piece; wherein the annular piece has an inner diameter, an outer diameter, a front face and a back face; wherein the outer diameter has a chamfer thinning the annular piece toward the back face; wherein the front face has a chamfered edge to support a ball of the ball valve; wherein the back face defines a concave surface; wherein when the ball is not in contact with the polymer seat, the polymer seat is in a first position wherein: a point of contact between the back face and a first surface of the seat pocket is proximate the outer diameter, the concave surface has a clearance from the first surface of the seat pocket, and the chamfer on the outer diameter is offset from a second surface of the seat pocket; and wherein when the ball is in contact with the chamfered edge on the front face, the polymer seat is in a second position wherein: the clearance of the concave surface from the first surface of the seat pocket is reduced, and the offset between the chamfer on the outer diameter and the second surface of the seat pocket is reduced.

12. The apparatus according to claim 1 1 , wherein when the ball is in high pressure, fully loaded contact with the chamfered edge on the front face, the polymer seat is in a third position wherein: the clearance of the concave surface from the first surface of the seat pocket is negligible, the point of contact between the back face and the first surface of the seat pocket is distal from the outer diameter as compared to the first position, and the outer diameter is supported and opposed by the second surface of the seat pocket whilst the offset between the chamfer on the outer diameter and the second surface of the seat pocket is negligible.

3. An apparatus for insertion into a seat pocket of a ball valve, comprising: a polymer seat for insertion into the seat pocket; wherein the polymer seat comprises an annular piece; wherein the annular piece has an inner diameter, an outer diameter, a front face and a back face; wherein the outer diameter has a chamfer thinning the annular piece toward the back face; wherein the chamfer on the outer diameter is an angular relief; wherein the angular relief is at an angle within a range of about 0.5 to 6 degrees with respect to a plane perpendicular to the front face; wherein the front face has a chamfered edge to support a ball of the ball valve; wherein the back face defines a concave surface; wherein the concave surface is at an angle within a range of about 0.5 to 6 degrees with respect to a plane parallel to the front face; wherein the concave surface has a secondary inset surface, the secondary inset surface having a smaller radius than the concave surface and terminating at the inner diameter; wherein when the ball is not in contact with the polymer seat, the polymer seat is in a first position wherein: a point of contact between the back face and a first surface of the seat pocket is proximate the outer diameter, the concave surface has a clearance from the first surface of the seat pocket, and the chamfer on the outer diameter is offset from a second surface of the seat pocket; and wherein when the ball is in contact with the chamfered edge on the front face, the polymer seat is in a second position wherein: the clearance of the concave surface from the first surface of the seat pocket is reduced, and the offset between the chamfer on the outer diameter and the second surface of the seat pocket is reduced.

14. The apparatus according to claim 13, wherein when the ball is in high pressure, fully loaded contact with the chamfered edge on the front face, the polymer seat is in a third position wherein: the clearance of the concave surface from the first surface of the seat pocket is negligible, the point of contact between the back face and the first surface of the seat pocket is distal from the outer diameter as compared to the first position, and the outer diameter is supported and opposed by the second surface of the seat pocket whilst the offset between the chamfer on the outer diameter and the second surface of the seat pocket is negligible.