BACKGROUND Field

[0001] This present disclosure is in the field of slip seals used in plug valves found in oil and gas applications.

[0002] A plug valve has two slips which are pressed against the inside diameter bore of the valve body by the downward motion of the wedge-shaped plug during valve closing (see FIG. 1). This downward motion causes the slip seals bonded to the slips to move outward toward the valve body, thereby producing a seal that holds the pressure of the medium flowing into and through the valve body.

[0003] Prior art slip seal profiles have a single point of contact between the slip seal and the valve body (see e.g. FIG. 2). This single point of contact is flat, located in the center of the seal profile, runs the entire length of the slip seal, and provides a relatively wide contact area. Sometimes this contact area does not provide enough resistance to the working pressure of the medium and the slip seal leaks.

SUMMARY

[0004] In general, disclosed herein are methods and apparatuses for double slip seal profiles for plug valves. In some embodiments, the apparatus includes a slip seal providing two points of contact or surface areas between the slip seal and the valve body. This double seal profile provides two barriers to withstand the working pressure of the medium acting against the slip when the plug valve is in the closed position.

[0005] Each of the two points of contact is rounded and run the entire length of the seal seat. The first point of contact is located toward an inside peripheral edge of the slip seal seat. The second point of contact is located toward the outside peripheral edge of the slip seal seat and acts as a back-up seal to the first. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] So that the manner in which the above recited features can be understood in detail, a more particular description may be had by reference to embodiments, some of which are illustrated in the appended drawings, wherein like reference numerals denote like elements. It is to be noted, however, that the appended drawings illustrate various embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0006] FIG. 1 is a cross-section view of a prior art plug valve.

[0007] FIG. 2 is a profile view of a prior art slip seal used in the plug valve of FIG. 1.

[0008] FIG. 3 is a top view of an embodiment of a double seal profile slip seal when bonded to a slip of a plug valve.

[0009] FIG. 4 is a cross-section view of the slip and slip seal taken along section line 4-4 of FIG. 3.

[0010] FIG. 5 is a cross-section view of the slip and slip seal taken along section line 5-5 of FIG. 3.

[0011] FIG. 6 is an enlarged profile view of the seal taken along section 6 of FIG. 3.

Elements and Numbering Used in the Drawings and Detailed Description

[0012] 10 Slip seal

[0013] 11 Face surface

[0014] 13 First contact point or area

[0015] 15 Vertical centerline

[0016] 17 Second contact point or area

[0017] 19 Recessed (valley) portions of face surface

[0018] 20 Slip

[0019] 21 Slip face

[0020] 23 Inner peripheral edge of slip seal seat

[0021] 25 Slip seal seat

[0022] 27 Outer peripheral edge of slip seal seat DETAILED DESCRIPTION

[0001] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0002] In the specification and appended claims: the terms "connect", "connection", "connected", "in connection with", and "connecting" are used to mean "in direct connection with" or "in connection with via one or more elements"; and the term "set" is used to mean "one element" or "more than one element". Further, the terms "couple", "coupling", "coupled", "coupled together", and "coupled with" are used to mean "directly coupled together" or "coupled together via one or more elements". As used herein, the terms "up" and "down", "upper" and "lower", "upwardly" and downwardly", "upstream" and "downstream"; "above" and "below"; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the disclosure.

[0003] Although the preceding description has been described herein with reference to particular means, materials and embodiments, it is not intended to be limited to the particulars disclosed herein; rather, it extends to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims.

[0023] The embodiment of a double profile slip seal 10 for use in a slip 20 of a plug valve is shown in FIGS. 3-6. The slip seal's double profile provides two barriers to withstand the working pressure of the medium acting against the slip when the plug valve is in the closed position.

[0024] The slip seal 10 has a first and a second contact point or area 13, 17 spaced apart from one another on opposite sides of the seal's centerline 15. The contact areas 13, 17 protrude outwardly from the slip seal seat 25 and, when seated in the seat 25 in a non-sealing position, protrude above the slip face 21. The contact areas 13, 17 are rounded in shape, giving a sinusoidal wave shape to the seal face 11 , with portions 19 of the face 11 lying below the slip face 21. [0025] First contact area 13 is located toward the inside peripheral edge 23 of the slip seal seat 25. This first contact area 13 provides the primary seal. The second contact area 17 is located toward the outside peripheral edge 27 of the slip seal 25. This second area of contact 17 acts as a back-up seal to the first contact area 13.

[0026] When in an assembled state, the double profile slip seal 10 is bonded to the seat 25 of the slip. Downward motion of a wedge plug body like that shown in FIG. 1 causes the slips 20 to move outward toward the valve body, thereby producing a double barrier seal that holds the pressure of the medium flowing into and through the valve body.