BACKGROUND

Field

The present disclosure relates to plug bodies used in double block plug valves and diverter plug valves found in pipeline applications.

Description of the Related Art

A plug valve includes a tapered (wedge-shaped) central or main plug body that moves the valve's seals (permanently bonded into slips) to and from the valve body (see e.g. FIG. 1).

In the open position, the seals are completely out of the product flow. Turning the operator hand wheel clockwise rotates the plug body 90° to block flow. During rotation, clearance is maintained between the slip seals and the inside diameter bore of the valve body. When the operator hand wheel is turned further clockwise, the wedge-shaped plug body begins to lower, forcing the slips and their seals outward against the inside diameter bore of the valve body.

This produces a seal that holds the pressure of the medium flowing into and through the valve body.

The valve's operator includes a stem or upper trunnion that, unlike the main plug body, is exposed to the environment. Sealing around the upper trunnion is critical to ensure product does not leak out into the environment. Additionally, the upper trunnion experiences the torque load required to open and close the valve during operation. Therefore, some plug valve customers require the upper trunnion to be made from a different material than the main plug body. For example, the upper trunnion can be specified to be made from a stronger and more corrosion resistant material than the rest of the plug body.

The three main ways to meet this different material requirement are: (1 ) cast the upper trunnion and main plug body as a one-piece casting using the stronger, more corrosion resistant material specified for the upper trunnion (see e.g. FIG. 2); (2) cast the upper trunnion separately using the stronger, corrosion resistant material and then cast the main plug body around the upper trunnion using a different material; or (3) cast each part separately and attach the upper trunnion to the main plug body with a pin. The one-piece casting option makes the plug more expensive because the main plug body is being cast using the stronger, more corrosion resistant material. The cast-around option is difficult to do and results in a relatively high scrap rate due to casting defects. The pinned option introduces a potential failure mode during valve operation.

SUMMARY

In general, disclosed herein are methods, systems, and apparatuses for a plug that includes an attachable upper trunnion that is assembled to the main plug body using fasteners and a male-female dovetail fit. The tensile and compressive loading experienced by the main plug body during its linear motion, and the torsional loading experienced during its 90° rotation, is supported by the fasteners and the dovetail fit.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is an isometric view of the main valve sealing components of the plug valve.

Figure 2 is an isometric view of a prior art integral upper trunnion plug. Alternatively, the upper trunnion can be cast separately using a stronger, corrosion resistant material and then the main plug body can be cast around the upper trunnion using a different material. Figure 3 is an exploded assembly view of a plug with an attachable upper trunnion that is assembled to the main plug body using fasteners and a male-female dovetail fit. The plug valve in which the plug is used includes other components (see e.g. Cameron International Corporation GENERAL VALVE® TWIN SEAL™ valves) but those components are not the focus of this disclosure.

Figure 4 is an isometric view of the upper trunnion and main plug body of Figure. 3 when assembled together.

Figure 5 is a top view of the assembled upper trunnion and main plug body of Figure

4.

Figure 6 is a front view of the upper trunnion of Figure 3.

Figure 7 is a front view of the main plug body of Figure 3.

Elements and Numbering Used in the Drawings and Detailed Description

10 Plug for use in a plug valve

20 Main plug body

21 Upper end

23 Channel (sized to tightly receive flange 33)

25 Sidewall

27 Male dovetail

29 Fastener holes

30 Stem or upper trunnion

31 Lower end

33 Flange (with fastener holes complementary to 29)

35 Sidewall

37 Female dovetail

39 Fasteners (preferably machine screws) DETAILED DESCRIPTION

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.

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 described some embodiments of the disclosure.

Although the preceding description has been described herein with reference to particular means, materials and embodiment, 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.

Referring to Figures 3-7, a plug 10 includes a tapered (wedge-shaped) central or main plug body 20 and a stem or upper trunnion 30. The upper trunnion 30 is attachable to, and detachable from, the main plug body 20. Because the upper trunnion 30 is attachable to the main plug body 20, each component 20, 30 can be made separately from the other and then assembled together. The main plug body 20 features a male dovetail 27 located in a channel 23 defined by two opposing sidewalls 25 at the upper end 21 of the plug 20. The upper trunnion 30 features a flange 33 having a female dovetail 37 at the lower end 31 of the trunnion 30. The flange 33 and its dovetail 37 are received by the channel 23 and its dovetail 27.

Fasteners 39 then secure the flange 33 in the channel 23 (which provides fastening holes

29 for the fasteners 39). In this assembled state, the tensile and compressive loading experienced by the main plug body 20 during its linear motion, and the torsional loading experienced during its 90° rotation, is supported by the fasteners 39 and the dovetail fit 27, 37.

The main plug body 20 and upper trunnion 30 can be made from the same material or, more preferably, from different materials. For example, the main plug body 20 is a first material and the upper trunnion 30 is a second different material that has higher strength, higher corrosion resistance, or both high strength and corrosion resistance than the first material.

The description above and illustrated in the drawing figures provide examples of the system and method. The following claims define the system and method and cover the full range of equivalents to which the recited elements of the claims are entitled.