DESC:FIELD OF THE INVENTION

The present invention relates generally to high performance butterfly valves, and more particularly, the present invention emphasizes more on improved triple offset valve sealing design.

BACKGROUND OF THE INVENTION

A Butterfly valve (BFV) is a valve which can be used for isolating or regulating flow. A valve consists of a rotating circular plate or a pair of hinged semi-circular plates, attached to transverse spindle and mounted in a pipe in order to regulate or isolate flow. A Butterfly valve works under the principle of quarter-turn valves. The valve may be opened incrementally to throttle the flow. There are different types of butterfly valves, each adapted for different pressure, temperature and usage. The zero-offset butterfly valve, which uses flexibility of a rubber, has the lowest pressure rating and temperature. The high performance double offset butterfly valve, used in higher pressure & temperature rating with improved seating arrangement by means of two offsets in design. Since double offset design has get a limitation towards very high pressure and temperature application, instead Triple offset design is used to overcome this high-end application.

Triple offset design prevents galling and scratches between the metal seat and the metal disc due to its unique design. The triple offset valve is generally used in applications which require bi-directional tight shut-off in oil and gas, LNG/NPG terminal and tanks, chemical factories and ship building.

In conventional sealing at non-driving end of a shaft of the triple offset valve, a bearing along with gasket ensures the sealing in static condition. Apart from poor sealing in static and dynamic condition, the conventional design requires precise machining in bearing, closer tolerances for gaskets. This increases bearing width which reduces body shell thickness (6). Further, the bottom cover plate of the triple offset valve needs to be machined for secondary sealing.

Figure 1 shows conventional arrangement for shaft (1) sealing of the triple offset valve to avoid leakage in static as well as in dynamic condition. In this, sealing is achieved by means of gasket (2) which are provided in a bearing (3) with groove. This increases the bearing (3) thickness. A spacer (4) is also provided to lock the position of the bearing (3). Further, precise machining and close dimensional tolerances leads to increase in manufacturing cost of the triple offset valve of the prior art. Apart from manufacturing cost, this arrangement does not ensure positive sealing in dynamic condition after prolonged use. Further secondary sealing is introduced to ensure leak proof design. The gasket (8) is provided on non-drive end cover (5).

Accordingly, there exists a need to provide shaft sealing mechanism for triple offset valve which overcomes above mentioned problems.

Objects of the invention

An object of the present invention is to provide a positive and consistent sealing for a triple offset valve in static as well as in dynamic condition.

Another object of the present invention is to provide ease of assembly, reduction in manufacturing cost of a triple offset valve.

Summary of the invention

Accordingly, the present invention provides a sealing mechanism (100) for a shaft (20) of a triple offset valve. The sealing mechanism (100) comprises a hollow cylindrical body (10) having the shaft (20) configured therein. Further, the sealing mechanism (100) includes a cover member (12) configured at bottom portion of the hollow cylindrical body (10) and a thrust pad (22) supporting the shaft (20) at the bottom portion. The thrust pad (22) gives support as well as smooth guiding surface to the shaft. Moreover, the sealing mechanism (100) includes a bearing (30) configured along the shaft (20) for providing support to the shaft (20) and a packing (40) configured below the bearing (30) for sealing through the shaft (20). Also, the sealing mechanism includes a wave spring (50) configured below the packing (40) extending up to the cover member (12). The wave spring (50) ensures a leak proof design in static and dynamic condition even in prolonged service as continuous positive preload is applied on the sealing of the shaft (20).

Brief description of the drawings

Figure 1 shows a triple offset valve, of the prior art; and

Figure 2 shows a triple offset valve, in accordance with the present invention.

Detailed description of the present invention

The foregoing objects of the present invention are accomplished. The problems as well as shortcomings associated with the prior art, techniques and approaches has been overcome. The present invention is described below in the preferred embodiments.

Accordingly, the present invention provides a mechanism for sealing a shaft of a triple offset valve at non-driving end. The construction of the triple offset valve of the present invention provides positive and consistent sealing thereof. Further, the triple offset valves provide ease of assembly and reduction in manufacturing cost.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring now to figure 2, there is a sealing mechanism (100) shown for a shaft of a triple offset valve at non-driving end (hereinafter, “the mechanism (100)”), in accordance with the present invention. The mechanism (100) comprises a hollow cylindrical body (10) having the shaft (20) configured therein. The mechanism (100) further comprises a cover member (12) configured at the bottom portion of the hollow cylindrical body (10).

The shaft (20) is supported with a thrust pad (22) at the bottom portion. The thrust pad (22) gives support as well as smooth guiding surface to shaft. In a preferred embodiment, the thrust pad (22) is made of up of ASTM A 479 GR. SS 316 + Nitriding.

The mechanism (100) further more comprises a bearing (30) configured along the shaft (20) for providing support to the shaft (20).

The bearing (30) along with a packing (40) is provided for high temperature application. Here, high temperature application constitutes to steam, exhaust gases, oil, gas application and the like. The bearing (30) along with the special packing (40) provides sealing through the shaft (20) of the triple offset valve. The packing (40) is made of up of graphoil (graphited).

The mechanism (100) furthermore includes a wave spring (50) configured below the packing (40) and extends up to the cover member (12). The wave spring (50) is made up ASTM A 693 Gr. 17-7PH and ensures a leak proof design in static and dynamic condition even in prolonged service as continuous positive preload is applied on the sealing of a triple offset valve (100). Apart from leak proof design this arrangement helps to reduce machining cost and ease of assembly.

Advantages of the invention

1. The triple offset valve (100) with addition of wave spring ensures positive sealing with adjustable stiffness/ compression to provide proper sealing in prolonged service.

2. The triple offset valve (100) also helps to reduce machining cost, easy to assemble and consistent body shell thickness is maintained.

3. Commercially available bearing can be used at non-driving end and there will not be any complications like seal tear off during shaft assembly.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

,CLAIMS:We Claim:

1. A sealing mechanism (100) for a shaft (20) of a triple offset valve, the sealing mechanism (100) comprising:
a hollow cylindrical body (10) having the shaft (20) configured therein;
a cover member (12) configured at bottom portion of the hollow cylindrical body (10);
a thrust pad (22) supporting the shaft (20) at the bottom portion, wherein the thrust pad gives support as well as smooth guiding surface to the shaft;
a bearing (30) configured along the shaft (20) for providing support to the shaft (20);
a packing (40) configured below the bearing (30) for sealing through shaft (20); and
a wave spring (50) configured below the packing (40) extending up to the cover member (12), wherein the wave spring (50) ensures a leak proof design in static and dynamic condition even in prolonged service as continuous positive preload is applied on the sealing of the shaft (20).

2. The sealing mechanism (100) as claimed in claim 1, wherein the packing is made of graphoil (graphited).

3. The sealing mechanism (100) as claimed in claim 1, wherein the thrust pad is made of ASTM A 479 GR. SS 316 + Nitriding.

4. The sealing mechanism (100) as claimed in claim 1, wherein the wave spring (50) is made up ASTM A 693 Gr. 17-7PH.