JP2001317640A - Seat ring for butterfly valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seat ring for a bitterfly valve with a long service life, low maintenance cost, easy valve opening and closing operation, not influenced by thermal expansion, easy production of the seat ring, and easy adjustment in assembling. SOLUTION: In the butterfly valve in which a valve seat and a valve shaft are eccentric each other, the seat ring whose inner circumferential valve seat surface is formed in a tapered shape having such an angle that the contact part with a valve element forms a tangential line is fixed to a valve body with a seat ring member, a gasket is interposed between the valve body and the seat ring and the seat ring pressing member, a first gap is formed between the outer circumferential end of the seat ring and the seat ring pressing member, a second gap is formed between the side surface of the seat ring and the valve body and the seat ring pressing member, a stepped part is formed on the side surface of he sear ring, the thickness of the inside than the stepped part is increased, a gasket is placed on the outside of the stepped part, and the protrusion inward of the gasket is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a seat ring for a butterfly valve.

[0002]

2. Description of the Related Art Conventionally, there has been known a butterfly valve in which a cylindrical flow path is provided at the center of a valve body and the flow path is opened and closed by a disc-shaped valve body. It is used for In such a butterfly valve, a seat ring, which is an elastic sealing material, is interposed between the inner peripheral surface of the flow path of the valve body and the disc-shaped valve body, and the flow path is opened and closed by contact and separation between the valve body and the seat ring. However, since the flow velocity becomes extremely high in the narrowed portion (contracting portion) of the valve, the seat ring located in this constricting portion is gradually damaged by the energy of the high flow velocity. In particular, when the controlled fluid is steam, the rate of damage increases. Further, when the fluid is a powder having a high hardness, the fluid is caught between the valve body and the seat ring, and both are easily worn. The purpose of the butterfly valve used for the flow rate control is to regulate the flow rate and the pressure by narrowing the opening of the valve, so that a flow contraction portion always occurs. Therefore, how to extend the life of the seat ring and extend the maintenance period is an important issue for this type of butterfly valve.

Conventionally, various proposals have been made to extend the life of a seat ring of a butterfly valve, for example, in Japanese Patent Application Laid-Open No. 57-15 / 1982.
No. 7,866, JP-A-61-38268, JP-A-9-14463, and the like. JP 5
The butterfly valve disclosed in Japanese Patent Application Laid-Open No. 7-157866 is an example of a flow control valve, and has a structure in which a valve body directly contacts a valve body inner surface without a seat ring as shown in FIG. However, in such a structure, when a high-temperature fluid is controlled, the valve body is exposed to the outside air and cooled, so that a difference occurs in thermal expansion between the valve body and the valve body, and the valve body and the valve body when fully closed. There is a problem that the gap between the valve body and the valve body must be set large, and the amount of leakage at the time of full closing increases. In particular, when the coefficient of thermal expansion of the valve body is smaller than that of the valve body, the influence is large. JP-A-61-38268
The butterfly valve disclosed in the above publication is an eccentric butterfly valve, and as shown in FIG. 6, the seat ring is formed by winding a metal thin plate around a spring to form a high sealing performance. However, in order to maintain the elasticity of the seat ring stably, it is additionally pressed by a metal plate. For this reason, there is a problem that a large space is generated in the seat ring insertion portion and the powder easily stays. JP-A-9-14
No. 463 discloses an example in which a thick metal seat ring is employed. However, as shown in FIG. 7, the valve contact shape of the seat ring is formed in a small arc, so that the fluid is However, in the case of liquid or steam, even if the contact position between the valve body and the seat ring is slightly deviated, there is a disadvantage that the leakage amount increases sharply. For this reason, high processing accuracy and adjustment of the valve closing position are required, which causes complaints and increases costs.

[0004]

SUMMARY OF THE INVENTION The present invention can reduce the damage to the seat ring, prolong the service life, reduce the maintenance cost, facilitate the opening and closing operation of the valve body, and are not affected by thermal expansion. Another object of the present invention is to provide a butterfly valve seat ring that facilitates adjustment of manufacture and assembly of a seat ring.

[0005]

In order to solve the above-mentioned problems, the present invention is directed to a butterfly valve in which a valve seat and a valve shaft are eccentric to each other. A seat ring formed in a tapered shape with an angle that is a tangent is fixed to the valve body with a seat ring retainer, a gasket is inserted between the valve body and the seat ring and the seat ring retainer, and the outer peripheral end of the seat ring and the seat are A first gap is formed between the valve body and the ring retainer, a second gap is formed between the side surface of the seat ring and the valve body and the seat ring retainer, and a step is formed on the side surface of the seat ring; The thickness of the gasket is made larger than the inside of the step, and a gasket is inserted outside the step to prevent the gasket from protruding inward.

The material of the seat ring is made of the same material as that of the valve body or a material similar in thermal expansion, and at least one of the seat ring and the valve body is subjected to a surface treatment to provide a hardness difference.

[0007] The gasket is characterized in that it is selected from sealing materials having sealing performance such as rubber, polytetrafluoroethylene, graphite and the like.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below. Referring to FIGS. 1-4, (1)
Denotes a valve body of the butterfly valve according to the present invention, and a cylindrical fluid passage (2) is provided at the center thereof. Numeral (3) is a disc-shaped valve element, which is rotatably supported in the valve body (1) by a valve stem (5) positioned eccentrically with respect to the valve seat (4).
The seat ring (6) constituting the valve seat (4) is made of a metal ring as shown in FIGS. 3 and 4. The inner peripheral valve seat surface is formed as a tapered surface. Ring (6) is in tapered contact. As shown in FIGS. 1 and 2, the seat ring (6) is sandwiched between the side surface of the valve body (1) and the seat ring retainer (7), and is fixed to the valve body (1). A gasket (8) is interposed between the valve body (1) and the seat ring retainer (7) and the seat ring (6). Further, a first gap (S1) is created between the outer peripheral end of the seat ring (6) and the seat ring retainer (7), and the seat ring (6) is formed.
Can absorb the thermal expansion.

Further, the side surface of the seat ring (6) and the valve body.
Second gaps (S2) and (S3) are also created between (1) and the seat ring retainer (7) to allow the movement of the seat ring in combination with the elasticity of the gasket, and the seat ring ( 6) is the seat ring retainer (7) or the valve body (1)
To avoid direct contact with Therefore, heat conduction from the valve body (1) directly in contact with the outside air and the seat ring retainer (7) in contact therewith can be cut off, and the seat ring (6) caused by the difference between the outside air temperature and the fluid temperature can be cut off. ) Can be suppressed. Steps (9) are formed on both sides of the seat ring (6), and the steps (9) of the seat ring (6) are formed.
The inner peripheral side is formed to be slightly thicker to form a second gap (S2),
(S3) is the thickness (G1) of the gasket (8) after compression,
(G2). Due to the difference between the size of the second gap and the thickness of the gasket (8) and the presence of the step (9), there is no possibility that the gasket (8) protrudes into the pipe due to the influence of the fluid and is damaged.

The inner peripheral surface of the seat ring (6) is in contact with the outer peripheral surface of the valve body (3) in a tapered shape as a valve seat surface, and the taper angle (α) of the valve when the valve is assembled as a valve. It is set so as to be in contact with the outer peripheral surface of the body (3). The taper angle (α) of this seat ring and the seat ring (6)
When the valve body (3) is rotated by being sandwiched by the gasket (8), the seat ring (6) is separated from the gap (S2) between the valve body (1) and the seat ring retainer (7). It is possible to move within the gap (S3) of
Produces a smooth rotation between the valve body (3) and the seat ring (6). At the same time, the gaps (S2) and (S3) can prevent excessive movement of the seat ring (6), and can suppress occurrence of abnormal torque and increase in leakage.

The material of the seat ring (6) is preferably the same metal as the valve body or a metal having a similar coefficient of thermal expansion in order to reduce the influence of thermal expansion at high temperatures. In addition, since the seat ring (6) can be formed to be thicker in shape, it takes a long time until the seat ring is damaged even if it is damaged by a fluid, resulting in a longer life of the seat ring. Can be achieved. Surface treatment such as plating or nitriding may be performed in order to reduce the damage by giving a hardness difference to one or both surfaces of the valve body (3) and the seat ring (6). For the gasket (8), an optimal material such as rubber, polytetrafluoroethylene, graphite or the like is selected according to the fluid conditions such as the type of fluid and the temperature.

A prototype of a butterfly valve having the seat ring according to the present invention and the seat ring shown in FIG. 7 was prototyped and tested.
The leakage of the control valve allowed by the standard was verified, but if the valve opening was shifted too close by 0.6 degrees,
In the product of the present invention, the amount of leakage tended to decrease by about 20%, whereas in the prototype of FIG. 6, the amount of leakage increased by about 10%. As a result, in the prototype of FIG. 6, the arc of the seat ring is small and the gap between the valve body and the valve body is easily increased even by a small angle movement, and the adjustment of the fully closed position of the valve tends to affect the valve performance. It can be understood that in the present invention, the seat ring follows the minute angular movement of the valve body and has a wide adjustment range.

[0013]

According to the present invention, the flow rate control valve is controlled with a small valve opening, and even if the seat ring is damaged by high-speed flow or powder in the contraction part, the damage to the seat ring is reduced and maintenance is performed. By extending the period, the life of the seat ring can be extended, and the operation of the valve can be made smooth. Also, even in the case of high temperature fluid,
Since heat conduction from the main body and the seat ring retainer to the seat ring is suppressed and the influence of heat is reduced, it is possible to increase the rotational torque of the valve body and reduce the amount of leakage.
Further, the fully closed position of the valve can be easily adjusted, and since the contact portion with the valve element has a linear shape, manufacture is easy and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a butterfly valve incorporating a seat ring according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the main part.

FIG. 3 is a perspective view of a seat ring.

FIG. 4 is a cross-sectional view along the line A-A ′ in FIG. 3;

FIG. 5 is a sectional view of a conventional butterfly valve.

FIG. 6 is a sectional view of another conventional butterfly valve.

FIG. 7 is a sectional view of another conventional butterfly valve.

[Explanation of symbols]

 (1) Valve body (2) Fluid passage (3) Valve body (4) Valve seat (5) Valve stem (6) Seat ring (7) Seat ring presser (8) Gasket (9) Step (1) First (S2) Second gap (S3) Second gap (G1) Gasket thickness (G2) Gasket thickness

Claims (3)

[Claims] In a butterfly valve in which a valve seat and a valve shaft are eccentric to each other, a seat ring in which an inner peripheral valve seat surface is formed in a tapered shape with an angle at which a contact portion with a valve body is tangential is provided on a valve body. A gasket is inserted between the valve body, the seat ring and the seat ring retainer, and a first gap is formed between the outer peripheral end of the seat ring and the seat ring retainer. A second gap is formed between the valve body and the seat ring retainer, and a step is formed on a side surface of the seat ring, and an inner thickness is made larger than the step, and an outer side of the step is formed. A seat ring for a butterfly valve, wherein a gasket is inserted into the seat ring to prevent the gasket from protruding inward. 2. The seat ring is made of the same material as that of the valve body or a material similar in thermal expansion to the valve body, and at least one of the seat ring and the valve body is subjected to a surface treatment to provide a hardness difference. The seat ring according to claim 1. 3. The seat ring according to claim 1, wherein the gasket is selected from a sealing material having a sealing performance such as rubber, polytetrafluoroethylene, and graphite.