CN100482986C - Three eccentric two-way self-tightening sealing rubber butterfly valve - Google Patents

Abstract

The invention discloses a rubber sealed butterfly valve, it has combination deltoid rubber seal band whose section structure is designed and calculated according to the sealed principle, seal surface of valve body is thethree eccentricity slope-intercept seal surface with best contact deviate, so it is simply structured and good sealed, also it achieves 'two-way sealed'. Since the sealing force of self-tight sealed structure is much smaller and the medium force of the butterfly plate will not act on the sealed surface directly, friction torque of the sealed surface is really small, the life of the rubber sealed bank can be improved by more than two times, since size of section of rubber sealed band is small, we can save large quantity of rubber, and decrease the cost of production and material.

Description

Triple eccentric two-way self-tight sealing rubber butterfly valve

technical field

The invention relates to a valve, in particular to the technical field of a rubber-sealed butterfly valve, specifically a triple-eccentric bidirectional self-tightening sealed rubber butterfly valve.

Background technique

Due to its simple structure and low level of manufacturing technology, rubber-sealed butterfly valves are still widely used in general industrial normal temperature and low pressure pipelines, especially in the construction of urban water supply pipelines. At present, there are two main types of sealing structures for rubber-sealed butterfly valves. One is a centrally symmetrical rubber-sealed butterfly valve. This butterfly valve mainly relies on the interference fit between the butterfly plate and the rubber seat to form a sealing force. The amount of interference compression between the butterfly plate and the rubber seat determines the level of the specific pressure of the seal. Generally, the interference compression of this butterfly valve is 1.4-2.2mm, and the specific pressure that can be formed is between 0.8-2Mpa. When the valve is in the closed state, the rubber seat is in the interference compression deformation, and when it is in the open state, the joint between the butterfly plate and the upper and lower ends of the rubber seat is still in the compression deformation. In this compressed state for a long time, the rubber material is very easy to age and lose its elasticity. Therefore, due to the aging of the rubber material, the valve will start to leak when the specific pressure of the seal must rise to a certain level. Especially when the valve is in the closed state, the joint between the upper and lower ends of the rubber valve seat is prone to leakage, and the pressure medium will leak into the gap between the valve body and the rubber valve seat, causing the outlet end of the rubber valve seat to leak. The inner circle bulges to form a swelling circle, at this time the butterfly plate is suffocated and cannot be opened. Therefore, the sealing reliability and service life of this valve are very limited, and it is only suitable for parts that are often opened and closed and easily replaced. In addition, due to the large cross-sectional size of the rubber valve seat and the consumption of many rubber materials, the production cost is high.

Another rubber butterfly valve is the eccentric rubber seal butterfly valve. The sealing structure of this butterfly valve is mainly to overcome the problem of rapid aging and failure of the rubber seat of the axially symmetrical butterfly valve due to interference compression deformation. The sealing structure of this product is to deviate the rubber valve seat from the center of the butterfly plate, valve stem and valve body, and at the same time, the rotation center of the valve stem also deviates from the center of the valve body, thus forming a double eccentric structure. In this way, when the valve is in the open state, the outer circle of the butterfly plate is completely separated from the rubber valve seat, and the sealing surface of the eccentric rubber valve seat is in a free state without compression, which solves the aging failure problem of the rubber valve seat due to compression deformation. But these two sealing pairs are two completely different sealing structures. The amount of interference compression of the rubber seat of the axisymmetric butterfly valve depends on the nominal pressure of the medium, and it has nothing to do with the direction of the medium's force. Therefore, the axisymmetric rubber-sealed butterfly valve has no restriction on the flow direction of the medium, that is, it can be bidirectionally sealed. The eccentric rubber seal butterfly valve is different, it relies on the compression force generated by the butterfly plate on the eccentric valve seat to form the sealing force. This pressing force is composed of two forces. One is the center of the arc sealing surface of the butterfly plate and the center of the sealing surface of the eccentric valve seat to the center of the valve stem. The center of the valve stem is designed according to the interference fit. The round sealing surface is pressed tightly on the valve seat, which is the closing force. The other is the media force. The two forces together act on the eccentric rubber valve seat through the butterfly plate and form a certain specific pressure, which is the actual sealing specific pressure q. The basic principle of the design of general industrial sealing valves is that the actual sealing specific pressure q must be greater than the necessary sealing specific pressure q _MF and at the same time smaller than the allowable specific pressure [q] of the sealing material, so that the valve can be reliably sealed. Their relationship is q _MF < q < [q]. But when the direction of the force of the medium changes, that is, when the flow direction of the medium in the pipeline is opposite, the eccentric rubber butterfly valve will appear q<q _MF , and the valve will leak at this time. Therefore, sealing butterfly valves similar to this eccentric structure are all unidirectional sealing valves.

Since the sealing mechanism of the above products is pressure forced sealing, the torque when the valve is opened and closed is particularly large. Due to the large cross-sectional structure size of the rubber valve seat, the amount of rubber material is particularly high, which increases the production cost. Therefore, the above There are obvious defects and deficiencies in the sealing performance of the product and the rationality of the structure.

Contents of the invention

The purpose of the present invention is to provide a triple eccentric bidirectional self-tightening sealing rubber butterfly valve with simpler structure, more reliable sealing performance, complete bidirectional sealing, long service life, smaller torsional moment and lower production cost. Its technical and structural scheme is realized in this way: the structure includes parts such as valve body, valve stem, butterfly plate, pressure ring and rubber sealing ring. The rubber sealing ring is fixed on the butterfly plate by the pressure ring. It is characterized in that : The cross-sectional structure of the rubber sealing ring is to combine its flat square round head with the rubber gasket between the butterfly plate and the pressure ring to form a combined rubber ring in the shape of a flat square-round head.

When the butterfly valve is closed, the self-tightening compression amount of the outer arc diameter of the flat square round head section of the rubber ring is represented by the code Sq. The width of the groove formed by the butterfly plate and the pressure ring = the diameter of the outer arc of the flat square head section when the rubber ring is in a free state, and the two sides of the sealing surface must be processed with a transition arc, and the size of the transition arc ≥ self-tightening compression Sq, press Sq is rounded up to an integer in millimeters. In addition, the matching gap between the outer circle of the butterfly plate and the inner hole of the sealing surface of the valve body is δ, the minimum gap δmin=Sq/5, and the maximum gap δmax=Sq/3.

The obvious effect after the implementation of this technology is: the combined rubber ring in the shape of a flat square round head is used, and the self-tight sealing principle is successfully applied to the design of butterfly valve products, so that the sealing performance is more reliable, and it can completely seal in two directions. . Due to the small cross-sectional size of the rubber ring, the consumption of expensive rubber materials is greatly reduced. Since the friction torque of the sealing surface of the self-tightening sealing structure is much smaller than that of the forced sealing structure, the selected valve driving device and related parts are much smaller. The obliquely truncated conical sealing surface, and the self-tightening compression Sq of the rubber ring and the fit clearance δ are reasonably determined through strict calculations, and the size of the transitional arc of the sealing surface is reasonably determined, effectively avoiding the occurrence of "edge trimming" and "cracking" of the rubber ring phenomenon, so that the service life of the rubber ring is increased by 2 times, and the comprehensive production cost is greatly reduced by 50%.

Description of drawings

Figure 1 is a structural schematic diagram of a triple eccentric bidirectional self-tightening seal rubber butterfly valve.

FIG. 2 is a top sectional view of FIG. 1 .

Figure 3 is a cross-sectional structure diagram of the rubber ring.

Fig. 4 is a compression deformation diagram of the outer arc R of the oblate square round head section of the rubber ring when the medium force = 0.

Fig. 5 is a compression deformation diagram of the outer arc R of the oblate square round head section of the rubber ring when the direction of the acting force of the medium is the positive direction.

Fig. 6 is a compression deformation diagram of the outer arc R of the oblate square round head section of the rubber ring when the direction of the medium acting force is in the opposite direction;

Among them, 1-valve body, 2-valve stem, 3-butterfly plate, 4-pressure ring, 5-rubber ring;

Detailed ways:

Below in conjunction with the accompanying drawings, the triple eccentric two-way self-tightening sealing rubber butterfly valve (hereinafter represented by code DN300) with a valve diameter of 300 mm is taken as an example to further describe the present invention.

See Figure 1 and Figure 2. The triple eccentric two-way self-tightening seal rubber butterfly valve is composed of a valve body 1, a valve stem 2, a butterfly plate 3, a pressure ring 4 and a rubber ring 5, among which the butterfly plate 3 is connected to the valve body through the valve stem 2. 1 are assembled together, and the butterfly plate 3 and the valve stem 2 are integrated through the positioning pin.

See Figure 1 and Figure 2, when the valve stem 2 is rotated by 90° by the driving device, the butterfly plate also rotates at the same time to realize the opening and closing of the valve (the dotted line figure in Figure 2 is the open state of the butterfly plate). The oblate square round head part of the rubber ring 5 is enclosed in the groove formed by the pressure ring 4 and the butterfly plate 3, and its groove width = the diameter d of the outer arc of the oblate square round head section of the rubber ring in Figure 3, that is, the flat square round head of the rubber ring Twice the radius R of the outer arc of the square head section, where the width of the groove formed by the DN300 butterfly plate and the pressure ring = 5. That is, the outer arc diameter of the oblate square round head section of the rubber ring is d=5.

As shown in Fig. 4, when the force of the medium in the valve pipeline is P = 0, the outer arc R of the oblate square head section of the rubber ring 5 is compressed and deformed, thereby forming a pre-compressed sealing force p ₁ , (p ₁ is equivalent to the traditional The required sealing specific pressure q _MF in valve design is calculated and determined by the calculation formula: p ₁ =E*f*ε _c (MPa):

In the formula: p ₁ ___ pre-compression sealing force (MPa).

E___The modulus of elasticity of the sealing material, DN300 adopts nitrile rubber with a hardness of Shore A70 degrees, taking 4MPa.

f___The coefficient related to the material of the rubber ring, take 1.27

ε _c ___Compressibility of the outer arc diameter d of the oblate square head section of the rubber ring

_εc = Sq/d

In the formula: Sq___ the self-tightening compression amount of the outer arc diameter d of the flat square round head section of the rubber ring (mm)

Sq＝0.1564d+0.1069(mm)

d___Rubber ring flat square round head section outer arc diameter (mm)

Substitute the relevant data of DN300 into the above formula:

p ₁ =4×1.27×(0.1564×5+0.1069)/5(Mpa)

＝0.9032Mpa

Since rubber is a viscoelastic material, similar to high-viscosity fluid, it can directly transmit the medium pressure to the sealing surface of the valve body, that is, the force of the medium indicated in Figure 5 and Figure 6 is transmitted to the valve body 1 through the rubber ring 5 The sealing surface of the valve body, the force is set to p ₂ , when the medium pressure in the valve pipeline is the nominal pressure PN, that is, the medium force p ₂ = PN, at this time the actual force of the rubber ring 5 acting on the sealing surface of the valve body 1 The compressive stress is the sum of p ₁ and p ₂ , that is, q=p ₁ +p ₂ , when the nominal pressure PN of DN300=1.6Mpa, substitute the relevant data of DN300 into the above formula to get q=0.9032+1.6=2.5032 of DN300 MPa, since the allowable compressive stress [q]=5MPa of the rubber material stipulated in the "Valve Design Manual" commonly used in the valve industry, the above calculation results form a relationship of 0.9032MPa<2.5032Mpa<5Mpa, which is completely in line with the valve design The basic principle, that is, the regulations and requirements of the relationship q _MF <q<[q], shows that the seal is reliable.

The transition arc r on both sides of the sealing surface of the valve body 1 in Fig. 5 and Fig. 6 is obtained from the formula of the self-tightening compression amount Sq=0.1564d+0.1069 of the rubber ring 5, and the Sq=0.1564×5+0.1069=0.889 of DN300. The result is rounded to an integer equal to 1 in millimeters, so the transition arc r on both sides of the DN300 valve body sealing surface is taken as 1.

In Figure 5 and Figure 6, in order to ensure that the rubber ring does not "squeeze the gap" phenomenon, the matching clearance between the outer circle of the butterfly plate 3 and the inner hole of the sealing surface of the valve body 1 is determined in this way, the minimum clearance δmin=Sq/5, the maximum The gap δmax=Sq/3. Substituting the Sq value of DN300 into these two formulas: δmin=0.889/5=0.178, δmax=0.889/3=0.296, and then comparing this result with the national standard "Tolerance Fitting", it is closer to H8/ The dynamic fit of d8 level, so the matching level between the outer circle of butterfly plate 3 and the inner hole of the sealing surface of valve body 1 is H8/d8.

It can be seen from Figure 5 and Figure 6 that the rubber ring 5 is always in a free state in the groove of the butterfly plate 3 and the pressure ring 4. When the direction of the medium force p2 changes, the compression deformation of the rubber ring 5 will also follow. Change, so can reliably achieve two-way self-tightening seal.

It can be seen from Figure 3 that the cross-sectional area of the rubber ring of the present invention is very small, only 60mm ² for DN300, while the rubber seat cross-sectional area of the axially symmetrical rubber butterfly valve of the same specification is as high as 548mm ² , and the rubber ring of the eccentric rubber butterfly valve The cross-sectional area of the valve seat is also 160 mm ² , which is 9.13 times and 2.67 times that of the rubber ring of the present invention, so the material cost is significantly reduced.

From the above description, it can be seen that because the sealing surface of the valve body adopts the three-eccentric oblique truncated conical sealing surface with the best contact and separation performance, and the reasonable determination of the matching clearance between the outer circle of the butterfly plate and the inner hole of the sealing surface of the valve body, the reasonable determination The size of the transitional arcs on the sealing surface completely avoids the phenomenon of "squeezing" and "edge cutting" of the rubber ring, ensuring the service life of the rubber ring. After testing, the life test of the prototype has a switching frequency of up to 40,000 times. The rubber ring is still intact and a very satisfactory result has been achieved.

Claims (4)

1. Triple eccentric two-way self-tightening seal rubber butterfly valve, including the structure of valve body, valve stem, butterfly plate, pressure ring and rubber sealing ring, etc. The rubber sealing ring is fixed on the butterfly plate by the pressure ring. Its characteristics Its cross-sectional structure is to combine the flat square round head of the rubber sealing ring with the rubber gasket between the butterfly plate and the pressure ring to form a flat square-round head combined rubber sealing ring. When the butterfly valve is closed, the self-tightening compression amount Sq of the outer arc diameter d of the rubber ring flat square round head section is calculated according to the following formula: Sq＝0.1564d+0.1069(mm) In the formula: Sq——the self-tightening compression amount of the outer arc diameter d of the oblate square head section of the rubber ring (mm) d——the diameter of the outer arc of the cross-section of the flat square head of the rubber ring (mm); 2. The triple eccentric two-way self-tightening seal rubber butterfly valve according to claim 1: It is characterized in that: the cross-sectional shape of the rubber sealing ring, the width of the groove formed by the butterfly plate and the pressure ring = the flat square head of the rubber ring in the free state axial thickness. 3. The triple eccentric two-way self-tightening sealing rubber butterfly valve according to claim 1: It is characterized in that: the two sides of the sealing surface of the valve body must be processed with a transitional arc, and the size of the transitional arc is greater than or equal to the self-tightening compression amount Sq, which is rounded according to Sq Determined as an integer in millimeters. 4. The triple eccentric two-way self-tightening sealing rubber butterfly valve according to claim 1: It is characterized in that: the matching gap δ between the outer circle of the butterfly plate and the inner hole of the sealing surface of the valve body, the minimum gap δ min=Sq/5, the maximum gap δmax=Sq/3.

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