The development history of butterfly valve _ introduction of the use of the ear butterfly valve

In the 1930s, Americans invented butterfly valves. In the 1950s, butterfly valves were introduced to Japan, and the promotion of butterfly valves in China was after the 1970s. At present, butterfly valves in the world above DN300 mm have gradually replaced gate valves. Compared with the gate valve, the butterfly valve has the advantages of short opening and closing time, small operation, small installation space and light weight.

As a "big family" in the valve, the application range of butterfly valves in China is constantly expanding, and the demand is increasing year by year, and more and more attention is being paid. This paper introduces the structure, performance and basic knowledge of the butterfly valve, and briefly summarizes the future development direction of the butterfly valve.

The first part approaches the butterfly valve

Since its invention, butterfly valves have been used more and more widely in various fields of life and work, playing an irreplaceable role. From the central sealing butterfly valve to the single eccentric sealing butterfly valve to the double eccentric sealing butterfly valve, the last is the widely used three eccentric sealing butterfly valve. The historical inheritance of butterfly valve technology confirms the continuous improvement of butterfly valve technology.

First, the basic knowledge of the butterfly valve

The butterfly valve opening and closing member is a disc-shaped disc that rotates around its own axis in the valve body to achieve opening and closing or adjustment. When the butterfly valve is fully open to full clearance, it is usually less than 900. The butterfly valve and the butterfly rod itself are not self-locking. For the positioning of the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of a worm gear reducer not only enables the disc to have a self-locking capability, but also stops the disc at any position and improves the valve's operating performance.

The industrial special butterfly valve is characterized by high temperature resistance, high applicable pressure range, large valve nominal diameter, valve body made of carbon steel, and the sealing ring of the valve plate adopts metal ring instead of rubber ring. Large high temperature butterfly valves are manufactured by steel plate welding and are mainly used for flue ducts and gas pipes of high temperature media.

(1) The advantages of the butterfly valve are as follows:

1. It is convenient and quick to open and close, labor-saving, and low fluid resistance, which can be operated frequently.

2, simple structure, small size and light weight.

3, can transport mud, the minimum accumulation of liquid in the pipe mouth.

4, under low pressure, can achieve a good seal.

5, the adjustment performance is good.

(b) The shortcomings of the butterfly valve are as follows:

1. The operating pressure and operating temperature range are small.

2, poor sealing.

(3) The following matters should be noted in the installation and maintenance of the butterfly valve:

When installed, the valve flap should be stopped in the closed position;

The opening position should be determined according to the rotation angle of the disc;

Butterfly valve with bypass valve, open the bypass valve before opening;

It should be installed according to the manufacturer's installation instructions. A heavy butterfly valve should be provided with a solid foundation.

Second, the classification of butterfly valves

The butterfly valve can be divided into a bias plate type, a vertical plate type, a slant plate type and a lever type according to the structure. According to the sealing form, it can be divided into two types: a relatively sealed type and a hard sealed type. The soft seal type is generally sealed with a rubber ring, and the hard seal type is usually sealed with a metal ring.

According to the connection type, it can be divided into flange connection and clip type connection; according to the transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic and electric.

(1) Classification by structure

1. Center sealing butterfly valve

2, single eccentric sealing coal valve

3, double eccentric sealing butterfly valve

4, three eccentric sealing butterfly valve

(2) Classification by sealing surface material

1, soft sealing butterfly valve.

(1) The sealing pair is composed of a non-metallic soft material and a non-metallic soft material.

(2) The sealing pair is composed of a metal hard material and a non-metal soft material.

2, metal hard seal butterfly valve. The sealing pair is composed of a metal hard material and a metal hard material.

(3) Classified by seal form

1. Forced sealing butterfly valve

(1) Elastic sealing butterfly valve. The sealing specific pressure is generated by the valve plate pressing the valve seat, the valve seat or the valve plate when the valve is closed.

(2) A torque seal butterfly valve is applied. The seal specific pressure is generated by the torque applied to the valve shaft.

2, pressure sealing butterfly valve. The seal specific pressure is generated by the compression of the spring seal element on the valve seat or valve plate.

3, automatic sealing butterfly valve. The seal specific pressure is automatically generated by the medium pressure.

(4) Classification by work pressure

1, vacuum butterfly valve. A butterfly valve with a working pressure lower than the standard atmospheric pressure.

2, low pressure butterfly valve. Butterfly valve with nominal pressure PN < 1.6MPa.

3, medium pressure butterfly valve. A butterfly valve with a nominal pressure PN of 2.5 MPa to 6.4 MPa.

4, high pressure butterfly valve. A butterfly valve with a nominal pressure PN of 10.0 MPa to 80.0 MPa.

5, ultra high pressure butterfly valve. Butterfly valve with nominal pressure PN > 100MPa.

(5) Classification by working temperature

1, high temperature butterfly valve. Butterfly valve with t > 450 °C

2, medium temperature butterfly valve. Butterfly valve at 120 °C < t < 450 °C

3, normal temperature butterfly valve. -40 °C < t <; 120 °C butterfly valve

4, low temperature butterfly valve. Butterfly valve with -100 °C < t < -40 °C

5, ultra-low temperature butterfly valve. Butterfly valve with t < -100 °C

(6) Classification by connection

1. Clip-on butterfly valve.

2, flanged butterfly valve.

3, the ear type butterfly valve.

4, welded butterfly valve.

Part II Basic knowledge of eccentric sealing butterfly valves and other valves

The family of butterfly valves can be described as huge. In the case of eccentric sealing butterfly valves, they can be divided into different types. The following focuses on the single eccentric sealing butterfly valve, the double eccentric sealing butterfly valve and the triple eccentric sealing butterfly valve that confirm the development history of the butterfly valve. In addition, there are certain introductions to the characteristics of flanged butterfly valves and elastic metal hard seal butterfly valves.

First, the characteristics of single eccentric sealing butterfly valve

In order to solve the problem of the pressing of the butterfly plate and the valve seat of the concentric butterfly valve, a single eccentric butterfly valve is generated, and the structural feature is that the axial center of the valve stem deviates from the center of the butterfly plate, so that the lower end of the butterfly plate no longer becomes the rotary axis, Disperses and reduces the excessive extrusion of the lower end of the disc and the valve seat. However, due to the single eccentric structure, the scraping phenomenon of the disc and the valve seat does not disappear during the whole switching process of the valve, and the application range is similar to that of the concentric butterfly valve, so it is not used much. The single eccentric sealing butterfly valve has the following characteristics:

  1 . It has a sealing structure with reliable performance and long service life.

  2 . It has a truss structure with small flow resistance, good rigidity and low pressure loss.

3 . The valve plate seals are easy to replace and easy to repair.

4 . The valve plate seal has a “T” shape and the seal pair is linearly sealed.

5 . The bottom end of the valve is made of bimetallic thrust washers for excellent thrust performance.

6 . The valve can be installed either vertically or horizontally for good applicability.

7 . This type of valve is recommended for one-way use and can be used in both directions when the reverse seal requirements are not critical.

  8 . When the valve is completely closed, the leak test leak is zero.

  9 . Replace the valve plate seal, O-ring, valve body, valve plate, shaft and other materials, can be applied to a variety of media and different temperatures.

Second, double eccentric sealing butterfly valve features

Further improved molding on the basis of a single eccentric butterfly valve is currently the most widely used double eccentric butterfly valve. The structural feature is that the stem axis is offset from the center of the disc and from the center of the body. The double eccentric effect allows the disc to be quickly disengaged from the valve seat after the valve is opened, which greatly eliminates unnecessary over-squeezing and scraping of the disc and the valve seat, reduces the opening resistance, reduces wear and improves The seat life. The scraping is greatly reduced, and the double eccentric butterfly valve can also be used with a metal valve seat, which improves the application of the butterfly valve in the high temperature field. However, because the sealing principle belongs to the position sealing structure, that is, the sealing surface of the butterfly plate and the valve seat is in line contact, and the elastic deformation caused by the butterfly plate pressing the valve seat produces a sealing effect, the closing position is required (especially metal). Seat), low pressure bearing capacity, which is why people think that butterfly valves are not resistant to high pressure and large leakage.

Its characteristics are as follows:

1. Adopt full flow design, free from the influence of impurity jamming. The joint “O” type sealing line at both ends makes the pipeline installation without gasket and maintains reliable sealing. Different materials can be selected according to different use requirements.

2. The butterfly material adopts streamline design, which can be used in both directions, with small flow resistance and excellent flow characteristics.

3. The axle pin adopts the unloading structure, which can tightly bond the disc valve stems without weakening the strength of the shaft and having good interchangeability.

4. The valve body connection can be applied to ANSI125/150, DIN2501 PN10/16, JISB2210 10K, JIS G5527 7.5K standard.

Three or three eccentric sealing butterfly valve features

Since its inception, the three-eccentric butterfly valve has undergone a process of self-improvement and continuous development in order to meet the increasingly severe working conditions. Even if the highest zero leakage is required, the triple eccentric butterfly valve can be theoretically implemented, but in reality it still relies on careful design and precise manufacturing. Taking the world-famous Babel Valve Co., Ltd. as an example, the company introduced the tri-eccentric butterfly valve Tritec based on the advantages and disadvantages of other brands of three eccentric butterfly valves. Its characteristics are as follows:

(1) API specifications

As we all know, API609 has in fact become an international specification for valves used in industrially important pipelines. Tritec is manufactured in the latest version of 1997, which is fully compliant with the API609 specification. The basic design of the triple eccentric butterfly valve is not limited to only one API specification, but BS5155 ANSI B 16.34, ASME SEC VIII and other major specifications can be matched, which ensures that the three eccentric butterfly valve has its place in all industrial fields.

(2) Double safety structure

The three eccentric butterfly valves are strictly in accordance with the specifications of API609. In order to prevent the deformation of the butterfly plate, the misalignment of the valve stem and the bite of the sealing surface caused by the influence of fluid pressure and temperature, two separate sides are respectively installed on the lower side of the butterfly plate. Independent thrust ring to ensure that the valve can work under any working conditions;

At the same time, in order to prevent sudden accidents caused by broken or flying out of the valve stem caused by unknown reasons, separate valve stem fly-out prevention mechanisms are designed in the inner and outer parts of the lower end of the valve.

(3) No dead zone design

In the design process, special consideration is given to the application problems in the field of regulation, making full use of the sealing principle of the triple eccentric butterfly valve, so that the butterfly plate does not scrape the valve seat when the valve is switched, and the torque of the valve stem is directly transmitted to the sealing surface through the butterfly plate. That is to say, there is almost no friction between the butterfly plate and the valve seat, thus eliminating the jumping phenomenon that is common when opening the ordinary valve, and erasing the control caused by friction and other unstable factors within the low opening range of the valve. Phenomenon, that is, eradicating the dead zone (not feeling). This means that the three eccentric butterfly valve can enter the controllable area from 0 degrees to 90 degrees, and its normal regulation ratio is more than 2 times that of the general butterfly valve, and the regulation ratio can be as high as 100:1 or more. This creates a good condition for the use of the three eccentric butterfly valve as a regulating valve, especially in the case of a large diameter, the cost of the shut-off valve is extremely high, and in addition, the shut-off valve cannot achieve zero leakage, and in the case of an emergency shut-off, it must be The shut-off valve is installed on the side of the shut-off valve, and the three eccentric butterfly valves are regulated and shut down in one body, and the economic benefit is extremely considerable.

(four) body valve seat structure

There are two types of valve seat mounting structures for the three eccentric butterfly valves, most of which are mounted on the butterfly plate for convenience, but the three eccentric butterfly valves adopt the body valve seat structure to mount the valve seat on the body. The advantage is that compared with the butterfly seat, the chance of the valve seat directly contacting the medium is greatly reduced, thereby reducing the degree of erosion of the valve seat and prolonging the service life of the valve seat.

(5) Thin layer valve seat structure

The valve seat is made of a stack of stainless steel sheets and graphite sheets. This structure can effectively prevent the influence of tiny solids in the medium and the sealing surface of the sealing surface caused by thermal expansion. Even if slight damage occurs, no leakage will occur. This is unimaginable for a double eccentric butterfly valve.

(6) Replaceable seal pair

The sealing pair can be described as unique, not only the body seat can be replaced, but also because the sealing surface of the butterfly plate is independent of the butterfly plate, the sealing surface of the butterfly plate can also be replaced, that is to say, when the sealing surface of the butterfly plate is damaged, it is not necessary to move the door. Back to the manufacturing plant or the large-scale decomposition valve, you only need to change the sealing surface of the butterfly plate, which not only greatly reduces the maintenance cost, but also greatly reduces the maintenance man-hour and maintenance intensity and difficulty.

(7) Balanced fixed structure

Starting from the shape characteristics of the sealing surface of the triple eccentric butterfly valve, the sealing pair fixing method adopts the elliptical shape of the bolt to fix, not only the positioning is accurate, but also the balance force is applied to each bolt, and the sealing pair generated due to uneven stress distribution is eliminated. Loose, leaking.

(8) Essential refractory structure

Many valves claim to have a refractory construction, but most of them use a soft and hard double seat construction to reduce leakage, which is dangerous. Incomplete combustion of the soft-seal valve seat in the fire causes stress on the metal-supporting valve seat and deformation of the temperature difference, resulting in failure of the fire-resistant function. Therefore, at present, Europe and the United States are gradually eliminating such a nameless fire-resistant valve. Because Tritrc is a zero-leakage, it does not require the help of a soft seal. It is a veritable essential refractory structure and has a certificate of fire resistance inspection for API607, API6FA and BS6755Part2. This ensures that Tritec can be used in a variety of hazardous areas such as petroleum and petrochemicals.

(9) High sealing packing structure

In the leakage problem of the valve, it is conventionally concentrated on the leakage of the valve seat, that is, the internal leakage, and the leakage of the filler portion, that is, the external leakage, is neglected. In fact, in today's contemporary society where environmental issues are increasingly valued, it is an indisputable fact that external leakage is far more harmful than internal leakage. The three eccentric butterfly valve is a rotary valve, and its valve stem action is only 90 ° rotation. Compared with the valve stem, the shut-off valve and the like, the valve stem is subjected to the spiral multi-turn reciprocating motion, and the packing portion is subjected to low degree of wear and is relatively used. Long life, and because Tritec has adopted the highest standard design for preventing external leakage in packing seals, it can guarantee the standard sealing performance below 100ppm when performing external leakage test according to EPA21. In fact, in the existing test results, the external leakage value was as low as 7 ppm under Lloyd's monitoring. These indicators mean that Tritec can be used in toxic and hazardous media pipelines in a variety of fields, including chemicals.

Fourth, the characteristics of the flanged butterfly valve

The flange butterfly valve introduces the self-sealing design concept, in which the connection between the valve flap and the valve shaft adopts a patented design to withdraw the pin structure. The main features of the valve