Butterfly valves are divided into concentric butterfly valve, single eccentric butterfly valve, double eccentric butterfly valve and three eccentric butterfly valve. What are the main differences between these four butterfly valves? Now, Dervos will introduce to you: 1. Concentric Butterfly Valve (Midline Butterfly Valve) The structural feature of the concentric butterfly valve is that the valve stem axis, the center of the butterfly plate and the center of the body are in the same position. It has the advantages of simple structure and convenient manufacture. The disadvantage is that the butterfly plate and valve seat are always in the state of extrusion and scratch, with large resistance distance and fast wear. In order to overcome extrusion and scratch and ensure sealing performance, the valve seat basically adopts elastic materials such as rubber or polytetrafluoroethylene, but the use of sealing materials is limited by temperature. 2. Single Eccentric Butterfly Valve The structural feature of the single eccentric butterfly valve is that the axis of the valve stem deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotation axis, which disperses and reduces the excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat, and solves the extrusion problem between the butterfly plate and the valve seat of the concentric butterfly valve. However, the scratch phenomenon between the butterfly plate and the valve seat has not disappeared in the whole opening and closing process of the valve. Therefore, the application range of single eccentric butterfly valve is similar to concentric butterfly valve, and there are few applications. 3. Double Eccentric Butterfly Valve The double eccentric butterfly valve is further improved on the basis of the single eccentric butterfly valve. Its structural feature is that the axis of the valve rod deviates from the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly plate to leave the valve seat immediately after the valve is opened, which greatly eliminates the unnecessary excessive extrusion and scratch between the butterfly plate and the valve seat, reduces the opening resistance and wear, improves the service life of the valve seat. The scratch is greatly reduced, so that the double eccentric butterfly valve can adopt metal seat, which improves the application of butterfly valve in high temperature field. However, the sealing effect is produced by the elastic deformation caused by the extrusion of butterfly plate and valve seat. It has high requirements for the closing position (especially the metal valve seat), low pressure bearing capacity and large leakage. 4. Three Eccentric Butterfly Valve To withstand high temperature, hard seal must be used, but the leakage is large; to achieve zero leakage, soft seal must be used, but it is not resista...

Plug valve is one of the earliest used valves with simple structure, fast opening and closing and low fluid resistance. Ordinary plug valves are sealed by the direct contact between the finished metal plug body and the valve body, which has the disadvantages of poor sealing, large opening and closing force and easy wear. They can only be used in low (not higher than 1 MPa) and small diameter (less than 100 mm). In order to expand the application range of plug valve, many new structures have been developed. Oil seal plug valve is the most important one. Special grease is injected from the top of the plug body between the taper hole of the valve body and the plug body to form an oil film to reduce the opening and closing torque and improve the sealing performance and service life. Its working pressure can reach 64 MPa, the maximum working temperature can reach 325℃, and the maximum diameter can reach 600 mm. The closing part of the plug valve is a cylinder with holes, which rotates around the axis perpendicular to the channel, so as to open and close the channel. Advantages of plug valve: 1. Easy for frequent operation, quick opening and closing; 2. Low fluid resistance; 3. Simple structure, relatively small volume, light weight and easy maintenance; 4. Good sealing performance; 5. The installation direction is unrestricted, the flow direction of media can be arbitrary; 6. No vibration and low noise. Classification of plug valves: 1. By structure: tight set plug valve, self-sealing plug valve, pressure balance plug valve and oil seal plug valve; 2. By channel: straight plug valve, three-way plug valve and four-way plug valve. The channel of plug valve has many forms. The common straight through type is mainly used to cut off the fluid; Three-way and four-way plug valve are suitable for fluid reversing.

The flat gate valve is a sliding valve whose closing part is a parallel gate. The closing part can be a single gate disc or a double gate disc with a supporting mechanism between them. The pressing force of the wedge to the valve seat is controlled by the medium pressure acting on the floating wedge or floating valve seat. If it is a double wedge flat gate valve, the support mechanism between the two wedges can supplement this pressing force. Features of flat gate valve: 1. The valve seat adopts O-ring seal and floating valve seat structure with preload, so that the inlet and outlet of flat gate valve are sealed in both directions. The opening and closing torque is only 1/2 of ordinary valves; 2. When fully open, the channel is smooth and straight, the flow resistance coefficient is very small, there is no pressure loss, simple cleaning; 3. The packing structure with self sealing ability is adopted, the sealing performance is more reliable than ordinary graphite packing. In addition, grease is injected into the sealing surface of the packing, the sealing surface meets the zero leakage standard; 4. When the flat gate valve is closed, it can automatically remove the high pressure in the inner cavity to ensure the safety of use; 5. Fully enclosed structure, good protection performance. Flat gate valve is divided into single gate plate and double gate plate. According to the connection mode, it can be divided into butt welded flat gate valve and flange flat gate valve. Features of butt welded flat gate valve: 1. Small fluid resistance and small scouring and erosion of sealing surface by medium; 2. Opening and closing is labor-saving; 3. The flow direction of the medium is unrestricted, no turbulence and no pressure reduction. 4. Simple shape, short structure length, good manufacturing technology and wide application range. Flange flat gate valve is stable and reliable when used in pipeline, Therefore, DERVOS recommends that flange flat gate valve could be used in high pressure pipeline. Features of flange type flat gate valve: 1. The sealing structure of flange flat gate valve is elastic with preload, and the upstream and downstream sealing seats are sealed at the same time. There is always face-to-face seal between the valve seat and the seal; 2. The valve seat has self-cleaning function and is not directly scoured by the air flow during the opening or closing of the valve. The valve seat is made of lubricated and non abrasive materials; 3. The problem of the valve actuator will not affect other parts of the valve, and the maintenance and replacement can be carried out without removing the valve; 4. When the flange flat gate valve is fully opened, the channel is smooth and straight, the flow resistance coefficient is very small, there is no pressure loss, and the pipeline can be cleaned by wool ball.

2022 is the year of tiger in China. It placed people's expectations that they could be as brave and strong as tigers and keep working hard. DERVOS Annual meeting of 2021 was held in the second working day after the Spring Festival holiday, which is also Valentine's Day, 14th Feb. In the morning, the heads of all departments made work reports. In the work reports, they reviewed the work achievements of the past year. At the same time, the Department's work objectives and work plans for the new year were formulated. Finally, Eric, our general manager summarized and planed the direction of struggle in 2022.The key word is pragmatic and development. Pragmatic means to work steadily, reduce trial and error costs, and carry out work with practical and feasible schemes. In the meantime, go from complexity to simplicity,result oriented, the final goal is to achieve the development. In the evening, the annual work summary came to an end and the annual dinner officially began. This was not only a good time for different departments to get together, but also an opportunity to win big prizes. DERVOS people work hard and also love life. We are grateful to the support of our business partners over the past year. We will continue to improve and provide partners with the most professional support and meticulous service.

In Short, the role of the check valve in pipe system is to prevent backflow of media. Check valve alsocan be divided into hard seal check valve and soft seal check valve--soft seal check valve sealing performance isoutstanding and it can reach zero leakage, butcanonlybe putin the normal temperature and low pressure pipeline, while hard seal check valve can. And due to the manufacturing process,hard seal check valvealwayshas a certain amount of leakage. But the advantage of hard seal is that it can adapt to high temperature and high pressure environment. Therefore, you can nothave a frivolous judge that the hard seal check valve is good or soft seal check valveis. Both have their advantages as long as they are correctly installed in the appropriate working conditions on the pipeline. So how to make a choice between them two? 1. Soft seal The spin or seat of soft seal check valve is made of non-metallic materials (mainly PTFE, and rubber, etc.). It enjoys remarkable sealing performance, but sustains reproof that it may leave more or less residues (such as welding slag, iron filings, etc.) in the pipeline system as they flow through the regulating valve, which is prone to hurt the valve seat or spool. Therefore, choosing soft seal check valve means extra notices on the purity of  medium and cleanness of the pipeline before commissioning. 2. Hard seal Hard seal check valve would adopts welded wear-resistant alloy on its sealing surface which balances sealing performance and the service life and reliability. Although it dwarfs as a competitor with soft seal check valve when it comes to sealing performance, it is enough to meet the needs of most working conditions, and it enjoys durable and longer service life. Xiamen Dervos is an API-Certified ball valve manufacturing and trading company who specializes in the production of various kinds of valve. In addition to all kinds of common valves such as gate valves, globe valves, plug valves and butterfly valve , we also produce other unconventional valves as long as our customers file their requirements. We stand ready whenever you have any requests. Contact us today for the best valve purchasing experiences.

It comes to Christmas again where 2021 is about to arrive its destination. At the intersection between two years, Dervos of course will have celebrating activities to mark the important moment. In the morning of Christmas, our secretary prepared a bag full of candies for every one of us. Apart from candies, there was also an apple for everyone, which is an unusual popular tradition on Christmas Eve in China. The tradition came about because the Chinese word for apple sounds similar to the word for Christmas Eve, and it sands for best wishes. Ping pong, as the most popular sports game in China, has become a fad in Dervos for the past few months. When Christmas holiday met ping-pong, we decided to hold a special, Chinese-featured game this time--a ping-pong competition. We, divided into 4 teams, had to go through a series of sessions--singles, doubles and mixed doubles, to determine who will have the last laugh. And what was surprising was that we really prepared trophies, a ribbon-cutting and a banner for the opening ceremony. That was so funny. That was a funny and stressful afternoon, you have to say. Because infrequently we took it so seriously that everyone practiced and performed hard, longing for the laurel of the team. Though every team was brilliant no matter the result. And unarguably the best play went to West Lin who led his team to runner-up when the situation was not optimistic for him. In the end of this article, Dervos is honored to spend another year with our customers and friends. We sincerely wish you a happy holiday season and a best new year.