Nowadays, we have distributed our products to 5 continents around the world, with 42% in Europe, 23% in Asia, and 20% in America. Keep expanding our market is always our aim. Last week, one of our clients came to visit us before order. It’s really a good beginning before cooperation. We went to Wenzhou office in the morning, introduced our company briefly. After that, we visited the casting factory which we cooperate often to show clients the whole process of controlling casting. Here in the casting factory, we have complete equipments to do the chemical composition analysis, tensile test, impact test, RT, PT, etc. This is to make all castings are of good quality and all raw materials are traceable. In the afternoon, we visit factory. To show clients the products we are manufacturing and the equipments and workers we have. Clients are happy about this trip; hope it is the very good beginning between you and me.

Floating ball valve The sphere of the ball valve is floating, under the action of medium pressure, the sphere can produce a certain displacement and press on the seal surface at the exit end, ensuring that the outlet seal. The structure of the floating ball valve is simple and sealed well, but the load of the ball under the working medium is passed to the outlet seal ring, so it is necessary to consider whether the sealing ring material can withstand the working load of the sphere medium, and the sphere may be offset when it is affected by higher pressure. This structure is commonly used for medium and low pressure ball valves. Trunnion Ball Valve The sphere of the ball valve is fixed and does not move after pressure. Fixed ball valves are equipped with floating seat, subject to media pressure and the seat is generated to move, so that the seal ring is pressed on the sphere to ensure the seal. Bearings are usually installed on the upper and lower shafts with spheres. Small torque for operation leads to its suitability for high pressure and large size valves. Elastic Ball Valve The sphere of the ball valve is elastic. The sphere and seat seal ring are made of metal material. This valve is suitable for high-temperature and high-pressure media. An elastic sphere is an elastic slot at the lower end of the wall inside the sphere, which obtains elasticity. When closing the channel, use the wedge head of the stem to make the sphere rise and hold to tighten to seal. Release the wedge head before turning the sphere, and the sphere reverts to its original shape, allowing for a small gap between the sphere and the seat, reducing friction and operating torque of the sealing surface. V Type Ball Valve The V-shaped regulating ball valve has a shear effect on the seat because the core has a V-shaped structure. Therefore, it is suitable for paper, chemical, metallurgy and other industrial enterprises containing fiber or tiny solid particles in the suspension fluid medium of the relevant process parameters control. V-ball valve belongs to the fixed ball valve and has a single seat. Its adjustment performance is the best ball valve. Plus, its flow characteristics are equal percentage, adjustable ratio of up to 100:1. Three-way Ball Valve The tee ball valves are T-type and L-type. The T-type can connect three orthogonal pipes to each other and cut off the third channel, which acts as a diversion and convection. The L-type can only connect two orthogonal pipes to each other, and cannot maintain the interconnection of the third pipe at the same time, only for distribution.

Although gate valves and knife gate valves share many similarities, for example, they are both used in on-off applications, there are more fundamental differences existing.  THE WORKING PRINCIPLE Gate valve is opened by lifting the wedge out of the path of the fluid. It is only used in for shut-off. Previously, normal gate valves are used in the pulp and paper industry, but the stringy pulp would be stuck between the wedge and seat and prevent flow shut-off. To solve this problem, knife gate valve was designed. It is with a sharp edge to cut through the pulp and keep the fluid flowing.  APPLICATIONS As mentioned above, gate valves are applied in many industrial applications requiring shut-off valves, such as power plants, water treatment, mining and offshore applications. They can be used in demanding environments, like high temperature and high pressure environments. Knife gate valves are preferred in slurry applications because their knives can cut right through thick liquids easily. The applications include but not limited to thick flows of heavy oils, light grease, slurry, paper pulp, varnish and waste water etc.  ADVANTAGES AND DISADVANTAGES The advantage of gate valves is that they are bi-directional, suitable for demanding working conditions like high pressure & high temperature. Besides, it is quite efficient that there won’t be much pressure drop when gate valves is fully open. However, the torque of gate valves will be larger compared with other types of valves, so they will need a large force to open and close. For larger sizes, pneumatic or electric actuators will be a must, and this, of course, will lead to higher cost. Also, they take longer time to operate and need more space for installation. By contrast, knife gate valves are cheap, light and easy to operate, but the design makes them only limited to low-pressure working environment. 

Occasionally we will see some relatively large valves installed with a bypass valve. What is the function of a bypass valve? Under what circumstances do you need to install them? What is the size of the bypass valve of the corresponding equipment? In fact, the two main functions of bypass valves are for protection and for emergency. Protection The bypass valve can protect main valve from destruction due to high pressure. Before the high pressure pipeline is opened, the pressure is released through the bypass valve to avoid sudden surge of high pressure and impact on the downstream valve. In addition, the pressure difference between the two ends of the valve is too large, which will lead to high torque that can damage the valve. Thus, the valve is opened after the bypass pressure is released. Emergency The biggest advantage is that when the main valve fails or needs maintenance and repair, the pipeline can be circulated by opening the bypass valve without affecting normal production. When do we need a bypass valve?  When the main valve is with specifications below, we can install a bypass valve. (Just for reference) 2.5MPa, DN400 above 4.0MPa, DN250 above 6.4MPa, DN200 above 10MPa, DN150 above When the main valve is between DN100~DN200,its bypass valve should be DN20; When the main valve is between DN250~DN600, its bypass valve should be DN25; When the main valve is above DN600, its bypass valve should be DN40.

Dervos, not only do business with clients, we also make friends with our clients. Every year, one of our biggest clients from Argentina will come to visit us. We work with each other happily, at the same time we enjoy leisure time together. T is the first big client of Dervos in the past ten years. This friendship has been lasting for 10 years. We will keep it to another 10 years. Hope you could be our next best friends.

A seal device that prevents the medium from leaking into the stuffing box when the valve is fully open is referred to as backseat. When the gate valve, the globe valve and the throttle valve are in the closed state, there is no or little pressure in the body cavity, thus the pressure on stem packing is small. When it is opened, the packing is subjected to the working pressure. If there is backseat structure, the working medium pressure can be prevented from acting on the sealing packing, and the life of the sealing packing can be prolonged, so that the valve does not have an external leakage. Another function is that when there is leakage at the sealing packing, the valve can be fully opened to seal the upper sealing portion, so that the packing gland or the packing sleeve can be loosened to replace packing. Therefore, the upper sealing device is required for the gate valve, the globe valve and the throttle valve.