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  • Difference Between Ball Valve and Traditional Valve
    Difference Between Ball Valve and Traditional Valve Sep 01, 2022
    Valves are widely used and have many kinds. Ball valve is one of the most important valve products. Next, Dervos will introduce the difference between ball valve and traditional valve! Comparison between ball valve and traditional valve: 1. From the perspective of energy conservation and environmental protection, the ball valve is an energy-saving product. It has good circulation capacity and small flow resistance, which is very important in engineering application. 2. The ball valve has the advantages of small fluid resistance, quick and convenient opening and closing, small external size, light weight, good sealing, long service life, high safety and reliability, and convenient maintenance. Moreover, it is welcomed for its characteristics of self pressure relief and ball cleaning. 3. The opening and closing stem of the ball valve performs rotary motion. Compared with the linear motion valve, it is convenient to open and close and easy to realize the automation of valve operation. 4. It can be used for various media, pressure and temperature conditions, and the valve diameter range is also expanding. In recent years, with the breakthroughs in new structure, new materials and processing technology, ball valves are used more and more widely, and the market share increases year by year. It is one of the fastest developing valve varieties.
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  • Suggestions on Installation and Maintenance of Lift Check Valve
    Suggestions on Installation and Maintenance of Lift Check Valve Aug 24, 2022
    Lift check valve refers to a valve that automatically opens and closes the valve disc depending on the flow of the medium itself to prevent the medium from flowing backward. The function of the check valve is to only allow the medium to flow in one direction and prevent the reverse flow. Installation and Maintenance of Lift Check Valve 1. Both ends of the passage of the lift check valve must be blocked and stored in a dry and ventilated room. If it needs to be stored for a long time, please check whether there is rust and corrosion every day. 2. Before installation, the valve should be cleaned and the defects caused during transportation should be eliminated. 3. Before installation, please carefully check whether the marks and nameplates on the valve meet the use requirements. 4. The lift check valve shown in above picture can only be installed on the horizontal pipeline. 5. When installing the check valve, pay attention to the flow direction of the medium. The flow direction of medium should be consistent with the arrow direction indicated on the valve body.
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  • Advantages of Soft Seal Gate Valve in Application
    Advantages of Soft Seal Gate Valve in Application Aug 16, 2022
    Under the condition that the valve body, bonnet and all parts of the existing gate valve are in good condition, the valve cannot be used only if the sealing surface is slightly deformed or corroded, resulting in great waste. Therefore, the customer hopes that the valve seat and the sealing surface of the valve plate are not easy to deform, corrosion resistant, and the vulnerable sealing materials can be replaced. The valve plate and the sealing surface should not have friction or minimize friction during opening and closing. Dervos soft seal gate valve can meet the needs of customers. Advantages of Soft Seal Gate Valve in Application: 1. Low flow resistance. The medium channel inside the valve body is straight, the medium flows in a straight line, and the flow resistance is small. 2. Compared with the globe valve, opening and closing is labor-saving. Whether it is open or closed, the movement direction of the wedge is perpendicular to the medium flow direction. 3. The closing time is long and the water hammer phenomenon is not easy to occur. 4. The medium can flow in any direction on both sides, which is easy to install. 5. The structure length (i.e., the distance between the two connecting end faces of the shell) is small. 6. Simple shape, short structure length, good manufacturing process and wide application range. 7. Compact structure, smooth channel and long service life. 8. PTFE packing is used for reliable sealing. The operation is light and flexible.
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  • Characteristics of High Performance Triple Eccentric Two-way Hard Sealing Butterfly Valve
    Characteristics of High Performance Triple Eccentric Two-way Hard Sealing Butterfly Valve Aug 03, 2022
    At present, as a component used to realize the on-off and flow control of pipeline system, butterfly valve has been widely used in many fields such as petroleum, chemical industry, metallurgy, hydropower and so on. However, due to the limitation of its structural characteristics, it is not suitable for high temperature resistance, high pressure resistance, corrosion resistance, wear resistance and other industries. There is a more advanced butterfly valve, namely the high performance triple eccentric two-way hard sealing butterfly valve. Compared with the traditional butterfly valve, it has the advantages of high temperature resistance, light operation, frictionless opening and closing, high sealing performance and long service life. Characteristics of High Performance Triple Eccentric Two-way Hard Sealing Butterfly Valve: 1. The valve seat seal ring is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped seal ring, which has the dual advantages of metal hard seal and soft seal, and has zero leakage sealing performance at low and high temperatures. 2. The sealing surface of the valve plate and the valve seat is an inclined cone structure, and the surface of the inclined cone of the valve plate is overlaid with heat-resistant and corrosion-resistant alloy materials. 3. The spring fixed between the pressing plates of the adjusting ring is assembled with the adjusting bolt on the pressing plate. This structure effectively compensates the elastic deformation of the valve stem under medium pressure caused by the tolerance between the shaft sleeve and the valve body.
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  • Inspection Requirements of Valves
    Inspection Requirements of Valves Jul 20, 2022
    General Valve Test Pressure: this standard refers to the international standard ISO5208-2015 Pressure Test of Industrial Valves. 1. Subject and area of application This standard specifies the requirements, methods and evaluation indexes of pressure test of general valves. It is applicable to the pressure test of Gate Valves, Globe Valves, Check Valves, Plug Valves, Ball Valves, Butterfly Valves, etc. 2. Term (1) Test pressure The gauge pressure that the inner chamber of the valve should bear during the test. (2) Shell test It is a pressure test of the entire valve shell formed by the valve body and bonnet. The purpose is to test the compactness of the valve body and bonnet and the pressure resistance of the whole shell. (3) Sealing test It is a test to check the sealing performance of the sealing pair of the opening and closing parts and valve body. (4) Upper sealing test It is a test to check the sealing performance of the sealing pair of the valve stem and valve bonnet. (5) Duration of test The duration of the test under the test pressure. 3. Pressure test items (1) Shell test; (2) Upper sealing test (This test should be conducted for valves with upper sealing structure); (3) Sealing test. 4. Test requirements (1) Pressure test should be conducted for each valve before delivery. (2) Before the completion of the shell test, it is not allowed to paint the valve or use other anti-leakage coatings, but it is allowed to carry out chemical anti-rust treatment without sealing effect. For inventory valves that have been painted, the coating does not need to be removed if the user requests to redo the pressure test. (3) Before the sealing test, the oil stain on the sealing surface should be removed, but it is allowed to apply a layer of protective agent with viscosity not greater than kerosene. Valves sealed by grease are allowed to be coated with grease selected according to the design regulations. (4) During the test, the valve should not be subjected to external forces that may affect the test results. (5) Unless otherwise specified, the temperature of the test medium should be between 5 ℃ and 40 ℃. (6) The manufacturer should select the test medium that meets the relevant regulations. (7) When testing with liquid, we should eliminate the gas in the valve chamber; When testing with gas, we should take safety protection measures. (8) When conducting sealing and upper sealing tests, we should close it in the way given by the design. (9) The test pressure should meet the requirements. (10) The duration of the test should meet the requirements. 5. Test methods and procedures First, the upper seal test (This test should be conducted for valves with upper sealing structure) and shell test should be carried out, and then the seal test should be carried out. (1) Upper sealing test (This test should be conducted for valves with upper sealing structure) Close the inlet and outlet of the valve, loosen the packing gland, keep the valve fully open, close the uppe...
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  • Common Malfunctions and Solutions of Knife Gate Valve (Ⅱ)
    Common Malfunctions and Solutions of Knife Gate Valve (Ⅱ) Jul 14, 2022
    The previous article talked about two common malfunctions and solutions of knife gate valve. This article will explain the remaining two. Let's have a look! 3. Ineffective Lifting of Knife Gate Valve Stem (1) Cause of Ineffective Lifting ① Excessive operation causes thread damage; ② Lack of lubricant or lubricant is invalid; ③ The valve stem is bent; ④ Insufficient surface finish; ⑤ The valve stem nut is inclined; ⑥ Improper material selection; ⑦ The open-air valve is lack of protection, the valve rod thread is covered with dust and sand, or corroded by rain, dew, frost, snow, etc.  (2) Solutions ① Careful operation, do not use force when closing; ② Check the lubrication condition frequently and maintain a normal lubrication state; ③ Do not open or close the valve with a long lever to prevent the valve stem from being twisted; ④ Improve the processing or repair quality to meet the specification requirements; ⑤ The material should be corrosion-resistant and adapt to the working temperature and other working conditions; ⑥ The nut of the valve rod should not be made of the same material as the valve rod; ⑦ When plastic is used as the valve stem nut, the strength should be checked, the corrosion resistance and friction coefficient should not be considered only; ⑧ Open-air valves should be provided with valve stem protective sleeve; ⑨ For frequently opened valves, the handwheel should be rotated regularly to prevent the valve stem from rusting. 4. Other Malfunctions and Solutions ① Valve body cracking: It is generally caused by freezing (This situation is generally caused by improper material selection, the valve material is not resistant to low temperature). If low temperature resistant material is selected, thermal insulation measures should be taken for the valve body; ② Hand wheel damage: Due to impact or heavy operation of long lever. It can be avoided as long as the operator or other relevant personnel pay attention to it; ③ Filler gland fracture: Uneven force when pressing the filler, or the gland is defective. When pressing the filler, the screws should be rotated symmetrically without deflection; ④ Failure of connection between valve rod and ram: Solve it in terms of manufacturing.
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