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.

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.

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...

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.

The opening and closing part of knife gate valve is wedge. The movement direction of the wedge is perpendicular to the fluid direction. Knife gate valve can only be fully opened and closed, can’t be adjusted or throttled. Next, let's learn about the common malfunctions and solutions of knife gate valve in the application process with Dervos! 1. Leakage of Closing Parts of Knife Gate Valve (1) Reasons of Leakage ① The sealing surface of knife gate valve is not well ground; ② The sealing ring is not tightly matched with the valve seat and disc; ③ Valve disc and valve rod are not firmly connected; ④ The valve rod is bent and twisted to make the upper and lower closing parts misaligned; ⑤ Closing too fast, resulting in poor contact or damage of sealing surface; ⑥ Improper material selection makes the valve unable to withstand medium corrosion; ⑦ Some media gradually cool down after the valve is closed, resulting in fine cracks on the sealing surface and erosion; ⑧ The valve can’t be closed tightly due to the embedding of welding slag, rust, dust and other impurities, or the valve core is blocked due to the falling off of mechanical parts in the production system. (2) Solutions ① Conduct pressure test carefully before use. If leakage is found on the sealing surface or the root of the sealing ring, handle it before use； ② Check whether all parts of the valve are in good condition in advance. Do not use the valve with bent valve rod or the valve disc is not firmly connected with the valve rod; ③ The valve should be closed firmly without strong force. In case of poor contact or obstruction between sealing surfaces, it should be opened a little immediately to let sundries flow out, then closed tightly; ④ When selecting the valve, we should consider the corrosion resistance of the valve body and closing parts; ⑤ It should be used correctly according to the structural characteristics of the valve; ⑥ In case of medium cooling and large temperature difference after valve closing, close the valve after cooling; ⑦ A filter should be added to the valve that may enter impurities. 2. Filler Leakage of Knife Gate Valve (1) Reasons of Leakage ① The filler does not adapt to the corrosion, temperature and pressure of the working medium; ② The filling method is wrong. In particular, the whole filler is placed in a spiral, which is most likely to cause leakage; ③ The machining accuracy or surface finish of the valve rod is not enough, there are ellipses or nicks; ④ The valve rod has pitted or rusted due to open air; ⑤ The valve stem is bent; ⑥ The filler has been used too long and aged; ⑦ Operation is too fierce. (2) Solutions ① Proper filler selection; ② Correct method of filling; ③ If the processing of valve rod is unqualified, repair or replace it; ④ Protective measures should be taken to prevent corrosion; ⑤ The bent valve rod should be straightened or renewed; ⑥ The filler should be replaced after a certain period of use; ⑦ Pay attention to stable operation. Open a...

Ball valve is a new type of valve widely used in recent years.Three-way ball valve is a relatively new type of ball valve. It has unique advantages in its own structure. It is widely used in petroleum, chemical industry, urban water supply and drainage and other working conditions requiring cut-off, diversion and confluence. Features of Three-way Ball Valve: 1. Integrated structure, less flange connection and high reliability; 2. Long service life and large circulation capacity; 3. According to the structural form, the three-way ball valve can be divided into L-type, T-type and Y-type. Different structural forms are selected according to different working conditions. Advantages of Three-way Ball Valve: 1. Low fluid resistance. Its resistance coefficient is equal to the pipe section with the same length; 2. Simple structure, small volume and light weight; 3. Tight and reliable, good sealing performance. It has been widely used in vacuum system; 4. Easy operation and quick opening and closing.It only needs to rotate 90° from full open to full close. It facilitates remote control; 5. Convenient maintenance. The sealing ring is generally movable, which is convenient for disassembly and replacement; 6. When the valve is fully open or closed, the sealing surface of the ball and valve seat is isolated from the medium. When the medium passes through, the valve sealing surface won’t be eroded. 7. Wide range of application. The diameter of three-way ball valve is as small as a few millimeters and as large as a few meters. It can be used in high vacuum and high pressure environments. Precautions for Maintenance of Three-way Ball Valve: 1. The valve handle rotation position should be reserved; 2. It can’t be used as throttling; 3. Ball valve with transmission mechanism should be installed vertically.