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.

In an instant, fourteen years have passed. Unconsciously, we ushered in the 14th anniversary of Dervos. During these 14 years, through continuous practice and learning, Dervos have withstood countless tests and worked tenaciously in this rapidly developing new era. In order to celebrate the birhday of Dervos, we gave up the monotonous indoor entertainments and embraced nature this year, went to Mount Wuyi, which is known as one of the "World Cultural and Natural Heritage Sites". In order to have an enough leisure holiday so that everyone can have a full rest, CEO Eric arranged for us five days to enjoy nature. After breakfast at the B & B every morning, we will follow the tour guide to the scenic spots of Mount Wuyi: Dahongpao scenic spot, Tianyou peak, Yunv peak, yixiantian, bamboo raft rafting, etc. It has to be said that mountain climbing is a challenging sport for a group of urban beauties who are always accompanied by computers! Nevertheless, everyone is enthusiastic and determined to reach the top. Maybe you will see some breathless figures in the process of climbing, but thanks to Ken, Judy, Matthew and others who have good physical strength to help us explore the way and encourage us to insist, so we can have so many group photos of the top of the mountain! In addition to climbing, the most amazing thing is the live performance of impression Dahongpao, which is directed by Zhang Yimou, Wang Chaoge and Fan Yue, with nearly 300 actors. It uses the world's first 360 degree rotating auditorium, you can see different scenes every time you rotate. It shows the history of tea, tea making technology. The antique pavilions brought us back to the past. Although the Mount Wuyi trip is over, the valve journey of Dervos is continuous. We will continue to provide you with high quality valves and considerate services! Let's develop together!

Exponor, an exhibition that takes place in Antofagasta - Chile every two years, links the latest advances aimed at the mining sector. It has a complete program of activities aimed at generating business opportunities and strengthening and establishing business networks at the national and international level. This year's exponor has been held from June 13 to 16, 2022. The industries participating in this exhibition include heavy equipment, process equipment, machinery, engineering services and electrical goods, automation, and control, etc. Our partner, the exclusive agent in Chile participated in exponor with our products. ①High Performance Butterfly Valve ▼Double offset, soft seated ▼Design: API609 ASME B16.34 ▼Pressure: Class 150-Class 600 ▼Size: 2”-60" ▼Material: Carbon Steel, Stainless Steel, Alloy Steel ②Metal Sealed Butterfly Valve ▼Triple offset, metal seated ▼Design: API609 ASME B16.34 ▼Pressure: Class 150-Class 1500 ▼Size: 2"-60” ▼Material: Carbon Steel, Stainless Steel, Alloy Steel ③Knife Gate Valve ▼Uni-directional or bi-directional, soft or metal seated ▼Design: MSS SP 81 ▼Pressure: Class 150 ▼Size: 2"-60" ▼Material: Carbon Steel, Stainless Steel, Alloy Steel, Ductile Iron ④Lined Ball Valve ▼Design: ASME B16.34 ▼Pressure: Class 150 ▼Size: 1/2"-16” ▼Material: Carbon Steel, Stainless Steel They all can be customized according to your needs! In May of 2022, DERVOS won a project which end user is AngloAmerican and application is iron ore mining. With this success, DERVOS is ready for more projects in mining industry.

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.