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  • What’s a knife gate valve and how it works
    What’s a knife gate valve and how it works Jun 12, 2020
    A knife gate valve serves as a ‘ninja’ that wields a blade to cut off blockages of heavy liquids in the pipelines. With the sharp blade, knife gate valves usually present in a situation where there is most corrosive, aggressive and abrasive   The pulp and paper industry is the one the knife gate valves were originally designed for. In the past, the viscous pulp will be caught between the wedge and seat of an ordinary gate valve, thus the flow stream can not be shut off. The knife gate valve there, with a sharp cutting edge, is able solve the problem and cut off the pulp and seal it.   Howdoes aKnife Gate Valve Work Out of this ingenious feature, knife gate valves have emerged to be more than popular when it comes to places that transport viscous fluids, slurry and other things alike.   Today, knife gate valves are used in many processing plants and are larger in size, which makes it easier to handle dense fluids such as light oil, heavy oil, varnish, mud, waste water, and pulp. It should be noted that these valves have low pressure limits, and after the blade cuts the material it handles, the blade will return to the elastomer seal. Thick liquid can smoothly slide over these soft seals, however, when solid substances or powders pass through the knife gate, these rough substances will eventually accumulate in the soft seal at the end of the knife gate. When this happens, the sealing performance of these valves will wane. If this happens, the seal needs to be replaced.   When not to Use Knife Gate Valves Knife gate valves can not be used to regulate the flow stream, because vibration occurs when the fluid is forced to flow through a partially closed gate valve and erodes the wedge and seat. Therefore, the knife gate valve can be used only when it is completely closed or opened.
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  • Select the right valve for different working conditions
    Select the right valve for different working conditions Apr 15, 2020
    Different valves work for different conditions. It is more than wrong If you think that valve is just a simple switch to cut off the flow just like a faucet (though faucet is actually a valve in some terms). But let explore further about how the valve works and how to select the right valve for the specific purpose! The valve used to cut off the flow The straight-through valve, with a relatively small flow resistance, is usually used to cut off the flow. On the contact, downward-closing valves like globe valve and plunger valve, which have a tortuous path, have higher flow resistance than other valves. Because of that, this kind of valve is used to control flow where high flow resistance is allowed. The valve used for flow control Usually we choose the valve that is easy to adjust the flow as the flow control. The downward-closing valve mentioned above works in this condition because its seat size is proportional to the stroke of the wedge. Rotary valve (plug valve, butterfly valve, ball valve), pinch valve and diaphragm valve can also be used to control the flow. But they are only applied within a limited valve diameter range. The gate valve uses a disc-shaped gate to make a transverse movement to the circular valve seat. It can control the flow rate only when it is about to close, so it cannot be used for flow control. Valve used to reverse and divert the flow In accordance with the need of reversing and diverting, this kind of valve has three or more channels. Plug valves and ball valves are more suitable for this. However, in some cases, other types of valves can also be used for reversing and diverting as long as two or more valves are properly connected to each other. Valve used for medium with particles Speak of transferring medium with floating particles in it, the best choice is to choose the valve whose disc slides along the sealing surface. The disc will wipe this area while it moves. If the disc moves vertically along the seat ring, particles may be stuck at the sealing part. Ball valve and plug valve will clean its sealing surface when they are working, hence, they can be put in particle-mixed medium transportation. At present, no matter in the pipeline system of petroleum, chemical industry, or in other industries, the application, operation frequency and service of the valve are ever-changing. To control or eliminate even the smallest leakage, the most important and critical equipment is the valve. The ultimate control of the pipeline is the valve, which plays a unique and reliable role in various fields.
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  • The reason why cryogenic valve has a extended bonnet
    The reason why cryogenic valve has a extended bonnet Apr 10, 2020
    As we all know, the valve works for medium at temperature -40 ℃ ~ -196 ℃ is called ‘cryogenic valve’. Cryogenic valves, including cryogenic emergency shut valve, cryogenic ball valve, cryogenic gate valve, LNG cryogenic valve, NG cryogenic valve, are usually found in chemical plants such as ‘300,000 tons of ethylene’ project and production of liquefied natural gas. Ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum, and other liquid media the cryogenic valve transfers are flammable and explosive. What is more, they are going to gasify and expand hundreds of times when the temperature rises. This kind of valve is always equipped with an extended bonnet or namely extended stem. That’s because: 1. The extended bonnet can prevent the stuffing box, which plays an important role in the cryogenic valve and other valves, from the damage of low temperature. As the temperature goes down, the packing will gradually become less elastic and lost its ability to prevent leakage. Then, medium freeze in the space between the packing and the stem, hampering the movement of the stem and scratching the packing as the stem moves. In the end, what follows is severe leakage. Therefore,a extended stem is used to ensure that the packing is warm enough, at least above 8 ℃. 2. The extended structure of bonnet makes it convenient to wrap special materials around the valve, preventing the loss of cold energy. 3. The pipes and valves are often installed in the so-called 'cold box', but its ‘long neck’ can go through the wall of the 'cold box'. Based on that, The extended stem makes it convenient to dismantle or replace the main parts of the valve quickly through the bonnet. Hence,the valve body and the pipeline are welded together to reduce the leakage of the cold box as much as possible and ensure the sealing performance of the valve.
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  • The Rising Trends of Solenoid Valves
    The Rising Trends of Solenoid Valves Mar 15, 2020
    The increasing usage of solenoid valve mean a rising future of it. Today, we will discuss why it become more and more popular.   Firstly, the introduction of environmental protection and sustainable development policy applied to industry give rise to the energy-saving concept, which is in line with the developing standards of solenoid valves-saving resources like water, energy and materials.   Second, the solenoid valves are designed to consume less energy and reduce energy loss due to flow resistance. This is the development direction of valve industry. Thus, the electric equipment is widely used in energy-saving industry. You can use consume less energy by upgrading its structure and choosing the low-power & low-noise device. On the premise of the two reasons mentioned above, we should invest more energy and money on the research, innovation and development of solenoid valves and make it play a great role in high-tech industry.
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  • What is the merit and demerit of cast valves?
    What is the merit and demerit of cast valves? Mar 08, 2020
    Casting method are widely used in valve industry. In this article, we will discuss the merits and demerits of cast steel valve.   Merit 1. Cast steel valves are made from liquid metal, thus it is more flexible in size and shape, even in complex shape. 2. There is a great variety in terms of material and its chemical composition. Thus, alloy steel valves are often made of casting method. 3. The less complicated and expensive process leads to its wide availability. 4. Cast steel valves have a contoured shape with round edges. This makes them easy to install even in small spaces and pipelines.   Demerit 1. Some material is lost when melting. The liquid is then reworked as it is put into and removed from molds. The overall process will generate lots of material waste. 2. There can be some impurities like cracks and voids during its solidifying process. This will lead to a lower mechanical property. 3. The heat treatments can alter the micro-structure of the castings after welding. This results in higher creep and lower hardness of the valve. Rigorous inspection is required to make sure the valve has retained its strength and creep resistance after being welded.
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  • The Differences between Plug Valve and Ball Valve
    The Differences between Plug Valve and Ball Valve Feb 21, 2020
    The plug valve is a relatively old type of valve, including sleeved plug valve,lubricated plug valve and multi way plug valve. It relies on the plug body to rotate around the center line of the valve body to achieve the purpose of opening and closing. The function of the plug valve is generally used to cut off, distribute and change the medium flow direction. The plug valve has a simple structure; the external dimensions are small; only 90% of the fluid resistance is required during operation. It is widely used, especially in low pressure, small diameter and medium temperature. The disadvantages of the plug valve are that the switch is laborious, the sealing surface is easy to wear, and it is easy to get stuck at high temperature and pressure, which is not suitable for regulating the flow. The ball valve is evolved from a plug valve. Its opening and closing member is a ball. The ball is rotated 90 degrees around the axis of the valve stem to achieve the purpose of opening and closing. It is mainly used to cut, distribute and change the flow of the medium Orientation, the ball valve designed as a V-shaped opening also has a good flow adjustment function. When used for shut-off, the plug valve has a slightly better adjustment capacity than the ball valve, but has limited advantages. Although the plug valve has a sealing surface much larger than the ball valve, the sealing effect is good, but it also brings the disadvantage of too much torque and insufficient flexibility. Due to the influence of the weight of the cock, the conventional positive cock structure is difficult to achieve a large caliber. If you want to use a large-size valve, you must use an inverted cock structure, that is, the cock has its head pointing down. This inevitably reduces the sealing effect under the action of gravity. It has to be sealed by grease injection. It is used for storage and transportation of natural gas and oil, but cannot be used in other industries, because grease will contaminate the medium. Although the ball valve's sealing effect is slightly poor in theory, it can be made into a large caliber. With the improvement of processing accuracy and sealing material, the ball valve's sealing effect can already meet the actual application requirements, and the application range is wider. When used for adjustment, there is not much difference between the two, and appropriate holes can be made in the rotating body for adjustment. Therefore, the general plug valve is used in occasions with higher sealing requirements, but the diameter is generally smaller, and the ball valve can be applied to more and more extensive industrial occasions.
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