Automation--types of valves

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Types of valves 1. Gate valve Gate valve, also called gate valve, is a widely used valve. Its closing principle is that the gate sealing surface and the valve seat sealing surface are highly smooth, flat and consistent, and fit together to prevent the flow of media. The sealing effect is enhanced by relying on the mold shape of the top mold, spring or gate plate. It mainly plays a cutting role in the pipeline. Its advantages are: small fluid resistance, effortless opening and closing, can be used when the medium flows in both directions, has no directionality, the sealing surface is not easily eroded when fully open, and the structural length is short. It is not only suitable for small valves, but also for large valves. Gate valves are divided into two categories according to the valve stem thread, one is the open stem type, and the other is the concealed stem type. According to the gate structure, it can also be divided into two categories, one is parallel and the other is pattern. 2. Stop valve Stop valve, also called stop valve, is the most widely used valve. The reason why it is so popular is that the friction between the sealing surfaces during the opening and closing process is small, it is relatively durable, it has a small opening height, it is easy to manufacture, and it is easy to maintain. It is not only suitable for medium and low pressure, but also for high pressure. Its closing principle is to rely on the pressure of the valve rod to make the valve disc sealing surface and the valve seat sealing surface closely fit to prevent the flow of media. The stop valve only allows the medium to flow in one direction and is directional when installed. Its structural length is larger than that of the gate valve, and at the same time, the fluid resistance is large, and the sealing reliability is not strong during long-term operation. Globe valves are divided into three categories: straight-through, right-angle and DC inclined globe valves. 3. Butterfly valve Butterfly valve is also called butterfly valve. As the name suggests, its key components resemble a butterfly facing the wind and rotating freely. The disc of the butterfly valve is a disc that rotates around an axis in the valve seat. The size of the rotation angle is the opening and closing degree of the valve. Butterfly valves are lightweight, save material than other valves, have a simple structure, can open and close quickly, can be used for cutting and throttling, have small fluid resistance, and are labor-saving in operation. Butterfly valves can be made into large diameters. Where butterfly valves can be used, it is best not to use gate valves, because butterfly valves are more economical than gate valves and have better adjustability. Currently, butterfly valves are widely used in hot water pipelines. 4. Ball valve The working principle of the ball valve is to rely on the rotating valve to open or block the valve. Ball valves are easy to switch, small in size, can be made into large diameters, have reliable sealing, simple structure, and easy maintenance. The sealing surface and spherical surface are always in a closed state and are not easily eroded by the medium. They are widely used in various industries. Ball valves are divided into two categories, one is the floating ball type and the other is the fixed ball type. 5. Plug valve Plug valve relies on the plug body to rotate around the center line of the valve body to achieve the purpose of opening and closing. Its function is to cut off, divide the fields and change the flow direction of the medium. It has a simple structure and small dimensions, and only needs to be rotated 90 degrees during operation. , the fluid resistance is not large either. Its disadvantages are that the switch is laborious, the sealing surface is easy to wear, and it is easy to get stuck at high temperatures, so it is not suitable for regulating flow. Plug valve, also called cock, cock, and rotating valve. There are many types of it, including straight-through type, three-way type and four-way type. 6. Check valve The check valve is a valve that automatically opens and closes by the force of the fluid itself. Its function is to prevent the medium from flowing back. It has many names, such as check valve, one-way valve, one-way valve, etc. It can be divided into two categories according to structure. (1) Lift type: The valve disc moves along the vertical centerline of the valve body. There are two types of check valves: one is horizontal type, installed in horizontal pipelines, the shape of the valve body is similar to that of a stop valve, and the other is vertical type, installed in vertical pipelines. (2) Swing type: The valve disc rotates around the pin outside the seat. This type of valve is divided into single disc, double disc and multi-disc, but the principle is the same. The suction bottom valve of the water pump suction pipe is a deformation of the check valve. Its structure is the same as the above two types of check valves, except that its lower end is open to allow water to enter. 7. Pressure reducing valve A pressure reducing valve is an automatic valve that reduces the medium pressure to a certain value. Generally, the pressure behind the valve is less than 50% of the pressure in front of the valve. There are many types of pressure reducing valves, mainly including piston type and spring diaphragm type. Piston pressure reducing valve is a valve that reduces pressure through the action of a piston. The spring diaphragm pressure reducing valve relies on springs and diaphragms for pressure balance. 8. Drain valve Traps are also called steam-blocking drain valves, steam-water valves, traps, return water boxes, return water gates, etc. Its function is to automatically drain the continuously generated condensation water without letting the steam come out. There are many types of traps, including float type, float type, bell float type, pulse type, thermodynamic type, and thermal expansion type. Commonly used ones are float type, bell float type and thermodynamic type. (1) Float-type traps Float-type traps are mainly composed of valves, shafts, conduits, floats and shells. When the condensate in the equipment or pipeline enters the trap driven by steam pressure and gradually increases until it nearly fills the float, the weight of the float exceeds the buoyancy and sinks downward, causing the throttle valve to open. This allows the condensed water in the cylinder to be discharged through the conduit and valve under the action of steam pressure. When the condensate water in the float is almost exhausted, the weight of the float is reduced and it floats upward, causing the throttle valve to close and condensate water begins to accumulate in the float again. Working periodically in this way can automatically discharge condensation water and prevent steam from escaping. (2) Bell-shaped float type trap. Bell-shaped float type trap is also called bucket type trap (mainly composed of regulating valve, bucket, shell, filter device and other components. The bucket in the trap is inverted, initially in the lowered position, and the regulating valve is open. When the cold air and condensed water in the equipment or pipes enter the trap under the pressure of steam, they are immediately discharged from the regulating valve. On the one hand, when steam and a small amount of air that has not been discharged gradually fill the internal volume of the bucket, and condensate water continues to accumulate, the bucket rises due to the buoyancy generated, causing the regulating valve to close and stop discharging condensate water. On the other hand, a small part of the steam and air inside the bucket is discharged from the small hole on the top of the bucket, and most of it condenses into liquid after dissipating heat, so that the buoyancy of the bucket gradually decreases and it falls, causing the regulating valve to open and the condensed water to be discharged. Working periodically in this way can automatically discharge condensation water and prevent steam from escaping. (3) Thermodynamic Trap Thermodynamic Trap (When the condensed water in the equipment or pipeline flows into the air-blocking drain valve, the steam in the pressure transformer chamber will condense and reduce the pressure. The force on the bottom of the valve plate is greater than the force on the top, so the valve plate is lifted up. Because condensate water has a higher viscosity than steam and a lower flow rate, it is less likely to cause negative pressure between the valve plate and the valve bottom. At the same time, it is difficult for condensate water to flow into the pressure transformer chamber through the gap between the valve plate and the shell, so that the valve plate remains open and the condensate water is discharged through the annular groove. When the steam in the equipment or pipeline flows into the trap, because the steam has a lower viscosity and a higher flow rate than the condensed water, negative pressure is easily caused between the valve plate and the valve seat. At the same time, part of the steam flows into the pressure transformer chamber, so the force on the upper part of the valve plate is greater than the force on the lower part, causing the valve plate to close quickly. Working periodically in this way can not only automatically discharge condensation water, but also prevent steam from escaping. ★Collected and organized by Komatsu blog. Please indicate when reprinting★