As an actuator, control valve always plays a very important role in the production process of process industry. The performance of control valve directly affects the output and unqualified rate of process, even normal production. With the development of process technology and control technology, the economic scale of process industry is becoming larger and larger, and the processing capacity is increasing day by day, which makes even if the percentage of valve performance improvement is small, great benefits can be obtained. Based on this situation, the process industry for the control valve before getting higher and higher, coupled with the advantages of the rotary valve itself, which makes the rotary valve than the traditional valve to obtain more and more applications.
Rotary valve features: the valve is usually divided into two categories and rotary straight program. Straight travel valves allow or shut off flow through a linearly moving component such as a gate. Straight type valve has a stop valve, gate valve. Diaphragm valves, etc. Rotary valves allow or shut off flow through a rotating member. Rotating parts can rotate 90 rotary valve called 1/4 rotary valve. Sometimes the classification of 1/4 rotary valves can be expanded to rotary valves with a rotation angle of less than 270. By definition, it can be seen that a rotary valve is a rotary valve that changes the position of the valve from open to critical by rotating a rotating member such as a rotating baffle 90. Rotary valves generally have the following characteristics. Adjustable range is the key, the adjustable range of the rotary valve is about 150:1, corresponding to the adjustable range of the cut-off valve is 30:1, that is to say, the rotary valve can provide 5 times the wide adjustable range. For example, in a large flow rate of 1000 liters/min, the cut-off valve can effectively reduce the flow rate to 30 liters/min, while the rotary valve can adjust the flow rate to 10 liters/min. The more accurate the control flow rate of the key valve, the better the repeatability in the process, which directly reduces the unqualified products in the process industry.
Two features of the eccentric rotary valve enhance its adjustable range. The first is its orifice plate design, the eccentric is an effective 1/4 of the circle, the eccentric spool is V-shaped, while the traditional spool is circular, when the eccentric rotary valve is off, its small V-shaped makes the formation of very precise control at low flow, for large flow, it almost opens the valve to almost the same diameter as the pipe. The second feature is the implementation of the machine's stroke rotary valve actuator with a certain stroke of the film method and cylinder two. 1, the stroke of the stop valve is about 3/4~7/8, while the stroke of the rotary valve is more than 2, for any other size valve. The greater the stroke of the input end, the better the control at the working end. The high adjustable ratio control valve provides accurate proportioning according to the requirements of the formula, regardless of the size of the flow of each flow path. The traditional linear or recommend valve is no longer suitable for such a task. The rotary valve can improve the strict cut-off standard, thus improving the cost-effectiveness index. The metal valve seat and the village made of special materials can prolong the service life of the valve, improve the performance of the valve, and the design of simple rotating structure, the maintenance workload can be reduced. Reduce the production cost of the owner. Cut off tightly.
The shaft of the straight stroke valve is the valve stem in and out of the valve body, and each cycle brings out the product. It is difficult to avoid leakage for straight stroke design. It can bring unwanted products into the production process system and generate large and unacceptable external leakage of factory volatility. The rotary design of rotary valve does not exist in nature. This problem, because this valve uses a low-lag, high-thrust cylinder actuator, which can provide more accurate and higher stability than other forms of actuators, there are metal seats that can provide long-term tight cut-off.
From the flow capacity of large size small point of view: the flow of the straight stroke valve is the installation method of the pipeline flow capacity of the fraction, improve the flow capacity of the method is to improve the size of the straight stroke valve, usually may be larger than the pipeline. The capacity of the rotary valve is about the same size of the straight stroke valve 2~3 times, rotary valve can be used to increase the amount of blending without changing the size of the feed line, can greatly reduce costs, for this reason, part of the rotary valve has been designed to replace the valve flange face flange connection form, and is equipped with connecting bolts, this kind of valve is even cheaper than their replacement valve.
Anti-cavitation: In the process industry, throttling can cause a lot of cavitation. Cavitation may damage the pipeline and produce unacceptable noise levels. At the same time, it can also disturb the metering system and cause unclear or unreliable readings. The rotary valve has a solid design, which greatly reduces the valve action failure caused by hammer phenomenon. At the same time, the valve core can absorb some excess energy, significantly reduces cavitation and related problems. No external leakage; the standard rotary valve is 100 times better than the external leakage of the standard shut-off valve design. The movement of the stem of the shut-off valve pulls dust out and brings sand into the valve, thereby damaging the graphite packing. In the rotary valve does not make any in and out of the movement, and for the rotation movement, so as not to damage the packing, to avoid the external leakage. Maintenance costs and spare parts; metal seat rotary valves are much less spare parts than globe valves, and maintenance is usually easier.
Type of rotary valve: according to the type of classification; rotary valve in accordance with the type of classification there are three types, butterfly valve, ball valve and plunger valve. Butterfly valve is through the baffle or blade to rotate a certain angle to control the direction of flow. The baffle or blade looks a bit like a butterfly. Butterfly valve can play the role of cut-off or recommend, adapted to slurry or with solid suspension of the fluid. The valve core of the ball valve is a spherical body with a round hole. When the valve is in the open position, the fluid is allowed to flow through, and the spherical body is turned 90 to cut off the flow. Ball valve can cut off and adjust the role, its pressure drop is small, suitable for viscous and corrosive fluids, slurry low temperature fluid. Ball valves can also be used for high temperature, high pressure fluids. The spool of the plunger valve is a conical or cylindrical plunger with a round hole in the middle. When the plunger hole and the flow direction are consistent, the fluid can pass through. When the plunger rotates to any 90, the exposure is cut off. Plunger valves are usually used for on/off control.
According to the mode of operation classification: rotary valve in accordance with the mode of operation classification has the following types: manual valve, automatic valve and control valve. The manual rotary valve is operated by hand, and is operated by a manual actuator such as a hand lever, gear, handwheel, etc., and includes a component that can rotate 90 degrees. The actuator opens and closes the valve by operating the valve stem and the control element. The automatic rotary valve includes an automatic actuator that uses external energy to automatically control or remotely control the valve switch. The following situations should generally choose automatic valve; large valve (such as more than 8, the valve)/manual operation is difficult to valve, in toxic or other harsh environment is impossible