Abstract: Large-diameter electric and pneumatic valves are one of the frequently used valves in the chemical industry. Some valves have a size exceeding DN600. They remain normally open or normally closed during the production process. After long-term use, the media or parts are rusted. It will cause the sealing shaft to jam, and the actuator will not be able to drive normally. Due to production constraints, it can not be effectively processed. The cost of replacing the actuator and the single unit is high. This paper takes the DN1200 caliber triple eccentric butterfly valve of our factory as an example. Analysis of the situation before and after the transformation, I hope to serve as a reference for readers.
Key words: butterfly valve sealing shaft actuator sliding bearing Introduction: Butterfly valve is one of the fastest growing valve quality in the past ten years. It has a wide application range, wide variety and specifications, and high pressure, large diameter, high sealing, etc. In the direction of development, there are mainly rubber soft seals, double eccentricity and triple eccentricity. Due to the low price of the valve body, the chemical industry is currently used in large-diameter pipelines, and most of them are clip-on and flange-type installations. Due to the short diameter, after long-term use, it is difficult to dismantle and repair the large-diameter butterfly valve after being squeezed by the pipeline. The air outlet unit compressor outlet venting butterfly valve, the diameter is DN1200, suspended installation, after the occurrence of the jam problem, It has not been effectively treated, and it has been considered to replace this actuator with a larger torque before the failure to reduce the resistance. However, due to the high cost, it has not been implemented.
I. Valve Overview Our factory air separation unit compressor outlet vent butterfly valve, caliber DN1200, suspended installation, 12 years low start operation, Yang repair electric actuator, original design torque 4000, in the 15 years of high load operation, remote Can not effectively drive the situation, but the manual can be normally switched, judged that the design principle is too small, then purchased an Autodesk actuator to increase the torque to 6000, but in the 17 years there is a remote jam phenomenon, due to the system The car has not been inspected. When the overhaul was carried out in September of 17 years, the valve was removed for external repair. During the overhaul, it was found that the upper and lower shafts of the valve body were not obviously worn. After grinding and replacing the upper and lower sealing bushings, the upper line was installed, the debugging was normal, and then the car was driven. During the period of the card, the maintenance unit also judged that the valve actuator selection was small. Before the resistance reduction scheme was formed, the actuator with larger torque was considered to solve the problem, but because of The high torque actuator is expensive (about 100,000 yuan) and has not been implemented. After repeated discussion and inquiries about the problems of other valves manufacturers, this valve has no effective advice.
In March of 18, combined with the actual operating conditions, we found that the valve has been in a certain degree of opening during normal operation, and the long-term constant, the resistance of the valve operation is mainly concentrated in the pipeline pressure difference, the upper circumferential seal ring, the next week. After three careful analysis, it is known that the maximum resistance of the valve should be the fixed seal ring of the lower shaft. This position not only bears the weight of the valve itself, but also the main rotating shaft when the valve is operating. The shaft is long. After the time is running, there must be rust, which increases the driving force of the valve. Therefore, a structure for reducing the friction of the electric valve sealing shaft and reducing the torque of the electric valve is provided, and an improved form that avoids the influence of the valve switch jam on the operation of the system is born.
Second, the transformation concept is mainly implemented by the following schemes. One is to change the existing carbon steel coupling to stainless steel to reduce the rust and friction during use; one is to process the lower shaft and reduce the running resistance of the hard seal. .
When we removed and replaced the original carbon steel shaft, it was found that due to the corrosion of the whole shaft, the connected valve body part was extremely difficult to remove. If it was forcibly removed, it would inevitably cause damage to the entire valve body. Due to the short maintenance period, there was not enough time. To make a new valve body, this program was cancelled.
According to the report study, the upper and lower hard seal drive shafts of the valve body were changed to the bearing sliding form to reduce the driving force of the electric actuator and was approved for implementation. After combining the driving characteristics of most of our electric valves, we finally adopted the form of increasing the sliding bearing to reduce the movement resistance, mainly in the following aspects: 1. Re-machining the fixed shaft, using the lathe for processing, so that it can Lower the sliding bearing. 2. Machining the lower shaft of the valve, replacing the original sealed steel ring with a graphite ring, and changing the sealing form of the base. 3. The weighing and fixing method is changed to the form of a flat bearing, and the rotating friction is changed from a hard-sealed steel ring to a sliding bearing. According to the research of the branch, the upper and lower hard seal drive shafts of the valve body were changed to the bearing sliding form to reduce the driving force of the electric actuator. The utility model has the advantages of simple structure, convenient installation and maintenance, and can effectively reduce the friction of the electric valve sealing shaft, reduce the electric valve torque, reduce the equipment maintenance cost and the valve investment, avoid the influence on the system operation, and improve the competition of the enterprise. force.
Third, the effect achieved by the maintenance team and full communication, combined with the process conditions and the operating characteristics of the electric valve, after 4 days, the final completion of the sliding bearing modification work, and smooth installation and commissioning, and an operator using a wrench The valve body can be rotated, which is greatly improved compared with the previous one. After 4 times of system start and stop, the remote control is not in the process of production during the production period, and the operation condition is good. The main structure is shown in Figure 1:
In the picture: 1 graphite packing, 2 sliding bearings, 3 flat bearing lower end caps, 4 plane bearings, 5 flat bearing upper end caps, 6 bearing cap sealing faces, 7 electric valve lower sealing shafts, 8 flange bolts, 9 lower seals Shaft flange cover IV. Summary The correct choice of valve form is essential for ensuring safe production of the device, improving valve life and improving long-term stable operation. Especially when selecting a larger-aperture valve, it should be carefully considered. Although the butterfly valve is simple in structure, easy to maintain, and the production cost is small, the maintenance strategy after the problem is worthy of our consideration. Daily maintenance is particularly important. Proper lubrication and regular maintenance are the key to long-life operation of the valve.
At present, large-diameter butterfly valves of chemical units appear to be stuck after long-term use. Most of the selected demolition and disassembly repairs are more like the previous ones. The driving force of equipment is constantly increasing, and the cost of maintenance and equipment renewal is high. For enterprises, it is not conducive to long-term stable operation, and it is impossible to effectively plan maintenance and cost control. It has been proved by practice that some butterfly valves and ball valves with larger diameters are stuck, and the drive is not flexible, such as long operation cycle. When the medium is stable and the maintenance cost is high, the repair and improvement can be carried out through the modified form of this paper, which can reduce more maintenance capital consumption for more enterprises.
Key words: butterfly valve sealing shaft actuator sliding bearing Introduction: Butterfly valve is one of the fastest growing valve quality in the past ten years. It has a wide application range, wide variety and specifications, and high pressure, large diameter, high sealing, etc. In the direction of development, there are mainly rubber soft seals, double eccentricity and triple eccentricity. Due to the low price of the valve body, the chemical industry is currently used in large-diameter pipelines, and most of them are clip-on and flange-type installations. Due to the short diameter, after long-term use, it is difficult to dismantle and repair the large-diameter butterfly valve after being squeezed by the pipeline. The air outlet unit compressor outlet venting butterfly valve, the diameter is DN1200, suspended installation, after the occurrence of the jam problem, It has not been effectively treated, and it has been considered to replace this actuator with a larger torque before the failure to reduce the resistance. However, due to the high cost, it has not been implemented.
I. Valve Overview Our factory air separation unit compressor outlet vent butterfly valve, caliber DN1200, suspended installation, 12 years low start operation, Yang repair electric actuator, original design torque 4000, in the 15 years of high load operation, remote Can not effectively drive the situation, but the manual can be normally switched, judged that the design principle is too small, then purchased an Autodesk actuator to increase the torque to 6000, but in the 17 years there is a remote jam phenomenon, due to the system The car has not been inspected. When the overhaul was carried out in September of 17 years, the valve was removed for external repair. During the overhaul, it was found that the upper and lower shafts of the valve body were not obviously worn. After grinding and replacing the upper and lower sealing bushings, the upper line was installed, the debugging was normal, and then the car was driven. During the period of the card, the maintenance unit also judged that the valve actuator selection was small. Before the resistance reduction scheme was formed, the actuator with larger torque was considered to solve the problem, but because of The high torque actuator is expensive (about 100,000 yuan) and has not been implemented. After repeated discussion and inquiries about the problems of other valves manufacturers, this valve has no effective advice.
In March of 18, combined with the actual operating conditions, we found that the valve has been in a certain degree of opening during normal operation, and the long-term constant, the resistance of the valve operation is mainly concentrated in the pipeline pressure difference, the upper circumferential seal ring, the next week. After three careful analysis, it is known that the maximum resistance of the valve should be the fixed seal ring of the lower shaft. This position not only bears the weight of the valve itself, but also the main rotating shaft when the valve is operating. The shaft is long. After the time is running, there must be rust, which increases the driving force of the valve. Therefore, a structure for reducing the friction of the electric valve sealing shaft and reducing the torque of the electric valve is provided, and an improved form that avoids the influence of the valve switch jam on the operation of the system is born.
Second, the transformation concept is mainly implemented by the following schemes. One is to change the existing carbon steel coupling to stainless steel to reduce the rust and friction during use; one is to process the lower shaft and reduce the running resistance of the hard seal. .
When we removed and replaced the original carbon steel shaft, it was found that due to the corrosion of the whole shaft, the connected valve body part was extremely difficult to remove. If it was forcibly removed, it would inevitably cause damage to the entire valve body. Due to the short maintenance period, there was not enough time. To make a new valve body, this program was cancelled.
According to the report study, the upper and lower hard seal drive shafts of the valve body were changed to the bearing sliding form to reduce the driving force of the electric actuator and was approved for implementation. After combining the driving characteristics of most of our electric valves, we finally adopted the form of increasing the sliding bearing to reduce the movement resistance, mainly in the following aspects: 1. Re-machining the fixed shaft, using the lathe for processing, so that it can Lower the sliding bearing. 2. Machining the lower shaft of the valve, replacing the original sealed steel ring with a graphite ring, and changing the sealing form of the base. 3. The weighing and fixing method is changed to the form of a flat bearing, and the rotating friction is changed from a hard-sealed steel ring to a sliding bearing. According to the research of the branch, the upper and lower hard seal drive shafts of the valve body were changed to the bearing sliding form to reduce the driving force of the electric actuator. The utility model has the advantages of simple structure, convenient installation and maintenance, and can effectively reduce the friction of the electric valve sealing shaft, reduce the electric valve torque, reduce the equipment maintenance cost and the valve investment, avoid the influence on the system operation, and improve the competition of the enterprise. force.
Third, the effect achieved by the maintenance team and full communication, combined with the process conditions and the operating characteristics of the electric valve, after 4 days, the final completion of the sliding bearing modification work, and smooth installation and commissioning, and an operator using a wrench The valve body can be rotated, which is greatly improved compared with the previous one. After 4 times of system start and stop, the remote control is not in the process of production during the production period, and the operation condition is good. The main structure is shown in Figure 1:
In the picture: 1 graphite packing, 2 sliding bearings, 3 flat bearing lower end caps, 4 plane bearings, 5 flat bearing upper end caps, 6 bearing cap sealing faces, 7 electric valve lower sealing shafts, 8 flange bolts, 9 lower seals Shaft flange cover IV. Summary The correct choice of valve form is essential for ensuring safe production of the device, improving valve life and improving long-term stable operation. Especially when selecting a larger-aperture valve, it should be carefully considered. Although the butterfly valve is simple in structure, easy to maintain, and the production cost is small, the maintenance strategy after the problem is worthy of our consideration. Daily maintenance is particularly important. Proper lubrication and regular maintenance are the key to long-life operation of the valve.
At present, large-diameter butterfly valves of chemical units appear to be stuck after long-term use. Most of the selected demolition and disassembly repairs are more like the previous ones. The driving force of equipment is constantly increasing, and the cost of maintenance and equipment renewal is high. For enterprises, it is not conducive to long-term stable operation, and it is impossible to effectively plan maintenance and cost control. It has been proved by practice that some butterfly valves and ball valves with larger diameters are stuck, and the drive is not flexible, such as long operation cycle. When the medium is stable and the maintenance cost is high, the repair and improvement can be carried out through the modified form of this paper, which can reduce more maintenance capital consumption for more enterprises.
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