Summary of college students' internship work
I have been away from school for a while, and I always think of my former classmates and buddies, remembering the time we spent together, but now everyone has gone their separate ways. I seem to be a lucky one. When I arrived at CSIC 388 Factory and worked as an assembly fitter, I finally found out that social life would be so cruel and so hard.
When I walked out of the campus, I thought I could breathe the so-called social air, but I felt that it was not easy in the job search process. I bumped into the wall, I was disappointed, I hoped, I applied again and again, and I was completely hurt again. I finally accepted it. Finally, I was touched by God. I came to the 388 factory and worked as a fitter. Think about it. During the internship at the school, we were grinding iron at that time. After coming here, I thought that it would be the same as before, and would ask us to grind iron. But after seeing the master, he told me that I would become an assembly fitter," Assembly fitter" I have a little reaction, but the master seems to see this too. He patiently told me what the assembly fitter is, how to be an assembly fitter, how to make an assembly fitter just started me. The mood is still full of doubts. What is puzzled is that we learn the molds, how can we do the work of the cylinder assembly! But now I think about it, I have learned a lot of knowledge, and some things can benefit me for life. How valuable is this! The fitter is the oldest metalworking technology in machinery manufacturing. After the 19th century, the development and popularization of various machine tools, although gradually making most of the pliers work mechanized and automated, but in the mechanical manufacturing process, the fitter is still the basic technology widely used, the reason is: scribing, scraping, grinding And mechanical assembly and other pliers work, so far no suitable mechanized equipment can be replaced; some of the most sophisticated models, molds, measuring tools and mating surfaces, still need to rely on the craftsmanship of the workers for precision processing; in a small batch production, repair In the case of work or lack of equipment conditions, it is still an economical and practical method to use the fitter to make certain parts. The quality and efficiency of the work of the pliers is largely determined by the skill and proficiency of the operator. According to the professional nature, the fitter is divided into ordinary fitter, lined fitter, mold fitter, scraper fitter, assembly fitter, machine repair fitter and pipe fitter.
From the safety education, the use of action essentials and tools to the practical operation of picking up tools such as sickles, this is undoubtedly a process of combining theory with practice. Some things are to be explored by themselves, and some things are to be found in theory for practical use. From the beginning of the polishing plane, I learned that it is not so simple to do a good job, to verify it with reality. It’s not necessarily true; it reminds me of why the school wants us to come here for an internship. It’s for us to know how valuable it is to learn, to learn and polish the plane, to be the best in the spirit, and to make us realize The importance of hands-on. It’s just not enough to learn the theory. It’s not enough. Without practical experience, you can’t find your own hands-on ability. This requires a combination of theory and practice. More cooperation between the mind and the hands is needed.
From plane polishing to scribing and dot-punching; from trimming shapes to drilling holes; from reaming to tapping, what I learned at each step is something that others can't take.
The contents of the fitter are for scribing, boring, boring, grinding, drilling, reaming, reaming, tapping, and so on. Understand the construction of the file; classification, selection, boring posture, boring method and quality inspection. And what I have to do is to deal with the operation and assembly of the valve. Here are some of my work: The problem that often occurs with the regulating valve is the jam, which often occurs in the new commissioning system and the initial operation of the overhaul, due to the welding slag in the pipeline. The rust, etc. cause blockage at the throttle opening and the guiding part to make the medium flow poorly, or the packing in the regulating valve over-tightening is too tight, resulting in an increase in frictional force, resulting in a small signal not moving and a large signal moving too much.
Trouble-shooting: The sub-line or regulating valve can be quickly opened and closed to allow dirt to be washed away from the secondary line or the regulating valve. Another method is to clamp the valve stem with a pipe wrench. When the signal pressure is applied, the valve stem is rotated forward and backward to allow the spool to flash past the card. If not, increase the air supply pressure and increase the drive power to move up and down several times to solve the problem. If it still does not work, it needs to be dismantled.
There are leaks, leaks are divided into
1. The valve is leaking and the length of the valve stem is not suitable. The valve is open and the valve stem is too long. The distance between the valve stem and the valve seat is not enough, resulting in a tight seal and internal leakage. Similarly, the valve stem of the gas shut-off valve is too short, resulting in a gap between the valve core and the valve seat, which cannot be fully contacted, resulting in a tight seal and internal leakage.
Solution: The valve stem should be shortened so that the length of the regulator is appropriate so that it is no longer leaking.
2. The packing leaks. After the packing is loaded into the stuffing box, axial pressure is applied to the packing by the gland. Due to the plasticity of the packing, it creates a radial force and is in intimate contact with the valve stem, but this contact is not very uniform. Some parts are loosely contacted, some parts are tightly contacted, and some parts are not in contact. During the use of the regulating valve, there is relative movement between the valve stem and the packing. This movement is called axial movement. In the course of use, with the influence of high temperature, high pressure and high permeability fluid medium, the control valve stuffing box is also a part with more leakage. The main cause of the leakage of the packing is the interface leakage, and leakage also occurs for the textile packing. The interface leakage between the valve stem and the packing is caused by the gradual attenuation of the contact pressure of the packing, the aging of the packing itself, etc., and the pressure medium leaks outward along the contact gap between the packing and the valve stem.
Solution: In order to facilitate the filling of the packing, chamfer the top of the stuffing box and place a metal guard ring with a small erosion-resistant gap at the bottom of the stuffing box to prevent the packing from being pushed out by the medium pressure. The metal surfaces of the parts of the stuffing box and the contact part of the packing are finished to improve the surface finish and reduce the wear of the packing. The filler is made of flexible graphite, because it has good air tightness, low friction, small change after long-term use, small wear loss, easy maintenance, no friction change after the gland bolt is retightened, pressure resistance and heat resistance. Good, free from internal media, and pitting or corrosion of metals in contact with the stem and stuffing box. In this way, the sealing of the stem packing box is effectively protected, and the reliability and long-term sealing of the packing are ensured.
3. The valve core and valve seat are deformed and leaked. The main cause of core and seat leakage is the increase in corrosion due to casting or forging defects in the production process of the regulating valve. The passage of the corrosive medium and the flushing of the fluid medium can also cause leakage of the regulating valve. Corrosion mainly exists in the form of erosion or cavitation. When the corrosive medium passes through the regulating valve, it will cause erosion and impact on the valve core and the valve seat material, and the valve core and the valve seat will be elliptical or other shapes. As time passes, the valve core and the valve seat will not be caused. Matching, there is a gap, and the leak is not strict.
Solution: The key is to select the quality of the valve core and valve seat, and the quality is off. Choose corrosion-resistant materials and resolutely eliminate defects in products such as pitting and trachoma. If the valve core and the valve seat are not too deformed, they can be ground through fine sandpaper to eliminate the marks and improve the sealing finish to improve the sealing performance. If the damage is serious, replace the valve with a new one.
In addition, it is oscillating. The reason for the oscillation is that the spring stiffness of the regulating valve is insufficient, and the output signal of the regulating valve is unstable and rapidly changes, which may cause the regulating valve to oscillate. It is also said that the frequency of the valve selection is the same as the system frequency or the pipe and the base are vibrated violently, so that the regulating valve vibrates accordingly. Improper selection, the valve operates at a small opening degree, there is a sharp flow resistance, flow rate, pressure changes, when the valve stiffness is exceeded, the stability is deteriorated, and when it is severe, oscillation occurs.
Solution: Since the cause of the oscillation is multi-faceted, the specific problem is analyzed in detail. A slight vibration to the vibration can be added to eliminate the stiffness. If a large stiffness spring is used, the piston is used to perform the structure. Vibrating vibration of pipes and pedestals eliminates vibration interference by increasing support; the frequency of valve selection is the same as the system frequency, and valves of different structures are replaced; the oscillation caused by working at small opening degree is the selection of improper flow capacity c value. It is necessary to re-select the flow capacity c value is small or use the split control or the mother valve to overcome the small opening of the regulating valve.
It also has a valve positioner failure, which is divided into
1. The general positioner works by the mechanical force balance principle, that is, the nozzle baffle technology, mainly has the following fault types:
1) Due to the mechanical force balance principle, there are many movable parts, which are easily affected by temperature and vibration, causing fluctuations of the regulating valve;
2) Using the nozzle baffle technology, since the nozzle hole is small, it is easily blocked by dust or an unclean gas source, and the positioner cannot work normally;
3) Using the balance principle of force, the spring coefficient of the spring changes under the harsh scene, causing the nonlinearity of the regulating valve to cause the control quality to drop.
2. The intelligent positioner is composed of a microprocessor, a/d, d/a converter and other components, and its working principle is completely different from that of the ordinary positioner. The comparison between the given value and the actual value is purely an electric signal and is no longer a force balance. Therefore, the disadvantage of the force balance of the conventional positioner can be overcome. However, when used in emergency parking, such as emergency shut-off valves, emergency venting valves, etc. These valves are required to be stationary at a certain location and require reliable action only in the event of an emergency. Staying in a certain position for a long time is a dangerous situation in which the electrical converter is out of control and the small signal does not move. In addition, because the position sensing potentiometer used for the valve works in the field, the resistance value is easy to change, causing the small signal to not operate, and the large signal is fully open. Therefore, in order to ensure the reliability and availability of smart positioners, they must be tested frequently.
By analyzing the cause of the failure of the regulating valve and adopting appropriate treatment and improvement methods, the utilization rate of the regulating valve will be greatly improved, the instrument failure rate will be reduced, and the production efficiency and economic efficiency of the process and the reduction of energy consumption will play an important role. , can effectively improve the quality of the adjustment system to ensure long-term operation of the production equipment.
After a period of time, I have been able to work freely. Now I am full of confidence in my future work. I believe that I will do something.
The above is my general business of internships during this period of time. I hope the teacher will criticize and correct me. Special note: This article is carefully compiled by the first Fan Wenwang editor for your reference.
When I walked out of the campus, I thought I could breathe the so-called social air, but I felt that it was not easy in the job search process. I bumped into the wall, I was disappointed, I hoped, I applied again and again, and I was completely hurt again. I finally accepted it. Finally, I was touched by God. I came to the 388 factory and worked as a fitter. Think about it. During the internship at the school, we were grinding iron at that time. After coming here, I thought that it would be the same as before, and would ask us to grind iron. But after seeing the master, he told me that I would become an assembly fitter," Assembly fitter" I have a little reaction, but the master seems to see this too. He patiently told me what the assembly fitter is, how to be an assembly fitter, how to make an assembly fitter just started me. The mood is still full of doubts. What is puzzled is that we learn the molds, how can we do the work of the cylinder assembly! But now I think about it, I have learned a lot of knowledge, and some things can benefit me for life. How valuable is this! The fitter is the oldest metalworking technology in machinery manufacturing. After the 19th century, the development and popularization of various machine tools, although gradually making most of the pliers work mechanized and automated, but in the mechanical manufacturing process, the fitter is still the basic technology widely used, the reason is: scribing, scraping, grinding And mechanical assembly and other pliers work, so far no suitable mechanized equipment can be replaced; some of the most sophisticated models, molds, measuring tools and mating surfaces, still need to rely on the craftsmanship of the workers for precision processing; in a small batch production, repair In the case of work or lack of equipment conditions, it is still an economical and practical method to use the fitter to make certain parts. The quality and efficiency of the work of the pliers is largely determined by the skill and proficiency of the operator. According to the professional nature, the fitter is divided into ordinary fitter, lined fitter, mold fitter, scraper fitter, assembly fitter, machine repair fitter and pipe fitter.
From the safety education, the use of action essentials and tools to the practical operation of picking up tools such as sickles, this is undoubtedly a process of combining theory with practice. Some things are to be explored by themselves, and some things are to be found in theory for practical use. From the beginning of the polishing plane, I learned that it is not so simple to do a good job, to verify it with reality. It’s not necessarily true; it reminds me of why the school wants us to come here for an internship. It’s for us to know how valuable it is to learn, to learn and polish the plane, to be the best in the spirit, and to make us realize The importance of hands-on. It’s just not enough to learn the theory. It’s not enough. Without practical experience, you can’t find your own hands-on ability. This requires a combination of theory and practice. More cooperation between the mind and the hands is needed.
From plane polishing to scribing and dot-punching; from trimming shapes to drilling holes; from reaming to tapping, what I learned at each step is something that others can't take.
The contents of the fitter are for scribing, boring, boring, grinding, drilling, reaming, reaming, tapping, and so on. Understand the construction of the file; classification, selection, boring posture, boring method and quality inspection. And what I have to do is to deal with the operation and assembly of the valve. Here are some of my work: The problem that often occurs with the regulating valve is the jam, which often occurs in the new commissioning system and the initial operation of the overhaul, due to the welding slag in the pipeline. The rust, etc. cause blockage at the throttle opening and the guiding part to make the medium flow poorly, or the packing in the regulating valve over-tightening is too tight, resulting in an increase in frictional force, resulting in a small signal not moving and a large signal moving too much.
Trouble-shooting: The sub-line or regulating valve can be quickly opened and closed to allow dirt to be washed away from the secondary line or the regulating valve. Another method is to clamp the valve stem with a pipe wrench. When the signal pressure is applied, the valve stem is rotated forward and backward to allow the spool to flash past the card. If not, increase the air supply pressure and increase the drive power to move up and down several times to solve the problem. If it still does not work, it needs to be dismantled.
There are leaks, leaks are divided into
1. The valve is leaking and the length of the valve stem is not suitable. The valve is open and the valve stem is too long. The distance between the valve stem and the valve seat is not enough, resulting in a tight seal and internal leakage. Similarly, the valve stem of the gas shut-off valve is too short, resulting in a gap between the valve core and the valve seat, which cannot be fully contacted, resulting in a tight seal and internal leakage.
Solution: The valve stem should be shortened so that the length of the regulator is appropriate so that it is no longer leaking.
2. The packing leaks. After the packing is loaded into the stuffing box, axial pressure is applied to the packing by the gland. Due to the plasticity of the packing, it creates a radial force and is in intimate contact with the valve stem, but this contact is not very uniform. Some parts are loosely contacted, some parts are tightly contacted, and some parts are not in contact. During the use of the regulating valve, there is relative movement between the valve stem and the packing. This movement is called axial movement. In the course of use, with the influence of high temperature, high pressure and high permeability fluid medium, the control valve stuffing box is also a part with more leakage. The main cause of the leakage of the packing is the interface leakage, and leakage also occurs for the textile packing. The interface leakage between the valve stem and the packing is caused by the gradual attenuation of the contact pressure of the packing, the aging of the packing itself, etc., and the pressure medium leaks outward along the contact gap between the packing and the valve stem.
Solution: In order to facilitate the filling of the packing, chamfer the top of the stuffing box and place a metal guard ring with a small erosion-resistant gap at the bottom of the stuffing box to prevent the packing from being pushed out by the medium pressure. The metal surfaces of the parts of the stuffing box and the contact part of the packing are finished to improve the surface finish and reduce the wear of the packing. The filler is made of flexible graphite, because it has good air tightness, low friction, small change after long-term use, small wear loss, easy maintenance, no friction change after the gland bolt is retightened, pressure resistance and heat resistance. Good, free from internal media, and pitting or corrosion of metals in contact with the stem and stuffing box. In this way, the sealing of the stem packing box is effectively protected, and the reliability and long-term sealing of the packing are ensured.
3. The valve core and valve seat are deformed and leaked. The main cause of core and seat leakage is the increase in corrosion due to casting or forging defects in the production process of the regulating valve. The passage of the corrosive medium and the flushing of the fluid medium can also cause leakage of the regulating valve. Corrosion mainly exists in the form of erosion or cavitation. When the corrosive medium passes through the regulating valve, it will cause erosion and impact on the valve core and the valve seat material, and the valve core and the valve seat will be elliptical or other shapes. As time passes, the valve core and the valve seat will not be caused. Matching, there is a gap, and the leak is not strict.
Solution: The key is to select the quality of the valve core and valve seat, and the quality is off. Choose corrosion-resistant materials and resolutely eliminate defects in products such as pitting and trachoma. If the valve core and the valve seat are not too deformed, they can be ground through fine sandpaper to eliminate the marks and improve the sealing finish to improve the sealing performance. If the damage is serious, replace the valve with a new one.
In addition, it is oscillating. The reason for the oscillation is that the spring stiffness of the regulating valve is insufficient, and the output signal of the regulating valve is unstable and rapidly changes, which may cause the regulating valve to oscillate. It is also said that the frequency of the valve selection is the same as the system frequency or the pipe and the base are vibrated violently, so that the regulating valve vibrates accordingly. Improper selection, the valve operates at a small opening degree, there is a sharp flow resistance, flow rate, pressure changes, when the valve stiffness is exceeded, the stability is deteriorated, and when it is severe, oscillation occurs.
Solution: Since the cause of the oscillation is multi-faceted, the specific problem is analyzed in detail. A slight vibration to the vibration can be added to eliminate the stiffness. If a large stiffness spring is used, the piston is used to perform the structure. Vibrating vibration of pipes and pedestals eliminates vibration interference by increasing support; the frequency of valve selection is the same as the system frequency, and valves of different structures are replaced; the oscillation caused by working at small opening degree is the selection of improper flow capacity c value. It is necessary to re-select the flow capacity c value is small or use the split control or the mother valve to overcome the small opening of the regulating valve.
It also has a valve positioner failure, which is divided into
1. The general positioner works by the mechanical force balance principle, that is, the nozzle baffle technology, mainly has the following fault types:
1) Due to the mechanical force balance principle, there are many movable parts, which are easily affected by temperature and vibration, causing fluctuations of the regulating valve;
2) Using the nozzle baffle technology, since the nozzle hole is small, it is easily blocked by dust or an unclean gas source, and the positioner cannot work normally;
3) Using the balance principle of force, the spring coefficient of the spring changes under the harsh scene, causing the nonlinearity of the regulating valve to cause the control quality to drop.
2. The intelligent positioner is composed of a microprocessor, a/d, d/a converter and other components, and its working principle is completely different from that of the ordinary positioner. The comparison between the given value and the actual value is purely an electric signal and is no longer a force balance. Therefore, the disadvantage of the force balance of the conventional positioner can be overcome. However, when used in emergency parking, such as emergency shut-off valves, emergency venting valves, etc. These valves are required to be stationary at a certain location and require reliable action only in the event of an emergency. Staying in a certain position for a long time is a dangerous situation in which the electrical converter is out of control and the small signal does not move. In addition, because the position sensing potentiometer used for the valve works in the field, the resistance value is easy to change, causing the small signal to not operate, and the large signal is fully open. Therefore, in order to ensure the reliability and availability of smart positioners, they must be tested frequently.
By analyzing the cause of the failure of the regulating valve and adopting appropriate treatment and improvement methods, the utilization rate of the regulating valve will be greatly improved, the instrument failure rate will be reduced, and the production efficiency and economic efficiency of the process and the reduction of energy consumption will play an important role. , can effectively improve the quality of the adjustment system to ensure long-term operation of the production equipment.
After a period of time, I have been able to work freely. Now I am full of confidence in my future work. I believe that I will do something.
The above is my general business of internships during this period of time. I hope the teacher will criticize and correct me. Special note: This article is carefully compiled by the first Fan Wenwang editor for your reference.
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