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1, the issue put forward Industrial automation instruments, VDC pneumatic control valve is widely used in the production of a high degree of automation plays an important role in the production, but because of its simple structure is often not taken seriously. In the chemical production process in the instrument to adjust the working conditions are more complex, installed in the key process pipe on the pneumatic control valve in the event of problems, due to greater impact on the production, instrumentation maintenance staff is also a greater psychological pressure, the problem is very confused Difficult to find accurate, often thankless, but also involves the system put into operation, system security, regulatory quality, environmental pollution, etc., thus overhauling the control valve affect the process of production often occur. I plant the process of heavy alkali 5 carbonation tower cooling system uses 10 sets of pneumatic control valve into the tower cooling water, respectively, 5 sets of DC water regulating valve, 5 circulating water regulating valve. In recent years of operation, the regulator valve stem and valve gland at the leakage problem has been unable to eliminate. On the one hand, the leakage of water to the valve body surface serious corrosion, affecting the life of the valve, the floor of the process of heavy alkali pollution; the other hand, the leakage rate assessment Home Furnishing installation and maintenance company in the first class, affecting the team Construction. 2, the reasons for the leakage of regulating valve Pneumatic valve stem and body seal at the maintenance methods are as follows: First, the valve actuator and the body off, and then open the gland, remove the gasket under the gland, hook filler Letter inside the "V" type of filler, replace the new filler, and then a good gland that is overhaul. This maintenance time, generally only maintain two to six months, some even after the leak occurred in the repair situation, and the gland can not be too tight pressure, otherwise it will affect the valve automatically adjust. In the initial repair generally add 4 to 6 laps "V" -shaped filler, then gradually weakened due to the spring tension, the added "V" -shaped filler gradually increased, and now has increased to a dozen laps. From the above analysis, the main reason for poor sealing is due to the stuffing box spring loses its elasticity due to rust, and we use the PTFE packing harder, the pressure is too tight, the packing will lock the stem, resulting in the valve Action is not flexible, the pressure is too loose to seal. 3, carbonation tower cooling system control valve maintenance Pneumatic control valve commonly used methods of maintenance of six: ①increase the sealing grease method: unused sealed grease valve, consider increasing the sealing grease to improve stem sealing performance. ② increase the packing method: In order to improve the sealing performance of the packing on the valve rod, can increase the packing method. Usually using double, multi-layer mixed filler, simply increase the number of 3 to 5, but the effect is not obvious. ③ replace the graphite packing method: Large use of PTFE packing, because of its operating temperature in the range of -20 ~ 200 ℃, when the temperature in the upper and lower limits change significantly, the sealing performance will be significantly reduced, aging fast, short life expectancy. Flexible graphite filler can overcome these shortcomings and long service life. Therefore, some factories will PTFE filler all replaced by graphite filler, and even the newly purchased control valve will be one of the PTFE filler replaced with graphite filler. However, the use of graphite packing valve action is a large backlash, and some early crawling phenomenon, which must be considered. ④ change the flow, set P2 in the stem end method: When △ P larger, P1 and larger, the seal P1 is obviously more difficult than the seal P2. Therefore, you can take to change the flow of the method, the P1 end of the rod at the end of the P2 in the valve stem, which is high pressure, large pressure valve is more effective. Such as bellows should normally be sealed test P2. ⑤ lens pad sealing method: the upper and lower lid seal, valve seat and the upper and lower valve body seal. If the plane seal rotor pump, under high temperature and pressure, poor sealing, causing leakage. At this point you can use the lens pad seal, can get satisfactory results. ⑥ replace the gasket: so far, most of the gasket is still asbestos board, at high temperatures, poor sealing performance, life expectancy is short, easy to cause leakage. Encounter this situation, can be changed to spiral wound gasket, "O" ring, etc., now many factories have adopted. Based on the above analysis, overhauling the valve as a whole we open the valve replacement spring replacement, and then install the filler, and in the control valve of each layer of "V" -shaped filler in the middle of a small amount (white oil) to improve stem lubrication and sealing Performance. This maintenance method is characterized by: the valve to maintain the original seal and structure, but the material needed for maintenance branch has been unable to solve, and overhaul time is too long, usually a valve takes 1 to 2 days. In view of this situation, we have reformed the original maintenance methods. Open the valve gland, remove the gasket inside the stuffing box, and then hook out the "V" type packing under the gasket 2 to 3 times, add the oily asbestos packing we commonly used, press 2 to 3 layers, the gasket cover After a good gland. It has better pre-tightening force, it will not lock the valve stem under the condition of tight pressure, and the oily asbestos packing has good sealing effect on the regulating valve with water regulating medium. Using this method of sealing, we have 1 # ~ 5 # tower pneumatic control valve overhaul, and achieved satisfactory results. 4, overhaul after the operation of the control valve and the effect After overhaul after over 3 months of operation, carbonization tower cooling system 10 Pneumatic control valve all leaks occur, regulating valve action flexible, adjust the quality to fully meet the requirements of process operation. We VDC control valve leaks overhaul attack, according to the actual work of carbonation tower regulating valve to create a local, comprehensive utilization, easy maintenance methods, this method eliminates the control valve leakage, Reduce the leakage rate of the team and save a lot of manpower, material resources and overhauling time. The successful application of this overhaul skill has gained valuable experience for our future overhaul and has good economic benefits and promotion value. Search Keyword: More Valve Technical Articles