【MTBE】Analysis of the reasons for frequent overcurrent in the circulation water pump of the MTBE methanol recovery tower

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This post was last edited by Xiao Gong 1985 on 2016-1-29 at 10:13. HaiChuan Chemical Forum – Title: Analysis of the reasons for frequent overcurrent in circulation pumps and corresponding solutions. Author: Guan Gongyu; Time: 2015-7-12 at 13:31. Title: Analysis of the reasons for frequent overcurrent in circulation pumps and corresponding solutions. This post was last edited by Guan Gongyu on 2015-7-13 at 22:09. Below are the basic details of the circulation pump: It is used in an MTBE plant; those who are familiar with this topic are encouraged to share their insights. The pump is used in the bottom of the methanol recovery tower, and the fluid it handles is desalinated water containing trace amounts of methanol. Due to the acidic nature of the incoming material, it causes certain corrosion to the methanol recovery tower. However, we will add or remove water from the recovery tower based on the pH value of the water in the bottom of the tower. Recently, this 3109 pump has been frequently tripping due to overcurrent (rated at 43 amps). The filter needs to be cleaned every 1-2 weeks, and the impeller and pump casing must be descaled every 20 days. After cleaning, the current level drops to 36 amps; it increases by 1-2 amps per day, and after a few days it reaches 42-43 amps, at which point the system shuts down due to overcurrent. The phenomenon has persisted for over 3 months. http://down1.hcbbs.com/forum/201507/12/132543nh6pnvehopenlotq.png.thumb.jpg http://down1.hcbbs.com/forum/201507/12/132544amumty88z30yuuyd.png.thumb.jpg http://down1.hcbbs.com/forum/201507/12/132546tz49qaw6j02rqz6h.png.thumb.jpg http://down1.hcbbs.com/forum/201507/12/132546ono6n3yd6y31318f.png.thumb.jpg http://down1.hcbbs.com/forum/201507/12/132546efthqfdhdcyincp9.png.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133349o2vuvp4ff8fj8f60.png.thumb.jpg Author: Guan Gongyu Time: 2015-7-12 13:37 This post was last edited by Guan Gongyu on 2015-7-12 14:13. These are pictures of the pump body at the installation site. There is rust on the upper layer of the impeller. Please analyze the reason why such a thin layer of rust can form in about 7 days. http://down1.hcbbs.com/forum/201507/12/135302jgq3lnlnb3rlb2al.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/135315cen7urkyzveb72e6.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/135431jnjpnkwn49zzncjk.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133536q8lgjsx8ryogs8ie.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133557yfdzdudz4huqnb5b.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133616ixb5ygjloz9zn5iy.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133633avw2vqbubh4xuu72.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/133650dl7i72lz8jzoh2ht.jpg.thumb.jpg Author: Guan Gongyu Time: 2015-7-12 13:38 This post was last edited by Guan Gongyu on 2015-7-13 21:48. These are the current statistics on pump current levels. Rated at 43 amps. http://down1.hcbbs.com/forum/201507/12/133819c51s8sij5r5posuo.jpg.thumb.jpg Author: Guan Gongyu Time: 2015-7-12 13:39. This post was last edited by Guan Gongyu on 2015-7-12 13:42. This is the method suggested by the supervisor: applying a corrosion-resistant coating to the impeller. It’s not clear whether this will work or not. http://down1.hcbbs.com/forum/201507/12/134057uznzhhqh9ts1m96n.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/134117jvzp38gl80w9z3g0.jpg.thumb.jpg http://down1.hcbbs.com/forum/201507/12/134040jfs8mqr89fq9k5ij.jpg.thumb.jpg Author: Guan Gongyu Time: 2015-7-12 13:49. Here’s what I know about this: 1. The current level decreases after cleaning the impeller, but it rises again after about 7 days. 2. The outer layer is rust. 3. The medium water is acidic, and the temperature is not particularly high. 4. The ring gap of the pump is 0.6–0.8 millimeters. 5. It is suspected that the small gap in the mouth ring leads to rust formation; with an even smaller gap, overcurrent is likely to occur. 6. The impeller was replaced with a smaller one earlier, resulting in insufficient flow rate. 7. Previously, running the wear ring around once didn’t yield very good results; it had some effect though. 8. I suspect it’s caused by friction between the rotor and the stator. 9. What do you think?:):):):) It ran continuously, and this problem didn’t occur at the beginning of operation. It’s the first time driving the vehicle after maintenance, and this pump keeps having this problem. Corrosion of the tower is suspected, with rust adhering to the impeller and rotor stator. . Author: bage Time: 2015-7-13 09:05 From the poster’s description, rust enters the pump from ahead of it; therefore, the anti-corrosion coating is likely to be ineffective. The problem should be addressed by tackling the root cause of rust. Author: melamine Time: 2015-7-13 09:59 How did the original poster determine that the black substance was rust? It could also be a polymer. It is recommended that the poster: 1) change from intermittent water replenishment and replacement based on pH to continuous low-flow water replenishment and replacement, in order to eliminate human factors and ensure that the pH at the bottom of the tower remains within the specified range. 2. Analyze the composition of the black substance on the impeller and determine its source, attempting to eliminate it. 3. If it cannot be eliminated, switch the pump before it experiences overcurrent and clean it. Isn’t it asking for trouble to frequently cause the pump to trip? Author: wfcl_wsh Time: 2015-7-13 10:04 Is the tower a packed tower? Is the packing filled in the maintenance tower? Author: Polymer Repair Date: 2015-7-13 11:59 Wait, open it up to check if the coating is damaged. If the current level rises again after a few days, it is necessary to consider whether the coating material can withstand damage from the medium. Applying a coating is one way to address this issue, but attention should be paid to the following points: 1. The surface must be properly prepared according to the surface treatment requirements specified for that material. 2. In terms of material selection, it is essential to choose appropriate materials that meet the requirements for use under various operating conditions. 3. It is recommended to use an ultra-smooth cerametallic coating, which not only prevents corrosion and reduces current flow but also prevents the accumulation of impurities, rust, and other deposits. Author: zhong181 Time: 2015-7-13 12:07 I think the rust adheres to the surface; it’s not part of the material itself. Changing the material won’t help – the problem lies in the earlier stages of the process. It is suggested that the water inlet be located slightly above the bottom of the tower, with a device for regular discharge at a lower point. I’m not sure if this will work. Author: Cuihua Maoge Time: 2015-7-13 12:41 In acidic environments, corrosion leads to excessive rust formation. The frictional wear at the shaft sleeves and seals increases, thereby increasing the load on the pump. Something needs to be done regarding the inlet pipelines. The motor power might also be a bit low. Author: liangmaoqian Time: 2015-7-13 12:55 It’s probably a problem with the materials used in the manufacturing process The data table shows methanol and water; it shouldn’t be like this. Check the upstream situation. Author: The Cat God Who Never Gives Up Time: 2015-7-13 13:04 A motor with higher power was used; what comes from upstream sticks to the impeller, but it’s quite difficult to deal with that issue related to the impeller. Author: She Chang’e Time: July 13, 2015, 13:25 Is it rust on the recovery tower? It’s necessary to measure the thickness of the tower body and pipelines.
Author: WQC Time: July 13, 2015, 14:27 When encountering such problems, it’s essential to first analyze the causes before taking any measures. The analysis should be conducted from the following aspects: 1. Determine whether it’s corrosion products or reaction products formed in the medium ； 2. The reason for the tripping was an increase in frictional resistance due to the reduction of the clearance in certain areas caused by these products ； 3. If it is corrosion product, the material of the flow-through components can be upgraded or an anti-corrosion layer added ； 4. If so, add a suitable filter before the reaction product pump ； 5. The clearances in certain areas can also be increased, as long as it does not affect the safe operation of the pump. Author: Ameba Time: July 13, 2015, 14:54 It seems that applying rust preventive paint might have a negative effect. Visually, the impeller appears quite clean; the source of the rust must be from previous processing steps.
Author: springpang Time: July 13, 2015, 16:56 Demineralized water containing a small amount of methanol serves as a breeding ground for bacteria. Among these bacteria, iron bacteria are the main cause of equipment corrosion and rust formation; they also contribute to the gradual increase in pump current. Please try adding an appropriate amount of biocide to the water (preferably a biocide that removes iron). Author: Guan Gongyu Time: 2015-7-13 21:49 The material upstream is acidic; this tower is made of carbon steel. Of course, there is corrosion. Author: wsm1988 Date: 2015-7-13 21:49 Rust and impurities combine to cause the gaps in the impeller’s flow channels to become too small, resulting in increased mechanical losses and excessive current flow. Author: Guan Gongyu Time: 2015-7-13 21:52 Iron bacteria – I’ve heard of them for the first time. Is it easy to form them? . . Rust is indeed a problem; we know that the materials are acidic, and since the tower isn’t corrosion-resistant, rust forms naturally. But it’s incredible how quickly a layer of rust can accumulate on the impeller in about 7 days. Author: Guan Gongyu Time: 2015-7-13 21:54 The experienced maintenance workers said the same thing. The cause of the rust accumulation cannot be identified, nor can the reason for the high current level. One can only try to see if applying an anti-rust coating will work. . We are getting ready to put this impeller into use in the next couple of days. Let’s see the results. . . Author: Guan Gongyu Time: 2015-7-13 21:57 Considering switching to a motor with higher power. However, purchasing it is a bit troublesome; I’m trying to handle it with a simple method for now, and if that doesn’t work, I’ll have to replace the motor. Author: Guan Gongyu Time: 2015-7-13 22:11 Yes, we also believe so; we just don’t know the reason for the formation of rust. Also, we changed the mouth ring, but the effect wasn’t very good. Now try applying the rust prevention layer. . Author: liuqun06092863 Time: 2015-7-14 07:53 Once the coating is applied and operation stabilizes, the current level becomes higher than before. In my opinion, the high current is caused by impurities attached to the impeller; it’s necessary to check whether the impurities in the filter are of the same type as those on the impeller, in order to determine their source. Additionally, it’s important to examine the material used in the heat exchanger tubes, as well as the magnetism of the impeller (we have encountered this issue on-site where the impellers develop magnetism and attract iron particles). It’s also worth considering whether the impurities attached to the impeller could cause excessive vibration in the machine Author: melamine Time: 2015-7-14 08:41 It is precisely because maintenance is required so frequently that a permanent solution is needed; at the very least, we must ensure that the pumps are not damaged as a result. Otherwise, it wouldn’t be a frequent issue; parking and holidays are both possible. Managers must also change their mindset and promptly address the wrong ideas among frontline employees. The roles of the guide and the guided have been reversed. Author: Guan Gongyu Time: 2015-7-19 05:34 Latest update: On July 14, the impeller was replaced with one coated in anti-rust paint; the current level remained stable at 36 amps, and it hadn’t changed by the afternoon of the 18th! This is good news; I will keep an eye on it and update you all on the latest developments! Author: Tan Jin Time: 2015-7-19 21:39 Use an impeller with a tungsten carbide coating, and go for a larger motor:D:D:D Author: zhangya*ong Time: 2015-7-20 22:23 Initially, your equipment was operating normally without any rust formation on the impellers or volutes; if rust did appear later on, it’s certain that there was some change in the operating conditions of your system. It’s important to analyze what exactly caused the rust formation. Since this issue occurred on your impellers and volutes, it’s possible that similar problems exist in the pipes and other devices downstream of the pump as well. The problem should be addressed at its source; if only a simple coating of rust-preventing substance is applied to the impeller, I think your solution will only be temporary. I will keep following up on your question. :lol Author: Guan Gongyu Time: 2015-7-20 22:40 I’m also collecting some data. In the MTBE plant, this tower used to be a reaction unit; the catalyst employed was a large-pore sulfonic acid-type cation exchange resin, and the tower itself was made of stainless steel. However, in this unit, pipelines and equipment made of carbon steel are being used. Acidic corrosion definitely exists. Our approach is to increase the rate of water replacement in the wash tower, drain water regularly, and monitor water quality promptly. Rust is inevitable unless the tower is replaced. Author: Guan Gongyu Time: 2015-7-21 21:42 Latest update: P3109B current – 36 amps on the 18th, 37.5 amps on the 19th, 38.5 amps on the 20th, and 39.2 amps on the 21st. From the 14th to the 16th, it remained at 36 amps, and these past few days there has been a trend of excessively high current levels. The situation is not optimistic. The manager said that our pump was not selected properly, with too low shaft power. If all else fails, we’ll have to replace the motor. . Author: whthday Time: 2015-7-21 21:53 Won’t applying an anti-corrosion coating to the impeller cause imbalance in the rotor? ? ? ? Author: Guan Gongyu Time: 2015-7-21 22:05 This one? :Dizzy: I have considered that aspect; once you see the anti-rust coating on the upper floor, I’m not sure how significant the impact will be. After sticking with it for a few days, the same problem occurred again. Author: zhangya*ong Date: 2015-7-21 23:17 In my opinion, a coating can only slow down rust formation; it cannot eliminate the root cause of the problem. Even if you replace the motor, it will only extend its operational life – the underlying issue isn’t resolved! Author: Guan Gongyu Time: 2015-7-21 23:23 Acidic corrosion is inevitable; sulfonate groups are present in the raw materials, leading to corrosion of the system’s pipelines as a result of acidity. In other places, a layer of stainless steel was lined on the inner wall of the tower in this unit, and the results were satisfactory. But this needs to be done before the tower is prefabricated. Our tower is already made of carbon steel, so there’s no other option but to increase the amount of water supplied and removed. Author: zhangya*ong Date: 2015-7-21 23:24 If the problem isn’t addressed at its source, it will continue to exist. Author: Guan Gongyu Date: 2015-7-21 23:27 Well, similar systems exist as well, but the problems aren’t as severe in those cases. It also exists at the source; in terms of operation, the temperature of the reaction bed layer should be controlled so as not to be too high, in order to prevent the catalyst from losing its sulfonate groups. It’s not working much at the moment. It must be that the acidity of the catalyst is too high. Author: hl2343744 Time: 2015-7-21 23:37 The medium in my system was too dirty; impurities got into the ring around the pump impeller, causing the impeller to stick and resulting in excessive current. After installing a filter and polishing the ring, everything returned to normal. You should find the source of the impurities in the medium – it has nothing to do with the pump’s power. Author: Guan Gongyu Time: 2015-7-21 23:46 You’re right; the pump was operating normally during operation, but now, two years later, the problem has become apparent. Author: chengjin2367 Time: 2015-7-25 15:58 It’s still necessary to address the root cause of the rust formation – such an abundance of rust is likely to have a significant impact on the lifespan of the pipes and equipment. Even with a pump that has higher shaft power, regular maintenance is still required; it only provides temporary relief rather than a permanent solution. Author: ZHANGZHANTJ Time: 2015-7-25 18:35 Recommendation: Disassemble the pump, clean all components except the impeller, reinstall it and measure the operating current. If the current decreases significantly, it indicates that the issue is not related to deposits on the impeller; if the current remains the same as before disassembly, then it means that the deposits on the impeller are causing the increased current. This method is used to determine whether the overload is due to reduced clearance and increased friction, or rather due to deposits on the impeller. Choosing a high-power motor is a last resort; it only helps to address the issue of overload tripping. Reducing the formation of deposits is the real solution to the problem. Even if there is no overload issue with the motor, other problems will arise – it’s just a matter of time. Author: Guan Gongyu Time: 2015-7-25 18:45 By cleaning it, the current associated with the impeller was reduced to 36 amps; however, after a few days it rose to 43 amps, causing the system to shut down. A lot of cleaning was needed again. Author: lifevivadeng Time: 2015-7-27 23:14 OP, has there been any change in the data usage? Should we check the outlet check valve and the valves? Author: landsay Date: 2015-7-28 09:27 This post was last edited by landsay on 2015-7-28 09:30. There are many inconsistencies in the information provided by the original poster. 1. In the equipment list, the rated flow rate is listed as 4.5 cubic meters per hour below, but as 7 cubic meters per hour above? 2. When the flow rate is 4.5, the shaft power is 21.3 kilowatts; is it only then that the power of the accompanying motor reaches 22 kilowatts? 3. In the preceding data table, the motor specified is rated at 45 kilowatts. How can the rated current of a 45-kilowatt motor be 43 amperes? 4. Those with a rated current of 43 amps are likely 22-kilowatt motors; obviously, the motor power selected for use with them is too low – how is it possible that the current won’t exceed the limit? ! ! Author: syq000 Date: August 28, 2015, 10:00 AM After the pump stops running, is it easy to turn its shaft? If so, consider replacing it with a motor of higher power.
Author: tiaduqicai Date: 3 days ago
1. Based on the photos of the site provided by the original poster, there is also rust at the filter screen. This rust must have come from the medium being pumped. Please collect some of this rust and have it tested in your company’s laboratory to determine whether it is pure iron or iron salts (iron ions). Based on the test results, we can then infer whether these iron ions are generated by the reaction between an acidic liquid and carbon steel, or whether they are brought in due to excessive impurities in the liquid. Then, based on these inferred results, the anti-corrosion condition of the tower equipment is checked, as well as to determine where iron powder may have entered during the liquid supply process. 2. There isn’t that much iron powder resulting from seal friction; investigate the cause from a process perspective. Author: Guan Gongyu Time: 3 days ago It must be related to the manufacturing process; impurities in the raw materials can be controlled at the source. Acidic corrosion, on the other hand, is more difficult to control. Welcome to Haichuan Chemical Forum (http://bbs.hcbbs.com/) Powered by Discuz! X3.2