Two C150Mx3 air compressors in the air compressor workshop are large-scale special protection units of our factory. They were started in May 1997 and December 2001 respectively. The main function is to provide industrial wind, instrument wind and catalytic main wind to the refinery system. The unit is produced by Ingersoll Rand of the United States. It adopts PLC constant pressure control, which has high operation and high degree of automation. However, in the operation, the first stage diffuser, the volute corrosion, the cooler fouling, and the secondary rotor appear. Problems such as high vibration and high stator temperature of the motor have brought great hidden dangers to safety production. In this paper, the problems arising in the operation of the equipment are analyzed item by item and corresponding improvement measures are proposed to make the air compressor achieve the purpose of long, stable and excellent operation. 2 Introduction to C150Mx3 Air Compressor 2.1 Structural Features The C150MX3 air compressor adopts a unique vertical split housing, integral bearing and seal (structure tube diagram), which is convenient and quick to replace, compact structure, small footprint and overhaul. It is very convenient to adjust the gap between the impeller and the diffuser. The three-oil wedge sleeve bearing structure is simple, the support stiffness is high, and the performance is stable. The oil film is easy to form under the high-speed operation of the rotor, which can ensure reasonable and sufficient lubrication, and can meet the long-term operation requirements of the equipment. The thrust bearing installed in the bearing housing can adjust the gap value by adjusting the bolt, which is convenient to operate. The dry air is used to isolate the product air and the bearing oil, so that the oil circuit and the medium are completely separated, ensuring that the compressed air is oil-free, and the unit is safely and normally supplied with air. The structure of C150MX3 air compressor is simple. 2 Working principle The unit is a three-stage centrifugal compressor, and the large gear is mounted on the main shaft of the air compressor and driven by the motor. Each stage consists of a pinion shaft and an impeller mounted thereon. The primary, secondary and tertiary shafts are distributed in a circumferential position of a common large gear, and the gears are evenly distributed with a uniform distribution of 120°. The high-speed rotation is driven by a common large gear, and the air compressor inlet and outlet are provided with automatic regulating valves to ensure that the working flow of the unit under the design pressure can be adjusted within the range of 0~100% of the design flow. The atmospheric air passes through the population valve to the first-stage impeller, and enters the diffuser along the radial direction of the impeller. In the diffuser, part of the dynamic pressure energy is converted into static pressure energy, which is then taken away by the interstage cooler to generate the compression process. Compressor technology 3 air compressor station 2 sets of C150Mx3 air compressor failure shutdown statistics 3 air compressor units were started in May 1997 and December 2001 respectively, as of January 2010 cumulative fault shutdown up to 28 times, the specific statistics The situation is shown in Table 1. Table 12 C150Mx3 type unit failure shutdown statistics table No. Unit number Downtime Stop reason Check and treatment 5 machine first stage after cold, high temperature, high level vibration. The primary cooler is severely fouled, the primary cooler is cleaned, and the secondary rotor is dynamically balanced. After the 5th stage is cooled, the temperature is high and the primary cooler is severely fouled, and the primary cooler is cleaned. After the first and second stages of the 5 machine, the temperature is high. First, the secondary cooler descaling, replace the diffuser. After the secondary cooling of the 5 machine, the temperature is high and the stator temperature of the motor is high. Clean the secondary cooler, the motor is cleaned, and the first and second volutes are preserved. The four-stage vibration high-level two-stage rotor is dynamically balanced, and the first and second-stage volutes are preserved and the motor is cleaned. The four-stage secondary vibration high-level rotor is dynamically balanced, and the first-stage impeller is cleaned. The 5-stage secondary vibration high-level rotor is dynamically balanced, and the secondary diffuser is laser-melted to repair. 5 machine after the first cold, high temperature cleaning first stage cooler (old), oil filter. 5 machine low voltage power supply damage oil pressure low interlock lock replacement low voltage power supply damage 4 machine secondary vibration high secondary rotor to do dynamic balance, clean, change diffuser. 5 machine secondary vibration high-definition gray 5 machine first-class cold after high temperature cleaning first-class cooler 4 machine two-stage vibration high two-stage diffuser welding layer falling off 4 machine vibration high, cold high temperature motor cleaning, one, two Stage cooler cleaning, after 1~3 stage rotor west balance dynamic balance, the unit vibration is large, the large gear is removed, the three oil wedge bearing bush is broken and replaced, and then the dynamic balance is turned on in Shanghai (secondary impeller\balance disc is 5) . 5 machine for cable one, two-stage cooler cleaning (secondary impeller, balance plate for 4), the first-stage cooler is added with ultrasonic descaler. After the machine is cold, the temperature is high, the second-stage cooler is cleaned, the second-stage vibration value is high, and the external balance is 4, the temperature is high, and the second-stage cooler is cleaned with the Dyke cleaning solution. Impeller cleaning, 3 coolers cleaning, volute anti-corrosion, motor insulation problems, Nanyang Motor Factory overhaul. After the machine is cold, the temperature is high, the impeller is cleaned, three coolers are cleaned, and the volute is preserved. The 4-stage secondary vibration high-level rotor is dynamically balanced. 4 machine motor stator temperature is high, the current limit of 4 machines is changed from 260A to rated current 242A, which solves the problem of motor overload. The air compressor air intake is reduced from 440m3/min to about 400m3/min. The unit is running smoothly. 4 machine secondary vibration high cleaning second and third stage impeller. 4 machine motor stator high temperature will purify the wind to introduce the motor to increase the circulating air volume measures 4 oil temperature high cooler water supply end block debris, high-pressure water cleaning of the oil cooler. 5 machine 2 level vibration high 2, 3 stage bearing inspection, replace the second and third stage radial bearings. 5 machine motor stator temperature high motor coil cleaning, air duct replacement sponge. 5 machine motor stator temperature high insulation insulation 0.96MQ, motor coil burned out, replace the coil winding, first-stage cooler core water side immersion cleaning 7h, air side 0.2MPa water gun cleaning. It can be seen from Table 1 that the number of failures is: 13 times for 13 machines, and 9 times for 5 times, accounting for 32. 14%; due to the diffuser and the volute corrosion guide 15 times. During the 28 shutdowns of the 2 units, the shutdown caused by the high vibration caused 8 times, accounting for 28.57%; due to the high stator temperature of the motor, the shutdown was 11 times, accounting for 39.28%; due to the high temperature after cooling, the cooler junction The scale machine 6 times, accounting for 21.42% of the heat to improve the compression efficiency, into the next level of compression until the design pressure is reached. 2.3 Control Features The energy-saving CMC (microprocessor) controller is selected to effectively prevent the pressure fluctuation and surge of the unit from occurring, which makes the unit run more stable. The energy-saving effect is 4%~10% higher than that of similar products. In the operation analysis and improvement measures of the powder forest: C150Mx3 air compressor, the main reasons for the unit failure are as follows: (1) The secondary vibration is high; 2) Cooling of the cooler; (3) Corrosion of the diffuser and the volute; (4) High stator temperature of the motor. 4 C150Mx3 air compressor failure shutdown reason analysis 4.1 secondary vibration high (1) impeller structure on the secondary vibration 4, the air compressor's secondary impeller is the whole milled open impeller, the manufacturer to ensure the rotor dynamic balance On the windward surface of the rotor of the four-stage two-stage impeller, there are five small holes with a diameter of 10mm and a depth of 20mm for the counterweight. The five machines also have three small holes of the same size. Therefore, during the operation of the unit, the holes in the surface of the impeller are prone to ash accumulation, which breaks the dynamic balance and causes the vibration value of the unit to rise. In 2004, we cleaned the two holes of the two air compressors, and the secondary vibration of the four machines dropped from 0.95 mils to 0.29 mils. The secondary vibration of the machine dropped from 0.89 mils to 0. Therefore, the impeller is caused by the abnormal vibration of the unit due to the unbalanced dust accumulation. (2) The effect of the air filter on the secondary vibration has been repeatedly repaired, and the surface of the impeller of the two air compressors is coated with dust and hard scale. Insufficient air volume, causing unstable rotor work. Further inspection revealed that: First, there is a large amount of rust in the air collection chamber of the air filter. The main body of the air collection chamber is made of carbon steel lining stainless steel. The connecting bolts inside and the connecting members supporting the filter element are also made of carbon steel, which is easy to corrode and form rust. During the operation of slag and air compressor, the rust slag is sucked with the air and applied to the surface of the impeller. Secondly, the filtration efficiency of the filter element is not up to the requirement. The design specification of the air filter is: filtration accuracy 9%. But in actual operation It is found that in the normal range of filter pressure difference, the unit is disintegrated, and a large amount of ash is still applied on the impeller, indicating that the filter effect of the filter directly affects the normal operation of the air compressor. 4.2 Cooler fouling The C150Mx3 air compressor cooler structure is different from the traditional cooler structure. The traditional air compressor cooler winds the shell and the water goes. The intercooler of the two air compressors is a tubular heat exchanger, and the ring structure is mainly composed of 924 copper tubes with a length of 650 mm and a ¢32. The water goes through the shell, the air goes through the tube, and the tube is embedded with heat-dissipating copper fins (see). A large amount of cooling water flows backwards with the compressed air. This structure theoretically has a high heat transfer efficiency. However, due to the compact structure of the cooler, the arrangement of the heat exchange tubes and the thin wall, the cooling water flows slowly. Under the action of hot air, calcium ions and carbonate ions in the water can easily combine to form calcium carbonate, and the distance between the tube and the tube is small. These scales are difficult to be washed away by water, causing local blockage on the tube wall, affecting The heat exchange effect of the cooler. Therefore, the effect of scale on the heat transfer effect of the copper tube is very obvious. After the cooler is fouled, the heat exchange efficiency drops sharply, and the temperature rises significantly after cooling, and is eventually forced to stop. Therefore, the fouling of the cooler is also an important reason for the long-term stable operation of the unit. C150Mx3 air compressor various stages of coolers and built-in finned tubes 4.3 diffuser and volute corrosion severe C150Mx3 centrifuge two-stage diffuser and cooler interface has an annular joint surface, which is slightly deeper than other parts, It is easy to accumulate water, which may cause local "point" corrosion of the diffuser during operation. Air compressors are generally installed in a relatively clean air environment: first, to ensure the quality of compressed air; second, to prevent corrosion of the air compressor flow surface, resulting in damage to the air compressor. The two open-air acid pools between the two air compressors are only about 50m away from the water car. The air contains a large amount of acid, especially in the rainy season. The air is easy to form acid mist and is highly corrosive. The acid-containing air enters the impeller through the air compressor filter, and then enters the diffuser and the volute. Over time, these flow surfaces are gradually corroded. From 2003 to the present, due to severe corrosion, the 4 air compressor diffuser was replaced twice, and the 5 air compressor diffuser and volute were subjected to 4 times of corrosion protection. Therefore, the poor air quality around the compressor also has a large impact on the safe operation of the unit. 4.4 Motor Stator Temperature High The motor of the C150Mx3 air compressor unit is produced by Siemens, Germany. It adopts natural air-cooled type and has a power of 2237 kW. The structure is compact. The domestic motor factory has not yet mastered the same power and the same volume structure of the motor technology. The disintegration inspection found that the oil in the stator and rotor heat dissipation parts was seriously polluted, which affected the heat dissipation of the motor. Due to the oil and gas generated in the thermal cycle of the air compressor tank, the oil mist remover of the unit is located near the motor. During the operation of the motor, the oil smoke discharged from the oil mister is re-inhaled into the motor, and the dust is firmly absorbed in the motor. The location seriously affects the heat dissipation of the motor, which ultimately leads to a sudden rise in the stator temperature of the motor, which affects the safe operation of the unit. 5 Improvement measures 5.1 High-level vibration value treatment (1) In order to reduce the vibration caused by the small hole ash on the secondary impeller, the relevant maintenance technicians in the maneuvering organization, under the premise of ensuring the rotor dynamic balance, the small hole The treatment is carried out to prevent the ash from damaging the dynamic balance in the hole; the compressor technology (2) is directed to the influence of the water vapor acid pool on the air quality of the air compressor, and it is recommended to improve the acid pool between the water vehicles to prevent the acid mist from spreading and reduce the surrounding Air pollution, at the same time, we replace the carbon filter bolts of the air filter plenum with stainless steel bolts to avoid the generation of rust into the compressor; (3) For the air filter element, it is recommended to select the air filter element and The selection of materials makes it possible to grasp the source of safe and stable operation of the air compressor. 5.2 Cooler scaling treatment For the problem of scale fouling, on the one hand cleaning the scaled cooler and continuously improving the cleaning technology; on the other hand, we understand that the ultrasonic scaler has good descaling effect on such coolers. . It is recommended to install an ultrasonic anti-scaler to prevent fouling of the cooler. (1) In 2007, in response to the scaling problem of the cooler, the manufacturer communicated with the Ingersoll-Rand manufacturers to break the cleaning method of the conventional online disassembly of the cooler, and the chemical cleaning method has achieved good results. In the chemical cleaning method, the outside of the cooler is first cleaned with a high-pressure water gun to remove dust, scale, and the like, and then the cooler is hoisted in the pickling tank while the pump is turned on for circulation. In order to prevent damage to the cooler during the pickling process, copper coupon corrosion monitoring is performed in the pickling tank. After pickling, the inner wall and fins of each tube are cleaned with a high-pressure water jet, and the cooling water line is modified, and the strainer is added before the inlet valve. (2) Ultrasonic anti-scaler is installed at the pipeline of the 5 machine cooling water population. The principle of the ultrasonic anti-scaler is to use the ultrasonic sound field to treat the cooling water. Under the action of the ultrasonic field, the scale and the chemical properties of the scale-forming material undergo a series of changes, which make it disperse, crush, loose, loose and not easy to apply. The wall of the pipe forms scale. 5.3 Diffuser and volute corrosion treatment For the problems of diffuser and volute corrosion, we have used aluminum plating and steel plating to prevent corrosion. As a result, the machine will run soon, and the diffuser and volute corrosion phenomenon will occur again. After several rounds of discussion by the maneuvering department and the workshop leader, the problem of the diffuser and the volute corrosion has not been found until the 5th machine is running. For the annular joint surface at the interface of the secondary diffuser and the secondary cooler, we wrap the loop of the steel structure with a rubber ring without affecting the mating connection. The steel ring can prevent the accumulation of water, and the rubber ring has Elastic effect, that is, does not affect the original connection and eliminates water accumulation, reducing the corrosion of the diffuser. 5.4 High motor stator temperature For the problem that the oil mist remover is close to the motor, the workshop will modify the oil mist remover and lead the oil mist remover outlet to the air compressor plant. At the same time, a DN32 pipeline is drawn from the purifying wind busbar, and after entering the motor, it is divided into four channels to enter the motor air inlet, forced air supply, increase the circulation of the internal air of the motor, and forced cooling of the motor to basically solve the motor stator temperature. High problem. 6 Conclusions Through the analysis of the operation of two Ingersoll Rand C150Mx3 air compressors in our air compressor station, the causes of the unit failures were identified, and the treatment was continued and improved. At present, the operation of the air compressors is generally good. Ensure the supply air demand of the refinery system. Due to the unstable water quality and temperature of the circulating water system, the impact on the operation of the chiller system fluctuates greatly. To ensure the safe operation of the air compressor for a long period of time, it is still the top priority in the technical work of our air compressor workshop. -), female, assistant engineer, bachelor's degree, graduated from Beijing University of Petroleum and Chemical Technology in 2005, majoring in automation, and now China Petroleum and Chemical Corporation Luoyang Branch air compressor workshop engaged in equipment management. Answer: The Prandtl number is a quasi-number used to describe the effect of T on fluid convection heat transfer. It is also called the physical property quasi-number. The symbol is Pr. The mathematical expression is the temperature coefficient of a fluid. The smaller the m2/s Pr is, the larger the kinematic viscosity v of the fluid is, and the lower the temperature coefficient a. The former indicates that the molecular diffusion caused by the movement is increased. The more difficult the temperature is evenly distributed during the heat exchange process, the lower the heat transfer amount; the latter indicates that the fluid has a reduced ability to transmit temperature changes and the heat conduction is lowered. Therefore, the amount of convective heat transfer decreases as the number of Pr increases. For air and water, their Pr can be approximated as a constant treatment: 腽! 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