Air separation unit operator exam questions
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Exam questions for air separation unit operators 1. What are the process characteristics of this air separation unit? What main systems does this oxygen concentrator consist of? answer: Taking the fifth workshop as an example, the process characteristics are as follows: It adopts the process flow of full low-pressure molecular sieve adsorption, pressurized turbine expander refrigeration, full distillation without hydrogen to produce argon, oxygen external compression, and argon internal compression. It also has the maximum liquid working condition of using backup expander and medium-pressure nitrogen in the pipeline network to produce cryogenic liquid. Taking the 23500m3/h oxygen generator as an example, the process characteristics are:: It adopts the process flow of full low-pressure molecular sieve purification and adsorption, air booster turbine expander refrigeration, full distillation without hydrogen to produce argon, product oxygen external compression, product nitrogen external compression, and argon internal compression. The system consists of raw material air compression system, pre-cooling system, molecular sieve purification system, heat exchange system, booster turbine expander refrigeration system, distillation system, product oxygen and nitrogen compression system and instrument, electronic control system, etc. 2. What is the reason why the air leaving the cooling tower contains a lot of water? answer: The reasons why the air leaving the air cooling tower carries a lot of water are:: 1. Caused by instrument failure in the water level control system. For example, when the water level is high, the emergency discharge valve cannot be opened, the water level self-adjusting valve fails or cannot be opened, the flap liquid level fails, etc. These are the most common reasons for water in the air cooling tower. 2. Operational errors. If the air volume suddenly changes, causing the flow rate to be too fast, it will also cause the air cooling tower to be filled with water. 3. There is a large amount of foam in the water, which makes it difficult to separate the gas and liquid in the air cooling tower, and also causes accidents in which the air leaving the air cooling tower contains a lot of water. 3. Why is the rise or fall of the main cold liquid oxygen level the main indicator of whether the cooling capacity is sufficient? answer: When the air separation unit is under stable operating conditions, the cooling capacity and cooling consumption of the unit remain balanced, and the temperature, pressure, liquid level and other parameters of each part of the unit do not change with time. At this time, the liquid oxygen level of the main cooling system also remains relatively stable. Although there will be fluctuations, there will be no upward or downward trend. When the cooling loss of the device increases, the cooling capacity is insufficient, causing the moisture content of the air entering the lower tower to decrease. In the condenser at the top of the lower tower, the amount of nitrogen to be condensed increases, the main cooling and heating load increases, the corresponding liquid oxygen evaporation volume also increases, and the liquid oxygen level drops. ； On the contrary, if the cooling capacity is too high, the moisture content of the air entering the lower tower will increase. In the main condenser at the top of the lower tower, the amount of nitrogen to be condensed will decrease, and the corresponding evaporation amount of liquid oxygen will also decrease, and the liquid oxygen level will rise. Therefore, whether the cooling capacity of the device is balanced or not is first reflected in the changes in the oxygen level of the main cooling liquid. Of course, the main cooling liquid oxygen level is the main indicator of whether the cooling capacity is balanced, but it is not the only indicator. 4. Due to a power grid failure, the air compressor suddenly stops. How should the air separation system be operated? answer: 1. Close the liquid argon, liquid nitrogen, and liquid oxygen storage tank filling valves ； 2. Switch instrument air to external air supply ； 3. Stop the operation of the supercharged turboexpander and related machines, and close all inlet and outlet valves. ； 4. Place the fractionating tower in a closed state ； 5. Stop the regeneration of the molecular sieve purifier. 6. Disconnect the motor-driven equipment in the device from the power grid ； 7. All devices are treated as temporary parking. 5. Under what circumstances do two expanders need to be started at the same time? What should be paid attention to during operation? answer: 1. The cooling stage and liquid accumulation stage during the start-up process of the air separation system ； 2. When the oxygen pressure is high and the product oxygen is abundant (the fifth workshop also requires that the medium-pressure nitrogen flow can also meet the demand), the maximum liquid working condition is carried out. Operational points: 1. Increase the amount of expansion air ； 2. Adjust the plate temperature in time ； 3. Appropriately reduce product oxygen production ； 4. Bypass part of the expansion air ； 5. Open the liquid discharge valve appropriately ； 6. Adjust the main tower distillation conditions accordingly. 6. Briefly describe the timing, location, medium, method and operational precautions for backfilling liquid during the start-up process of the air separation system? answer: The fundamental reason why the cryogenic liquid reverse full distillation tower can shorten the start-up time of the air separation system and save power consumption is to use the cooling capacity of the cryogenic liquid to meet the needs of equipment startup. Liquid oxygen can speed up the start-up of air separation and save power consumption. 1. Countercharge timing: It should be chosen after the main cold liquid. If in order to save startup time, a large amount of liquid is added in a hurry before the equipment has cooled down, not only will the equipment be damaged due to severe thermal stress effects caused by excessive temperature changes. At the same time, this result only consumes a lot of low-temperature liquid (cooling capacity), but the cooling capacity received by the equipment is very little. The reason is that after the filled liquid is quickly vaporized, it is discharged from the cold box before it can fully exchange heat. At this time, the temperature difference in the hot section of the main heat exchanger is too large, and a considerable part of the cooling capacity filled into the fractionation tower is increased by insufficient reheating and is offset. Theoretically, when the starting temperature of the equipment is relatively high, the unit amount of liquid required for the cooling equipment is relatively large, and when the temperature becomes low, the unit amount of liquid required drops rapidly. When the liquid is close to or has reached the saturation temperature (liquid accumulation stage), the consumption of the charged liquid is minimal, and the supplemented liquid basically remains in the fractionation tower. Actual operation also proves that the best time to replenish liquid should be when the cooling stage of the air separation system ends and enters the liquid accumulation stage (i.e.: Main cold solution). 2. Reverse charging position: Main cooling liquid oxygen side ； medium: Liquid oxygen or oxygen-enriched liquid air ； Way: Use a tank truck to boost pressure and reverse charge or use a liquid storage tank to boost pressure and recharge. The back-filling operation greatly shortens the liquid accumulation stage of the air separation system, and in the later stage of the liquid accumulation stage, the purity adjustment of the distillation system must be gradually started. Therefore, when considering the filling medium, you should choose a liquid that is the same as or has little purity difference from the medium at the filling position when the equipment is operating normally to reduce the purification time. Theoretically and in practical terms, the main condensing evaporator of the fractionation tower is the best location to make full use of the cooling capacity. The main cooling medium is liquid oxygen when the equipment is running normally, so the backfill liquid should be liquid oxygen or oxygen-rich liquid air with higher oxygen content. 3. Precautions for reverse charging operation: a. The connecting pipes must be connected correctly and the joints must be tight and tight without leakage. ； b. To prevent overpressure in the upper tower, the pressure during backfilling or backfilling should not be too high. ； c. Keep someone on site during the filling process and pay attention to pressure changes at any time. ； d. Coordinate the upper and lower parts to ensure the filling is in place. 7. How do you understand "Adjusting the purity of the main tower is the basis for adjusting the purity of the crude argon tower"? answer: Argon has two argon-rich zones in the upper tower, one in the rectification section and one in the stripping section. The argon fraction tap is generally in the stripping section. When the oxygen purity increases, the argon-rich area moves up, and conversely, the argon-rich area moves down. The purity of the main tower includes oxygen purity and nitrogen purity. Only when the oxygen and nitrogen purity are stable, the purity of the crude argon tower is stable. Otherwise, there is no way to adjust the purity of the crude argon tower. ； The raw gas and cooling capacity of the crude argon tower come from the main cooling and return to the main tower. The crude argon tower and the main tower are closely related and influence each other. Therefore, the basis for adjusting the purity of the crude argon tower is that the operating conditions of the main tower are stable, the output and quality of oxygen and nitrogen products are close to or reaching normal values, and the cooling capacity is sufficient. 8. Briefly describe the principle of molecular sieve adsorption? answer: The holes in the molecular sieve account for about 50% of the volume. Each gram of molecular sieve has a surface area of 80 to 700 m2 adsorbed inside the holes, which can suck molecules smaller than the holes into the holes and block molecules larger than the holes from the holes, playing the role of screening molecules. 9. Briefly describe the principle of turbine expander refrigeration? answer: From the perspective of the entire process of gas flowing through the expander, the reduction in gas pressure is an expansion process, and work is output to the outside at the same time. The output of external work is based on the consumption of energy inside the gas, which reflects the decrease in temperature and the reduction in enthalpy, that is, a part of the energy is taken away from the inside of the gas, which is usually said to produce cold energy. 10. Briefly describe the principle of air cryogenic separation? answer: The air is first compressed, then expanded and cooled, cooled and liquefied, and then the different boiling points of oxygen and nitrogen are used. In the distillation tower, under a certain pressure and temperature, through the mutual contact of steam and liquid, more oxygen in the steam is condensed, and more nitrogen in the liquid evaporates. Through multiple contacts, the purpose of separating oxygen and nitrogen is achieved. 11. What is pressure? What are its commonly used units? How to convert? answer: 1. The force acting on unit area is called pressure. 2. Commonly used units include: Standard atmospheric pressure, engineering atmospheric pressure (Kg·f/cm2), mmH2O, mmHg, b/in2 (pounds per square inch). 3. Conversion: 1Pa＝1N/m2（1Kg＝9.8N） 1standard atmospheric pressure＝1.013×105Pa 1engineering atmospheric pressure＝9.81×104Pa 1mmH2O＝9.81Pa 1mmHg＝133.32Pa 1b/in2＝6894.76Pa＝0.07engineering atmospheric pressure（Kg•f/cm2） 12. Briefly describe the various means and methods you use when inspecting operating equipment? answer: 1. Strengthen routine inspections and rationally use the senses: rely on human feeling ---- a. Visual method b. Hearing method c. Hand touch method d. Smell method 2. For modern operators of many types of large centrifugal compressors, it is difficult to diagnose based on traditional methods alone based on human feeling and experience. Today, mastering computers and related technologies has become the core of detection and fault diagnosis. Advanced online detection, portable detection instruments and scientific reasoning methods must be applied for detection and diagnosis. a. Application of microcomputer display curve b. Application of testing instruments---vibration meter, thermometer c. Application of professional knowledge, operating information, scientific logical reasoning method 13. What impact does changes in environmental conditions (atmospheric pressure, ambient temperature, atmospheric humidity and impurities in the air) have on the performance of the related equipment of the oxygen generator? answer: 1. The reduction of atmospheric pressure will increase the compression ratio of the air compressor, reduce the exhaust volume of the air compressor, the corresponding oxygen production will also decrease, and the unit power consumption of oxygen production will increase. ； 2. As the ambient temperature increases, the exhaust volume of the air compressor decreases, the shaft power increases, the exhaust temperature of the air compressor increases, the cooling loss increases, and the energy consumption increases. ； 3. As the atmospheric humidity increases, the shaft power of the air compressor increases. ； 4. The increase in impurity content in the atmosphere increases the purification load of the molecular sieve adsorber. 14. What is "surge", and what are the typical phenomena when surge occurs in a turbine compressor? answer: surge: It is a kind of vibration that occurs under abnormal working conditions of a turbine compressor when the flow rate is reduced to a certain extent. Centrifugal compressor is a form of turbine compressor, and surge is very harmful to centrifugal compressors. When surge occurs in a centrifugal compressor, typical phenomena include:: 1. The outlet pressure of the compressor initially increases, then drops sharply, and changes periodically. 2. The flow rate of the compressor drops sharply and fluctuates greatly. In severe cases, air may even flow back into the suction pipe. 3. The current and power meter indications of the motor driving the compressor are unstable and fluctuate greatly. 4. The machine generates strong vibration and abnormal air flow noise. 15. What are the possible reasons for the increase in bearing temperature of centrifugal compressors, and how to deal with them? answer: The operating temperature of centrifugal compressor bearings should generally be 45-50°C, and the best temperature should not exceed 65°C. Generally, 65℃ is the alarm temperature and 75℃ is the chain shutdown temperature. The causes of excessive bearing temperature are:: ⑴The gap between the bearing bush and the journal is too small, and the bush should be scraped to adjust the gap. ⑵The aperture of the throttle ring at the inlet of the bearing lubricating oil is small and the amount of oil inlet is insufficient. The aperture of the throttle ring should be appropriately increased. ⑶The inlet oil temperature is too high. The cooling water volume of the oil cooler should be adjusted. ⑷The oil is mixed with water or is dirty or deteriorated, which affects the lubrication effect. The oil cooler should be checked to eliminate water leakage or replace with new oil. ⑸Dirt enters the bearings and wears out the bearings. Bearings and lubricating oil lines should be cleaned, and bushings should be scraped. ⑹If the bearing bush is damaged, the bearing bush should be recast. 16. What are the reasons that can cause the air compressor to burn tiles, and how to prevent it? answer: 1. Poor oil quality ； 2. Oil temperature is too high ； 3. Oil pump leakage causes oil volume to decrease ； 4. Compressor reverses ； 5. The axial displacement is too large. 17. How does the axial displacement of the centrifugal compressor occur? How to prevent excessive axial displacement? answer: The axial displacement of the centrifugal compressor is first due to the existence of axial force. The generation process of axial force is as follows: After the gas passes through the working wheel, the pressure is increased, causing the front and rear of the working wheel to bear different gas pressures. Since the axial forces on both sides of the wheel from the outer diameter D2 to the diameter Df of the wheel cover sealing ring cancel each other, its axial force consists of the following three parts: ⑴F1---The force of the gas on the back of the wheel disc from the diameter Df to the diameter df of the journal seal ring. ⑵F2---The gas pressure endured by the area from diameter Df to d at the inlet of the working wheel. ⑶F3---The impact force produced by the inlet airflow on the wheel disc at a certain speed. Under certain circumstances, F1>(F2+F3), so the axial thrust of each impeller is directed from the disc side of the impeller to the inlet side (disc side). If all impellers are installed in the same direction, the total axial force will be considerable. In order to reduce the axial force, a balance plate is usually used, and the pressure difference on both sides of the balance plate is used to generate air in the opposite direction to the above-mentioned axial force, or a double-sided air intake impeller is used to reduce the axial force, and the remaining part is borne by the thrust bearing. During the operation of the compressor, when the seal of the balance plate is damaged, or the small pipe that connects the low-pressure chamber to the atmosphere behind the balance plate is blocked, and loses the ability to offset part of the axial thrust, the axial force of the rotor will increase sharply, making it difficult for the thrust bearing to bear, and eventually causing a large axial displacement. In addition, when the thrust bearing alloy is excessively worn or melts due to other sudden accidents (such as a sudden oil cutoff in the lubrication system), excessive axial displacement will also occur. For safety reasons, centrifugal compressors are equipped with axial displacement safety indicators. When the axial displacement exceeds the allowable value, the indicator will issue an audible and visual alarm or automatically shut down. Remember! In any case, if the axial displacement is too large, the machine must be stopped immediately to avoid a major accident in which the rotor and fixed components collide. 18. If the oil temperature of the compressor lubricating oil is too high or too low, what impact will it have on the work of the compressor? What measures should be taken? answer: 1. If the oil temperature is too high, the cooling effect of the bearing will not be good, causing the bearing temperature to rise. ； High oil temperature will reduce the viscosity of the oil, which will cause local oil film damage and reduce the bearing capacity of the bearing. ； Even the lubricating oil is carbonized and burned. ； 2. The oil temperature is too low, the viscosity of the oil increases, and the friction increases. ； Bearing power consumption increases ； It can also cause machine vibration. 19. Why is the rotation speed of turbine compressor higher than that of piston compressor? answer: The higher the turbine compressor speed, the greater the pressure increase. The higher the turbine compressor speed, the smaller the diameter of the impeller can be, reducing the weight of the machine. The higher the turbine compressor speed, the fewer stages can be achieved relative to the total pressure ratio. The piston compressor has large operating inertia, which limits the increase in machine speed. 20. Under what circumstances is the turning of the compressor usually performed, and what is its function? answer: Before driving, start the oil pump and crank the engine 2-3 times to check whether there is any sticking or friction in the engine. After maintenance, check whether there is any foreign matter left in the machine. After stopping, because the pressure and temperature of the centrifuge are high when running before stopping, it is still in a high temperature state after stopping, and the rotor has stopped at a certain position, which can easily cause local thermal deformation and cause shaft bending. Therefore, after stopping, the centrifuge should be turned at different angles multiple times until it cools down completely. (The two nitrogen compressors in the fifth workshop are produced by the American Ingersoll Rand Company. Their on-site service personnel require that the vibration values of the rotors at all levels be observed when the unit is turning. If the value exceeds the shutdown value, the cover must be removed for inspection. ) 21. What factors will affect the displacement of centrifugal compressors? answer: 1. The inlet resistance of the air compressor increases, such as the guide vane opening is too small, valve failure and other reasons. 2. The resistance of the air filter and filter increases, causing the suction resistance to increase. 3. The compressor cooler is not effective, causing the machine efficiency to decrease. 4. The machine is not well sealed and leaks, and the cooler leaks, causing part of the gas to leak out. 5. The frequency and voltage of the power grid decrease, causing the motor speed to decrease and the exhaust volume to decrease. 6. As the suction temperature increases, the gas density decreases. 22. Under what circumstances does the oil pump automatically switch on? What other operations should be performed after the oil pump is put into operation? answer: When the operating oil pressure of the unit drops to the "standby pump mutual switching setting value" (power outage, oil pump failure, instrument and control system malfunction, etc.), the oil pump will automatically switch on. In order to prevent the unit from losing oil and burning the bearings due to the oil pressure dropping too low or even to zero. If the main oil pump stops operating due to a power outage, just check and confirm that the power supply is turned on. ； If the main oil pump shuts down due to failure, turn the oil pump mutual switching switch to the manual position, cut off the power supply, and then inspect the oil pump. ； If the main oil pump shuts down due to malfunction of the instrument and control system, it will be restored to normal after the cause is found out. 23. What are the daily inspection contents of the circulating cooling water system (i.e. the large water pump room)? answer: 1. Are the pump and motor operating normally? ； 2. Is the cooling tower fan operating normally? ； 3. Is the dosing device normal? ； 4. Is the filtering device normal? ； 5. Whether the water supply and sewage drainage system are normal. 24. How does the orifice flow meter measure the flow rate? answer: When the fluid passes through the orifice plate, the static pressure decreases and the flow rate increases, resulting in a pressure difference on both sides of the orifice plate. The orifice flowmeter measures the flow rate of the fluid based on the one-to-one correspondence between the pressure difference and the flow rate. 25. What is an air-opening diaphragm regulating valve and what is an air-closing diaphragm regulating valve? In what situations are they used? answer: When there is no pressure signal input, the valve is closed ； When there is a pressure signal, the valve begins to open, and the greater the input signal, the greater the valve opening. This type of membrane regulating valve is called an air-opening membrane regulating valve. When there is no pressure signal input, the valve is fully open, and when there is a pressure signal input, the valve begins to close. ； The greater the input signal, the smaller the valve opening. ； When the input signal reaches the maximum, the valve is fully closed. This type of diaphragm valve is called an air-closed diaphragm regulating valve. In practical applications, the choice of air opening and air closing is mainly based on the safety requirements of production. The principle of consideration is to see what state the regulating valve is in when there is no pressure signal (such as air source failure), which will cause the least harm to production. If the hazard is minimal when the valve is open, choose the air-closed type; if the hazard is minimal when the valve is closed, choose the air-opening type. For example: The liquid air and liquid nitrogen regulating valve and the air volume regulating valve in front of the turbine expander are all air-opening types. When the air is cut off, the valve is closed ； When the fan outlet regulating valve of the fan braked turbine expander is cut off, the valve must be opened so that the expander can work under the maximum braking load to prevent overrun accidents, so the air-closed type must be used. The vent valve on the oxygen storage tank and the nitrogen vent valve on the upper tower are all air-closed. Once a failure occurs, they can be vented during a power outage to ensure safety. 26. Please talk about your understanding of "P, I, D parameters (or K, T1, T2 parameters)"? answer: Several automatic adjustments are derived from imitating manual adjustments. Manual adjustment includes coarse adjustment, re-adjustment and pre-adjustment. Automatic adjustment includes proportion (P or K), integral (I or T1), and differential (D or T2). Proportional adjustment effect: The deviation is obtained through comparison and an output signal proportional to the deviation is sent. If the ratio is too large, the amplification factor will be too large, the adjusted parameters will change too much, and the system will be unstable. ； Otherwise, the adjustment time will be extended. The disadvantage is that there is static difference. Integral adjustment effect: It means that the output of the regulator is the accumulation of deviation over time. In other words, as long as the deviation exists, the output will accumulate over time. The shorter the integration time, the stronger the integration effect. differential adjustment: It represents the changing process of output and deviation. The differential effect can effectively suppress the fluctuation amplitude of the adjusted parameter, which means reducing the variation amplitude of the maximum deviation and increasing the stability of the adjustment process. However, too strong a differential effect is equivalent to excessive manual pre-adjustment, which will aggravate the oscillation of the adjustment process. 27. Please talk about your understanding of "nitrous oxide (N2O)"? answer: A. Nitrous oxide is also called nitrous oxide, commonly known as "laughing gas". The content in the atmosphere is 310 ppb, which can destroy the ozone layer and enhance the greenhouse effect. B. The boiling point of nitrous oxide is higher than that of nitrogen, oxygen, krypton, and xenon. As the boiling temperature of liquid oxygen increases, the solubility of nitrous oxide in liquid oxygen increases. It is a flammable component in a pure oxygen environment. C. The freezing of nitrous oxide in the air separation unit can block pipelines or heat exchangers, and can also cause local accumulation of hydrocarbons in the main cold liquid oxygen. D. Nitrous oxide can only be partially adsorbed in the molecular sieve adsorber. Once the carbon dioxide on the surface of the adsorbent reaches saturation, the adsorbed nitrous oxide will be desorbed and enter the cold box with the air.
Oxygen production worker senior worker practical examination review* Information description: 1. Questions 1 to 44 are worth 35 points, questions 45 to 72 are worth 25 points, and questions 73 to 113 are worth 10 points. 2. After each contestant selects three questions to answer, he will then need to answer one question related to the unit he is currently operating. 1. What are the process characteristics of 20000m3/h, 1#6000m3/h, 2#6000m3/h air separation units? What main systems are they composed of? answer: The process characteristics are: 20000m3/h unit: It adopts the process flow of air pre-cooling system chilled water closed circuit circulation, water cooling tower cooling water (2), full low-pressure molecular sieve adsorption (3), pressurized turbine expander refrigeration (3), full distillation without hydrogen to produce argon (3), and oxygen external compression (3). The system consists of raw material air compression system (3), pre-cooling system (3), molecular sieve purification system (3), heat exchange system (3), booster turbine expander refrigeration system (3), distillation system (3), product oxygen and nitrogen compression system (1) and instrument, electronic control system (1), circulating water system (1), etc. 1#6000m3/h: It adopts the process flow of air pre-cooling system chilled water closed circuit circulation, refrigerator cooling water (2), full low-pressure molecular sieve purification and adsorption (3), air booster turbine expander refrigeration (3), hydrogenation to produce argon (3), and product oxygen external compression (3). The system consists of raw material air compression system (3), pre-cooling system (3), molecular sieve purification system (3), heat exchange system (3), booster turbine expander refrigeration system (3), distillation system (3), product oxygen and nitrogen compression system (1) and instrument, electronic control system (1), circulating water system (1), etc. 2#6000m3/h: It adopts the process flow of air pre-cooling system chilled water open circuit circulation (2), full low-pressure molecular sieve adsorption (3), pressurized turbine expander refrigeration (3), full distillation without hydrogen to produce argon (3), and oxygen external compression (3). The system consists of raw material air compression system (3), pre-cooling system (3), molecular sieve purification system (3), heat exchange system (3), booster turbine expander refrigeration system (3), distillation system (3), product oxygen and nitrogen compression system (1) and instrument, electronic control system (1), circulating water system (1), etc. 2. What is the reason why the air leaving the cooling tower contains a lot of water? answer: The reasons why the air leaving the air cooling tower carries a lot of water are:: 1. Caused by instrument failure in the water level control system. For example, when the water level is high, the emergency discharge valve cannot be opened, the water level self-adjusting valve fails or cannot be opened, the flap liquid level fails, etc. These are the most common reasons for water in the air cooling tower. (15) 2. Operation error. If the air volume suddenly changes, causing the flow rate to be too fast, it will also cause the air cooling tower to be filled with water. (10) 3. There is a large amount of foam in the water, which makes it difficult to separate the gas and liquid in the air cooling tower, and also causes accidents in which the air leaves the tower with a large amount of water. (10) 3. Under what circumstances do two expanders need to be started at the same time? What should be paid attention to during operation? answer: 1. The cooling stage and liquid accumulation stage during the start-up process of the air separation system ； (8) 2. When the oxygen pressure is high and the product is rich in oxygen, the maximum liquid production condition is performed (8). Operational points: 1. Increase the amount of expansion air ； (7) 2. Adjust the plate temperature in time ； (3) 3. Appropriately reduce product oxygen production ； (3) 4. Bypass partial expansion air ； (3 5. Open the liquid discharge valve appropriately ； (3) 4. Briefly describe the various means and methods you use when inspecting operating equipment? answer: 1. Reasonable use of the senses: relying on human feelings ---- (3) a. Visual method (4) b. Hearing method (4) c. Touch method (4) d. Smell method (4) 2. Use computers and related technologies (1) a. Use microcomputer to display curves (3) b. Apply testing instruments---vibration meter, thermometer (3) c. Apply professional knowledge, operating information, and scientific logical reasoning methods (3) 5. Under what circumstances is compressor cranking generally performed, and what is its function? answer: 1. Before driving, start the oil pump and crank the engine for 2-3 turns to check whether there is any jamming (5) and friction (5) in the machine. 2. After maintenance, check whether there are foreign objects left in the machine (5). After stopping, because the pressure and temperature of the centrifuge are high when running before stopping, it is still in a high temperature state after stopping (5), and the rotor has stopped at a certain position, which can easily cause local thermal deformation (5) and cause shaft bending (5). Therefore, after stopping, the centrifuge should be turned at different angles multiple times until it cools down completely. For two nitrogen turbine compressors produced by Ingersoll Rand in the United States, it is required to pay attention to the vibration values of the rotors at all levels when turning the unit. If it exceeds the shutdown value, the cover needs to be uncovered for inspection. (5) 6. Under what circumstances does the oil pump automatically switch on? What other operations should be performed after the oil pump is put into operation? answer: When the operating oil pressure of the unit drops (5) to the "standby pump mutual switching setting value" (power outage (4), oil pump failure (4), instrument control system malfunction (4), etc.), the oil pump will automatically switch on. In order to prevent the unit from losing oil and burning the bearings due to the oil pressure dropping too low or even to zero. (5) If the main oil pump stops operating due to a power outage, just check and confirm that the power supply is turned on. ； (4) If the main oil pump shuts down due to failure, turn the oil pump mutual switching switch to the manual position, cut off the power supply, and then inspect the oil pump. ； (5) If the main oil pump shuts down due to malfunction of the instrument and control system, find out the cause and restore it to normal. (4) 7. What are the daily inspection contents of the circulating cooling water system? answer: 1. Are the pump and motor operating normally? ； (7) 2. Is the cooling tower fan operating normally? ； (7) 3. Is the dosing device normal? ； (7) 4. Is the filtering device normal? ； (7) 5. Whether the water supply and sewage drainage system are normal. (7) 8. After the oxygen compressor is overhauled, how to conduct a nitrogen test run? answer: 1. Check that the water supply is normal (3 points) ； 2. Check that the sealing gas supply is normal or the vacuum pump is operating normally (4 points) ； 3. Start the oil pump and confirm that the oil supply is normal (4 points) ； 4. Turning is normal (3 points) ； 5. The power supply system is normal (3 points) ； 6. Instrument indication and interlocking are normal (3 points) ； 7. Operate the relevant valves to the correct position (4 points) ； 8. Start the compressor, the sound and vibration are normal (4 points) ； 9. Slowly pressurize and check for normal leaks (4 points) ； 10. Relieve pressure and stop the vehicle for backup (3 points). 9. How to conduct a more comprehensive inspection of the air filter of the air compressor during operation? answer: 1. Is the resistance normal (7 points) ； 2. Is the ash discharge normal (7 points) ； 3. Is the mechanical cleaning mechanism or pulse cleaning mechanism normal (7 points) ； 4. Whether the filter bag falls off (7 points) ； 5. Is the sealing good (7 points) ； 10. How to check the main motor of the air filter? (Full marks are awarded for 8 points for correct answers, and 4 points for each correct answer). answer: Shaft temperature, oil pressure, return oil temperature, stator temperature, voltage, current, water temperature, air temperature, vibration, smell, sound. 11. What are the preparations before starting the backup oxygen compressor? answer: 1. Check that the water supply is normal (5 points) ； 2. Check that the sealing gas supply is normal or the vacuum pump is operating normally (5 points) ； 3. Start the oil pump and confirm that the oil supply is normal (5 points) ； 4. Turning is normal (5 points) ； 5. The power supply system is normal (5 points) ； 6. Instrument indication and interlocking are normal (5 points) ； 7. Operate the relevant valves to the correct position (5 points) 12. After the air compressor has been inspected and tested, how do you stop it? answer: (5 points for each correct answer,) 1. Open the anti-surge valve to relieve pressure. ； 2. Fully open electric or manual vent valve ； 3. Close the inlet guide vane ； 4. Stop the main motor ； 5. Turning ； 6. Stop the oil system operation after 20 minutes ； 7. Others (stop filter, soundproof cover fan, winter drainage, oil fume fan, power outage, etc.). 13. In normal operation of the air separation equipment, the main cold liquid level does not rise high. What are the possible reasons? answer: 1. Main heat exchanger, incomplete heat exchange loss increases (7 points). 2. The temperature difference of the expander is small, the efficiency is low, and the expansion amount is small (7 points). 3. The temperature of the air entering the main heat exchanger is high (the air cooling system is faulty or the molecular sieve adsorber is not completely cooled) (7 points). 4. The equipment leaks and the cooling loss increases (7 points). 5. A large amount of liquid product is taken out (7 points). 14. When the liquid air level positive pipe of the crude argon tower condenser leaks, what parameters and regulating valves will change in the process? answer: (Full marks for more than five correct answers) 1. The crude argon tower liquid air level indicator is low (7 points) ； 2. Open the liquid-air throttle valve into the condenser (7 minutes) ； 3. Close the liquid air throttle valve in the upper tower (7 minutes) ； 4. The resistance of the crude argon column changes (7 points) ； 5. The main cooling liquid oxygen level decreases (7 points) ； 6. The oxygen content of the argon fraction increases (7 points). 15. When the total oxygen production is sufficient and liquid oxygen is required to be produced, how should the air separation work be performed? answer: (Full marks for five or more correct answers) 1. Increase the amount of expansion (7 points) ； 2. Adjust plate temperature (7 points) ； 3. Reduce oxygen production (7 points) ； 4. Bypass air volume (7 points) ； 5. Adjust the distillation conditions of the lower tower (7 minutes). 16. What equipment in the oxygen production system are used to remove impurities other than oxygen, nitrogen and argon in the air? answer: (Full marks for five or more correct answers) 1. Air filter 2. Plate heat exchanger or molecular sieve adsorber 3. Air cooling tower 4. Non-condensable gas blowing 5.1% liquid oxygen injection or production of liquid oxygen products 6. Liquid air adsorber 17. What should be checked before starting the expander and be ready to start? answer: 1. The sealing air pressure is normal (7 points) ； 2. Check that the water supply is normal (7 points) ； 3. Start the oil pump and the oil supply system is normal (7 points) ； 4. Instrument control interlock test and instrument indication are normal (7 points) ； 5. The valve position is correct (7 points). 18. The liquid nitrogen throttle valve suddenly shut down due to malfunction. What changes will happen to the oxygen generator in two hours? answer: (Full marks will be awarded if more than five correct answers are given) 1. Oxygen content of argon fraction (increases and then decreases) (7 points) ； 2. The resistance of the lower tower increases (7 points) ； 3. The resistance to ascending the tower decreases (7 points) ； 4. The air liquid level rises or the air liquid throttle valve is opened wide (7 points) ； 5. The purity of liquid air decreases (7 points) ； 6. The purity of liquid oxygen decreases (7 points) ； 7. The resistance of the crude argon column decreases (7 points). 19. What should you do if the circulating argon pump suddenly stops while it is running? answer: 1. Close the inlet and outlet valves (4 points) ； 2. Open the drain valve (4 minutes) ； 3. Heat, find the cause, eliminate it and reserve (3 points). 4. Pre-cooling backup pump (4 points) ； 5. Appropriately reduce oxygen production (4 points) ； 6. Produce some liquid oxygen or liquid nitrogen products or reduce expansion (4 points) ； 7. Stop the argon system (3 points) ； 8. Start the backup argon pump (3 points) ； 9. Adjust the crude argon column to normal (3 points) ； 10. Invest in argon tower (3 points). 20. After the argon compressor is shut down due to an accident, while the backup machine is being inspected, what should you do? answer: (Full marks will be given for more than five correct answers) 1. Stop hydrogenation (7 points) ； 2. Stop the refrigerator or turn off the working water (7 points) ； 3. Stop the dryer (7 minutes) ； 4. Crude argon venting (7 minutes) ； 5. Stop the argon tower (7 minutes) ； 6. Adjust the surplus cooling capacity (produce some liquid products or reduce expansion) (7 points). 21. When the air separation starts to accumulate liquid to meet the adjusted purity, how do you operate until the crude argon is qualified and the oxygen production reaches the standard? answer: 1. Adjust the opening of the liquid nitrogen throttle valve and liquid nitrogen return valve according to the purity of the liquid air (7 points) ； 2. Increase or decrease oxygen production according to changes in oxygen purity (7 points) ； 3. Add crude argon column according to the change of argon fraction (7 points) ； 4. Expander volume reduction (4 points) 22. After the molecular sieve enters water, the carbon dioxide content exceeds the standard. The operating air separation system is ready to shut down and start molecular sieve activation. How do you operate until the activation is completed? answer: 1. Pour instrument air (4 points) ； 2. Discontinued product compressor (3 points) ； 3. Stop the production of all liquid products, spray 1% liquid oxygen, and vent gas products (3 points) ； 4. Stop the argon system (3 points) ； 5. Stop the expander (3 points) ； 6. Operate air separation related valves (4 points) ； 7. Open the air regeneration valve (4 points) ； 8. Slowly close the air inlet cold box valve (3 minutes) ； 9. Set the temperature of the electric heater (4 minutes) ； 10. End after two cycles (or more) of activation (4 points). 23. What are the possible reasons for the unexpected shutdown of the expander? answer: The speed is too high (7 points), the oil pressure is too low (7 points), the shaft temperature is too high (7 points), the instrument gas pressure is lost (7 points), and the emergency solenoid valve is powered off (7 points). 24. The outlet valve of the #1 normal temperature pump is faulty during normal operation and is now planned to be replaced. What should be done (until the fitter starts working)? answer: 1. Pour the instrument gas (4 points) ； 2. Stop the product compressor and vent the product gas (4 points) ； 3. Stop the production of liquid products and spray 1% liquid oxygen (4 points) ； 4. Stop the argon system (4 points) ； 5. Stop the expander (4 points) ； 6. Operate valves related to air separation (3 points) ； 7. Vent the air compressor and close the air supply valve (3 minutes) ； 8. Stop the water pump and close the relevant valves (3 points) ； 9. Molecular sieve pauses or switches the system to stop (3 points) ； 10. Relieve the pressure in the air cooling tower and close the pressurized return water (3 minutes). 25. After the crude argon tower is plugged with nitrogen, the oxygen purity indicates 98.5% and is still declining. How to operate until the oxygen purity starts to rise? answer: 1. Vent or stop the oxygen compressor (10 minutes) ； 2. Reduce oxygen production (5 points) ； 3. Stop the operation of the refined argon tower (5 minutes) ； 4. Stop production of liquid products (5 points) ； 5. Full cycle or stop the argon pump (5 points) ； 6. Cooling capacity distribution or expansion machine reduction (5 points). 26. How do you warm up the #1 expander to standby after normal shutdown? answer: (Correct answer is worth 7 points) 1. Check whether the inlet and outlet valves are closed ； 2. Check that the sealing gas supply is normal and start the oil pump. ； 3. Open the emergency shut-off valve and nozzle ； 4. Open the purge valve and heating valve ； 5. Stop heating and set aside. 27. Briefly describe the principle of molecular sieve adsorption? (35 points) Answer: The holes in the molecular sieve account for about 50% of the volume. Each gram of molecular sieve has a surface area of 80 to 700 m2 adsorbed inside the holes, which can suck molecules smaller than the holes into the holes and block molecules larger than the holes from the holes, playing the role of screening molecules. 28. What impact will changes in space environmental conditions (atmospheric pressure, ambient temperature, atmospheric humidity and impurities in the air) have on the performance of the oxygen generator's related equipment? answer: 1. The reduction of atmospheric pressure will increase the compression ratio of the air compressor, reduce the exhaust volume of the air compressor, the corresponding oxygen production will also decrease, and the unit power consumption of oxygen production will increase. ； (12) 2. As the ambient temperature increases, the exhaust volume of the air compressor decreases, the shaft power increases, the exhaust temperature of the air compressor increases, the cooling loss increases, and the energy consumption increases. ； (12) 3. As the atmospheric humidity increases, the shaft power of the air compressor increases ； (4) 4. The increase in impurity content in the atmosphere increases the purification load of the molecular sieve adsorber. (7) 29. What is "surge", and what are the typical phenomena when surge occurs in a turbine compressor? answer: surge: It is a kind of vibration that occurs under abnormal working conditions of a turbine compressor when the flow rate is reduced to a certain extent. Centrifugal compressor is a form of turbine compressor, and surge is very harmful to centrifugal compressors. (15) When surge occurs in a centrifugal compressor, typical phenomena include:: (5 points each) 1. The outlet pressure of the compressor initially increases, then drops sharply, and changes periodically. 2. The flow rate of the compressor drops sharply and fluctuates greatly. In severe cases, air may even flow back into the suction pipe. 3. The current and power meter indications of the motor driving the compressor are unstable and fluctuate greatly. 4. The machine generates strong vibration and abnormal air flow noise. 30. What may be the causes of vibration in centrifugal compressors, and how to eliminate them? (35 points for 7 correct answers) Answer: 1. The working speed of the rotor is close to the critical speed, which easily causes resonance. The way to eliminate it is to let the working speed of the rotor avoid the critical speed. 2. The rotor dynamic balance is poor. Some are caused by manufacturing problems, and strict dynamic balance inspection was not carried out before leaving the factory. Some are caused by contamination, wear, scaling or other reasons that cause the shaft to deform and lose dynamic balance. If the vibration is caused by this reason, remediation must be carried out according to the specific situation, and the rotor dynamic balance must be corrected again. 3. The processing accuracy of the transmission gear is insufficient and the meshing is poor. The peripheral speed of the speed-increasing gear pair of the centrifugal compressor is usually greater than 120m/s, which is a typical high-speed gear transmission. Therefore, according to * * Standard, its processing accuracy should be no less than level 5, preferably above level 4. Otherwise, excessive vibration will be caused when the gear dynamic load is large. 4. The alignment between the shafts is not good. The only way to eliminate it is to re-check and align the relationship between the compressor shaft and the driven shaft of the speed-increasing gearbox and the driving shaft of the speed-increasing gearbox and the motor shaft. 5. Improper connection of pipelines before and after the compressor. An expander or soft connection device should be installed at the inlet and outlet. Hard-connected pipes will generate external forces on the compressor and adversely affect the operation of the air compressor. 6. The bearing is poorly processed or damaged. The only way to eliminate it is to replace or repair it. 7. Oil film oscillates. For details, please refer to question 419 of the "Newly Established Oxygen Workers Questions and Answers". 8. The main shaft is bent. The spindle needs to be calibrated. 9. Improper operation causes surge. For details, please refer to Questions 410 and 411 of the "Newly Established Oxygen Workers Questions and Answers". 10. The foundation is not strong or the anchor bolts are loose. The foundation should be designed in strict accordance with the data and requirements provided by the manufacturer, in strict accordance with relevant specifications, and by a qualified and experienced design unit. Always check whether the anchor bolts are loose and tighten them with a wrench. 11. There is water or solid matter on the impeller in the casing, which affects the dynamic balance of the impeller and causes vibration, or there is dirt deposited on the aluminum gas seal. The cause of water accumulation should be found out and drained ； Or clean the solid matter and check the air filter chamber to ensure its normal dust removal function. Pay attention to whether the suction pipe of the air compressor is rusted. Pay attention to the effective removal of condensed water between stages (especially stages 3 and 4). Some air compressors are equipped with impellers * * The descaling device should be descaled regularly. 12. The uneven gap between the motor rotor and the stator causes motor vibration and drives the compressor to vibrate. Pay attention to checking and repairing the motor. 13. The bearing oil inlet temperature is too low. The inlet oil temperature should be kept at 35-45°C. 14. Contact friction occurs between the rotor and the gas seal. The sealing gap should be readjusted according to technical requirements. 15. The pressing fit between the bearing cap and the bushing is not tight. The gasket should be adjusted to maintain an interference preload of 0.02-0.05mm between the bearing cap and the bushing. 31. What are the reasons that can cause the air compressor to burn tiles, and how to prevent it? answer: 1. Poor oil quality ； (7) 2. Oil temperature is too high ； (7) 3. Oil pump leakage causes oil volume to decrease ； (7) 4. Compressor reverses ； (7) 5. The axial displacement is too large. (7) 32. If the oil temperature of the compressor lubricating oil is too high or too low, what impact will it have on the work of the compressor? What measures should be taken? answer: 1. If the oil temperature is too high, the cooling effect of the bearing will not be good, causing the bearing temperature to rise. ； High oil temperature will reduce the viscosity of the oil, which will cause local oil film damage and reduce the bearing capacity of the bearing. ； Even the lubricating oil is carbonized and burned. ； (25) 2. The oil temperature is too low, the viscosity of the oil increases, and the friction increases ； Bearing power consumption increases ； It can also cause machine vibration. (15) 33. What factors will affect the displacement of centrifugal compressors? (35 points) Answer: 1. The inlet resistance of the air compressor increases, such as the guide vane opening is too small, valve failure and other reasons. 6 2. The resistance of the air filter and filter increases, causing the suction resistance to increase. 6 3. The compressor cooler is not effective, causing the machine efficiency to decrease. 6 4. The machine is not well sealed and leaks, and the cooler leaks, causing part of the gas to leak out. 6 5. The frequency and voltage of the power grid decrease, causing the motor speed to decrease and the exhaust volume to decrease. 6 6. As the suction temperature increases, the gas density decreases. 5 34. What precautions should be taken when filling tank trucks carrying cryogenic liquids from external units with cryogenic liquids? answer: 1 Check whether the vehicle procedures are complete. (6 points), 2. The tank truck must be in a braking state before connecting the infusion tube, and should leave in time after filling. If the filling work is interrupted for too long (overnight or on holidays), the infusion tube connection should be disconnected. (10 points). 3. Tank trucks must wear fireproof covers, and the engine of the tank truck must be turned off during filling operations. (4 points), 4 to prevent frostbite. (4 points), 5 When the valves, instruments, and connecting joints on the equipment are frozen, it is strictly forbidden to hit them with a hammer or heat them with an open flame. It is advisable to use 70 to 80°C clean and oil-free hot air, hot nitrogen, or warm water to thaw and thaw them. (6 points), 6 When filling with liquid oxygen, gloves and work clothes must not be contaminated with grease. If the clothing of the filling personnel has been penetrated by oxygen, they are not allowed to enter places with open flames and change their clothes when necessary. The blowing time in the atmosphere is not less than 15 minutes. (5 points) 35. The flange behind the stop valve behind the pressure regulating valve in the old refining and rolling area of the 20,000 pressure regulating station suddenly leaked seriously and became unusable. How to deal with it urgently? Answer (1) Quickly start the 1# and 7# nitrogen compressors in the nitrogen workshop, and then start five 1140 nitrogen compressors one after another. The old system starts to deliver low-pressure nitrogen, and the low pressure is supplemented by medium pressure. (7 points) (2) Stop the 20,000#2 nitrogen compressor or unload it (7 points). (3) Close the low-pressure nitrogen regulating valve and stop valve in the old refining and rolling area. Close the stop valve on the bridge outside the east side road. (5 points) (4) Deal with the air leakage after the pressure is released (7 points). (5) After the treatment is completed, quickly restore the gas supply to the 20,000#2 nitrogen compressor. The old system did not have enough low-pressure nitrogen. (7 points) 36. What are the steps to shut down the oxygen production system normally? (4 points for each of the first 8 answers, 3 points for the last correct answer) Answer (1) Stop operating all product compressors. (2) Open the vent valve on the product pipeline. (3) Switch the instrument air system. (4) Shut down the booster turboexpander. (5) Open the air compressor vent valve. (6) Stop the air compressor. (7) Shut down the chiller and water pump, and the water pump of the air cooling system. (8) Stop the switching system of the molecular sieve purifier. (9) Depending on the pressure, close the air and product pipelines and open the exhaust valve on the pipelines in the cold box. 37. What is the startup sequence after the oxygen production system is temporarily shut down? (5 points for each question) Answer: (1) Start the air compressor and slowly increase the pressure. (2) Start the water pump and chiller of the air pre-cooling system. (3) Put into use molecular sieve purifier. (4) Slowly supply air and pressure to the fractionating tower. (5) Start and adjust the booster turboexpander. (6) Adjust the distillation system. (7) Adjust product output and product purity to meet standards. 38. What are the starting procedures and precautions for centrifugal pumps? (Total 35 points) Answer: First make sure the outlet valve is closed and open the liquid inlet valve (15 minutes). If the pump casing is filled with liquid, when the impeller rotates, the liquid will also rotate at high speed driven by the blades. Due to the action of inertial centrifugal force, the liquid pressure at the outer edge of the impeller increases. Under the action of this pressure, if the valve is opened, the liquid will be discharged from the pressure-out pipe. This process is called the pressure-out process (5 points). At the same time, the pressure of the liquid at the center of the impeller decreases. When it has sufficient vacuum, the liquid is introduced through the suction pipe under the action of external atmospheric pressure. This process is called the suction process (5 points). As long as these two processes are not disrupted, the centrifugal pump will continuously introduce and press out liquid. It can be seen from the working process of the centrifugal pump that it must be filled with the liquid being transported and the air in the pump must be eliminated before starting. Otherwise, when the impeller rotates, since the density of air is much smaller than that of liquid, it will gather in the center of the impeller and cannot form a sufficient vacuum, which will destroy the suction process of the pump and cause the centrifugal pump to not work properly (10 points). 39. Why does the gear oil pump sometimes fail to get oil? (Total 35 points) Answer: The gear oil pump is a conversion device that converts mechanical energy into hydraulic energy through a pair of meshing gears. It is widely used in the lubrication system of air compressors. Failures in the operation of the oil pump are usually due to a decrease in oil pressure in the lubrication system and sometimes even no oil. The reasons are generally: (1) The oil suction pipeline is not tight. (7 points) (2) The oil pump has a poor seal between the pump body and the pump cover. (7 points) (3) There is insufficient oil in the oil tank. (7 points) (4) Oil pump parts are severely worn. (7 points) (5) The oil suction net is blocked. (7 points) 40. What should be paid attention to when filling the refrigerant of the piston chiller currently used in the oxygen production branch? (Total 35 points) Answer: If the unit needs to add refrigerant during daily operation, the unit should be operated at full load for a period of time (15 minutes) before adding more refrigerant. The standard is that no bubbles can be seen in the liquid surface sight glass. However, when adjusting the refrigerant filling amount, water must be continuously flowing in the condenser and evaporator to avoid freezing (15 points). Filling too much refrigerant will generate higher exhaust pressure, consume more cooling water, and may damage the compressor (5 points). 41. What are the common causes and measures for bearing heating? (Total 3 points) Answer: 1. Grease or oil is ineffective or wrongly selected. Countermeasures: Choose the correct grease or oil and check the compatibility of the grease or oil. (15 points) 2. The oil level is too low, the lubricant is lost from the oil seal, and there is insufficient grease in the bearing box. Countermeasures: The oil level should be slightly lower than the center of the lowest rolling element, and the grease in the bearing box should fill about 1/3 to 1/2 of the space. (10 points) 3. The oil level is too high or the bearing box is completely filled with grease, which will cause the lubricant to be fully stirred and cause high temperature or oil leakage. Countermeasures: Add grease into the box to 1/2 ； If the engine is lubricated by oil, the oil level should be slightly lower than the center of the lowest rolling element. (5 points) 4. The bearing clearance is inappropriate. When heat flows through the shaft center, it causes the inner ring to expand excessively. Countermeasures: Check whether the clearance of the overheated bearing is within the original design range. If so, please change to a larger clearance, change it to C3 or change C3 to C4. (5 points) 42. Analysis of the phenomenon, hazards and causes of overspeeding (speeding) of the turboexpander? (35 points) Answer: reason: (15 points) (1) Motor-braked expander: Motor outage. (2) Expander with branch brake: Brake gas valve malfunctions. Human error. Brake impeller failure. Plumbing problems. Phenomenon: (10 points) The speed rises straight up and soon exceeds the rated speed, causing screams and vibrations. The pressure behind the deflector drops and the temperature of the bearing bush increases. harm: (10 points) is a serious equipment accident, causing damage to the impeller and burning of the expander bearing alloy. Excessive speed causes impact loss and reduces efficiency. 43. What is the reason for poor oxygen purity? (35 points) Answer: Under normal operating conditions, the oxygen purity depends on the reflux ratio of the stripping section of the upper tower. As the reflux ratio increases, the oxygen purity decreases. (11 points) Reason: (1) The efficiency of the tray decreases, the tray is clogged, the tray is tilted, and the mass transfer effect is poor, etc. (4 points) (2) Abnormal distillation conditions: Flooding or leakage occurs. (4 points) (3) The condensing evaporator is working abnormally: Impurities affect the main cooling heat exchange and reduce the amount of processing air. (4 points) (4) The amount of oxygen taken out is too large: The rising gas in the upper tower is reduced and the reflux ratio is increased. Nitrogen evaporation is insufficient. (4 points) (5) LA (oxygen-containing) purity is low: The reflux ratio of the lower tower increases. (4 points) (6) The liquid oxygen level in the main condensing evaporator rises: The liquid flowing down the upper tower is too large and the reflux ratio increases. (4 points) 44. What are the factors that affect adsorption capacity? (35 points) Answer: (1) Temperature of the adsorption process. The adsorption capacity decreases with increasing temperature. (7 points) (2) Pressure. As the pressure rises, the pressure of the adsorbed component increases and the adsorption capacity increases. (7 points) (3) The degree of completeness of adsorbent regeneration. The regeneration analysis is thorough and the adsorption effect is good. (7 points) (4) The flow rate of fluid. High flow rate results in poor adsorption effect. (7 points) (5) Adsorbent bed height. High height and good adsorption effect. (7 points) 45. What are the dangers of excessively high exhaust temperature of a piston compressor? (25 points) Answer: (1) The viscosity of the lubricating oil decreases, losing the lubrication effect and causing carbon deposition, causing the valve plate or piston ring to become stuck, and even causing a burning and explosion accident. (15 points) (2) For oil-free lubrication compressors, the sealing elements may cause plastic deformation or even vaporization. (10 points) Analysis and treatment of causes of reduced exhaust volume of turbine air compressor? (25 points) Answer: (1) The voltage is insufficient and the grid frequency decreases. (Check the power supply) (5 points) (2) The intake air temperature is high. (Reduce the cooling water temperature and reduce scale) (5 points) (3) The intake pressure is low. (Check the air filter resistance) (5 points) (4) The sealing gap is too large. (Adjust the gap to prevent leakage) (5 points) (5) The cooler pipe is scaled, the heat transfer effect is reduced, and the air intake volume is reduced. (Dealing with scaling) The cooling water temperature is high. (Reduce the cooling water temperature) (5 points) 46. How to prevent explosion accidents in the heating furnace of the molecular sieve purifier? (25 points) Answer: (1) A safety valve should be installed on the heating furnace. (5 points) (2) When switching, the nitrogen inlet valve and high-pressure air inlet valve of the adsorption cartridge must be closed tightly. (5 points) (3) During installation and maintenance, the air pipelines and valves should be purged clean. Check the sealing condition of the valve and grind the damaged sealing surface to ensure its sealing performance ； (5 points) (4) When testing the pressure of the adsorption cylinder, the valve on the nitrogen outlet pipe of the heating furnace should be opened. (5 points) 47. What should be paid attention to during the storage of liquid oxygen? (25 points) Answer: (1) The liquid level of the liquid oxygen tank is controlled at 30%-95%, the liquid level of the high-purity oxygen tank is controlled at 10%-95%, and the pressure is controlled at 5-7Kpa. (5 points) (2) The C2H2 content in liquid oxygen is tested once a week and the C2H2 content is less than 0.1×10-6 (5 points) (3) Regularly (at least once a year) detect the ground resistance, the resistance value is less than 10 ohms (5 points) (4) There is no open flame within 30m. It is strictly forbidden to place flammable and explosive materials near the liquid oxygen discharge port, and warning signs must be hung. (10 points) 48. What requirements should be met for the strength and tightness test of oxygen pipelines? answer: (1) When using air or nitrogen for strength test, the pressure should be stabilized for 5 minutes after reaching the test pressure. No deformation or leakage is required to be qualified. When water is used for strength testing, it should be maintained under the test pressure for 10 minutes, and it should be qualified if there is no deformation or leakage. (15 points) (2) The tightness test should last for 24 hours after reaching the test pressure. The average hourly leakage rate of indoor and trench pipes should not exceed 0.25%. ； For outdoor pipes, no more than 5% should be considered qualified. (10 points) 49. How to determine if a water intrusion accident occurs in the molecular sieve purification system? answer: When water enters the molecular sieve purifier, the pressure fluctuates from high to low (5 points). The curve changes after the adsorber resistance increases (5 points). The most obvious is that the temperature drops after cold blowing (8 points), and a flat front appears. The longer the distance between the flat front curves, the more water enters the molecular sieve (7 points). 50. In order to prevent water intrusion accidents in molecular sieves, what should be paid attention to during operation? answer: ⑴The air cooling tower should be operated according to the operating procedures. Air should be introduced first, and water should be introduced after the pressure rises and stabilizes. (5 points) ⑵Do not increase or decrease the gas volume suddenly. (5 points) ⑶ Maintain the water level in the air cooling tower. (5 points) ⑷The amount of water spray should not be too large. (5 points) ⑸ The water quality should meet the requirements, lower the inlet water temperature and reduce scale. (5 points) 51. What are the starting conditions for an air compressor? answer: ⑴The lubricating oil pressure reaches above 0.2MPa gauge pressure. (4 points) ⑵ The cooling water pressure reaches above 0.3MPa gauge pressure. (4 points) ⑶The smoke exhaust fan is running. (3 points) ⑷The inlet blade is adjusted to the starting angle position. (4 points) ⑸The outlet vent valve is fully open. (3 points) ⑹The motor has the conditions to start. (3 points) ⑺The lubricating oil temperature reaches 35℃. (4 points) 52. Write down the main control parameters of the air separation unit, at least 5 parameters? answer: Oxygen purity ≥99.2% (5 points) Liquid air purity: 32-40% (5 points) Pressure at the bottom of the upper tower ≤ 0.06MPa (5 points) Liquid level in the lower tower ≤ 550mm (5 points) Main cold liquid level: 1900-2600mm (5 points) 53. How to start the expander? Answer: ⑴ Turn on the sealing gas supply. (2 points) ⑵ Turn on the instrument and electronically controlled air source. (2 points) ⑶ Start the oil pump. (2 points) ⑷The oil cooler is supplied with cooling water (water is supplied temporarily when the oil temperature is low), and the air cooler is supplied with cooling water. (1 point) ⑸Open the expander outlet valve. (1 point) ⑹Open the expander inlet valve. (1 point) ⑺Open the outlet valve of the supercharger. (1 point) ⑻Open the supercharger inlet valve. (1 point) ⑼Open the nozzle regulating valve at 30% of the design working condition. (1 point) ⑽Open the emergency shut-off valve, the turbine starts to run, and quickly reaches a minimum speed, and then quickly opens the large nozzle regulating valve to make the speed reach 15000r/min. (3 points) ⑾ Gradually open the nozzle regulating valve and close the supercharger return valve until the rated operating condition is reached. (3 points) ⑿ As the inlet temperature of the expander decreases, the rotation speed will decrease, which must be adjusted by closing the supercharger return valve. (3 points) ⒀Check the bearing temperature, gap pressure and overall machine operation at any time to see if they are normal. (2 points) ⒁Open the purge valve of the machine and instrument pipeline briefly, and then close it tightly. (2 points) 54. What are the factors that affect oxygen purity? answer: ⑴The amount of oxygen taken out is too large. (3 points) ⑵The oxygen purity in the liquid air is too low. (3 points) ⑶The amount of expansion air entering the upper tower is too large. (3 points) ⑷The liquid oxygen level of the condensing evaporator is too high. (4 points) ⑸ Tray efficiency decreases. (4 points) ⑹ The distillation working conditions are abnormal. (4 points) ⑺ Main cold leakage. (4 points) 55. When the compressor exhaust temperature is high, how to reduce the exhaust temperature? answer: ⑴Reduce the intake air temperature to ensure the cooling effect of the intercooler. (5 points) ⑵ The final intake temperature in the cylinder affects the exhaust temperature. The final intake temperature is related to the intake and exhaust pressure losses. Therefore, attention should be paid to valve installation and spring selection to ensure that the valve operates normally and reduces the intake and exhaust pressure losses. (7 points) ⑶ The compression process index will affect the exhaust temperature. The process index is related to cylinder cooling. The better the cooling, the smaller the index. The lower the exhaust temperature, the lower the exhaust temperature by strengthening cylinder cooling. (8 points) ⑷ Internal leakage is an important reason for excessive exhaust temperature. Therefore, it is necessary to prevent the exhaust valve from being laxly closed. (5 points) 56. How to operate the air cooling tower of 1#6000m3/h oxygen concentrator? answer start: 1) The air cooling tower pressure reaches normal value and is stable. (2 points) 2) Start the normal temperature pump, observe the bottom liquid level, and open the control valve to control it within a certain range (2 points). 3) Open the normal temperature water supply valve to the chilled water system (2 minutes). 4) The indicator light in the liquid collector in the middle of the air cooling tower goes out (2 minutes). 5) Adjust the refrigerator valve to start the freezing pump (2 minutes). 6) After normal operation, adjust the replenishing water valve to control the replenishing water volume to 2-4m3/h (2 minutes). 7) Start the freezer (2 points). shutdown: 1) Stop the freezer (2 minutes). 2) Stop the chilled water pump (2 minutes). 3) Close the normal temperature water supply valve to the chilled water system (2 minutes). 4) Stop the normal temperature water system (2 points). 5) Discharge the remaining water at the bottom and close the relevant valves (3 points). 57. How to replace the oil filter of 1#6000m3/h air compressor? answer: When the differential pressure of the 1#6000m3/h oil filter exceeds 147KPa, the oil filter should be replaced (5 minutes). The steps are as follows: (1) Open the oil filter bypass valve (4 minutes). (2) Open the drain valve of the backup oil filter and check whether the oil filter is full of oil (4 points). (3) Turn the three-way valve control lever to flow to the backup oil filter (4 minutes). (4) Close the bypass valve of the filter to be cleaned (4 minutes). (5) Open the drain valve to remove residual oil, close the drain valve, and replace the filter element (4 points). 58. What are the steps to switch the oil pump of 1#6000m3/h air compressor (Pump A is replaced by Pump B)? answer: (1) Make preparations for starting pump B and switch the oil pump interlock to the independent program of pump B (4 points). (2) Open the oil pressure adjustment screw of pump B to reduce the pressure and start pump B (4 minutes). (3) Start pump B (4 points). (4) Adjust the oil pressure, adjust the pressure of pump B to increase the pressure, and adjust the pressure of pump A to decrease the pressure and keep the oil pressure above 0.2MPa (4 points). (5) After the oil pressure adjustment is stable, stop pump A and observe the oil supply of pump B (4 points). (6) Return the A pump oil pressure adjustment screw to its original position. (5 points) 59. What are the steps for nitrogen test run of 6000m3/h oxygen compressor? answer: Preparations before operation (1) The oil pressure is not less than 0.4MPa, the oil temperature is not less than 20°C, and the oil level in the fuel tank is normal. (3 points) (2) Cranking. After cranking, the limit switch of the cranking device is closed (3 points). (3) The cooling water path is smooth (3 points). (4) Start the vacuum pump (3 minutes). (5) Close the suction emergency shut-off valve, open the nitrogen inlet valve, close the delivery valve, and open the vent valve (3 minutes). (6) The electrician sends power and allows the start light to turn on. (3 points) Start: (1) Start the compressor test run (2 minutes). (2) Use the vent valve to adjust the three-stage exhaust pressure (2 points). At the end of the test run, the nitrogen inlet valve should be closed and the suction emergency shut-off valve should be opened. (3 points) 60. What measures are taken in the 2# 6000m3/h local heating plate heat exchanger to prevent the return air from entering the heat exchanger and affecting heating? answer: The steps to prevent backflow gas from entering the heat exchanger are as follows:: (1) Close the liquid air throttle valve LCV1, liquid nitrogen throttle valve VH1, and return valve V6. (4 points) (2) Close the oxygen delivery valve FLV102A and the vent valve FLV102B. (4 points) (3) Close the PLV104 valve of the nitrogen removal water cooling tower. (4 points) (4) Close the FLV103 valve of the nitrogen removal water cooling tower, vent the HV103 valve, and transport the HV102 valve. (4 points) (5) When heating starts, use V301, V302, and V303 to control the upper tower pressure. (4 points) (6) Open the V1217 valve to increase the molecular sieve regeneration air pressure to form an air seal to prevent contaminated nitrogen from entering the molecular sieve through the plate. (5 points) 61. How to adjust the slight "nitrogen plug" in the #2 6000m3/h crude argon column? answer: During normal operation of the crude argon tower, sometimes the resistance suddenly drops, the argon content of the crude argon tower drops (2 points), and the oxygen content rises (2 points). The normal operating conditions of the crude argon tower are destroyed, which is called the "nitrogen plug" condition of the crude argon tower (2 points). Once a "nitrogen plug" occurs in the crude argon tower, the purge valve on the pipeline of the crude argon tower should be opened quickly to allow the nitrogen accumulated on the condenser side of the crude argon tower condenser to be quickly discharged into the atmosphere (5 minutes). Then, the nitrogen amount should be increased (5 minutes), the oxygen amount should be reduced and the upper tower working conditions should be reduced (5 minutes), so that the argon content of the argon fraction can gradually return to normal. (4 points) 62. The V1211 valve or V1212 valve of the 2#6000m3/h molecular sieve is not tightly closed. What measures should be taken to prevent overpressure of the electric furnace? answer: When the molecular sieve V1211 valve or V1212 valve is not closed tightly and there is slight air leakage, the regeneration program runs to pressure equalization switching. When the pressure is reduced, the electric furnace will overpressure (4 points). The following measures should be taken to prevent the electric furnace from overpressuring.: (1) Adjust the valve positioner of the FLV1201A valve, that is, the program display is zero, and there is a certain opening on site. (7 points) (2) Close the electric furnace outlet valve when the molecular sieve regeneration program reaches the start of cold blowing. (7 points) (3) Open the outlet valve of the electric furnace before the molecular sieve regeneration program reaches the end of cold blowing. At the same time, pay attention to the temperature of the electric furnace, as well as the molecular sieve regeneration temperature and flow rate. (7 points) 63. What are the safety requirements for oxygen compressors during operation and maintenance? answer: Strengthen the sealing. If the sealing stuffing box is found to be bad, it should be replaced in time. ； (4) Since pure oxygen is easy to explode and burn when in contact with oil, the oxygen compressor should be a non-lubricated oxygen compressor sealed with fluorine plastic or lubricated with water. Parts in contact with compressed oxygen must be degreased and deoiled before installation, and cleaned with carbon tetrachloride or its substitutes. ； (6) Repair personnel should keep their hands oil-free when replacing parts that come into contact with compressed oxygen. The workbench and spare parts cabinet should also be clean and oil-free. ； (5) Ensure the supply of lubricating water or cooling water. When the pressure and temperature at all levels of the oxygen compressor change, or the sound is abnormal, the relevant valves should be replaced or repaired in time. ； (5) Ensure that the safety valve is regularly inspected and the interlocking device is sensitive and easy to use. (5) 64. What main measures should be taken for the safe operation of air separation units? answer: 1) In order to prevent the accumulation of acetylene in the liquid oxygen of the full low-pressure subunit, part of the liquid oxygen should be extracted from the air separation unit, and the amount should not be less than 1% of the oxygen production. (9) 2) The acetylene and hydrocarbon content in liquid oxygen should be tested regularly. The acetylene content should not exceed 0.1PPM. The acetylene content in the liquid oxygen of the oxygen generator below 300M3/H should not exceed 1PPM. If it exceeds, it should be discharged. (8) 3) Strictly control the plate main cooling liquid level to avoid large fluctuations and adopt full immersion operation. (8) 65. Fire-prone areas in air separation plants include: answer: Oxygen compressor, liquid oxygen pump), oil system, heater, electrical switch (transformer), drive motor, electrical control cabinet, water cooling tower, workshop (warehouse), etc. (3 each) 66. Potential combustion sources in air separation units include: answer: Open flames (such as lit cigarettes, matches and cutting guns), friction within mechanical systems, impact of valves (such as switching valves), overheating caused by electrical faults, extinguished cigarette butts, power tools, metal particles entrained in high-speed airflow, heat generated during compression, etc. (3 each) 67. Which work in the oxygen plant is classified as hot work? answer: Various welding and cutting operations ； (4) Blowtorches, stoves, liquefied gas furnaces, and electric furnaces (excluding scientific research and testing) ； (4) Burning, roasting, simmering, etc., boiling asphalt, frying sand, or hammering operations that are prone to sparks ； (4) Open fire for heating and lighting ； (4) Temporary power use in flammable and explosive places and dangerous goods warehouses (including the use of electric drills, grinding wheels, pneumatic picks), etc. ； (4) Used in production areas * Tube, * * Waiting for blasting operations. (4) 68. What are the safety precautions when using warm liquid tanks? (25 points for 6 correct answers) Answer: 1) Overpressure is strictly prohibited in the tank during use. Operators must undergo systematic training, be familiar with the characteristics of liquid gases and the structure and principles of cryogenic tank trucks, be familiar with explosion-proof safety technology and fire safety regulations, and have operating certificates. During operation, operators must strictly follow the operating procedures and be able to correctly troubleshoot. 2) When the filling medium is liquid oxygen, it is strictly forbidden to use tools and protective equipment with grease, and it is strictly forbidden to use steel tools that are prone to sparks. A rubber or brass mallet should be used. 3) All valves should be opened and closed slowly to prevent them from being too fast or too fierce. The valves should not be tightened too tightly to avoid damaging the valve core. If the valve is frozen due to low temperature and is not tightly closed or cannot be opened, it is strictly forbidden to use force tools to open and close it. It should be heated with hot water before opening and closing. 4) Appropriate protective equipment, such as coarse cloth gloves, safety helmets, etc., should be worn during operation to prevent low-temperature liquids from injuring the skin. 5) If the hose interface pad is thin or not tightly closed, causing leakage, you can wrap it with black electrical tape to solve such problems. 6) Strictly pay attention to whether there is any obvious large-area "juice" phenomenon on the outer wall of the tank. If so, stop using it immediately and find out the cause in time. 7) If it is found that the pressure in the storage tank rises abnormally, you should immediately check whether the booster valve is not closed or the insulation is insufficient. If the booster valve is not closed, close it. If it is due to insulation failure, the liquid should be drained immediately and dealt with separately. 8) When out of service for a long time, the liquid in the cylinder must be drained and the vent valve slightly opened to prevent overpressure when unattended. 9) If a large amount of liquid leaks, personnel entering the site must wear long-tube respirators and protective equipment. 10) When repairing the vehicle, it should be replaced with dry hot air or dry nitrogen first. Welding can only be done when the oxygen content in the tank reaches the normal value. 11) The grounding device should be intact. It is strictly forbidden to use iron chains as grounding wires. 12) It is strictly forbidden to discharge the vehicle engine exhaust pipe to the rear of the vehicle to prevent the liquid from coming into contact with sparks when the tank, pipe, or valve leaks, causing an accident. 13) It is strictly forbidden to disassemble the hose without opening the residual liquid drain valve in the pipeline to prevent the liquid from spraying out and injuring people. 69. What safety requirements should be met when selecting and setting elbows on oxygen pipelines? answer: Oxygen pipelines are strictly prohibited from using corrugated elbows. (5) When cold bending or hot bending is used to bend carbon steel elbows, the bending radius should not be less than 5 times the outer diameter of the pipe. ； (5) When using seamless or press-welded carbon steel elbows, the bending radius should not be less than 1.5 times the outer diameter of the pipe. ； (5) When stainless steel or copper-based alloy seamless or pressed elbows are used, the bending radius should not be less than the outer diameter of the pipe. (5) The work pressure is not greater than 0. For lMpa steel plate coiled welded pipes, welded elbows with a bending radius of not less than 1.5 times the outer diameter of the pipe can be used. The inner wall of the elbow should be smooth and free of sharp edges, burrs and welding burrs. ； (5) 70. What are the safety precautions for starting and operating a large air compressor? (25 points for 5 correct answers) Answer: 1) The cartridge filter in front of the air compressor suction pipe should operate normally. 2) Large air compressors should be equipped with alarm interlocking devices such as surge, vibration, oil pressure, oil temperature, water pressure, water volume, bearing temperature and exhaust temperature according to the characteristics of the equipment. An airdrop test must be done before driving. 3) Large air compressors should be equipped with high-level oil tanks, and should be equipped with self-starting and shutdown interlock protection devices for the auxiliary oil pump when the oil pressure decreases. 4) All protective devices and safety accessories checked before driving should be in good condition, otherwise driving is strictly prohibited. 5) For large air compressor cooling water systems, the anti-water cutoff protection device must be sensitive. If the water supply is interrupted during operation, forced water supply is strictly prohibited and must be stopped for processing. 6) A large air compressor should not have more than three consecutive cold starts and no more than two hot starts. Pay attention to the startup interval. 7) When cranking, the rotor must move for at least one week. If it is the first time to drive, it should be cranked several times. If the cranking is difficult or there is a collision sound, it should be checked and eliminated. It is required to start the equipment according to the principle of "whoever turns the wheel starts." 71. What are the basic measures to prevent direct contact and electric shock? (4 each) Answer: a. Insulation ； b. Screen protection ； c. Safety distance ； d. Limit discharge energy ； e. Safety extra-low voltage 24V and below ； f. Use leakage protector for supplementary protection. 72. What is a pressure vessel? List 8 pressure vessels with different names in our factory? answer: A pressure vessel is also called a pressure vessel, which refers to a closed container with a maximum working pressure greater than or equal to 0.1Mpa (excluding hydrostatic pressure), an inner diameter greater than or equal to 0.15m, and a volume greater than or equal to 0.025m3. The medium is gas, liquids and liquefied gases with a maximum operating temperature higher than the standard boiling point. (15) Answer: Oxygen, nitrogen, argon, hydrogen storage tanks, air separation towers, air compressor gas heat exchangers, air cooling towers, molecular sieve adsorbers, etc. (10) 73. Tell us which company's products the 6000m3/h oxygen production and 20000m3/h oxygen production automation systems are, and which series they belong to? (25 points) Answer: The 6000m3/h oxygen production automation system is a product of Zhejiang University Central Control and belongs to the JX300 series. (5 points) The 20000m3/h oxygen production automation system is a Schneider product and belongs to the Quantum series. (5 points) 74. What is the fundamental difference between the 6000m3/h oxygen production automation system and the 20000m3/h oxygen production automation system? answer: The 6000m3/h oxygen production automation system is a DCS system. (5 points) The 20000m3/h oxygen production automation system is a PLC system. (5 points) 75. How does the air compressor of the 20000m3/h oxygen generating unit communicate with the monitoring computer? answer: The RS485 line drawn from the air compressor control panel (Vantage) is converted to RS232 and connected to the MODBUS PLUS port on the Schneider Quantum series lower CUP module. (5 points) Finally, it is displayed on the computer screen after software programming. (5 points) 76. How do the low-pressure and medium-pressure nitrogen compressors of the 20000m3/h oxygen generating unit communicate with the monitoring computer? answer: The RS485 lines drawn from the low-pressure and medium-pressure nitrogen press control panels are converted to RS232 and connected to the BM85 network bridge, and the outgoing lines are connected to the B+ port on the lower CUP module of the M Schneider Quantum series. (7 points) Finally, it is displayed on the computer screen after software programming. (3 points) 77. What operations can be achieved on the air compressor on the 20000m3/h oxygen production operation microcomputer? answer: It can realize chain remote unloading (3 minutes), emergency stop (3 minutes), and control DN300 anti-aircraft valve. (4 points) 78. When starting the 20000 air compressor, what are the starting conditions (sequence) displayed on the Vantage panel, and what are their values? (10 points for 10 correct answers) Answer: Oil Temperature > 20 0 Oil Temperature < 65 0 1st Stage Vibration（一级振动值） < 12 0 2nd Stage Vibration （二级振动值） < 12 0 3rd Stage Vibration （三级振动值） < 12 0 Stator Temp A （A相定子温度） < 165 0 Stator Temp B （B相定子温度） < 165 0 Stator Temp C （C相定子温度） < 165 0 IB Motor Bearing Temp（电机负荷侧轴承温度）< 100 0 OB Motor Bearing Temp（电机自由侧轴承温度）< 100 0 Emergency Stop Signal（紧急停车信号） = NORMAL 0 Oil Pressure（油压） > 0.82 10 Control Motor Enable = ON 1 Start Start Signal = 5.00 1 79. When the air compressor stops normally, what are the shutdown conditions (sequence) displayed on the Vantage panel, and what are their values? (10 points) Answer: Control Motor Enable = OFF 0 (12 points) Stopped Motor Running Signal = OFF 5 (13 points) 80. What instrumentation and control issues should be paid attention to when starting the process argon circulation pump of the 20000 unit? answer: 1. After power is sent to the inverter, local (LOC) should be displayed on the operation panel. If remote (REM) is displayed, the motor will run immediately after power is supplied. (5 points) 2. Before starting, the frequency must be reduced to about 20Hz. (3 points) 3. After the motor is running, the speed should be slowly increased or decreased. (2 points) 81. Describe respectively the oxygen, nitrogen, and argon nameplate capacity of the oxygen generator of the current oxygen production branch and the external supply capacity of the compression equipment under normal circumstances (excluding 3×1500Nm3/h oxygen generator air separation equipment). answer: oxygen: 32000Nm3/h ； Nitrogen: 39000Nm3/h ； Argon: 1070 Nm3/h (3 minutes) Oxygen external supply capacity: 4×1750Nm3/h+3×6000Nm3/h+20000Nm3/h=45000 Nm3/h (3 points) Medium pressure nitrogen external supply capacity: 5×1140 Nm3/h+7700 Nm3/h=13400Nm3/h. (2 points) Low-pressure nitrogen external supply capability: 22000 Nm3/h+7000 Nm3/h+3200 Nm3/h =32200Nm3/h. (2 points) 82. When the pressure behind the oxygen compressor and the pressure in the oxygen storage tank is 2.9MPa, and when the pressure in the medium-pressure nitrogen storage tank is 2.3MPa, what are the theoretical storage capacities of the oxygen and medium-pressure nitrogen storage systems of the oxygen production branch? answer: Oxygen is: (6×100m3+2×400m3+2×1000m3)/kg×29kg=98600m3 (5 points) Nitrogen is: (100m3+400m3)/kg×23kg=11500m3 (5 points) 83. Who are the main users of pipeline oxygen at present? What is the pressure of pipeline transportation and the approximate hourly usage? (10 points) Answer: The main ones include converter steelmaking plant (consumption of about 16000~18000m3/h), 70t electric furnace steelmaking plant (consumption of about 3500m3/h), ironmaking branch blast furnace branch (consumption of about 9000m3/h), and the third steelmaking plant (consumption of about 5000m3/h). ； The pipeline transportation pressure is set to 1.5MPa. 84. What are the nameplate outputs and pressure levels of the liquid oxygen, liquid nitrogen, and liquid argon pumps currently configured in the 20,000-ton oxygen-producing low-temperature liquid vaporization system, and what are the external air supply volumes in gaseous hours? answer: liquid oxygen: 416L/min ； The maximum outlet pressure is: 3.11 MPa ； Equivalent gas hourly flow rate: 416/1000m3×60×800=20000m3 (5 minutes) Liquid nitrogen: 257L/min ； The maximum outlet pressure is: 3.13 MPa ； Equivalent gas hourly flow rate: 257/1000m3×60×640=9868.8m3 (3 minutes) liquid argon: 800~1500L/h ； The maximum outlet pressure is: 3.13 MPa ； Equivalent gas hourly flow rate: 800~1500/1000m3×780=624~1170m3 (2 points) 85. Describe the entire start-up process and operating points of the 20,000 oxygen production low-temperature liquid oxygen vaporization system. (10 points) Answer: Refer to the "QZD22.SM Liquid Oxygen Water Bath Evaporator System Operation Instructions" 86. How to improve the economical operation of the oxygen generator. (10 points for 5 correct answers) Answer: In the cost of oxygen production, electricity consumption accounts for the main part, and the electricity consumption is mainly the energy consumed by compressed air, followed by the energy consumption of compressed oxygen and other energy consumption. Compressor energy consumption is related to the compressed air volume, exhaust pressure and compressor efficiency. Therefore, the key to improving the economy of oxygen production is to improve the management level and personnel operation level, which should start from the following aspects: a) Reduce the operating pressure of the oxygen generator to reduce the power consumption of the air compressor. b) Improve the efficiency of the compressor. c) Increase air volume. d) Improve oxygen extraction rate. e) Extend the continuous operation cycle of the equipment and reduce the startup and shutdown time. f) Reduce cooling loss. g) Comprehensive utilization to produce a variety of products. 87. What are the reasons why the pneumatic diaphragm regulating valve does not operate? answer: (2 points for one correct answer, full points for five or more correct answers) 1. Diaphragm leakage ； 2. Instrument air pressure loss ； 3. The valve is in the manual position ； 4. The feedback lever falls off ； 5. The valve stem is frozen or deformed ； 6. The solenoid valve is faulty or loses power. 88. What factors will affect the accuracy of manual oxygen purity analysis? answer: 1. Air tightness of the instrument (7 points) ； 2. Absorbents, agents and copper wire are effective (7 points) ； 3. Take samples quickly and accurately (4 points) ； 4. Analyze, shake thoroughly for absorption, and return air slowly and completely (7 points). 89. What to do after the secondary piston rod of the oxygen compressor catches fire? answer: 1. Parking (4 points) ； 2. Close the suction valve and close the exhaust valve (3 points) ； 3. Report (2 points) ； 4. Put out the fire (1 point). 90. What are the procedures for external units to transport tank trucks carrying cryogenic liquids? answer: (1) Driver’s dangerous goods transportation qualification certificate. (2 points) (2) Inspection report of the cryogenic liquid transport vehicle (there is no inspection department in Xinjiang, and our factory’s vehicle was inspected by the Gansu Provincial Boiler and Pressure Vessel Inspection Institute). (3 points) (3) The vehicle’s motor vehicle driving license of the People’s Republic of China. (3 points) (4) The qualifications of the unit where the vehicle is located. (2 points) 91. When what happens when the pressure gauge is in use, should it be stopped? (10 points) Answer: If the pressure gauge encounters any of the following conditions during use, it should be stopped and replaced with a new gauge. 1. When there is no pressure on a pressure gauge with a limited stop nail, the pointer cannot return to the limit nail. When there is no pressure on a pressure gauge without a stop nail, the value of the pointer from zero exceeds the allowable error specified by the pressure gauge. ； 2. The surface glass is broken or the scale is blurred ； The lead seal is damaged or the calibration validity period has expired ； 4. Air leakage, liquid leakage or pointer jump inside the watch ； 5. Other defects that affect the accuracy of the pressure gauge. 92. In the "Measures for the Implementation and Management of Shutdown Work Tickets" currently implemented by the branch, it is stipulated that which equipment needs to be filled in when starting and stopping work tickets? (10 points for 8 correct answers) Answer: 6000m3/h oxygen generation system air compressor oil pump 6000m3/h oxygen generation system air compressor oil filter 6000m3/h oxygen generation system air compressor oil cooler 6000m3/h air separation unit expander 6000m3/h air separation unit process argon circulation pump 300S-58 large cycle Water pump nitrogen workshop 7 # nitrogen pressure oil pump 20,000 oxygen production system air compressor oil filter 20,000 air separation unit expander 20,000 oxygen production system DFSS400-460 circulating water pump 20,000 air separation unit process argon circulation pump oxygen oil permeation pump oxygen oil permeability filter oxygen permeability oil cooler 20,000 oxygen production system nitrogen permeability oil filter 93. The tank truck was weighed and the net weight of liquid oxygen was 3420kg. How many cubic meters is it after conversion? answer: The density of liquid oxygen is 1.14kg/L. (4 points) According to density = mass m/volume v, we get v = mass m/density (4 points). v=3420/1.14＝3m3 (2 points) 94. The net weight of liquid nitrogen is 3240kg when the tank truck is weighed. How many cubic meters is it after conversion? answer: The density of liquid nitrogen is 0.81kg/L. (4 points) According to density = mass m/volume v, we get v = mass m/density (4 points). v=3240/0.81＝4m3 (2 points) 95. The net weight of liquid argon is 7000kg when the tank truck is weighed. How many cubic meters is it after conversion? answer: The density of liquid argon is 1.4kg/L. . (4 points) According to density = mass m/volume v, we get v = mass m/density (4 points). v=7000/1.4＝5m3 (2 points) 96. Valve related knowledge (10 points in total) Answer: 1. Definition of valve: Valve is a control component in a fluid delivery system. It is a mechanical product that controls fluid flow, pressure and flow direction by changing the size of its flow channel area. (4 points) 2. Definition of regulating valve: Regulating valve, also known as control valve, is a device that uses power operation to change fluid flow in a process control system. (2 points) 3. Commonly used valve and pipeline connection methods: Flange connection, threaded connection, welding. (2 points) 4. Valve transmission mode: Manual, pneumatic, electric actuators, hydraulic actuators. (2 points) 97. Name the liquid storage capacity of the oxygen plant? State the liquid storage amounts of oxygen, nitrogen, and argon in the storage tanks of each air separation unit respectively? (10 points) Answer: (1) Liquid oxygen is 1120m3, liquid nitrogen is 450 m3, and liquid argon is 470 m3, a total of 2040m3. (4 points) (2) A. The 20000 m3/h air separation unit has one 100 m3 liquid oxygen storage tank, one 400 m3 liquid nitrogen storage tank, and two 200 m3 liquid argon storage tanks. (2 points) B. The 1#6000m3/h air separation station has a 50 m3 liquid oxygen storage tank, a 50 m3 liquid nitrogen storage tank, and a 20 m3 liquid argon storage tank. The 2#6000m3/h air separation unit has a 50 m3 liquid oxygen storage tank and a 50 m3 liquid argon storage tank. (2 points) C. There is a 20 m3 liquid oxygen storage tank in front of the 1500m3/h industrial building. (2 points) 98. What is the composition principle of three-phase asynchronous motor windings? (10 points) Answer: The composition principle of the three-phase asynchronous motor winding is: The three-phase windings must be symmetrically distributed. (2 points) The conductor material, specification, number of turns, number of parallel windings, number of parallel branches, etc. of each phase must be exactly the same. (4 points) The distribution pattern of each phase winding must be exactly the same, and the spatial position of each phase winding must differ from each other by 120 electrical degrees. (4 points) 99. What are the main rated parameters of a transformer? (10 points) Answer: The main rated parameters of the transformer are:: 1) Rated capacity. 2) Rated voltage. 3) Rated current. 4) Connection group label. 5) Impedance voltage drop percentage. 6) Temperature rise. 100. Describe the meaning of grounding in electronic equipment? (10 points) Answer: There are two meanings of grounding in electronic equipment. One is to protect the safety of people and machines by connecting the metal casing of electronic equipment to the earth, which is called safety grounding. Safety grounding can prevent equipment from leaking electricity or the casing from touching a high-voltage power supply. (5 points) The other is that when electronic equipment is working and measuring, one end of the DC power supply is often used as a common potential reference point. This point is generally connected to the base plate or shell, not necessarily to the earth, which is called working grounding. Properly setting the working grounding point is one of the important methods to suppress interference. (5 points) 101. How to judge the quality of crystal diodes? (10 points) Answer: To judge the quality of a crystal diode, use a multimeter R×100 or R×1k block to measure its forward and reverse resistance. The larger the difference between the forward and reverse resistances, the better. If they are almost the same or very close, it means that the diode performance is poor or damaged. (4 points) When measuring diodes with low withstand voltage and small current, you can only use R×100 or R×1k block. If the current flowing through the diode is too large with R×1 block, if you use R×1k block, the voltage in the meter will be higher, which may damage the tube. Since the forward and reverse resistances of the diode are not constant, the measurement results using different magnification blocks are different. (4 points) When judging the polarity of a crystal diode, when the forward resistance is small, the pin connected to the black test lead is the anode of the diode, and the pin connected to the red test lead is the cathode of the diode. (2 points) 102. What causes the temperature of the automatic air switch to rise too high? (10 points) Answer: 1) The contact pressure is too small. (2 points) 2) The contact surface is excessively worn or has poor contact. (5 points) 3) The connecting screws of two conductive parts are loose. (5 points) 103. Please describe the 20000m3/h process analysis instrument: Start-up steps of the 402R-EU online total hydrocarbon analyzer. answer: Point 1 (4 points) The startup steps of the 402R-EU online total hydrocarbon analyzer are:: answer: 1. When starting, you should first check whether there are any faults and air leaks in the circuit and gas line. Once you are sure that they are correct, you can start. 2. Turn on the power, put the range switch in the "HI" position, and preheat for 2 hours. 3. Ventilate air (no hydrocarbons) during preheating, adjust the air pipeline pressure to 0.1-0.2MPa, and vent oil-free combustion gas (40% H2 and 60% N2) after venting air for 1 hour. Point 2 (3 points) 4. Adjust the combustion gas pressure to 0.04-0.05MPa. 5. After the sensor is preheated for 1 hour, the yellow heater indicator light goes out and the red flame interruption indicator light comes on, indicating that the temperature has reached the set value. Point 3 (3 points) 6. Place the switch in the IGNITE position and release it immediately when the instrument indicates that it is out of range. The flame indicator light goes out to indicate successful ignition. The switch is placed in the IGNITE position for approximately 5 seconds. 7. Adjust the sample gas pressure to 0.02-0.03MPa. Wait for the analyzer to stabilize for 4 hours before reading. Turn it on continuously. The value displayed on the dial is the total hydrocarbon content in the sample gas. 104. Can the measurement data of this instrument truly reflect the concentration at the sampling port of the air separation equipment? What data should be used to ultimately guide the analysis data of the air separation main cold effluent? answer: Point 1 (6 points) The measurement data of this instrument cannot truly reflect the concentration at the sampling port of the air separation equipment. This is because the online instrument inevitably introduces the sample gas to the entrance of the analytical instrument through a long pipeline (usually more than 5 meters at the production site). Therefore, this sampling method determines that the data provided by the online instrument can only reflect the changing trend of the gas component content under specific conditions, and cannot be treated as instantaneous real data values. Point 2 (4 points) The final guidance is that the analysis data of the air separation main cold effluent should be based on the offline analysis data. Or a hydrocarbon analysis report is also acceptable. 105. Please describe the steps to start up the Hansen Oxygen Analyzer. (2 points × 5) Answer: 1 Check whether there is air leakage at each connector of the oxygen analyzer. 2 Adjust the amount of absorption liquid. Turn the three-way piston to connect the measuring tube and the absorption bottle, and raise the level bottle to bring the liquid level in the liquid seal bottle to the appropriate position. 3 System exhaust. Rotate the three-way piston to connect the measuring tube to the outside world. Use a level bottle to adjust the liquid level to the highest point and close the three-way piston. 4 Sampling. Connect the oxygen to be analyzed to the gas pipe, open the three-way piston, allow the gas sample to pass through the gas pipe, take a certain amount of gas sample, and bring the liquid level in the gas pipe to the zero mark. 5 Absorption measurements. Turn the three-way piston to connect the measuring tube and the absorption bottle. Slowly lift the level bottle to allow all the gas samples to enter the absorption bottle. Close the tee piston, oscillate thoroughly, and return the gas to the burette. Repeat this several times until the volume remains unchanged after absorption, and read the oxygen content on the trachea. 106. Please tell us the precautions when using Han's oxygen analyzer. (Those who answer 5 questions correctly will get 10 points) Answer: 1 Since the trachea and level bottles are filled with oxygen absorbers, sampling must be done quickly. 2 When lowering the level bottle to return the gas to the measuring tube, do not do so too quickly to avoid air leakage into the analyzer. 3. When sampling, the flow rate of the gas sample should not be too high, and the pipe must be purged for a period of time before connecting it to the gas volume pipe. 4. When reading, the liquid level in the level bottle and the liquid level in the measuring tube must be kept on the same plane to make the reading accurate. 5. When the absorbent turns yellow, replace the solution immediately. When replacing, keep about 1/3 of the old solution to increase the low-priced copper in the new solution. 6. You must always pay attention to the consumption of copper wire, so that the copper wire should always be kept at about 4/5 of the capacity of the absorption bottle. 7. There should be no residual gas in the analyzer pipe to avoid analysis errors. 107. Please describe the measurement objects and usage methods of the ZO series zirconia oxygen analyzer? answer: (1) ZO series zirconia oxygen analyzer can be used to measure oxygen (constant), trace oxygen content in argon and nitrogen in liquid air. 3 points (2) cannot be used to measure flammable gases. 3 points (3) How to use: Turn on the power and the temperature will pop up. When the temperature reaches the set value, connect the sample gas, adjust the flow rate, and then the reading can be taken. 4 points 108. Please tell us the precautions for the ZO series zirconia oxygen analyzer? answer: Things to note: a. Control flow: Do not use large flow rates to avoid impact on the zirconium tube, causing rupture and damage to the zirconium tube. When measuring trace oxygen, the flow rate must be adjusted to 500ml/min. (4 points) b. Check the air tightness. (3 points) C. When measuring trace oxygen, latex tubes should not be used for connection. Metal tubes or polytetrafluoroethylene tubes should be used for connection. (3 points) 109. Basic knowledge answers: (1) Is the pressure measured by the pressure gauge the true pressure of the gas? (3 points) The pressure value measured by the pressure gauge reflects the level of pressure, but it is not the actual pressure. The pressure it measures is the difference between the actual pressure (absolute pressure) and the surrounding atmospheric pressure. (2) Pressure conversion (4 points) 1 standard atmospheric pressure (atm) = (760) mmHg = (101.3) kPa = (10.33) mH2O 1bar = (105) Pa 1psig = (0.007) MPa (3) ppm = 10-6 % = 10-2 (1 point) (4) English notes on the process analysis instrument panel (2 points) range---range oxygen----oxygen alarm-------alarm zero----zero point 110, 20000 air separation What are the items that need to be monitored? (10 points for six correct answers) Answer: Oxygen, liquid oxygen purity, nitrogen purity, pressure nitrogen, liquid nitrogen purity, lower tower liquid air purity, air outlet purifier, carbon dioxide content, product liquid argon containing nitrogen, liquid argon containing oxygen, acetylene content in liquid oxygen, total carbon content in liquid oxygen, moisture measurement 111. What are the items that need to be monitored in 6000 air separations? (10 points for six correct answers) Answer: Oxygen, liquid oxygen purity, nitrogen purity, liquid nitrogen purity, lower tower liquid air purity, air outlet purifier, carbon dioxide content, product liquid argon containing nitrogen, liquid argon containing oxygen, acetylene content in liquid oxygen, total carbon content in liquid oxygen, moisture measurement standardization 112. Please describe the startup and shutdown steps of the PMA30 high-purity oxygen analyzer. answer: Point 1: 4 points 1. Check whether there are any faults or air leaks in the circuit and gas path. After making sure everything is correct, introduce the sample gas and adjust it to 80ml/min. 2. After half an hour of ventilation, set the range range to 0-100%, then turn on the power and preheat for 2 hours. Point 2: 3 points 3 When the purity reaches above 97%, the measuring range can be placed at 97-100%. 4. After the analyzer indication is stable, the reading can be taken. Point three: When stopping at 3 minutes and 5 minutes, return the measuring range to 0-100% and turn off the power. 113. Please describe the startup steps of the D-type online trace nitrogen analyzer in argon. answer: Point 1: 4 minutes 1. Turn on the phone: Check whether there are any faults or air leaks in the circuit and gas line. After making sure everything is correct, turn on the power switch. After powering on, the instrument preheating time is 2-3 hours, and the pipeline blowing time is 24-48 hours. Point 2: 6 minutes 2 After preheating and calibration, send the gas to be measured into the analyzer and adjust the flow rate to 700cc/min. After the analyzer indication is stable, the reading can be taken.
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