Air separation commissioning specifications

KDON-550/800 Air Separation Unit Operation and Maintenance Manual 15097.SY Prepared by: Reviewed by: Approved by: Suzhou Oxygen Generator Co., Ltd. October 2010 Table of Contents 1. Overview: 1.1 Key Specifications 1.2 Basic Principles and Process 1.3 Overview of the Process Flow 2. Starting Up the Air Separation Unit 2.1 Conditions Required for Startup 2.2 Preparation for Startup 2.3 Cooling Phase 2.4 Liquid Accumulation and Adjustment Phase 2.5 Safety Measures for Operating the Unit 2.6 Important Operational Data 3. Unit Management 3.1 Normal Operation 3.2 Maintenance 3.3 Faults and Their Resolution 4. Shutdown and Heating 4.1 Shutdown and Restart 4.2 Complete Heating of the Fractionation Tower 5. Safety Regulations 5.1 Properties of Air and Its Components 5.2 Safety Precautions 5.3 Safety Measures 5.4 Use of Insulating Materials 1. Overview 1.1 Key Specifications Processed Air: Volume: 4700 Nm3/h Pressure: 0.9 Mpa(G) Products Oxygen: Production Rate: 550 Nm3/h Pressure: ≥0.2 Mpa(G) Purity: ≥99.6% O2 Nitrogen: Production Rate: 800 Nm3/h Pressure: ≥0.6 Mpa(G) Purity: ≤10 PPm O2 Liquid Oxygen: Production Rate: 30 L/h Pressure: ≥0.2 Mpa(G) Purity: 99.6% O2 Liquid Nitrogen: Production Rate: 40 L/h Pressure: ≥0.6 Mpa(G) Purity: ≤10 PPm O2 1.2 Basic Principles and Process The basic principle of air separation is to separate the various components in liquefied air based on their different boiling points. To achieve this goal, the operation of an air separation unit should include the following processes: (1) Filtration and compression of air; (2) Removal of moisture and carbon dioxide from the air; (3) Cooling the air to its liquefaction temperature; (4) Generation of cooling capacity; (5) Liquefaction; (6) Distillation; (7) Removal of hazardous impurities. 1.2.1 Filtration and compression of air: The air from the atmosphere is first filtered through air filters to remove mechanical impurities such as dust, and then compressed in an air compressor to the desired pressure. The heat generated during compression is removed by cooling water. 1.2.2 Removal of moisture and carbon dioxide from air: If moisture and carbon dioxide present in the processed air enter the low-temperature areas of air separation equipment, they will form ice and dry ice, which can block the channels of the heat exchangers as well as the small pores on the trays. Therefore, a chiller and a molecular sieve adsorber are used to remove moisture and carbon dioxide from the air in advance; the temperature of the air entering the molecular sieve adsorber is approximately 15°C. Molecular sieve adsorbers are used in pairs in rotation, with one operating while the other is being regenerated. 1.2.3 Cooling of air to the liquefaction temperature: The cooling of air takes place in the main heat exchanger, where it is cooled to a temperature close to the liquefaction temperature by the reflux gas coming from the distillation tower. Meanwhile, the cold return gas is reheated. 1.2.4 Generation of cooling capacity: Due to adiabatic losses, insufficient reheat in the heat exchanger, and the direct discharge of low-temperature fluid from the cryogenic tank, the cooling capacity required by the distillation tower is obtained through the expansion of air in the expander and the isothermal throttling effect. 1.2.5 Liquification: During the start-up phase, the process air is cooled by the returning cold air flow in the main heat exchanger and subcooler, thereby being liquefied. During normal operation, the heat exchange between nitrogen and liquid oxygen takes place in the condensation evaporator. Due to the difference in pressures of these two fluids, nitrogen is liquefied while liquid oxygen is vaporized. Nitrogen and liquid oxygen are supplied from the lower column and the upper column respectively, and this is a condition necessary to ensure the proper progression of the distillation processes in both columns. 1.2.6 Distillation The physical properties of the main components in air are shown in Tables 1-1 and 1-2. Table 1-1: Name, Chemical Symbol, Volume Percentage, Weight Percentage. Nitrogen: N2 – 78.09%, 75.5%. Oxygen: O2 – 20.95%, 23.1%. Argon: Ar – 0.932%, 1.29%. Carbon dioxide: CO2 – 0.03%, 0.05%. Helium: He – 0.00046%, 0.0016%. Neon: Ne – 0.0016%, 0.0011%. Krypton: Kr – 0.00011%, 0.00032%. Xenon: Xe – 0.000008%, 0.00004%. Table 1-2: Name, Chemical Symbol, Boiling Point (°C), Melting Point (°C), Density, Critical Point (Kg/m3, Kg/L at 10^-1 MPa). Nitrogen: N2 – Boiling point: -195.8°C, Melting point: -209.86°C, Density: 1.25, Critical point: 0.81, -147°C, 34.5. Oxygen: O2 – Boiling point: -183°C, Melting point: -218.4°C, Density: 1.43, 1.14, -119°C, 51.3. Argon: Ar – Boiling point: -186.7°C, Melting point: -189.2°C, Density: 1.782, 1.4, -122°C, 49.59. Helium: He – Boiling point: -268.9°C, Melting point: -272.55°C, Density: 0.18, 0.125, Critical point: 1251.204, -267.7°C, 2.335. Neon: Ne – Boiling point: -146.1°C, Melting point: -248.6°C, Density: 0.748, 1.204, -228.7°C, 28.13. Krypton: Kr – Boiling point: -153.2°C, Melting point: -157.2°C, Density: 1.735, 2.165, -68.7°C, 56. Xenon: Xe – Boiling point: -108.0°C, Melting point: -111.8°C, Density: 1.664, 3.52, Critical point: 16.6, 60.1. 99.04% of air consists of oxygen and nitrogen, while 0.932% is argon; these proportions remain relatively constant. Hydrogen, carbon dioxide, and hydrocarbons vary within certain ranges depending on the region and environment. The water vapor content in the air varies significantly depending on the saturation temperature and geographical conditions. Water vapor and carbon dioxide have properties that are very different from those of air. At atmospheric pressure, water vapor turns into ice at 0°C, while carbon dioxide turns into dry ice at -79°C; these substances can block the channels in plate heat exchangers as well as the small pores in sieve tray columns. Therefore, these components must be removed before air enters the cooling box. Non-condensable gases among the noble gases, such as neon and helium, have very low condensation temperatures; as a result, they remain in gaseous form within the condensing evaporator, occupying the heat exchange surface and thereby affecting the efficiency of heat exchange. Therefore, they need to be removed regularly. The separation process can yield a considerable amount of high-purity product. Air distillation takes place through the heat and mass exchange that occurs when the liquid phase of an oxygen-nitrogen mixture comes into contact with the gas phase; the liquid flows from top to bottom, while the gas flows from bottom to top, and this process is facilitated by sieve plates. Due to the different boiling points of oxygen and nitrogen, nitrogen evaporates more easily than oxygen, while oxygen condenses more easily than nitrogen. As the gas passes through the plates, the nitrogen concentration increases; with enough plates, high-purity nitrogen can be obtained at the top of the tower. Conversely, as the liquid passes through the plates, the oxygen concentration increases, allowing for the production of oxygen-rich liquid at the bottom of the lower tower and high-purity oxygen at the bottom of the upper tower. The heat and mass exchange process between the rising gas and the flowing downward liquid on the tray can be understood from Figure 1.1. The temperature T2 of the rising gas at point A on a given tray is higher than the temperature T1 of the liquid at point B, which has the same composition. Subsequent equilibrium will occur at point C on the vertical line between T1 and T2 (at temperature T3). At this temperature T3, only the liquid at point E, which has a higher oxygen concentration than that at point B, and the gas at point D, which has a lower oxygen concentration than that at point A, can reach equilibrium. As a result, the oxygen component accumulates in the flowing downward liquid, while the nitrogen component becomes concentrated in the rising gas. Through separation across sufficient numbers of trays, pure oxygen can be obtained as the liquid product, and pure nitrogen as the gas product. Figure 1.1 Oxygen-nitrogen mixture equilibrium diagram. In the lower column, air is initially separated into oxygen-enriched liquid air and nitrogen. The liquid air is drawn out at the bottom of the lower column and then sent, via throttling, to the trays in the upper column where its composition is similar to that of the liquid air; generally, the liquid air is first subcooled in a subcooler before throttling. 1.2.7 Emission of hazardous impurities Hazardous impurities in the air are hydrocarbons, particularly acetylene. During the distillation process, explosions can occur if acetylene is concentrated to a certain degree in liquid air or liquid oxygen; therefore, the concentration of acetylene in liquid oxygen is restricted to no more than 0.1 PPM, and this requires utmost attention! In the condensation evaporators and auxiliary condensation evaporators, the continuous evaporation of liquid oxygen poses a risk of hydrocarbon concentration, but this can be prevented by continuously discharging 1% liquid oxygen from the equipment. And when liquid oxygen is taken from the device, there is no need to discharge additional liquid oxygen to prevent the concentration of hydrocarbons. 1.3 Overview of the Process Flow 1.3.1 Production of Oxygen and Nitrogen (refer to the process flow diagram) Raw air is drawn in front of the suction tower, where dust and other mechanical impurities are removed via an air filter. After filtration, the air is compressed to around 0.9 Mpa (gauge pressure) using a centrifugal air compressor. The compressor is equipped with inter-stage and final-stage coolers; the compressed air, whose temperature is below 42°C, then enters the pre-cooling unit (RU1101). The saturated air temperature in this unit reaches 10°C, after which it proceeds to the molecular sieve purifier MS301 (or MS302), where carbon dioxide, hydrocarbons, and residual water vapor in the air are adsorbed. The molecular sieve adsorbers are used in pairs in rotation; while one is in use, the other is being regenerated. The switching cycle of the purifier is about 4 hours. After purification, the air has its temperature raised to 20°C; a portion of this air (900 Nm3/h) enters the pressure-increasing end of the turbine expander, where its pressure is increased to around 1.2 Mpa (absolute pressure), before it enters the distillation tower. The main heat exchanger (EH-1) is cooled by the backflow gas (pure oxygen, pure nitrogen, contaminated nitrogen), after which it enters the auxiliary condensation evaporator; there it is liquefied and then throttled to enter the lower column. Another portion is cooled to -115°C in the main heat exchanger (EH-1) by the backflow gas (pure oxygen, pure nitrogen, contaminated nitrogen), after which it is divided into two streams. One stream enters the turbine expander ET-401 (or ET-402) for expansion-based cooling; after further subcooling in a cooler, it enters the upper column. The other stream continues to be cooled in the main heat exchanger (EH-1) by the backflow gas (pure oxygen, pure nitrogen, contaminated nitrogen) to -175°C, reaching a temperature close to that of air liquefaction; after throttling, it enters the lower column. In the lower tower, the air is initially separated into nitrogen and oxygen-enriched liquid air; the rising gaseous nitrogen is liquefied in the main condensation evaporator, while the liquid oxygen on the low-pressure side of the main condenser is vaporized. Part of the liquid nitrogen is used as reflux liquid in the lower column; a small amount of another portion of liquid nitrogen is drawn from the top of the lower column and sent out of the column as a product. A third portion is cooled in a subcooler and then sent to the top of the upper column via throttling to serve as reflux liquid. Liquid air is also cooled in a subcooler and then sent to the top of the upper column via throttling to function as reflux liquid. Liquid oxygen is drawn from the bottom of the condensing evaporator and enters the auxiliary condensing evaporator, where it is vaporized by air to form pressurized gaseous oxygen; after being reheated in the main heat exchanger, it is sent outside the tower. Contaminated nitrogen gas is drawn from the top of the upper tower, and after being reheated in the subcooler and the main heat exchanger, it is also sent outside the tower. A portion of this nitrogen gas is used as regeneration gas for the purifier. Pure nitrogen gas is drawn from the top of the lower tower, and after being reheated in the subcooler and the main heat exchanger, it is sent outside the tower. 2. Startup of air separation equipment 2.1 Conditions required for startup: 2.1.1 The pipelines, machinery, electrical equipment, etc., associated with the air separation equipment must be installed and verified to be in good condition. 2.1.2 All operating machinery: air compressors, expanders, pre-cooling units, etc., shall be in condition to start, and some should have undergone individual trial runs in advance. 2.1.3 All safety valves have been tested and put into use. 2.1.4 All manual and pneumatic valves shall operate smoothly, and control valves must be tuned and calibrated. 2.1.5 The machines and instruments used are in good condition and meet the requirements for use. 2.1.6 The computer system is operating properly, displaying accurate information that matches the reality. 2.1.7 The molecular sieve purifier meets the operating conditions. 2.1.8 The piping of the low-temperature equipment inside the refrigerator has been heated and purged, and the humidity level has been verified to be satisfactory. 2.1.9 All valves of the air separation equipment are in the closed position. 2.1.10 The power supply system is operating normally. 2.1.11 The water supply system is operating normally. 2.2 Preparation for startup: Before starting up, the pipes and containers inside the cryostat must be thoroughly heated and purged (see Heating for details). There must be no liquid water or mechanical impurities in any parts that operate at low temperatures. Except for analysis instruments and measuring instruments, all valves leading to indicator instruments must be open. And carry out the following steps: 1. Start the cooling water system. 2. Start the instrument air system. 3. Start the air compressor. 4. Start the pre-cooling unit system. 5. Start the molecular sieve purification system. 6. Blow out the air ducts. 2.2.1 Starting the cooling water system 1. Notify that preparations for supplying cooling water are in place. 2. Open the cooling water inlet and outlet valves. 2.2.2 Starting the instrument air system and switching the system: 1. Turn on the backup instrument air. 2. Open each air switching valve and test the switching system program. 3. Install all instruments except for analysis and metering instruments. 2.2.3 Starting the air compressor: Refer to the “User Manual for Air Compression” for details. 1. Turn on the cooling water system. 2. Prepare the motor for starting. 3. Operate in accordance with the manufacturer’s instructions. 4. Gradually increase the pressure after the air compressor. 2.2.4 Starting the air pre-cooling system 1. Turn on the cooling water system. 2. After the air pre-cooling system pipelines are pressurized, start the air pre-cooler in accordance with the instructions provided for the air pre-cooling unit. 2.2.5 Starting the molecular sieve purification system: Please refer to the “User Manual for Molecular Sieve Purification System” for details. 1. Run the startup procedure according to the “Operating Instructions for Molecular Sieve Purification System”. 2. Open valve V601; make sure that the pressure at PI601 does not exceed 0.05 MPa before turning on the electric heating furnace. 3. The startup of the molecular sieve adsorber (including adsorption and regeneration) – gas must be supplied to the distillation column only after at least one cycle has been completed. And turn on the expander bearing air system. 2.2.6 Purge air pipeline The purpose of purging is to remove impurities and moisture. During purging, use normal-temperature dry air from the molecular sieve adsorber; each purge valve should be opened for purging until no impurities or moisture remain. The purging steps are as follows: 1. First, purge the pipelines outside the tower. Disconnect the connection to the fractionation tower, open all purging valves, and seal all pipe openings in the fractionation tower with blind plates until no dust or impurities are emitted from any of the purging ports. Connect to the fractionation tower. 2. Connect each air flow path. A. For the first path, purge the lower tower: open valves V8, V10, V13, V12, V9, V501, and V101 to purge the air circuits of the main heat exchanger, as well as the nitrogen channels of the condensing evaporator and the main heat exchanger. Be careful to control the pressure in the lower tower to prevent overpressure ； B. Second line: purging the upper tower and corresponding pipelines ； Open valves V1, V2, V104, and V105 to allow air to flow from the lower tower into the upper tower, thereby purging the oxygen channels and the nitrogen channels of the main heat exchanger. Be careful to control the pressure in the upper tower to avoid overpressure ； C. Open the instrument valves of the fractionation tower for purging. 3. Dew point analysis: Samples are taken for analysis using AIA102 and AIA101; the purging process is completed when the moisture content in the air is around 10PPM. 4. Precautions: A. During the purging of each flow path, gradually open the exhaust valve of the air compressor – this is to avoid a drop in pressure while ensuring an adequate supply of air for purging. B. Strictly control the pressure in the upper tower at ≤0.1 Mpa to avoid overpressure in it. C. When connecting the various systems, the purge valve must be opened first, followed by the inlet valve. When stopping the blowing, the inlet valve should be closed first, followed by the outlet valve. 2.3 Cooling Phase 2.3.1 Prerequisites before cooling the distillation tower 1. The air compression system is already in operation. 2. The air pre-cooling system is already in operation. 3. The molecular sieve purification system is already in operation. 2.3.2 Starting the booster turbine expander 1. Carry out the preparatory work for starting the turbine expander in accordance with the instructions provided in the \"Operation and Maintenance Manual for Turbine Expanders\". 2. Open the valves of each cooling flow path. 3. Open the valve at the pressurized end of the turbine expander to start the turbine expander. 4. Increase the air supply to the expander, gradually bringing the turbine expander to its maximum air flow rate. 5. Open the cryostat gas seal valve. 2.3.3 Cooling Fractionation Tower System The purpose of the cooling fractionation tower is to cool the low-temperature portion during normal operation from room temperature to a temperature close to that of air liquefaction, in order to create low-temperature conditions for liquid accumulation and the separation of oxygen and nitrogen. At the start of cooling, not all of the air discharged by the compressor can enter the fractionation tower; the excess air is released into the atmosphere through the discharge valve, thereby maintaining a constant pressure at the discharge outlet. As the temperatures in various sections of the distillation tower gradually decrease, the amount of air drawn in increases accordingly. The relief valve can be gradually closed down for adjustment. When the cold-side temperature of the main heat exchanger approaches the liquefaction temperature, the cooling phase can be concluded, and the liquid accumulation phase begins. Special attention should be paid to ensuring that the temperature difference between various parts inside the insulated box is not too large during the cooling process; otherwise, thermal stress will be generated. The cooling process should proceed slowly to ensure uniform temperatures throughout all parts. 1. Open the valves of the cooling circuit in sequence. 2. Maintain the exhaust pressure of the air compressor. 3. Switch the regeneration gas of the molecular sieve purifier from the air flow path to the contaminated nitrogen flow path. 4. It is necessary to pay attention to the flow rate through each channel, so as to ensure a uniform decrease in temperature across all areas, with no significant temperature differences occurring. 2.3.4 Control of the pressurized turbine expander During the cooling phase, the amount of cooling capacity generated by the turbine expander should be kept at its maximum; the temperature at the exit of the expander should be as low as possible, but it must not fall below the liquefaction temperature. In the operations at this stage: 1. Two expanders must be started sequentially. 2. The operating temperature of the expander should be as low as possible, but it must not be operated with liquid present. 3. The expander can rapidly cool the pipes and equipment inside the cold box. 4. The cooling phase comes to an end when the air at the cold end of the main heat exchanger approaches the liquefaction temperature. 2.3.5 Checking valve status 1. Status of the distillation column valves: All valves in the distillation column are closed. 2. Introduction of air: Fully open V605, V609, and V610; slowly open V9 and V10 to allow the pressure in the lower section of the column to increase gradually. 3. Activate the cooling circuit: a. For the first circuit, which is used to cool the upper tower and the oxygen channels of the main heat exchanger, open the oxygen vent valve V104. b. For the second flow path, which is the nitrogen channel of the cooling upper tower, subcooler, and main heat exchanger, open the nitrogen vent valve V101. c. Third flow path, liquid-air, liquid-nitrogen flow path: Open control valve V1. Fully open V413, V418, V419; slowly open V401 and V402. 4. Switch the gas source for regenerating the molecular sieve adsorber: When the air separation unit is started, the gas used for molecular sieve regeneration should be air that has been purified by the molecular sieve. Once the air separation unit is started and there is sufficient regeneration gas available, the contaminated nitrogen stream can be used instead as the gas for molecular sieve regeneration. 5. Start the cold box seal gas filling system. During the cooling process of the air separation unit, the temperature inside the cold box gradually decreases; it is necessary to start this system in a timely manner to prevent a negative pressure from forming inside the cold box. Open valve V203. 6. Precautions during the cooling phase: a. As the number of cooling channels increases, the air compressor should continuously increase the amount of air supplied. The outlet pressure of the air compressor should be maintained at 0.9 MPa, and the air compressor should be controlled locally. b. During the cooling process, the temperature of each part should be controlled to avoid large temperature differences. c. To accelerate the cooling rate, the refrigeration capacity of the expander should be utilized to the fullest extent. As the temperature inside the tower decreases, the degree of expansion gradually increases, thereby adjusting the operating conditions of the expander. Adhering to the principle that no liquid droplets should be generated at the expansion turbine outlet, the temperature at its exit should be reduced as much as possible. Before the temperature of the air exiting the main heat exchanger reaches 106 K, the inlet valve of the expander should be gradually opened to increase the amount of gas drawn off. d. As the temperature drops, the pressure inside the cryogenic box also decreases gradually; it is necessary to pay constant attention to adjusting the gas supply flow to the cryogenic box. 2.4 Accumulation and adjustment phase: The equipment inside all cryogenic tanks is cooled further, air begins to liquefy, and a liquid-air interface forms in the lower column. Later, the condensation evaporator also gradually produces liquid, and the distillation process in the upper and lower columns begins, with the condensation evaporator establishing a liquid oxygen level. At the same time, it is possible to start adjusting the product purity, and the product output can be set at 70% to 80% of the designed output level. During the liquefaction stage, the outlet temperature of the expander should be kept as low as possible, but not to the extent of entering the liquefaction zone. 2.4.1 Valve adjustment All valve adjustments should be carried out slowly and sequentially, step by step; the adjustment of the next valve can only begin after the adjustment of the previous valve has achieved the desired result. 2.4.2 Temperature control 1. The temperature at the cold end of the main heat exchanger should be close to the liquefaction point; TI-1 is approximately -166.2°C, while the temperature of the air in the middle section, TI-401/402, is around -110°C. 2. Other temperatures should be adjusted to the specified values during normal production. 2.4.3 Accumulation of Liquids 1. Slightly open the neon-helium purge valves V504 and V505. 2. Adjust the output of the air compressor to meet the increased air intake requirement of the distillation tower and maintain a constant pressure downstream of the compressor. 3. When there is liquid oxygen at the main cooler level, slowly close the valves of each cooling pipeline. 4. First, slightly open the liquid nitrogen reflux valve V11, and gradually increase its opening degree based on the rise in liquid oxygen level. 5. Sample and analyze the initially accumulated liquid; if impurities or solid CO2 are detected in the liquid, it should be discharged continuously until it becomes pure. Since air contains moisture, when drawing liquid samples, this moisture condenses into the liquid, causing it to become cloudy; therefore, the container used to collect the liquid should be covered. 6. Adjust the liquid-air level LI-1 in the lower column using valve V1. 2.4.4 Establishment of the distillation process 1. Install the metering instruments and control the product flow rate at 70%–80% of the design value. 2. Adjust the pressures of the upper and lower towers to normal levels. 3. The increase in the reading from the dynamometer indicates that the distillation process has begun to establish itself. a. When the level of the main liquid rises to 50%–60% or higher, the liquid nitrogen reflux valve V11 in the lower column can be gradually opened until it is fully open, thereby establishing the distillation conditions in the lower column. b. Gradually increase V1 based on the rise in the liquid level in the lower tower. c. Adjust the dirty nitrogen valves V108 or V105 at the outlet of the distillation tower, and valve V101 for pure nitrogen at the same outlet. d. Adjust the liquid-air level in the lower column using valve V1; set LI-1 to 500 mm. 4. When the liquid level in the condensing evaporator reaches the specified minimum value, the cooling capacity of one turbine expander can be reduced step by step. If the output of the air compressor has already reached its maximum value yet the pressure in the lower column continues to drop, the cooling capacity of the turbine expander should be reduced earlier. 2.4.5 Adjustment of distillation operating conditions 1. Activate the analytical instrument recorder in accordance with the manufacturer’s instructions. 2. Based on the data at each analysis point, adjust the distillation conditions using V1, V2, V9, V10, and V12. 3. During adjustment, the product is kept at around 80% of the design value when removed. 4. Once the operating conditions are stable, the amount of product taken out can be increased to the design value, thereby maintaining the purity of the contaminated nitrogen gas at the specified levels. 5. Once the output volume and purity of the product meet the specified standards, the product is gradually transferred from the vent line to the product output line. 6. Pay attention to the liquid oxygen level; it must remain stable and must not drop. If necessary, the cooling capacity of the turbine expander can be increased; the additional volume of gas from the expander should be appropriately bypassed to the nitrogen waste stream via valve V412. 7. When the designed operating conditions are reached and there is excess cooling capacity, liquid nitrogen can be extracted; by activating V8 and V13, the liquid nitrogen is sent to the cryogenic liquid storage tank, with a production rate of 40 L/h. Turn on V14 to deliver liquid oxygen to the cryogenic liquid storage tank; the liquid oxygen production rate is 30 L/h. Safety operation measures for the 2.5 unit: 2.5.1 Safe discharge of liquid oxygen – During normal operation, the safe discharge of liquid oxygen is an important measure to prevent explosions in the condenser, and it cannot be ignored. During normal operation, the auxiliary cooling system should discharge liquid oxygen once per hour, with the amount discharged accounting for approximately 1% of the oxygen produced. 2.5.2 Hydrocarbons in liquid oxygen within the condensation evaporator must be strictly controlled; tests should be conducted every 8 hours, and the results must be recorded. The maximum allowable levels of acetylene and hydrocarbons in liquid oxygen are as follows: Test point code, Chemical name, Normal value, Alarm value, Shutdown value – AE-3, as well as the lower valve of the auxiliary cooling liquid oxygen LI-3: Acetylene: 0.01 PPM, 0.1 PPM, 1 PPM; Hydrocarbons: 30 mg/L of liquid oxygen (on a carbon basis), 100 mg/L of liquid oxygen (on a carbon basis). When the levels of acetylene and hydrocarbons in liquid oxygen are too high, the following measures should be taken: 1. Conduct more tests to identify as soon as possible the cause of the increase in concentration, and take action to eliminate it. 2. Increase liquid oxygen emissions. 3. Check whether the molecular sieve adsorber is operating normally. 4. If, after taking measures, the level of acetylene or hydrocarbons continues to rise and reaches the shutdown limit, the equipment should be stopped immediately, the liquid removed, and the equipment warmed up to thaw it. 2.5.3 Charging of the cryostat: To prevent moist air from entering the cryostat and to avoid the concentration of hazardous gases within it, the cryostat must be filled with dry nitrogen as an inert gas. This nitrogen is sourced from waste nitrogen and is fed into the cryostat via V203. Under normal circumstances, if the amount of gas in the gas seal is too high and this causes an increase in pressure inside the cold box, pressure can be maintained by allowing gas to escape through the exhaust valve on the cold box. The exhaust valve should be inspected regularly; no objects should be placed on it, and it must also be protected from freezing due to ice and snow. 2.5.4 When adding preservatives to the circulating cooling water in the air pre-cooling system, the amount of preservative used must be strictly controlled to prevent excessive foaming of the water. 2.5.5 At startup or upon restarting after shutdown, it is necessary to check whether the opening positions of the inlet and outlet valves of the molecular sieve adsorber are correct; if not, they should be adjusted. The valve should be opened slowly to avoid causing shock to the molecular sieve bed. 2.5.6 When starting the comprehensive heating process after draining liquid during the cold start-up of the air separation unit, it is necessary to ensure that the amount of heating gas used is appropriate and the heating rate is slow; it is absolutely not permissible to use a large volume of gas for heating from the beginning. The heating gas should be dry air at room temperature. 2.6 Operations on Important Data The operations listed below can provide good guidance for the operator. 2.6.1.1 Pressure
Pressure at the bottom of the lower column (PI-1): 0.65 MPa(G)
Pressure at the bottom of the upper column (PI-2): 0.09 MPa(G)
Pressure at the inlet of the expander (PI-401): 0.85 MPa(G)
Pressure at the outlet of the expander (PI-402): 0.092 MPa(G)
Pressure in the auxiliary condensation evaporator (PI-3): 0.218 MPa(G)
Pressure of product oxygen (PI-102): 0.203 MPa(G)
Pressure of product nitrogen (PI-103): 0.613 MPa(G)

2.6.1.2 Temperature
Temperature at the inlet of the expander (TI-401): -110°C
Temperature at the outlet of expander ET-1 (TI-403): -157.2°C
Temperature at the outlet of expander ET-2 (TI-404): -157.2°C
Temperature of air entering the lower column (TI-1): -166.35°C
Temperature of air entering the auxiliary cooler (TI-7): -162.49°C
Temperature of air exiting the auxiliary cooler (TI-8): -164.25°C
Temperature of liquid oxygen entering the auxiliary cooler (TI-5): -176.25°C
Temperature of gaseous oxygen exiting the auxiliary cooler (TI-6): -170.25°C
Temperature of nitrogen exiting the distillation column (TI-103): 24°C
Temperature of oxygen exiting the distillation column (TI-102): 17°C
Temperature of waste nitrogen exiting the distillation column (TI-104): 17°C

2.6.1.3 Resistance
Resistance in the lower column (PdI-1): 20 KPa
Resistance in the upper column (PdI-2): 20 KPa

2.6.1.4 Liquid level
Liquid level of liquid air in the lower column (LI-1): ~500 mm
Liquid level of liquid oxygen in the condensation evaporator (LIA-2): ~1600 mm

2.6.1.5 Flow rate
Flow rate of air entering the distillation column (FI-101): 4600 Nm3/h
Flow rate of product nitrogen (FI-103): 800 Nm3/h
Flow rate of product oxygen (FI-102): 550 Nm3/h
Flow rate of regenerated gas entering the electric heater (FI-604): 1000 Nm3/h
Flow rate of pressurized air (FI-401): 900 Nm3/h

2.6.1.6 Purity
Purity of nitrogen (AAIS-601): ≤10 PPm
Purity of oxygen (AIA-602): 99.6% O2
Purity of liquid air (AE-501): 32.5% O2
Purity of liquid nitrogen (AE-502): ≤10 PPm
Purity of liquid oxygen (AE-503): 99.6% O2
The values listed represent theoretical calculations; actual values may vary during operation, and operators should adjust them to remain within specified ranges based on actual conditions. In daily operation, it is important to note: 1. Do not allow the outlet temperature of the turbine expander to reach the liquefaction range. 2. The liquid level in the condensing evaporator and on the tray should not be too high, to avoid flooding. It also cannot be too low, as this could lead to the concentration and deposition of flammable hydrocarbons. 3. Equipment Management 3.1 Normal Operation The adjustment of the air separation unit should be carried out gradually in stages. Further adjustments can only be made after the effects of a previous adjustment are evident; one should not rush things. 3.1.1 Regulation of cooling capacity The amount of cooling capacity can be determined by the fluctuations in the liquid level of the condensing evaporator. If the liquid level drops, it indicates insufficient cooling capacity; conversely, it means there is an excess of cooling capacity. The cooling capacity is primarily generated by the expander; therefore, adjusting the cooling capacity is achieved by regulating the gas flow rate to the expander. Through adjustment, the liquid level of the condensing evaporator is kept within a specified range under various conditions. 3.1.2 Distillation control 1. The liquid level in the lower column must remain stable, and this can be adjusted using valve V1 to keep it at the specified level. 2. The control of the distillation process is mainly achieved by valves V1, V2, V9, and V10; opening these valves increases the oxygen content in liquid nitrogen, while closing them reduces that content. 2. The amount of product gas removed also affects the purity of the product; as the amount removed increases, the purity decreases, while a decrease in the amount removed leads to an increase in purity. 3.1.3 Adjustment to meet specified parameters 1. Adjust all instruments to the set values. 2. Use the V2 valve to adjust the purity of nitrogen at the top of the lower column to the specified value. 3. To adjust the purity of the product gas exiting the upper tower, the amount of product taken out can be adjusted accordingly first. Once the purity is achieved, gradually increase the amount taken out until the specified criteria are met. 3.1.4 Methods to reduce production 1. Reduce the amount of air entering the distillation tower. 2. Adjust the expansion amount of the expander to reduce production. 3. Reduce the valve for removing the product gas. 4. Use valves V1, V2, V9, V10, and V12 to make appropriate adjustments to the purity. 5. Regularly check the purity and liquid level. 3.1.5 Discharge of liquids 1. The liquid discharge valve must be opened slowly. 2. After stopping the machine and before preparing to heat it, it is necessary to drain the liquid from all liquid containers and pipes, ensuring that they are completely empty. In areas where complete drainage is difficult, the liquid should be drained under pressure. 3.2 Maintenance Here, only the operation and maintenance of the main components of this device are described. For the use and maintenance of air compressors, turbine expanders, pre-cooling units, and water pumps, please refer to the respective operation and maintenance manuals. For general operations, 3.2.2 recommends establishing an operation record sheet and a maintenance log. 1. The operation record sheet is filled out once per hour, and its contents include temperature, pressure, resistance, flow rate, liquid level, analysis results, etc. The data from important automatic recording instruments should also be recorded. Record the acetylene content in the liquid oxygen of the condensation evaporator once a day. 2. The maintenance log should record the progress of the following tasks. Blow and clean all measurement pipelines once a week. Before cleaning, the pipeline controller should be removed, and the instrument zero point should be checked and recalibrated if necessary. Check whether the functions of the switching device and control instruments are normal. Inspect the air and gas filters monthly, and clean them as necessary. 3.2.2 Heat Exchangers The maintenance of heat exchange reactors focuses mainly on monitoring changes in resistance and temperature. Abnormal situations are usually caused by blockages from ice, dry ice, and powder. . This is often caused by improper equipment operation, and can be eliminated by heating and blowing out. Another thing to note is whether there are any leaks in the heat exchanger, which can be determined by analyzing whether there are differences in the composition at the inlet and outlet of the heat exchanger. The device provides many analysis points for sampling and analysis. 3.2.3 Condensing evaporator: The acetylene content in the liquid oxygen within the condensing evaporator needs to be analyzed daily. And record the results in the operation book. The acetylene content in liquid oxygen is generally below 0.01 PPm and should not exceed 0.1 PPm. Excessively high levels pose a risk of explosion; if the acetylene concentration is too high, measures must be taken to increase the discharge volume as much as possible, while also increasing the expansion volume to maintain the liquid level. Continuous analysis of the liquid oxygen in the condensation evaporator is necessary. If the acetylene concentration rises to 1 PPm, all the liquid should be drained, the system should be stopped for heating, and the molecular sieve adsorber should be regenerated. To prevent local concentration of acetylene and blockage by carbon dioxide, the plate-type unit of the condensation evaporator must be submerged in liquid oxygen; it is essential to avoid operating for long periods at low liquid levels. If the liquid level is too low, the cooling capacity should be increased immediately to raise the liquid level to the specified range; however, it should not be raised too high, as this could cause the liquid to cover the tray sheets and result in a flooded tower. 3.2.4 Distillation Tower: Differential pressure gauges are installed at the top and bottom of the distillation tower to measure the resistance during the distillation process. The resistance value measured after initial startup and once everything is adjusted properly should be used as a reference for operation. A decrease in resistance indicates either a leak or an excessively low liquid level on the tray, and it is necessary to identify the cause. If the resistance increases, it is usually due to blockage of the tray, and this situation can only be resolved by heating the distillation column. When the liquid level at the bottom of the distillation column rises too high, submerging the lowest tray, it results in column flooding. At this point, the resistance increases significantly; the liquid should be drained and then adjusted again. 3.2.5 Molecular sieve purifier: An important aspect of the management of a molecular sieve purifier is the management of the \"switching device,\" for which the instrument control manual can be referred to. The purifier should be checked once a week to verify whether the specified humidity is achieved during regeneration and cooling, and whether the switching times are in accordance with the requirements. If there are any abnormalities, adjustments should be made. After using the purifier for 1 to 2 years, it is necessary to check the degree of fragmentation of the molecular sieve particles; if needed, all the filler should be removed and screened to remove any particles. It is important to thoroughly clean and brush the filtered material to eliminate any particles and powder that may have accumulated on it. The molecular sieve must be added or replaced as specified; untested molecular sieve shall not be used first, and it is necessary to ensure that the adsorption layer reaches the specified thickness. 3.2.5 Valves: Valves used in low-temperature applications and on oxygen pipelines must be free of oil and grease. Special attention must be paid to ensuring this when maintaining and repairing these valves. If it has come into contact with oils and fats, degreasing should be performed. Gaskets and sealing rings should also be free of oil and grease, and must be made of non-flammable materials suitable for oxygen valves. The management and maintenance of valves also include keeping the visible surfaces of the valve stems clean and checking for leaks in the valves; the valve surfaces should be regularly coated with a lubricant suitable for oxygen valves. For detailed management and maintenance requirements regarding valves and specialty valves, please refer to the valve operation and maintenance manual. 3.2.7 Measurement and control devices: The management and maintenance of various instruments must be carried out in accordance with the provisions of the “Instrument Control User Manual”. The measurement pipeline requires special maintenance to ensure there are no leaks; otherwise, it will affect the accuracy of the instrument measurements and may even prevent it from functioning. It is also not allowed to measure pipeline blockages; they should be removed by heating and purging. 3.3 Faults and Their Resolution Here, only some of the faults that may occur during operation are described; other unexpected faults must be dealt with promptly by on-site personnel according to the specific circumstances. 3.3.1 Supply interruption: Signal: The air compressor alarm device sounds. Consequence: System pressure and distillation column resistance decrease. Product purity is compromised. If the product gas compressor continues to operate, it will cause a negative pressure in the distillation tower and related pipelines. Emergency measure: Stop the operation of the product gas compressor. Vent the product gas from the fractionation tower. Stop the operation of the turbine expander. Close the liquid discharge valve. Stop purifier regeneration. Further actions: Shut down the device. Troubleshooting method: Identify the cause in accordance with the operating and maintenance instructions for the air compressor, and take appropriate measures. 3.3.2 Power interruption signal: All electrically driven machines stop operating, and the alarm devices on these machines activate. Consequence: System pressure and distillation column resistance decrease. Product purity is compromised. Emergency measures: Stop the operation of the turbine expander and related machinery, and close all inlet and outlet valves. Vent the product gas from the fractionation tower. Close the liquid discharge valve. Stop purifier regeneration. Further measures: Disconnect all electrically driven machines from the power supply network. Shut down the device. Troubleshooting method: After the power supply issue is resolved and the circuit is restored, it depends on the duration of the power outage to determine whether the system needs to be reheated; follow the startup procedure to restart it. 3.3.3 Turbine expander fault signal: Alarm from the turbine expander alarm device. Consequence: Excessively high rotational speed affects the proper operation of expansion. However, if the rotational speed is too low, the cooling capacity decreases and the liquid level in the condenser and evaporator drops. Production has declined. Emergency measure: Start the standby turbine expander. Adjust the speed to stabilize the expander. Reduce the quantity of products. Check the purity of the product. Reduce product output or liquid discharge as necessary, or shut down completely. Further action: Resolve the fault immediately. Adjust the flow rate, speed, and output to normal values. Troubleshooting method: Common faults in turbine expanders are blockages caused by ice and dry ice. Heating must then be applied. As for other faults, the causes should be identified and eliminated in accordance with the operating instructions for the turbine expander. 3.3.5 Instrument air interruption signal: Alarm from the instrument air pressure alarm. Consequence: The switching device fails. All pneumatic instruments have failed. Emergency measure: Open the backup instrument air valve, and the device will resume operation. If it does not function properly, shut down the device. Further actions: If the unit continues to operate, the product purity should be checked, as well as the degree of regeneration and cooling of the molecular sieve purifier. If it is abnormal, corresponding adjustments should be made. Methods to troubleshoot the issue: The problem may be caused by a clogged instrument air filter, or by leaks in the valves and pipes. The filter should then be cleaned to eliminate the leak. 3.3.6 Pre-cooling unit fault signal: Excessively high air temperature entering the molecular sieve adsorber. Consequence: The molecular sieve adsorber cannot effectively remove moisture and carbon dioxide from the air, requiring the shutdown of the system. Measure: Shut down the unit. Method for troubleshooting: Identify the cause in accordance with the operation and maintenance instructions for the pre-cooling unit, and eliminate the fault. 4. Shutdown and Heating 4.1 Shutdown and Restart 4.1.1 Normal Shutdown Refer to: Appendix on Valve Status and Instrument Inspection. A normal shutdown should be carried out promptly by following the steps below in sequence. 1. Shut down all product compressors. 2. Open the vent valve on the product pipeline. 3. Shut down the turbine expander. 4. Open the air release valve on the air pipeline of the air compressor. 5. Shut down the air compressor. 6. Shut down the pre-cooling units and the water pumps of the water cooling system. 7. Shutdown system for the molecular sieve purifier. 8. Close the air and product pipelines, and open the exhaust valve on the pipelines inside the cold box (depending on the pressure). 9. If the vehicle is parked for an extended period, the liquid should be drained. 10. Close all valves (excluding those mentioned above). 11. Heat each device. If the parking time is short, follow only steps 1-8. Be sure to drain the water from the containers and pipes after parking when the outdoor temperature is below zero degrees, to prevent freezing. Note: Cryogenic liquids are not allowed to evaporate inside the container; when only 20% of the normal liquid level remains, it must be completely drained. 4.1.2 Temporary Parking: When a short-term stop is required to address various faults, follow steps 1–8 in section 4.1.1, and depending on how quickly the fault can be resolved, proceed to step 9 through step 11. Generally, when the parking time exceeds 24 hours, the entire system should be heated before restarting. 4.1.3 Restart after temporary parking. When the unit is restarted after a temporary shutdown, the starting point of the operation steps should be determined based on the temperature inside the cryogenic tank. The equipment inside the cold box in a refrigerated state does not need to be purged. 1. Start the air compressor and gradually increase the pressure. 2. Start the water pump and chiller of the air pre-cooling system. 3. Start the molecular sieve purification system; to ensure thorough regeneration of the other purifier, a switching cycle is required before air is fed into the distillation tower. 4. Slowly feed gas into the fractionating tower and increase the pressure. 5. Start up and adjust the turbine expander. 4.2 Heated fractionation tower: After long-term operation of the air separation unit, ice, dry ice, or hydrocarbon deposits may form in the low-temperature vessels and pipelines of the fractionation tower system, gradually increasing the resistance. Therefore, after 24 months of operation, the fractionation tower should generally be warmed and thawed to remove these deposits. If, during operation, an increase in the resistance of the heat exchanger and the distillation column is observed, to such an extent that the specified targets for yield and purity are not met, it is necessary to pre-warm and thaw the distillation column; this situation is often related to improper operation and maintenance. The heating gas is air that has been adsorbed by a molecular sieve purifier. When heating, efforts should be made to ensure that the temperature of each part rises slowly and evenly, in order to avoid temperature stress caused by large temperature differences, which could damage the equipment or pipes. During heating, all testing pipelines for temperature measurement, analysis, etc. must also be heated and purged. The above methods must be strictly followed. 4.2.1 Heating of valves All low-temperature valves can freeze due to leakage, which is often caused by a poor seal in the packing gland. Do not try to open or close a frozen valve forcefully, as this may damage it. Hot air or steam can be used to blow on the frozen parts of the valve, but when using steam care should be taken to prevent moisture from entering the stuffing box. After the valve is thawed, the source of the leak should be identified and eliminated. 4.2.2 Heating of the turbine expander Refer to the appendix on valve positions and instrument monitoring during the heating of the turbine expander. 1. Shut down the turbine expander and close all valves. 2. Open the heating valve to heat the nozzle, housing, and outlet pipe. 3. The heating process ends when the temperature of the heated gas at all outlets is close to the inlet temperature. 4. Close the heating gas inlet valve and all other valves. 4.2.3 Heating of the distillation system 1. Drain all liquids and close all valves. 2. Start the air compressor, pre-cooling unit, and molecular sieve purifier. (The amount of heated air is 30–60% of the total air volume.) 3. Open each valve according to the heating flow path. 4. When the gas temperature at each heating gas outlet rises above 0°C, open the detection line on the heating pipeline. 5. The heating is completed when the inlet and outlet temperatures of the heated gas are essentially the same. 6. Shut down the air compressor, pre-cooling system, and molecular sieve purifier, and close all valves. 4.2.4 Adsorption and regeneration of the molecular sieve purifier. For detailed instructions, please refer to the user manual for the molecular sieve purification system and the instrument control manual; only a brief explanation is provided here. 1. Regeneration: The gas is heated to a specified temperature using a heater and then fed into a molecular sieve purifier. It is led out from below and discharged to the atmosphere. 2. Cooling: Once the desired heating level is reached, the electric heater has its power turned off, and the regenerated gas is sent to the purifier for cooling. The process stops once the temperature of the regenerated gas exiting the purifier drops to the specified level. 3. Pressure increase: Before switching, all the inlet and outlet valves of the regenerated purifier are closed. Air is introduced through a balance valve to gradually increase the pressure inside the purifier; once the desired air pressure is reached, the system is switched to the air flow path for adsorption to take place. 4. Pressure relief: At this point, the pressure in the other purifier that has already been in use is gradually reduced through a small valve, after which that purifier is regenerated following the steps mentioned above. 4.2.5 Supply of heating gas: The air used for local or overall heating in this device comes from an air compressor; it is cooled by a pre-cooling unit system and dried using a molecular sieve purifier. 5. Safety Procedures: The use of air separation units must comply with safety procedures. Operators and those working in the air separation department must first learn the safety procedures and receive the necessary training. 5.1 General properties of air and its components 5.1.1 Air: Various components contained in air can be obtained through distillation after the air is liquefied. If liquid air is left in an open container for some time, nitrogen, which is more volatile, gradually vaporizes; as a result, the oxygen content in the liquid increases, and the liquid gradually takes on the properties of liquid oxygen. 5.1.2 Oxygen Oxygen is a colorless, odorless, and non-toxic gas with a strong flammability-promoting effect. The higher the oxygen concentration, the more intense the combustion. A 14% increase in the oxygen content in the air can lead to a significant intensification of combustion. Many substances, including metals, do not ignite in normal air. However, it can ignite at higher oxygen concentrations, or in pure oxygen. Therefore, flammable materials are prone to spontaneous ignition or even explosion at higher oxygen concentrations, and the situation worsens in the presence of pressurized oxygen and liquefied gases. Clothing saturated with oxygen is highly flammable (for example, due to sparks generated by static electricity) and will catch fire extremely quickly; unless the oxygen is removed, this danger will persist for a considerable length of time. 5.1.3 Nitrogen Nitrogen is a colorless, odorless, and non-toxic gas. However, at high concentrations, if inhaled by humans, it causes hypoxia and can lead to suffocation, which is very dangerous because the victim loses consciousness quickly without any prior signs of discomfort. Nitrogen can suppress combustion. Therefore, nitrogen is used in many cases as a protective gas for flammable and explosive substances. The insulation box of the air separation unit is filled with purified nitrogen to remove moisture and prevent the accumulation of oxygen. Inert gases such as argon, neon, helium, krypton, and xenon also possess properties similar to those of nitrogen. 5.1.4 Liquefied gases: The liquid form of air and its components, due to their very low temperatures, can cause severe burns similar to frostbite if they come into contact with human skin. 5.2 Safety Precautions The working area of air separation units, as well as all locations where various product gases are stored, transported, and reprocessed, must comply with the following safety precautions. 5.2.1 Prevention of fires and explosions 1. Smoking and open flames are prohibited. Activities that can generate sparks, such as welding, gas welding, and grinding with grinding wheels, are generally forbidden in the oxygen production area; if such activities must be carried out, measures must be taken to ensure that the oxygen concentration does not increase, and they can only be performed under the supervision of qualified safety personnel. 2. Do not wear shoes with nails or any steel components to avoid sparks from friction. Materials that are prone to generating static sparks should not be used for work uniforms. 3. Oil and greases must be strictly avoided; all parts that come into contact with oxygen must be completely free of oil and grease. Therefore, degreasing cleaning is necessary, and hydrochlorocarbons or hydrofluorocarbons, such as perchloroethylene, should be used for cleaning. Common substances such as trichloroethylene are not suitable for cleaning aluminum or aluminum alloys, as this can cause explosive reactions. Since such cleaners are toxic, it is necessary to ensure good ventilation, protect the skin, and wear a gas mask when using them. 4. The clothing of personnel on site must be free of oil and grease. Even fatty cosmetics can become a source of fire. 5. The clothing of personnel on site in the air separation production area must be free of oil and grease. 6. Prevent local concentration of oxygen. If certain areas are found to be concentrated or at risk of becoming concentrated, they must be clearly marked and subjected to forced ventilation. Before entering the oxygen container or pipeline, the area must be purged with oil-free air, and entry is only permitted after sampling and analysis confirm that the oxygen level is normal. 7. Personnel should avoid staying in areas with increased oxygen concentrations. If it has been left there, its clothing must have been saturated with oxygen; it should be immediately thoroughly flushed and replaced with air. 8. The opening and closing of the oxygen valve should be done slowly, avoiding rapid operations; this rule must be strictly followed especially when dealing with pressurized oxygen. 9. The concentrations of acetylene and hydrocarbons in the liquid oxygen of the condensation evaporator must be strictly controlled; see Section 2.6 for details. 5.2.2 Preventing death due to asphyxiation 1. It is necessary to prevent localized concentrations of nitrogen; if any area shows an elevated concentration or is likely to do so, it must be clearly marked and forced ventilation must be provided. 2. Personnel are strictly prohibited from entering the nitrogen enrichment area. To enter the nitrogen-enriched area, ventilation and replacement of air are required first, and entry is only permitted after thorough inspection and analysis confirm that everything is normal; this must be carried out under the supervision of safety personnel. 3. Before entering the nitrogen vessel or pipeline, personnel must undergo inspection and analysis to confirm that there is no concentration of nitrogen before being allowed to enter. It must also be carried out under the supervision of security personnel. 5.2.3 Preventing frostbite 1. When handling low-temperature liquefied gases, it is necessary to wear appropriate protective clothing and gloves; the cuffs of pants should not be stuffed into boots to prevent the liquid from coming into contact with the skin. 2. Before entering the cryogenic box of the air separation unit, the relevant sections must be heated first. 5.3 Safety Measures 5.3.1 Plant Design The plant and auxiliary buildings for air separation units must be equipped with appropriate ventilation systems. Especially in basements, pits, and passages, these areas are prone to an increase in gas concentrations. In areas where liquid oxygen may leak, the floor slabs must not be covered with any flammable materials (such as wood planks, asphalt, etc.), and they must be smooth without any joints or cracks. The sewers in the air separation unit and associated building areas must be equipped with liquid seals, as well as sufficient emergency exits. 5.3.2 Fire protection equipment: To extinguish fires promptly, adequate fire-fighting equipment should be available: 1. Special sprinkler systems that can start spraying water simply by pressing a button or when someone enters the area. 2. Fire hydrants equipped with hoses of sufficient length. 3. Equip with a convenient portable fire extinguisher. 4. A safe and reliable alarm system. 5. Place prominent warning signs prohibiting smoking and open flames in areas where oxygen levels may be high. 5.3.3 Prevention of overpressure: All containers and pipes that operate under pressure, as well as those whose internal pressure may increase, must be equipped with safety devices to prevent overpressure (such as safety valves and burst disks). These safety devices must remain in good working condition. If necessary, the setting pressure of the safety valve should be checked regularly. The alarm system must be inspected regularly. 5.4 Use of Insulating Materials 5.4.1 To maintain good insulating properties of the insulating materials inside the insulated box, inert nitrogen gas must be filled into it to prevent moisture from entering; the pressure of this inert nitrogen gas within the box should be checked regularly. 5.4.2 To prevent an increase in oxygen concentration inside the insulated container due to oxygen leakage, which could result in the insulating material becoming oxygen-rich, it is necessary to regularly check the gas composition within the insulated container. If oxygen enrichment occurs, nitrogen purging should be applied to reduce the oxygen concentration to a safe level. 5.4.3 When filling insulating materials, special masks and gloves must be used to prevent damage to the respiratory organs and skin. The sand box in the cryogenic chamber should be equipped with protective grids to prevent people or other objects from falling into it. Never step on the perlite sand piles, as this could lead to getting trapped and pose a life-threatening risk.

New version of GB50274-2010: Code for Construction and Acceptance of Refrigeration Equipment and Air Separation Equipment Installation Projects

Is there Suoyang 10000?

Reply to 2# yzlfeng: Hello, do you have an electronic version of this specification? Please send an email to zhxy20081986@126.com, thank you

Thank you all. I am looking for some professional standard documents, such as debugging workflows and the scope of debugging work. Thank you