Knowledge of safe operations in reservoir areas

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Chapter 1: Properties of Oil Products 1. What are the precautions for storing petroleum products? Answer: (1) Check the oil tank for leaks in a timely manner. (2) Prevent overheating and bumping boiling of oil, as well as emulsification that leads to oil degradation. (3) Prevent oil leakage, spilling, or mixing due to inadequate inspection. 2. What are the characteristics of petroleum products? Answer: Petroleum products are characterized by being flammable, explosive, prone to generating static electricity, and toxic and harmful to human health. 3. What are the two main elements that make up petroleum? Answer: Oil is primarily composed of two elements, carbon and hydrogen, which account for 96–99% of its total elemental composition; among these, carbon makes up 83–87% and hydrogen accounts for 11–14%. 4. What are the main production characteristics of refineries? Answer: (1) Flammable ； (2) Explosive ； (3) High temperature ； (4) High pressure ； (5) Corrosion-prone ； (6) Prone to poisoning. 5. What is the impact of the flash point of petroleum products on their storage and transportation? Answer: The risk of fire involving a petroleum product can be determined by its flash point level. Since the flash point is the lowest temperature at which a fire hazard can occur, the lower the flash point, the more flammable the fuel is, and the greater the risk of fire. Therefore, based on the flash point, various fire safety measures for its transportation, storage, and use can be determined. Chapter 2: Safe Production 6. How to prevent oil tank roof collapse accidents? Answer: (1) Strengthen a sense of responsibility; frequently measure, inspect, communicate, and keep abreast of the oil receipt situation ； (2) When the oil level in the tank approaches the safe level, it is necessary to strengthen on-site inspections and switch tanks in a timely manner ； (3) Keep track of changes in oil intake in a timely manner ； (4) Do not rely too heavily on the level gauge; when there are abnormalities in the liquid level, it is necessary to pay attention, and if needed, go up to the tank to check the level, in order to prevent the level gauge from getting stuck and failing, which could lead to overflow. 7. Why is it necessary to measure the oil tank regularly? Answer: (1) Regular measurements can promptly detect any changes in the amount of oil in the tank, preventing accidents such as spills, leaks, cross-contamination, and overflows. (2) Determine the amount of oil in and out when the tank is in motion, and assess whether the inflow and outflow are normal ； (3) Check whether there are any leaks in the oil tank heaters and coolers. 8. When using a side-depth dipstick to measure the clearance, how is the oil level determined? Answer: Until the difference between two consecutive measurements is no more than 2 mm. If the difference between the second measurement and the first measurement is greater than 1 mm, the first measurement value shall be taken as the oil level ； If the difference between the second measurement and the first measurement is greater than 1 mm, the average of the two measurements is taken as the oil level. 9. Under what circumstances is it strictly prohibited to use an oil dipstick? Answer: The dipstick must be intact when in use. In any of the following situations, it must not be used: the scale surface is twisted, bent, or has any joints ； The scale markings on the ruler are blurred or the numbers have fallen off ； Wear at the tip of the caliper hammer ； The scale markings of the ruler exceed the permissible tolerance; there is no correction table issued by a metrology authority after verification. 10. How long does it take for the liquid level to stabilize before measuring the oil tank? Why? Answer: The stabilization time of the oil surface before measuring a tank should be no less than 30 minutes. This is because, first and foremost, it is a matter of safety – the static electricity generated inside the tank after the flow of oil stops needs to dissipate completely, and it takes about an hour to reach a safe level. The second issue is accurate measurement; during the process of loading and unloading oil into the tank, there is significant disturbance in the oil inside the tank, with swirls or ripples on the liquid surface, which can cause measurement errors. Therefore, it is specified that a stabilization time of at least 30 minutes is required. 11. What is an upper sample? Answer: A sample taken at a depth equal to one-sixth of the depth below the surface of petroleum or liquid petroleum products. 12. What is a middle sample? Answer: A sample taken at a depth equal to half the depth below the surface of petroleum or liquid petroleum products. 13. What is a lower sample? Answer: A sample taken at a depth of five-sixths below the free surface of oil or liquid petroleum products. 14. What is a top sample? Answer: Sampling taken at a depth of 150 mm below the free surface of oil or liquid petroleum products. 15. What is a bottom sample? Answer: A sample taken from the bottom of the oil tank or from the lowest point in the pipeline, from the petroleum or liquid petroleum products there. 16. Under what circumstances is it prohibited to use a densitometer? Answer: The densitometer must not be used in any of the following situations: (1) The glass is cracked or scratched ； (2) The density meter scale strip is loose ； (3) Loosening of ballast metal pellets. 17. What are the methods for determining when a safety valve starts to operate? Answer: (1) Pressure gauge fluctuation ； (2) There is a beeping sound at the safety valve ； (3) It feels warm to the touch ； (4) Frosting on the pipeline of the liquid-phase safety valve trip. 18. What is the function of a drain? Answer: The function of a steam trap is to automatically remove the steam condensate from steam heating equipment or steam pipes. 19. How to use oil tanks correctly? Answer: (1) First, it is necessary to establish and improve the technical documentation for oil tanks, such as drawings and manuals. (2) Safe storage and transportation operations: Oil tanks that have been newly built or repaired must undergo pressure testing, and inspections should be carried out when receiving oil. (3) Strengthen daily inspection and maintenance management. (4) Effective measures should be taken when storing and transferring oil to reduce various forms of evaporation losses of the oil. 20. Why are heavy oil tanks, steam pipelines, and hot oil pipelines insulated? Answer: Insulation is used to reduce heat loss from heavy oil tanks, steam pipelines, and hot oil pipelines. Insulation helps save thermal energy, reduce the heating area, and lower the capacity of heating equipment. 21. To maintain product quality, what measures should be taken during the storage and transportation of oil products? Answer: (1) Strive to minimize oil evaporation losses and prevent oil from oxidizing and deteriorating ； (2) Prevent moisture and mechanical impurities from mixing into the oil; (3) Prevent oil cross-contamination and mixing ； (4) Maintaining product quality requires strict adherence to the established systems. 22. What tasks should be done on rainy days? What should be noted during operation? Answer: (1) Cover the tank’s gauging holes and sight glasses to prevent rainwater from entering the tank ； (2) Check the drainage conditions of facilities such as tank areas, storage tanks, and pump rooms, and verify whether there is any sinking of the buildings ； (3) Wear a raincoat when working outdoors; the use of umbrellas is strictly prohibited ； (4) During severe storms, outdoor work should be carried out in such a way as to prevent insulation sheets and similar items from falling and injuring people ； (5) Work on the tank top is strictly prohibited during thunderstorms and windy or rainy conditions of level 6 or above ； (6) When work must be carried out on the tank in strong wind conditions, two people must work together and effective safety measures must be taken. 23. What tasks should be carried out in snowy weather? What should be noted during operation? Answer: (1) Cover the oil measurement holes and light-transmitting holes of the storage tank ； (2) Clean the snow accumulation on the tank area, work passages, and related equipment in a timely manner ； (3) When working outdoors in heavy snowstorms, be careful to avoid being injured by falling metal sheets and other objects ； (4) During rainy or snowy weather, measures should be taken to prevent slipping and avoid injuries to people ； (5) When it is necessary to work on the tank during severe snowstorms, two people must work together and effective safety measures must be taken. 24. Why is it necessary to heat storage tanks? Answer: (1) When oil is heated, its viscosity decreases, hydraulic friction is reduced, and its fluidity increases, which facilitates oil transportation and aids in operations such as oil processing, transfer, loading, and transport ； (2) Heating can achieve demulsification, removal of water contained in the oil, and settlement of impurities, which facilitates processing in the facility, ensures product quality, and also improves measurement accuracy ； (3) Heating during oil blending facilitates convective heat transfer between light and heavy fractions, resulting in more uniform blending and ensuring the quality of the blended oil ； (4) During tank cleaning, in order to eliminate the residual oil at the bottom of the tank that has lost its fluidity, steam is often used directly for local heating, thereby helping the oil to melt and increase its fluidity, which facilitates cleaning the bottom of the tank. 25. What measures should be taken during the storage and transportation of oils to maintain product quality? Answer: (1) Strive to minimize oil evaporation losses and prevent oil from oxidizing and deteriorating ； (2) Prevent oil from mixing with water and mechanical impurities ； (3) Prevent oil cross-contamination and mixing ； (4) Maintaining product quality requires strict adherence to the established systems. 26. Under what circumstances is it necessary to purge pipelines? Answer: (1) The pipeline needs to be inspected and maintained ； (2) The type of oil in the pipeline needs to be changed ； (3) When the last tank of the same oil type within the same processing system is used up; (4) For oils that need to be heated when the temperature is below 100°C, after sales cease for the second shift on that day. 27. What are the measures to reduce evaporation losses? Answer: Based on the process by which losses occur, measures can be taken from the following aspects to reduce evaporation losses of oil products: (1) Reduce temperature fluctuations inside the tank ； (2) Increase the pressure resistance of oil tanks ； (3) Eliminate the gas space on the oil surface to prevent or minimize the release of gas outside the tank ； (4) Collect exhaled oil vapors, etc. 28. How to prevent oil tank boiling over? Answer: (1) Strictly control the storage temperature of oil products ； (2) High-temperature oils must not contain water; water must be removed from the tank regularly ； (3) Any leakage in the heater must be repaired promptly. 29. What are the anti-freezing measures for the oil unloading equipment? Answer: (1) In winter, when the pipeline is not in use, it must be purged with steam and isolated using blind flanges. (2) Dehydration should be enhanced in each oil storage tank. (3) Keep the medium in constant flow within the pipeline. (4) Maintain the flow temperature at each steam vent point. 30. How to deal with frozen condensation on valves? Answer: When thawing and dehydrating a switch, it is necessary to turn the switch off first. When using steam for heating, approach the area to be thawed slowly in order to preheat it; this prevents sudden thermal expansion due to drastic changes in local temperature, which could cause the pipes to break and lead to danger. 31. What are the measures to reduce oil product losses? Answer: (1) Minimize leaks by properly maintaining all equipment in the oil storage and transportation system, eliminate leaks, and enhance the sense of responsibility among operators to prevent oil leakage from tanks and tank trucks ； (2) Eliminate accidental oil mixing ； (3) Reduce the evaporation loss of oil products. 32. Why can heating be used to accelerate the settling rate of water in oil products? Answer: The settling speed of water in oil is proportional to the density difference between water and oil, and inversely proportional to the viscosity of the oil. It is also related to the stability of the oil-water emulsion. To increase the settling speed of water, it is necessary to reduce the viscosity of the oil as much as possible, increase the density difference between oil and water, and decrease the stability of the emulsion. By using heating, these objectives can be achieved simultaneously; therefore, the heating sedimentation method can accelerate the sedimentation rate of water in oil, facilitating its dehydration. 33. How to deal with oil freezing in pipelines? Answer: 1) For pipelines without insulation that have frozen, they can be thawed by direct heating with steam. 2) If freezing occurs due to a non-functional heat tracing line, the heat tracing line should first be repaired and put into use. 3) If only a part of an insulated pipeline has frozen, a steam line can be inserted into the insulation layer to heat and thaw it. 4) In the case of long-distance freezing of insulated pipelines, treatment should be carried out in segments. 34. What are the causes of boiling in oil tanks? Answer: When the temperature of the water droplets suspended in the oil tank rises to a high enough level, the water is heated and vaporized, forming bubbles. Since the volume of water increases rapidly to more than a thousand times its original volume when it vaporizes, these bubbles rise swiftly, causing intense stirring. This expansion in volume carries the oil out of the tank, resulting in bumping in the oil tank. 35. Briefly describe the sequence of operations and precautions for measuring oil tank levels. Answer: The sequence of operations is: first measure the length, then take the temperature or collect a sample. Precautions: Place the ruler under the reference pad, do so firmly and at an appropriate speed; read the values first as decimals and then as whole numbers, and make proper records. 36. What are the main contents of inspections in the tank farm? Answer: (1) Is the production in the tank farm operating normally, and is the process flow correct? ； (2) Are there any signs of leakage or spills? (3) Are the fire-fighting equipment in good condition? ； (4) Changes in oil level ； (5) In winter, check the tracing, anti-freezing, and anti-condensation measures ； (6) Are there any unsafe factors in the surroundings? 37. What conditions are related to the evaporative loss of oils and fuels? How is the relationship? Answer: The evaporation loss of oil is related to the storage temperature and pressure of the oil, its density, the evaporation area, as well as the relative flow velocity between the oil surface and the vapor. The higher the temperature, the greater the evaporation loss; the lower the temperature, the smaller the evaporation loss ； Losses decrease as storage pressure increases, while they increase when pressure decreases ； The higher the density of oil, the less likely it is to evaporate; the lower the density, the easier it is to evaporate ； The larger the evaporation area, the greater the evaporation; the smaller the area, the less the amount of evaporation ； The greater the relative wind speed above the oil surface, the greater the evaporation loss. 38. What are the dangers of leaks? Answer: Leaks and spills have ten major hazards: they poison the air ； Harm to the human body ； Contaminating water sources ； Corrosion equipment ； Caused the explosion ； Caused the fire ； Destroy buildings ； Increase consumption ； Dangerous agriculture ； It affects the appearance of the factory. 39. What preparations should be made before switching tanks? Answer: Before switching tanks, it is necessary to conduct a thorough and careful inspection of the process, equipment, and accessories. For the feed tank, drain water first to check the oil level. When operating the lift pipes, open the valve of the tank being switched to first, and then close the valve of the tank that is being replaced. 40. What factors determine the safe height of oil tanks? Answer: To determine the safe height of an oil tank, it is necessary to take into account the flash point of the oil stored in the tank, the tank’s capacity, the thickness of foam required for fire suppression, the location of the foam generators, as well as the minimum and maximum temperatures of the oil. 41. What are the main causes of errors in length measurement? Answer: The main reasons for errors in measurement are as follows: (1) In terms of work attitude: there is a lack of emphasis on measurement tasks; the work is done carelessly and sloppily, with no regard for quality, and things are dealt with perfunctorily, resulting in continuous mistakes ； (2) In terms of technical proficiency: a lack of specialized training in measurement techniques, low technical skill, and poor understanding of basic knowledge and operational procedures result in operations and calculations that do not meet the required standards, leading to data errors. (3) Regarding the implementation of procedures and regulations: operations are not carried out in accordance with established procedures; people try to cut corners by estimating values and oil quantities, and there is no verification of measurements ； (4) Errors in calculation: reading errors, tabulation errors, lookup errors, calculation errors, errors in transcribing records, and intentionally choosing too few digits for the calculation results, etc ； (5) In terms of measuring instruments: inappropriate selection of such instruments, insufficient precision, substandard quality; continued use of instruments that have become inaccurate or damaged over time; inadequate periodic calibration; and poor management of measuring instruments. 42. During storage and transportation, what measures are taken to prevent oil from mixing with water and impurities? Answer: (1) Keep the oil storage containers clean: That is, the containers must be washed before filling with oil, and only after inspection to confirm they meet the quality requirements of the oil to be stored can it be poured in ； Containers must be used for specific oils only; they cannot be mixed with each other ； The inner wall of the container is coated with rust-proof materials, etc ； (2) The longer the oil is stored and transported, the more precipitates are formed due to oxidation, which has a greater impact on the quality of the oil. Therefore, oil tanks should be cleaned regularly; cleaned and dried tanks and containers must be free of moisture, impurities, oil residues, and fibers, and should not leave any stains when wiped with a clean cloth ； (3) During the loading and unloading of oil products, such operations shall be halted in case of rainy, snowy, windy, or sandy weather; (4) Strengthen the storage and custody of oil products in drums. Classified storage of oil products upon arrival ； Exposed to the elements; cover with a tarp ； It should be placed at a 45-degree angle ； Install the rubber ring around the barrel opening and tighten the barrel lid ； Before pouring in the oil, clean the oil residues and dust from the mouth and surface of the tank ； Strictly control factors such as the ambient temperature of stored oil; (5) Conduct regular testing and analysis of the stored oil, and apply the first-in-first-out principle when distributing it. 43. How to prevent oil mixing during storage and transportation? Answer: To prevent oil mixing, oils should be classified and used separately according to their different properties; oils with distinct properties must not be mixed through the same pipelines. If mixing is necessary, the pipelines should be flushed with air, and where possible, with steam, followed by proper treatment of the oil ends before it can be used. 44. What are the regulations and precautions for water separation operations in oil tanks? Answer: (1) Allow 2 hours of standing time before receiving the material and after feeding it before draining the water; for heavy oils, allow 4 hours of standing time before draining the water. It is not allowed to drain the water while the material is being received or processed. (2) When cutting off water, control the opening degree of the valve to prevent oil from being carried by the vortex; if oil is detected in the water, stop cutting off the water immediately. (3) Someone must be on site to supervise the water cutting operation. (4) It is strictly prohibited to drain water from two (or more) oil tanks simultaneously. 45. Why can the water that accumulates in equipment during winter freeze and damage the equipment and pipelines? Answer: Since most materials exhibit the property of expanding when heated and contracting when cooled, water behaves in the same way at temperatures above 40°C. However, below 40°C, it shows the opposite behavior, namely expansion when heated and contraction when cooled. Therefore, water has its maximum density at 40°C. When water freezes, its volume increases by about one-tenth. Based on the elasticity of water, an increase in volume of one-tenth can generate a pressure of over 200 Mpa on the pipe walls or associated components, causing them to break. 46. Why is it necessary to dehydrate crude oil before sending it to the processing unit? Answer: Excessive water content in crude oil can lead to a high vapor phase velocity in the distillation tower, resulting in unstable operation; in severe cases, this can even cause tower flooding accidents. It also increases the load on the heaters and the top condensers, as well as the workload of the heat exchangers. Furthermore, it raises fuel consumption and cooling water usage, thereby reducing the actual processing capacity of the facility. 47. What abnormalities may occur to the oil in the tank during the heating process? How should it be handled? Answer: (1) If the oil becomes emulsified, the inlet and outlet should be closed promptly. After carefully identifying the cause, appropriate action should be taken immediately. (2) If there is oil or fire at the outlet of the heat source, it may be due to a broken heating tube; heating should be stopped immediately, and heating can resume only after the issue has been resolved. (3) The temperature drops, but both the steam inlet and outlet are open; in this case, it should be considered a heating blockage, and the system must be cleared using purging or other methods before heating can resume. 48. Why is it necessary to limit the storage temperature of oils? Answer: During storage and transportation, it is often necessary to heat the oil. As the temperature of the oil rises, its flow properties improve, but the risk of fire also increases. For light oils, the flash point is relatively low; once the heating temperature exceeds this flash point, they can easily ignite and explode when exposed to an open flame. Although the flash point of heavy oil is relatively high, its auto-ignition temperature is low; when heated beyond this temperature, it can ignite even in the presence of air. For oil products containing water, in addition to the aforementioned hazards, sudden boiling may also occur; therefore, the storage temperature must be strictly controlled and should not exceed 90°C. 49. What are the methods for dealing with overflowing oil tanks? Answer: (1) Immediately open the oil inlet line of the same tank ； (2) Pour the oil from the tank at risk of overfilling into other tanks until a safe level is reached ； (3) Organize manpower to handle the spilled oil. 50. What regulations must be followed for various oil tanks in the oil product tank farm? Answer: The “three dehydration” regulations must be implemented. (1) Dehydrate before oil recovery to prevent water from remaining at the bottom of the tank; otherwise, it may emulsify due to agitation during oil recovery, affecting measurement accuracy. (2) After oil collection, sedimentation and dehydration are carried out; moisture often exits with the oil at the outlet of the device. Once the tank is full, it needs to be left to stand for 1–4 hours to remove the moisture, thereby facilitating further processing steps. (3) Dehydration prior to transfer ensures that any residual water at the bottom of the tank is not carried over into the downstream processing steps, thereby guaranteeing the quality of the final product. 51. What is the significance of determining the density of crude oil? Answer: (1) It can be used for measurement; the weight of petroleum can be determined through volume and density ； (2) It provides certain guidance for controlling production ； (3) The value of density indicates the purity of crude oil ； (4) To a certain extent, it is possible to determine the composition and type of crude oil ； (5) It is possible to approximately assess the changes in the quality of the oil. 52. What are the causes of oil leakage accidents? How should it be prevented? Answer: During the storage and transportation of oil products, the reasons for oil leaks are roughly as follows: (1) Lack of responsibility among staff, failure to conduct inspections, or leaving post in violation of regulations ； (2) Failure to operate in accordance with the process specifications, resulting in overheating, pressure buildup, etc ； (3) Unclear instructions or inadequate communication ； (4) Leaks in valves, heating pipes, etc ； (5) Malfunction of measuring instruments ； (6) Poor quality of maintenance work ； (7) Lack of anti-freezing and insulation, resulting in the freezing and cracking of valves or oil pipes ； (8) The oil storage and transportation equipment is old and in poor condition. Safety measures to prevent oil leakage: (1) Provide operators with ideological and safety technical training ； (2) Strictly implement the post responsibility system, conduct tank measurements on time, and avoid any mistakes ； (3) Strictly follow the operating procedures; avoid exceeding temperature and pressure limits ； (4) Conduct thorough routine inspections ； (5) In the event of leaks or defects, take immediate action to resolve them ； (6) Regularly check the equipment for leaks to ensure the quality of maintenance work ； (7) Strengthen the water cutting work for storage tanks ； (8) The communication and handover with relevant personnel must be clear. 53. What are the factors that affect the ‘minor breathing’ loss in oil tanks? Answer: (1) It is related to the magnitude of diurnal temperature variations. The greater the temperature difference between day and night, the greater the loss due to \"minor respiration\" ； (2) It is related to the solar radiation coefficient of the area where the oil tank is located. The higher the solar irradiance coefficient, the greater the loss due to ‘minor respiration’ ； (3) It is related to the size of the oil tank. The larger the storage tank, the greater its cross-sectional area and evaporation area, which in turn results in higher \"minor breathing\" losses ； (4) It is related to atmospheric pressure. The lower the atmospheric pressure, the greater the ‘small breathing’ loss ； (5) It is related to the degree of filling of the oil tank. When the oil tank is full, the volume of the gas space is small, so the “minor breathing” loss is minimal ； A larger space volume means greater losses as well ； (6) It is related to factors such as the properties of the oil, including boiling point, vapor pressure, component composition, and the level of oil management. 54. What are the factors that affect the \"large breathing\" loss in oil tanks? Answer: (1) It is related to the properties of the oil. Oil has a low density; the more light fractions it contains, the greater the losses ； The higher the vapor pressure, the lower the loss ； The lower the boiling point, the greater the loss ； (2) It is related to the oil intake and output speed. The faster the oil inflow and outflow rates, the greater the losses ； (3) It is related to the pressure level inside the tank. The higher the pressure resistance of the oil tank, the lower the breathing loss ； (4) It is related to the number of times the oil tank is used. The more times the oil tank is used, the greater the \"large breathing\" loss ； (5) It is related to factors such as the geographical location of the oil tank, atmospheric temperature, wind direction, wind force, humidity, and the level of oil management. 55. Practical significance of density measurement: Answer: Density is one of the most important physical properties of petroleum and its products. It is related to the composition, so its composition can be roughly determined based on density. Density is related to other properties such as boiling range and viscosity, yielding constants that are related to the composition; for example, in crude oil classification, the value of the characteristic factor (K value) is used to determine whether the oil is paraffinic, intermediate, or naphthic ； The composition of structural families is calculated using density and other physical properties, thereby determining the type of carbon and the composition of cyclic compounds, etc. In the manufacturing process and production, volume measurement is generally used, while the actual product is measured by weight at the time of shipment and calibration; therefore, density values are essential data. Density is one of the key parameters for controlling petrochemical products; for example, it determines the purity of benzene-based products. The density of jet fuel is related to its range of flight. By measuring the density of oils or chemical raw materials of the same type, it is possible to determine differences in their composition and distillation ranges, thereby assessing their suitable applications. 56. Precautions for using a petroleum densitometer: Answer: The densitometer is a fragile glass instrument, so it must be handled with care during use. It should be wiped with absorbent cotton or other soft materials. Apart from holding the upper part of the densitometer with your hands when inserting or removing it (make sure to do this vertically), its lower part should be removed during cleaning to prevent it from breaking. Samples with large temperature differences or those taken from refrigerated containers should be left at the measurement ambient temperature for a period of time to eliminate errors that could affect the results. For products with viscosity and that are solid at room temperature, in order to obtain accurate data, they are heated and melted in an electric furnace oven and then poured into a measuring cylinder. The cylinder containing the oil sample is placed in a constant-temperature water bath, and measurements are taken once the temperature has reached equilibrium. The melted sample cannot be poured into a measuring cylinder and immediately measured at room temperature, as a large temperature difference will result in overly high values. 57. The significance of measuring residual carbon: Answer: Residual carbon is related to unstable hydrocarbon compounds, polycyclic aromatic hydrocarbons, and non-hydrocarbon compounds in oils; it is particularly closely associated with asphaltenes and resins in heavy oils. For lubricant fractions, the carbon residue value reflects the degree of refinement, and carbon residue is one of the important indicators in the production process; it is also one of the specification requirements for commercial lubricants. 58. What is the significance of measuring the viscosity of petroleum products for production and use? Answer: The viscosity of oils generally increases as their boiling range increases. However, fractions within the same boiling range have different viscosities due to their varying chemical compositions. Among the hydrocarbons in oils, alkanes have the lowest viscosity, while cyclic hydrocarbons with long side chains or multiple side chains have the highest viscosity. Therefore, the degree of refinement of the lubricating oil is determined during the production process by analyzing viscosity control. Generally, the viscosity of the unrefined fraction is greater than that of the fraction refined with sulfuric acid, and the viscosity of the fraction refined with sulfuric acid is greater than that of the fraction oil refined with a selective solvent. Viscosity is one of the important parameters of diesel; it determines the atomization and combustion of diesel in internal combustion engines. High viscosity leads to poor atomization; insufficient mixing with air results in incomplete combustion. At the same time, diesel acts as a lubricant for plunger pumps; if its viscosity is too low, it will affect the lubrication of the oil pump and increase plunger wear. 59. The importance of determining the pour point of petroleum products in production and usage. Answer: For wax-containing oils, the pour point can serve as an indicator for estimating the paraffin content. The higher the paraffin content in the oil, the easier it is to solidify. If 0.1% paraffin is added to the oil, the freezing point rises by about 9–13 °C; conversely, removing paraffin from the oil results in a significant decrease in the freezing point. The freezing point is used to indicate the grade of diesel; for example, the freezing point of No. 0 diesel should not be higher than 0°C, while that of No. -10 diesel should not be higher than -10°C. Furthermore, the freezing point is also related to the lowest temperature at which diesel can flow smoothly through the engine’s fuel system; solid paraffin particles that form at low temperatures can clog the fuel filter and disrupt the fuel supply. 60. What is the significance of determining the flash point of petroleum products for production and application? Answer: The flash point of a petroleum product allows one to determine the lightness or heaviness of its distillate composition. Generally, the higher the oil vapor pressure and the lighter the distillate composition, the lower its flash point. Conversely, the heavier the distillate composition, the higher its flash point. During the production process in atmospheric and vacuum distillation units, the flash point is controlled to adjust the operating conditions of the side streams, thereby producing qualified distillates. The flash point can be used to determine the fire hazard of oils. Since the flash point is the lowest temperature at which a fire hazard occurs. The lower the flash point, the easier it is to ignite, and the greater the fire hazard. Therefore, flammable liquids can also be classified according to their flash point. Liquids with a flash point below 45°C are called flammable substances, while those with a flash point above 45°C are called combustible substances. Based on the flash point, various fire safety measures for transportation, storage, and use can be determined. 61. What is the significance of determining the water content in petroleum products for production and application? Answer: The oil supply tank measures the actual data of the oil product. By subtracting the moisture content after measuring, the actual amount of oil in the entire container can be determined. The moisture content in the oil product is measured, and based on this level of moisture, a dehumidification method is determined to prevent the following hazards: (1) When moisture in petroleum products evaporates, it absorbs heat, which reduces their calorific value. (2) Moisture in light oils can deteriorate the combustion process. It can also bring dissolved salts into the cylinder, resulting in carbon buildup and increased wear on the cylinder. (3) At low temperatures, the moisture in the fuel freezes, blocking the fuel lines and filters and interfering with the fuel supply to the engine’s fuel system. (4) When there is moisture in petroleum products, it accelerates the oxidation and gelation of the oils ； (5) Water in the lubricating oil can cause corrosion of engine components during use; at high temperatures, it can destroy the oil film on the metal surface, leading to wear. 62. What are the disadvantages of thiols in petroleum products? Answer: Gasoline contains a high amount of thiol compounds, which not only produce an unpleasant odor but also reduce the stability of the fuel. Because thiol is an oxidation initiator that can cause unstable compounds in oils to oxidize and polymerize, forming gel-like substances. Thiols are also corrosive and can increase the corrosivity of elemental sulfur. In addition, thiols also affect the sensitivity of petroleum products to additives such as anti-knock agents and antioxidants. From an environmental perspective, using gasoline containing more mercaptans increases the emissions of SO2 and SO3 from vehicles, thereby exacerbating air pollution. 63. What is the reaction mechanism for the sweetening of gasoline? Answer: The reaction mechanism for the desulfurization of gasoline is an anion-radical reaction mechanism. Its kinetic process is as follows: RSH + OH⁻ → RS⁻ + H₂O; Catalyst + 1/2 O₂ → RS⁻ → RS˙ + Catalyst + 1/2 O₂⁻²; RS˙ + RS˙ → RSSR; O₂⁻² + H₂O → 2 OH⁻ + 1/2 O₂. Initially, the mercaptans in the oil come into contact with NaOH, resulting in the formation of sodium mercaptide, which then dissociates into the mercaptide anion RS⁻. Meanwhile, molecular oxygen forms an unstable active complex with the catalyst. The reactive complex and the thiolate anion RS− undergo a single-electron transfer reaction to produce the thiol radical RS•. The two thiol radicals quickly combine to form a stable disulfide RSSH. The chemical equation for the sweetening of gasoline is: 2RSH + O2 = RSSR + H2O. 64. What are the catalyst, cocatalyst, and carrier used in the solid-bed gasoline sweetening process? Answer: The main catalyst is cobalt polyphtalocyanine or sulfonated cobalt phthalocyanine ； The catalyst is a NaOH solution ； The carrier is activated carbon or molecular sieve. 65. What effect does temperature have on the solubility of cobalt polyphthalocyanine? Answer: If the temperature is too high, it will undermine the stability of cobalt phthalocyanine in alkaline solutions, thereby reducing the efficiency of desulfurization. The experimental data is shown in the table. Dissolution temperature/°C: 20, 40, 60, 88. Thiol removal rate/%: 74, 74.5, 77, 66.5. What is the effect of NaOH concentration on the thiol removal rate of cobalt phthalocyanine polymer? Answer: The experimental data is shown in the table below. As can be seen from the table data: an increase in NaOH concentration is beneficial for the sweetening reaction; however, excessively high concentrations lead to salting out, thereby reducing the reaction efficiency. NaOH concentration/% 5 10 20 40 Thiol removal rate/% 75 83 75 67 67. What is the effect of the temperature used in the desulfurization of gasoline on the thiol removal rate? Answer: The effect of the gasoline desulfurization reaction temperature on the thiol removal rate is shown in the table below. As can be seen from the data in the table, a reaction temperature of 40 degrees Celsius is appropriate, as gasoline volatilization is also low at this temperature. Reaction temperature/°C: 20, 30, 40, 50, 60; Thiol removal rate/%: 83, 91.7, 93.7, 88, 74, 68. What is the impact of the air/oil ratio on gasoline desulfurization? Answer: Under certain operating conditions, the effect of the air/oil ratio on gasoline desulfurization is shown in the table. As can be seen from the data in the table. When the air/oil ratio is greater than 1:1, it has very little effect on the sweetening of gasoline. In production, a large amount of air not only causes gasoline to oxidize and change color, but also increases the loss of light components through volatilization. The actual air/oil ratio for desulfurization of alcohols in the catalytic unit of the Shanghai Refinery is only 1:39. Wind/oil (ratio): 1:1, 1:10, 1:20, 1:30. Thiol removal rate/%: 86.8, 87.5, 86.6, 86.5. 69. What is a Doctor solution? Answer: Dissolve 25 g of lead acetate (containing three molecules of water of crystallization) in 200 ml of water. Filter this solution into an aqueous solution containing 60 g of sodium hydroxide in 100 ml of water. The resulting solution is then referred to as the “Doctor’s Solution”. 70. What is the博士 test? Answer: When an oil product containing thiols is mixed with the Baas test solution, a certain amount of sulfur is added. After shaking for 15 seconds, the mixture is allowed to stand for 1 minute. If the interface appears brownish-yellow or brown, it indicates the presence of thiols in the oil product; in this case, the Baas test fails, and this is denoted by “+” ； Conversely, compliance is indicated by “—”. The reaction in the doctoral experiment is as follows: Pb(OH)2 + 2RSH → (RS)2Pb + 2H2O. Lead thiol ((RS)2Pb) + S → RSSR + PbS ↓ disulfide. 71. How should a fixed-bed reactor be prepared for the desulfurization of gasoline using thiol? Answer: Place 4–8 kg of cobalt polyphthalocyanine into an enameled bucket, then pour in a dilute alkaline solution at a concentration of 5% and a temperature of 50–60 degrees Celsius. Stir with a rod to dissolve it. The amount of alkali solution should not be excessive; just enough to dissolve cobalt phthalocyanine is sufficient. Prepare 10 m3 of an alkaline solution with a concentration of 10%, pour the dissolved catalyst into it, start the alkaline pump to circulate the mixture, and stir thoroughly to ensure uniform distribution. It is then drawn into the reactor for circulation, allowing the catalyst to be immersed and adsorbed on the activated carbon. When the lye turns yellow, the soaking is complete. Pump the alkaline solution from the reactor into another container. 72. How is the solid-bed sweetening reaction regenerated? Answer: Drain the oil and waste alkali solution separately; then use water to flush out the oil from the reactor, and finally introduce steam to steam the tank. After maintenance, the fixed-bed reactor is re-soaked with newly prepared catalyst alkali solution. After soaking is complete, the reactor is regenerated. Based on the experience of the refinery at Shanghai High Chemicals Company, the lifetime data for the gasoline desulfurization catalyst, cobalt polypyrrophosphate, is 90,000 tons of gasoline per kg of catalyst. If the service life of cobalt phthalocyanine is exceeded, the solid-bed reactor needs to be regenerated. 73. What is the alkali-free liquid fixed-bed deodorization method? Answer: In the alkali-free fixed-bed deodorization method, the preparation of the catalyst is the same as that in the conventional Merox fixed-bed deodorization method; it is prepared using activated carbon as a carrier through an impregnation process. During operation, 10–20 ug/g of activator is added to the gasoline, which serves as the material to be deodorized. The activator is miscible with oil; it acts as a base during the deodorization process and also prevents contamination of the catalyst bed, remaining ultimately in the deodorized oil. Throughout the deodorization process, no alkaline liquid phase appears, and no alkaline liquid is discharged. Therefore, the alkali-free deodorization process is a clean deodorization method that produces almost no pollutants. However, the cost of the activator it uses is high. 74. Why is the thiolic sulfur content in denatured gasoline below 10 ug/g, yet it fails the Drabek test? Answer: The Drabert test is a qualitative method for detecting thiol compounds, and it is used by many **to examine thiols in fuels. For example, gasoline grade 90 requires passing the Drabek test or having a thiol sulfur content (SRSH) of less than 10 ug/g. But these two indicators are not exactly the same. Sometimes, the SRSH level is below 10 ug/g, or even below 4 ug/g, yet the Dr. test fails, which directly affects the export of No. 90 gasoline in our country and results in huge economic losses. According to the mechanism of thiol oxidation, the oxidation of thiols to disulfides involves two steps: RSH + OH- → RS- + H2O (1) (oil phase) (alkaline phase); 2RS- → RSSO2 (2). The presence of an alkali is essential during the deodorization process. Whether it is the Merox liquid/liquid method or the conventional fixed-bed deodorization method, it is necessary for the thiol to transfer from the oil phase to the alkali phase, thereby forming a thiol anion, i.e., reaction (1), followed by an oxidation reaction (2). For lower alkanethiols, due to their good solubility in alkalis, reactions (1) and (2) occur easily; therefore, these two deodorization processes are effective for removing lower alkanethiols. However, for higher thiols, due to their low solubility in alkalis, they do not easily transfer from the oil phase to the alkaline phase; as a result, these two deodorization processes are less effective at removing higher thiols. Thiols with different structures exhibit varying sensitivities in the Drucker test. Generally speaking, lower thiols are less sensitive to the Drabkin test, while higher thiols are more sensitive to it. When gasoline contains 1.5 ug/g of dodecanethiol, its Drabek test yields a positive result (unqualified). Regarding the distribution of thiolic sulfur in the deodorized gasoline, higher thiols are the main components of the trace thiols present in it. Therefore, at present, in some domestic refineries, when the thiolic sulfur content in the degassed gasoline is below 10 ug/g, the Drabek test fails. 75. What is the “minor breathing” loss of oil tanks? Answer: When a oil tank is stored stationary, the loss caused by the day-and-night variations in the temperature of the gas space inside the tank is known as the “minor breathing” loss of the oil tank. 76. What are the contents of the “five no’s” in the post responsibility system? Answer: (1) If the equipment issue is unclear, do not connect ； (2) Do not accept tasks if the orders issued by the workshop have not been completed ； (3) Jobs will not be accepted if the work area is not clean ； (4) Records that are unclear, incomplete, or inaccurate will not be accepted ； (5) Production is abnormal; no connection will be made if accidents are not addressed. 77. What are the contents of the “ten handovers” during shift change? Answer: The ten aspects of handover refer to: handing over tasks, instructions, raw materials, operational parameters, quality standards, equipment, problems and experiences, safety measures, tools, and hygiene requirements. 78. What tasks need to be carried out during shift handover? Answer: During shift handover, it is necessary to achieve “three ones,” “four arrivals,” and “five reports.” “\"Three ones\" means handing over important production areas one by one, transferring key production data item by item, and delivering major production tools one at a time. “The four ‘dos’ mean that one should see what needs to be seen, touch what needs to be touched, hear what needs to be heard, and smell what needs to be smelled. “The “five reports” refer to reporting the inspection location, the safety status, the production status, the existing problems, and the measures taken. Chapter 3 Equipment Operation 79. What is the function of a pump? Answer: It converts the mechanical energy of the prime mover into energy of the liquid being transported, thereby increasing the flow rate and pressure of the liquid. 80. What is the working principle of a centrifugal pump? Answer: The working principle of a centrifugal pump is as follows: the drive mechanism causes the impeller to rotate at high speed, thereby generating centrifugal force. Under the action of this centrifugal force, the liquid is forced along the blade channels toward the outlet of the impeller. At the same time, a low-pressure area is formed at the center of the impeller inlet; under the effect of this pressure difference, the liquid at the center of the suction pipe continuously flows through the suction pipeline and the pump’s suction chamber into the impeller. In general, a centrifugal pump works by continuously drawing in liquid due to the pressure difference between the inside and outside of the pump; the high-speed rotation of the impeller gives the liquid kinetic energy, and the discharge chamber converts this increasing kinetic energy into pressure energy. 81. What are the main components of a centrifugal pump? Answer: The main components include: shaft, impeller, pump body, bearings, bearing housing, sleeve, sealing device, axial thrust, balancing device, and coupling. 82. How many types are there for pump sealing devices? Answer: The sealing mechanism of a pump includes two aspects: (1) the seal between the impeller and the pump casing ； (2) Sealing between the pump casing and the bearings. 83. What preparations should be made before starting a pump? Answer: Check the condition of the pump and whether the lubrication oil level in the bearings is normal ； Open the inlet valve ； Turn off the vent switch ； Turn on the cooling water ； Is there any abnormality in the cranking motion? 84. What are the reasons why a centrifugal pump does not work? Answer: (1) There is air inside the pump ； (2) Blockage in the impeller flow channel ； (3) Large gap between the impeller mouth ring and the shell mouth ring ； (4) Reverse installation of the multistage pump impeller, etc. 85. What are the disadvantages of operating a centrifugal pump at low flow rates for extended periods of time? Answer: (1) Raise the temperature inside the pump ； (2) Increase in radial thrust ； (3) Surge. 86. Why must the pump be filled with liquid before starting a centrifugal pump? Answer: When the impeller of a centrifugal pump rotates idle, the centrifugal force generated on the air is very small, not enough to expel the air; as a result, the pressure inside the pump does not drop below atmospheric pressure. Therefore, it is not possible to draw in a liquid at 1 atmosphere of pressure; thus, the pump chamber must first be filled with liquid before starting the centrifugal pump. 87. What are the reasons why a pump motor will not rotate? Answer: (1) Oil solidification ； (2) Stuck due to lack of regular turning over ； (3) Faults in the pump itself. 88. What are the common faults of centrifugal pumps? Answer: (1) Find some time ； (2) High-current trip ； (3) Sealing leakage ； (4) High vibration ； (5) Bearing overheating and shaft seizure ； (6) Large leak in the cover. 89. Why is it necessary to first close the outlet valve slowly before shutting down the pump? Answer: It is to prevent the high-pressure liquid in the outlet pipeline from flowing back, impacting the pump body and causing the impeller to rotate in the reverse direction and thus damaging the components ； Additionally, closing the outlet valve of the pump reduces the load on the pump, thereby lowering the motor current. When the motor is stopped and the electrical switch is disconnected, no excessive arcing occurs, which prevents damage to the switch contacts as well as arcing-induced short circuits. 90. What is the purpose of pump sealing? Answer: (1) To prevent the liquid at the high-pressure side from leaking out between the shaft and the pump casing, improve the efficiency of the pump, and ensure safe and reliable operation ； (2) Prevent air from the low-pressure side from entering the pump through the gap between the shaft and the pump casing, thereby affecting the pump’s normal suction. 91. What are the two types of sealing methods for centrifugal pumps? Answer: There are two types: packing seal and mechanical seal. 92. Can closing the pump outlet valve to increase the pump outlet pressure improve the flow rate? Why? Answer: The flow rate cannot be increased. Because: (1) Closing the outlet valve increases the pressure before the valve, while the pressure behind the valve decreases ； (2) The flow rate decreases, and since the cross-sectional area of the pipe remains unchanged, the flow velocity will not increase but will decrease instead. 93. What is the function of the shaft seal in a centrifugal pump? What are its sealing measures? Answer: The main function of the shaft seal in a centrifugal pump is to prevent the liquid inside the pump from leaking out and to stop air from entering the pump, thereby ensuring its proper operation. There are two common sealing methods: packing seal and mechanical seal. 94. What range is considered normal for bearing temperature and vibration during the routine inspection of mechanical pumps? Answer: The vibration clearance of the bearings should be ≤ 0.06 mm; the temperature of sliding bearings should be ≤ 650°C, while that of rolling bearings should be ≤ 700°C. The temperature of the motor should also not exceed 700°C. 95. What is the purpose of lubricating mechanical pumps? Answer: The purpose of lubricating a pump is to reduce friction between its internal components, minimize wear, wash away impurities generated during operation, and dissipate the heat produced during operation. 96. Which parts of a centrifugal pump are lubricated? Answer: The parts of a centrifugal pump that require lubrication are the shaft and bearings inside the bearing housing. 97. What is the common method used to adjust flow rate in centrifugal pumps during operation? Answer: In practical use, when the conditions of the equipment remain constant, adjusting the opening degree of the centrifugal pump’s outlet valve to change the fluid resistance in the pipeline is the most common method used to regulate flow rate. 98. What are the main causes of vibration in centrifugal pumps? Answer: The reasons for vibration are: (1) The axis centerline is not aligned ； (2) Shaft bending ； (3) Damaged or excessively worn bearings ； (4) Base screws are loose ； (5) Insufficient intake volume, resulting in unstable flow and partial evacuation ； (6) Pump evacuation ； (7) Cavitation. 99. What are the reasons for high temperature in centrifugal pump motors? Answer: (1) Poor insulation ； (2) Overload, excessive current ； (3) Voltage too low ； Excessive current ； (4) Bearing housing runs out of place or excessive vibration ； (5) Unbalanced three-phase current. 100. How should overheating of the pump shaft be dealt with? Answer: The pump shaft causes the oil tank temperature to rise excessively due to heat generation, and noise is also produced; the temperature at the friction points can reach several hundred degrees or even thousands of degrees, which can melt the balls in the bearings on the shaft. Therefore, when it is detected that the bearing housing temperature exceeds the specified limit, the pump should be stopped immediately. Have a fitter inspect it; if the shaft is found to be red, never pour water on it. Instead, stop the pump to allow it to cool down, and then have a fitter carry out repairs. 101. What types of pressure gauges are used on centrifugal pumps? Describe its principle. Answer: A Bourdon tube pressure gauge is used on centrifugal pumps. Principle: When pressure is applied to the pressure gauge, the Bourdon tube expands into a circular shape; its free end extends outward. Through the action of connecting rods and sector gears, this movement causes the pointer to rotate, thereby indicating the value of the pressure on the scale. (5) The gap between the valve and the flange should be appropriate, around 2 mm ； (6) The distance between the valve and the pipe seat should be greater than 100 mm. 102. What are the reasons why a centrifugal pump fails to deliver flow after starting? How to handle it? Answer: (1) Air leakage in the inhalation pipeline system. Solution: Check for leaks in the inlet piping system. (2) The pump is not filled or not fully filled. Solution: Refill the pump. (3) Cavitation occurs, leading to evacuation, due to reasons such as increased resistance in the suction pipeline caused by an excessively high geometric installation height, too high liquid inlet temperature, and excessive liquid viscosity. Solution: Identify the cause of cavitation, reinstall it, cool down, increase pressure, remove the blockage, or replace the impeller. (4) Mechanical reasons: Pump shaft breakage, loose impeller, reverse rotation or insufficient speed of the impeller, corrosion or damage to the impeller, etc., can all cause the pump to lose suction. Solution: Reassemble or replace the impeller. (5) Equipment failure or malfunction: a. Gas remaining in the pump chamber has not been completely discharged ； b. The inlet valve is not open or the valve core has fallen off ； c. Blockage in the inlet pipeline or impeller flow channel ； d. The liquid level in the suction tank is too low or there is no liquid. Treatment method: a. Drain the gas completely ； b. Open the valve or repair it ； c. Remove blockages ； d、Raise the liquid level in the suction tank or switch tanks. 103. What is the phenomenon of \"cavitation\"? Answer: When a centrifugal pump is in operation, the liquid is drawn into the pump under pressure differences. If the absolute pressure at a certain point at the pump inlet is lower than the saturated vapor pressure of the liquid, the liquid will vaporize to form bubbles that are mixed within the liquid. As the liquid rotates at high speed inside the pump, these bubbles continuously coalesce into droplets; the collisions between these droplets generate noise and vibration, and this is the phenomenon known as \"cavitation\". 104. Why is it necessary to regularly turn the standby pump manually? What’s the temperature of the disk? Answer: (1) The pump shaft is equipped with components such as impellers, and under the long-term effect of gravity, the shaft may bend. Regularly turning the shaft to change the direction of the forces acting on it can minimize the bending deformation of the shaft. (2) The crankshaft carries lubricant to all parts of the bearings, preventing them from rusting; moreover, since the bearings are initially lubricated, it is possible to start immediately in an emergency situation. The standby equipment should be turned over at least once per shift, with a rotation of 1800 degrees in accordance with the operation direction of the pump. 105. What are the reasons for high noise in centrifugal pumps? Answer: (1) Insufficient amount of lubricating oil or substandard quality of lubricating oil ； (2) No discharge, cavitation or evacuation ； (3) Severe wear of rotating components ； (4) Debris inside the pump. 106. What are the causes of severe leakage in the packing box of a centrifugal pump, and how to address it? Answer: Reason: (1) The packing box bolts are not tightened or the gland is skewed ； (2) Damage to the packing or end face seal ； Exclusion method: (1) Tighten the packing box bolts and adjust the gland ； (2) Replace or add packing, adjust the end-face seal to prevent skewing. 107. What are the auxiliary equipment of oil tanks? Answer: The auxiliary equipment of oil tanks includes: light-transmitting holes, manholes, measurement holes, siphon drain valves, internal shut-off valves, lift pipes, breather valves, hydraulic safety valves, fire suppressors, foam injectors, ventilation pipes, inlet and outlet short pipes for the bypass pipe system, oil heaters, etc. 108. Why are lead gaskets installed at the edges of the oil tank gauging port? Answer: It is to prevent accidents such as fires or explosions in the oil tank caused by sparks resulting from metal collisions and friction between the dipstick and the measuring device when closing the lid. 109. What are the obvious advantages of floating roof oil tanks? Answer: Floating roof tanks have the following obvious advantages: since there is no gas space, corrosion of the tank walls and roof is significantly reduced ； In terms of steel consumption, it is 15–20% less than that of similar fixed-roof oil tanks ； This type of oil tank is easy to repair, and it poses a lower risk of fire and explosion compared to other types of oil tanks. 110. What is the function of the vent windows (ear windows) on the wall of an internal floating roof tank? Answer: (1) Provide adequate ventilation to prevent the oil vapor concentration in the space above the floating deck from reaching the explosive limit ； (2) It can serve as a liquid storage and overflow function in an accident scenario. 111. What are the “four understandings” and “three abilities” required to manage equipment properly? Answer: Four understandings: understanding the structure, understanding the principle, understanding the performance, and understanding the application. Three skills: know how to use it, know how to maintain it, and know how to troubleshoot faults. 112. Briefly describe the general procedure for cleaning oil tanks. Answer: The cleaning methods for various oil tanks vary depending on the type of oil and the degree of contamination in the tank; different requirements are thus imposed on the tanks to be cleaned. The basic procedures for tank cleaning are as follows: (1) Preparation work: Determine the cleaning plan, and prepare the necessary equipment, cleaning tools, and protective gear ； (2) Pouring out oil: Use a pump to empty the oil in the tank ； (3) Removing oil from the bottom of the tank: Open the upper and lower manholes, light-transmitting holes, and oil-level measurement holes, and use a temporary pump to drain all the oil at the bottom of the tank. (If welding is required on the tank or if the inlet and outlet pipelines need to be handled, the oil inside those pipes can first be pumped back into the tank; after the oil at the bottom of the tank has been drained, blind flanges can be installed at the flange connections for the inlet and outlet of the tank.) ； (4) Ventilation by blowing air or forcing air in ； (5) Flushing: Connect the water supply line and nozzles, and flush the tank with water. While flushing, clean it with a broom or brush, and drain the water into the sewer (for heavy oil tanks, scrub with sawdust) ； (6) Scrubbing: Use a broom to remove rust debris, and wipe the bottom of the tank, its walls, and the interior fixtures with mops and rags until they are clean enough ； (7) Storage tanks that require welding work must also undergo steam cooking ； (8) Cleaning: After construction is completed, clean the debris inside the tank ； (9) After passing the inspection and acceptance, seal the container for future use. 113. What issues should be considered when operating oil tanks in winter? Answer: (1) It is strictly prohibited to transport oil products with water ； (2) Conduct regular inspections to check the water cut tank, sewage outlets, and all drain valves; remove water promptly if it is present ； (3) The heating coil of the oil tank can allow a slight amount of steam emission as long as the oil temperature remains within the permissible range; attention should be paid to whether the heating in the dehydrating tank is functioning properly ； (4) Frost protection measures should be applied to the breather valves of oil tanks to prevent failure that could lead to the tanks collapsing. 114. Why must the surface of the oil tank foundation be higher than the ground level? Answer: (1) It facilitates drainage and keeps the bottom of the tank dry ； (2) Moisture resistance ； (3) Compensates for the uneven settlement at the bottom of the tank. 115. What is the function of the floating roof in a floating-roof tank? Answer: (1) There is essentially no gas space between the floating roof and the liquid surface, so the oil does not evaporate easily; as a result, both large-scale and small-scale breathing losses are virtually eliminated ； (2) Reduce air pollution ； (3) Reduce the risk of fires ； (4) Internal floating roof tanks also prevent rain, snow, and dust from accumulating on the floating roof, eliminating the need for special drainage elbows, which further helps to ensure the quality of the stored oil. 116. In which areas is the bottom plate of oil tanks prone to corrosion? Answer: Generally speaking, the distribution of corrosion is not uniform; corrosion tends to occur in the following areas: (1) Depressed areas: Even if the tank wall is not corroded, there are numerous pitting defects in the depressed parts of the bottom plate. (2) Around the heating tube supports: Pitting occurred on the floor surrounding the pillars inside the heavy oil and crude oil tanks that are used to support the heating tubes. (3) Weld heat-affected zone: Due to the changes in the metal structure of the weld heat-affected zone, residual stresses are generated, leading to pitting along the weld path within this zone. (4) Areas where mechanical plastic deformation occurs and areas with scratches caused during construction are prone to pitting corrosion. 117. Under what circumstances should oil tanks be cleaned? Answer: Oil tanks should be cleaned under the following circumstances: (1) when maintenance, renovation, or the adoption of new technical measures is required ； (2) There are many pollutants and impurities inside the tank, which affect the quality of the oil ； (3) Changing the type of oil, as well as using the original oil type, has an impact on the quality of the newly installed oil ； (4) The oil tank has exceeded the specified cleaning time. 118. What issues should be considered when operating oil tanks in winter? Answer: (1) Water is strictly prohibited in the transportation of oil products. (2) Conduct regular inspections to check the water cut tank, drain outlets, and drain valves, and remove water promptly if it is present. (3) The heating coil of the oil tank can allow for slight venting of steam and water removal as long as the oil temperature remains within the allowable range; it is necessary to monitor whether the heating process is functioning properly. (4) Frost protection measures should be applied to the breather valves of oil tanks to prevent failure that could lead to the tanks collapsing. 119. What are the four no’s regarding equipment operation? Answer: No overheating, no overpressure, no overspeed, no overload. 120. Why do oil tanks deflate? Answer: The main reasons for the deflation of oil tanks are as follows: In winter, moisture inside the tank causes the disc and seat of the mechanical breathing valve to freeze and become non-functional ； The breather valve spring is rusted and no longer functional ； The oil release rate is too fast, exceeding the air intake speed allowed by the diameter of the breather valve, resulting in negative pressure inside the tank ； Exceeds design specifications ； The copper mesh or corrugated plate of the flame arrester has fallen off and caused a blockage ； When the breather valve fails, the excessively low or rapid oil inlet temperature causes the temperature of the gas space inside the tank to drop rapidly, resulting in significant condensation of oil and gas and the creation of a negative pressure that exceeds the specified design limits. 121. How to deal with oil leakage at the bottom of an oil tank? Answer: (1) Immediately pour water into the tank to isolate the oil from the leakage site ； (2) Quickly pour the oil from the leaking tank into other tanks containing the same material ； (3) Organize personnel to handle the spilled oil ； (4) Treat the oil tank and deliver it for maintenance upon passing the inspection. 122. Why can’t the oil inlet pipe be connected from the top of the oil tank? Answer: During transportation, oil must pass through oil pumps and pipelines before entering the oil tank. Since it is not possible to dissipate all the static electricity generated as the oil flows, a certain amount of static electricity accumulates in the oil itself upon entry into the tank. If the inlet pipe is connected at the upper part of the tank, the oil flowing at high speed will spray out in a mist-like form from high to low, increasing the area of friction due to contact with air. The remaining oil then hits the liquid surface and tank walls, causing a sharp increase in static electricity – the voltage can reach several thousand to tens of thousands of volts. Coupled with the floating impurities present in the oil, this can easily lead to spark discharge, resulting in explosions and fires in the tank. Therefore, it is strictly prohibited to connect the inlet pipe at the upper part of the tank. 123. What are the four systems for equipment operation? Answer: a. Rotating inspection system ； b. Post responsibility system c. Equipment lubrication system ； d. Equipment maintenance system. 124. What are the advantages of using hoses for the oil inlet and outlet pipelines of oil tanks? Answer: At the earthquake site, it was found that tank ruptures were extremely rare, while ruptures in the oil inlet and outlet pipelines near the tanks were more common. Therefore, replacing this section with a hose can reduce the risk of breakage. When the tank in question is put into use, the sudden increase in load causes significant settlement of the tank; a hose can serve as a buffer to compensate for this. 125. What are the reasons for the overturning or sinking of the floating disk in internal floating roof tanks? How to avoid it? Answer: The reasons for the overturning or sinking of the floating disk in internal floating roof tanks are as follows: (1) Poor construction quality, or individual supports being welded firmly to the tank bottom plate ； (2) Operational issues: too fast oil inlet speed, gas entrainment blown into the floating roof tank ； (3) Structural issues: In some tanks, no light-transmitting holes are provided on the tank walls, and an increased number of vent valves are installed on the roof, which results in pressure being applied to the upper part of the floating disk and reduces its buoyancy ； (4) Process condition issues: Due to the high inlet oil temperature, or because the oil has not been properly stabilized and degassed, its vapor pressure increases. Above the oil inlet, the rapid rise of large amounts of gas causes the floating disk to tilt and get stuck, as well as leading to flooding. The measures to prevent the floating platform from sinking or capsizing are as follows: (1) Improve construction quality and conduct thorough inspections and acceptance ； (2) Design the floating roof tank in strict accordance with design specifications ； (3) Strengthen responsibility by adding high and low liquid level alarms ； (4) Reduce the inlet oil temperature and install additional oil stabilization and dehydration facilities to ensure that the vapor pressure of the inlet oil remains below 66.7 kPa ； (5) Diffuser tubes are added inside the oil tank, which helps to distribute the oil evenly and prevent concentration, thereby improving the stable operation of the floating disk and avoiding overflow ； (6) It is strictly prohibited to blow gas into the internal floating roof tank during pipeline purging. 126. What are the advantages of internal floating roof tanks compared to dome tanks? Answer: (1) **Reduced evaporation losses of oil products ； (2) Reduces the risk of fire and explosion ； (3) Reduced air pollution ； (4) Reduced the corrosion of oil products on the tank roof and tank walls ； (5) Ensure the quality of the stored oil products. 127. How to conduct a gas tightness test? Answer: From a technical standpoint, it is first necessary to check the system flow, close all backflow valves, and inspect the equipment and pipes for any openings or air leaks. Install pressure gauges, and restore all flanges, manholes, level gauges, thermometers, etc. related to the equipment. Before conducting the airtightness test, the system must be purged and flushed, followed by a gas introduction test. During the test, the pressure should be increased gradually. Once the specified test pressure is reached (in China, this is the design working pressure for airtightness tests), the pressure is maintained for 10 minutes before being reduced to the working pressure. Afterwards, soap water or a leak detector is used to check all welds, flanges, valves, manholes, level gauges, and other potential leakage points in the equipment; any leaks found must be repaired until no more leaks occur. However, leaks cannot be sealed while the equipment is under pressure. The pressure should generally be maintained for more than eight hours; if the average pressure drop per hour is ≤0.2%, the airtightness test is considered successful. Requirements: (1) Units under different pressures must be tested separately ； (2) Try to identify all leaks during a single pressure filling ； (3) Knocking on the equipment is not allowed in a hermetically sealed environment ； (4) Clear division of labor is necessary for ensuring airtightness, and leaks must be carefully recorded ； (5) The pressurization must be done slowly. 128. What is the role of valves in pipelines? Answer: (1) To enable or stop the flow of the medium in the pipeline ； (2) Change the flow direction of the medium in the pipeline ； Adjust the flow rate and pressure of the medium ； (3) Protect the safety of the pipeline system. 129. Why can’t valves be opened and closed quickly? Answer: Rapid opening and closing of valves can cause the following hazards: (1) It can generate significant water hammer in the pipelines, damaging the pipelines and equipment ； (2) Suddenly increasing the pressure in the pipeline equipment, resulting in excessive shock forces ； (3) Cause a sudden temperature rise in pipeline equipment, resulting in excessive thermal stress ； (4) If communication is not timely during the switching operation, it may cause significant effects on the device (such as vacuum formation, tripping, etc.) ； (5) A sudden change in the pump’s displacement causes it to operate unstably. 130. What are the causes of external leakage in valves? How to handle it? Answer: External leakage of valves includes: (1) Leakage at the packing gland ； (2) Leakage at the flange joint of the valve end face ； (3) Leakage at the valve cover. (1) Causes of leakage at the packing gland and solutions: a. Inappropriate selection of packing – choose the right type of packing. b. Incorrect installation of the packing – reinstall the packing properly. c. Corrosion at the base of the valve stem – repair it (e.g., by grinding). d. Failure to replace the packing regularly – replace it on a regular basis. (2) Leakage at the flange joint at the valve end face: Causes and solutions: a. Inappropriate selection of gaskets – use the appropriate type of gasket. b. Incorrect installation of the gaskets – reinstall them properly. c. Damaged gaskets or failure to replace them regularly – replace the gaskets. d. Improper operation leading to overheating or overpressure – follow the operating procedures. e. For valves used in high-temperature or low-temperature environments, expansion/contraction may cause thermal or cold tightening. f. Loose bolts – tighten them again. 131. How to determine if there is internal leakage in a valve? Explain the reasons and solutions. Answer: First, check the temperatures of the pipelines on both sides of the valve; if there is a temperature difference, it indicates internal leakage in the valve (for volatile liquids) ； Second, check the pressures on both sides of the valve; if the pressures are equal (the valve is in the closed position), it indicates that there is a leak inside the valve, whereas if the pressures differ, then there is no leak. Reason: Solution: (1) The valve seat and valve body are not airtight; repair or weld them. (2) Make the valve seat and valve disc more airtight, and re-grind the sealing surfaces. (3) Improper operation with excessive force; follow the correct operating procedures. (4) Improper maintenance resulting in the valve not closing properly; carry out proper maintenance. 132. What is the function of a safety valve? Answer: A safety valve is an important safety pressure relief device for pressure vessels, industrial pipelines, etc. Under normal conditions, it remains tightly sealed to the vessel or pipeline without any leaks; when the pressure in the vessel or pipeline exceeds the safe level, the safety valve opens automatically to release pressure, thereby ensuring the safety of such vessels and pipelines. At the same time, the harsh sound produced when the safety valve activates can serve as an alarm. 133. Explain the working principle of a safety valve. Answer: The working principle of a safety valve is that the compressive force of the spring or the pressure exerted by a weight through a lever is greater than the pressure exerted by the medium; at this point, the valve disc seals against the valve seat surface ； When the pressure of the medium exceeds the specified value, the spring is compressed or the weight is lifted; the valve disc loses its balance, moves away from the valve seat, and the medium is discharged ； When the medium pressure drops below the specified value, the compressive force of the spring or the pressure exerted by the weight through the lever exceeds the medium pressure acting on the valve disc; as a result, the valve disc returns to its original position and the sealing surfaces come back into close contact. 134. What are the structural differences between globe valves and gate valves? Answer: The structure of a stop valve is similar to that of a gate valve, consisting of four parts: the valve body, the sealing element, the actuation mechanism, and the sealing surface. The difference lies in the fact that the sealing element is not a gate plate but rather a valve disc and a valve seat; moreover, the flow channels for inlet and outlet are not on the same central line. 135. Write down the codes for gate valves, globe valves, ball valves, check valves, safety valves, pressure relief valves, and plug valves. Answer: Gate valve Z ； Stop valve J ； Ball valve Q ； Check valve H ； Safety Valve A ； Pressure relief valve Y ； Plug valve X. 136. How to choose a valve? What are the requirements for installing valves? Answer: Selecting the valve: (1) Determine the valve material based on the corrosiveness of the medium ； (2) Determine the material and nominal pressure based on the medium temperature and pressure ； (3) Determine the nominal diameter of the valve based on the medium flow velocity and flow rate ； (4) Determine the structural form of the valve based on its installation, operating medium, and cost-effectiveness. Installation requirements: (1) The valve should be installed in a location that facilitates operation and maintenance ； (2) The valve stem of horizontal pipelines should point vertically upward ； (3) Pay attention to the material flow direction; it must not be installed in the reverse order (such as stop valves, check valves, etc.) ； (4) Clean the inside of the valve thoroughly before installation ； Chapter 4 Fire Safety 137. What are the characteristics of oil fires? Answer: (1) Fast burning speed ； (2) High flame temperature, large amount of radiant heat ； (3) Prone to explosion, with fire spreading very easily ； (4) Oils containing moisture are prone to bumping, which hinders fire suppression ； (5) During the intense phase of a petroleum fire, it is difficult to extinguish it. 138. What are the basic methods of extinguishing fires? Answer: (1) Isolation method ； (2) Asphyxiation method ； (3) Cooling method ； (4) Inhibition method. 139. What are the protective measures of the “four essential items” for safe construction? Answer: (1) Safety helmet ； (2) Seat belt ； (3) Safety net ； (4) Leakage protector. 140. What conditions are required for combustion? Answer: Three conditions must be met simultaneously: (1) there must be combustible material ； (2) Combustion aids ； (3) There is a fire source. 141. What are the three levels of safety training in our factory? Answer: (1) Safety education before entering the factory ； (2) Workshop safety education ； (3) Team safety education. 142. What are the causes of a fire in an oil pump? Answer: (1) The packing was installed too tightly, causing overheating and smoking, which in turn ignited the oil vapor accumulated in the pump room. (2) Idling of the oil pump causes excessive temperature in the pump casing ； (3) Excessively high resistance of the electrostatic wire or the wire is broken and non-functional ； (4) Impact by iron objects or external sources of fire. 143. What are the sources of fire that can cause fires? Answer: Generally speaking, they can be divided into direct fire sources and indirect fire sources. There are mainly three types of direct sources of fire: (1) open flames ； (2) Electric spark ； (3) Lightning strike. There are mainly two types of indirect fire sources: (1) ignition by heating and spontaneous combustion ； (2) Self-ignition. 144. Why should hazardous substances not be discharged into the sewer system? Answer: Since hazardous substances are mostly toxic and flammable materials, when discharged into sewers, they contaminate water sources. Moreover, when such substances accumulate to a certain level, they can easily reach a level that poses an explosion risk; in the presence of an ignition source, fires and explosions may occur. Furthermore, the sewers are mostly crisscrossing, and many locations lack safety measures, making fires likely to occur; these fires can then spread to even more dangerous areas. 144. Why cannot gasoline or light oils be used to clean equipment, tools, and clothing? Answer: Because: (1) Gasoline or light oils have a low flash point; their vapors are lighter than air, easily volatile, and can form explosive mixtures with air, which may explode if exposed to an ignition source ； (2) Gasoline and light oils generate static electricity when subjected to vibration, collision, impact, or friction; when this electricity reaches a certain level, it can discharge and ignite the volatile vapors of gasoline, causing an explosion. 145. What are the four conditions that must be present for an electrostatic fire or explosion accident to occur? Answer: For an electrostatic fire or explosion accident to occur, the following four conditions must be present simultaneously: (1) Electrostatic charge ； (2) Conditions for spark discharge to occur ； (3) The sparks generated must have sufficient energy ； (4) There are flammable and explosive substances in the discharge gap and its surrounding environment. 146. What is the fire-extinguishing principle of foam extinguishants? Answer: The foam produced by foam extinguishants is lighter than oil, allowing it to float on the surface of the oil and spread freely, thereby preventing contact between the flammable gas and the outside air. Combustion stops due to lack of oxygen; the main mechanism of action is suffocation. 147. What are the safety measures for working with fire? Answer: (1) Obtain a valid hot work permit ； (2) Combustible material content monitoring is satisfactory ； (3) Remove all combustible materials around the area where welding is being performed ； (4) A certain number of fire extinguishing equipment should be available at the site where welding work is carried out ； (5) There must be a fire supervision officer present, who should immediately stop the use of fire in case of any abnormal situations ； (6) After the hot work is completed, a thorough inspection must be carried out to remove all remaining embers ； 148. The degree of injury caused by electric shock to the human body depends on three factors: Answer: 1. The current flowing through the body; 2. The path taken by the current through the body; 3. The duration for which the current flows through the body. 149. In what environments are filter-type gas masks suitable? Answer: Filter-type gas masks are suitable for environments that are not at high temperatures, where the oxygen content is above 20% and the concentration of toxic gases is below 2%, providing protection against corresponding toxic substances. 150. What is the function of a fire dike? Answer: The fire dike is an integral part of the tank farm safety system; it serves a dual purpose, namely containing spilled oil and preventing the spread of fire in case of an outbreak. 151. What are the specific methods for using the cooling method to extinguish fires? Answer: There are two specific methods for using the cooling method to extinguish fires. One involves spraying water directly on the burning material to absorb the heat generated during the oxidation process, thereby lowering the temperature below the ignition point and causing the flame to go out ； Another method is to spray water on the combustible materials near the burning substance, thereby protecting them from the threat of flame radiation and preventing combustion or explosion. 152. What are the methods of using suffocation to extinguish fires? Answer: The main methods of using the smothering technique to extinguish fires are as follows: First, use non-flammable or poorly flammable materials to cover the surface of the burning material, thereby preventing air from reaching it and stopping the combustion ； Secondly, water vapor or non-flammable gases are sprayed into the burning material to dilute the oxygen in the air, reducing its concentration to below 9%, thereby achieving extinguishment through asphyxiation ； Third, try to seal the holes and gaps in the container that is on fire, so that the oxygen inside the container is consumed during the combustion process with no new supply arriving, thereby achieving extinguishment through suffocation. 153. What are the specific methods for using isolation to extinguish fires? Answer: The specific methods for using isolation to extinguish fires are as follows: (1) Quickly remove combustible, flammable, and easily **ignitable items from the area around the fire ； (2) Promptly remove flammable buildings and ignition sources adjacent to the fire site ； (3) Prevent flammable and oxidizing substances from entering the combustion zone ； (4) Prevent the spread and splashing of burning materials ； (5) Move the movable flammable materials to a safe location using safe methods, so that the burning materials can burn under human control. 154. What are the basic ways to prevent the hazards of static electricity? Answer: (1) Process control method: a. Limit the conveying speed ； b. Accelerate the dissipation of static electricity charges c. Eliminate additional sources that generate static electricity ； d. Remove impurities ； e. Reduce the concentration of explosive mixtures. (2) Leakage diversion method: a. Humidification ； b. Add antistatic agent ； c. Ensure the holding time and relaxation time ； d. Static grounding. (3) Legal in static electricity (use an electrostatic eliminator). (4) Anti-static measures for the human body: a. Grounding of the human body ； b. Conductivity of the working surface ； c. Safe operation. 155. What precautions should people entering the equipment to work take? Answer: When working inside equipment or containers, the following points should be noted: (1) Strictly adhere to the dressing code by wearing appropriate work clothing and safety protective gear ； (2) No items unrelated to maintenance work are allowed to be brought into the equipment to prevent them from being left inside ； (3) Use tools and equipment as specified ； (4) Manholes should be equipped with ventilation facilities to ensure the oxygen level within the equipment ； (5) After completion, the site must be thoroughly cleaned; only after checking to ensure that no debris remains can one leave. 156. What are the common fire-fighting tools? Answer: Common fire-fighting tools include: (1) fire hoses and fire hydrants ； (2) Fire-fighting steam ； (3) Fire extinguishers ； (4) Other tools, such as sand, felt, seaweed*, etc. 157. What does the “three skills” in fire fighting entail? Answer: The ability to report a fire, the ability to use fire-fighting equipment, and the ability to extinguish incipient fires. 158. Explain the working principle of dry powder fire extinguishers. Answer: The mechanism of chemical dry powder fire extinguishing is as follows: (1) When the powdered mist is sprayed onto the flame, it prevents oxygen from reaching the flame; at the same time, it **reduces the radiant heat exerted by the flame on the combustible materials, thereby decreasing their decomposition and evaporation ； (2) The fine dry powder particles decompose upon exposure to the high temperature of the flame, producing non-flammable gases such as carbon dioxide and water vapor, which helps to extinguish the fire by suffocation. At the same time, heat absorption during the decomposition reaction helps to cool the combustible materials ； (3) According to the latest theories of combustion, combustion is a vigorous oxidation reaction that produces light and heat; it is a chain reaction driven primarily by the presence of reactive species H+ and OH—. When the foggy powder comes into contact with the flame, a large number of active groups H+ and OH— are adsorbed on the surface of the fine dry powder particles, resulting in a strong inhibitory effect that prevents the chain reaction from continuing, thereby extinguishing the fire instantly. 159. What are the “four prohibitions” during maintenance? Answer: Construction and use of fire are not permitted in the absence of safety measures or when such measures are not implemented ； It is prohibited to enter the construction site without wearing a safety helmet ； Working at heights is not allowed without a safety belt ； During work at heights, it is prohibited to drop objects from above. 160. Why can water and water vapor put out fires? Answer: Water and water vapor have the ability to absorb a large amount of heat, which can lower the combustion temperature. Water vapor can also easily be washed away or used to cut off the supply of air to the burning material, thereby extinguishing the fire. 161. How to carry out poison prevention in storage and transportation work? Answer: (1) Strengthen management and supervision, enhance education on poison prevention and safety, and regularly measure the concentration of toxic gases in the workplace air to ensure it remains below the maximum allowable level. (2) Ensure that equipment such as oil pipes, oil tanks, oil drums, and oil pumps are airtight to reduce the concentration of oil vapors in the air, especially to prevent leaks of leaded gasoline. (3) Attention should be paid to the ventilation in the barrel storage areas, filling rooms, and pump rooms to disperse the oil vapors that are heavier than air; mechanical ventilation can be employed if necessary. (4) It is prohibited for workers to enter the tank to remove bottom oil without taking safety measures. (5) It is strictly prohibited to suck oil from the rubber hose using the mouth ； It is prohibited to use leaded gasoline for washing hands, mechanical parts, clothes, or any other purpose ； It is strictly prohibited to use aviation kerosene with added carbon disulfide for lighting or any other purpose. (6) After working in a toxic environment, the clothes removed should be placed in a designated area ； It is not allowed to wear work clothes when going home or eating ； Hands must be washed carefully with hot water and soap before eating or smoking. (7) Strengthen personal protection; it is best to avoid smoking and drinking. 162. What are the hazards of hydrogen sulfide? Answer: H2S is a colorless gas with a very unpleasant odor and high toxicity; at low concentrations, it takes some time before symptoms such as headache, tearing, nausea, and shortness of breath appear. When the H2S concentration reaches 1000 mg/m3, it can cause loss of consciousness by directly paralyzing the respiratory center, leading to immediate asphyxiation and resulting in a \"shock-type\" poisoning. In hydrogen sulfide poisoning, the intensity of the odor initially increases in proportion to the concentration, but once the concentration exceeds 10 mg/m3, the odor weakens even as the concentration continues to rise. At high concentrations, olfactory fatigue occurs rapidly, preventing the detection of hydrogen sulfide; therefore, it is not possible to determine whether a dangerous concentration has been reached by judging the intensity of its odor. At the same time, when the hydrogen sulfide concentration reaches a certain level, it can cause fires and explosions. 163. What are the emergency evacuation measures for the finished product unloading platform? Answer: (1) After an accident occurs, a safety zone is established. Depending on the extent of the spread of the spilled refined oil or fuel, as well as the range affected by flame radiation, traffic control is implemented on the main roads leading to the accident site. Vehicles carrying refined oil or fuel are immediately evacuated and moved away from the accident site. (2) The boundaries of the warning area should be marked with warning signs and guarded by designated personnel. Except for fire and emergency response personnel, others are prohibited from entering the restricted area. (3) Open flames are strictly prohibited at the accident site; non-explosion-proof tools and synthetic fiber clothing must not be used. (4) In the event of an accident at a oil unloading site where toxic and harmful gases are released in large quantities, first responders must wear gas masks and air respirators before entering the accident site to carry out rescue operations. (5) Quickly evacuate people and vehicles unrelated to the accident from the restricted area, in order to reduce unnecessary casualties and economic losses. (6) In case of an emergency evacuation, people should move to the upwind area, with designated personnel guiding and escorting them to a safe zone. Do not stay in low-lying areas, tank locations, tree pits, and similar places. (7) When evacuating oil-carrying vehicles, a dedicated person should direct the evacuation process to ensure it takes place in an orderly manner and that the vehicles move away from the site of the incident. 164. Why cannot compressed air be used to clean pipelines for oils with a flash point below 600°C? Answer: Since compressed air contains oxygen, the flammable vapors in the pipelines mix with this oxygen to form an explosive mixture. During pipeline cleaning, friction between this mixture and the pipe walls generates heat as well as static electricity, which can easily lead to fires and explosions. Therefore, oils with a flash point below 600°C should not be cleaned using compressed air. 165. Types of combustion: Answer: Flash ignition: When air mixes with the vapor of a flammable liquid and comes into contact with a heat source, instantaneous combustion occurs; this phenomenon is known as flash ignition. The lowest temperature at which the vapor of flammable or combustible liquids can catch fire in contact with a source of ignition is called the flash point. Ignition: When a combustible material comes into contact with a flame at a certain temperature in the air, it catches fire. The phenomenon in which combustion can continue even after the flame is removed is called ignition. Spontaneous combustion: The phenomenon in which a combustible material burns on its own when its temperature rises to a certain level, without the need for an external source of fire, is called spontaneous combustion. Explosion limit: A mixture of flammable gases, dusts, and air must be within a certain concentration range in order to explode when exposed to an ignition source. This concentration is called the explosive limit concentration. The highest concentration at which an explosion can occur is called the upper explosive limit; combustion or explosion does not take place below the lower explosive limit or above the upper explosive limit. 166. Classification of the fire hazard of oils: Answer: The flash point is used as a criterion for grading the hazard level of oils. A flash point below 28 degrees Celsius corresponds to level 1; 28–45 degrees Celsius corresponds to level 2; 45–120 degrees Celsius corresponds to level 3; and a flash point above 120 degrees Celsius corresponds to level 4. The higher the level, the lower the hazard. 167. Classification of flammable and combustible liquids: Category Level Flash point Product name Flammable liquids 1 2 Below 28 degrees Celsius 28 degrees Celsius to 45 degrees Celsius Gasoline, alcohol, propane, toluene Jet fuel, kerosene Combustible liquids 3 4 Above 45 degrees Celsius to 120 degrees Celsius Above 120 degrees Celsius Diesel, No. 5 high-speed engine oil Lubricants, greases, asphalt 168. Classification of fire hazards associated with oils stored in oil depots: Category Oil flash point Examples A B Below 28 degrees Celsius 28 degrees Celsius to 60 degrees Celsius Crude oil, gasoline, etc. Jet fuel, lamp kerosene, No.-35 light diesel, etc. C A Above 60 degrees Celsius to 120 degrees Celsius Above 120 degrees Celsius Light diesel, heavy diesel, No. 20 heavy oil, etc. Lubricants, No. 100 heavy oil, etc. B Chapter 5 Glossary of terms 169. Evaporation: Answer: It refers to the process of vaporization that occurs at the surface of a liquid. 170. Flow rate: Answer: It is the total amount of fluid that passes through any cross-section perpendicular to the pipeline per unit of time. 171. Viscosity: Answer: It indicates the magnitude of the resistance generated between molecules due to friction as a liquid flows. 172. Pump efficiency: Answer: The ratio of the pump’s effective power to its shaft power is called the pump efficiency. 173. Density: Answer: The mass of a substance per unit volume. 174. Combustion: Answer: An intense oxidation reaction that releases heat and light. 175. Explosion: Answer: A phenomenon in which a substance rapidly changes from one state to another, releasing enormous amounts of energy in the form of mechanical energy in an instant, along with a loud noise. 176. Petroleum: Answer: A complex mixture that exists underground as a natural fuel, primarily composed of various hydrocarbons. 177. Rotational speed: Answer: Refers to the number of revolutions per minute of the pump shaft, measured in n/min. 178. Shaft power: Answer: The energy consumed by the pump shaft per unit of time. 179. Level gauge: Answer: Used in vertical metal tanks to measure the vertical distance from the liquid surface to the bottom of the tank. 180. Empty tank gauge: Answer: Used to measure the vertical height from the gauge point to the liquid surface inside the tank. 181. Static electricity: Answer: Electricity generated when two different materials are rubbed against each other. 182. Single-stage pump: Answer: A pump that has only one impeller; its head is limited to around 120–150 meters. 183. Multi-stage pump: Answer: A pump that has two or more impellers, allowing for a higher head, up to several hundred meters. 184. Gauge point: Answer: The point on the bottom of the container or on the gauge plate where the measuring rod makes contact during level measurement. The vertical metal storage tank specifies the location for taking measurements at the top of the tank. 185. Ignition point: Answer: It is the lowest temperature at which, when a liquid is heated above its flash point, the mixture of its vapor and air will burn continuously upon contact with a flame. 186. Isolation method: Answer: It is a method of separating the fire from combustible materials, thereby preventing those materials from continuing to burn. 187. Cooling method: Answer: It is a method of lowering the ignition temperature and eliminating the conditions necessary for combustion, so that burning cannot continue. 188. Smothering method: Answer: It is a method of isolating combustible materials from oxidizing agents, preventing them from obtaining oxygen from the air and thus stopping further combustion. 189. Oil refining: Answer: It is the process of using various physical and chemical treatment methods to transform crude oil into petroleum products that meet various quality standards, in order to resolve the discrepancy between the properties of crude oil and the requirements for its use. 190. Head: The height to which a pump can lift liquid. 191. Saturated vapor pressure: Answer: Under certain pressure conditions, when the liquid and vapor phases of water in a device are in equilibrium, the vapor phase at this point is known as saturated vapor