Construction of long-distance pipelines

Types of fires in oil tanks: 1. Stable combustion – In the case of oil tanks containing light oils, high temperatures cause a large amount of oil vapor to be released, escaping through vents, openings, and sampling ports. When this vapor comes into contact with a source of fire, it results in stable combustion, also known as torch combustion. 2. **Combustion**: The mixture of oil vapor and air inside the tank, within its **limiting range**, will undergo **combustion** when exposed to a fire source; this leads to damage to the tank, after which the combustion continues. Under certain conditions, oil leakage may occur, resulting in a flame from the leaked liquid. 3. Deflagration: When the concentration of oil vapor evaporated inside a tank containing heavy oil exceeds the **lower limit concentration**, and a fire source is present, deflagration may occur within the tank. Since the rate of vaporization of the oil vapor cannot keep up with the amount of vapor required for combustion, deflagration takes place and the tank stops burning further. A deflagration in an oil tank can cause damage to the tank itself; sometimes the tank roof collapses inside the tank. 4. Boiling combustion: When fires break out in tanks containing water-rich crude oil and heavy oil, unlike lighter oils, the most notable characteristic is the occurrence of boiling, splashing, and bumping during combustion.

Static electricity control and protection: To prevent fire accidents caused by static electricity, it is sufficient to eliminate any one or more of the four conditions required for static discharge to occur. That is, to prevent or reduce the generation of static electricity ； Find a way to divert or neutralize the generated charge, so that it cannot accumulate ； To prevent the generation of high electric fields, electrostatic discharge with sufficient energy is applied ； Prevent the formation of **mixed gas mixtures. Impurities in the oil are important factors that cause charging, yet achieving high precision in the oil is difficult and uneconomical. Therefore, to prevent oil-related static electricity disasters, it is not about completely eliminating the generation of static charge, but rather about controlling various parameters related to static electricity through process or equipment management, so as to prevent them from reaching dangerous levels and avoiding accidents. 1. Process control (1) Control the flow rate. Data shows that for the same type of oil, the higher the flow rate and the larger the pipe diameter, the greater the amount of static electricity generated. Tests on filling tank trucks with oil showed that at an average flow rate of 2.6 m/s, the potential of the oil surface was 2.3 kV ； When the average flow velocity is 1.7 m/s, the oil surface potential is 580 V; it can be seen that controlling the flow velocity is an effective measure to reduce the generation of static electricity. To limit the generation of static electricity, when oil flows within pipes, the flow velocity and pipe diameter must satisfy the following relationship: υ²D ≤ 0.64, where υ is the flow velocity in m/s ； D is the pipe diameter, in meters. (2) Control the refueling method. When oil tanks, tank trucks, etc. are filled from the top by splashing, the oil inevitably hits the tank walls, stirring the liquid inside the tank. It also accelerates the evaporation, atomization, and foaming of the oil, resulting in a sharp increase in the static electricity level of the oil inside the container. Therefore, the inlet pipe for the oil storage tank should be connected to the lower part of the tank; if connection from the upper part is necessary, it should extend to a distance of 200 mm from the bottom of the tank ； When the tank truck is filling the tank, the dip pipe should be extended to a distance of no more than 200 mm from the bottom of the tank. (3) Avoid mixing substances of different properties. When oils mix with water, air, and oils of different properties, the amount of static electricity generated increases. The mixing of different oil types can also pose a static electricity risk; such mixing generally occurs during blending, switching, or when two pipelines deliver different oils to a tank simultaneously. When compressed air comes into contact with oils, certain measures must be taken to limit the risks associated with static electricity. When working with oil products, it is strictly prohibited to use air to clean the oil at the bottom of oil tanks as well as Class A and Class B oil transmission pipelines. An accident occurred in a company where the flushing of residual oil on the floor with fire water led to an explosion. 2. Anti-static facilities (1) Grounding. Grounding is the most common measure to eliminate the hazards of static electricity. For **, as well as equipment and pipelines in areas prone to fire hazards that may generate static electricity, static grounding measures must be taken. Automobile tankers, railway tank cars, and loading/unloading sites shall be equipped with dedicated anti-static grounding wires. At the beginning, end, and middle sections of the railway oil loading and unloading trestle, electrical connections should be made with the rails, oil pipelines, dip pipes, etc., and it should be grounded. Filling facilities for motor vehicle tankers or drums of Class A oils, such as type A, B, and C, shall be equipped with anti-static grounding devices that are connected to the tankers or drums. At oil loading and unloading terminals, an antistatic grounding device that can be connected to oil tankers should be installed; this grounding device shall share the same system as the antistatic grounding devices of the oil loading and unloading equipment located at the terminal. Anti-static grounding devices should be installed at the beginning and end of oil pipelines laid on the ground or in trenches, at branching points, and every 200–300 meters along the straight sections. (2) Antistatic additives. Antistatic additives are compounds that increase the conductivity of oils. Their role is not to \"combat\" static electricity, but rather when added in small amounts, they can increase the conductivity of the oil by many times over, preventing charge accumulation without affecting the quality of the oil. There are many types of antistatic agents, such as oleates, cyclic sulfonates, chromium salts, and synthetic fatty acid salts. (3) Static eliminator. An electrostatic eliminator is a device that generates electrons or ions; by utilizing these electrons or ions, the static charge on the material is neutralized by an opposite charge, thereby achieving the elimination of static electricity. 3. Restrictions on operating conditions: In order to avoid the maximum static electric potential on the oil surface and prevent static electricity-related accidents, when performing inspection tasks on containers that have just been filled with oil or have been transported, the oil must be allowed to stand for a certain period of time to ensure that the static charge within the container can dissipate. The standing time for oils is determined based on the oil’s conductivity and the volume of the container, as shown in Table 1. Table 1: Standing time of oil, electrical conductivity of oil/(S·m-1), container volume/m3 – <10, 10–50, 51–5000, >5000. Standing time/min: 10–8, 1, 1, 1, 2; 10–12–10–8, 2, 3, 20, 30; 10–14–10–12, 4, 5, 60, 120; below 10–14, 10, 15, 120, 240. Therefore, during the standing time of oil in tanks and containers, operations such as measuring volume, taking temperature readings, and sampling are strictly prohibited. For railway tank cars and road tank trucks, volume measurement and temperature testing must be carried out only after the oil has been loaded and allowed to stand for a certain period of time. Any temperature measuring devices or sampling tools made of metal must use ropes made of conductive materials and must be properly grounded to the tank body. It is not allowed to use tools made of two different materials with varying electrical conductivity for volume measurement, temperature testing, or sampling. When feeding oil into the tank, it is necessary to avoid starting or stopping the pump suddenly. Sudden starts and stops can cause sudden pressure spikes and high flow rates, leading to the generation of static electricity and potential accidents. It is more reasonable to use the sequence of starting with a small pump and a large pump, and then stopping with a large pump and a small pump, as this can provide good protection. 4. Human anti-static protection: It is more dangerous for humans to become charged than for machinery and equipment, as people move around. If one moves around or operates in a hazardous area, it is equivalent to a moving source of fire. Therefore, anti-static protection for the human body cannot be ignored. (1) Wear anti-static shoes and use a conductive floor. The human body can accumulate static electricity only if it is insulated from the ground; if the static electricity generated is dissipated by the ground, the body cannot remain charged. From an anti-static perspective, materials with a resistance of less than 108Ω are considered conductors. The resistance of anti-static shoes ranges from 0.5×105Ω to 108Ω; they act as conductors for static electricity, yet as insulators for power frequency alternating current, and they also provide protection against electric shock. Wearing anti-static shoes is only effective on conductive floors. For surfaces such as soil, sand and gravel, cement, etc., the resistance does not exceed 106Ω, and they are all electrostatic conductors. Conductive flooring should be used in any area where flammable gases or liquids may leak. To ensure the reliability of anti-static shoes, the following rules should be followed when wearing them: ① Do not wear thick socks made of wool or synthetic fibers, except those with conductive fibers ； ②Shoe insoles are prohibited ； ③Do not allow the soles to become contaminated with oils, paints, etc.; the soles must not contain any insulating impurities. (2) Wear anti-static clothing. Anti-static clothing contains conductive fibers that prevent the accumulation of static electricity. To ensure the reliability of anti-static clothing, the following points should be observed when wearing it: ① It is prohibited to put on or take off such clothing in areas where static electricity poses a risk ； ②It is prohibited to attach or wear any metal parts on static-control workwear; if metal parts must be used, they must not be exposed. The buttons must be fastened properly; the front and hem should not be in a state that is close to being unfastened ； ③Must be used in conjunction with anti-static shoes ； ④Areas where power distribution lines are inaccessible or where electromagnetic waves are emitted ； ⑤It is not advisable to wear it if the person wearing the anti-static clothing feels an electric shock, experiences a shock while removing the clothing, or if there is a large amount of paint, resin, etc. attached to the workwear ； ⑥Washing should be done gently; strong acids and alkalis should not be used. Use the \"normal\" setting on the washing machine; do not use \"intensive wash\", and the cycle time should not exceed 20 minutes each time. (3) Wearing synthetic clothing is prohibited. Due to the high resistivity of fiber clothing, static electricity is likely to be generated, and the charge produced can hardly move and thus is difficult to dissipate; its discharge time can range from several hours to even several days. Therefore, wearing fiber clothing is prohibited in areas where flammable gases and liquids are present. (4) Soft chairs should be used with caution in areas with static electricity hazards. Getting up from a soft chair requires a significant amount of energy. According to tests, standing up from a soft chair with a synthetic leather surface charges the human body to 1.84 kV ； When getting up from a soft chair covered with polyvinyl chloride film, the human body acquires a charge of 1.8 kV. Therefore, soft chairs with insulating fabrics such as artificial leather, plastic, or synthetic fiber surfaces should not be used in areas with static electricity hazards.

Introduction to several methods of oil and vapor recovery during storage and transportation. Oil and vapor recovery refers to the process of collecting the volatile gasoline vapors that are generated during the loading and unloading of gasoline as well as when filling vehicles. Through one or a combination of methods such as absorption, adsorption, or condensation, this process either reduces the pollution caused by these vapors or converts them from a gaseous state to a liquid state, allowing them to be turned back into gasoline for reuse. 　　 Oil and gas recovery is an energy-saving and environmentally friendly high-tech solution. By using this technology to capture the oil and gas released during storage, transportation, and loading/unloading processes, it prevents air pollution caused by the evaporation of such gases, eliminates safety hazards, and increases energy efficiency thereby reducing economic losses – leading to significant benefits. Common methods currently include adsorption, absorption, condensation, and membrane separation. 1. Adsorption method: Separation of oil and gas from air is achieved by utilizing the adsorption capacity of adsorbents such as activated carbon, silica gel, or active fibers. The oil and gas pass through adsorbents such as activated carbon; the components of the oil and gas get adsorbed on the surface of these adsorbents. Subsequently, desorption is carried out under reduced pressure or using steam, and the concentrated oil and gas is pumped into oil tanks using vacuum pumps or liquefied by other methods ； Adsorbents such as activated carbon have very low adsorption capacity for air, and the unadsorbed exhaust gases are released through the exhaust pipe. 　　Advantages: The adsorption method can achieve a high treatment efficiency ； 　　The emission concentration is low, and can reach very low values. 　　Disadvantages: Complex manufacturing process, requires secondary treatment ； 　　Adsorption beds are prone to developing high-temperature hot spots, posing safety risks ； 　　Triphenyls can easily deactivate activated carbon, and deactivated activated carbon poses a problem of secondary pollution ； 　　The adsorption capacity of domestically produced activated carbon is generally only around 7%, and its lifespan is short – it usually needs to be replaced every 2 years or so. The cost of replacing activated carbon is quite high. 2. Absorption method: Separation of oil and gas from air is carried out based on the differences in solubility of various components in the mixed oil and gas within the absorbent. Generally, lean fuels such as diesel are used as absorbents. Generally, countercurrent contact is employed between the oil and gas and the absorbent sprayed from the top of the absorption tower; the absorbent selectively absorbs the hydrocarbon components, while the unabsorbed gas is discharged through a flame arrester. The absorbent then enters a vacuum desorption tank for desorption, after which the enriched oil and gas are absorbed using oil products. 　　Advantages: Simple process and low investment cost. 　　Disadvantage: The recovery rate is too low, typically only around 80%, failing to meet the current **standards ； 　　The equipment requires a large amount of space ； 　　High energy consumption ； 　　The absorbent is consumed in large quantities, so it needs to be replenished continuously ； 　　The pressure drop is too high, around 5000 pascals. 3. Condensation method: This method utilizes refrigeration technology to remove the heat from oil and gas, enabling a direct conversion of their components from the gas phase to the liquid phase. The condensation method is a technique for recovering oil and gas by taking advantage of the difference in vapor pressures of hydrocarbons at different temperatures; by cooling, the vapor pressure of certain hydrocarbons in the oil and gas is brought to a supersaturated state, and the supersaturated vapor condenses into a liquid state. A multi-stage continuous cooling method is generally used to lower the temperature of the oil and gas, causing them to condense into a liquid for recovery. The minimum temperature of the condensation unit is determined based on the composition of the volatile gases, the desired recovery rate, and the allowable concentration limits of organic compounds in the exhaust gases released into the atmosphere. 　　It is generally achieved through steps such as pre-cooling and mechanical refrigeration. The pre-cooler is a single-stage cooling device. To reduce the operational energy consumption of the recovery unit, a technology for reusing cold energy has been developed, which lowers the temperature of the gas entering the recovery unit from the ambient temperature to around 4°C, allowing most of the water vapor in the gas to condense into water and be removed. After leaving the pre-cooler, the gas enters the shallow cooling stage. The gas temperature can be cooled to –30°C to –50°C, which can be set according to requirements; nearly half of the hydrocarbons in the oil and gas can be recovered. The slightly cold oil and gas proceed to the deep-cold stage, where they can be cooled to temperatures ranging from –73°C to –110°C. The temperature is set according to specific requirements, and the compressors are configured accordingly. 　　Advantages: Simple process principle ； 　　The recycled liquid oil can be seen visually ； 　　High security ； 　　High level of automation. 　　Disadvantage: The single-condensation method requires temperatures to be reduced to very low levels in order to meet the standards. 4. Direct combustion method: This method involves directly oxidizing and burning the hydrocarbon-containing gases generated during storage and transportation; the carbon dioxide, water, and air produced as a result of combustion are then released directly as purified gases. This process flow serves only as a measure to control oil and gas emissions; it cannot recover oil products, nor does it offer any economic benefits. 5. Membrane separation method: Utilizing the property of special polymer membranes to allow hydrocarbons to pass through more easily, this method involves forcing a mixture of oil and gas along with air under certain pressure; as a result, the oil and gas molecules pass through the polymer membrane first, while the air components are retained and removed. The concentrated oil and gas are then transferred back to the oil tank or liquefied using other methods. 　　Advantages: Advanced technology, relatively simple process ； 　　Low emission concentration and high recovery rate. 　　Disadvantage: High investment cost ； 　　The membranes have not yet been made domestically; they are expensive, and their lifespan is short ； 　　Membrane separation devices require stable-flow, stable-pressure gas, and have high operational requirements ； 　　In conditions of low oil and gas concentrations and high air volume, the membrane is prone to forming a discharge layer, posing a safety hazard.

Classification of pipeline leak detection methods. Pipeline leak detection serves two main purposes: one is to prevent leaks from causing harm and pollution to people and the environment, and the other is to avoid losses due to leaks of the oil transported through the pipelines. Currently, the relatively practical pipeline leakage detection technologies can be roughly divided into two categories: direct detection methods and indirect detection methods. The direct detection method involves identifying the traces of the leaked liquid on the surface or the volatile gases. For example, leakage is detected by using leak detection cables, leak detection optical fibers, etc., to measure changes in characteristics such as the impedance and resistivity of the components after a leakage occurs. Alternatively, manual line inspection or inspections using airborne instruments can be employed to detect leaks. In recent years, the American company OILTON has developed an airborne infrared detection technology in which a helicopter carries a high-precision infrared camera and flies along pipelines, using the analysis of subtle temperature differences between the substance being transported and the surrounding soil to determine whether there are leaks in the pipelines. The indirect detection method is a technique for detecting leaks by measuring changes in physical parameters such as flow rate, pressure, and wave patterns in the pipeline system when a leak occurs. It is mainly divided into 3 types: 1. Real-time model method. The real-time model method is the most extensively studied approach; it involves combining real-time diagnostic systems with pipeline SCADA systems to carry out dynamic leak detection. 2. Mass balance method: Based on the principle of mass conservation, in a leak-free pipeline, the mass flow rate in must be equal to the mass flow rate out. The flow rates at the inlet and outlet of the pipeline are measured in real time; if there is a certain difference, it indicates that a leak may be occurring within the pipe section. 3. Signal-processing-based methods: At key points along the pipeline, the SCADA system uses sensors to measure parameters such as flow rate, temperature, and pressure in order to monitor the pipeline in real time. The data collected is sent to the central control room, where various algorithms are used for real-time analysis and processing, thereby enabling the detection and location of leaks. Analysis of changes in the pressure distribution along the line before and after a leak, or the propagation of negative pressure waves, is commonly used to detect leaks and locate them. This method includes the pressure gradient method, negative pressure wave method, pressure point analysis method, and statistical analysis method, among others. Currently, the negative pressure wave method is the most widely used in domestic oil pipelines. Since a single leak detection method often has certain limitations and finds it difficult to fully meet practical requirements, it is necessary to take into account the characteristics of various leak detection methods in application. Multiple detection methods can be used together to create a leak detection system that offers the best balance between reliability and cost-effectiveness. Compared to the other method, the direct leakage detection approach offers better sensitivity, higher positioning accuracy, and a lower rate of false alarms; however, it takes longer to conduct a complete inspection of the pipeline ； The indirect detection method can continuously monitor for leaks, enabling real-time surveillance of pipelines, but it has relatively low sensitivity and positioning accuracy, as well as a higher rate of false alarms.

Analysis of Hazard Factors in Oil Depots and Safety Countermeasures Oil depots play a crucial role in the petroleum and chemical production process, carrying out tasks related to transfer and storage and transportation. They serve as bases for storing oil products and as transfer stations for supply. Oil depots are specialized facilities used for receiving, storing, and distributing gasoline and diesel; they have large storage capacities, experience high levels of activity with frequent turnovers, and handle large volumes of oil per year. 1. Characteristics of oil depots: A high density of oil tanks, large capacity per tank, large total storage volume, and a variety of oil products stored. As warehouses for the transfer and storage of petroleum products, oil depots are prone to fire hazards due to the physical and chemical properties of these products. In the storage, transportation, and production operations at oil depots, activities such as the transport of oil products, loading and testing procedures, heating, insulation, and heat tracing for heavy oils with high freezing points, as well as inspections of oil tanks and various equipment and facilities, all involve the generation of static electricity, the use of high-temperature heating elements and a large number of electrical devices, as well as the use of open flames. All these factors undoubtedly pose a fire risk to oil depots. 2. Analysis of risk factors 2.1 Analysis of fire **risk factors (1) Analysis of the fire **risk characteristics of oils and fuels Oils and fuels are flammable and explosive ； Higher vapor pressure ； Prone to static electricity buildup ； Easy to diffuse, fluidity ； Characteristics such as easy expansion when heated⋯ Gasoline is a flammable liquid, while diesel is also a flammable liquid. Gasoline falls into Category A B, diesel belongs to Category C A, and light diesel is classified as Category B I, I ； Therefore, gasoline and diesel have a high fire hazard. (2) Analysis of **hazard characteristics of fires in critical areas of oil depots ① Oil tank area: The oil tank area is a key and vital part of an oil depot, as well as a major source of hazard. Due to frequent operations, the presence of numerous attachments and piping components around the oil tanks, and the storage of large quantities of flammable substances, this area is prone to accidents. Through analogous investigations and identification analysis, there are risks of accidents such as fires, oil mixing and leakage, work at heights, and personnel poisoning and suffocation. ②Oil unloading pump room: The oil unloading pump room is an important part of an oil depot. ③Fuel delivery area: The fuel delivery area is generally located at the entrance on the road-facing side of the oil depot; it is an important production area for carrying out wholesale operations of refined oil, with the ultimate goal of delivering fuel to the purchasing entities. The main facilities in this area include the fuel transfer pump room, fuel transfer area, and fuel transfer pipelines. There are also flow meter-based fuel dispensing systems for transaction settlement, as well as oil spill prevention devices, oil and vapor recovery systems, and static electricity discharge devices to ensure the safety of fuel transfer and to reduce environmental pollution. Obviously, this work area is crowded with people and vehicles, and there is high mobility ； There are many safety hazards ； It is difficult to manage, and accidents such as leaks, oil spills, and fires can occur very easily.** ④Railway loading and unloading area: A railway loading and unloading area is a facility dedicated to oil unloading, and it mainly includes dedicated railway lines and loading/unloading trestles. The areas prone to accidents and the potential hazards are as follows: (1) On dedicated railway lines, sparks from locomotive chimneys or activities related to furnace cleaning and slag removal can cause stray currents to enter the working tracks, leading to fires ； Failing to repair slope changes in a timely manner, or failing to secure tank trucks after they are aligned, which can cause them to slide, can also lead to fires. (2) Operational errors at the loading/unloading trestle, poor grounding leading to static discharge, and power distribution that does not meet explosion-proof requirements, resulting in sparks ； After use, the loading and unloading equipment is not returned to its proper position, or no fixing measures are taken due to poor balance, resulting in the equipment being damaged by pulling or pressing. 3. Safety countermeasures: The following safety countermeasures are proposed in light of the characteristics and risk factors of the oil depot. 3.1 Fire and explosion prevention measures: For a fire to occur in an oil depot, there must be a certain ignition source along with an oil-gas mixture within a specific concentration range. The basic measures for preventing fires and explosions are to prevent these two conditions from existing simultaneously – that is, to reduce the evaporation of oil, prevent the formation of explosive oil-gas mixtures, or to control and eliminate ignition sources, thereby avoiding any possibility of such sources igniting the oil-gas mixtures. Measures to prevent the formation of **flammable gas-oil mixtures are called primary prevention measures, while measures to eliminate ignition sources are called secondary prevention measures. Under normal circumstances, due to limitations in equipment and operating conditions, oil inevitably evaporates, forming explosive mixtures. Primary protective measures alone are not sufficient; secondary protective measures must be implemented to compensate for the shortcomings of the primary measures. Specific measures can be taken as follows. (1) Reducing oil evaporation and lowering the concentration of oil-gas mixtures: The main measures taken include: ① Preventing oil leaks ； ②Reduce the temperature difference inside the oil tank ； ③Use internal floating roof tanks ； ④Conduct oil and gas recovery to reduce oil product losses ； ⑤Improving equipment and operations ； ⑥Ventilation ； ⑦Inerting. (2) Controlling and eliminating fire sources. There are many types of ignition sources, each with its own characteristics; among them, electrical and open flames pose the greatest threat. 3.2 Lightning protection measures: The main objects that require lightning protection in oil depots are oil storage tanks, oil pipelines, loading/unloading pipes, pump houses on trestles, as well as some buildings or structures that are at a relatively high elevation. Its lightning protection measures mainly rely on conventional lightning protection devices, with some also using arresters and other devices for such protection. 3.3 Anti-static measures: For static electricity to act as a source of ignition and cause ** and combustion, four conditions must be met. To reduce and control its risks, ensuring safety is possible simply by eliminating one or several of these conditions. That is, to prevent and reduce the generation of static electricity ； Find ways to divert and neutralize the static electricity that is generated ； No static discharge with sufficient energy ； Prevent the formation of **flammable oil-gas mixtures. 3.4 Safe Electricity Use (1) The selection and installation of electrical equipment and wiring in oil depots must comply with the explosion-proof requirements of the respective areas; the working grounding and protective grounding must be proper and effective ； (2) Enhance awareness of safe electricity use, and strictly comply with the safety regulations set by electricity management authorities ； (3) Electricians must work with valid certificates, and safety procedures for electrical use must be strictly followed during operations ； (4) Electrical warning signs are prominent, and protective equipment is in good condition and effective ； (5) Electrical equipment and circuits shall be repaired in a timely manner in accordance with relevant regulations, and the grounding devices of the vehicles shall be tested and inspected ； (6) Thoroughly conduct testing and inspection of the grounding system ； (7) Carefully maintain records of the operation, inspection, and testing of electrical equipment ； (8) In the event of a power outage, explosion-proof safety lighting fixtures should be used. 3.5 Protection against falls (1) Strengthen safety education and training prior to starting work, enhance awareness of self-protection at the workplace, and wear appropriate personal protective equipment as required by the job requirements; avoid performing work in violation of regulations ； (2) The safety protection and lighting facilities are complete, warning signs are clearly visible, and the construction or work area is clean and free of debris, facilitating construction work and personnel evacuation ； (3) Strictly enforce labor discipline and operating procedures during construction; materials and equipment should be arranged neatly, reasonably, and in a safe and reliable manner. Tools used for inspection/maintenance must not be placed randomly on high areas such as the top of tanks, but rather in tool bags (boxes) ； (4) Strengthen the inspection and maintenance of safety protection measures, address any issues found promptly, and ensure they are in good working condition ； (5) Construction or work on tanks or other high locations is strictly prohibited in case of severe weather conditions such as winds above level 6. 3.6 Strengthen safety management to ensure the safe operation of oil depots

Transport of waxy crude oil: From the perspective of pipeline transportation, crude oil can be classified based on its flow properties into light crude oil with low solidification point and low viscosity, crude oil that solidifies easily, and heavy crude oil with high viscosity. Easy-to-solidify crude oil is crude oil with a high wax content, often referred to as \"waxy crude oil\"” ； The main problem in pipeline transportation of waxy crude oil is its high freezing point. The key to reducing the freezing point of wax-containing crude oil lies in targeting the wax present in the oil; for example, chemical or physical methods are used to alter the shape of the already formed wax crystals, making it difficult for them to combine and form structures, or to weaken the strength of any structures that have already formed. As a result, not only is the freezing point reduced, but the viscosity below the abnormal temperature point also decreases significantly. This is the current mainstream approach for reducing the pour point of waxy crude oils; methods such as adding pour point depressants and heat treatment all fall into this category. Processes for transporting waxy crude oil with reduced viscosity and solidification point: 1. Transport process via demulsifier modification; 2. Transport via thermal treatment modification; 3. Water-suspension transport; 4. Gas-saturation transport; 5. Other methods for reducing the solidification point and viscosity of waxy crude oil: modification methods such as light oil dilution and shear treatment, as well as upgrading methods such as dewaxing and cracking.

The disadvantages of heating oil for transportation: For both waxy crude oils and heavy oils, increasing the temperature can reduce viscosity; therefore, heating for transportation has become the most common method for transporting viscous, thixotropic crude oils through pipelines. However, it also has several inherent defects: 1. High energy consumption for transportation. According to statistics from the early 1990s, in China’s Northeast region, when 720mm pipelines were operating near full capacity, the annual fuel oil consumption per thousand kilometers for heating was approximately 0.4% of the oil transport volume, with a total energy consumption of around 410 KJ per ton-kilometer. Fuel consumption is higher when operating at capacities below the designed throughput ； The smaller the pipe diameter, the higher the relative fuel consumption. In the United States, for equivalent-sized isothermal pipelines transporting light crude oil, the total energy consumption per thousand kilometers is approximately 0.4% of the crude oil transported, with a total energy consumption of about 161 KJ per ton-kilometer. 2. The installation of heating stations increases the investment in pipeline construction, as well as the difficulties and costs associated with operation and management. 3. Due to the high freezing point of wax-containing crude oil and the high viscosity of heavy oil at low temperatures, if hot oil pipelines are shut down for an extended period, the crude oil inside the pipes can cool and solidify, leading to pipeline blockage accidents. 4. The heating delivery pipelines have a minimum allowable flow rate, and the allowable range of flow variation is narrow, making it difficult to meet the requirements of low-flow operation during the initial and final stages of oil field development. Furthermore, the heating and transportation management of crude oil with a large viscosity variation with temperature may lead to the pipeline entering an unstable operating zone during low-flow operations, putting it in a unsafe condition.

Damage and Maintenance of Anti-corrosion Coatings on Oil and Gas Pipelines
I. Main Types of Anti-corrosion Coating Damage
1. Peeling of the anti-corrosion coating
2. Scratching, cracking, and perforation of the anti-corrosion coating
3. Water intrusion into the anti-corrosion coating

II. Causes of Anti-corrosion Coating Damage and Failure
1. Inappropriate selection of anti-corrosion coating type
2. Poor quality of anti-corrosion repairs
3. Damage to the anti-corrosion coating due to external forces
4. Natural aging of the anti-corrosion coating
5. Inappropriate parameters for cathodic protection
6. Poor management

III. Maintenance of Anti-corrosion Coatings
1. Monitoring the condition of the anti-corrosion coating
Methods such as regular inspection for defects in the coating and measurement of its insulation resistance are typically used; when necessary, partial excavation is carried out to assess the coating’s appearance, adhesion properties, and degree of peeling. At the same time, the extent of corrosion on the pipe wall is also checked. Analyze the changes and causes of cathodic protection parameters to determine the quality and degree of damage of the anti-corrosion coating. (1) Inspection of the insulation resistance of the anti-corrosion layer; (2) Detection of defects in the anti-corrosion layer. 2. Hierarchical management of the anti-corrosion layer: Anti-corrosion layers on different pipe sections and in different conditions are classified according to their technical condition, and different maintenance measures are applied accordingly. Currently, petroleum asphalt anti-corrosion coatings are classified into five grades based on their insulation resistance values, from highest to lowest: excellent, good, medium, poor, and inferior. The worst-grade level requires the existing anti-corrosion coating to be replaced promptly. 3. Formulate and implement maintenance plans: For the anti-corrosion coatings identified at different levels through inspection, measures such as regular inspection, repair, or replacement are taken accordingly.