The pre-tightening of flange bolts is an important factor to ensure the sealing effect and prevent leakage of the flange connection system, and how to determine the tightening torque of flange bolts is the core issue in the flange pre-tightening process. This paper highlights the common methods for controlling the pre-tightening force of the flange connection system. In order to ensure the safety and reliability of the flange connection system, the paper puts forward a set of calculation methods for reasonably selecting the bolt tightening torque. Meanwhile, it points out the main differences in the selection of flange pre-tightening force and yield strength ratio in domestic and foreign specifications. And on this basis, the paper proposes a practical and reliable method for selecting the constant torque wrench to control the flange pretightening and sealing in engineering.

Printed circuit board heat exchanger (PCHE) is a microchannel heat exchanger based on chemical etching and diffusion bonding. When PCHE is applied to domestic offshore oil platforms, it often occurs that the heat exchange medium is supercritical natural gas. In order to explore the effects of different medium flow rates, different medium components and different plate structures on the flow and heat transfer characteristics of the heat exchanger, the physical properties, flow and heat transfer characteristic parameters of natural gas supercritical fluid are systematically analyzed by FLUENT software. The results show that the flow velocity has the most significant effect on the flow and heat transfer characteristics of the heat exchanger and the convective heat transfer coefficient increases linearly with the increase of flow velocity. The channel diameter is the second largest factor affecting the flow and heat transfer characteristics of the heat exchanger. The effects of different medium components, plate thickness and channel rib width on the fanning friction factor and average surface convective heat transfer coefficient of the heat exchange medium can be ignored. The research results can provide theoretical guidance for the process design of PCHE in the future.

Settlement separation is widely used in Chinese petroleum industry, but theoretical research on it obviously lags behind the structural design and application research. Based on CFD-DEM coupled model, this paper took the discrete phase oil droplets in the settling tank as the research object. It constructed the mathematical model of the settlement separation of oil droplets in the gravity field. By using the method of theoretical analysis and numerical simulation, the paper analyzed the motion characteristics of oil droplets in the process of settling, obtained the motion trajectory of oil droplets in the settling and separation process and grasped the changes of velocity and force in the process of oil droplets separation. By improving the inclination and the equivalent spacing of the inclined plate, it was determined that the inclination of the inclined plate with the best oil phase separation effect was 60° and the equivalent spacing of the inclined plate was 150 mm. With the above parameters, the oil removal efficiency can be increased from 64% to 82%. The results of this study can provide theoretical basis and data reference for revealing the mechanism of settlement separation and guiding the design of new high-efficiency settlement device.

The vacuum filter is the equipment for solid-liquid separation of sulfur slurry in natural gas desulfurization system. After separation, sulfur paste and filtrate are obtained. The following defects have occurred in the process of on-site use: 1) during the production of sulfur paste, the water content ratio of the sulfur paste is high, which may cause pollution; 2) abnormal equipment vibration occurs during the operation of the vacuum filter. Aiming at the above problems, the optimization is carried out from such aspects as vacuum filter operating parameters, equipment performance and abnormal vibration of the equipment. The specific optimization involves: 1) controlling the feeding speed, driving wheel speed and other operating parameters during sulfur paste production; 2) controlling the structural parameters of the equipment, including limiting the flow of filtrate branch pipe elbow and reducing the diameter from 65mm to 25mm and replacing the filter cloth of pore diameter 30 μm with that of 12 μm; 3) adjusting the valve opening according to the on-site working conditions, and conducting regular maintenance to eliminate the abnormal vibration of the vacuum filter. Through taking the above control optimization measures, the rate of water content of sulfur paste produced by vacuum filter is reduced from more than 35% to less than 25%, and the equipment vibration value is reduced from more than 10 mm/s to less than 7.1mm/s. The problems of high water content ratio and large vibration of sulfur paste are solved.

Vacuum pumps are very important rotating equipment in styrene extraction plants, which are used to ensure the vacuum degree of the process system. This paper analyzes the factors that should be taken into consideration in the selection of vacuum pumps. It points out that not only the operating parameters such as vacuum degree, gas volume and so forth, but also the medium characteristics should be taken into account. The analysis concludes that liquid-ring vacuum pumps are more suitable for styrene extraction plants. In addition, this paper also elaborates on the stage selection, anti-cavitation setting, seal configuration and energy-saving design of liquid-ring vacuum pump, which is intended to provide reference for engineering design.

Flue gas temperature is very high at the inlet of convection sections. High chromenickel alloy cast tube sheets are often used for supporting of convection coils. In recent years, leakage of convection coils often occur because of failure and cracking of cast tube sheets in use. This paper described the damage and replacement of the cast tube sheet of a foreign heater. Meanwhile, the stress analysis software ANSYS was applied to analyze and simulate the stress of the cast tube sheet under various working conditions, and the causes of cracking were found. According to the above reasons, the material of the original tube sheet was reselected and the structure of the tube sheet was redesigned to ensure the long-term safe and stable operation of the heater.

With the further internationalization of the projects, more and more refinery heaters need to be designed in accordance with foreign structural codes. This paper compares the code system, design principles, wind loads, seismic action, combination of loads, structural layout and practices of node in the design of heater steel structures between European codes and Chinese codes with the aim of providing reference for domestic engineering designers.

Except for a small amount of new content added in the part about gas stations in GB 50156—2021 Technical Standard of Fuelling Station revised on the basis of the original standard, most parts of the relevant content in the standard remain the same as the original one, and there are some ambiguities in the practical application. Based on the longterm practice of gas station engineering design, safety and fire protection design review, completion acceptance, safety evaluation review and safety inspection verification, the main reasons for the ambiguities are distinguished. The analysis indicates that the ambiguities are partly due to a small number of defects in the standard, but more likely due to people's misinterpretation. Therefore, it is proposed that the revision of national standards should be widely solicited for opinions to maximize the screening of errors and eliminate ambiguities and further improve the preciseness and authority of national standards. Meanwhile, this can also facilitate the relevant application personnel to achieve comprehensive understanding and correct application of the standards and to avoid misinterpretation and reduce ambiguities.

The upgrading and efficiency improvement of heating furnace is significant to the green and low-carbon operation of oil and gas gathering and transportation pipeline. Taking Weijing Line transporting 2,949 t/d of three-high crude oil (refers to crude oil with high wax content, high freezing point and high viscosity) as an example, this paper analyzes the transformation effects of pipeline heating furnace in detail from the aspects of oil properties, heating furnace working principles and furnace efficiency. The results show that compared with the traditional direct heating furnace, the vacuum phase change furnace has an increased efficiency of 12% and the average unit consumption of such furnace is reduced by 0.098 m³/t, which results in annual cost saving of 371,500 yuan. In addition, the annual emission of waste gas is reduced by 1.12 million m³, and the carbon dioxide equivalent (CO₂e) emission is reduced by 236 t. The goal of low-carbon emission reduction has been achieved by the transformation of heating furnace.

Star-shaped discharge valves are common equipment for powder conveying. Axial leakage tends to occur on both ends of the star-shaped discharge valve in the conveying process of high hardness powder. By analyzing the main reasons for the axial leakage fault of the star-shaped discharge valve, the improvement measures for rotor structure are proposed. The application results after the improvement show that wear resistance of the sealing surface can be improved by increasing the sealing surface hardness of the rotor shaft at both ends of the star-shaped discharge valve; wear on sealing surface can be reduced evidently and the service life of the equipment can be extended. Meanwhile, the rotor impeller is changed to a split structure, which is advantageous to rotor machining and equipment overhaul.

Coke tower is one of the important equipment in delayed coking unit. The scientific and effective periodic inspection of the coke tower is extremely important for the long-cycle safe and stable operation of the unit. This paper mainly introduces the application of collapsible umbrella lift platform in coke tower inspection and strength check analysis. The application results show that collapsible umbrella lift platform is used innovatively in the unit. On the existing drill pipe of the coke removal system, the existing drill pipe, drill winch, steel rope and other equipment are utilized cleverly to achieve safety and reliability, efficiency and time saving, and cost saving. Meanwhile, the testing data will provide important data support for the long-cycle operation and regular inspection of the coke tower.

Aiming at the problem of oil and gas long-distance pipeline being prone to corrosion failure, this paper conducted macroscopic and corrosion product analysis, metallographic analysis, chemical analysis, mechanical property testing, hardness determination, scanning electron microscopy and energy spectrum testing of the failure area and surrounding soil analysis of the natural gas longdistance pipeline. The results show that external mechanical damage first led to great damage defects and thickness thinning of the pipe wall, and also caused breakage of the external anti-corrosion coating of the pipe. Then the damage site was directly exposed to the electrolyte environment of the soil, and chemical or electrochemical corrosion occurred in the damaged site until the occurrence of the pipeline failure due to local wall thickness reduction. The above analysis demonstrates the general phenomenon of pipeline failure induced by mechanical damage during installation and subsequent corrosion during operation. According to the failure causes, this paper puts forward relevant recommendations and measures for the procurement, construction and installation, and operation and maintenance stages, which are of certain reference value for the handling of similar problems.

It has been a hot issue and difficulty in recent research to gradually reduce the dependence on manual identification by automatic identification of defects in radiographic inspection films. Due to the limitations of professional fields, technicians good at image identification do not know much about radiographic testing technology. Therefore, in order to do a good job in automatic identification of negative films, it is necessary for technicians to fully grasp the characteristics of defect images in radiographic films and the key factors affecting the identification including low transparency of negative film, small defect size, image edge blur, edge erosion effect, image deformation, imaging difference of area type defect, overlapping imaging, human factors, differences in standards or regulations and so on. This paper analyzes and studies the characteristics and key factors so as to provide reference for technicians engaged in automatic identification of radiographic inspection films to accurately grasp the image characteristics and elements of film defects.