The bidirectional tensioning structure can play the role of combined reinforcement and precise positioning, which can enhance the strength of tube bundles to achieve vibration resistance, impact resistance and deformation resistance. Such structure can meet the performance requirements of shellandtube heat exchangers with special structures or special process conditions and address issues related to operation, manufacturing, and maintenance of tube bundles. Aiming at the phenomenon that there are fewer public thematic researches and regulations related to the engineering application of bidirectional tensioning structures in shellandtube heat exchanger tube bundles, this paper introduces the bidirectional tensioning structures applied in several different scenarios, explains the engineering principles, and also puts forward suggestions for the future development of the bidirectional tensioning structure engineering technology.

External fire is a common accident condition in petrochemical plants and safety valves are usually installed to prevent overpressure of pressure vessels. Reasonable calculation of the discharge capacity of safety valves in fire scenario is an important prerequisite for protecting the safe operation of pressure vessels. This paper provides an overview of the calculation formula for the discharge capacity of safety valves in fire scenario, and discusses the selection and determination methods of key parameters in the formula, aiming to provide reference for engineering designers.

The radial gap between the internal dynamic and static parts of the compressor in the ethylene plant is very small and sensitive to the external stress. If the compressor's connecting pipes are installed under stress, deformation or displacement of the body may occur. This in turn will cause change in concentricity between stator and rotor and then the occurrence of such problems as scraping between the rotor parts and static parts such as the spacer or air seal, coupling misalignment, bearing vibration and temperature overruns, and so on. Taking the installation of the compressor connecting pipes of an ethylene cracking plant as an example, this paper presents the methods to prevent the installation of the compressor connecting pipes under stress and the measures to relieve the residual stress in the compressor connecting pipes. This can be used as reference for the installation construction of connecting pipes of compressor unit under stress.

Centrifugal pumps may fail for a short time during the startup and shutdown phase of the equipment due to drastic changes in the internal pressure of the pump body, poor contact of the mechanical seals and so forth. Aiming at the problem of seal failure of upstream pumping mechanical seals under offdesign condition, this paper analyzes the failure causes. The analysis shows that the original dynamic pressure groove is unidirectional spiral, which is prone to poor sealing effect under offdesign condition of the equipment. And this is the root cause of the seal failure. In order to solve this problem, a new bidirectional interconnecting groove is designed by combining with the structural characteristics of bidirectional groove. The speed, pressure, and leakage of the fluid film in the bidirectional interconnecting groove are investigated by numerical simulation. The results show that the pressure at the top of the moving ring is the largest; the outer diameter speed of the sealing ring is maximum; when the groove depth is less than 6, the number of slots is between 8 and 10, the platform width ratio is 0.3 to 0.4, and the dam length ratio is less than 0.5, the mechanical seal can achieve good sealing effect under offdesign condition. Based on the results of the above study, the structural parameters of the bidirectional interconnecting groove are optimized.

The composite seal structure of highpressure heat exchanger is a new sealing technology. It has the features of compact structure, reliable sealing, low input cost, longterm use, convenient maintenance and so on. This structure is composed of Omegashaped seal ring (abbreviated as Ωshaped ring) and Cshaped seal ring (abbreviated as Cshaped ring), providing a dualsealing. This paper introduces the structures and manufacturing methods of Ωshaped ring and Cshaped ring. Combining with the design conditions of the highpressure heat exchanger of a fluidized bed residue unit, it also adopts ANSYS software to analyze and verify the composite seal structure and summarizes the advantages of composite seal structure compared with other seal structures of highpressure heat exchangers. The analysis results demonstrate that the composite seal structure combining Ωshaped ring and Cshaped ring can ensure leakfree and reliable operation of heat exchangers, offering a novel approach to address sealingrelated technical challenges in the manufacturing and application of largediameter highpressure heat exchangers.

Aiming at the problems of limited monitoring methods, scattered monitoring data, low data utilization, lack of early warning mechanism and backward maintenance mode in the equipment management of refining and chemical enterprises, the key parameters affecting the main equipment of petrochemical installations were analyzed to determine the warning values; an equipment monitoring and warning platform was developed. Various monitoring data were unified into a management platform to realize comprehensive data analysis and deep data mining, which facilitates the equipment management personnel to find out the hidden problems of equipment operation in time and take preventive measures to achieve preventive maintenance.

At present, there are many weak links in the management of mobile pressure vessels. For example, some use them in violation of regulations; some operate irregularly when filling, and there are loopholes in supervision. Thus, it is necessary to establish a system to collect objective information on the filling of mobile pressure vessels to regulate the management. Relying on the national mobile pressure vessel traceability platform, the dynamic monitoring system of the Internet of Things (IoT) for mobile pressure vessels installs explosionproof filling controllers at the site and configures explosionproof handheld terminals, which can realize the legitimacy determination of the mobile pressure vessels, the control of filling equipment and the data interoperability through the Internet of Things (IoT) and the Internet. Thus, the safety of the filling work of mobile pressure vessels can be enhanced. Meanwhile, the automation and informatization of the filling process can also be realized to improve the efficiency of mobile pressure vessel filling.

This paper addresses the problem of frequent leakage of mechanical seals in the CDU tower bottom pumps of a new refinery during the startup phase. By conducting failure mechanism analysis, seal structure analysis and DCS operational data comparison, the root causes of the seal leakage were determined to be seal face misalignment due to thermal deformation of the seal chamber, insufficient PLAN53B pressure settings and cooling deficiency caused by PLAN32 filter failure. A series of optimization measures have been taken to address the causes of the leakage including enhancing pump case insulation to mitigate environment thermal transients; raising PLAN53B pressure at nondrive end to prevent media backflow; installing PLAN32 orifice plates for precise flushing pressure control; implementing PLAN61 backcooling system to inhibit coke formation and substituting the original white oil with high flashpoint barrier fluid. After the implementation of these measures, the tower bottom pump runs smoothly, and the mechanical seal leakage has been permanently eliminated. This mechanical seal leakage solution can provide some reference for addressing mechanical seal failures of the same type of hightemperature oil pumps under complex operating conditions.

One year after the commissioning of a cracking furnace in an enterprise, cracks and leakage were detected in the welded joints of the mixer during operation. After shutting down the furnace for inspection, five cracks were identified in the mixer. To accurately determine the causes of the cracks, comprehensive analyses including macroscopic morphology, metallographic examination, hardness testing, and chemical composition evaluation were conducted on the welds, integrating factors such as construction practices and operational parameters. The investigation concluded that thermal fatigue cracking in the dissimilar steel welded joints was the cause of the leakage. This paper proposed targeted solutions to address the root causes discussed above.

A BCL405/A type recycle hydrogen compressor is used in the 3.3 million tons/year residue oil hydrogenation unit of one domestic petrochemical company. This compressor is a vertical split centrifugal compressor. During the normal operation of the unit, malfunction of the thrust bearing temperature indicator on the nondriven end of the compressor often occurs. This paper analyzes the reasons for the malfunction of the temperature indicator from two aspects including mechanical manufacturing and design of temperature lead wire of the bearing. Aiming at the causes of indication malfunction, it proposes such measures as improving the equipment lead method, adjusting the bearing mounting clearance, and increasing the lubricating oil pressure of the thrust bearing, which have completely solved the above problems. These measures can provide reference for future routine maintenance, repair and operation of similar compressors.

This paper systematically investigated the moving blade fracture in a fluid catalytic cracking unit flue gas turbine through comprehensive failure analysis approaches including material recertification, metallurgical analysis, scanning electron microscopy (SEM), strength calculation, and nondestructive testing (NDT). It is found from the analysis that the safety margin between the intrinsic frequency and the excitation frequency resonance of the moving blade is less than 10%; the machining accuracy is insufficient; and the minor fouling causes the rubbing of blade tip and so on. Aiming at the above problems, measures such as optimizing the design of highstrength twisted composite moving blades, enhancing shot peening hardening of the tenon teeth, eliminating stress concentration, performing finishing treatment on the shrouds, controlling the quality of raw material V and catalysts, and optimizing operational performance are taken to effectively ensure the longterm safe operation of the flue gas turbines.

A crane pipe elbow broke after being idle for 2 years at the seaside loading and unloading yard. In order to find out the root cause of the elbow cracking, its macroscopic morphology is carefully studied and the fracture, microstructure and chemical composition are analyzed. The analysis results indicate that there's a large amount of chlorine at the fracture of the elbow and the fracture is intergranular cracking; there's welding residual stress at the source of the crack. Further force analysis and calculation on it reveals that the outermost side of the crane pipe elbow generates tensile stress under its own weight. However, this stress value is much less than the yield strength of 304 stainless steel and the empirical value of weld residual stress (which is generally greater than 50% of the yield strength). Therefore, it is concluded that the reason for the fracture of the elbow is that the grain boundaries of 304 stainless steel sensitization occurs due to the presence of chloride ions, and eventually chloride stress corrosion cracking occurs under the action of welding residual stress. According to the cracking causes, this paper puts forward the corresponding countermeasures.