Aiming at the condensation problem of cold nozzles on top of large LNG storage tanks, this paper takes the top feeding pipe of pre-stressed concrete full-capacity LNG storage tanks as an example. And it carried out a quantitative analysis of the five main factors influencing local condensation of cold nozzles by adopting a L16(45) orthogonal analysis method. The results show that the influence order of the five factors from the largest to the smallest are length of the insulating sleeve without outside insulation, atmospheric convective heat transfer coefficient, inner insulation thickness, the tempreture of atmospheric environment and length of the insulating sleeve. It can reduce the condensation probability effectively to increase length of the insulating sleeve without outside insulation, atmospheric convective heat transfer coefficient and inner insulation thickness in a certain range. And the larger the diameter of the cold nozzle is, the higher the condensation probability will be.

Under the action of design vacuum pressure and wind pressure, large storage tanks are prone to instability and failure. So reinforcing rings (or wind girders) are usually set to improve the stability of the oil tank walls. This paper focuses on comparing the instability formulas under external pressure for large storage tank walls in Chinese and American codes for design. Researches show that for atmospheric storage tanks, the basis for determining the instability of the tank walls under external pressure in Chinese and American codes is based on the theoretical formula for minimum critical pressure in short round cylinders. Shape deviation was considered in American design codes, while it was not consi-dered in domestic codes; for large storage tanks under external pressure, the wind pressure selection criteria for instability check formula of tank walls is inconsistent; both Chinese and American codes have not taken the factors of ground roughness (or landform category) and tank wall height into consideration. This paper proposes to take such factors into account when revising the relevant clauses in the codes.

In this paper, numerical simulation of shell flow field was performed on two kinds of baffle structure (the singlebow baffle and the staggered sector gap baffle) in shell and tube exchanger with ANSYS CFX14.0 simulation software. And the shellside pressure cloud map, temperature cloud map and fluid velocity vector diagram for two types of baffles were obtained; the shell heat transfer coefficient, shellside pressure drop and shellside unit pressure drop heat transfer coefficient of two types of baffles under six different flow conditions was compared. And then, this paper arrived at the conclusion that the integrated heat transfer performance of the staggered sector gap baffle is better than that of the single bow baffle heat exchanger, which is worthy of application and popularization.

Aiming at how to determine the temperature of the outer wall of the cryogenic storage tanks when calculating the cold leakage of the tanks, the formulas for calculating the average temperature and the maximum temperature of the outer wall of the storage tanks are deduced by using the outdoor temperature change rules and the heat transfer principles of solar radiation through analyzing the ambient temperature and solar radiation which are two main factors affecting the outer wall temperature of cryogenic storage tanks. The method for calculating the average temperature and the maximum temperature of the outer wall of the tank roof, the average temperature and the maximum temperature of the outer wall of the tank wall is demonstrated in the form of an example by using the derived formulas and relevant standards. The main influencing factors of the outer wall temperature of cryogenic storage tanks are identified and the method for reducing the outer wall temperature is proposed by analyzing the formulas and calculation examples. The application suggestions for the outer wall temperature of cryogenic storage tanks in the calculation of insulation and evaporation rate are put forward, and the application of the calculation method is expanded.

In this paper, the influence of stepless flow regulation system on the interstage pressure of reciprocating compressor is analyzed according to the thermodynamic theory formula. And then, based on the practical application, the active control of the interstage pressure of reciprocating compressor is discussed. This can provide some guidance for the application of stepless flow regulation system of reciprocating compressor.

In view of the single working condition of the performance curve of centrifugal compressors, it is difficult to adjust the working condition directly according to the curve in actual operation, and it is not convenient to carry out the operation optimization work. The performance curve and optimization measures of centrifugal compressor were studied. Taking a compressor station of Yuji pipeline as an example, the main performance parameters and calculation formulas of centrifugal compressor were analyzed; and the performance curves of energy head, power and variable efficiency were obtained by using the similarity criteria and curve fitting method; then the obtained performance curves were compared with the actual situation. The results indicate that the relative error between the actual energy head and the fitting energy head was within 2 ‰, which verified the accuracy of the fitting curve. The relationship curves of energy head, variable efficiency, pressure ratio and flow rate under different working conditions were obtained by adopting software programming. The changing law of the curves was analyzed, and the operation optimization measures under different working conditions were obtained.

Heat pump distillation is an energy-saving chemical separation process. Based on the actual industrial project of C4 heat pump distillation, the characteristics and selection schemes of different heat pump compressors (centrifugal compressor, reciprocating compressor and screw compressor) are compared. The isentropic compression characteristics of typical gases with different molecular weights (propane, n-butane and n-pentane) are analyzed. It is pointed out that liquefaction risk exists in mixed C4 during compression process. These provide reference for the selection of compressors for heat pump distillation.

This paper aims at the breakage of the inducer and gear fracture of the speed-increasing box in the imported high-speed water injection pump of a high-pressure residue hydrogenation unit in China. The sequence of failures was determined based on the vibration, displacement, flow and current in the operation trend. Through spectrum analysis, the fault frequency of bearings and gears was eliminated, and the cause of the fault was finally confirmed to be gear fatigue. In order to solve the above problems, the gear was replaced. A 1∶1 mapping of the gear was conducted by a domestic machinery and equipment research institute after contact. Meanwhile, a technical agreement was signed to specify many important parameters such as gear surface grinding accuracy, surface quenching hardness, dynamic balance grade and so forth. And the manufacturing of the gear was completed and the operation test was carried out in the processing factory. Then on-site installation was completed. After the gear was replaced, the vibration and noise were in normal range during operation.

Since the ultra-high pressure waste heat boiler of POX unit was put into operation, leakage has occurred in the large flange of the main body many times. By analyzing the reasons for the failure of the flange welding lip seal, it was confirmed that the sealing failure was related to three factors, namely: the large assembly deviation of the lip welding gasket, defective gasket welds and insufficient bolt pre-tightening force. The main factor for the failure was insufficient bolt pre-tightening force. At the end of 2015, the welding lip seal was replaced synchronously when the coil was replaced in the waste boiler. By improving the welding lip seal assembly process and welding process, and pre-tightening the bolts regularly, the problem was solved completely. After replacing the welding lip seal, there has been no leakage accident in the large flange of the main body so far.

This paper makes a deep analysis on the repeated tripping failures of the thrust bearing of the circulating oil slurry pump in heavy oil catalytic unit. Through collecting online monitoring data of bearing vibration and beginning with analysis on the acceleration spectrogram and envelope diagram, the paper arrives at the conclusion that the rolling element wear of the thrust bearing and the cage broken resulted from too much axial force produced by the impeller. According to the actual installation situation, the axial force on the top of the impeller is calculated quantitatively. Based on the main reasons for the thrust bearing failure, scientific treatment measures have been formulated to ensure the safe and reliable long-term operation of the circulating oil slurry pump.

As the main fluid mechanical equipment, pump is widely used in chemical industry, pharmaceutical industry, water conservancy, manufacturing and other fields. And the problems occurred in the practical application of pumps have attracted much attention. The key to solve these problems is to analyze the causes of the problems, improve the process conditions and enhance the performance of the equipment. Under the influence of catalysts in the quench water, the quench water pump in the MTO plant has obvious erosion wear. And under the influence of many factors including corrosion and cavitation, such wear has been intensified. So the frequency of equipment failure caused by wear increases, which greatly limits the long period, stable and efficient operation of quench pump. Aiming at the pump wear problem, the main reasons for the wear of quench water pump can be found from analyzing the quench water fluid characteristics, production operation and equipment materials. Corresponding protective measures for each major cause are taken. This can avoid or reduce the wear of the pump effectively. Among the protective measures, improving the characteristics of quench water is the key measure to alleviate the wear; and lifting pump material grade and applying wear-resistant coating materials are optional means to improve the wear resistance performance of the pump.

Direct monitoring of the pumping performance of liquid film seals is difficult to be put into effect. In order to test the performance parameters of the seals online, the monitoring method based on BP neural network is proposed. The pumpage and film thickness of liquid film seals under different pressures and revolving speeds are obtained through test firstly. The BP neural network is trained with experimental data. Output data of the network is gained by traversing input range method and the contour plots are drawn to be compared with the ones of measured data so as to assess the neural network generalization. Then, non-linear regression effects of five training functions are compared in three aspects involving generalization, accuracy and regression and the optimal BP neural network models are obtained. Finally, the monitoring effects of BP neural network are tested. And the results indicate that trainbr function is characterized by strong generalization and weak dependence on the number of hidden layer nodes. And BP neural network using trainbr function can satisfy the monitoring requirements for liquid film seals.

Blower steam turbine and induced draft fan steam turbine are important equipment of the 2500t/d methanol plant of certain company. The main oil pump installed at the shaft end of the steam turbine is a three-screw pump. During the operation of the two main oil pumps, the main safety valves of the main body have taken off frequently to varying degrees. By studying and troubleshooting the failure phenomenon, the problem was identified. According to the failure characteristics of the two main oil pumps, effective measures were taken involving redeploying the amount of oil in the main oil pumps of the blower and adjusting the opening of the self-regulating valve. For the induced draft fan, the equipment fault was eliminated through changing the speed ratio of the gear box of oil pumps to reduce the speed of oil pumps. The above-mentioned experience can provide reference for relevant technical personnel to deal with similar faults.