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In order to satisfy the corrosion resistance requirement, the original pipe material of a heat exchanger is replaced by BFe30-1-1white copper. Based on analysis of the welding characteristics, joint structure and factors affecting the welding quality of BFe30-1-1 tube-to-tubesheet, the welding procedure is made. The morphology inspection, test of pull-off strength, metallographic structure examination and hardness test of the tube-to-tubesheet joints which is welded according to the welding procedure, can satisfy the standard and design requirements. The success of the test provides a good reference for the welding quality control of white copper heat exchangers.

The fracture reason of the autoclave sterilizer was analyzed by metallographic examination, fracture analysis and chemical composition analysis. The results showed that failure of the autoclave sterilizer was due to stress concentration at the closed angle of poor fusion area by cyclic stress via vacuumizing and filling water vapor.

15NiCuMoNb has good mechanical properties, which is widely used in high-end equipment. However, the performance of existing material standards has been conservative in the past. In this paper the mechanical properties of 15NiCuMoNb at different temperatures are systematically studied. It is shown that the yield strength of the material decreases with the increase of temperature. The decrease tends would be slown after 200 °C, and the tensile strength of the material has similar characteristics. The least square method is used to obtain the prediction formula of the material in the range of 20~350 °C, which could be effectively predicted the mechanical properties of material. It could be useful to improve the accuracy of analytical design results, and provide a data basis for the revision of subsequent material standards.

High pressure hydrogen storage tank is a key component in hydrogen supply systems of the fuel cell vehicles. Composite hydrogen storage tanks own some advantages such as high stiffness, density and strength, and the composite tanks for storage of 70 MPa hydrogen is the hotspot of research. However, composite hydrogen storage tanks have the potential leakage and explosion hazards in the process of using due to the flammable and explosive storage medium. hydrogen cycle test is an important means to detect the macroscopic strength, safety margin, structure design rationality and reliability of composite hydrogen storage tanks. The relevant standard of 70MPa composite hydrogen storage tanks is not yet introduced in China. At present, the european union, Japan and the international standardization organization have formulated the composite hydrogen storage tanks standard or code, which have an important reference for the formulation of the relevant standards in china. In this study, foreign standards related hydrogen cycling test content such as (EU) 406-2010, ANSI HGV 2-2014, ISO CD 19881-2015, SAE J2579-2013 and ECE/TRANS/180-2013 are systematically studied, which could be helpful for the establishment of relevant standards in China and the development of hydrogen cycle test equipment.

20MnMoNb alloy steel is a structural steel for forgings with good mechanical properties, which is typically used in the manufacture of pressure vessel tube sheets. The mechanical properties of 20MnMoNb at different temperatures were systematically studied. It is shown that the 20MnMoNb material has the good high temperature resistance. With the increase of temperature, the yield strength and tensile strength of the material have little difference. The tensile strength is nearly 800MPa at high temperature, and the yield strength is about 643MPa, which could meet the complex working environment of the high pressure heaters. It is helpful to improve the accuracy of analytical design results and provide a data base for the revision of subsequent material standards.

Tubesheet is the main part of high pressure heater, which is very thick based on chinese code GB151 for the design of heat exchangers. Increased tubesheet with large thermal stress are not conducive to manufacture, heat transmission and detection. The stress and structure of tubesheet are so complex that the time costs too large during the analysis design, and stress classification exists uncertainty. Limit load method contributes to tubesheet lightweight. 3-D finite element model used for analysis design should be simplified reasonably. In this paper, the effect of mechanical model on limit load analysis of high pressure heater tubesheet conforming to the design-by-analysis code is researched. It is found that the tubesheet could pass the plastic collapse assessment, and the thickness of tubesheet could be decreased. The difference between the equivalent sold tubesheet model and the whole tubesheet model exists during plastic collapse assessment. Though the local stress distribution is different, the limit load results occurred plastic collapse by the equivalent sold tubesheet model is close to that by the whole tubesheet model. The limit load occurred plastic collapse is influenced by max circular diameter of tube layout little. The reason is attributed to original tubesheet owning enough rigidity related to thickness, and high stress appeares on the inner wall of jointing of tubesheet with head. The equivalent sold tubesheet model could be used for primary evaluation of limit load, and the whole tubesheet model is suited for partial analysis. The results provide some reference for the design-by-analysis of high pressure heater tubesheet.

Responding to non-conductive, non-magnetic material characteristics of polyethylene (PE) pipe, this paper comes up with the ground penetrating radar (GPR) detection for urban PE gas pipeline visualization research in order to solve the problems of positioning difficulty, and to avoid potential safety hazards caused by undefined positioning of PE pipeline, so that it can provide some experience to the application of position detection technology to locate buried polyethylene pipeline. Responding to the special material properties and welding form and based on the analysis of traditional ultrasonic testing for polyethylene butt-fusion joint, this paper comes up with an ultrasonic phased array dynamic focusing and S scanning imaging technology, to make a testing experiment on polyethylene butt-fusion joint. Results of the phased array ultrasonic testing of cracks in polyethylene butt-fusion joints shows that the testing method is feasible, and verifies the buried polyethylene butt-fusion joints engineering. This research would provide experience to the application of ultrasonic phased array technology in buried polyethylene pipeline inspection.

9Ni steel has good toughness and high strength. This paper focuses on the influence of vertical hole defects on the ultrasonic propagation characteristics, which are studied from two aspects of the propagation characteristics of the base metal and the ultrasonic waves of the weld, respectively. The acoustic reflection characteristics of the reflector are compared with the acoustic reflection characteristics of the two different welding processes, (manual welding and automatic welding). It is shown that the gain compensation of the weld is larger than the gain of the same diameter and the same position of the vertical hole in the base metal. The gain compensation of the automatic welding is larger than that of the manual welding. The ultrasonic attenuation in the automatic welding is larger than that of the manual welding. The results of the study contribute to improving the application of ultrasonic testing in 9Ni weld joints.

The cross-hole test block test, the acoustic emission characteristics of the system base metal, manual welding and automatic welding for each defect, the research shows that the attenuation of the ultrasonic wave in the base metal and the weld is different, and the attenuation in the weld is greater. Because the welding process causes the coarse crystal structure in the weld, the attenuation of the ultrasonic wave in the weld is increased, and the sensitivity of the weld detection is also increased. Ultrasonic waves pass through the manual weld seam longer than the automatic weld.

Finite element technology provides the basis for the complex structural analysis and calculation, which has been widely used in the design and evaluation of large-scale equipment. However, the time and cost of calculations are getting larger and larger due to complexity of the structure. How to improve the economics and rationality of calculations as much as possible under the premise of ensuring accuracy has become the focus of research. In this paper, the simplified high-pressure heater is taken as the research object, and the influence of different grid size on the calculation accuracy is shown. It is shown that the mesh size could be appropriately increased under the premise of the certain calculation accuracy, which could improve the calculation process and shorten the calculation time.

This paper focuses on the influence of vertical hole defects on the ultrasonic propagation characteristics, which are studied from two aspects of the propagation characteristics of the base metal and the ultrasonic waves of the weld, respectively. The acoustic reflection characteristics of the reflector are compared with the acoustic reflection characteristics of the two different welding processes, manual welding and automatic welding, and the properties of the base material. It is shown that the cross-slot of the weld is different from the cross-slot in the base metal, and the attenuation of the ultrasonic wave in the base metal and the weld is different. The gain compensation is too large, and the automatic welding gain compensation ratio of the upper groove of the weld is lower. The automatic welding gain compensation of the cross-slot is large, and the manual welding gain compensation of the lower cross-slot is higher than that of the automatic welding, and the cross-slot gain compensation of the automatic welding upper surface weld is higher than that of the manual welding.