As well as known, fixed-roof tanks are vulnerable to fire and explosion accidents. To ensure the safe operation of atmospheric vertical fixed-roof storage tanks, it is essential to conduct fire and explosion risk assessments. In order to overcome the subjectivity of traditional analytic hierarchy process, improved analytic hierarchy process, and fuzzy fault tree analysis in the risk assessment of storage tank fire and explosion, a modified analytic hierarchy process was proposed in this paper. Meanwhile, the judgment matrix of modified analytic hierarchy process was constructed based on the optimized structure importance of the bottom event of the fault tree. Then, the weight factors of all indexes were calculated to evaluate the fire and explosion risk of the storage tank with fixed roof.
This study proposes a split-type pressure sensor based on differential capacitance that can be applied to in-situ accurate pressure testing in high-temperature environments. The sensor is mainly composed of a high-temperature resistant chip and a high-temperature resistant encapsulation structure. The chip is made of a ceramic substrate and presents a differential capacitance structure that can withstand high temperatures and effectively restrain the temperature drift. The encapsulation presents a split-type structure, in which the chip and the test circuit board are placed at the front and back ends of the sensor, respectively. Therefore, the front end of the sensor can work in the high-temperature area for in-situ testing, while the back-end temperature remains below 60℃ all the time, which ensures normal operation of the circuit board. Finally, the test results show that the pressure sensor's temperature drift coefficient is only 6.6% within the temperature range of 25°C-400℃. The sensor's sensitivity can reach 9.27 mV/kPa and the maximum repeatability error is less than 2.2% at 400℃, which shows that the proposed sensor has a higher working temperature and higher precision than the existing pressure sensors.
The fatigue performance of welded joints of submarine pipelines is directly related to the safety and economic benefits of welded structures. Considering the limitations of fatigue calculation, anti-fatigue design and small-scale fatigue test in the evaluation and analysis of pipeline fatigue life, this paper demonstrated the feasibility, scientificity and advancement of submarine pipeline full-scale fatigue test technology in engineering applications. Consequently, a full-scale fatigue test system and its test analysis technology applied for ZY-PFS2000 pipelines have been first developed in China, in which the effects of welding residual stress, stress concentration, initial welding defects, pipeline internal pressure shutdown and internal medium fluctuations on the fatigue life of full-scale pipelines were comprehensively taken into account. Through the full-scale fatigue test (four-point bending + internal pressure) of the X65 submarine pipeline, the fatigue cycles of different specifications of pipelines under different stress amplitudes were obtained. Moreover, the fatigue loading results were evaluated and analyzed in accordance with the international standard of BS 7608 and DNV C203. The research in this paper is conducive to accumulating full-scale fatigue performance data for submarine pipelines in China, not only offering a quantitative basis for the subsequent full-scale fatigue life evaluation and the safety operation cycle, but also providing a reference direction for the future development of submarine pipeline full-scale fatigue test technology.
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