| Summary: | 碩士 === 國立雲林科技大學 === 環境與安全工程技術研究所 === 88 === Recently, The chemical industries of the world have noticed the seriousness of the fracture of pressure vessel made of carbon steel, and was used in an adverse environment, especially the absorber, distillation column, endplate of heat exchanger, and pipelines etc. in the petrochemical industries. The fracture of pressure vessel is attributed to the corrosive environment, because there are frequently some acidic components, such as H2S, CO2 and other acidic gases in both gas and liquid phases. If hydrogen atoms permeate into the metal of facilities, it will cause the metal structure to crack. The reaction will continue and things get worse if it were left unattended. On the other hand, metals are also affected by the stress built up inside the pressure vessel and by chemical reactions. Consequently, the mechanical strength of the metal will decay, and ever causes an accident.
It is hard to tell whether the pressure vessel has been damage by hydrogen in the initial period of use. One way to solve this problem is to use higher quality material, which is so-call “Inherently Safety Design”. For this reason, to choose the applicable material which resist hydrogen’s attack is most important. The next step to do is to improve the manufacturing process, such as outgassing, reducing the operating temperature and pressure or lining the inside of vessel.
The pressure vessel designer also can choose the appropriate material for facilities and pipeline. Depending on the operating temperature and pressure, the refinery plant often use 2.25 Cr-1.0 Mo Steel or 2.0 Cr -0.5 Mo Steel in the hydrogen rich environment. Recently, the inspection technique of the refinery plant has made a great progress. Hence, the reliability of inspection for detecting the flaw and the crack of the facilities has improved significantly. The manager of the facilities also can utilize the fracture mechanical concept to evaluate the suitable material in corrosion environment. This study has constructed a computer program of “the evaluation program for assessing the fitness of metals in the corrosion environment”. The software is able to raise reliability of the facilities, coupled Risk-Based Inspection（RBI）strategy, the wish of facility safety hazard can be effectively reduced.
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