How to prevent brittle failure in refining equipment

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Taking into account the various causes of brittleness in refining equipment mentioned earlier, preventive measures can be taken from aspects such as material selection, operation, and processing: optimize material selection by using materials with high toughness and low carbon content; for low-temperature conditions, use austenitic stainless steel, and for environments exposed to hydrogen, use special steels resistant to hydrogen embrittlement, thereby reducing the brittleness sensitivity of the materials themselves. Strictly control the operating temperature, avoiding the temper embrittlement range of 325–575°C and the 475°C embrittlement range of 371–538°C. Adopt a thermal start-up and shutdown procedure that involves raising the temperature first before increasing pressure, and reducing pressure first before lowering the temperature, with the rate of temperature change controlled at ≤25°C/h. To prevent hydrogen and corrosive agents from causing damage, it is necessary to maintain the wall temperature of the equipment above the dew point during shutdown periods. Equipment that is not accessible should be protected by filling it with nitrogen or ammonia. Austenitic stainless steel components that come into contact with air should undergo neutralization cleaning to avoid stress corrosion cracking caused by polyoxysulfuric acids. Optimize manufacturing and operation and maintenance to reduce stress concentration in the structure; control the thickness of components to prevent excessive thickness; eliminate residual stresses through post-weld heat treatment; conduct regular hardness and impact tests to identify potential risks of brittleness in advance.