The abnormal pressure at the boosting end of the air separation expander is mainly divided into three categories: excessively high pressure, excessively low pressure and frequent fluctuation. The reason is closely related to the mechanical state of the equipment, process flow and instrument control, which directly affects the stable operation of the air separation system. Under normal circumstances, the outlet pressure at the boosting end shall be 1.2~1.5 times of the inlet pressure, and the deviation shall not exceed ± 5%. If the deviation exceeds this range, it shall be deemed as abnormal.
Too high pressure is mostly caused by increased resistance or poor exhaust. Common causes include blockage and leakage of outlet cooler at supercharging end, resulting in poor heat exchange and blocked flow of gas; The outlet valve is stuck or the opening is insufficient, causing the system back pressure to rise; Freezing and blocking of main heat exchanger or pipeline, increasing gas flow resistance.
Too low pressure mainly results from insufficient air intake or reduced supercharging capacity, such as blocked inlet filter screen and decreased performance of molecular sieve adsorbent, resulting in insufficient air intake; Wear of impeller at supercharging end and sealing leakage cause gas leakage and decrease of supercharging efficiency; Improper closing of anti-surge valve and insufficient opening of inlet guide vane will also lead to low pressure.
Frequent pressure fluctuation is mostly related to control and mechanical failures, such as misoperation of inlet guide vane and misalignment of instrument measuring elements, resulting in abnormal regulation; Excessive bearing oil temperature and inflexible rotor operation affect the stability of pressurization; Instantaneous blockage of air circuit or signal interference will also cause pressure fluctuation. During troubleshooting, the working condition parameters shall be combined to comprehensively judge the root cause of the fault and timely handle it to ensure the safe and efficient operation of the system.
