How to carry out naked cooling after installation or repair of air separation equipment

After the installation or repair of the air separation equipment, the overall bare cooling shall be carried out.

Naked cooling purpose: check the quality of installation or repair of air separation equipment; Cold deformation and compensation capacity of air separation unit under low temperature; Whether the equipment pipeline is unblocked and can work normally.

Preparation before bare cooling: whether each unit equipment is normal after multiple test runs; Instrument control and electric control are put into operation and operate normally. Start the air separation unit according to the normal startup procedure to cool all the equipment and main pipelines in the cold box, and hang frost layers of different degrees. The measuring points meet the technical requirements, and the temperature of each reference point is allowed to be 5-10 ℃ higher in summer. In case of bare cooling, close the valve of liquid hydrogen to liquefaction storage system.

Work after bare cooling: tighten the bolts at low temperature with high speed; Sweep the frost in time; Conduct air tightness inspection after heating and inflation.

Before the overall cold test, the fractionator shall be fully heated and purged. Air turbine compressor, turbine expander, air precooling system, molecular sieve purification system (or switching system), electrical and instrument control system shall be prepared for good luck.

Operation method of cold test:

1. l) During the cold test, the distillation tower, condensing evaporator and other main equipment shall be cooled to the lowest temperature in turn, so that all containers, pipes and their outer surfaces in the cold box are covered with white frost, and shall be maintained for at least 2H.

2) During the cold test, organize personnel to enter the cold box (wear cold hat, gloves, cotton clothes, etc.) to strictly check the leakage part and mark it. For the cold valve and low-temperature film regulating valve, the nut can be tightened with special tools, and pay attention to whether the valve is stuck.

3) After the cold test (or natural reheating, as long as the manhole is opened), the air tightness test (or dynamic test) shall be carried out. Therefore, all bolts, flange connections, valves and other parts and components need to be tightened again. Pay special attention that the valve cannot be fully closed when tightening. The air tightness test pressure is the same as the working pressure.

Generally, the overall cold test shall be conducted twice. According to the leakage and treatment during the test, it is up to the site to decide whether to conduct the cold test again.

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