In bare cooling, the main equipment such as the distillation tower and main condenser evaporator should be sequentially cooled to the lowest temperature for 2 hours each. Then cool the entire air separation equipment until it reaches equilibrium temperature, so that all equipment pipelines have white frost on their surfaces, and maintain it for 3-4 hours.
In the cold state, each part should be carefully inspected for deformation and leakage. The location of the leakage point can be determined based on the frost formation and should be marked. After freezing, the flange screws should be tightened again to compensate for the screw relaxation caused by different thermal expansion coefficients at low temperatures. But it should also be noted not to tighten too tightly to prevent excessive prestressing. Then sweep the frost and avoid melting it in the insulation box, which may affect the filling of the insulation material. Heat it again to room temperature and conduct an air tightness test.
If there are any treatment items, they need to be exposed again after treatment. The number of times and qualification standards for bare cooling depend on the specific situation. After the bare cooling is qualified, each adsorber is loaded with adsorbent, and the cold insulation box is filled with cold insulation materials.
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