Practical Operation Specification for Vacuum Extraction in Cold Storage | First level Coarse Extraction, Second level Fine Extraction, Vacuum Recovery, Negative Pressure Side Water Inlet Avoiding Pit
The purpose of vacuuming is to remove air and water vapor from the pipeline. Water vapor left in the system can cause hydrolysis and acidification of POE refrigeration oil, as well as continuous ice blockage, which is a hidden long-term fault source.
Standard procedure: First, perform a rough draw to around 500Pa; Perform secondary precision pumping, with a target vacuum degree of ≤ 100Pa. After pumping, close the valve and let it stand for 2 hours to maintain pressure.
The Xitelide unit has already been pre evacuated internally before leaving the factory, and only external pipelines are being evacuated on site; After the overhaul of the whole machine and the cutting of the pipeline, a complete second vacuum must be applied, and it cannot be applied for just a few minutes.
Vacuum rebound judgment: Let it stand for 2 hours, and if the pressure rebound is ≤ 150Pa, it is qualified; Rapid recovery indicates slight leakage or residual moisture in the pipeline.
Many masters only finish pumping for a dozen minutes, and the vacuum gauge reading is very low. The water adsorbed on the inner wall of the pipeline is not fully analyzed, and after adding refrigerant, the water vapor is slowly released.
Vacuum extraction cannot be done by the compressor itself, as the lubricating oil and seals inside the compressor are easily damaged by negative pressure and can also contaminate the system with oil vapor.
Construction in high humidity weather increases the difficulty of vacuuming. It is recommended to use nitrogen blowing to remove free water vapor before vacuuming on the machine to improve the efficiency of vacuuming.
Negative pressure cold storage, long pipeline quick freezing tunnel, with large pipeline volume, need to be matched with high flow vacuum pumps, small diameter vacuum pumps to pump large systems, which cannot dry and takes a long time.
The voltage at overseas construction sites for foreign trade projects is unstable, and the vacuum pump is prone to speed drop, making it difficult to meet vacuum standards. In the plan, it is recommended to provide a stable voltage power supply or reserve longer vacuum pumping hours.
After passing the vacuum test, priority should be given to filling the refrigerant. Do not maintain high vacuum for a long time, as water vapor in the air will seep back into the pipeline through small leakage points.
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FAQ
1. Second level precision pumping target vacuum degree? ≤100Pa。
2. How long should it be kept under pressure and left to stand? 2 hours, with a rebound of ≤ 150Pa, qualified.
3. Can I use a compressor to vacuum myself? Strictly prohibited, as it may damage the compressor.
What does fast vacuum recovery represent? There are leaks or residual moisture.
5. What are the suggestions for vacuuming in humid weather? First, blow with nitrogen and then evacuate.
6. Hidden dangers of short-term vacuum pumping? The adsorbed water on the pipe wall has not been released, resulting in ice blockage in the later stage.
What should be done as soon as the vacuum is qualified? Add refrigerant and avoid long-term vacuum storage.
