It usually occurs in the refrigeration system of low-temperature cold storage, or due to the selection of high freezing point and inferior refrigeration oil. Because the freezing point of inferior refrigeration oil is high, it may cause the refrigeration lubricating oil to flow through the valve hole of the thermal expansion valve after mixing with the refrigerant. , Due to the sudden drop in temperature, part of the lubricating oil is precipitated from the refrigerant and frozen into a thick paste, causing the valve hole of the thermal expansion valve to be blocked. When encountering the problem of oil blockage in the refrigeration system, it is usually necessary to replace the refrigeration oil.