Alcohol-based additives in wastewater volatilize under low-temperature, negative-pressure conditions to form alcohol vapor, which enters the vacuum pump along with non-condensable gases. Prolonged contact with the vacuum pump oil triggers multiple forms of degradation and causes damage to the pump components. The entire process is as follows. Alcohol vapor possesses a certain degree of solubility; upon entering the oil chamber, it dissolves and diffuses directly into the vacuum pump oil. First, it dilutes the base components of the vacuum oil, reducing the oil’s overall viscosity. As viscosity decreases, the oil film struggles to adhere stably to the rotor and blade clearances, causing a continuous decline in sealing performance. The unit’s ultimate vacuum gradually deteriorates, making it difficult to maintain vacuum levels in the evaporation chamber, which directly impairs evaporation efficiency. At the same time, lubrication capacity weakens, friction between the vanes and bearings intensifies, pump operating noise increases, and bearing wear accelerates. Since alcohols are polar substances, they can degrade the antioxidant additives in the vacuum oil, accelerating the oil’s oxidation and deterioration. During prolonged operation, the oil’s color gradually darkens, viscous, gel-like oxides form, and the oil becomes emulsified and cloudy. Gummy deposits adhere to the inner walls of the pump chamber, the exhaust valve plates, and the oil circuit filters, causing poor exhaust flow and increased pump body heat generation. This further promotes the volatilization of alcohol vapor and the degradation of the oil, creating a vicious cycle. Alcohol vapor carries trace amounts of condensed water vapor; when water and alcohol coexist, it is highly likely to cause the vacuum oil to emulsify. Emulsified oil loses its original physical and chemical properties, not only causing seal failure but also producing acidic substances that cause mild corrosion of the cast iron pump chamber and vanes, resulting in pitting and rust spots. The oil-water-alcohol mixture also continuously generates foam; excessive foam inside the pump can cause oil spray issues, leading to oil leakage from the exhaust pipe. Some alcohols are hygroscopic and weakly polar, which can cause small amounts of organic acids and trace salt mist in wastewater to enter the oil pump along with the vapor. Over time, these accumulate to form suspended impurities. These impurities continuously abrade the precision mating surfaces inside the pump, causing clearances to widen, increasing vacuum pump leakage, and resulting in irreversible deterioration of vacuum performance. Furthermore, alcohol dissolved in the oil continuously volatilizes toward the exhaust port. As temperatures fluctuate, it repeatedly condenses and evaporates, constantly carrying away effective additives from the oil. This significantly shortens the oil’s service life and increases the frequency of oil changes. In addition to the degradation of the oil itself, there are also cascading process effects. The volatilized alcohol vapor flows back through the vacuum piping; some of it condenses in the low-temperature sections of the piping, and the resulting liquid is periodically drawn into the pump, continuously contaminating the oil. If a downstream activated carbon adsorption unit is installed, insufficient adsorption allows alcohol to continue penetrating, failing to prevent damage to the vacuum pump. Recommendations for operational improvements: Install a condenser at the front end of the vacuum system to fully recover alcohol vapor, and pair it with a gas-liquid separator to reduce droplet carryover; add a low-temperature adsorption tank to the vacuum pump’s inlet to intercept organic vapors; shorten the sampling and testing cycle for vacuum oil, and replace the oil promptly upon any signs of cloudiness or decreased viscosity to prevent permanent wear on the pump housing.