Use and Maintenance of Diffusion Pump Oil

Pump oil—the "blood" of efficient diffusion pump operation. In industrial and scientific research fields that pursue high vacuum environments, diffusion pumps play a central role. Their performance largely depends on the key working medium, the pump oil. Like blood in the human body, the condition of the pump oil directly determines the health and efficiency of the diffusion pump. Proper use and standardized maintenance not only guarantee a stable ultimate vacuum but are also crucial for extending equipment life and reducing failure costs.

To ensure the long-term stable operation of the diffusion pump, the following three aspects are crucial:

Correct Charging: Strictly adhere to the "appropriate amount" principle.

Standard: Always strictly follow the oil quantity recommended in the equipment manual.

Risks of Insufficient Charging: Leads to decreased pumping speed, poor vacuum, and may cause the bottom heater to burn out.

Risks of Excessive Charging: Increases oil vapor backflow, contaminating the vacuum chamber, prolonging start-up time, and increasing energy consumption.

Preventing Oil Backflow: Cut off the main source of contamination.

Importance: Oil backflow is the primary cause of vacuum system contamination and severely impacts process quality.

Solution: Properly configuring a cold trap (liquid nitrogen cold trap or electrically cooled baffle) above the pump inlet can efficiently condense escaping oil vapor, reducing the backflow rate by several orders of magnitude. This is an essential measure to ensure chamber cleanliness.

Regular replacement: Identifying signs of oil failure. Causes of failure: Pump oil gradually deteriorates in performance due to high-temperature oxidation, thermal cracking, and the intrusion of external contaminants during long-term operation.

Inspection Methods:

Visual Inspection: High-quality pump oil should be clear and transparent. If the oil becomes darker or cloudy, or if sediment/suspended matter appears at the bottom, it is a clear sign that replacement is necessary.

Replacement Schedule: A reasonable periodic replacement plan should be developed based on factors such as equipment usage frequency and operating pressure.

Common Problem Diagnosis and Solutions

When a diffusion pump system malfunctions, refer to the following list for quick troubleshooting of pump oil-related issues:

Problem 1: Vacuum cannot be achieved

Possible causes: Pump oil is faulty or contaminated; insufficient oil level; degraded back pump performance leading to excessive back pressure.

Problem 2: Severe backflow

Possible causes: Heating power mismatch (too high or too low); cooling water system malfunction resulting in insufficient cooling; incorrect pump oil type selection; baffle/cold trap not installed or not open.

Problem 3: Black coking appears in the pump body

Diagnosis: This is a clear sign of thermal cracking of the pump oil, usually indicating severe oil deterioration or excessively high heating temperature.

Action: The pump must be stopped immediately, the oil completely replaced, and the pump body thoroughly cleaned to remove all coking deposits.

Pump oil management is an essential aspect of diffusion pump maintenance. By mastering correct operating procedures, establishing preventative maintenance processes, and quickly diagnosing and resolving common problems, equipment performance can be maximized, ensuring the stability and repeatability of production processes, ultimately reducing costs and increasing efficiency for the enterprise. Establishing a scientific pump oil maintenance system will provide your vacuum system with a long-lasting and reliable power source.