Diffusion Pump Maintenance
Diffusion Pump Maintenance
Caring for a diffusion pump involves periodically changing the working fluid, cleaning internal components, and troubleshooting issues to maximise uptime. Establishing maintenance routines is essential for safety and performance.
Oil Changes
The working fluid in diffusion pumps can degrade from thermal stresses, chemical reactions, particulate contamination, and natural breakdown over time. Replacing the oil every 3-6 months guards against these issues. Oil condition should also be visually inspected monthly. Discoloration indicates a need for an oil change.
Cleaning Procedures
Diffusion pump interiors accumulate residue from back streaming, condensation, and general wear. Yearly cleaning involving disassembly and inspection should be scheduled. Clean using solvent baths or steam cleaning methods. Critical components like the boiler, nozzles, and vapour jet assembly may need refurbishment after several years.
Degassing of Diffusion Pump Oil
When oil is used as the working fluid in diffusion pumps, it can get contaminated by decomposition products that accumulate over time or from gases pumped from the vacuum chamber. This can negatively impact the pressure range and ultimate vacuum achievable.
To counteract this, diffusion pumps utilise a degassing section. The spent oil flows through this just before re-entering the boiler. Heaters raise temperatures in the degassing section to around 130°C. This causes more volatile elements in the oil to evaporate, essentially boiling them off.
These removed gaseous components are then exhausted via the backing line rather than returning to the freshly replenished boiler oil. This cleansing via heat prevents the bulk operating oil from being increasingly contaminated.
Over periods of continuous operation, large amounts of atmospheric gases, water vapour, carbons, silicone residues and other contaminants can dissolve in the oil. The degassing process ensures only the least volatile 'clean' fractions return to generate the high-velocity vapour jet. This restores pumping performance and helps meet specified ultimate vacuum levels.
Proper oil degassing arrangements are critical to the functioning of oil-based diffusion pumps. The purification by heat supports consistent functioning for industrial applications needing reliable high vacuums.
Troubleshooting Common Issues
High back streaming - clean baffles and cold cap. Check fore pressure. Replace fluid.
Poor vacuum performance - Leak detection. Clean pump body interior. Oil change.
Overheating - Check water cooling flow. Test heaters. Insulate exterior.
Unstable pressures - Inspect the backing pump. Fix flow control issues. Check oil level.
Oil leaks - Seal all joints and fittings. Replace gaskets as needed.
Foaming fluid - Wrong viscosity. Flush and refill oil. Degas oil.
With dedicated adherence to oil changes, cleaning cycles, and component lining, diffusion pump reliability stays high. Real-time monitoring and trend analysis also improves troubleshooting.
