ULVAC Diffusion Pumps – High Vacuum & Ultra-High Vacuum Pumps
ULVAC Diffusion Pumps – Proven Technology for Deep Vacuum Applications
ULVAC diffusion pumps represent proven, mature technology for achieving high vacuum and ultra-high vacuum. These reliable pumps have been the workhorse of high vacuum systems for decades, delivering very deep ultimate vacuum, high pumping speeds, and dependable continuous operation. ULVAC offers a comprehensive range of oil diffusion pumps for research, industrial, and production applications.
🎯 What are Diffusion Pumps?
Diffusion pumps (also called vapor jet pumps) are fluid entrainment vacuum pumps that use high-velocity vapor jets to capture and remove gas molecules. They have no moving mechanical parts, making them extremely reliable and capable of decades of continuous operation.
⚙️ Operating Principle:
- Oil is heated in a boiler at the bottom of the pump
- Oil vapor rises through a central chimney
- Vapor is directed through multiple jet nozzles (stages)
- High-velocity vapor jets move downward at supersonic speeds
- Gas molecules are captured by vapor jets through momentum transfer
- Gas is compressed and pushed toward outlet
- Vapor condenses on water-cooled walls and returns to boiler
- Backing pump removes compressed gas from outlet
✅ Key Advantages of Diffusion Pump Technology:
| ⬇️ Very Deep Ultimate Vacuum | Can reach 10⁻⁷ to 10⁻¹⁰ mbar – ultra-high vacuum capability |
| 🚀 High Pumping Speeds | Very large pumping speeds available (100-50,000+ l/s) |
| 🔧 No Moving Parts | Extremely reliable – no mechanical wear, minimal maintenance |
| 💪 Robust & Reliable | Proven technology – can operate continuously for decades |
| 💰 Cost-Effective | Lower initial cost than turbo pumps for large capacity |
| 🔇 Silent Operation | Virtually no noise – no moving parts |
| ⚡ Simple Construction | Few components – easy to maintain and repair |
| 📊 Scalable | Available from small laboratory to very large industrial sizes |
📊 ULVAC Diffusion Pump Range:
🔷 Standard Oil Diffusion Pumps
ULVAC offers comprehensive oil diffusion pump series for various applications.
| Size Category | Inlet Diameter | Pumping Speed | Ultimate Vacuum |
|---|---|---|---|
| Small Laboratory | 50 - 100 mm (2" - 4") | 100 - 500 l/s | < 10⁻⁷ mbar |
| Medium Laboratory/Industrial | 150 - 250 mm (6" - 10") | 500 - 3,000 l/s | < 10⁻⁸ mbar |
| Large Industrial | 300 - 500 mm (12" - 20") | 3,000 - 10,000 l/s | < 10⁻⁸ mbar |
| Very Large Industrial | 600 - 1,000+ mm (24" - 40"+) | 10,000 - 50,000+ l/s | < 10⁻⁷ mbar |
✅ Standard Features:
- ✓ Multi-stage jet design (3-4 stages typical)
- ✓ Water-cooled housing and condensing surfaces
- ✓ Integrated heater with thermostat control
- ✓ Baffle or cold cap compatible (reduces backstreaming)
- ✓ ISO flange connections (standard sizes)
- ✓ Available in vertical or horizontal orientation
🔶 High-Performance Series
ULVAC's high-performance diffusion pumps feature optimized jet design for maximum efficiency.
- ✓ Optimized jet nozzles – higher compression ratio
- ✓ Enhanced cooling – improved condensation efficiency
- ✓ Lower ultimate vacuum – down to 10⁻⁹ mbar
- ✓ Higher throughput – better performance at all pressures
- ✓ Reduced backstreaming – cleaner vacuum
💎 Ultra-High Vacuum (UHV) Series
For ultra-high vacuum applications, ULVAC offers specialized UHV diffusion pumps.
| Feature | Specification |
|---|---|
| Ultimate Vacuum: | < 10⁻⁹ to 10⁻¹⁰ mbar |
| Materials: | Stainless steel construction, bakeable |
| Seals: | Metal seals, UHV-compatible |
| Oil: | Low vapor pressure diffusion pump oils |
✅ UHV Applications:
- Surface science and analysis (XPS, Auger, SIMS)
- Molecular beam epitaxy (MBE)
- Particle accelerators
- Space simulation chambers
- High-energy physics research
🏭 Large Industrial Pumps
For large-scale industrial processes, ULVAC provides very large diffusion pumps.
- ✓ Inlet diameters: 600-1,000+ mm (24"-40"+)
- ✓ Pumping speeds: 10,000-50,000+ l/s
- ✓ Applications: Large coating chambers, metallurgy, space simulation
- ✓ Heavy-duty construction for 24/7 operation
- ✓ Multiple heater zones for optimal performance
Available ULVAC diffusion pump types: Oil diffusion pumps, vapor jet pumps, high vacuum diffusion pumps, ultra-high vacuum diffusion pumps, UHV diffusion pumps, multi-stage diffusion pumps, laboratory diffusion pumps, industrial diffusion pumps, large-capacity diffusion pumps, bakeable diffusion pumps
🔩 Construction & Design Features:
⚙️ Core Components:
| Component | Material/Design | Features |
|---|---|---|
| Body/Housing | Stainless steel or aluminum | Water-cooled walls, corrosion-resistant, vacuum-tight |
| Jet Assembly | Stainless steel (3-4 stages) | Precision-machined nozzles, optimized jet angles, multi-stage compression |
| Heater | Electric resistance heater | Integrated thermostat, precise temperature control, overheating protection |
| Boiler | Stainless steel reservoir | Oil capacity: 0.5-5+ liters depending on size |
| Cooling Jacket | Water cooling channels | Efficient heat removal, condenses vapor back to liquid |
| Inlet Flange | ISO standard flanges | Various sizes: ISO-K, ISO-F, conflat (CF) for UHV |
| Outlet Flange | Standard vacuum connections | Connects to backing pump or fore-vacuum line |
🛡️ Special Design Features:
- ✓ Multi-stage jet design – typically 3-4 stages for optimal compression
- ✓ Optimized jet angles – maximize momentum transfer efficiency
- ✓ Efficient cooling system – rapid vapor condensation
- ✓ Integral fractionating stage – reduces backstreaming
- ✓ Thermostat control – maintains optimal oil temperature
- ✓ Safety features – overheating protection, cooling water interlock
- ✓ Easy oil filling – accessible fill port
- ✓ Viewing ports – allows visual inspection (optional)
🛢️ Diffusion Pump Oils:
The choice of diffusion pump oil is critical for performance and ultimate vacuum.
Oil Types & Selection:
| Oil Type | Vapor Pressure | Ultimate Vacuum | Applications |
|---|---|---|---|
| Hydrocarbon Oils | 10⁻⁶ - 10⁻⁷ mbar | 10⁻⁶ - 10⁻⁷ mbar | General industrial, coating (lower cost) |
| Silicone Oils | 10⁻⁸ - 10⁻⁹ mbar | 10⁻⁸ - 10⁻⁹ mbar | Standard high vacuum, most common choice |
| Polyphenyl Ether (Santovac) | 10⁻⁹ - 10⁻¹⁰ mbar | 10⁻⁹ - 10⁻¹⁰ mbar | Ultra-high vacuum, research, surface science |
| Perfluorinated Oils (Fomblin) | 10⁻⁹ - 10⁻¹⁰ mbar | 10⁻⁹ - 10⁻¹⁰ mbar | Oxygen service, corrosive gases, chemical resistance |
💡 Oil Selection Guidelines:
- ✓ Lower vapor pressure = deeper ultimate vacuum achievable
- ✓ Silicone oils – best general-purpose choice for most applications
- ✓ Polyphenyl ethers – for UHV, but expensive and sensitive to oxidation
- ✓ Perfluorinated oils – for oxygen or corrosive gas applications
- ✓ Never mix oil types – can degrade performance
- ✓ Regular oil changes – extends pump life and maintains performance
🏭 Primary Applications:
| Industry | Applications |
|---|---|
| 🎨 Vacuum Coating | Optical coatings, decorative coatings, tool coatings, large-area coating, web coating, evaporation |
| 🔥 Vacuum Metallurgy | Vacuum furnaces, degassing, vacuum melting, heat treatment, brazing, sintering |
| 🔬 Surface Science | XPS, Auger spectroscopy, SIMS, LEED, surface analysis, UHV chambers |
| ⚛️ High-Energy Physics | Particle accelerators, beam lines, synchrotrons, vacuum systems |
| 🚀 Space Simulation | Thermal vacuum chambers, satellite testing, space environment simulation |
| 🔬 Materials Research | Thin film research, MBE, crystal growth, materials processing |
| 🔌 Electronics | Vacuum brazing, electron beam welding, vacuum soldering |
| 🎓 Research & Development | University laboratories, research institutes, fundamental research |
🛡️ Backstreaming Prevention:
One concern with diffusion pumps is oil backstreaming – small amounts of oil vapor migrating back into the vacuum chamber. ULVAC offers several solutions:
Backstreaming Prevention Methods:
| Method | Description | Effectiveness |
|---|---|---|
| Baffle (Chevron Baffle) | Water-cooled chevron-style baffle above pump inlet | Good – reduces backstreaming by 90-99% |
| Cold Cap/Trap | Liquid nitrogen cooled surface above pump | Excellent – reduces backstreaming > 99.9% |
| Optically Dense Baffle | Multiple-angle baffle preventing direct line of sight | Very good – 99%+ reduction |
| Fractionating Stage | Additional top stage in pump design | Good – built-in reduction |
💡 Best Practices:
- ✓ Always use baffle or cold trap for clean vacuum applications
- ✓ Choose low vapor pressure oils (silicone or better)
- ✓ Maintain proper cooling water flow
- ✓ Avoid overheating the pump oil
- ✓ Regular oil changes minimize backstreaming
⚙️ System Configuration:
🔄 Complete Diffusion Pump System:
A typical diffusion pump system consists of:
- Vacuum chamber – the process vessel
- High vacuum valve – isolates pump from chamber
- Baffle or cold trap – prevents backstreaming
- Diffusion pump – main high vacuum pump
- Backing/roughing valve – controls backing line
- Backing pump – rotary vane, piston, or Roots + rotary vane
- Cooling water system – provides cooling to pump and baffle
- Vacuum gauges – monitor chamber and fore-vacuum pressures
⚡ Backing Pump Requirements:
| Backing Pump Type | When to Use |
|---|---|
| Rotary Vane Pump (Two-Stage) | Standard choice – most common, cost-effective |
| Roots + Rotary Vane | Large diffusion pumps – higher throughput needed |
| Rotary Piston Pump | Very large systems – maximum capacity and robustness |
| Dry Pump | Oil-free backing required (rare for diffusion pumps) |
🔧 Operation & Startup Procedure:
✅ Correct Startup Sequence:
- Ensure cooling water is flowing – critical before heating!
- Start backing pump – establish fore-vacuum
- Rough out chamber to ~10⁻² mbar with backing pump
- Close backing valve (if separate roughing line used)
- Turn on diffusion pump heater – wait for warm-up (20-30 minutes)
- Wait for pump to reach operating temperature – oil begins vaporizing
- Open high vacuum valve slowly – connect chamber to diffusion pump
- System reaches high vacuum – typically 10⁻⁵ to 10⁻⁷ mbar
✅ Correct Shutdown Sequence:
- Close high vacuum valve – isolate chamber from pump
- Turn off diffusion pump heater – stop heating
- Continue running backing pump for 15-30 minutes minimum
- Wait for pump to cool – oil vapors condense
- Stop backing pump (or keep running if system stays under vacuum)
- Continue cooling water until pump is cool
- Stop cooling water only after pump fully cooled
⚠️ Critical Safety Points:
- ⚠️ Never heat pump without cooling water! – will destroy pump
- ⚠️ Never shut off cooling water while pump is hot – thermal shock damage
- ⚠️ Never expose hot pump to atmosphere – oil can ignite
- ⚠️ Ensure backing pump running before heating – prevents oil oxidation
- ⚠️ Install cooling water interlock – automatic safety protection
🔧 Maintenance & Service:
📅 Maintenance Schedule:
| Task | Interval | Description |
|---|---|---|
| Visual Inspection | Weekly | Check for leaks, cooling water flow, proper operation |
| Cooling Water Check | Weekly | Verify adequate flow rate, check for blockages |
| Oil Level Check | Monthly | Check oil level in boiler, top up if low |
| Oil Condition Check | Quarterly | Check oil color and clarity – dark oil needs replacement |
| Oil Change (Normal Use) | 1-2 years | Drain old oil, flush, refill with fresh oil |
| Oil Change (Heavy Use) | 6-12 months | More frequent for contaminated environments |
| Pump Cleaning | 2-5 years | Disassemble, clean jets and interior surfaces, reassemble |
| Complete Overhaul | 10-20 years | Full inspection, part replacement if needed, performance testing |