VHS-250 Oil Diffusion Pump

Importance of the topic

Vacuum diffusion pumps are critical components for achieving and maintaining high and ultra-high vacuum conditions required in various industrial and research applications. The ability to reach pressure levels as low as 10⁻⁹ Torr enables processes such as vacuum furnace operation, thin-film deposition, and advanced coating techniques used in optics, electronics, and materials science. Reliable performance, minimal contamination, and efficient pumping capacity ensure consistent system operation and product quality.

Objectives and overview

This summary reviews the key features and performance specifications of the VHS-250 oil diffusion pump. It aims to provide a clear understanding of its design innovations, operational parameters, and suitability for high-vacuum and industrial applications. The data sheet presents pumping speed metrics, throughput capacity, physical dimensions, fluid requirements, and accessory information.

Methodology and used instrumentation

The VHS-250 design incorporates several engineering enhancements to improve efficiency and longevity:

• Stainless steel body and flanges: simplify cleaning and maintenance.
• Patented bulge contour: increases effective gas capture, maintaining lower ultimate pressures.
• Finned boiler assembly: expands surface area for the pump fluid, prolonging operational life.
• Sight glass with fill and drain assembly: allows continuous fluid level monitoring and easy servicing.

Performance specifications were determined using DC704 pump fluid under controlled conditions. A DS40M rotary vane pump with a minimum 17 cfm (29 m³/hr) capacity is recommended as a backing pump.

Main results and discussion

The VHS-250 diffusion pump delivers high pumping speeds and wide operating ranges:

• Peak pumping speed: 2,125 L/s for air, 2,660 L/s for helium and hydrogen.
• AVS 4.1 (1963) standard speed: 3,700 L/s for air.
• Operating pressure range: from 1.2 × 10⁻³ Torr down to < 5 × 10⁻⁹ Torr.
• Maximum throughput: 2.6 Torr-L/s (3.5 mbar-L/s) in operating range; 3.5 Torr-L/s (4.5 mbar-L/s) at 0.01 Torr.
• Backstreaming rate with standard cold cap: < 5 × 10⁻⁴ mg/cm²/min, minimizing contamination.
• Warmup and cooldown times: approximately 10 minutes each, aided by a quick-cool coil.

Electrical and cooling requirements include single-phase power at 120/208/240 VAC (2,200 W) and water flow of 0.25 gpm at 15–26 °C. The maximum forepressure tolerances are 0.65 Torr unloaded and 0.55 Torr under full load.

Benefits and practical applications

The VHS-250 offers several operational advantages:

• High and stable vacuum levels for advanced processes such as heat treatment, metallizing, and optical coating.
• Low contamination risk due to effective cold trapping and minimized backstreaming.
• Robust construction allowing for easy maintenance and extended fluid life.
• Flexibility to integrate with different backing pumps and system configurations.

Typical applications include vacuum furnaces, semiconductor processing, protective film deposition, and research laboratories requiring reliable high-vacuum performance.

Future trends and opportunities

Emerging trends in vacuum technology may influence diffusion pump design and usage:

• Development of advanced pump fluids with lower vapor pressures and higher thermal stability.
• Integration of real-time monitoring sensors and digital control for automated performance optimization.
• Hybrid vacuum systems combining diffusion pumps with turbomolecular or cryogenic pumps for extended pressure ranges.
• Eco-friendly materials and designs aiming to reduce energy consumption and fluid disposal impacts.

Conclusion

The VHS-250 oil diffusion pump represents a high-performance solution for achieving deep vacuum levels in industrial and research settings. Its design innovations, reliable specifications, and ease of maintenance make it well suited for demanding applications. Understanding its operational parameters and integration requirements ensures optimal system performance and longevity.

Reference

Agilent Technologies. VHS-250 Oil Diffusion Pump Data Sheet, document number 5994-3470EN, August 19, 2024.