Welch Belt Driven Rotary Vane Pump

Proven Performance and Robust Design


A belt-driven vacuum pump is a type of rotary vane pump that uses a flexible V-shaped belt to transmit mechanical power efficiently from the motor to the vacuum pump module.  Compared to direct-driven vacuum pumps, the rotational speed of belt-driven vacuum pumps is approximately 1/3 slower, which reduces wear and minimizes temperature to decrease oil degradation.

Welch’s portfolio showcases belt driven pumps that stand out for their precision engineering and consistent performance. Designed with care, they offer a balance of reliability and efficiency. Their adaptability makes them suitable for various settings, from research to industrial and academic environments.


What Is a Belt Driven Vacuum Pump?

A belt-driven vacuum pump is a mechanical system utilizing a flexible V-shaped belt to efficiently transmit mechanical power from the motor to the vacuum pump module. Distinguished by its approximately 1/3 slower rotational speed compared to direct-driven vacuum pumps, this design offers multiple benefits. 
These include minimized friction and wear on internal rotary vane components, leading to extended service intervals and a longer pump lifetime. The reduced rotational speed also results in cooler pump operation, approximately 20°F lower than many high RPM direct-driven vacuum pumps, mitigating chemical activity within the pump and reducing rates of oil consumption. 
Furthermore, the slower rotational speed allows for an extended gas-filling time in the internal pump cavity during rotation, enhancing pumping efficiency and facilitating shorter pump-down times for vacuum chambers to achieve low mbar pressures.


Why Welch Belt-driven Vacuum Pumps are Proven Performers?

Welch's belt-driven vacuum pumps have proven their reliability over the span of decades, backed by the largest installed base and continuous refinement. This enduring performance stems from a thoughtful design approach that prioritizes ruggedness, featuring a substantial oil reservoir for contaminant dilution, a lower RPM to mitigate internal wear, and a simplified structure with fewer moving parts to enhance overall durability.
The cool operating temperature of Welch pumps contributes to a prolonged oil life, minimizing oil backstreaming and necessitating fewer maintenance interventions and oil changes. Beyond durability, these pumps demonstrate high efficiency in pumping, resulting in reduced pump-down times. This efficiency ensures a consistent, clean vacuum and stable pumping even when operating in the low mbar range. Welch's belt-driven vacuum pumps offer an educational insight into a reliable and resilient solution for various vacuum applications.


How Do Welch Belt-driven Vacuum Pumps Operate?

Welch Belt-driven Vacuum Pumps operate as oil-sealed mechanical pumps, achieving low mbar pressures by steadily removing air through rotating elements in the pump module. The pump's cycle involves gas being drawn into a vacuum-tight space, compressed, and expelled, reducing pressure in the chamber over time. A thin oil film seals rotor and vanes, lubricates parts, and aids heat transmission. 
The pump's specially formulated oil, with low vapor pressure, allows it to reach low mbar pressures. The large oil reservoir dilutes contaminants, drawing clean oil from the top. A built-in gas ballast keeps the pump oil clean by introducing atmospheric air when opened. These pumps come in one or two-stage configurations, with multiple stages achieving a higher compression ratio for lower ultimate pressure.


Where Are Welch Belt-driven Vacuum Pumps Used?

Belt-driven vacuum pumps find common applications in laboratory, industrial, and HVAC settings where extended service life is crucial. Some key uses include:

Schlenk Line (Vacuum Manifold)

  • Widely used in organic and inorganic laboratories.
  • Ideal for achieving low ultimate pressure in the final drying step of samples from a rotary evaporator.
  • Suitable for manipulating oxygen and water-sensitive compounds.
  • Recommendations include a cold trap and an acid neutralization trap, particularly when dealing with strong acids.
  • Larger capacity pumps may be required for optimal performance.

Glove Box Transfer Chamber

  • Effective in high-purity atmosphere metal glove boxes.
  • Draws a deep vacuum in the transfer chamber before backfilling with dry nitrogen.
  • Ideal for rapid cycling.

Refrigeration Servicing

  • Known for providing a deep vacuum for quick evacuation and dehydration of HVAC systems.
  • Enables efficient and swift completion of servicing tasks.

Vacuum Oven Drying

  • Well-suited for applications requiring sample drying, back-out, and curing to low mbar range with short cycle times.
  • Recognized for durability and ruggedness in vacuum oven applications.
  • An in-line cold trap is recommended when pumping chemical vapors.

Freeze Drying for Corrosive Vapors

  • Tolerant of chemical contamination due to the design of belt-driven vacuum pumps.
  • Using a synthetic hydrocarbon oil, such as Gold oil, provides resistance to chemical attack.

Roughing Vacuum Chambers

  • Selected based on the type and free air displacement needed for evacuating chambers, annular spaces, and transfer lines.
  • Pumping capacity determined by the rule of thumb (1 to 1.5 times the volume of space).
  • Chosen for fast pumping speed below 0.13 mbar.


Types of Welch Belt-driven Vacuum Pumps

Welch offers a range of belt-driven vacuum pumps, including four main types:

DUOSEAL® Vacuum Pumps

  • Common and versatile, known for low RPM design.
  • Maintains high pumping efficiencies into the low mbar range.
  • Most DUOSEAL pumps are two-stage, providing a lower ultimate pressure.
  • Utilizes Welch DUOSEAL oil for optimal performance.

CHEMSTAR® Vacuum Pumps

  • Specially designed for pumping corrosive gases.
  • Features corrosion-resistant components for enhanced durability.
  • Includes an oil bubbler for inert gas purging, extending the pump's service life.
  • Equipped with Welch Gold Oil for resistance to corrosive gases or vapors.

HVAC Service Vacuum Pumps

  • Proven performers in HVAC applications.
  • Low pump RPM ensures a long service life.
  • Large oil reservoir dilutes contaminants, providing deep vacuum for fast evacuation and dehydration.
  • Comes with refrigeration intake fittings for easy attachment to HVAC systems.

CAPTURE Pump (Model CRR-1A)

  • Specifically designed for low-pressure refrigerant recovery and recycling systems.
  • Ductile iron oil case allows maximum boosting of refrigerant vapor.
  • Accommodates evacuation pressures greater than 29.9 in. Hg.
  • Comes with DUOSEAL oil for optimal oil separation.