Selection of Roots Water Ring Vacuum Unit

The core principles for selection are matching operating conditions, balancing performance, and saving energy and reducing consumption. Based on key parameters such as the required vacuum level, pumping speed, and gas properties of the pumped system, priority should be given to the following four aspects:

1. Vacuum Parameter Matching

The ultimate vacuum of the unit shall be 0.5 to 1 order of magnitude higher than the operating pressure of the pumped system to ensure process requirements are met with sufficient margin and avoid substandard vacuum caused by condition fluctuations.

Low vacuum demand (0.1~1 kPa): Basic configuration is recommended; excessive ultimate vacuum should be avoided to prevent energy waste.

Medium–high vacuum demand (1.65 Pa~0.4 kPa): Conventional optimized configuration is preferred for balanced performance and cost-effectiveness.

High vacuum demand (≤25 Pa): High-level configuration is required, using multiple Roots pumps in series with a two-stage water ring pump, or adding an atmospheric ejector to achieve higher ultimate vacuum.

2. Pumping Speed Matching

Pumping speed matching includes two levels: matching between the main pump and backing pump, and matching between the overall unit and the pumped system.

Main pump & backing pump matching: The pumping speed ratio of the Roots pump to the water ring pump should not exceed 2. Insufficient backing pump capacity will cause poor exhaust, overheating, and overload of the Roots pump, reducing unit performance.

Unit & system matching: Select a unit with an appropriate pumping speed range according to the system volume and gas generated during the process, to avoid slow vacuum buildup due to insufficient speed or energy waste from excessive speed. Common pumping speeds range from 30 to 600 L/s for flexible selection.

3. Adaptation to Pumped Gas Properties

Gas properties directly determine the unit configuration and auxiliary accessories, especially regarding condensable vapor, solid impurities, and corrosive components.

Gas containing condensable vapor (e.g., vacuum drying, distillation): A condenser should be installed, preferably at around 45 Torr, using 30~35℃ cooling water to reduce pumping load. A gas-ballast mechanical vacuum pump can be connected in parallel to improve high-vacuum retention.

Gas containing solid particles/dust (e.g., chemical, mining applications): A dust collector/filter must be installed at the suction port to prevent impurities from entering the pump chamber, causing rotor wear, seal damage, or pipeline blockage.

Corrosive gas: Corrosion-resistant materials (such as aluminum bronze impellers) and seals shall be used, and working fluid selection optimized to minimize corrosion.

4. Energy Consumption & Maintenance Adaptation

Selection shall balance energy consumption requirements, maintenance convenience, initial investment, and long-term operating costs.

General applications: Standard combination of 2BV series water ring pump + ZJY series Roots pump, featuring high efficiency, easy maintenance, and low cost.

Automatic production lines: PLC automatic control system can be upgraded for unit start/stop, vacuum monitoring, fault alarm, and reduced manual operation.

High environmental protection requirements: If organic solvents are used as working fluid, a closed circulation system shall be established for solvent recovery and reduced environmental pollution.