How Liquid Ring Vacuum Pumps Work? A Complete Guide

Liquid ring vacuum pumps are widely used in industries where reliability, wet process handling, and continuous operation are critical. Unlike dry vacuum pumps, liquid ring pumps use a sealing liquid to create vacuum, making them ideal for harsh, humid, and vapor-laden industrial environments.

In this guide, we explain how liquid ring vacuum pumps work, their working principle, key components, industrial applications, and why many industries prefer liquid ring vacuum pumps over other types.

What Is a Liquid Ring Vacuum Pump?

A liquid ring vacuum pump is a positive displacement rotary vacuum pump that uses a liquid (usually water or oil) to form a rotating liquid ring inside the pump casing.

This liquid ring acts as:

• A seal — prevents gas leakage
• A coolant — absorbs heat during compression
• A compressing medium — compresses the gas

Because of this design, liquid ring vacuum pumps are highly suitable for:

• Wet gases
• Condensable vapors
• Dust-laden or corrosive processes

How Liquid Ring Vacuum Pumps Work (Step-by-Step)

Step 1: Formation of the Liquid Ring

When the pump starts, a sealing liquid (typically water) is introduced into the pump casing. The impeller is mounted eccentrically inside the casing.

As the impeller rotates:

• Centrifugal force pushes the liquid outward
• The liquid forms a rotating ring along the inner wall of the casing

This rotating liquid ring creates sealed chambers between the impeller blades.

Step 2: Gas Suction Phase

As the impeller rotates:

• The volume between impeller blades increases
• This increase in volume creates vacuum
• Gas is drawn into the pump through the inlet port

This makes liquid ring pumps ideal for continuous vacuum generation in industrial processes.

Step 3: Gas Compression Phase

As the impeller continues rotating:

• The liquid ring shape changes due to eccentric mounting
• The volume between blades reduces
• Gas trapped inside the chamber gets compressed

Step 4: Gas Discharge Phase

Once compressed:

• Gas is discharged through the outlet port
• The sealing liquid remains inside the pump and is recirculated

In many systems, the liquid is cooled and reused, making the pump suitable for continuous industrial operation.

Key Components of a Liquid Ring Vacuum Pump

• Impeller (rotor) — creates the rotating motion
• Pump casing — houses the liquid ring
• Sealing liquid — water or process fluid
• Inlet and discharge ports — for gas flow
• Shaft and bearings — supports rotation

These pumps have very few moving parts, which results in low maintenance, high reliability, and long service life.

Why Liquid Ring Vacuum Pumps Are Used in Industry

1. Excellent for Wet and Vapor-Heavy Applications

Liquid ring pumps handle moist gases, steam, and condensable vapors without damage.

2. Stable Vacuum Performance

They provide steady vacuum levels even in fluctuating process conditions.

3. Low Wear and Tear

No metal-to-metal contact inside the pumping chamber.

4. Safe for Explosive or Hazardous Gases

Often used in chemical and pharmaceutical plants.

Industrial Applications of Liquid Ring Vacuum Pumps

Common Industries

• Chemical processing plants
• Pharmaceutical manufacturing
• Sugar and food processing
• Paper and pulp industry
• Power plants
• Fertilizer and petrochemical plants

Typical Applications

• Vacuum distillation
• Evaporation and drying
• Filtration processes
• Deaeration systems
• Condenser evacuation

Liquid Ring Vacuum Pump vs Other Vacuum Pumps

Feature	Liquid Ring Pump	Dry Vacuum Pump
Handles moisture	Excellent	Limited
Handles vapors	Excellent	Moderate
Maintenance	Low	Medium
Operating temperature	Low	High
Harsh processes	High suitability	Medium

This is why liquid ring vacuum pumps are preferred for heavy-duty industrial processes.

Common Mistakes While Using Liquid Ring Vacuum Pumps

• Using incorrect sealing liquid
• Poor liquid temperature control
• Improper discharge piping
• No liquid recovery system

Proper system design ensures maximum efficiency and long pump life.

How to Select the Right Liquid Ring Vacuum Pump

Consider:

• Required vacuum level
• Gas composition
• Operating temperature
• Availability of sealing liquid
• Continuous or batch operation

Choosing the right pump ensures energy efficiency and reliable production.

Conclusion

Understanding how liquid ring vacuum pumps work helps industries choose the right vacuum solution for demanding applications. Their ability to handle wet gases, vapors, and harsh process conditions makes them a preferred choice across multiple industries.

At Upbringing, we help industries select and implement the right liquid ring vacuum pump solutions based on process requirements, ensuring reliability, efficiency, and long service life.