How Industrial Vacuum Oil Purifiers Remove Water and Gas from Oil

Industrial vacuum oil dehydrators, also known as vacuum oil purifiers, are designed to deeply remove water (free, emulsified, and dissolved) and gases (air and volatile gases) from various industrial oils.

Compared to centrifugal oil purifiers, which primarily separate solid particles and large amounts of free water, vacuum systems offer more thorough dehydration and degassing, thereby restoring oil to a clean and stable state.

1. Working Principle: Heat, Then Vacuum

The core concept is simple — heat first, then dehydrate under vacuum.

When oil is heated and exposed to low pressure, the boiling point of water drops, allowing it to evaporate naturally at much lower temperatures.

2. Three Core Operating Stages

(1) Heating

Purpose:

Not to boil water directly, but to activate water molecules for easier evaporation under vacuum. Heating also lowers the viscosity of the oil, helping moisture separate from the oil film.

Method:

Electric or indirect heat transfer systems are used to avoid local overheating and oil oxidation.

(2) Vacuum Flash Evaporation

This is the heart of the vacuum oil purifier.

Principle:

Water’s boiling point decreases with pressure.

At –0.085 MPa (85% vacuum) → water boils around 60°C

At –0.095 MPa (95% vacuum) → water boils below 40°C

Process:

Preheated oil is sprayed into a vacuum separation chamber.

In this low-pressure environment, emulsified and dissolved water instantly flash-evaporates, turning into vapor that separates from the oil.

(3) Separation and Discharge

Gas–Water Separation: The vacuum pump draws out vaporized water and gases.

Condensation Recovery: Water vapor passes through a condenser, cools into liquid water, and is collected in a discharge tank.

Gas Exhaust: Non-condensable gases (mainly air) are vented safely.

Oil Output: The purified, dry oil is discharged from the bottom and returned to the system or storage tank.

3. Key Advantages

Complete Dehydration: Removes free, emulsified, and dissolved water — far beyond centrifugal purification capability.

Efficient Degassing: Eliminates dissolved air and gases, reducing oxidation and cavitation.

Protects Oil Quality: Uses physical, low-temperature dehydration, avoiding oil cracking and additive loss.

Fully Automated: Modern systems include automatic control for oil level, temperature, and vacuum pressure, enabling continuous operation.

4. Typical Applications

Vacuum oil purifiers are widely used in industries that require deep dehydration and gas removal, including:

Power Industry: Transformer and insulating oil purification (most common).

Hydraulic Systems: Removes moisture and air to prevent corrosion and valve cavitation.

Turbine Oil Systems: Maintains lubrication and control accuracy in power plant turbines.

Machinery and Bearings: Extends the lifespan of lubricating and gearbox oils.

Summary

An industrial vacuum oil dehydrator works like a low-pressure evaporator:

By heating the oil and creating a vacuum, water evaporates at low temperature. The vapor is extracted, condensed, and discharged — leaving behind clean, dry, and stable oil ready for reuse.