Understand the water removal principle of turbine oil vacuum purifier

A turbine oil dehydration purifier—commonly known as a vacuum oil purifier—is one of the most effective solutions for removing water from turbine oil. To understand how it works, it helps to look at the forms of water in oil and the physical principles behind the process.

Forms of Water in Turbine Oil

Turbine oil (steam turbine oil) can contain water in two main forms:

Free Water → Water that separates from oil, forming droplets or layers.

Dissolved Water → Water molecules that are uniformly dissolved in the oil, similar to sugar in water. This form is the hardest to remove.

The challenge is that dissolved and emulsified water cannot be removed by ordinary filtration. A vacuum oil purifier solves this by converting dissolved water into free water and then removing it efficiently.

Step 1: Heating and Pre-Separation

The first stage is heating the oil (typically to 50–65°C).

Why heating is important:

Reduces viscosity → Thinner oil flows more easily, aiding separation.

Raises water vapor pressure → Makes it easier for water molecules to escape from the oil.

Promotes demulsification → Breaks down emulsions, causing small water droplets to merge into larger ones.

At this stage, some free water may already have separated due to density differences.

Step 2: Vacuum Evaporation (Core Process)

The preheated oil enters a vacuum chamber, where it is sprayed into fine droplets under extremely low pressure (0.5–1.5 kPa absolute).

The physics principle:

At normal pressure (101.3 kPa), water boils at 100°C.

Under vacuum, the boiling point drops sharply:

70 kPa → 90°C

30 kPa → 70°C

1 kPa → just 7°C!

Since the oil is heated to 50–65°C, it is well above the boiling point of water under vacuum. This causes dissolved water to vaporize instantly without affecting the oil (whose boiling point exceeds 300°C).

Result: Deep dehydration and degassing in one step.

Step 3: Condensation and Water Discharge

The evaporated water vapor rises into the upper chamber and is processed as follows:

Condensation → The vapor passes through a condenser, cooling below its dew point, and turning back into liquid water.

Collection → The condensed water gathers in a tank or cup.

Discharge → Water is automatically or manually drained out.

Gas release → Residual air and non-condensable gases are expelled via the vacuum pump.

Meanwhile, the purified oil settles at the bottom of the chamber and is pumped back into the clean oil tank.

Comparison with Other Water Removal Technologies

Coalescing Purifiers → Combine water droplets into larger ones for separation. Good for free and emulsified water, but weak against dissolved water.

Centrifugal Purifiers → Use centrifugal force to separate oil and water. Effective for free water, but cannot remove dissolved water.

Vacuum Oil Purifiers → The only technology that reliably removes dissolved, emulsified, and free water, along with gases.

Conclusion

The water removal principle of a turbine oil vacuum purifier is a smart application of physics, not brute-force filtration. By combining heating, high vacuum, and condensation, these purifiers create the conditions for water to spontaneously boil out of turbine oil, leaving it dry, clean, and gas-free.

This makes vacuum oil purifiers the preferred solution for turbine oil dehydration, ensuring the safe and long-term operation of critical equipment such as steam turbine generator sets.