How to Lower Acid Value in Transformer Oil: Why Regeneration Is Required

Why Ordinary Oil Purifiers Cannot Reduce Acid Value — And How Regenerative Oil Purifiers Solve the Problem

Transformer oil naturally oxidizes during operation, forming acidic byproducts that increase its acid value (neutralization value). Many users wonder whether an ordinary vacuum oil purifier can reduce acid value.

The answer is no.

To truly lower acid value, a regenerative oil purifier with adsorbent technology must be used.

Below is a clear explanation of why acid value increases, how purification works, and which equipment is required.

1. Why Ordinary Oil Purifiers Cannot Lower Acid Value

Source of Acid Value in Transformer Oil

During long-term operation, transformer oil reacts with oxygen and heat, forming:

Organic acids (such as carboxylic acids)

Oxidation byproducts

Polar compounds

These acidic components dissolve directly into the oil.

How an Ordinary Vacuum Oil Purifier Works

A standard vacuum oil purifier improves oil quality through two main methods:

1. Vacuum Dehydration & Degassing

Removes:

Free and dissolved water

Free and dissolved gases (oxygen, nitrogen, etc.)

2. Mechanical Filtration

Removes solid contaminants, including:

Metal particles

Carbon residue

Dust and fibers

But here is the core limitation:

Mechanical filtration cannot remove dissolved organic acids

Acidic molecules are dissolved at the molecular level.

Filtering them is like trying to filter dissolved salt out of soup—impossible with a physical filter.

Result

An ordinary vacuum oil purifier can significantly improve:

Breakdown voltage

Moisture level

Cleanliness

But it has almost zero impact on:

Acid value

Dielectric loss

Chemical aging indicators

How a Regenerative Oil Purifier Effectively Reduces Acid Value

To reduce acid value, oil treatment equipment must include a regeneration system using special adsorbent materials.

Core Technology: Adsorbent Purification (Regeneration)

A regenerative oil purifier contains a regeneration tank filled with materials such as:

Activated clay

Activated alumina

Silica gel

Special composite adsorbents

When hot transformer oil passes through the regeneration tank:

The adsorbent’s microporous structure captures acidic molecules

Polar oxidation products are removed

Colloids and dissolved aging substances are adsorbed

Effect: Acid Value Is Directly Reduced

This process physically and chemically removes the dissolved acidic substances, lowering:

Acid value

Dielectric loss factor

Oxidation byproducts

Oil color (becomes lighter)

Complete Workflow of a Regenerative Oil Purifier

A full regeneration system usually includes:

Mechanical filtration → removes solid particles

Vacuum dehydration & degassing → removes water and gases

Adsorption regeneration → removes acids and aging byproducts

This allows the oil’s chemical and electrical properties to be restored.