Transformer Oil Purification

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SC Industrial Sales has over 25 years experience implementing transformer oil purification, filtration, vacuum dehydration, vacuum degassing and regeneration.  We offer personalized assistance when it comes to selecting the proper piece of equipment for your requirements.  

Examples of Transformer Oil Purification equipment we offer:


High Vacuum Oil Purifiers

The increasing voltage and rating of the modern transformer and electrical apparatus result in greater electrical stress in insulating material and fluids. To handle these greater stresses, transformer oils with better dielectric quality are required, and lower residual water content in insulation must be maintained. 

The proper treatment and upgrading of the insulating fluid / transformer oil will result in the improvement of the properties of the entire insulating media of power transformers. 

The principal functions of the insulating liquid are to serve as a dielectric material and an effective coolant. To perform these functions, the insulating liquid must have the necessary qualities at the time of initial impregnation and filling at the factory and later maintain the same quality in the field operation. 

The Pro-Filtration High Vacuum Process upgrades the new or used electrical insulating liquids and transformer oil. 

A High Vacuum Process is used for dehydrating and degasification of electrical insulating fluids (transformer oil) to increase and maintain their dielectric strength. The processing includes the removal of free and soluble water, free and dissolved air and gases, and particulate matter. 

  • Removes Gases
  • Removes Free, Emulsified & Dissolved Moisture
  • Removes Particulate / Carbon Fines <0.5 µm nominal and ß2.5[c]=1000
  • Restores Dielectric Strength
  • Stationary, Portable or Mobile
  • Flow Range from 5 – 65 GPM

High Vacuum Oil Purifier

High Vacuum Oil Purifiers feature:

  • Vacuum Pump & Booster Package
  • Digital Absolute Vacuum Gauge
  • Moisture Monitors
  • Heater Packages
  • Absolute Filtration

High Vacuum Package

Mobile Options

Check out our latest Mobile Transformer Oil Purifier

Transformer Oil Purifier





We offer several mobile options.  All trailers are built in house with quality, safety and longevity being our top priorities.

Our small single axle trailers are ideal for degassing, dehydrating and filtering of oil when the transformers are in tight spaces.

Small High Vac Trailer

Cargo trailers are ideal for tight areas but more internal space is required for oil storage tanks, hose reels, hose storage, work benches or an extra vacuum package.

Oil Processor Cargo Trailer

53′ custom trailers are ideal for large processors with generators, dry air systems, office space, work benches, tools and storage are needed.

High Vacuum Oil Purifier Trailer

Low Vacuum Oil Purifiers

Low vacuum transformer oil purifiers are a simpler version of the high vacuum system.  These are used mostly for dehydration and light degassing.  These are an economical choice when moisture removal and filtration is required without the need for gas removal.

Flow rates range from 3 GPM up to 50 GPM.

POP3 Vacuum Dehydrator

Transformer Oil Regeneration Systems

Transformer oil regeneration systems transformer oil to like new condition. Oil flows through large volume media vessels at a very slow rate and removes acids, sludge and products of oxidation.  The system includes a regeneration cycle to restore media to new condition; media can be restored 200-300 times before it needs to be replaced.  These systems are typically used in conjunction with a degassing and filtration system. And, are designed to fit in a 20’ or 40’ cargo container for ease of transport.

Fullers Earth Regen SchematicTransformer Oil Before After FE Regen

Typical Transformer Oil Results Before and After Regeneration

Condition Test Methods Before regeneration After regeneration
Appearance Visual Cloudy brown Clear and transparent
Acid number, mg КОН/g IEC 296; ASTM D-664 0.63 0.01
Corrosive sulfur ISO 5662; ASTM D-1275 Present None
Moisture content, ppm IEC 733; ASTM D-1533 170 5
Breakdown voltage, kV IEC 156; ASTM D-1816 11 73
Dielectric loss tangent at 90ºС IEC 247; ASTM D-924 4.0 0.001
Surface tension, mН/m, at 25ºС ISO 6295; ASTM D-2285 22 45
Mechanical contaminants size, micron   50 5
Oxidation stability: mg КОН/g IEC 1125А; IEC 1125B; IP-307 0.2

Fullers Earth Systems

Used to correct total acid number (TAN) and correct color, much like the fullers earth regeneration systems.  Unlike the fullers earth regen systems, the media is discarded after each use.  We manufacture cartridge vessel systems or bulk style tower systems.  Cartridge vessel systems are a nice add on to small flow applications.

fullers earth cartridge vessel skid

Cold Traps

During the restoration of a transformer, it is extremely important to remove as much moisture as possible from its internal components. This is accomplished by isolating the empty transformer so that it can be placed under vacuum. 

Under these “blank off“ conditions, vacuum is pulled down to 0.25-1 torr for an extended period of time. Water will be vaporized and pulled toward the vacuum pumps; with moisture temperatures above 60-70°F. The longer the transformer is left under this condition, the dryer it gets. 

The cold trap is used to help the operator in determining that point and which the transformer has reached sufficient dryness. The operator can end the process with confidence as the process can be recorded from time to time by freezing, metering and comparing the amounts of moisture trapped in the cold trap.

Cold Trap Cold Trap Collection Vessel 

Transformer Oil Dryout Systems

Transformer oil Dryout systems utilize water absorptive media to remove moisture from transformer oil.  These are ideal for applications where vacuum cannot be used and/or just moisture and particulate removal is required.

Benefits Include:

  • Removes free and emulsified water
  • Removes Carbon
  • Can be used online
  • Stationary, portable and mobile options
  • Customizable with oil storage tanks, valve manifolds, moisture monitors, etc.

Dryout Trailer InsideTransformer Oil Dryout SkidTransformer Oil Dryout Skid with TankTransformer Oil Dryout Trailer

Vacuum Pump Packages

Stand alone vacuum packages, skid mounted for easy transport to site. 

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