Contaminated lubricating and insulating oils are responsible for 70–80% of hydraulic system failures and transformer breakdowns. Water, dissolved gases, particulate matter and oxidation by-products degrade oil performance — reducing dielectric breakdown voltage in transformers, increasing wear in hydraulic and gear systems, and triggering premature bearing failure in turbines. Effective oil filtration and purification restores oil to as-new condition, extending equipment life by 5–10 years.
Transformer oil purification is critical for maintaining dielectric strength and preventing electrical breakdown. New transformer oil must be processed before energisation to remove dissolved moisture and air. In-service oil requires periodic treatment when the BDV (breakdown voltage) falls below 50 kV. Our mobile and fixed transformer oil purifiers remove water to below 5 ppm and dissolved gas content to below 0.1%, restoring BDV above 70 kV.
Turbine oil and hydraulic oil purification using vacuum dehydration units (VDU) removes free, emulsified and dissolved water plus dissolved gases that cause cavitation and accelerate oxidation. For hydraulic systems, achieving ISO cleanliness Class 14/12/09 or better dramatically reduces valve spool wear, actuator seal life and contamination-induced system downtime.
We supply portable skid-mounted, fixed-installation and mobile trailer-mounted oil filtration units for all industrial oil types. Our systems serve power utilities (66 kV to 765 kV transformers), steel plants, paper mills, cement plants, oil & gas facilities and power generation utilities.
The first stage removes large particles (>25μm) that would damage downstream fine filters and vacuum pumps. A bag filter or strainer basket with 25–50μm mesh rating captures metallic particles, rubber seal fragments and sludge agglomerates. A differential pressure gauge monitors filter loading, with automatic bypass protection when differential pressure exceeds the set value. Pre-filter housings are designed for quick cartridge change without draining the entire system.
Cold oil has high viscosity, which limits filtration flow rate and reduces the efficiency of coalescing and vacuum dehydration. An immersion heater or tubular heater raises oil temperature to 50–65°C — reducing viscosity for efficient water coalescence and gas release while remaining below oxidation and flash point thresholds. Temperature is PID-controlled with high-temperature cutout at 70°C for safety.
Fine water droplets dispersed in oil are coalesced into larger drops in a borosilicate glass fibre coalescing cartridge. Larger water drops then separate by gravity into a water sump below the filter housing, which is automatically drained by a float-type water drain valve. Coalescing efficiency above 95% for free and emulsified water. Oil-water interface level indicator alerts operator when water accumulation requires draining.
The heated, pre-filtered oil is sprayed through nozzles into an evacuated vacuum chamber maintained at 0.1–1.0 mbar absolute by a two-stage vacuum pump. At this low pressure, the boiling point of water drops below 10°C, causing dissolved and emulsified moisture to flash-evaporate rapidly from the oil surface. The evaporated water vapour is condensed in a refrigerated condenser and discharged. This stage achieves moisture content below 5 ppm in transformer oil and below 50 ppm in hydraulic oil.
Dissolved air and gas (oxygen, nitrogen, CO₂) is simultaneously removed in the vacuum chamber along with water vapour. Oxygen removal is particularly important for transformer oil — dissolved O₂ accelerates oxidation and acid formation. For transformer oil, dissolved gas content is reduced below 0.1% by volume, meeting IEC 60422 transformer oil maintenance standards. The vacuum system is sized for continuous operation at rated flow with positive vacuum reserve.
Oil exiting the vacuum stage passes through high-efficiency fine filters (3μm β₃ ≥ 200, then 1μm absolute) to achieve target particle cleanliness class. For hydraulic oil: ISO Class 14/12/09 (per ISO 4406:2021); for turbine oil: ISO Class 15/13/10; for transformer oil: IEC 60422 requirements. Magnetic separation removes ferrous particles (steel wear debris) with 100% efficiency regardless of particle size.
| Oil Types Handled | Transformer / Turbine / Hydraulic / Gear / Cutting |
| Flow Range | 100 LPH to 20,000 LPH |
| Moisture Achievement | <5 ppm (transformer) / <50 ppm (hydraulic) |
| Particle Class | ISO 4406 Class 14/12/09 |
| BDV After Treatment | >70 kV (transformer oil) |
| Dissolved Gas | <0.1% by volume (transformer) |
| Vacuum Level | 0.1–1.0 mbar absolute |
| Filtration Grades | 25μm → 10μm → 3μm → 1μm |
| Construction | Skid / Trailer / Fixed Installation |
| Standards | IEC 60422 / ISO 4406:2021 / IS 335 |
Tell us your oil type, volume, current condition and required cleanliness target — we will recommend the right purifier and provide a full cost justification analysis.
