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ESI Group - Transformer Oil Reclamation

ESI Group is a provider to the electrical supply industry and industry customers in Australia, New Zealand, the Pacific and South East Asia. The company has more than 20 years’ field experience in the design and operation of high-voltage transformer oil reclamation equipment.


Paper mechanical strength, dielectric strength and dielectric spacing keep your transformer going. Oil protects the paper, but oil oxidises create oxidation by-products which destroy the paper. To maximise the life of the paper insulation, oxidation of the oil must be controlled.


ESI provides the following services throughout Australia, New Zealand and South East Asia:

  • Transformer oil reclamation including desludging, on or off-line
  • Transformer oil vacuum drying
  • Oil sampling and testing
  • Dechlorination of PCB contaminated oil and solid waste
  • Supply of transformer oil filtration equipment
  • Manufacture of tap changer filter units under ESI TOMS brand
  • Supply, installation and hire of passive filtration and dry-out systems for main transformer tanks, supply of new or regenerated oil


On-line vacuum dry-out units allow drying of transformer windings while the transformer remains in normal service. Maintaining low moisture levels in the cellulose ensures the transformer is less likely to fail due to shock loadings, such as lightning or through faults, and insulation material is not degraded through chemical reaction with moisture.


ESI tap-changer filter units remove moisture and particulates in the insulating oil, maintaining electrical properties and reducing arcing during contact break. Cost savings in maintenance, spares and a significant increase in system reliability soon recover initial installation costs. Stainless-steel construction, pipe and fittings ensure maximum filter life.


The ESI vacuum dryer / degasser units are designed as versatile transformer oil filter units for field or factory use. These units use high-capacity multi-stage electric oil heaters, large-capacity vacuum pumps with external connections and three-stage particulate filtration. Flow rates up to 6,000L/hr are available.


These filter units are simple to use and plug into a standard domestic power supply yet will remove free, emulsified and dissolved moisture in oil from 50ppm to <10ppm in a single pass. Particles are also removed to < 0.4µm ensuring the electrical properties of insulating oil always meet specifications. An in-line moisture meter comes standard with the filter unit so maintenance crews can re-energise field equipment with confidence.

Versions of this unit are also available for lubrication and hydraulic oils.


On-line transformer oil regeneration not only restores the oil to new oil condition, it also removes sludge and other contaminants from the transformer windings and cooling system, lowering operating temperatures and preventing re-contamination of the oil. Maintaining the chemical properties of insulating oil through regeneration ensures maximum transformer life and reliability.


ESI is committed to protecting community health and the environment. The fulfilment of this commitment is considered an essential requirement for the long-term success of the company. ESI strives to conduct its business as a responsible steward of the environment, as well as safeguarding the health and well being of our employees, neighbours and customers.

Contact Details

Energy Electric Ltd t/a ESI Group (NZ) Pty Ltd
New Zealand
Contact: Bill Kilgour (New Zealand enquiries)
Tel: +64 6 7648176
Fax: +64 6 7648167

With ESI on-line vacuum dry-out units, drying of transformer windings can take place while the transformer remains in normal service.
ESI tap-changer filter units remove moisture and particulates in insulating oil, which helps maintain electrical properties.
Vacuum dryer / degasser units for field or factory use and versatile transformer oil filter units.
ESI portable filter units are simple to use and plug into a standard domestic power supply.
On-line transformer oil regeneration restores the oil to new oil condition and removes sludge and other contaminants.
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