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The Best Way to Dewater New Transformer Bunds

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There are a variety of systems for dewatering transformer bunds. Some scenarios call for sophisticated monitoring and pumping systems but these increase the complexity and cost of bund construction and introduce multiple points of failure. For lower-risk sites, this may be overkill.

In this article we look at a low-cost, low-maintenance and scalable solution which offers an alternative to oil-discriminating pumps, oil water separators and vacuum tankering.

Green Rhino’s Oil Removal Cartridges & Filters attach to a simple drainage outflow built into the transformer bund. Oil is removed from the bund water as it passes through the cartridge, allowing clean water (less than 5ppm oil) to be discharged to surface drains or the environment.

Popular with transformer manufacturers and maintenance contractors, these cartridges are simple and highly effective.

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Here are five reasons why Green Rhino’s Oil Removal Cartridges and Filters could be the best solution for your transformer bund installations.

Reduced construction costs

Installing oil discriminating pumps and underground oil water separators can add a week to bund construction. Additional costs include specialist equipment, an electrician to wire, test and certify equipment, and oversight by a senior authorized person (SAP). Retrofits may require the transformer to be switched off and the load transferred. With more third-party operatives on site, your health and safety risks are also higher.

Green Rhino’s Oil Removal Cartridges simply require a drainage outflow to be built into the bund.

High performance

Water enters the cartridge from the bund outflow and passes first through a sediment filter then a hydrocarbon filter. Clean water is discharged from the cartridge into the environment.

Filters are available with a range of capacities from 1‒14 litres of oil and flow rates from 6‒80 litres of water per minute. On low-risk sites, cartridges may last years before needing to be replaced.

The active component in these cartridges is a proprietary smart polymer which reacts with the transformer oil to form a solid and insoluble rubber-like substance. Trapped inside the cartridge, the solidified oil physically can’t leak out. (Watch how our smart polymer solidifies oil here.)

When all the polymer in the filter has been activated by oil, flow is naturally blocked so no leakage can occur. This means that the cartridges deliver a failsafe response in the event of a catastrophic breach.

Low maintenance

The cartridges have no mechanical parts or power requirement which reduces the potential points of failure. This is ideal for remote and infrequently-visited locations.

Your regular maintenance engineers simply to need to check the cartridges when on site. An accumulation of water in the bund indicates either that the sediment filter needs cleaning out or that the cartridge needs replacing.

A fitting kit enables the cartridge to be removed, inspected and replaced without any leakage occurring. The sediment filter can be easily removed and cleaned out during inspections.

The smart polymer inside the cartridges poses no health and safety issues to maintenance operatives and units can be disposed of in standard hazardous waste bins.


As a transformer ages and the rate of leakage increases, lower-capacity cartridges can be replaced with higher-capacity units, or additional filters can be added to a bund.

Similarly, filters can be retrofitted to bunds to replace or provide support for pumping systems that are struggling to perform.

Low cost

Cartridges cost from just £240 to £2,300 depending on the specification. Factor in the savings on construction, installation, maintenance and waste oil/water removal, and Green Rhino’s Oil Removal Cartridges offer a very cost-efficient solution.


Oil Removal Cartridges aren’t suitable for every situation. Old transformers leaking litres of oil each day would quickly overwhelm a cartridge and instead require substantial preventative measures.

For new and smaller transformers, however, Oil Removal Cartridges offer considerable advantages.

If you would like to learn more, please call us on 01206 299388 or book an onsite demo.

Oil Removal Cartridges ¦ Oil Removal Filters

Filters can also be provided in single and multi-filter chambers, to manage the outflow from a series of bunds or a site. (Ask too about our creosote filters for utility pole and sleeper depots.)

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