How do you size an oil and water separator for each site?

The two main design criteria when considering the size of an oil and water separator for your site are flow rate and spill containment. The size of your oil and water separator will depend on the type of site you have, and which of these factors is the most important.

For example, at an airport, refuelling occurs anywhere on the apron – which is quite a large area. Subsequently, this large catchment will have a high volume of runoff in a rain event. In sites with these large catchment areas, the flow rate is often the defining factor for choosing a full retention separator – and the devices will be sized to suit higher flow rates, with spill containment being a secondary priority.

Alternatively, at sites such as transformer yards, oil and water separators may be employed to contain large volumes of oil in the event of a fire or a large spill. In these cases, the full retention separator will need to accommodate the desired on-site spill capacity. This will be the defining factor for choosing the right size device, and the spill capacity of the device is designed to match the potential for a spill scenario – and flow rate would be a secondary constraint.

By weighing your on-site priorities and defining key parameters, you can adequately size a device to suit your site. Other considerations include local device standards, environmental compliance policies and any legal obligations for the site operator.

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