Oil Treatment for Vehicle Wash Interceptors

Extract from the Pollution Prevention Guidelines: PPG3

Closure devices and alarms

Closure devices

If too much oil is allowed to accumulate inside a separator, it will not work effectively and oil will escape. To avoid this, full retention separators must be provided with an automatic closure device that will prevent flow passing through the separator when the quantity of oil in the separator exceeds the oil storage volume (V).

Also, during emptying or maintenance the separator should be isolated to prevent the escape of waste oil. Open all isolation valves when the operation is complete.

Do not fit automatic closure devices to bypass separators unless they have been designed specifically to operate on such separators.

If the automatic closure device is activated the operator should be alerted by a high level alarm so that immediate maintenance can be carried out.

Automatic Warning Devices/Alarm systems

Separators must be provided with a robust device to provide visual and audible warning (if necessary to a remotely located supervisory point) when the level of oil reaches 90 per cent of the oil storage volume (V) under static liquid level conditions. This automatic warning device indicates that the separator is in need of immediate emptying for it to continue to work effectively.

Also, as the build up of silt will prevent the separator from working effectively, we recommend that you install a silt level alarm or another suitable device in your separator to alert you to the build-up of excessive levels of silt. In many cases, oil and silt alarms can be fitted to an existing separator. Silt alarms are most useful on those sites where high volumes of silt are likely to enter the separator, such as quarries, builder's yards and major trunk roads.

Further equipment can be fitted to the separator, alongside a closure device and warning device, to alert the site operator to the routine maintenance requirements of the separator. This equipment might, for example, indicate when the next inspection is due and such 'separator management systems' will ensure that the separator continues to receive the appropriate level of attention.

Any electrical device used within a separator or used to monitor sensors placed within a separator must be intrinsically safe and certified to a suitable explosion protection standard. The location of the monitoring device, such as the alarm or 'separator management system' control panel, must be located within a safe area and conform to the requirements of BS EN 60079-10. For this reason it is important to always use qualified technicians who are familiar with the installation, calibration and servicing of intrinsically safe equipment. Regular maintenance and testing of equipment is essential.