Manual raking is only viable for small schemes, or sites which are manned for other reasons. There are now a range of automatic raking devices available to clean the screen and dispose of the trapped debris. The most common types are:

A robotic rake. These come in a variety of designs, but usually involve one or more rakes operated by a hydraulic ram.  Some designs require only a single rake which can index along the screen; otherwise two or more rakes can operate side by side.  These systems are usually very robust, partly because they can keep their drive mechanisms out of the water at all times.  Their main disadvantages are the visual presence of the equipment and the slightly greater health and safety risk posed by unattended operation of the equipment.

A rake-and-chain cleaner, in which a bar is moved up the screen by a chain drive at each end.  The bar deposits the collected debris in a channel running the length of the screen.  The channel can be flushed clean by a water supply (pumped if necessary), washing the debris towards a side spillway.

The grab-and-lift cleaner is a robust alternative to the robotic rake.  A single set of ‘jaws’ indexes along the screen and lifts the material straight into a skip.