The Auto-Shok and Auto-Pulse Filters are classical tubular filters, also known as Candle Filters
When the service cycle reaches its end, cleaning can be performed using compressed air for backpulsing. After a number of cycles that last a few seconds, the solids are purged from the lower cone by flushing.
Depending on the properties of the membrane and the nature of the solids settled in the lower head, AutoPulse can also be “bumped” instead of backflushed as the flow through the tubes is momentarily reversed, dislodging the cake from the non-stick surface of the filter element. After the solids settle into the cone-shaped bottom of the extended filter shell, the influent is pumped into the filter just above the solids layer.
Because cleaning time is minimal, the filter is extremely flexible. Some applications will require only a small flow-equalization tank upstream to enable a single filter to handle a continuous stream. On larger filters, the top dome can be segmented to allow for cleaning in sections. This provides the key benefit of continuous filtration from a single filter.
The start of the cleaning sequence is triggered as the pressure drop across the tube elements reaches a predetermined setpoint during filtration. Next, the service cycle is stopped and the inlet and outlet are closed. The filter is then pressurized from an external pressure source (e.g. feed pump) and compressed air is applied to the top dome. Once an internal pressure of 60 psi has been reached, the drain valve is quickly opened to allow the filtered liquid to backwash the tubes.