Mechanical Scraper vs. Backwash: Choosing the Right Self-Cleaning Method

Automatic self-cleaning filters are generally divided into two mechanical types: backwash systems and scraper-type systems. Backwash filters use a portion of the clean fluid to flush the screen from the outside-in, effectively stripping the "filter cake" and discharging it through a sewage valve. This method is highly effective for removing low-density solids and organic matter from cooling water and river water. It relies on the system's pressure to provide the force needed for cleaning, making it an elegant and energy-efficient solution for most high-flow water applications.

Scraper-type filters, however, are designed for more "difficult" fluids, such as those that are viscous, sticky, or laden with heavy mechanical solids. In this design, a motorized scraper blade (made of plastic or metal) physically wipes the internal surface of the filter screen. This mechanical action is essential for removing substances like grease, thick oils, or adhesive residues that would simply stick to a screen during a standard backwash. The scraped debris is pushed into a collection chamber at the bottom of the housing, where it is periodically discharged.

The choice between these two methods depends on the nature of the contaminant and the viscosity of the fluid. Backwash filters are the standard for water treatment and thin liquids, while scraper filters are the go-to for the petrochemical and food processing industries (e.g., filtering chocolate or resins). Both systems share the same ultimate benefit: they operate continuously without the need for human intervention or consumable filter elements. By selecting the correct cleaning mechanism, industrial facilities can eliminate the ongoing costs of filter replacement while maintaining a perfectly clean process stream 24 hours a day.