For food processors, automatic scraper strainers are among the closest solutions to a true “set-and-forget” system, effectively removing both large and fine suspended solids from process water, cooling tower water, wash water, liquids, and slurries.
The basic design represents one of the most efficient and cost-effective industrial self-cleaning strainers available. The motorized unit is engineered for minimal maintenance and operator involvement and can remove solids as small as 75 microns. These strainers allow for continuous, uninterrupted flow, including during blowdown cycles.
Cleaning is performed by a spring-loaded blade and brush system controlled by a fully automatic control unit. The two blades and two brushes rotate at 8 RPM, for a total of 32 passes per minute. The scraper brushes penetrate the wedge-wire slots to dislodge stubborn particulates and adhered solids.
This design enables the scraper strainers to resist clogging and fouling even in food processing applications with large debris and high solids concentrations. It also ensures a complete cleaning and is very effective against organic matter biofouling.
However, incorporating minor customizations or application-specific modifications can further optimize the automatic scraper strainer’s performance and suitability for a given food processing application, according to Robert Presser, President of Acme Engineering Products, Inc., a North American manufacturer of industrial self-cleaning strainers.
Choose the Screen Best Suited to the Application
Scraper strainers are available in various screen constructions, each engineered to address different process requirements and operating conditions.
Screen selection for food processors usually begins with consideration of the solid profile generated by the product being processed as well as the solids content within the cleaning water and wastewater streams. Solid profiles vary significantly depending upon the product being processed. Dairy, fruit and vegetable, meat and poultry, beverage, and ingredient operations can each generate different combinations of fine suspended solids, sticky organics, fibrous debris, fats, oils, and grease.
Reverse formed wedge wire screens are the most common screen type used due to their strength, durability and resistance to deformation resulting from high differential pressures. The smooth continuous slot profile minimizes particle wedging and facilitates the use of automated brush cleaning systems.
Affordable Solutions for More Effective Solids Removal Scraper strainers allow the solids to accumulate at the bottom of the vessel, where the blowdown valve will open periodically to clear them out. Liquid loss is minimal, accounting for less than one percent of the total system flow.
If additional pressure is required to clean the screen, however, an inexpensive trash pump can be added to the blowdown line to assist in removing the solids, debris, and sediment that collect in the strainer sump.
Add a Macerator to Break Up Large Solids
For applications with high solids loading that are prone to clogging, including many food processing wastewater and byproduct streams, a macerator can be installed upstream of the automated scraper strainer. This solution accommodates heavy solids loading while ensuring uninterrupted flow and dependable, clog-free performance.
Specify Fiber-Reinforced Plastic (FRP) Construction
When the chemical properties and temperature of the process fluid raise concerns about material compatibility, automated scraper strainers are available in other materials such as Monel, D2205, SD2507, and even Fiber-Reinforced Plastic (FRP). The internal mechanism and wetted components can be manufactured from super duplex or similar high-performance steels.
Although standard carbon steel construction is adequate for typical use, corrosive environments such as those involving seawater, erosive slurries, or aggressive chemicals can quickly corrode conventional equipment. This can lead to potential issues in safety, quality, and compliance as well as production downtime, requiring premature strainer component replacement.
For these reasons, duplex or super duplex stainless-steel construction is used to resist corrosion, but at considerable cost. However, a much more cost-effective option is to utilize Fiber-Reinforced Plastic (FRP) strainers that are specifically designed to be resistant to corrosive environments at a fraction of the cost.
For food processors, automatic scraper strainers can offer a far more stable answer to solids separation in applications where conventional screens struggle with heavy loading, changing flow conditions, or persistent fouling. Continuous self-cleaning reduces the need for manual intervention, helping plants avoid unnecessary downtime and maintenance.
For more info, visit Acme Engineering Prod. Inc. at acmeprod.com; phone Philippe Ellison, Project Manager at: +1-518-236-5659; email phil@acmeprod.com. In Canada phone: +1-514-342-5656.