What design for a filter strainer with automatic backwash cleaning?

Our client is a global leader in plant-based ingredients and a pioneer in new plant proteins. The group addresses societal challenges by unlocking the potential of nature to provide the best ingredients for the biopharma, pharmaceutical & nutraceutical, cosmetics, food, nutrition, and industrial markets. This global group, present in over 100 countries, employs 8,600 people across 25 manufacturing sites.

A 316L stainless-steel strainer filters water containing sand and various starches.

Observations:

This strainer, with a 500 µm filtration rating, was unsatisfactory, as it did not retain enough sand and small stones present in the water. Moreover, the presence of starch rapidly clogged the strainer, requiring 4 to 5 cleaning interventions per day.

Desired improvements:

• Provide a reinforced strainer capable of withstanding a backwash system installed by the client, to remove contaminants under a counterflow rate of 25 m³/h at 5 bar.
• Ensure filtration of particles larger than 500 µm while maintaining a flow rate of 60 m³/h at 5 bar, to prevent pump cavitation downstream of the filter.

The proposed solution has two key aspects:

• Strict adherence to the geometry and dimensions of the strainer to ensure easy installation when replacing the filter in an existing filter housing.
• A design and filtration rating perfectly aligned with the process and the client’s requirements.

Geometry & Dimensions

Design & Filtration Rating

Inserted into a horizontal filter housing at the client’s site, the strainer measures 275 mm outer diameter and 263 mm inner diameter.

Each end features a 340 mm flange with a 29 mm groove to accommodate an O-ring, enhancing the seal of the strainer—a specific client requirement.

The reinforced filter design allows:

• Filtration from outside to inside at a flow rate of 60 m³/h under a maximum pressure of 5 bar
• Automatic backwash with water at 25 m³/h and a pressure of 5 bar

Design & Filtration Rating

The strainer design consists of a wire with a trapezoidal/triangular cross-section wound around cylindrical supports. Its main advantages include:

• High mechanical rigidity, essential for backwashing
• Pressure resistance superior to more traditional technologies—in this case, 5 bar
• Extended service life, minimizing maintenance interventions for the client

We proposed three filtration ratings: 500, 400, and 350 µm. The client opted for our 350 µm strainer following the installation of an automatic backwash system. The open area of the strainer is 19.8%.

In conclusion, the filtered fluid is sufficiently purified and meets our client’s quality expectations. Productivity gains are significant, as the client no longer needs to perform 4 to 5 daily interventions on the installation.

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