Gravity Strainer model BSW is available in six sizes.

Capacity range:

25 to 700 m3/h

Filter fineness:

0.08 to 0.25 mm (80 to 250 micron)

Connection dimensions:

DN100 to DN400

Filter motor:

0.25 – 0.37 kW, depending on filter size


Stainless steel EN1.4301 or EN1.4404 and EN1.4436.

The Gravity Strainer Filter BSW is available in six sizes, and are self cleaning systems that work under atmospheric conditions, removing suspended solids from relatively high flow water streams up to 11000 l/min. They are most commonly used in the pulp and paper industries to reduce the fibre concentration and to remove felt hairs and fibre bundles. Also to separate long fibres and process debris from recycled plant waters.

Gravity Strainer BSW used on white water in papermaking are mostly used on water streams with 20 up to about 600 mg/l (ppm) fibres. Smaller units are used for up to about 1000 ppm.

Typical applications are the mill’s spray water supply, purification of sealing water from vacuum pumps, polishing of water from flocculation plants and cooling towers. The filter is also used for purification of intake water from lakes and rivers.

How they work

The water is fed in tangentially between the outer and inner jackets of the filter vessel. The water flows up and over the edge of the internal vessel and down onto the strainer media. Unwanted solids/fibres are captured upon the strainer media, and clean water passes through the fine filter mesh, exiting at the bottom of the strainer vessel. Cleaning is achieved by spray cleaning the strainer media in a novel way, “bottom-up cleaning”. Two spray bars positioned below the strainer media, rotates in-line with the unique collection chambers located directly above the strainer media. These collection chambers catch the fibres/solids lifted by spray water from the screen surface, and feed them down towards the drain. Fibres are transported inside the collection chambers, not on the top of the strainer media.

The “bottom-up” advantage

Our Gravity Strainer BSW represent a superior alternative to previous designs prevailing in the market. The bottom-up cleaning technique used, is a major improvement over other designs that rely on “top-down” sprays to drive solids/fibres along the strainer media to a collection point. This top-down technique is less effective and less efficient in retaining fibres/solids, because the sprays can drive solids into or through the strainer media. The bottom-up spray continously forces fibres/solids off the strainer media and lifts them into the reject pipe. This makes the BSW Gravity Strainer more effective and efficient in retaining fibres/solids, and provides an improved final filtrate.