Filtration bag

A filtration bag for a flowing fluid, comprising:

• an outer fabric sleeve (29) having a first end edge, and a second undulating end edge (41);
• said undulating edge having areas thereof pressed together and secured by stitches, to close the fabric sleeve at said second end edge;
• a wire annulus (23) located at said first end edge of the fabric sleeve;
• said fabric sleeve being looped around said wire annulus at said first end edge to form a reinforced mounting ring structure for the bag;
• said ring structure being adapted for positionment in a rigid flow duct so that fluid flowing through the duct is subjected to a filtration action by the bag;
• said outer fabric sleeve having a circular cross-section concentric around a central fluid flow axis (15);
• an inner fabric liner (35) located within said sleeve;
• separate stitch means (47) extending through said fabric liner and said sleeve to directly connect the liner to the sleeve at circumferentially spaced points around the sleeve;
• each said stitch means extending parallel to said central axis;
• sections of said liner between said separate stitch means being looped away from the fabric sleeve toward the sleeve central axis to form plural hollow pockets (39);
• the walls of each pocket being convergent in a direction going toward the central axis, to form apex areas (50) spaced from the fabric sleeve;
• said pockets being circumferentially spaced to form crevices (55) between the pockets;
• and
• a filler material (38, 57) filling each pocket so that the pockets are prevented from collapsing due to fluid flow forces.