Filtrate sampling device

A filtrate sampling device for collecting a filtrate sample from a pulp solution, the filtrate sampling device comprising:

• a jacket;
• a hollow piston rod (i) comprising a first end, a second end, and an opening, (ii) being arranged inside the jacket in a longitudinal direction of the jacket, and (iii) being arranged to reciprocate inside the jacket in the longitudinal direction of the jacket;
• and
• a hole screen arranged on the hollow piston rod, the hole screen comprising a number of holes, and the hole screen and the jacket having a clearance defined therebetween, wherein
• an end edge of the jacket is arranged to contact the hole screen as the hollow piston rod moves into the jacket, and
• the filtrate sampling device is equipped with backflush equipment comprising:
• an empty space defined between an inner wall of the jacket and the hollow piston rod, the opening of the hollow piston rod providing a path between an interior of the hollow piston rod and the empty space, such that the empty space is in fluid communication with the holes of the hole screen through the interior of the hollow piston rod and the opening, and
• a protrusion disposed around the hollow piston rod, the protrusion forming a piston that affects a volume of the empty space.