Usage: for determining the fibre length of pulp by classification.
Standardization: TAPPI and SCAN
Device Description : the Baure Mcnett fibre classifier consists of up to 5 narrow tanks 255mm deep , 127 mm wide
and 320mm high, mounted in a cascaded arrangement , with screens of 335cm2 mounted on the flat side . A
vertical , cylindrical agitator with short paddles rotates at 580rpm near one semi circular end of each tank . this
causes suspension to flow horizontally across the screen and circulate around the tank . an overflow weir is
provided at outgoing side of each screen , and a short pipe leads to the next tank with a finer screen at a slightly
lower level , or from the last tank to drain away . A flow regulator supplies water at the rate of 11.35 l/m to the
first tank. The motion of the water keeps the water from settling and presents them repeatedly to the screens
through which they will pass if the length is less than twice the screen opening. The primary unit has an inlet
funnel with an overflow and the nozzle for a constant water flow rate.Fractionating unit is completely self
contained having its own electric motor for the rotor and is made of non-corrosive material. Fibre collection box
with rapid locking device, support wire and suction connection.Interchangeable screens are available with wire of
4, 6, 8, 10, 14, 20, 30, 50, 100 and 200 standard mesh. The screen frames are clamped spring loaded self clamping
system. Classifier gives a very low spread in the results with a variation coefficient of less than 1%.
Test Description: With the screens correctly mounted in the tanks press the start button to start the water flow
into thje top tank . as soon as the lowest tank starts overflowing , press the stop button again and simultaneously
start to pour the prepared sample of 3,333ml with 24 grams of moisture free pulp during the period of 18second in
the top tank. Subsequently the flow at the rate of 11,355 l/m into the top tank, the stirrers and the timing of
20minutes are started automatically . A green light shows that the classification is in the process . during this time
the drainage cups are furnished with weighed and marked filter papers.
After the test (20 minutes acc to TAPPI and 15 minutes according to SCAN) the water flux is stopped automatically
and green light goes out . the stirrers continue running for another 2 minutes until there is no more water to drain
away from the lowest tank . now the drain plug and tap below the cup of the first tank is opened and the pump is
turned on to allow the contents to drain into the cup. After the tank has been drained the screen and the tank is
flushed carefully with the provided hose. When all the tanks are emptied in this way the pads are taken out of the
cups and folded in the middle. As much water as possible is removed using a wringer , a blotter or towel . before
weighing to within to 0.01 g the pads are dried in an oven at 100*c to constant weight