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9
20. At the end of the test, close (tighten) the top and bottom valve stems. This
will seal the cell.
Failure to close the valve stems before releasing pressure (step 22)
will damage a regulator by drawing fluid into it.
21. Turn off the heat switch and set the temperature controller to the lowest
setting.
22. Open the outlet valve on the back pressure receiver to collect all of the
filtrate in the graduated cylinder. Open the relief valve on the manifold
block. This will flush the pressure lines and ensure no test fluid has flowed
back into them.
23.
Slowly turn the regulators counterclockwise to close off the flow of
pressurized gas.
24. Remove the top and bottom retaining pins and remove the manifold block
and the back pressure receiver. Drain any residual filtrate collected in the
receiver into the graduated cylinder.
25. Remove the cell from the heating jacket after once again checking that
the cell valve stems are tightly closed. Allow it to cool to room temperature
or quick cool the cell by immersion in cool water.
Pressure inside the sample cell will still be approximately 500 PSI
(3,450 kPa). Keep the cell upright and cool it to room temperature
before disassembling. The cell must be cool for at least one hour
at room temperature or at least 10 minutes in cool water before
loosening the cap locking screws and removing the cell cap.
26.
Correct the total filtrate volume collected to a standard filtration test
area of 7.1 in
2
(45.8 cm
2
) by doubling the filtrate volume collected in
30 minutes. Record this total filtrate volume (doubled), temperature,
pressure, and time.
27.
Using extreme care to save the filter paper and deposited cake, place
the cooled cell upright with the outlet (cap side) or filter side down. Open
(loosen) the inlet valve stem to bleed off pressure from the cell body.
Pressure cannot be relieved from the cell by opening the outlet valve
stem as the filter cake will seal off the cell. It is a good idea to open
the valve stem with the cell inside a sink or with a rag over the valve
stem in order to catch any liquid that might be ejected.
28. Loosen, but do not remove, the six cap locking screws, and separate the
cap from the cell with a slight rocking motion. Discard the fluid inside the
cell and retrieve the filter cake.
