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25. Open (loosen) the top valve stem
½
turn to pressurize the sample. Main
-
tain this pressure on the fluid until the temperature has stabilized.
26. After the one hour heat up time, increase the pressure on the top pres
-
sure unit to 500 PSI (3,448 kPa) more than the back pressure.
27. Open (loosen) the bottom valve stem
½
turn to initiate filtration as soon as
possible.
Closely monitor the pressure gauges. If at any time during the test the
pressure inside the cell rises above the setpoint, carefully open the
needle valve on the top pressure assembly just enough to bleed off the
excess pressure. Then close the valve. If the cell pressure decreases due
to collection of filtrate, increase the pressure with the inlet regulator.
28. To collect filtrate, carefully open the ball valve on the bottom of the back
pressure receiver while holding a graduated cylinder up to the valve port.
Close the valve immediately after the pressure begins to decrease and
the filtrate is collected.
Collect filtrate at 10 seconds, 1 minute, 7.5 minutes, and 30 minutes.
The initial 10 second collection is precautionary in nature, as a fluid with
little filtration properties may fill up the 15 mL receiver tube almost imme
-
diately, potentially damaging the regulator. Do not record the 10 second
collection as a separate notation, but do record the volume collected at
the other time intervals.
While collecting filtrate, maintain the test temperature within ± 5°F (±3°C).
If the back pressure rises during the test, cautiously reduce the pressure
by opening the valve on the receiver and drawing off some of the filtrate
into the graduated cylinder.
29.
At the end of the test, close (tighten) the top and bottom valve stems to
seal off the cell.
30. Turn both regulator T-screws counterclockwise to close off the flow of
pressurized gas.
31. Open the outlet valve on the back pressure receiver to collect all of the
remaining filtrate.
32. Open the bleeder valve on the manifold block to release any remaining
pressure in the line.
33. Remove the manifold block and the back pressure receiver. Drain any
residual filtrate from the receiver into the graduated cylinder.
The heating jacket will still be very hot. Be careful not to touch it while
removing the back pressure receiver.
