BUCHI Inert Loop B-295 - Manual (Page 54)

6 Operation
54 B-290 Operation Manual, Version I
Usually the Inert Loop is set on -20°C for optimal solvent recovery. Some solvents tend to freeze
in the Inert Loop B-295, while working with those please adjust the set temperature to a higher
one, use the buttons c and d. The display of the Inert Loop B-295 e shows the set tempera-
ture and the current temperature.
2. Switch on the aspirator (see figure 6.2 on page 52).
3. Check whether the spray gas source is an inert gas, normally nitrogen. Open the needle valve
at the flow meter and adjust the flow to the requested level. The closed system now starts to be
inertised (see figure 6.2 on page 52).
4. As soon as a certain pressure drop threshold is reached by the gas flow and spraying gas, the
signal lamp of the pressure display g is switched off. If the pressure drops under the threshold
(due to glass breakage, stop of gas inlet, taking away of a glass component etc.), the peristaltic
pump and the heater are blocked. This is indi cated by a lit signal lamp g and the message PR
LO on the display of the Mini Spray Dryer B-290.
5. The overpressure in the system due to the constant flow inlet is limited by the exhaust outlet at
the Inert Loop B-295, which is permanently open. Therefore, no overpressure can built up. The
gas mixture from the exhaust outlet is slightly conta minated with solvents. This gas flow must
undergo an after treatment and be disposed of according to regional standards and laws.
6. The oxygen concentration decreases due to the con stant inlet of inert gas. As soon as the
concentration is below 6 %, the signal lamp of the oxygen control f goes off. If the oxygen
threshold of 6 % is exceeded (e.g. by using pressurized air instead of inert gas), the peristaltic
pump and the heater are blocked. This is indicated by a lit signal lamp f and the message O2
HI on the display of the Mini Spray Dryer B-290.
7. As soon as both signal lamps f and g go off, the peris tal tic pump and the heater are
unblocked and can be turned on. The spray process can be started. The blocking and signals
are reversible. If the pressure increases or the oxygen decreases, respectively, the pump and
heater are unblocked again and must be started manually.
8. At the left bottom side of the Inert Loop B-295 a flask is positioned to receive the condensed
solvent. To empty the flask, close the drain valve and take out the flask carefully.
6 .7 .1 Status messages
Table 6-1: Status messages at the Mini Spray Dryer B-290
Code Description Possible cause Corrective measure
O2 HI O
2
sensor indicates exces-
sively high O
2
content
Oxygen connected instead of
nitrogen
System not yet sufficiently inert
(display on oxygen measurement
equipment still above threshold level
but falling)
Oxygen enters system because of a
leak Connect nitrogen supply
Wait until threshold level is reached
Check tubing system (seals in place
and in proper condition, cover firmly
closed)
PR LO Pressure monitor shows
operation taking place at too
low pressure
Leakage in gas circulation system or
clogged filter Check tubing system (seals in place
and in proper condition, cover firmly
closed) or replace/clean filter