Hach ORBISPHERE 31xxx Manuel D'utilisation Simplifié page 10

• Hand tighten the attaching collar.
• Connect the sensor cable.
• Check for leaks; replace O-rings if product leaks are visible.
Instructions for micro volume flow chambers
Do not twist the sensor when inserting it into a micro volume flow chamber. This rotation may twist
the protection cap, thus changing the membrane position. This can modify the membrane measuring
conditions, and affect measurement precision.
5.4 Sensor removal
• Shut off the sample flow and drain the sampling circuit from liquid or gas pressure.
• Remove the sensor cables connected at the sensor side.
• Remove the purge gas connections.
• Hold the sensor body in one hand to avoid rotation, and unscrew the collar with other hand.
• Pull the sensor straight out of its socket, or flow chamber.
• Check that both O-rings remain in place inside the flow chambers.
• Install the storage cap on the sensor.
5.5 Purge gas system
5.5.1 Purge gas regulator
The role of the ORBISPHERE 29089 gas regulator is to deliver purge gas
filtered at 40 μm. Attach the unit to a suitable bracket, using the M3 threaded
holes on the back. It's position should be vertical ± 5%. The gas flow is
indicated by an arrow on the regulator's body.
Maintenance:
Drain the condensate periodically. Unscrew by hand the drain at the bottom of
the bowl.
If filter is contaminated:
• Turn off the gas supply
• Unscrew the bowl by hand
• Unscrew the black disc at the bottom
• Remove the white composite filter
• Wash under clean tap water, blow dry, and install
5.5.2 Purge gas supply
Make sure there is no interruption in the purge gas supply. The use of a backup gas cylinder and an
automatic changeover valve, that activates when the first cylinder is empty, are recommended.
Use a 6 mm flexible (nylon or PVC) or rigid (stainless steel) line to connect the pressure regulator
and thermal conductivity sensor to the purge gas supply. Swagelok connectors (6 mm or 1/4") are
provided.
A short length of plastic tube is supplied for the purge gas to exit the sensor. To insert, push the tube
firmly into the orifice. To remove, push on the ring surrounding the tube, and pull the tube out. For
certain applications such as waste gas, a 3 mm (1/8") Swagelok fitting is provided for the purge gas
exit, to enable safe evacuation of an eventually hazardous gas.
A source of dry and filtered gas (pure at 99.8%) is required with a flow rate set at 10 to 50 mL/min.,
and a pressure regulated at 2 bar gauge. Do not exceed this, since excess pressure will deform the
membrane and change measurements.
To check the flow rate, put the exit tube into a cup of water. With the instrument turned on, you
should see at least three bubbles per second during the purge cycle.
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