Hach Ultra ORBISPHERE 3624, Operator'S Manual

Page: 30 / 102

24 of 96 Installation - 3624 ProBrix Plus
Operator Manual
ORBISPHERE
Purge the CO
2
sensor with reasonably pure (99.8% or better) nitrogen at a flow rate of
10 to 50 ml/min. The gas must be maintained at a controlled pressure of 2-bar gauge. Do
not exceed this purge gas pressure, since excess pressure inflates the sensing
membrane and falsifies measurements. To adjust the pressure, lift the pressure adjustor
(see
Fig 1-14 for location) and turn until the correct pressure is reached. Press on the
adjustor to snap shut and lock it.
A 6mm Swagelok fitting is provided on the CO
2
sensor to attach the purge gas. When
installing, make one and one quarter turns of the nut. Use any convenient tubing (e.g.
nylon, tygon, or PVC) to conduct the gas to the sensor. A 15cm length of plastic tube is
supplied for the exit of the purge gas. To insert, push it firmly into the orifice diametrically
opposite the purge gas entrance. To remove, push on the ring surrounding the tube, then
pull.
To ensure continuation of purge gas while the sensor is in contact with the sample, it is
recommended to use a backup purge gas cylinder with an automatic changeover valve.
Drain the condensate periodically. Open the Condensate Bleed Screw (see Fig 1-14 for
location) and blow off any moisture under pressure.
The filter should be cleaned or replaced if it
becomes heavily contaminated. To check the Filter,
unscrew the Filter Cover (see
Fig 1-14 for location),
and then unscrew the Filter Holding Nut to remove
it. Clean with water and dry with compressed air.
To check the flow rate of purge gas leaving the CO
2
sensor, immerse the end of the exit tube into water.
With the instrument switched on, you should see at
least three bubbles per second during the purge
cycle (every 15 seconds).
Note:
Do not leave the exit tube permanently in the water.