Teledyne 4250 Installation And Operation Manual page 92

4250 Flow Meter
Section 3 Installation
3-2
You will need to remove the particles from the cartridge for
regeneration; you cannot regenerate the cartridge like the case
desiccant canister. The cartridge is plastic and will melt. See
Section 5 for details on regenerating the desiccant cartridge.
Be sure to remove the red plastic cap from the desiccator car-
tridge when you install the flow meter. If you do not, the AV
sensor will be unable to reference to atmospheric pressure,
and inaccurate level measurements will result.
Many flow meters are installed in damp environments in atmo-
spheres containing corrosive fumes. These fumes can form weak
acids with moisture. Keeping the desiccators active and the door
closed will prevent these fumes from damaging the flow meter.
Keep the lid closed and latched except when you are installing the
unit or changing the program.
Do not operate the flow meter with the door open or the desic-
cators saturated. If you leave the door open, moisture in the air
will quickly saturate the desiccant. Dust may damage the printer
mechanism. Water or dirt drawn into the reference port can block
the tubing, preventing the pressure transducer from sensing
atmospheric pressure.
Symptoms of a clogged reference port on the AV sensor are
varied. Noticeable drift in measured level when you know the
level is essentially constant, or an oscillation in the level corre-
sponding to changes in barometric pressure are two indicators of
clogging in the reference port tube.
If dirt and/or moisture block the reference tube between the des-
iccant cartridge and the AV sensor connector on the flow meter,
you may be able to clear the blockage from the tube by applying
compressed air. Likewise, if the blockage is inside an extension
cable for the AV sensor, you can try to clear it with air. In these
cases, both ends of the tube are accessible.
However, if the blockage is inside the AV sensor's cable, the
sensor may be ruined. The cable is sealed where it enters the AV
sensor and the sensor itself is a sealed unit. Consequently, you
cannot push air through the tube. Applying pressure to the con-
nector will only drive the water further into the line, and may
destroy the transducer inside the probe. If you suspect blockage
in the AV sensor's reference tube, return the probe to Teledyne
Isco. The repair department may be able to vacuum the water or
blockage from the line; however, water may cause permanent
internal damage, and not all blockages are removable.
You can avoid this problem completely by preventing moisture
from entering the reference tube in the first place. Maintain the
desiccators. Inspect them frequently and regenerate them when
necessary.
CAUTION