paragraph. Should that not prevent the foam rising
too far, the intensity of the spray and
fl
ow velocity of
the water will need to be reduced.
Th
is will slow
down the speed of response of the RAD AQUA and
RAD7 system.
7.5.2 Spray Chamber Fills With Water
If the spray chamber
fi
lls with water, the air return
tubing inside the spray chamber may be too long.
Th
e open end should be about half way between the
spray nozzle opening and the water level in the base.
If the tubing is too long it is easy to disassemble the
RAD AQUA (simply remove the knurled nut and pull
the assembly apart) and cut o
ff
the extra tubing
length.
Another cause of the spray chamber
fi
lling with water
is the depletion of dissolved gases.
Th
is would cause
air to be lost from the air loop. A bleed inserted
between the check valve and the spray chamber air
connection, with approximately 1m of tubing, will
replace any air that is removed and will establish the
air pressure inside the chamber at atmospheric
pressure.
In addition, the spray chamber may
fi
ll with water if
the system’s air loop is not closed, or if it has a
signi
fi
cant leak.
Th
is will cause the air pump to
remove air from the spray chamber without replacing
it. Verify that the closed air loop has no open
connections or leaks.
7.5.3 Air Path Integrity
When drawing a sample from a remote location, air
path integrity is essential to prevent dilution of the
sample with ambient air. Always make sure that
there are no loose connections or leaky
fi
ttings (such
as the screw cap of the laboratory drying unit) in the
air loop, particularly upstream of the RAD7. In the
event of unexpectedly low radon values, check the air
path for integrity.
7.5.4 Poor Spray Formation
If the spray pattern is degraded, with no or
inadequate spray curtain, the response time of the
RAD AQUA will be increased, though the eventual
equilibrium for radon will not be a
ff
ected.
(
Th
oron
equilibrium will be seriously a
ff
ected because the
additional time to reach equilibrium allows more of
the thoron to decay.)
One cause of a poor spray is a pump of insu
ffi
cient
strength. Be advised however that larger pumps may
cause other problems related to the supply of power.
If a bigger pump is not an option, another way to
increase the
fl
ow rate to generate a better spray is to
switch to smaller nozzles.
Disassemble the RAD
AQUA, and replace the nozzles with smaller ones.
7.5.5 Water Over
fl
owing From Base
Where possible, place the RAD AQUA somewhere
that over
fl
owing water doesn't matter. It is also
advisable to screw the drain hose onto the lower base
outlet.
Th
e top outlet may be opened and if
permitted, water may be allowed to spill from the
outlet directly.
Section 7
Care, Maintenance, and Troubleshooting
21
