DURRIDGE RAD7 User Manual - Page 13

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5 CARE, MAINTENANCE, AND TROUBLESHOOTING

5.1 Water Catastrophe

If water ever enters the RAD7, or if the RAD7 ever

goes swimming in the water, it will probably cease to

operate and immediate steps should be taken to

minimize the impact on the instrument.

Keep the RAD7 upright. This will prevent water from

touching the detector, which is close to the face plate

at the top of the dome. Put a piece of tubing on the

RAD7 outlet with the other end in a sink. Use the

RAD7 pump if it still works or, otherwise, an external

pump into the inlet, to blow air through the

instrument. When water ceases to be blown out of

the outlet, put desiccant upstream of the RAD7 to dry

out the air path. When the air path is fully dry (after

dry air has been blown through it for approximately

one hour), remove the face plate from the case, empty

the water out of the case and blow dry the case and

the RAD7 electronics.

Once there is no visible water in or on the

instrument, it can be put in an oven at 50°C for a few

hours to dry out completely. Additionally, desiccated

air can be passed through the air path until the air

leaving the RAD7 drops below 10% RH. After this

treatment further corrosion will be prevented, and

the RAD7 will boot once more and you can use the

internal RH sensor to measure how dry the air path

is. At this point the instrument should be returned to

DURRIDGE for service.

5.2 RAD7 Care

Water, particularly salt water, is hostile to electronic

instruments. Please keep the RAD7 in a relatively

clean and dry environment. One way is to enclose the

instrument in a large, transparent plastic bag; see

Section 1.2.3. Should it ever be seriously splashed

with salt water, please follow the instructions in

Section 7.1, above.

As a preventive measure, plastic cling wrap can be

placed over the RAD7 face plate and down the sides

of the RAD7. Push it down around the hose

connections, push the power and RS232 plugs into

their sockets, and push the lid onto its hinges. The

wrap will make the RAD7 almost watertight. If it

tears it can be easily replaced at any time. The

instrument should, in any case, be returned every

year for recalibration.

Section 5

Care, Maintenance, and Troubleshooting

It is useful to look at a cumulative spectrum

periodically. This may be obtained by having the

printer on and allowing the RAD7 to complete a run.

The "Recycle" number may be set to the current cycle

Setup, Recycle, NN [ENTER]

number (

the RAD7 reaches the end of the current cycle it will

then print out the end of run summary including the

cumulative spectrum. Look to see that the peaks are

clean and in their normal positions.

5.3 Exchanger Care

There is a potential for biofouling to occur in long-

term monitoring applications. The exchanger should

be kept as clean as possible in the circumstances. The

Water Probe should therefore be inspected

periodically to ensure that there is good contact

between the radon exchange tubing and the

surrounding water, and no clogging with weeds,

algae, etc.

5.4 Desiccant Regeneration

Please see the RAD7 manual for information on the

care and regeneration of the desiccant. Regenerated

desiccant, after a few regenerations, loses most of its

indicating ability (due, we believe, to migration of the

cobalt chloride to the interior of the calcium sulphate

crystals). One way to 'indicate' the status is, every

time you reﬁll the laboratory drying unit with

regenerated desiccant, you ﬁrst add half an inch or so

of new, blue desiccant, out of the jar. This way, you

can always tell if the unit is still working, as the new

desiccant will only turn pink when the rest of the

desiccant, upstream, has become hydrated.

5.5 Water Probe Troubleshooting

5.5.1 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 ﬁttings (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.

). When