Hach Ultra ORBISPHERE 29981, Operator'S Quick Manual

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Page 6
Using the Test Unit
The test unit (illustrated left)
allows for a variety of tests
with ou t ha vin g to p ierce
actual vials or ampoules.
A purge gas inlet is situated at
the bottom of the unit, with the
outlet at the top.
Check for Purge Gas Leaks
To test for purge gas leaks, place a beaker of
water on the sample platform. Then raise the
platform so that the needle is immersed in the
water (but the beaker is not pressing on the
needle or gasket).
Start the purge gas and regulate the purge gas
pressure to slightly more than atmospheric
pressure.
When the purge gas is on, bubbles should be
visible in the glass bubbler, and from the needle in
the beaker. However, when the purge gas is off,
the bubbling should stop.
The analyzer display should show a change of no
more than 0.01 kPa per minute, otherwise a leak
may be present and you should check all fittings.
Unable to Purge the System
If you observe no bubbles when the purge gas is
on during the preceding test, check to see if either
the piercing needle assembly is too tight or the
sensor is improperly mounted on the flow
chamber.
Sudden Jet of Water
A sudden jet of water can come out of the purge
gas exit tubing if the purge gas pressure is too
high. Excessive purge gas pressure can cause
gas to leak into the flow chamber during the
measuring phase, thus distorting readings. Adjust
purge gas pressure and flow rate.
Check for Air Leaks
If you suspect an air leak somewhere in the flow,
first make sure that your purge gas supply is
running, and that your sensor is at baseline, that
is, showing a typically low oxygen value.
Fill the test unit with deaerated water, full enough
to form a protruding meniscus at the test unit's
opening. Place the test unit on the sample
platform and raise the test unit. When the rubber
gasket forms a seal with the test unit, stop the
platform.
After five minutes, check the instrument
measurement. The oxygen value should remain
constant, rising no more than 0.05% (kPa) during
that delay. If the value increases significantly,
then you may assume that the system is leaking.
Check all appropriate fittings and try this test
again.
Alternate Check for Purge Gas Leaks
The display value could also decrease in the
preceding test if there is leakage of purge gas into
the flow chamber. First, verify the presence of
bubbles in the glass bubbler.
Then, place the test unit on the sample platform
and raise the platform until the rubber gasket
forms a seal with the test unit. Check to see that
the bubbling stops.
If the bubbling does not stop, the leak is
continuous. Disassemble the piercing needle
assembly, and replace the small O-ring. (Do not
forget to place a thin film of silicone grease
around the O-rings before reassembling the
piercing needle assembly.)
If the purge gas tubing "burps", the leak probably
is due to purge gas pressure that is too high.
Adjust purge gas pressure and flow rate.
Troubleshooting