AMI Analyzer Manual
Expanded Installation Procedure
16
it should drop to less than 10ppm in less than 20 minutes, if it has been installed properly, the temperature
is above 50
º
F, and always assuming your sample has less than 10ppm of oxygen in it. (Cold temperatures
cause the sensor to respond more slowly).
You may be required to perform a low level span – this means spanning the analyzer with a suitable span
gas whose value is close to where the analyzer will be operating. If so, it is essential that the analyzer gets
down to a lower value than the span gas value, or it will take forever to exponentially work its way down to
the span gas reading.
Often this operation causes problems. For example, the span gas may be contaminated, or the regulator
hasn’t been properly bled. A good first step is to simply run the span gas through the analyzer and see what
it reads. If it is close to the correct value, you can go ahead and span it. If it isn’t, you MUST trouble shoot
why not before you believe the span gas! The calibration you just did on air is going to be accurate to
within about 2% of reading, probably, which is closer than many span gases!
20. If desired, span with known calibration gas.
a) Connect a regulator (with Stainless Steel diaphragm ONLY) to span gas tank.
A regulator with any other kind of diaphragm will allow oxygen to diffuse into the gas, contaminating it.
b) Bleed high pressure side of the regulator 7 times.
This effectively removes trapped oxygen from the air in the primary side of the regulator. If you just try to
purge it by flowing gas through it, it will take a very long time to get rid of all the air and you may
contaminate the gas in the bottle. Bleeding the regulator can save days of time.
c) Bleed low pressure side of the regulator 7 times.
Removes the air from the secondary side. Bleeding the regulator can take days off the stabilization time.
d) Shut off the regulator outlet valve and leak check all fittings, gauges and packing glands with
Snoop
or equivalent.
Again, flow the liquid on, don’t spray it on. Make sure you check the regulator and tank valve as well.
e) Flow calibration gas preferably through a length of AMI supplied tubing WHILE you are
connecting the tubing to the span gas fitting. Allow the gas to purge around the fitting for
about 20 seconds before you tighten it.
It is preferable to use the AMI special flexible non-diffusive tubing with its O-ring sealed fittings so that you
don’t destroy the span inlet fitting on the analyzer. This can be purchased from AMI as an option.
Compression fittings can only take a few openings and closings before they cease to seal well enough for a
trace oxygen analyzer. Flow the gas through the tubing while you attach it to the span fitting: screw it on by
one thread allowing the gas to escape around it, and after about 20 seconds tighten it up. This displaces the
air from the fitting, meaning that you don’t inject a slug of air onto the sensor and delay it coming to
stability.
f)
Tighten fitting on the span gas inlet.
Use Snoop™ or equivalent to leak check it.
