ļ 2002 by ELTRA GmbH Germany ā January 2002 ā Service Manual OH 900 / ON 900 / ONH 2000
1.3-1
1.3
1.3
The flow rate is not stable
Please note: The gas flow in consideration is read on the right-side flow meter.
Vibrations of the ball inside of the flow meter is not a sign of an unstable flow rate. This is
an effect of the weight of the ball and the compressibility of the carrier gas in a small tube.
The flow rate is only unstable, if the average position of the ball becomes higher or lower.
First check the vacuum at the inlet of the electronic flow controller. It should be higher than
50 mbar. If it is not, check the tubes from furnace to flow controller.
If the vacuum is higher than 50 mbar, check the tubes following the flow controller.
Check the complete tubing from the furnace outlet up to the analyser outlet.
Otherwise change the flow controller.
Caution:
It has happened several times already, that the outlet of the furnace was blocked by
silicon grease. Due to an excessive greasing of the surface of the O-ring ( 4 ) of the lower
furnace closure, some of the grease can land onto the furnace outlet hole ( 1 ), causing its
blockage.
In this case open the furnace,
remove the tube ( 2 ) from the furnace outlet ( 1 )
and pass a pipe cleaner ( 3 ) through the
fitting ( 1 ) into the furnace area to
make sure that the hole is
completely free.
3
2
1
1-3
1
4
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