Paul,
We had problems with burning holes through the sides of the ash tubes, 
the tube would fuse to the combustion column, the quartz wool liner 
would fuse to the quartz wool in the combustion column and it was often 
difficult to get the ash tube out of the column.  These problems were 
solved by reducing the combustion column temperature 1020°C to 1000°C 
and putting a thin layer of chromium oxide on top of ash tube quartz 
wool.  I think the reason this worked is that quartz tube is real close 
to its softening temperature and when the flash combustion occurs enough 
heat is released for quartz to melt locally.  Also, the quartz wool in 
the ash tube no longer fused together so flow was not affected.  This 
change in temperature did not adversely affect our results.  We use the 
Costech 4010 analyzer.

For easy removal of the ash tube use a round Sharpie marking pen (it is 
~1.1cm in diameter).  The slightly tapered shaft of the sharpie easily 
forms a wedge fit to the tube and out it comes.  We have been using the 
same marking pen for years.

Bill Reichert
NW Fisheries Science Center
Seattle, Washington


Paul Eby wrote:
> Listmembers,
>
> I've been having trouble with ash tubes from our EA breaking lately.
>
> We use Elemental Microanalysis C1090, which is open both ends and has 
> slits on the bottom half. I have a small bit of quartz wool at the 
> bottom of the tube, and at the top of the reactor. Typically, the tube 
> is stuck when I try to remove it, and breaks near the top of the ash 
> level when I force it. This occurs regardless of whether I am at full 
> temperature or standby temperature, and I have had the same trouble 
> with tubes that are closed at the bottom.
>
> My best guess is that the slag is seeping through the slits and fusing 
> to the reactor tube. Does anyone have any applicable wisdom?
>
> I'm considering the vacuum removal method at this point....
>
> Paul Eby
> University of Victoria