Re: First the AI, then the DG, then...?

"G.R. Patterson III" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> David Lesher wrote:
> > 
> > Does garbage really migrate upstream into the expensive toys?
> 
> If a dry pump fails, the carbon vanes may turn into powder. When this happens,
> the pressure on the instrument side is lower than atmospheric pressure, and you
> may wind up with some of this powder being blown back into the instruments. In
> normal use, however, garbage does not migrate back upstream.
> 
> > (And if so, you'd thunk someone would add a inline filter between the
> > toy and the common vacuum line..)
> 
> Some people do this as a preventative measure. Alternatives include prophylactic
> replacement of the dry pump to attempt to ensure it never fails, using a wet
> pump, and cleaning the instruments before using them after a pump fails. The
> filter is cheap insurance.
>  
> George Patterson
>      
     A failed vac pump isn't likely to send garbage back up the line.
The instruments represent a significant vacuum leak, and the pressure
will drop off almost instantaneously when the pump fails. The filters
between the gyros and pump are more likely to keep garbage from a
failed instrument from gettingn into the pump, failing it as well.

 Dan