Penny,

A leak at the seal or the down-to-air vent could cause this. You 
wouldn't hear a lot from the turbo, as it wouldn't be able to spin 
fast enough. Can you monitor the roughing pump vacuum? That should 
give you an indication.

Paul Eby
University of Victoria

At 02:45 PM 11/01/2007, you wrote:
>Hi all,
>
>It's late and I'm tired and my Delta Plus XP is cheesing me off. I'm 
>sure I've simply done something stupid, but I can't think of what it is.
>
>We had to send our turbo pump back to Pfeiffer for repair (bad 
>bearing). I just got it back and am putting everything back 
>together. So far as I can tell, everything is tight and connected as 
>it should be.
>
>I turn on the pumps and get the normal gurgle from the rotary pump. 
>No shock, it's been sitting idle for nearly a month. The turbos 
>start up, as the gurgle continues. The turbos run quietly as they do 
>when there is not a leak in the system, but the rotary is still 
>gurgling away. The fail-safe finally shuts down the pumps when the 
>turbos are unable to reach 70% (or whatever the cutoff is) of their 
>operating speed.
>
>Everything is tight, and the turbos don't howl like a jet engine as 
>they do when there's a leak in the system, so I'm at a loss. I've 
>checked to be sure the source is seated properly in the source 
>housing, and it's OK. The one thing I'm not sure I have attached 
>right is the down-to-air vent on the turbo. It looks right, but 
>there are so many washers and rubber rings that I could have it 
>wrong - could an incorrect installation be causing this problem? I 
>suppose I could check that by simply removing it and inserting the 
>plug to see what happens.
>
>Is there anything else it could be? Could it be an artifact of the 
>rotary sitting for so long (I don't think so)?
>
>Yarrrgh!
>
>Thanks all,
>
>~Penny
>
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>                       Dr. Pennilyn Higgins
>                        Research Associate
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>                             "SIREAL"
>   Stable Isotope Ratios in the Environment Analytical Laboratory
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