FW: [3dem] Prepump airlock

[Kenneth Goldie]

Hi Eduardo,

On our Tecnai F30 when you press the prepump airlock "button" this
initiates the opening of V41, the valve between the turbo pump line and
the airlock. This valve then stays open until the sample holder has been
loaded. You should hear a click when it actuates. My understanding is
that this "cleans up" the vacuum in that line so there is no vacuum
differential between the vacuum lines at this point. Valve V8 is
positioned after this and opens a few seconds after the holder is
inserted to pump the holder.

When you say it stops working it probably means you had a better vacuum
in the line between V41, V8 and the nitrogen airing valve (V42 from memory) and that in fact it is working (and the turbo pump is at operational speed). The red light on the compustage will turn off more quickly than if the line has a poorer vacuum, taking
longer to pump. You will see all this if you watch the vacuum overview
page.

If this is not the case then right, you have a problem. My experience
working on machines before this prepump airlock function was instigated
is that it does not make a big difference (unless you have not loaded a
sample for a while and the vacuum in the line has really dropped quite a
bit. I would recommend using it if you have it though.

All the best

Ken

Ken Goldie
Electron Microscopy Unit Manager
Bio21, Molecular Science and Biotechnology Institute
The University of Melbourne
30 Flemington Road,  VIC 3010, AUSTRALIA
Email:      goldie at unimelb.edu.au

 

________________________________

From: 3dem-bounces at ncmir.ucsd.edu on behalf of Terje Dokland
Sent: Sat 5/23/2009 12:08 AM
To: Eduardo Sanz Garcia
Cc: 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] Prepump airlock



In our case (Tecnai F20) it has always pumped for only 3 sec, as long 
as the turbo pump is already warmed up and ready. (If not, the Turbo 
warmup time f 3 mins would be added to the pumping time.) It doesn't 
seem to make any difference if you run it or not, so I'm also 
wondering what the purpose is.

On May 21, 2009, at 9:09 PM, Eduardo Sanz Garcia wrote:

> The "prepump airlock" of our Technai F30 used to pump for about ~30-60
> sec. and all the sudden it stopped working (currently only pumps for
> just 2 sec).
> How can we fix/change that? Is the "prepump airlock" function 
> totally necessary?
>
> Thank you.
> _______________________________________________
> 3dem mailing list
> 3dem at ncmir.ucsd.edu
> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem

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