Want info on Savant Gel Pumps

David Johnstondaj daj at uk.ac.ic.nhm
Fri Aug 27 03:32:15 EST 1993


On Thu, 26 Aug 1993 15:48:44 GMT,
  chris burns writes:

>Howdy,
>
>Our lab needs to replace the vacuum pump that we use to dry our gels.  We
>are thinking about the Savant (GP100) pump, as the oil-free design is
>particularly appealing.  The company claims that the pump can be run
>without any cold trap whatsoever.  Does anyone out there have any first
>hand experience with one of these things?  We'd really like to get some
>oppinions before we buy.

We have been using one of these for 18 months to dry down our sequencing 
gels and, subject to 2 minor design critisisms, think it is brilliant. As 
I understand it, the basic concept is that the fluid from the gel passes 
through a heater immediately before entering the pump and thus passes 
through the pump as a vapour, hence no problems with fluid damaging the 
pump. The pump has telfon cylinder heads (and chamber?) so (a) doesn't need 
any oil lubrication (hence no problems of water getting into the oil) and 
also (b) isn't affected by corrosion problems (from acetic acid and the 
such like) It is very smooth and quiet in operation and dries a sequencing 
gel in about 20 minutes. You need to prewarm the pump by running it for 
about 20 minutes prior to drying your gel (I always prewarm the drier 
itself aswell).

I have 2 minor critisisms:

(1) The vacuum gauge between the drier and the pump is extreemely useful 
for telling when the gel is completely dry but its inner workings are 
made of brass and so corrode on contact with acetic acid (we fix 
sequencing gels in 10% acetic acid, 10% methanol). Ours lasted approx 12 
months before it stopped working. The other lab in the museum which has 
one had the same thing happen. Replacement gauges from Savant are not cheap 
and the screw thread on them seems a funny size (so we couldn't source a 
direct replacement elsewhere). However you can buy from general lab 
suppliers, very cheap "inline" vacuum gauges supported on what looks like 
the base of a bunsen burner with 2 horizontal metal nozzles to connect 
to the vacuum line. These are dirt cheap (approx 20 quid) and do fine.

(2) After the pump is a little plastic pot to trap fluid (you put granules 
of "acid neutalising chemical" (calcium carbonate?) in it). IMHO this is a 
pathetic bit of cr*p engineering/design, cheaply executed and is a classic 
case of spoiling an expensive ship for a hap'peth of tar. It 
comprises a standard plastic specimen pot with 2 holes drilled in its 
lid. It is attached to the exhaust port on the underside of the cylinder 
block by a plastic fitting passing through one of these holes. A porous 
dome screws into the other to vent gas. It didn't fit properly and 
leaked. After much good humoured complaining to the Savant distributer in 
the UK, I was given a small plastic fitting with a screw thread on one end 
(to fit into the exhaust port (a non standard screw thread?)) and a hose 
barb on the other. I have connected a standard 100ml side arm flask to this 
to trap fluid and it works fine.

Hope this helps

DAJ
David A. Johnston
Dept of Zoology, The Natural History Museum, Cromwell Road,
South Kensington, London SW7 5DB.
(tel 071 9389297, fax 071 9388754, email daj at nhm.ic.ac.uk)



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