Gel dryer / pump corrosion - New Pumps from Edwards

David Huen s.d.huen at
Sat Jun 18 04:17:59 EST 1994

In article <2trlgt$1k5 at>, Tony Hodge
<tph at> wrote:
> Subject: Gel dryer / pump corrosion
> From: Paulo Magalhaes, pamaga at
> Date: Thu, 16 Jun 1994 14:28:11 GMT
> In article <CrHuv0.6zq at> Paulo Magalhaes,
> pamaga at writes:
> >Hi all!
> >
> >A couple of questions concerning "small" problem we're having.
> >
> >Recently we found that the pump used with our gel dryer (a so-called
> >"one step oil pump"), got corroded and eventually stopped working.
> >The manufacturers claim that it must be something that gets into the
> >pump (the oil, in spite of regular changes, was *very* brownish).
> >Perhaps of interest, there was a "cold trap" installed between the
> >pump and the dryer.
> >

<stuff deleted> 

> We are presently evaluating one of a new series of pumps from
> Edwards which they believe will be more resistant to corrosion. 
> They are the RV series and we are trying an RV5 for drying down
> sequencing gels, ie lots of Acetic Acid.  We are NOT using a cold
> trap and the pump has an Outlet mist filter to trap oil droplets in
> the exhaust.  We have found that the exhaust does need to be vented
> to the outside or a fume cupboard but after some months of running
> the pump still pulls an extremely good vacuum.  A representative

<stuff deleted>

We have had a two-stage diaphragm pump for gel drying use manufactured by
Grieffenberger Anstriebtechnik GmbH Marktredwitz (copied off eqmt plate...
wots it mean...). As with many diaphragm pumps, the flow path is entirely
nylon/Teflon. While the vaccum it pulls is not good enough for freeze
drying, it is perfectly adequate for gel drying. It tolerates
water/acid/alkali flowing thru' it, operates in any position/orientation,
doesn't require oil and is reasonably priced. Over the 8+ years it's been
running, it has had no maintenance other than one diaphragm change (torn
from fatigue, prolly). Every other dryer pump here, both rotary and oil
ring types, has failed over the period and had to be replaced from
corrosion, some more than once.

I have no affiliation with the above company other than wishing I owned

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