[Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like Me....

Mon Apr 1 11:01:27 EDT 2013

I have a very common Sargent Welsh two stage vane pump and it works great for 
getting moisture out of refrigeration systems.  Of course heat helps with 
something like a transformer.  In my experience the vane pump will do the job, 
but you need to leave it running for a while.  The water still comes out, but 
over some time.  I use a good solid 24 hours on refrigeration systems which were 
open and got real water inside, let my car system sit for almost 48 hours when 
none of the shops could fix it and it's been running perfectly for several years 
now.

Sure an ion pump system is better, but how many have that?  And yes, with the 
instrumentation you can see the moisture limiting the vacuum (or spot even the 
tiniest leak).  But for most people the refrigeration pump and time should do 
the job.  Consider that the propensity for the water to evaporate will not be 
significantly different at the micron vacuum of the mechanical vs the lower 
vacuum of the ion system, it's just that you can't see the water induced vacuum 
floor unless you have the better vacuum and the instruments.

On 4/1/2013 10:46 AM, Bill Carns wrote:
> Having worked on high vac systems a lot, I can tell you that a "roughing"
> pump (a normal mechanical vacuum pump) will not do a very good job of
> getting water out of a transformer....  The usual procedure in a high vac
> system, is to rough down to the floor of the roughing pump and then Ion pump
> on down to better vacuums. You can see when there is moisture in the system,
> as the vacuum will bottom out at a higher level while it "works" on the
> moisture.  Getting a water molecule out is much more difficult than getting
> out an air molecule.
>
> I would use the roughing pump in combination with some heat, or just the
> heat and time alone will do the job..  A roughing pump alone will not help
> that much. It sounds like you have the ability to heat the vacuum chamber
> and that is good.
>
> Bill
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Thekan, Paul
> Sent: Monday, April 01, 2013 9:23 AM
> To: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like
> Me....
>
> I have a vacuum chamber oven I saved from the dumpster here at work. I
> thought I could use it to dry out xfmrs under a partial vacuum. Just need to
> find an old Welch vac pump now.
>
>   Anybody see a problem with this...as long as I do not 'implode' anything.
>
> Tnx
> Paul
> N6FEG
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of J. Forster
> Sent: Monday, April 01, 2013 7:09 AM
> To: Todd, KA1KAQ
> Cc: Military Radio Collectors Association; milsurplus; ARC-5 List
> Subject: Re: [Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like
> Me....
>
> For years, I've always baked out stuff with non-hermetic magnetics.
>
> I put the thing on a few bricks, put a couple of 100 Watt incandescent lamps
> underneath it, and a big cardboard box with some holes in the top over it,
> and let it sit for a week or more.
>
> You want the thing to get up to about 130F for several days, at least.
> Longer is better, IMO.
>
> YMMV,
>
> -John
>
> ==============
>
>
>> On Mon, Apr 1, 2013 at 12:50 AM, David Stinson <arc5 at ix.netcom.com> wrote:
>>
>>>
>>> I thought about putting the whole thing sans end bells into a
>>> 200-degree oven for a couple of  hours to dry it out
>>>
>> This is  a problem with big chunks of iron in old transmitters, too.
>> Many do not realize how similar to a sponge the laminations and windings
> are.
>> And old transformer left sitting in a damp cellar or storage shed is
>> an accident waiting to happen if you just haul it out, hook it up, and
>> apply voltage. Might happen in 5 seconds, 5 hours, or 5 days, 9.9999
>> times out of
>> 10 it'll zorch.
>>
>> The oven works great as is provides a means of getting rid of the
>> moisture without introducing more. On bigger pieces it can take a day
>> or two, maybe more, to feel safe enough to put power to it. And
>> there's never a guarantee, of course. But recovery rate is far, far
>> better when dried out than when not. The trick is to heat it up long
>> enough for the heat to reach the core and drive out the moisture. It's
>> all about the mass. Smaller = faster; hours vs days.
>>
>>
>> A good reminder as many of my dynamotors are out in the garage here in
>> humid NC. Though lately humidity has been amazingly low.
>>
>> ~ Todd,  KA1KAQ/4
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