Roger,
I agree with most of what you said, except for the longevity of the DI or
Distilled. We used Disitlled rather DI, because we found the DI was too
aggressive. I installed and maintained both water cooled and Vapor Phased
cooled UHF TV transmitter up to 240KW for 25 years, and over that time, I
never saw the kind of failure rate in the flow system hardware that you
descibe. However, we regularly drained and flushed our systems. About every
60 to 90 days on average. We monitored Ph levels more than conductivity,
because it was a bigger problem. If the water was let go until it was
contaminated enough to have high conductivity, the water would generally
have become very acidic, and I suppose you would see the kind of failures
you describe, but when the water was changed every 2 or 3 months, the system
parts lasted for a dozen years or more in fact most of the plumbing lasted
the life of the transmitter. Heat exchangers usually were worn thin by 10 to
15 years and had to be replaced, but the copper and brass components seemed
to hang in there.Now so far I am describing the procedure for the Vapor
Phase systems. The water cooled systems were run longer because most of them
were a 50/50 mix with Glycol, because they were at elevations where is would
get pretty cold. The water cooled systems were much more friendly than the
steamers. The steamers were constantly distilling the water and making the
water more aggressive and picking up more impurities. The 50/50 mix water
systems were only changed about once per year, and their flow systems gave
very little trouble.either. The procedures we used were pretty much by the
book from Varian. And of course all this stuff ran 24/7 as well. If it
didn't there was lots of explaning to do. Biggest failure component we had
on the steamers was the rubber boot on the wehr, they would only last a
little more than 2 years, so you wanted to make sure you stayed ahead of
that, because it was a hect of a mess when they let go!
73's
Chuck
W6RD
----- Original Message -----
From: "Roger (K8RI)" <sub1@rogerhalstead.com>
To: "F. Veitch" <fletchv3@comcast.net>
Cc: <amps@contesting.com>
Sent: Friday, May 16, 2008 12:17 PM
Subject: Re: [Amps] liquid cooled Amplifier coolant recommendations
> F. Veitch wrote:
>
> I used and have worked with water cooled amps and oscillators for
> years. We used De Ionized (DI) water for years with systems up to
> multi-hundred KW. Either DI or distilled water should work fine. Most
> tap water is far too conductive. Just put your ohm meter on the high
> scale and stick the probes in a half inch to one inch apart. As long as
> it shows 50-100K it should be fine. I used a probe that had 1 CM
> square plates separated by 1 CM to measure Ohms per cubic CM , or
> resistivity.
>
> The only thing to remember about DI and Distilled water is they are
> corrosive to copper and brass. However the amount of flow in
> intermittent amateur service should show no degradation in years of
> use. You might need to replace the water every now and then as it picks
> up ions from the metal in the system. Others have commented on how they
> monitor this. If there are no indications of lower conductivity there
> is no need to replace the water. In systems that ran almost steady 24
> X 7 we had to replace copper and particularly brass fittings every 3 or
> 4 years. Based on that I'd expect the normal amateur system to last a
> lifetime. Water replacement which was around a thousand gallons was
> about twice a year, but it ran through a lot of equipment and in an
> industrial environment. I'd hate to tell all the stuff that went into
> that, but a half a salt shaker in a thousand gallons shut the whole
> system down. That was expensive in the 100's of thousands of dollar
> range, but we never did find out who did it we were fairly certain. Just
> rumors from the crews running all that equipment. Word was someone
> remarked, "I never thought that little would do that much". <:-))
>
> Look into "Vapor Phase" cooling as well.
>
> 73
>
> And good luck,
>
> Roger (K8RI)
>> I am in the process of getting a water cooled GS-15B cavity on line and I
>> wonder if the group has any recommendations on coolants. Distilled water
>> is
>> typically of unknown provence, so you are never sure if it is really low
>> conductivity unless you measure it. Somehow the idea of 1700-2000V on
>> water
>> of unknown conductivity just bothers me. (silly me!) I have heard that
>> some
>> Radar systems and high power lasers use a special ethylene glycol for a
>> coolant. I wonder if anyone in the group has any experience with such
>> coolants and if they can recommend a source for same.
>>
>> Thanks and regards
>> Fletch
>> K3JYD
>> FM18
>>
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>>
>>
>
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