[Amps] Oil v water cooling

[John Lyles]

On 4/17/15 10:00 AM, amps-request at contesting.com wrote:
>> Hi, I believe that not all "distilled water" is suitable for this, you may
need to specify "deionised water". The water conductivity needs regular 
checking,
it will rise as it gets contaminated by traces of solder flux etc...I 
seem to
remember where in a published design for a watercooled amplifier that 
about 6"
from the tube anode that the plastic cooling pipe went through a brass 
coupler
that had a meter connected between it and chassis ground to monitor 
leakage current.
Regards David G0FVT

Yes, exactly. The brass coupler and meter just insert a volt meter into 
the water pipe, to measure the actual leakage current, like measuring 
the voltage drop across a shunt. Getting it calibrated is the trick. If 
you have 6 inches of pipe from the brass sleeve to ground and now the 
diameter, can calculate the resistance for a given value of resistivity 
of water.

>     As a retired* broadcast engineer with plenty of experience
> maintaining vapor and water cooled transmitting tubes I highly
> recommend ONLY "steam distilled" water over any deionized water.
> Deionized water can contain dissolved minerals that the demonizing
> process cannot remove, namely dissolved silicates which are plentiful
> in Florida water.   (elsewhere I have no knowledge)
>     These minerals do get deposited in the cooling circuit and an acid
> rinse does not dissolve them.  (they are white glass like coating)
>

The literature from Varian + Eimac (CPI) and the other tube companies 
recommends deionized water. CPI website has this info in several app 
notes. By using proper resin bed followed by an oxygen removal stage, 
mineralization is not a problem. A continuous process through these 
bottles (available from Culligan and Cuneflow) will keep the water pure. 
This is industry practice, from companies like Continental Electronics 
to users such as our particle factory. In a closed loop system, the 
water must be continuously 'polished' this way, and the equipment is 
called, appropriately, the polishing loop. The bottles are replaced 
about once per year in the installations that I maintain/design.

Steam distilled water might be a good starting point, but I cannot 
imagine that the closed-loop process includes a distillery and the 
incipient energy consumption required to continuously boil and re- 
condense a large flow of water in real time.

>     I will add that operating these high power tubes with water on their
> collectors (through the Ammeter and overload relay coil) is made much
> easier by grounding the collectors and supplying the high Voltage to
> the cathode with the power supply terminal with the surplus of
> electrons.  (the negative terminal)
 > * after 50 years and 5 months.
 > -- Ron KA4INM - Youvan's corollary: Every action results in unwanted
 > side effects.

Indeed, Klystrons and IOTS are typically run that way, with the 
collector grounded or just off ground (to measure body current from the 
voltage between the body and the collector to see how much beam is being 
spilled). Then the negative HV is applied to a floating cathode/filament 
with isolated heater transformer.

For those of us using PGT (power grid tubes) though, we typically have 
B+ on the anode and have to insulate those pipes.

Oil vs water:
I like water only in that we always find leaks and water on the floor 
and equipment is a lot easier to clean up. The federal gov't doesn't 
like having oil spills, even indoors. Also, for the Specific Heat 
Capacity as Ron suggested.

73
John
K5PRO