On 4/17/15 10:00 AM, amps-request@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
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