Ultrasonic Cleaners Revisited
- In the past there have been several discussions about using ultrasonic cleaners for cleaning locomotive mechanisms. Tonight came across a post from the yahoo Heathkit forum from one who has made use of ultrasonic cleaners for cleaning watch and electronic assemblies. Some of his tips and safety precautions apply to model locomotives so with the permission of Mike McCarty I am copying his post to here. Many of his comments apply to industrial strength ultrasonic cleaners and are not necessarily applicable to low power home-use cleaners, but still would be wise to keep these pointers in mind...
**** All below is re-posted to the Z Scale group with permission from Mike McCarty ****
I used to work as a watchmaker and clockmaker, and used ultrasound
for perhaps 15 years.
It works great, when it is used properly. It can have some
disastrous effects if misused.
One thing to bear in mind is cavitation. It generates quite a
bit of local heat, and can pit some things.
Another to bear in mind is that, if you have a hard part, and
it happens to resonate at or near the frequency used, it can
shatter. Springs, for example, are hard.
Another thing to bear in mind is that it is vibration, and it
can unscrew everything in sight, almost instantly, even if
lockwashers or some sort of loktite like glue is holding them
"immobile". Parts which are crimped on may vibrate off, and
be very difficult to replace, especially if they are "inside"
Solvents, when activated by the heat and vibration, are much
more active than when they are just sitting there. Chemical
reactions also take place faster when they are warmed, and
the local, temporary heating, can vastly speed them up.
The solvent will get into places it would not normally get,
and will react with things it does not normally react with.
It may be difficult to get all the solvent back out of the
small crevices it'll get into, without using heat to get it
back out. It may hide out inside sleeves around shafts, etc.,
for long periods of time, when just immersion would not get
it into there at all.
Anything held together with some sort of adhesive will
almost surely come apart.
Also, bear in mind that, when I used it on watches and
clocks, I always _completely_ (and I do mean absolutely
totally completely) disassembled the watch or clock first.
It would disassemble itself in the bath, anyway, and it's
hard to find small parts rolling around in the bottom of the
container, and it's also difficult/impossible to figure out
where they came from.
If there is any mercury, or other semi volatile substance in
there, it will likely come out as a very fine aerosol. I've
seen a blob of mercury the size of a pencil eraser disappear
into a vapor in the air. I recommend DO NOT BREATHE the
mist or vapors coming off of an ultrasonic cleaner. Some of
the gunk in that switch will turn into an emulsion which
will get turned into ultra small droplets of water or
whatever solvent is being used, and go into the air. The
mist may or may not be visible. It will certainly exist.
I don't want to breathe ultra small droplets of emulsified
old switch gunk.
Also, DO NOT IMMERSE YOUR FINGERS OR HOLD THE OBJECT to be
cleaned with your hands. The vibrations will cause cavitation
in your flesh. This is both painful, and harmful, especially
to joints. I used to use a basket to hold things, and lower
it in with the unit off, and then clean. I used a timer, and
when the time expired, I'd raise the parts. Since you don't
intend to disassemble the switch, that's not feasible, so
I'd suspend the switch with a piece of string.
With those caveats in mind, it works great when it works.
I would be willing to start the ultrasonic bath going, and then
just dip the switch in on one side, and withdraw it after just
a moment (maybe 3 seconds), while closely observing the effects.
If it looks ok, I'd try the other side. I'd just dip the switch
in for a few seconds at a time, and only part of it. If things
look ok, then I'd turn off the machine, and immerse the switch.
I'd then turn the machine on for brief period while observing.
Careful, not to breathe the mist!
Some mild detergent might help. Unscented diswashing liquid,
intended for hand washing of the dishes, not machine
washing, might be good. A few drops per cup should be enough.
I used to use green soap, but it's expensive.
I would clean repeatedly, until no more gunk came out.
After cleaning, I'd rinse, also in the ultrasound machine.
If more "gunk" came out during the rinse, then I'd
consider that another "wash". The last rinse should be
with distilled water. We don't want calcite (calcium carbonate)
crystals inside our switches, grinding them down.
Then, I'd dry the switch with gentle heat, like a hair dryer,
on low, until it achieved total dryness. At this point it
should be ready for lubrication.
On anything ferrous, I'd use hydrocarbons, as mentioned
in the later post I made. Kerosene might be good. I'd test
by evaporating to dryness a drop on a piece of glass,
like a microscope slide. Then, with light glancing on the
surface, look through the glass. You want NO RESIDUE.
Remember, anything left on there after evaporation to
dryness is going to be a solid, that is, crystalline,
and will act as an abrasive.
To clean copper based stuff (brass parts) I'd use water
+ detergent + ammonia. Use water to rinse, in the ultrasonic
bath, until nothing comes out. The last rinse should be
in distilled water.