Another possibility might be the stuff used to clean cooker/oven parts.
It is a liquid that you dunk shelves, burners etc in. I think it is used
cold and must be fairly "frisky" to burned on carbon and yet presumably
benign to metals. I think it is called Oven Pride but not sure as it is
not in my "department".
I'm a bit concerned that this compressor seems to have been run so hot
that it would burn the oil. My compressor does get hot - too hot to keep
my hand on but that should not decompose oil.
It is possible Malcolm but compared with the dire warnings on the now
banned "Kleen-off" which was NaOH in a gel, this stuff has less warnings
and at the same time we have been more H&S conscious, so I'm minded to
think it might be OK with metal bearing in mind that many hob burner
parts are diecast aluminium.
Are you suggesting that shiny oven shelves are not made of chromed steel?
Don't you think any oven cleaning product might be careful how much
sodium hydroxide they put into their magic formula?
Just in case you don't know:
Well sometimes I aqctually learn something new here. It appears that
chrome is dissolved by caustic, but *very slowly* which is a good thing
because I have been using caustic to clean fatty gunk off chrome since
With no apparent ill effects.,
The lifetime of any political organisation is about three years before
its been subverted by the people it tried to warn you about.
Ah yes, I've used such bought from the Poundshop to (quite
effectively) to clean the grilles from our oven. I think you mixed up
the chemical, tipped it into a big Ziplok bag, added the metalwork and
then moved it about a bit to 'coat' all the metal bits then leave it
for a while to do it's stuff. You then took the metal bits out and
they were all clean and shiny. ;-)
The thing is, these particular 'silent' compressors only have a 50:50
duty cycle with a maximum on time of 30 mins. So, let's say it was
being run hard (a worse duty cycle) and using the older mineral(?) oil
then I'm wondering if it was a possible cause of it starting to coke /
As soon as that happens, some carbon get under the (fairly light) reed
valve and it not make pressure, even if not being used it would then
run continuously (and silently) and could therefore run pretty hot and
for a long time?
The rest of the guts 'look' ok, the bore isn't scored and there
doesn't appear to be any crank / gudgeon / big-end noise and because
it was so lacking in oil (and obvious signs of being opened), a good
chance any oil that was in there was still in there when they noticed
it wasn't working was tipped out rather than burnt out.
The oil is drawn up the wet sump though the spinning crankshaft /
armature and then just spray lubricated all the bits at the top (big
end, piston / bore, top bearing etc).
The bits in question can be seen on the bottom half of the 'Pump
Diagram' page (4) seen on the link below:
The reed valves in question are either side of the 'Valve plate' (item
26). One is just trapped against the gasket and held in place with two
dowel pins but the other is held down under the raised 'horseshoe' /
end stop you can see in the diagram. This would allow that reed to
'open' about 2-3 mm at the top of the 'U' before being restrained by
said plate. The ends of the retaining plate are riveted to the main
valve plate and it's that bit I'm trying not to disassemble (by
drilling out the rivets, cleaning and possibly re-setting the 'spring'
in the reed and re-assembling using countersunk machine screws and
possibly locking nuts (not sure the nylon would survive the heat in a
Cheers, T i m
Given the warnings in the manual about ensuring no leaks to avoid
damage, it seems that the 50:50 is a warning to the user not to exceed
50:50 duty rather than saying the compressor itself is controlled to run
at max 50:50.
I wonder if the thermal trip device has failed shut and that a leak
present has meant the unit has cooked itself. Modern copper wire has a
very high temperature enamel so possibly not a concern but could have
led mineral oil to burn.
TBF, the only sign of anything untoward is this buildup on the
*outside* of the valve plate and inside of the cylinder head (if that
means anything to anyone).
The air is drawn in via a sort of plenum chamber us sucked into the
head via the reed inside the valve plate and then blown back out
though the horseshoe reed, round the head and back out though another
manifold / reservoir chamber, before being discharged out through the
delivery pipe to the reservoir (though a non return valve).
As the piston is ringless, they predict a certain amount of oil
bypassing the piston and so getting into the cylinder and potentially
out though the output reed / head.
Cheers, T i m
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