Conductivity monitoring to detect integrity loss of glass coating of steel

by curious_cat   Last Updated July 11, 2019 20:25 PM

I have an application where the integrity of the glass lining of a glass coated steel vessel needs to be monitored.

In theory, once the integrity is lost anywhere there ought to be contact between the fluid inside the vessel and the underlying steel. The fluid inside is conductive, say water with salts in it.

In practice, would one be able to monitor the conductivity change and trigger an alarm?

To make the problem specific, say the vessel is 10,000 L capacity (cylindrical) and the glass lining is 2 mm thick (if that matters). Is it realistic to be able to detect a lining breach by monitoring conductivity?

Any other ideas for a detection system?

Alternatively, could the capacitance of the liquid-glass-steel or the air-glass-steel system be monitored? Would one expect the capacitance to change significantly if the glass gets a small breach?

To add more context:

If the breach in glass lining is detected early enough then there are ways to patch it up. Hence the goal is to try and catch the breach as small as you can. There's no breach that's too small since these linings are used in corrosive environments the smallest breach will allow the corrosive fluid to progressively eat away the underlying steel and then widen the breach.

i.e. It's only a matter of time for a small breach to turn into a large breach.

Answers 2

An interesting problem.
I seriously doubt that a continuity test will suffice for your application. This would require that you have a large enough fault in the glass surface to actually touch the outer container. I'd imagine that you may have a class of faults that are just cracks or blemishes that could only be detected by a Hi-pot leakage test.

There are plenty of commercial Hi-pot testers that should meet you need.

If you want to roll your own (inadvisable, though would be fun) then you could use something like a CO2 Laser power supply (20kV) with an optically isolated high side current detector (very high side!!). The dialectic strength of air is much less than that of glass (though your glass type is not specified). So if you position a high voltage ball probe at 3-4 mm above the glass you should be able to identify high leakage areas as faults.

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Jack Creasey
Jack Creasey
December 31, 2016 06:30 AM

This device does something that you re looking for:

Jürgen Reinemuth
Jürgen Reinemuth
July 11, 2019 19:37 PM

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