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from the Automation List department...
Impact of dust on electronic component
Continuous process industries, DCS questions. topic
Posted by Rajesh Dwivedi on 10 September, 2007 - 11:52 pm
As I saw in my plant that we cleaned the all DCS cards due to possibility of dust accumulation that may badly impact the functioning of the cards, since this is a nearly 10 year old plant. Can you explain how dust can impact the proper functioning of electronic equipment?


Posted by Michael Griffin on 12 September, 2007 - 12:58 am
A thick layer of dust can act as an insulator and cause higher power chips to overheat.


Posted by Curt Wuollet on 12 September, 2007 - 1:13 am
Dust is bad for several reasons:

It can insulate the devices causing them to overheat.
It can attract moisture causing leakage problems.
It can be directly conductive also causing leakage problems.
It can cause poor contact in relays, switches and connectors.
It can cause arcing and carbon tracking in higher voltage apps.
It makes it more difficult to service the equipment.
etc...

Regards,

cww


Posted by Eric Ratliff on 13 September, 2007 - 2:47 am
Some products offer 'conformal coating'. This makes them resistant to electrical conduction problems with dust. It does not help with thermal problems.

You can get very dramatic flame like arcs when the dust contains carbon fibers.


Posted by Eric Ratliff on 15 September, 2007 - 12:20 am
P.S. See http://www.dowcorning.com/content/etronics/etronicscoat/etronics_cc_tu torial.asp?DCWS=Electronics&DCWSS= about conformal coating.

Eric Ratliff
www.icpdas-usa.com

moderator's note: please make sure you remove the blank spaces in the url when you copy and paste this into your web browser.


Posted by CSA on 13 September, 2007 - 1:52 am
Dust by itself can be conductive, causing "tracking" and even arcing between components on printed circuit cards as well as causing overheating because heavy accumulations can act as an insulating "blanket".

Dust, when combined with humidity and other vapors in the air, can lead to even worse "tracking" and arcing between components on printed circuit cards. Depending on the voltages involved and the circuitry, this can lead to all manner of intermittent and "unexplained" phenomena. Certain types of dust when combined with humidity can even be slightly corrosive to electrical components.

I have seen power plants where control room doors were continually left open in dusty, dry environments and poor maintenance and lack of housekeeping standards allowed heavy concentrations of oil lubricating vapors to combine with the dust on printed circuit cards. Over a couple of decades, these plants experienced all manner of nuisance and unexplained trips and "weird" occurrences. When replacing a printed circuit card in one particular plant one day, it was observed that the accumulation of oil vapors and dust was causing the solder joints to "dissolve" and components were loose on the card! Shortly after that (within days) there was a fire in the 125 VDC battery charger caused by arcing due to dust and moisture.

To this day, that plant has all manner of problems--and the control system gets blamed for every one of them. Good housekeeping is essential to maintaining a properly functioning plant.

These days, with the proliferation of PCs used as operator interfaces, cleanliness is even more important as it affects drive (hard drive, optical (CD and DVD) drive, floppy drive) life as well as chip life. So many times I've seen PCs just shoved under counters and desks, used as ottomans for feet, and then they fail and the plant can't be operated the blame is placed on the PC.


Posted by Mike McDermott on 13 September, 2007 - 2:36 am
Dust is very harmful. Dust bunnies, those little piles of dust you find, can actually cause arcing and can short equipment out.
http://en.wikipedia.org/wiki/Dust_bunny

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