Guess the fault...

flyingsparks · 8 Nov 2011

Called today to a wool procesing plant because of reports of people getting small shocks off of a handheld control device for controlling a overhead crane. The entire control device is made of plastic and fibreglass, with no exposed metal parts. Well I found what was causing the tingles, any ideas?

Electrifying · 8 Nov 2011

Static?

ricicle · 8 Nov 2011

Stray piece of wool found it's way in to the controller and hanging out ? (wool can conduct electricity)

ColJack · 8 Nov 2011

that would likely be the steel wire either side of the control cable to act as support.... oh and static..
either from the plastic / wool interaction, or they just got new polyester overalls...

RUBICON52 · 8 Nov 2011

New flooring footwear or gloves?

flyingsparks · 8 Nov 2011

Its got nothing to do with static..

Ricicle is closest so far...

ricicle · 8 Nov 2011

Does the crane have exposed busbars ? Wool somehow in contact with them ?

flyingsparks · 8 Nov 2011

No. I'l tell you. There was a very small crack in the fibreglass casing on the controller. The grease from the wool had got into the controller and obviously was all over the outside of it from handling. The case was meggering with one probe on a contact inside and the other on the outside of the case, about 0.1M ohm. With some thinners and a rag I stripped it all down and cleaned all parts. That took the reading up to about 20M ohm! Didnt realise wool grease was so conductive! Putting the probes onto some wool about 300mm apart gave a reading of 0.05M !! Quite a interesting one!

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Guess the fault...

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