cathodic protection 3

[cenelected]

do shunt resistors have to be installed in exd enclosures in a zone 2 area

 

[gr2vessels]

Wrong forum, try Electrical / Electronics Engineers forum on left hand menu bar.

 

[ScottyUK]

EEx 'e' resistors do exist, and in fairly large sizes, so the possibility to use something other than EEx 'd' types is certainly there. I think the main requirement would be that the resistor temperature does not exceed the temperature class for the environment. Obviously there should be no spark-generating contacts in the enclosure, and the materials would have to meet the extended creepage requirements and so on specified in IEC 60079-7. If you're considering a moulded enclosure then the biggest problem may well be getting heat out of the enclosure.


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If we learn from our mistakes I'm getting a great education!

 

[cenelected]

cheers for that scotty im actually from teesside myself(small world) i am an EX inspector but have not had much to do with cathodic protection before as its normally installed by specialists as i am sure you know,these shunt resistors are known as an anti-fuse and i believe they can carry two circuits and if the smaller fuse blows due to a fault the higher rated circuit comes into play until this blows (eg shunt resistors are used in xmas lights)this is why if one light blows the resistance becomes higher and will blow the smaller fuse so the remaining lights still function,if more blow the resistance will be higher so the second fuse will blow,i now have a copy of the cathodic protection standards BS 7361-1 1991 and it states all cp apparatus installed in a hazardous area should be contained in a flameproof enclosure suitably rated for the area classification.

 

[ScottyUK]

Hi Ted,

Depending on what your CP system is protecting, you might want to look at BS EN 12954:2001 and BS EN 13636:2004 which are less prescriptive about the method of protection, essentially saying it should be in line with BS EN 60079. The old CP1021 is now withdrawn and BS 7361 (which replaced it) is largely superceded.

Life in the smog... I'm a missionary from a bit further north.


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If we learn from our mistakes I'm getting a great education!

 

[cenelected]

cheers scotty,
i will have to try and get info on what has been superceded in BS 7361,normally all of the kit ie,test posts,anode jbs etc are all installed in non hazardous areas ie for a petrol storage tank they would be installed outside of the bund wall,where i am they are not i think its a case of contractors cutting corners to make more money,thanks