On 14/11/2019 12:44, David Round wrote: > He said that the rats would prefer to gnaw on the armoured cable and > would easily cut through the CST armour. Does anyone have any > real-world experience of this? Should we be installing SWA armoured? > Are there any other actions we should be considering? The rodent > control chap suggested sealing up the ends of the ducts in each > chamber, not to stop the rats, but to allow us to track them so that > we can find where they are getting in to the network.
CST cables *can* be constructed in such a way that the outer jacket itself is corrugated, which makes it easier for rodents to grasp and chew on, so there might be a little bit of truth there. But they're also available from most manufacturers in a double-sheath configuration with a smooth outer jacket, which eliminates that. CST will be a pretty good protection regardless - rats won't easily go through a decent quality CST armoured cable, or SWA. SWA is much nastier to work with for fibre, though - nightmare to strip and anchor, and a pain to ground (and if you're using metallic-armoured cables, you are grounding the armour, right?). Flexibility isn't as good as CST, either. Chemical additives to the outer jacket (capsaicin, etc) can also help, but most manufacturers only provide this in concert with CST; I've seen some chemical-only options for LSZH/plenum applications though. Presumably the really hard core rats that can chew through steel don't live in building voids. It's widely reckoned to be less effective than armour. Making the cables' outside diameter bigger will also help by preventing the rat from getting their jaw into a position to bite down. Have you considered using a large outside diameter sub-duct, if your main ducts permit it? Sealing up ducts is a good idea anyway - doesn't cost much, helps prevent water/gas ingress into chambers, and it will help dissuade less hungry rodents. -- Cheers, James Harrison
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