Cable Sheathing Material "LSZH"

zero halogen means no chlorine, so not PVC, but polypropylene and polyethylene are candidates for ZH. However neither are exactly 'low smoke', this is generally achieved by adding finely powdered mineral fillers (aluminium or magnesium oxides  or hydroxides for example, or in some case chalk, a carbonate that gives of CO2 when heated)


The inert filer means the fuel to thermal mass ratio no longer favours a run-away burning reaction, this is In much the same way as wet wood needs so much extra heat to heat the water before it can get hot enough to self ignight  it that a fire tends not to keep going.


Exact mixes and which mineral fillers are probably a jealously guarded trade secret. They certainly blunt your wire strippers faster, and the ones with a lot of mineral are quite stiff.

Hi.

Thanks for the swift reply.

So sheaths could be PP or possibly PE, so might actually be XLPE plus filler in some cases?  The cross linking is not particularly important to what I'm looking into but I just ask out of interest.


Thanks!

As an aside if you are equipped to measure dielectric constant, you can say something about the fraction of the mineral loading - pure PP and PE have an Er of about 2.5,  while the oxides are about 10, so even though the filler is a few tens of percent, it has a significant effect. The loss  tangent also rises.

Just be a bit wary about "LSF" - claims of low smoke and fume aren't quantifiable


LS0H cabling will have limits on the specific gas production and the amount of obscuration created by the test samples.


Be wary of polyethylene - it may be zero halogen, but will produce a lot of obscuring smoke when involved in a fire - ditto for some fillers - certain types of below ground comms cabling is filled with basically petroleum jelly wrapped up in medium density polyethylene - donot need to run it far inside a facility before it's a real problem


Regards


OMS

Thanks OMS.  Agreed, we ought to rely on standards such as BS 7211, or better Euroclass classifications to be clear about what we specify in terms of smoke and halogen emissions.


Interesting point about petroleum jelly filled PP telecoms cabling - I wonder how the authors of BS 6701 thought that might be managed!

Sure  - reliance on a standard that has identified and repeatable test criteria has to be better than some vague description of performance like "LSF"


As for gel filled cable, then I tend to not run it more than say 1 - 2m into a dedicated Building Entry Facility (BEF) before terminating it and converting to a more sensible indoor grade cable spec. Make the BEF as fire sterile as possible, and wrap it up in 60minute protection - not usually a problem if you consider your comms to be important to you


Regards