Green gunk found
- Thread starter ro63rto
- Start date
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It sounds like the conductors have not been terminated properley and the insulation has burned which makes the green like substance you are likely to have, dunno about it being greasy though?, its usually powdery and dry...
Or it is pre 1970 PVC, and you are looking at the 'green gunge of death' as the PVC decomposes. Some cable makers had problems with their choice of plasticiser (some phthalate derivitives), and it leaches over time, and reacts badly with the copper.
The decay is excaerbated by heat. Very mild cases can be wiped of with a cloth and methyleted spirits, and the cable left in service if the insulation resistance remains within acceptable limits.
However, rather like advanced cases of nob-rot beyond a certain point there is no happy cure, and then affected circuits are better treated by replacing the cables.
The other effect that can occur is at higher tempoeratures when the PVC decomposes in such a way as to liberate hydrchloric acid (HCL) In small doses the stabiliser (usually lead or cadmium) will absorb this to form a non-soluble chloride, preserving the insulation even when damp. However, once all the stabiliser has been used up, the resistance of the cable will start to fall. Thus cables that have been overloaded or wrapped round the heating pipes may exhibit this problem first.
Pound to a penny if it is from the green gunge era you have no earthing your lighting circuit either.
From about 1974 onwards the plasticiser problem was recognised, and all makers adopted the more stable formulations. (but the lead is still present, and the plastic will release bothe HCL dioxins if burnt at normal temperatures, so don't burn the old stuff.)
The decay is excaerbated by heat. Very mild cases can be wiped of with a cloth and methyleted spirits, and the cable left in service if the insulation resistance remains within acceptable limits.
However, rather like advanced cases of nob-rot beyond a certain point there is no happy cure, and then affected circuits are better treated by replacing the cables.
The other effect that can occur is at higher tempoeratures when the PVC decomposes in such a way as to liberate hydrchloric acid (HCL) In small doses the stabiliser (usually lead or cadmium) will absorb this to form a non-soluble chloride, preserving the insulation even when damp. However, once all the stabiliser has been used up, the resistance of the cable will start to fall. Thus cables that have been overloaded or wrapped round the heating pipes may exhibit this problem first.
Pound to a penny if it is from the green gunge era you have no earthing your lighting circuit either.
From about 1974 onwards the plasticiser problem was recognised, and all makers adopted the more stable formulations. (but the lead is still present, and the plastic will release bothe HCL dioxins if burnt at normal temperatures, so don't burn the old stuff.)
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BenStiller said:
It's di-octyl phthalate.
Green exudate from PVC
Draft BCA statement (April 2001)
1) PVC
PVC comes in two main grades, plasticised and unplasticised PVC.
Unplasticised PVC (UPVC) is used for example in double glazing window frames where a rigid material is required.
The PVC used for manufacture of cables is a plasticised PVC that conforms to the relevant British Standard for the cable type in question.
2) Ageing effects
As a cable ages (at temperatures above normal ambient) the elongation to break decreases (also the Insulation Resistance increases). The life expectancy of a cable is arbitrarily considered to be when the elongation to break of the PVC is 50%.
A lower elongation to break value could be considered suitable especially for a fixed wiring cable. Therefore, providing the cable is not subject to movement or when moved due to inspection of socket outlet or the like, the PVC does not crack, a much lower value of elongation to break is considered by some as suitable.
3) Greening
Greening is the appearance of a wet green substance that is a product of an adverse reaction between certain types of plasticiser and the copper conductors. This greening, which is a rare occurrence, can happen either after a long period of time for some cables, or if the cable has been severely overheated.
The plasticiser itself is a clear oily liquid that is non conductive. The green substance is a combination of copper oxide and plasticiser which may become conductive under certain adverse conditions.
4) Action if Greening is found
Therefore whenever this green substance is found at socket outlets etc. initially it should be removed and the terminations cleaned (gloves should be used) otherwise it is possible that tracking/overheating may occur. It is strongly recommended that rewiring should be carried out as soon as possible.
If further information is required, the original cable manufacturer should be contacted.
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