- Sat May 09, 2015 12:10 am
#47445
RoSy, to answer your question about silicone grease: it is an insulator, and prevents the passage of current.
HOWEVER, it has a very low film strength, and this is why it is used in electrical connectors. At the points where the metallic contacts touch or slide over each other, the silicone grease is displaced (due to the low film strength) and thus the metallic contacts can touch each other and conduct electrical current from one to the other.
Where the contacts don't touch, the film of grease remains intact, and thus forms a waterproof "shell" all around the contacts. You can fill a connector with silicone grease, which will prevent any water from entering it, but which will still allow the metal contacts to touch each other.
You can do exactly the same thing with vaseline (petroleum jelly). BT has hundreds of millions of individual connectors in its underground network, all of which are supposed to be protected against water ingress. The great majority of them are filled with petroleum jelly. It keeps the water out, but allows metallic contact when the metal parts (the conductors) are pressed together or slid over each other.
HOWEVER, it has a very low film strength, and this is why it is used in electrical connectors. At the points where the metallic contacts touch or slide over each other, the silicone grease is displaced (due to the low film strength) and thus the metallic contacts can touch each other and conduct electrical current from one to the other.
Where the contacts don't touch, the film of grease remains intact, and thus forms a waterproof "shell" all around the contacts. You can fill a connector with silicone grease, which will prevent any water from entering it, but which will still allow the metal contacts to touch each other.
You can do exactly the same thing with vaseline (petroleum jelly). BT has hundreds of millions of individual connectors in its underground network, all of which are supposed to be protected against water ingress. The great majority of them are filled with petroleum jelly. It keeps the water out, but allows metallic contact when the metal parts (the conductors) are pressed together or slid over each other.