Strip paper insulation appear when the power core is loosely wraped with telephone-cable or cable insulating paper. Every next turn is overlaid the previous one (20-25% from tape width). The width and the pitch of taping are designed in a such way that there are an air slot between the paper tube and the power core (pic.1, a).
Strip paper insulation is made by multiway vertical machines with central paper-lapping head.
The pulp insulation is formed on the core with cellulose. It looks like a cylindrical layer of paper mass with inner pores, which filled with air (pic.1, b). Wood pine unbleached sulphate cellulose is a raw material for the paper mass, which is also used for manufacturing various cable papers and electrical insulating boards.
Cable or phone papers wastes can be added to the cellulose. Basic specifications of insulating materials are shown in the table:
The manufacturing method of insulating consists of next operations:
- beating (shortening and splitting) of cellulose fibres in water;
- mass mixing and cleaning;
- watering up to 0.1…0.2% concentration;
- dosed supply of water paper pulp suspension into the insulated part of paper pulp aggregate – a buth, where the cage cylinder is rolling.
The fibres come down on 60 wires, which bend the cage cylinder, and form an insulating layer on each wire, the water filtered out with the cylinder warp. After that, the warps get through a former – fast rolling spiral planer, where the insulation is taken cylindrical shape. The process is finished by high-temperature drying in an electric furnace, thereby the wet is boiled off, forming pores in the mass.