Abrégé
A method for manufacturing of ceramic electro-insulating pipes having an external diameter between 30 mm and 100 mm, a wall thickness between 5 mm and 10 mm, a length between 15 cm and 150 cm, the method comprising moulding in a mould, an element made from a ceramic powder, compacting the ceramic element in a press, glazing, firing of a glazed element in a furnace and shaping the fired element in order to produce the ceramic insulating pipe characterised in that the element is moulded in a mould (102) from a ceramic powder consisting of AI2O3 from 40% to 75% by weight, SiO2 from 5 to 25%, kaolin (white clay) from 5% to 20%, and potter's clay from 5% to 20%, wherein the mould (102) comprises a rigid cylindrical lower punch (202) and a flexible cylindrical outer membrane (203) placed around the lower punch (202) so that between them a cylindrical gap (204) is formed to be filled with the ceramic powder, wherein while filling the gap (204) with the ceramic powder, the outer membrane (203) is deformed from a circular cross-section to an oval cross-section with the use of at least one pair of vibrators (211-212; 213-214) positioned on the opposite sides of the membrane (203) and operating in at least three stages, in which the vibration frequency increases and the amplitude of vibration decreases between successive stages, wherein the lowest vibration frequency is between 50Hz and 70Hz, and the highest vibration frequency is between 90Hz and 110Hz, and wherein the vibration amplitude causes a reduction of the diameter of membrane between the vibrators from the lowest value of about 0.5% to the highest value of about 2%, wherein the filled mould (102) is placed in the isostatic press in order to compact the element, wherein the membrane (203) of the mould is pressed isostatically in a first cycle that lasts from 15 s to 25 s, in which the pressure is linearly increased from 1 bar up to a value between 300 bar and 800 bar, a second cycle which lasts about 1 s, in which the pressure is maintained at the level reached so far, and in a third cycle that lasts from 25 s to 35 s, wherein the pressure is reduced linearly to 1 bar, resulting in forming an element having a porosity of below 20%.
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