Pertains to cast aluminium alloy enclosures pressurized with dry air, inert gases, for example sulphur hexafluoride or nitrogen or a mixture of such gases, used in indoor or outdoor installations of high-voltage switchgear and controlgear above 1 kV, where the gas is used principally for its dielectric and/or arc-quenching properties with rated voltages - above 1 kV and up to and including 52 kV and with gas-filled enclosures with design pressure higher than 300 kPa relative pressure (gauge); and with rated voltage above 52 kV.