Cast components having reduced porosity levels are produced by pouring a molten metal into a mould which is in a first chamber, and withdrawing the filled mould into a second chamber. The second chamber is then isolated from the first chamber with regard to pressure, and the second chamber is then pressurized with a fluid up to a maximum pressure of 7 MPa for at least part of the time required for solidification of the metal in the mould. The pressure is preferably applied within forty seconds from the finish of pouring of the molten metal, and more preferably within twenty seconds. The still molten state of the metal permits the use of a relatively low pressure to reduce the porosity levels.

Centrifugal oil filters are described comprising a rotatable centrifugal cleaning cartridge, a shaft for rotation thereon, a co-operating member for connecting the filter assembly to a source of fluid to be cleaned, an outer casing member, a closure member for sealing one end of the casing member and a fluid drain conduit and wherein the centrifugal cleaning cartridge may be removed without removal of the outer casing member or disconnection of the fluid drain conduit.