Filter unit

Abstract

The arrangement of the disclosure comprises a filter unit having an upper, inlet chamber and a lower, outlet chamber. A hydrophilic filter separates the upper chamber from the lower chamber and a lower placed hydrophobic filter or membrane separates the lower chamber and the upper chamber. A liquid reservoir is provided in the first chamber between the filter and membrane, and a gas reservoir is provided in the second chamber between the filter and membrane. A liquid admitted to the upper, inlet chamber with a forward differential pressure, that is with the pressure in the upper chamber larger than that in the lower chamber, will flow through the upper hydrophilic filter into the lower chamber. If any gas accumulates it cannot accumulate above the level of the lower hydrophobic membrane. Accordingly no gas flows out of the lower, outlet chamber in the forward direction. If there is a reverse differential pressure, reverse liquid flow is prevented by the hydrophobic membrane and by air trapped above the lower hydrophobic filter against the upper, wet hydrophilic filter. If liquid supply to the upper chamber fails and a forward pressure differential exists between the chambers, forward gas flow is prevented by the wet upper hydrophilic filter and the liquid trapped above the hydrophobic filter. Therefore the unit filters the liquid flow, vents gas in the outlet chamber to the inlet chamber, prevents forward gas flow, and prevents reverse liquid flow.