Abstract: A device for liquid pumping, including a main chamber and a pump chamber for receiving a subportion of the liquid to be pumped from the main chamber and which is provided with means for cyclic variation of the pressure in the pump chamber between a pressure greater than a pressure less than the pressure in the main chamber. The pump chamber is connected to the main chamber by at least one input opening and at least one output opening. The input opening has a substantially lower flow resistance in the direction into the pump chamber than in the opposite direction and the output opening has a substantially lower flow resistance in the direction out of the pump chamber than in the opposite direction.

Abstract: A method of cleaning watery i.e. humid, ventilating air containing liquids which have been gasified during cooling or lubrication of converting machines, particularly rolling mills, comprises cooling of the ventilating air in one or several stages to a temperature below the condensing point of the gasified substances in the ventilating air, so that these substances condense. In connection with the condensation, the larger portion of the condensed cooling or lubricating liquids is separated from the water and reused. The condensed water mixed with the rest of the condensed cooling and lubricating liquids is returned to the cleaned and dried ventilating air and is caused to be absorbed by the ventilating air. By dividing the cooling operation into two steps, the cooling and lubricating liquids can be caused to condense in the first stage without condensation of any water and water can be caused to condense substantially only in the second stage.