JP2652491B

PURPOSE:To surely and stably perform detection operation of the clogging of filter paper and perform filtration with high efficiency by detecting the deposition and clogging by impurities of the filter paper by relatively large change in pressure on the pump outlet side. CONSTITUTION:A vessel VS where liquid to be filtered is housed and used is connected to the introducing part of a filter FL. On the other hand, a pump PM driven by a motor MT is connected to the discharging part of the filter FL on the introducing side and is connected to the vessel VS on the outlet side. As a result, impurity-contg. liquid delivered from the vessel VS is filtered by the filter FL and returned to the vessel VS again through the pump PM. A pressure detector PD is fitted to the outlet side of the pump PM. When the oily liquid is not smoothly filtered, pressure failure is detected by the pressure detector PD on the outlet side of the pump PM and when the pressure becomes lower than a specified one, filter paper in the form of a web is moved. Thus, the filter paper of the filter is moved by the output of the pressure detector PD in a timely manner.