Abstract: A hydraulic oil filtration apparatus 40 comprises an actuation control valve V, a pump-pressure oil passage 41, a connection oil passage 43, a tank oil passage 51, a return filter 60, a drain oil passage 53, a drain filter 70 and an aspirator structure 90. The actuation control valve V controls to charge and discharge a hydraulic actuator A such as a boom cylinder 22 and travel motors with hydraulic oil from a hydraulic pump P, which is connected through the pump-pressure oil passage 41 to the actuation control valve V The hydraulic actuator A is connected with the actuation control valve V by the connection oil passage 43, and the actuation control valve V is connected to a tank T by the tank oil passage 51, in which the return filter 60 is provided. The part of the tank oil passage 51 downstream with respect to the return filter 60 is connected to the hydraulic pump P by the drain oil passage 53, in which the drain filter 70 is provided.

Abstract: An assembly for removing hydrophilic contaminants and a method of removing hydrophilic contaminants such as sodium included in an oil-state liquid using the removing assembly, which is able to remove positively the hydrophilic contaminants such as the sodium included in the oil-state liquid in each process of the plant such as a phenol producing apparatus as well as maintain a certain level of the removing performance for a long duration, consisting of: a coalescing element for coalescing and separating from the oil-state liquid the moisture including the hydrophilic contaminants such as sodium by being penetrated the fiber layer having the characteristics of alkali resistance and solvent resistance, typified by a carbon fiber; a liquid feeding means for feeding and supplying a mixed liquid of the moisture including the hydrophilic contaminants and the oil-state liquid; a water collecting means for collecting the moisture including the hydrophilic contaminants which is coalesced and separated; and a oil colle

Abstract: An oil filter for filtering oil is combined with a differential pressure indicator with temperature compensation. The differential pressure indicator has a spool assembly slidably disposed in a spool insertion cylinder in axially confronting relation to a terminal which is connected through a warning lamp to a battery. The spool assembly comprises a spool body disposed for axial sliding movement in the spool insertion cylinder, a contact member disposed for axial sliding movement in the spool body and having a contact pin movable out of one of the spool body, and a spring of a shape-memory alloy, restorable to a memorized shape when the oil is in a predetermined temperature range, for biasing the contact member to move the contact pin out of the spool body towards the terminal. When a differential pressure in excess of a predetermined level is developed in the oil and applied to the spool assembly, the differential pressure acts to move the spool assembly towards the terminal.