Abstract: A low pressure relief valve having a flow passage therethrough providing fluid communication between the interior and exterior of a vessel the interior of which is under a low positive or negative pressure. A valve port in the flow passage has a valve seat therearound and a closure member is carried in said valve body for engagement with the valve seat to block fluid communication between the interior and exterior of said vessel. The closure member is of a preselected weight and is free to disengage the valve seat in response to a predetermined increased pressure differential between the vessel interior and exterior, without being affected by any other force than gravity, to permit fluid communication through the flow passage for reducing the pressure differential.

Abstract: A rotating filter apparatus is disclosed having a stack of sintered filter discs mounted on a vertical, rotatable hollow shaft and located within a chamber, the shaft having a plurality of radial openings therein to the hollow bore of the shaft. Unfiltered fluid is introduced under pressure to a tangential entry port in the same direction as disc rotation. The shaft is rotated at a speed sufficient to create a water boundry on the surface to aid the filtering of particles. The clean filtered fluid flows inwardly through the discs and down through the shaft, while the unfiltered fluid and the solid particles, or sludge materials, descend in the chamber to the bottom of a concentration chamber, which includes inwardly slanted sidewalls. The free-flowing sludge flows out of an outlet connection, with the more solid sludge taken out either through a hydrocyclone or a tapered auger connection.