Self-cleaning centrifuge drum

In a centrifugal separator comprising

• a. a rotatably mounted separator drum having at least one sludge discharge passageway disposed at the radially outward periphery of the drum,
• b. a piston valve disposed within the drum extending from adjacent the drum axis to adjacent the radially outward periphery of the drum, and being movable vertically to open and close the sludge discharge passageway(s) for desludging,
• c. a closing chamber in the drum disposed outwardly of the piston valve extending from adjacent the axis of the drum to adjacent the radially outward periphery thereof, defined in part by the axially outward side of the piston valve, for receiving and discharging control fluid for, respectively, forcing the piston valve to the closed position and relieving force initiating the moving of the valve to its open position,
• d. a release passage communicating with a radially outwardly disposed portion of the control chamber for receiving control fluid from the control chamber for discharge thereof from the drum,
• e. a release valve in the release passage for closing the passage for holding control fluid in the control chamber and opening the passage for discharge of control fluid from the control chamber,
• the improvement which comprises:
• f. an annular chamber in the drum concentric with the drum axis and interposed between the closing chamber and the release passage for receiving control fluid from a peripheral portion of the control chamber and conveying the control fluid to the release passage, passageway means between said peripheral portion of the control chamber and the annular chamber such that with the release valve open, control fluid leaves the closing chamber through said passageway means so that the level of the control fluid is maintained concentric with the drum axis as the level in the control chamber moves radially outwardly so that tilting of the piston valve during emptying of the control chamber is prevented.