Abstract: An automatic backwashing strainer system is provided for cleaning a strainer with a minimum amount of backwash water. The system includes a long time mode and a short time mode of operation in which the backwashing operation is conducted periodically with a variable duration and a variable cycle time. The system also includes a differential pressure mode of operation in which the backwashing is conducted whenever the pressure drop across the strainer exceeds a predetermined upper limit and continues for a variable time delay after the pressure drop reaches a predetermined lower limit. The particular durations, cycle times, time delays, and modes utilized to control the backwashing are selected in response to the operating conditions of the strainer system.

Abstract: A strainer is provided for removing particulate debris from a fluid passing therethrough. The strainer is primarily of the automatic type having a hollow body, a cover, a strainer element and a backwash arm assembly for cleaning the strainer element. The strainer element is a cylindrical, convoluted screen having encapsulating end caps positioned at either end. The end caps and thus the strainer element are retained so as to avoid rotation in seal rings, one of which is connected to the cover and the other of which is detachably connected to the terminus of the backwash arm. The strainer element is a structural member capable of withstanding the loads imposed on it by the fluid.

Abstract: A strainer of the self-cleaning type includes a strainer element capable of removing matted debris by backwashing. The strainer element comprises a plurality of stacked annular strainer plates maintained in spaced relationship to form straining passages wherein the passages are substantially greater in depth than height. Protruding surfaces of the strainer element form vertically aligned compartments along its upstream side. The compartments collect the debris. A rotating backwash arm or arms are provided which may carry at least one cutting blade. The blade cuts matted debris extending between compartments into sections as it passes over these protruding surfaces and these sections are removed by backwashing.