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A statistical method for estimating the parameters of a dynamic system, using recursive techniques of estimation, measurement, weighting, and correction. Weighting is based on vari- ances of the measurements and of the estimates. The filter acts to reduce the variance of the estimate with each measurement cycle. In navigation, the technique is used to refine the positions given by one or more electronic systems.

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This is an improvement on the wire gauze strainer. It can be cleaned whilst in operation and it can filter out particles down to 25 microns in size. The dirty oil passes between a series of thin metal discs mounted upon a square central spindle. Between the discs are thin metal star-shaped spacing washers of slightly smaller overall diameter than the discs. Cleaning blades, fitted to a square stationary spindle and the same thickness as the washers are between each pair of discs. As the oil passes between the discs, a solid matter of sizes larger than the space between the discs remains upon the periphery of the disc stack.
The filter is cleaned by rotating the central spindle, this rotates the disc stack and the stationary cleaning blades scrape off the filtered solids which then settle to the bottom of the filter unit Periodically the flow of oil through the filter unit is interrupted and the sludge well is cleaned out. To facilitate this the filters are generally fitted in pairs.
Pressure gauges are fitted before and after the filter unit, these give an indication of the condition of the filter. Auto-Klean filter unit capable of filtering out particles down to 200 microns in size, this type can also be made to filter particles of under 75 microns, but the mechanical strength of the cleaning blades will below. A more recent type of Auto-Klean strainer has the modified disc stack and cleaning blade arrangement. With this modified disc stack particles of under 25 microns in size can be filtered out without impairing the mechanical strength of the cleaning blades.


Any device or porous substance used as a strainer for cleaning fluids by removing suspended matter.

Wire gauze type filters are made with coarse or fine mesh depending upon the positioning of the filter unit in the oil system. An example of this are hot and cold oil filters fitted in oil burning and pumping installations, the coarse mesh suction filters are used for cold oil and the fine mesh discharge filters are used for the heated oil. The wire mesh type filter, however, is rarely made to filter out particles below 125 microns in size. If finer filtration is required, other types of filter units are used, one such filter unit is the well known Auto-Klean Strainer.


A filter cartridge made into a convoluted form that resembles the folds of an accordion.


Heat-exchange device similar to a plate-and-frame filter press; fluids flow between the frame-held plates, transferring heat between them.


A filter that has a series element and two parallel elements connected in the shape of the Greek letter pi ().


A frequency band in which the attenuation of a filter is essentially zero.


A filter press used during petroleum refining for the separation of paraffin oil and crystallizable paraffin wax from distillates.


Cartridge-type filter used in automotive oil-lubrication systems to remove metal particles and products of heat decomposition from the circulating oil.


1. A process in which oil is passed through a filter as it comes from equipment and then returned for reuse, in the same manner that crank case oil is cleaned by an engine filter. 2. A method in which solids are removed from oil by treatment in settling tanks.


[ENG ACOUS] A band-pass filter in which the upper cutoff frequency is twice the lower cutoff frequency.

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