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Self-cleaning Air Filters

29th May 1959, Page 53
29th May 1959
Page 53
Page 53, 29th May 1959 — Self-cleaning Air Filters
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KNOWN as the Far-Air Rotonamic, an IN. air filter for oil engines being produced under licence to the American Farr company of Los Angeles by Intermit, Ltd., Bradford Street, Birmingharit, 5, is a self-cleaning unit with an exhauStextractor system incorporating a venturi aspirator. The filter provides filtration of dust particles in the 0.6 to 6.0 micronparticle range, and efficiencies of up to 96 per cent. are obtainable.

When equipped with a Roto-Pamic dry-type after-filter, the combined units give an initial and average efficiency of 99 per cent., and can deal with particles with a mean diameter of 2 microns. Although the elements of the after-filter have to be renewed periodically, the period between replacements is greatly extended by the action of the exhaust extractor in removing a large percentage of the dust in the first filtration stage. The after-filter elements can be replaced in a few minutes.

Cyclone Cleaner

Rotonamic filters comprise a series of separation elements having the shape of a small cyclone chamber with a tapered end, the air being given a swirling action by a vaned hub located in the mouth. A central tube, open at both ends, is fitted to the boss of the hub and extends to the discharge nozzle, ' where its outer periphery forms an annulus with the inner surface of the cyclone chamber. Dust particles are centrifuged by the action of the air and continuously scour the surface of the chamber before discharge at the nozzle.

About 10 per cent. of the air is discharged with the dust at high velocity, the remaining 90 per cent. returning to the hub end of the central tube in a spiral flow close to the outer surface. This purged air is then drawn through the inside of the tube to the after-filter, or direct to the intake manifold of the power unit. The dust is removed continuously by the exhaust venturi aspirator, which eliminates the need for periodic servicing to .remove dust concentration if no after-filter is employed. cleaning.

The smallest -filter in a range of 11 types has four separator units and a capacity of 25 to 39 c.f.m., and is suitable for power units with outputs of up to about 40 b.h.p. Incorporating 64 separation units, the largest single filter has a capacity of 806 to 1,255 clan. and units of any size may be combined to give intermediate capacities not included in the standard range or capacities above that of the largest single filter.

When the Roto-Pamic after-filter is employed, filtration efficiency is not reduced by an accumulation of dust exceeding the normal holding capacity of the unit. Partial blockage of the filter restricts the volume of air flow and causes a corresponding reduction in the engine performance, and in this way provides a clear indication that the elements of the after-filter require renewal. It is claimed that blocks of solidified dust cannot be separated from the elements and enter the air stream.

A typical application is quoted by the company in which a combined Rotonamic and Roto-Pamic filter was employed to filter the air of a power unit fitted to a quarry vehicle operating in an atmosphere having a high percentage of fine dust. A conventional oil-bath filter fitted to the engine of a similar vehicle required servicing at 8-hour intervals, whereas the Roto-Pamic afterfilter operated for 700 hours before replacement of the dry elements was necessary. The combined filters also afforded a reduction in bore wear. Oil-bath an filters of the Far-Air type manufactured by the concern operate on the viscous-impingement principle, and it is claimed that a pressure loss across the filter of approximately 5 in. water gauge remains virtually constant throughout the operating period. After passing a guard screen in the filter casing, the air is divided into two streams, a large percentage of the total volume being drawn vertically through a venturi section and impinging on the wetted surface of the filter panel.

The secondary air stream is initially diverted downwards to the filter sump, where it agitates the oil before carrying droplets of the lubricant vertically to the filter area to wash the screen. Finally it descends on the opposite side of the panel through an inertia eliminator to the sump.

All dust particles are removed from the panel by this continuous washing action, and servicing is limited to removal of sump sludge and renewal of the oil.

Tags

People: Birmingharit
Locations: Los Angeles

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