Abrasive tool making process – material – or composition – With carbohydrate or reaction product thereof
Patent
1990-08-10
1991-11-19
Rachuba, M.
Abrasive tool making process, material, or composition
With carbohydrate or reaction product thereof
51321, 51428, 51436, B24C 300
Patent
active
050655515
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to apparatus and methods for abrasive cleaning or cutting.
BACKGROUND ART
Techniques for the underwater cleaning of surfaces have for many years relied principally on the use of manual or powered brushes, scrapers, chisels etc.
More recently, in an effort to improve cleaning efficiency, in such applications as the subsea cleaning of welded regions of metal structures prior to safety testing or inspection where high standards of cleaning are demanded, blast cleaning systems employing a high pressure jet of an abrasive slurry have been tried, using water as a carrier for the abrasive. However, the use of such slurries has been found to present many difficulties. For effective cleaning action, the slurry must emerge from the nozzle at a pressure of at least 2000 psig (141 kg/cm.sup.2) above the local hydrostatic (ambient) pressure, more typically from 7000 to 15000 psig (490-1060 kg/cm.sup.2) above the hydrostatic pressure. As well as the need for expensive pumping equipment and components capable of withstanding the very high delivery pressures required, large reactive forces are generated at the nozzle, causing difficulty in orientation and manipulation, and considerable danger to the diver operating the equipment. Furthermore, the equipment is prone to very high degrees of internal abrasion from the high pressure slurry.
DISCLOSURE OF THE INVENTION
The present invention is based in one aspect on the finding that by preparing the abrasive stream in a particular manner described in more detail below, a method and apparatus can be achieved permitting faster, safer, and more effective cleaning at relatively low nozzle pressures. Indeed we have found that the action of the abrasive stream can be so effective that the apparatus can be employed for the purpose of abrasive cutting of materials.
According to a first aspect of the present invention, there is provided an apparatus for abrasive cleaning and/or cutting, suitable particularly but not exclusively for underwater abrasive cleaning and/or cutting, which comprises a mixing zone for preparing an abrasive mixture comprising abrasive particles, air (the word "air" herein including also other gases) and a liquid, an outlet nozzle for directing a stream of the mixture at a surface to be cleaned and/or cut, a pipeline connecting the mixing zone to the outlet nozzle for conveying the abrasive stream to the nozzle, and means for supplying the abrasive particles, air and liquid to the mixing zone in such a way that the resultant abrasive stream includes abrasive particles at least partially (preferably substantially) surface-wetted by the liquid and entrained in air or an air/liquid mist as an abrasive carrier.
The invention further provides a method of abrasive cleaning and/or cutting in which an abrasive stream comprising a mixture of abrasive particles, air and a liquid is directed under pressure at a surface to be cleaned and/or cut, the abrasive stream including abrasive particles at least partially surface-wetted by the liquid and entrained in air or an air/liquid mist as an abrasive carrier.
It is desirable that the abrasive stream leaves the mixing zone in substantially the form of a fine mist as a propellant entraining the abrasive particles. It is preferred that the mixing is carried out under pressure. The mist and surface-wetted particles may suitably be obtained by the accurate control and metering of proportions of abrasive particles, air and liquid, to achieve reduced resistance to outflow of the abrasive stream, and a greatly enhanced performance.
Given suitable control of ingredients supplied, the required abrasive stream can be achieved without the need for an atomiser (whereby the liquid would enter the mixing zone in atomised form). The word "atomise" in the context of this invention refers to the formation of liquid droplets of sufficient size to wet the abrasive particles.
Without wishing to be bound by theory, it is believed that under suitable conditions, in the present invention the abrasive parti
REFERENCES:
patent: 2371434 (1945-03-01), Eppler
patent: 3323257 (1967-06-01), Fonti
patent: 4209952 (1980-07-01), Odds
patent: 4545317 (1985-10-01), Richter et al.
patent: 4802312 (1989-02-01), Glaeser et al.
Cleaning Technology Limited
Rachuba M.
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