The Abrasiive Blast Cleaning is the cleaning of the surface by the action of granular abrasives propelled either by compressed air through a nozzle or by using a vaned hardened steel blast wheel.Abrasive Blast Cleaning provides a method of surface preparation that is rapid and well established. Blast cleaning in its purest sense,relies primarily on mechanical forces(rather then chemical) to achieve cleaning performance.To blast clean,some form of media needs to be directed and ?blasted? via some method of delivery,towards a surface.The mechanisms of delivery and types of medis are wide and diverse and the possible combinations are many.With this versatility,blast cleaning,if specified properly,can be used to clean in many applications. There are several methods and equipment options available for delivering blast medis -- again,these depends on the application.Different applications require different media - and there are many media choices from which to select.Blast Cleaning is line-of-sight in nature.As such,only those surface that can be impacted by the blast spray may be effectively cleaned. In this seminars,we discuss the physical properties of metallic and non-metaalic blasr-cleaning abrasives and describes their versatility in producing various degrees of finish and cleanliness on metal surface.Also reviewed are types of metallic abrasives and an analysis of blast-cleaning with these abrasives.
An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away. While finishing a material often means polishing it to gain a smooth, reflective surface it can also involve roughening as in satin, matte or beaded finishes.
Abrasives are extremely commonplace and are used very extensively in a wide variety of industrial, domestic, and technological applications. This gives rise to a large variation in the physical and chemical composition of abrasives as well as the shape of the abrasive. Common uses for abrasives include grinding, polishing, buffing, honing, cutting, drilling, sharpening, and sanding (see abrasive machining). (For simplicity, "mineral" in this article will be used loosely to refer to both minerals and mineral-like substances whether man-made or not.)
Files act by abrasion but are not classed as abrasives as they are a shaped bar of metal. However, diamond files are a form of coated abrasive (as they are metal rods coated with diamond powder).
Abrasives give rise to a form of wound called an abrasion or even an excoriation. Abrasions may arise following strong contract with surfaces made things such as concrete, stone, wood, carpet, and roads, though these surfaces are not intended for use as abrasives.
Mechanics of abrasion
Abrasives generally rely upon a difference in hardness between the abrasive and the material being worked upon, the abrasive being the harder of the two substances. However, this is not necessary as any two solid materials that repeatedly rub against each other will tend to wear each other away (such as softer shoe soles wearing away wooden or stone steps over decades or centuries or glaciers abrading stone valleys).
Typically, materials used as abrasives are either hard minerals (rated at 7 or above on Mohs scale of mineral hardness) or are synthetic stones, some of which may be chemically and physically identical to naturally occurring minerals but which cannot be called minerals as they did not arise naturally. (While useful for comparative purposes, the Mohs scale is of limited value to materials engineers as it is an arbitrary, ordinal, irregular scale.) Diamond, a common abrasive, for instance occurs both naturally and is industrially produced , as is corundum which occurs naturally but which is nowadays more commonly manufactured from bauxite. However, even softer minerals like calcium carbonate are used as abrasives, such as "polishing agents" in toothpaste.