19-01-2013, 10:41 AM
ABRASIVE BLAST CLEANING
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ABSTRACT
Abrasive blasting is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface, or remove surface contaminants. A pressurized fluid, typically air, or a centrifugal wheel is used to propel the media. The first abrasive blasting process was patented by Benjamin Chew on 18 October 1870
Abrasive blasting is defined as an operation in which materials are cleaned by the abrasive action of any metal shot or mineral particulate propelled within a gas or liquid. It is a ‘prescribed activity of environmental significance’ under Schedule 1 of the Environment Protection Act 1993 (the Act); these activities require a licence under the Act. Abrasive blasting using totally enclosed automatic blast cleaning units, or those of less than five cubic metres in volume, is not included as a prescribed activity in Schedule
It is important to ensure that all practicable steps are taken to minimise the adverse effect that the noise emissions may have on the amenity value of an area. This responsibility includes not only the noise emitted from the blast equipment and generators but also associated noise sources, such as radios.
INTRODUCTION:
• What is Abrasive ?
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.)
Manufactured abrasives
Abrasives are shaped for various purposes. Natural abrasives are often sold as dressed stones, usually in the from of a rectangular block. Both natural and synthetic abrasives are commonly available in a wide variety of shapes, often coming as bonded or coated abrasives, including blocks, belts, discs, wheels, sheets, rods and loose grains.
Bonded abrasives
ABRASIVE BLAST CLEANING:
Abrasive blasting or air blasting is a method of propelling abrasive using a compressed gas (typically air) or pressurized liquid (typically water) as the propellant. There are numerous generic terms for this application usually related to the abrasive media in use; common terms include sand blasting, shot blasting, grit blasting, bead blasting and blast cleaning.
The process of abrasive blasting began in 1904. It is used today to:Abrasive blasting can be defined as a process of cleaning fu~dfinishing ofmaterials by forceful direction of an abrasive media applied either dry orsuspended in a liquid medium, against the surface of the workpiece.
Abrasive blasting operations applies abrasive material forcibly to a surface using pneumatic pressure, hydraulic pressure or centrifugal force. In addition to exposure to the impact of rebounding material, hazards related to abrasive blasting include the toxicity of the abrasive material and the surface being abraded.
This guide will review the Oregon OSHA code OAR Division 2 Subdivision G Occupational Health & Environmental Control 1910.94 (a) Abrasive blasting, as well as provide additional safety information to guide you in safe abrasive blasting operations.
Blast room
A blast room is a larger version of a blast cabinet and the blast operator works inside the room. A blast room includes three of the four components of a blast cabinet: the containment structure, the abrasive blasting system and the dust collector. Most blast rooms have recycling systems ranging from manual sweeping and shoveling the abrasive back into the blast pot to full reclaim floors that convey the abrasive pneumatically or mechanically to a device that t normal temperatures. Typically Hydrogen and Oxygen are used .
CONCLUSION:
Abrasive blasting is an amazing technology that is gaining popularity very quickly. The advantages of abrasive blasting far surpass disadvantages.The crushed glass can be reused up to 5 times before the grain size reduces below that whichno longer gives the surface roughness required by NG. Disposal of the waste products, whichis not considered as a hazardous waste, are easier to manage and provides reduced cost tooperations