We discuss the history of abrasive blasting, what types there are, and provide an overview of the abrasive materials used as blast media.
There are several reasons why abrasive blasting would be used, commonly these are for:
There are a number of methods of abrasive blasting, each providing a different outcome and requiring the use of varying blasting materials or “blasting media”.
The type of blasting media used is dependent on the workpiece material and desired effect. Blasting media comes in a range of different densities, materials, hardness, particle sizes and shapes. These all need to be considered in order for the desired effect to be achieved.
Abrasive blasting is typically done by using a centrifugally powered wheel to propel the media at the surface of the workpiece. Alternatively, you can use compressed air, which is the method typically used for ADS Laser Cutting. It can also be done by using a high-pressure water jet with high velocity.
Modern abrasive blast cleaning is used in a variety of industries such as oil and gas, steel fabrication, marine shipbuilding, construction and automobile.
Abrasive corrosion theoretically has been around since the Earth was formed. In the deserts, sandstorms are a naturally occurring event, with these high-speed winds carrying sand and other particles capable of altering the surface of an object.
Abrasive blasting began with Benjamin Tilgham, who patented the first shot-blasting machine in 1870. This was used to clean up painted and/or rusted surfaces. Thomas Pangborn developed this further in 1904, to include compressed air with the blast alongside deep cleaning of metal materials through the use of sandblasting.
A problem with sandblasting during the early 1900’s, was the serious health implications as a result of high-risk exposure to silica dust.
Water was originally introduced into abrasive blasting in the early 1950s, once silica sand had been banned in sandblasting.
This ban was introduced due to the discovery of silica fractures upon impact, becoming respirable posing a high risk of Silicosis and other respiratory diseases to the operator.
There is a wide range of terms used in abrasive blasting, including:
The three most common methods of abrasive blasting are Sand Blasting, Shot Blasting and Wet Blasting.
Sandblasting when used in sheet metal fabrication, is the process of firing a blast media at high velocity. Typically out of an air-powered pressure gun (known as Air Blasting), towards a metal surface. This is done with two hoses; one of which compressed air passes through, creating pressure. This pressure then pulls media from a tank through the second hose, before expelling both the air and sand together out of the gun. Sandblasting can be used to remove paint, and residues from oxidation, rust, scratches, and casting marks and is widely used for cleaning a surface before applying a finish, such as powder coating.
Shot blasting fires abrasive media like tiny pieces of metal (known as steel shot and steel grit) against a surface to remove impurities as well as clean it. Used to polish or strengthen (known as peen) metal it is also often used as a method of preparing a workpiece for metal finishing.
This method can be done by pneumatically accelerating the blast media towards the surface using compressed air inside of a blast cabinet (Air Blasting). It is also often done using Wheel Blasting, which instead of being propelled by compressed air, the media essentially ‘throws’ the shot or grit at the workpiece via a centrifugally powered rotating wheel.
Wet blasting is used to remove coatings, residues, corrosion and contaminants from hard surfaces. It is similar to sandblasting only the blast media is dampened prior to blasting.
Hot water and soap can be used at the same time as fine media such as plastic or steel, meaning an operator can simultaneously degrease the surface while blasting.
Methods include attaching either a Water Injection Nozzle (WIN) or Halo nozzle to a sandblaster which dampens the abrasive as it leaves the nozzle. By using cabinets or blast rooms, and modifying sandblasters to store water and abrasives in a tank prior to them being drawn through.
Using the Venturi Effect and with Vapor Abrasive Blasters the water and abrasive are stored in a tank before being pushed into the airflow.
Abrasive materials can be either organic, plastic, metal, silicate, or stone. Each material type performs a particular task well due to a number of its key abrasive properties, which include a mix of its hardness, shape, particle size and density.
Common abrasive materials include:
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