TYPE OF SAND BLASTING
Sandblasting
Sand blasting is also known as abrasive blasting, which is a
generic term for the process of smoothing, shaping and cleaning a hard surface
by forcing solid particles across that surface at high speeds; the effect is
similar to that of using sandpaper, but provides a more even finish with no
problems at corners or crannies. Sandblasting can occur naturally, usually as a
result of particles blown by wind causing aeolian erosion, or artificially,
using compressed air. An artificial sandblasting process was patented by
Benjamin Chew Tilghman on 18 October 1870.
Sandblasting equipment typically consists of a chamber in
which sand and air are mixed. The mixture travels through a hand-held nozzle to
direct the particles toward the surface or work piece. Nozzles come in a
variety of shapes, sizes, and materials. Boron carbide is a popular material
for nozzles because it resists abrasive wear well.
Wet abrasive blasting
One of the original pioneers of the wet abrasive
(vapourmatting) process was Norman Ashworth who found the advantages of using a
wet process a strong alternative to dry blasting. The process is available in
all conventional formats including hand cabinets, walk-in booths, automated
production machinery and total loss portable blasting units. Advantages include
the ability to use extremely fine or coarse media with densities ranging from
plastic to steel and the ability to use hot water and soap to allow
simultaneous degreasing and blasting. The reduction in dust also makes it safer
to use silicacious materials for blasting, or to remove hazardous material such
as asbestos, radioactive or poisonous products.
Process speeds are generally not as fast as conventional dry
abrasive blasting when using the equivalent size and type of media, in part
because the presence of water between the media and the substrate being
processed creates a lubricating cushion that can protect both the surface and
the media, reducing breakdown rates. Reduced impregnation of blasting material
into the surface, dust reduction and the elimination of static cling can result
in a very clean surface. However wet blasting of mild steel will result in
immediate or 'flash' corrosion of the blasted steel substrate due to the
presence of water. The lack of surface recontamination also allows the use of
single equipment for multiple blasting operations—e.g., stainless steel and
mild steel items can be processed in the same equipment with the same media
without problems.
Bead blasting
Bead blasting paint from a concrete curb. Mixing particles
with water substantially reduces dust.
Bead blasting is the process of removing surface deposits by
applying fine glass beads at a high pressure without damaging the surface. It
is used to clean calcium deposits from pool tiles or any other surfaces, remove
embedded fungus, and brighten grout color. It is also used in auto body work to
remove paint. In removing paint for auto body work, bead blasting is preferred
over sand blasting, as sand blasting tends to create a greater surface profile
than bead blasting. Bead blasting is often used in creating a uniform surface
finish on machined parts.[3] It is additionally used in cleaning
mineral specimens, most of which have a Mohs hardness of 7
or less and would thus be damaged by sand.
Wheel blasting
In wheel blasting, a spinning wheel propels the abrasive
against an object. It is typically categorized as an airless blasting operation
because there is no propellant (gas or liquid) used. A wheel machine is a
high-power, high-efficiency blasting operation with recyclable abrasive
(typically steel or stainless steel shot, cut wire, grit, or similarly sized
pellets). Specialized wheel blast machines propel plastic abrasive in a
cryogenic chamber, and is usually used for deflashing plastic and rubber
components. The size of the wheel blast machine, and the number and power of
the wheels vary considerably depending on the parts to be blasted as well as on
the expected result and efficiency. The first blast wheel was patented by
Wheelabrator in 1932.[4]
Hydro-blasting
Hydro blasting is not a form of abrasive blasting as no
abrasive media is used. Hydro-blasting, commonly known as water blasting, is
commonly used because it usually requires only one operator. In hydro-blasting,
a highly pressured stream of water is used to remove old paint, chemicals, or
buildup without damaging the original surface. This method is ideal for
cleaning internal and external surfaces because the operator is generally able
to send the stream of water into places that are difficult to reach using other
methods. Another benefit of hydro-blasting is the ability to recapture and
reuse the water, reducing waste and mitigating environmental impact.
Micro-abrasive blasting
Main article: Abrasive jet machining
Micro-abrasive blasting is dry abrasive blasting process
that uses small nozzles (typically 0.25 mm to 1.5
mm diameter) to deliver a fine stream of abrasive accurately to a small part or
a small area on a larger part. Generally the area to be blasted is from about 1
mm2 to only a few cm2 at most. Also known as
pencil blasting, the fine jet of abrasive is accurate enough to write directly
on glass and delicate enough to cut a pattern in an eggshell.[5] The
abrasive media particle sizes range from 10 micrometres up to about 150
micrometres. Higher pressures are often required.
The most common micro-abrasive blasting systems are
commercial bench-mounted units consisting of a power supply and mixer, exhaust
hood, nozzle, and gas supply. The nozzle can be hand-held or fixture mounted
for automatic operation. Either the nozzle or part can be moved in automatic
operation.
Automated blasting
Automated blasting is simply the automation of the abrasive
blasting process. Automated blasting is frequently just a step in a larger
automated procedure, usually involving other surface treatments such as
preparation and coating applications. Care is often needed to isolate the
blasting chamber from mechanical components that may be subject to dust
fouling.
Dry-ice blasting
Main article: Dry-ice blasting
In this type of blasting, air and dry ice are used. Surface
contaminants are dislodged by the force of frozen carbon dioxide particles
hitting at high velocity, and by slight shrinkage due to freezing which
disrupts adhesion bonds. The dry ice sublimates, leaving no residue to clean up
other than the removed material. Dry ice is a relatively soft material, so is
less destructive to the underlying material than sandblasting.
Bristle blasting
Main article: Bristle blasting
Bristle blasting, unlike other blasting methods, does not
require a separate blast media. The surface is treated by a brush-like rotary
tool made of dynamically tuned high-carbon steel wire bristles. Repeated
contact with the sharp, rotating bristle tips results in localized impact,
rebound, and crater formation, which simultaneously cleans and coarsens the
surface.
Vacuum blasting
Main article: Vacuum blasting
Vacuum blasting is a method that generates very little dust
and spill, as the blast tool does dry abrasive blasting and collects used blast
media and loosened particles from the surface to be treated, simultaneously.
Blast media consumption is relatively low with this method, as the used blast
media is automatically separated from dust and loosened particles, and reused
several times.
Reference
https://en.wikipedia.org/wiki/Abrasive_blasting