Equipment
Device used for adding sand to the compressed air (top of
which is a sieve for adding the sand)
Portable blast equipment
Mobile dry abrasive blast systems are typically powered by a
diesel air compressor. The air compressor provides a large volume of high
pressure air to a single or multiple "blast pots". Blast pots are
pressurized, tank-like containers, filled with abrasive material, used to allow
an adjustable amount of blasting grit into the main blasting line. The number
of blast pots is dictated by the volume of air the compressor can provide.
Fully equipped blast systems are often found mounted on semi-tractor trailers,
offering high mobility and easy transport from site to site. Others are
hopper-fed types making them lightweight and more mobile.
In wet blasting, the abrasive is introduced into a
pressurized stream of water or other liquid, creating a slurry. Wet blasting is
often used in applications where the minimal dust generation is desired.
Portable applications may or may not recycle the abrasive.
Blast cabinet
A sand-blasting cabinet
A blast cabinet is essentially a closed loop system that
allows the operator to blast the part and recycle the abrasive.[6] It usually
consists of four components; the containment (cabinet), the abrasive blasting
system, the abrasive recycling system and the dust collection. The operator
blasts the parts from the outside of the cabinet by placing his arms in gloves
attached to glove holes on the cabinet, viewing the part through a view window,
turning the blast on and off using a foot pedal or treadle. Automated blast
cabinets are also used to process large quantities of the same component and
may incorporate multiple blast nozzles and a part conveyance system.
There are three systems typically used in a blast cabinet.
Two, siphon and pressure, are dry and one is wet:
A siphon blast system (suction blast system) uses the
compressed air to create vacuum in a chamber (known as the blast gun). The
negative pressure pulls abrasive into the blast gun where the compressed air
directs the abrasive through a blast nozzle. The abrasive mixture travels
through a nozzle that directs the particles toward the surface or workpiece.
Nozzles come in a variety of shapes, sizes, and materials.
Tungsten carbide is the liner material most often used for mineral abrasives.
Silicon carbide and boron carbide nozzles are more wear resistant and are often
used with harder abrasives such as aluminum oxide. Inexpensive abrasive
blasting systems and smaller cabinets use ceramic nozzles.
In a pressure blast system, the abrasive is stored in the
pressure vessel then sealed. The vessel is pressurized to the same pressure as
the blast hose attached to the bottom of the pressure vessel. The abrasive is
metered into the blast hose and conveyed by the compressed gas through the
blast nozzle.
Wet blast cabinets use a system that injects the
abrasive/liquid slurry into a compressed gas stream. Wet blasting is typically
used when the heat produced by friction in dry blasting would damage the part.
Blast room
A blast room is a much larger version of a blast cabinet.
Blast operators work inside the room to roughen, smooth, or clean surfaces of
an item depending on the needs of the finished product. Blast rooms and blast
facilities come in many sizes, some of which are big enough to accommodate very
large or uniquely shaped objects like rail cars, commercial and military
vehicles, construction equipment, and aircraft.[7]
Each application may require the use of many different
pieces of equipment, however, there are several key components that can be
found in a typical blast room:
An enclosure or containment system, usually the room itself,
designed to remain sealed to prevent blast media from escaping
A blasting system; wheel blasting and air blasting systems
are commonly used
A blast pot — a pressurized container filled with abrasive
blasting media[8]
A dust collection system which filters the air in the room
and prevents particulate matter from escaping
A material recycling or media reclamation system to collect
abrasive blasting media so it can be used again; these can be automated
mechanical or pneumatic systems installed in the floor of the blast room, or
the blast media can be collected manually by sweeping or shoveling the material
back into the blast pot
Additional equipment can be added for convenience and
improved usability, such as overhead cranes for maneuvering the workpiece,
wall-mounted units with multiple axes that allow the operator to reach all
sides of the workpiece, and sound-dampening materials used to reduce noise
levels.[9]
Media
In the early 1900s, it was assumed that sharp-edged grains
provided the best performance, but this was later demonstrated not to be
correct.[10]
Mineral: Silica sand can be used as a type of mineral
abrasive. It tends to break up quickly, creating large quantities of dust,
exposing the operator to the potential development of silicosis, a debilitating
lung disease. To counter this hazard, silica sand for blasting is often coated
with resins to control the dust. Using silica as an abrasive is not allowed in
Germany, United Kingdom, Sweden, or Belgium for this reason.[11] Silica is a
common abrasive in countries where it is not banned.[12]
Another common mineral abrasive is garnet. Garnet is more
expensive than silica sand, but if used correctly, will offer equivalent
production rates while producing less dust and no safety hazards from ingesting
the dust. Magnesium sulphate, or kieserite, is often used as an alternative to
baking soda.
Agricultural: Typically, crushed nut shells or fruit
kernels. These soft abrasives are used to avoid damaging the underlying
material such when cleaning brick or stone, removing graffiti, or the removal
of coatings from printed circuit boards being repaired.
Synthetic: This category includes corn starch, wheat starch,
sodium bicarbonate, and dry ice. These "soft" abrasives are also used
to avoid damaging the underlying material such when cleaning brick or stone,
removing graffiti, or the removal of coatings from printed circuit boards being
repaired. Sodablasting uses baking soda (sodium bicarbonate) which is extremely
friable, the micro fragmentation on impact exploding away surface materials
without damage to the substrate.
Additional synthetic abrasives include process byproducts
(e.g., copper slag, nickel slag, and coal slag), engineered abrasives (e.g.,
aluminum oxide, silicon carbide or carborundum, glass beads, ceramic
shot/grit), and recycled products (e.g., plastic abrasive, glass grit).
Metallic: Steel shot, steel grit, stainless steel shot, cut
wire, copper shot, aluminum shot, zinc shot.
Many coarser media used in sandblasting often result in
energy being given off as sparks or light on impact. The colours and size of
the spark or glow varies significantly, with heavy bright orange sparks from
steel shot blasting, to a faint blue glow (often invisible in sunlight or
brightly lit work areas) from garnet abrasive.
Reference
https://en.wikipedia.org/wiki/Abrasive_blasting#Equipment