Grit Sand Blasting Equipment Review

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Grit Sand Blasting Equipment Review

Manufacturing Processes & Engineering

Grit or sand blasting equipment is utilized to clean and prepare surfaces by directing a medium to high pressure stream of abrasive particles against the component surface. Specialized micro-blast or micro-jet machines are available for selective surface preparation applications, material removal and finishing. Grit or sand blasting provides a surface suitable for subsequent coating operations such as thermal spraying, painting or plating. Stationary and portable grit- sand blasting machines are readily available throughout the market place.

Portable or mobile blast equipment can be powered by a generator, diesel or gas 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 sand or grit 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 light weight and more mobile

In wet blasting, the abrasive is introduced into a pressurized stream of water or other liquid, creating slurry. Wet blasting is often used in applications where the minimal dust generation is desired. Portable applications may or may not recycle the abrasive.

Sand Grit Blast Cabinet

Blast Cabinet:

A blast cabinet is essentially a closed loop system that allows the operator to blast the part surface and recycle the abrasive. 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.

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 cleans the abrasive prior to recycling.

Safety:

Cleaning operations using sand or grit abrasive blasting can present risks for workers' health and safety, specifically in portable air blasting or blast room (booth) applications. Although many abrasives used in blasting rooms are not hazardous in themselves, (steel shot and grit, cast iron, aluminum oxide, garnet, plastic abrasive and glass bead), other abrasives (silica sand, copper slag, nickel slag, and staurolite) have varying degrees of hazard (typically free silica or heavy metals). However, in all cases their use can present serious danger to operators, such as burns due to projections (with skin or eye lesions), falls due to walking on round shots scattered on the ground, exposure to hazardous dusts, heat exhaustion, creation of an explosive atmosphere, and exposure to excessive noise. Blasting rooms and portable blaster's equipment have been adapted to these dangers.

Positive pressure blast hood or helmet - The hood or helmet includes a head suspension system to allow the device to move with the operator's head, a view window with replaceable lens or lens protection and an air feed hose. Grade D air supply (or self contained oil-less air pump) - The air feed hose is typically attached to a grade D pressurized air supply. Grade D air is mandated by OSHA to protect the worker from hazardous gases. It includes a pressure regulator, air filtration and a carbon monoxide monitor/alarm. An alternative method is a self contained oil-less air pump to feed pressurized air to the blast hood/helmet. An oil-less air pump does not require an air filter or carbon monoxide monitor/alarm, because the pressurized air is coming from a source that cannot generate carbon monoxide.

Hearing loss prevention:

Ear muffs or ear plugs are recommended.

Operator Body Protection:

Operation body protection varies by application but usually consists of gloves and overalls or a leather coat and chaps. Professionals would wear a cordura/canvas blast suit (unless blasting with steel abrasives, then they would use a leather suit).

In the past, when sandblasting was performed as an open-air job, the worker was exposed to risk of injury from the flying material and lung damage from inhaling the dust. The silica dust produced in the sandblasting process would cause silicosis after sustained inhalation of the dust. In 1918, the first sandblasting enclosure was built, which protected the worker with a viewing screen, revolved around the work piece, and used an exhaust fan to draw dust away from the worker's face.