ABRASIVE BLASTING TERMINOLOGY
Abrasive (also called MEDIA)– Any natural, by-product or manufactured substance, material or residue in granular form that will clean, cur, abrade, gouge or can otherwise change the appearance or condition of a surface when propelled at any speed by compressed air, water, steam, centrifugal wheels/paddles or any other means.
Abrasive Blasting (also called MEDIA BLASTING) – To clean, improve, and / or change the condition or appearance of any object by propelling abrasive / media particles against it by any controlled means.
After Cooler – A device which can be used to remove moisture from compressed air.
Air Compressor – A device which intakes atmospheric air and by using a piston or rotating screw, “forces” that air into a smaller space thereby increasing the pressure of that air when discharged.
Anchor Pattern (also called PROFILE or ETCH) – An automatic result of abrasive striking a surface during a blast cleaning operation. It is the roughness or etch produced and is measured in MILS from the bottom of the lowest valley to the top of the highest peak.
Angle of Approach – The angle, at which, a blast nozzle is held to the surface being cleaned.
Automated Blast Cleaning – A system where one or more blast nozzles, or blast guns, are held in stationary or moveable fixtures inside a blast cabinet. The items being cleaned are then automatically blast cleaned as they move into and / or rotated into the blast streams for programmed time intervals.
Black Beauty (coal slag) – A black boiler slag abrasive with the following advantages: low moisture content, high degree of etch for permanent bonding of coatings, inert, fast cutting due to sharp angular edges and hardness.
Blast Cabinet – An enclosed blast cleaning area where the product is contained inside, but theoperator controls the blast nozzle or suction gun from the outside through arm holes in the front of the cabinet. The operator’s hands and arms are protected by gloves and gauntlets.
Blast Hood – A protective covering for the head and neck. Protects the blast operator from ricochet of abrasives generated by a blast cleaning action.
Blast Nozzle – The actual tool attached to the exit end of a blast hose, which delivers compressed air and abrasives / media onto the item or surface being cleaned. The shape, orifice size, length and lining material can affect the abrasive velocity, pattern, and the actual amount of abrasive being used.
Blast Operator – The person who controls and directs the air / abrasive stream for abrasive blasting.
Blast Room – A blast cleaning enclosure, where blast cleaning is performed under controlled conditions with the operator(s) inside the enclosure.
Blow Down – The complete removal, with the aid of a high pressure compressed air stream, of all loose dust, rust, mill scale, used abrasives and any other residues off a blast cleaned surface prior to the application of any protective coating.
Centrifugal Wheel Blast Cleaning – A surface preparation process where metal shot and/or grit is propelled at very high speed by one or more specially designed wheels onto the workpiece(s). The work piece(s) pass through or are contained in enclosures to contain the abrasive and to provide for control of dust.
Choke Valve – An air valve located in the “pusher air line” of a direct pressure blast machine. This valve is most often used to clear the machine of minor amounts od damp abrasive or small obstructions by closing and opening repeatedly. It should always be in the full open position during normal operations. Also used to isolate an outlet on multi-outlet blast machines.
Closed Circuit Blast Cleaning – Specially designed blast cleaning equipment, using either direct pressure or the suction method, where abrasive and compressed air are contained in special housings, which are held in contact with the workpiece. Spent abrasive and compressed air are returned to collection and dust control units by vacuum.
Closed Top Blast Machines – A style of direct pressure blast machines which use a dome shaped top and are usually filled through a screened funnel/sealing cap arrangement. The capacity of this type of machine can be from less than 1 to 160+ cubic feet for portable units, up to 800 cubic feet for stationary models.
Embedment – All or part of an abrasive grain which becomes attached to the surface of product being blast cleaned and cannot be removed by usual clean-up procedures. Embedment could cause an extremely high “peak” (10 or more MILS), above the normal surface which usually will not be covered with a protective coating and can lead to early coating failure.
Equal Pressure – A term denoting that the compressed air pressure inside a direct pressure blast machine is equal to the air pressure passing through the pusher air line that connects to the outlet of the abrasive metering valve. Thus, the abrasive “free flows” into the air stream.
Fan Tip Nozzle – A nozzle which produces a flat, blade like spray pattern.
Industrial Blast Machine – Blast machine that is designed to operate on a production basis for long periods of time.
Inhibitor – A chemical substance which stops or retards the formation of rust on a blast cleaned surface.
Manufactured Abrasive – Any abrasive that is produced by the reduction, formulation, or further processing of minerals or chemicals: i.e. aluminum oxide, silicon carbide, glass beads, plastic grit, iron or steel shot or grit.
Media Blasting (also called ABRASIVE BLASTING) – To clean, improve, and / or change the condition or appearance of any object by propelling abrasive / media particles against it by any controlled means.
Mesh Size (also called Grit Size) – The physical size of any abrasive. Determined by the grains which will remain on various National Bureau of Standards screens. MIL – 1/1000th of an inch (.001). Used by the blasting and painting industry to measure the amount of anchor pattern (profile) produced and the wet or dry thickness of protective coating applied.
MOHS Scale – A measurement of the ability of one mineral to scratch another. Used by the abrasive industry to indicate the hardness of various abrasives to determine their effect on blast cleaning quality.
Multi-Outlet Blast Machine – Any type of blast machine that provides more than one operator outlet.
Open Top Blast Machine – A popular style of direct pressure blast machine which uses a bowl shaped head. Most manufacturers provide an automatic pop-up sealing valve which automatically closes when the machine is pressurized and opens when the machine is shut down, provided the Pressure Release type of Remote Control Deadman Systems are used.
Pressure Blasting – A term indicating that compressed air and abrasive travel through a single hose and under pressure to the blast nozzle. This can produce an impact velocity up to 450 MPH @ 100 PSI blast nozzle pressure. Used where a vigorous action is required.
PSI (Pounds Per Square Inch) – The force produced when air is compressed, commonly referred to as “air pressure” or “blasting pressure”. Most air compressor output is measured in PSI and CFM (Cubic Feet per Minute); that is pressure and volume of air.
Rockwell “C” Scale – A method of measuring the hardness of metallic substances.
Sandblasting – The original term used to describe “Abrasive Blasting” or “Media Blasting” as silica sand was the first abrasive used. The term “Abrasive Blasting” or “Media Blasting” should be used now as there is a wide variety of abrasive medias now available.
Shot – Round balls of manufactured abrasives made of steel, cast iron or glass.
Silica Sand - The first abrasive ever used to do abrasive blasting, hence the term “sandblasting”. The use of silica sand as an abrasive material is HIGHLY discouraged, as exposure to respirable crystalline silica dust causes silicosis, a very serious lung disease.
Silicon Carbide - Silicon carbide, also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive.
Slag Abrasives – A popular by-product type of expendable abrasive obtained from the burning of coal or reduction of copper or nickel. One very popular type of slag abrasives is known as “Black Beauty”.
Soda Blasting – An environmentally friendly form of media/abrasive blasting, which uses a form of sodium bicarbonate (baking soda) as the media. Soda blasting is very gentle to the underlying substrate material being cleaned. It is non-sparking, and the process produces very little heat. As a result, soda blasting will not warp thin metal panels, and will not change dimensional or surface characteristics of metal parts, since it does not remove any of the underlying material. Soda blasting leaves a fresh looking surface on metals, and does not harm chrome, glass, bearings or rubber seals. Also very popular for mold and fire damage cleanup, since it deodorizes the area being cleaned.
Suction Blasting – A term indicating that compressed air and abrasive travel toa blast nozzle through separate hoses. Most often used for low velocity blast cleaning or surface finishing.
Suction Gun – A device most often used in blast cabinets to produce a low velocity blast stream.
Tumble Blast – Where small parts are cleaned in a revolving barrel and subjected to a direct or suction blast stream.
Tungsten Carbide – A hard and durable alloy used as a lining material for blast nozzles.
Venturi – The orifice section of a blast nozzle where compressed air and abrasive are compacted and then allowed to uniformly spread out as they leave the nozzle, resulting in a higher velocity and more uniform blast pattern.