This article provides comprehensive information about abrasive blasting and sandblasting machinery. You will learn how these sandblasters are made and their materials of construction as well as applications, advantages, and drawbacks.
Read further to answer questions like:
Sandblasting equipment includes systems or machinery, and components for projecting blast media against a part‘s surface to abrade, clean, or modify the surface. Sand, abrasive, metal shot, and other blast media are driven or propelled using pressurized water, compressed air, or a blast wheel.
Sandblasting equipment includes a wide variety of individual types such as:
If you want an answer to the question "how do sandblasters work?", then you first need a better understanding of the technology empowering blast equipment.
The technology employed to energize or propel the blast media is an important aspect characterizing sandblasting equipment types. Blast machines use either pneumatic or air pressure or wheel to project abrasives or media.
The pneumatic propulsion technologies blast machinery employs to clean, peen, or modify surfaces include:
Air or Dry Blast Equipment – Air abrasive blasting or dry blast equipment utilize compressed air to move the blast media. Pneumatic or compressed air blast systems can be divided into two types, suction, and direct pressure.
Suction or Siphon Blast Equipment – Suction blasters or blast cabinets employ the venturi siphon effect to such abrasive into a pressurized stream of fluid, air, or water.
Venturi devices utilize a constriction in a moving stream of fluid to generate a pressure differential or vacuum. Blast media is sucked into the air or water stream at the constriction.
Venturi devices are found in many industries. Venturi generators are used to create a vacuum for mechanical holding applications. Ejectors and eductors move fluids, powder, or solids in chemical process industries.
Suction blast cabinets or portable siphon blasting pots cost less than pressure blast systems. Economy blasters tend to be suction sandblasters. They do not require a pressure vessel and consume only half of the pressurized air compared to pressure blast cabinets. However, suction blasters require higher air pressure levels to maintain media flow.
Suction blast cabinets are less aggressive and take longer to impact clean. Suction blasters are commonly used in short-run or light production, maintenance, and remote field applications.
The less aggressive nature of suction or siphon blasters increases the time to strip or clean parts. On the upside, the lower aggressiveness reduces the wear rate of the parts within a suction blaster. Suction blasters tend to last longer, which reduces blast equipment maintenance costs.
Small handheld sandblasters can have a cup above the blast gun to gravity feed into a blast gun‘s venturi point. Gravity blasters are a type of suction blaster because gravity-fed blast guns still make use of the venturi siphon effect.
Have you ever wondered why direct pressure blasters are found more often in industrial applications than suction blasters?
Direct Pressure or Pressure Blast Equipment – Pressure or direct pressure abrasive blast equipment makes use of a pressure vessel to energize the abrasive media. A pop-up or metering valve on the pressure vessel is opened to release pressurized fluid and blast media into a blast hose. The pressurized media travels through the blast hose to the direct pressure cabinet and blast gun.
Direct pressure cabinet blast machines expel the blast media at much higher flow rates or speeds compared to suction blast equipment. Impact or kinetic energy (K) of the blast media is K = ½ mv2 where m = blast media mass and v = velocity. Doubling the flow or velocity quadruples the impact energy and blast cleaning efficiency.
The higher blast media speeds enable direct pressure systems to impact clean parts up to 4 times faster than suction blast machines. Pressure levels are more adjustable with direct pressure blast cabinets, so cleaning and surface modification can be more precisely controlled.
Direct pressure blast equipment can lift and propel heavy media such as steel shot, cut wire shot, and steel grit. Suction sandblasters struggle with heavy media. Doubling the blast media mass doubles the impact energy. Heavier blast media (denser or larger) is more efficient at cleaning and profiling compared to lighter, lower density, or smaller media.
A higher density or larger diameter as well wider diameter nozzle or multiple nozzles will blast parts with more mass and higher energy impacts. Air compressors with greater flow capacity (CFM) are required to drive the higher mass through the blast system.
The higher speeds, ability to handle heavy steel media, more aggressive nature and better control of direct pressure sandblasting equipment make pressure blast equipment more widely employed in high volume production and automated blasting applications. The higher blast media speeds enable pressure sandblaster guns to operate at greater stand-off distances from the part.
Pressure blasters consume two to three times the volume (CFM) of compressed air compared to suction blast equipment.
Pressure vessel maintenance and safety are a concern. The failure of a pressure vessel could harm operators and damage equipment. Blast system pressure vessels need to be manufactured to American Society Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Codes.
Wet Abrasive Blast Equipment – Water can replace air as the fluid used to propel the blast media. Wet abrasive blast or water blasting can reduce the dust generated during abrasive blasting by over 90%, which can be important when stripping or cleaning a part containing heavy metals and hazardous materials.
An aspect I find interesting about water blast equipment is the ability to provide additional surface modification with water additives. Chemicals can be added to break down hard to remove films or grease. Anti-rust agents can be added, so the parts will be protected until coatings are applied.
While some suppliers refer to wet abrasive blasters as dustless blast equipment, no abrasive blasting system suppresses 100% of the dust generated.
Water blasting can keep the parts cooler compared to dry blasting, which can reduce warping or distortion of thin sections. If the dust generated during blasting is explosive such as aluminum or titanium dust, then wet blasting is advantageous because static discharges and ignition are suppressed.
Water blasting can consume up to 50% less blast media compared to dry blasting. Wet blasting provides deep cleaning with less or no imbedment of abrasive media. Wet blasting systems can employ closed-loop media can recyclers, oil separators, demisters, and filtration systems. Dust is converted to clean, disposable sludge waste.
In dry blasting, the dust must be removed from parts with an air blow gun or washing. In factory settings, dry blasters require dust collectors.
Wet blasting combines washing and dedusting with the blasting step. Detergents can be added to the water to loosen deposits, dissolve oils or greases and accelerate the cleaning process.
Rust inhibiting agents can be added to the water to prevent rusting of wet steel after the blasting process is complete. If rust suppressors are not added to the water, then the steel should be dried, oiled, or painted immediately after blasting to prevent rust formation.
Bacteria and microbes can grow in the blast water forming slime films and releasing odors. The blast water like other metalworking fluids and grinding coolants require the addition of antimicrobial agents.
There are several types of water blasters and water abrasive blasters.
Slurry Blasting Equipment – Dry blasting equipment can be retrofitted to provide wet blasting. Slurry blast systems are also known as air abrasive water blasters. A water injection nozzle or water ring (halo) is attached to an air blasting gun, which introduces water into the blast media stream. They suppress 50% to 85% of the dust generated.
The water ring or halo nozzles provide less dust control than the water induction or injection nozzles.
Slurry blasters have a high degree of versatility because they can dry blast, wet blast, rinse, and dry parts. One drawback of slurry blasters is cleaning up the muddy mess generated in field applications. Slurry blast equipment is tiresome for operators to carry and handle because a heavy water hose is attached.
The water blast technology that I find the most interesting is vapor abrasive blasting.
Wet Venturi Blasters – Wet venturi blasters are like dry suction blasters, except compressed air generated venturi vacuum sucks in an abrasive water mixture. Some manufacturers call these systems modified sandblasters. With venturi pot systems, air is used to pressurize the pot to keep it consistent while blasting. While venturi blasters successfully suppress dust, they require high blast pressure to operate effectively resulting in high consumption rates of water and blast media with limited flow control.
Vapor Abrasive Blasting Equipment – Vapor abrasive blasting is known as wet blasting, liquid honing, vapor honing, dustless blasting, and slurry blasting. In the wet blasting process, water is used to remove contaminants from surfaces using pressurized water and an abrasive media. When the abrasive media is mixed with water, it is pressurized in a pressure pot before it is sent through the blast nozzle by compressed air, a process referred to as slurry blasting.
Vapor blasting is a gentler process than dry blasting since the water acts as a cushion for the abrasive. The water, also, dampens the process and contains the particles removed by the abrasive. Additionally, in wet blasting, the impact of the abrasive is cushioned evenly dispersing over the surface in a feather like pattern allowing for a finer blast method.
Vapor sandblasters have a wide operating pressure range and finer control of the wet abrasive blasting process compared to other wet blasters. Vapor abrasive blast machines operate at very low pressures (30 psi) for paint stripping to very high pressures such as white metal blasting for corrosion control applications.
High-Pressure Water Blasters and Hydroblasters – If high-pressure water is employed, blast media is not necessary for some applications. Water blasters are also called aqua cleaners and hydraulic blasters. Media-less or nonabrasive water blasters and water jetters blast clean surfaces with high-pressure water.
High-pressure water blasters operate at pressures of 6000 psi and higher – beyond the range of typical pressure washers. Water blasters can remove paint and light rust, but they cannot remove tightly adherent corrosion, rust, mineral scales, and other deposits.
What I find amazing is the fact that UHP water jetters can cut material without abrasive grits.
Ultrahigh pressure (UHP) hydroblasters or water jetters operate at ultra-high pressure of 30,000 psi or higher. UHP hydroblasters can remove heavy rust layers, thick scale, hard deposits, concrete, and coatings. UHP hydroblaster can even demolish and hydrocut materials such as tanks, pipes, reactors, rebar, manways, and concrete. Pressure vessel and reactor heads can be removed with hydrocutting even in explosive environments without the need for purging.
I would guess that almost every foundry casting pouring large steel or iron castings has a wheel blasting machine in their cleaning room. Read on to find out why!
Wheel Blast Equipment - Another major type of sandblasting or shot blasting equipment is based on centrifugal wheel blast technology. Blast media is fed into the axis of a spinning turbine wheel impeller. A series of throwing blades or paddles on the blast wheel accelerate and fling the shot or abrasive media onto the parts.
Adjustments to the control cage around spinning blades can direct the stream of media to control the blast pattern as well as the size and location of the "hot spot". The blast pattern can be several inches to feet in width depending on the wheel dimensions, wheel speed, and distance between the wheel and part surfaces.
The hot spot is a region of the blasted surface, which becomes hot to the touch. The hot spot tells the operator where the center of the blast flow is located. The hot spot is the most aggressive portion of the blast media stream. In other words, the hot spot has the highest density of impacts per unit area. If the parts are not hot to the touch, then the operator adjusts the blast pattern to move the hot spot onto the parts.
Wheel blasters are ideal for moving heavy blast media like steel shot, stainless steel shot, metal grit, cut wire shot, and cast shot. Aluminum oxide and other angular abrasive media are not typically blasted with wheel blasters. Round steel shot is excellent at cleaning castings, descaling forgings, and shot peening structural components.
The shape and hardness properties of the media, or whether any media is used at all, is another parameter controlling the blasting process. Blast machines are also defined by the blast media type employed:
Abrasive Blasters - Abrasive blasters are the conventional sandblasters designed to impact hard, angular grits against a surface. Blasting abrasives compositions include aluminum oxide, silicon carbide, coal slag, garnet, mineral sands, ilmenite, olivine, pumice, staurolite, crushed glass, abrasive sponge media, micro-abrasives, and copper slag. The blast nozzles, blast hoses, and surfaces in abrasive blasters need greater wear resistance and require more frequent maintenance and replacement.
Non-aggressive Media Blasters – Non-abrasive media includes walnut shells, soda (sodium bicarbonate or baking soda), plastic grit, corn cobs, and starch. Equipment designed for blasting non-abrasive media does not require components with the extreme wear resistance of abrasive blasters. blast nozzles, blast hoses, and internal surfaces should last longer before replacement is required.
What I find very intriguing about shot peening equipment is the ability to alter the strength of parts by orders of magnitude or up to 5 times.
Shot Peening Machines – Peening impacts a surface with spherical steel, stainless steel, glass beads, or ceramic ball media to impart compressive residual surface stresses on a part.
The majority of shot peeners or shot peening machines employ centrifugal wheels or pressure blasting. They are highly effective in projecting shot peening media.
Ice Blasters – Dry ice blasters and water ice blasters impact clean with a frozen media such as dry ice (solid carbon dioxide) or water ice (H2O). Dry ice and water ice are non-aggressive types of media.
Ice blasting equipment must be designed to handle the colder media, as well as the condensation on lines, cabinets, pots, and vessels. The materials of construction cannot include types of plastics or metals, which become brittle at lower temperatures.
Dry ice is gentler and softer than plastic media. Dry ice media can be in two forms: pellet and shaved or snow-like flakes. NASA engineers have used dry ice or carbon dioxide snow-like crystals to clean particle contaminants and molecules from the surface of a space telescope mirror while generating zero scratches or profile changes.
Dry ice and water ice blasters have clean-up advantages over conventional blasters. Water ice grits will evaporate after blasting. Dry ice sublimes in gaseous carbon dioxide. The sublimation of dry ice absorbs heat from the part‘s surface, which can aid in paint removal and cleaning.
Sandblasting equipment can consist of complete blasting machines or abrasive blast packages preconfigured with the required components. Sandblasting equipment can be modular. You can configure a sandblasting system specifically for your application by selecting various parts from a supplier‘s catalog. Parts include blast guns, wear-resistant nozzles, pressure vessels, valves, deadman handles, blast cabinets, blast rooms, and blast hoses.
Sandblasting equipment can vary greatly in size and configuration depending on the specific application, the size of the parts being blasted, the end-use or function, and setting (lab/shop, production line, or field/remote sites) where they are used.
Benchtop Micro Blasters and Pencil Blasters – Microabrasive blasters or micro blasters have small 0.018 to 0.125-inch diameter nozzles. Some nozzles are made of sapphire or single crystal alumina. Media sizes range from 10 to 350 microns are used to blast surfaces. Microblast cabinets are benchtop or floor mounted. Handheld pencil blasters are a type of micro blaster. They usually have a small gravity-fed media cup.
Cleaning, stripping, and etching of small parts and detailed work in dental, jewelry, and electronic (PCBs) applications are common for micro-abrasive blasting systems. Stainless cannula, microtubes, and hypodermic needles are deburred with microblasting systems.
Manual Blast Cabinets or Cabinet Blasters – Manual blast cabinets have two holes with rubber blasting glove protruding into the cabinet, which allow an operator to manipulate parts and hold the blast nozzle at the appropriate stand-off distance to generate a hot spot and then move the hot spot across the surface to clean or etch a surface.
The blast cabinets have a window and internal lighting, so the operator can see the parts and guns without getting blasted in the face. Some blast cabinets blast air across the window to maintain visibility by preventing dust build-up.
Spent blast media drops through the cabinets steel or fiberglass grate and into a collection hopper. The used blast media was conveyed to a media separator to recover the abrasive. Economy blast cabinets might skip the separator step and directly reuse the spent media. Without separation, dust and finer broken media are blasted, which can reduce efficiency and damage filters.
Ideally, the media and dust generated from blasting parts are contained within the cabinet and filtration system. Blast cabinets develop leaks as seals wear and tear over time. Leaking around doors is a common problem because cabinet doors are not always clamped tight around the whole periphery.
One leading manufacturer, Titan Abrasive Systems, has developed a patent-pending technology for "leak or warp" proof blast cabinet doors. The doors have double panels and two rigid, steel channels. The doors also have a better closing mechanism to better clamp the door shut along the edge. A knife-edge on the door forms a positive seal every time the door closes.
Blast cabinets can have front, top and side opening doors. Some cabinets have multiple doors. Double doored cabinets allow shuttling in of a dirty part, while a cleaned part is removed. Blast cabinet doors can swing open, swing up, or slide open.
Pass-through cabinets are available for etching glass sheets or panes and metal plates. Pass-through blast systems come up with a narrow gap with special brush or rubber flap seals to prevent abrasive leaks. The sheet or part is pushed into the gap and passed through the cabinet on rollers.
Manual blast cabinets are ideal for machine shops, garages, body shops, light production or short runs, touch-up of production parts, prototyping, and custom work.
Production blasting machines are built to a higher level of quality and durability to handle the wear and tear found in industrial settings. Production blasting systems are designed for handling larger production run volumes of parts or larger-sized casting, forgings, extrusions, or structural shapes.
They can have multiple blast guns with each prepositioned to blast specific areas on the part. A blasting system with 12 guns will have exceedingly high consumption rates of compressed air and blast media.
Automated vs. Manual – Production sandblasting systems can be manually operated or automated. If your parts vary greatly in size, shape, and production volume, then a manual system for loading or unloading parts might be sufficient. Sandblast system automation is advisable when production quantities are larger or when quality is an issue.
Sandblasting processes can be semi-automatic, fully automatic, or turnkey. In a semi-automatic system, operators might manually load or fixture parts on a table and hanger. Then, the blast chamber door is shut, and the parts rotate and blast with preset or programmed parameters. At the end of the first cycle, the operator might have to flip or reposition the part to complete the blast cleaning of surfaces shadowed during the first cycle. In a turnkey or fully automated blasting system, the part loading, handling, and manipulation, as well as the blasting parameters, are programmed or controlled automatically.
Part handling, as well as gun manipulation, can be automated. Automation can more precisely control gun standoff and travel speed back and forth across the part surfaces. This can result in more consistent cleaning and surface preparation with few or no missed spots requiring touch-ups. The additional cost of automation can be offset by reduced labor cost, higher throughput, few rejects and rework, and increased quality.
Fixed Station and Robotic Blasters – In fixed station and robotic blasting systems, the blast gun or guns are mounted onto the end of a robot arm. The parts are loaded manually or automatically into the blast machine and then the robotic gun nozzle scans and blasts the areas requiring surface treatment.
Robotic blasters are commonly found in aerospace and automotive industries for abrasive blasting and shot peening delicate and complex components such as turbine blades, pump impellers, engine parts, and valve components.
Batch and Pass-through Blast Chambers – Batch production systems include tumble blasters and table blasters. In these systems, batches of parts are placed in the blast machine and processed. In pass-through blast systems, parts are pushed through an opening with special brush or rubber flap seals to prevent abrasive leaks.
Inline and Continuous Blasting Systems – In very high-volume and continuous production applications, blasting machines can be integrated into production lines or placed in-line. Alloy strip, plate, or sheet in a primary or secondary metal mill can be continuously blasted. Inline and continuous blasting system is used for descaling and cleaning steel metal stock (sheet, strip, plate), structural steel (I-beams, channels, angle), pipe and rod (skew rolls).
Large in-line abrasive blasting systems are available for production lines where parts or materials are passed in front of abrasive blasting guns or blast wheels. Production blasting systems have automatic guns or remotely operated blasting guns.
For sandblasting steel or metal sheet or other continuous or semicontinuous stock materials, blasting nozzles or blast wheels are mounted above and below the stock material. The abrasive blasting system continuously cleans the steel or stainless sheet as rollers move it along the mill production line.
The Eco Pickled Surface (EPS) process from TMW uses steel grit blasting as an alternative to acid pickling. The EPS blasted sheet and strip has a more uniform surface profile, better coating adhesion, and improved weldability.
Blast Rooms – Blast rooms can clean part parts too large for blast cabinets, table blasters and hanger blasters. Blast rooms are large enough to accommodate an operator and sometimes even vehicles or material handlers.
Used blast media drops through the grating on the blast room floor. The used media is mechanically or pneumatically conveyed to the reclaimer or separator.
Blast operators don a complete sandblasting suit including a blast sandblasting hood, sandblasting gloves, respirators or air supply, and hearing protection. The surface blasting is accomplished with a portable blasting pot or blasting machine integrated into the blast room.
Blast Booth Lifts – Blast lifts for blast rooms provide an alternative to wearing personal protective equipment (PPE). The operator is enclosed in a protected enclosure with windows. The operator can manipulate the gun and move the entire booth vertically and horizontally across the blast room. Blast booth lifts are useful for impact cleaning tall tanks, structures, ships, and vehicles.
Media Separators and Dust Collectors – Most production blast rooms and blasting systems have media separators to allow recovery or reclamation of used blast media. Recovered media and returned to the blast media pot or bin. Dust and disintegrated media are sent to a dust collector and filtration system, which removes the dust for disposal.
Tumble Blasters - Tumble blasters have a tumbling basket or continuous rubber tumble belt to tumble parts while being blasted. The part must be suited for the tumbling action. Certain parts with thin fins, protrusions, or complex geometries can be damaged during tumbling or get jammed together. A hanger blaster or wire mesh belt blaster for those parts.
The basket should be fully loaded to protect the belt or basket from excessive wear. Overloading the tumble belt or tumble basket is not advised because the surface or part might not see the blasting media. Overload can also damage the tumble belts or baskets.
Table Blasters – Table blast systems are used with blast clean heavy castings and forgings. The parts are mounted on a rotary table inside a blast chamber. The chamber doors are closed and the part blasted while the table rotates inside the chamber.
The bottom of the part sitting on the table is not exposed to blast media. The part has to be flipped over to clean the underside of the part.
Hanger Blast Systems – In hanger blast systems, parts hang down from hooks. Virtually all of the part is exposed to the blast stream or multiple blast streams, so almost every surface can be cleaned.
Wire Mesh Belt Blasters – Wire mesh belts have a wear-resistant manganese steel mesh belt to convey parts past a stream of flowing blast media. The belt should not be blasted without parts. If only a few parts need a surface treatment, then the belt should be loaded with dummy parts or scrap to reduce belt wear.
Monorail Blast System – Monorail blast equipment has an overhead rail. Parts hanging from the monorail enter the blast machine through doors or a pass-through opening. The parts are blasted and then they exit the other end of the machine where the cleaned parts are removed from the monorail.
Roller Conveyor Blast System – Roller conveyors allow heavier metal stock such as billets, thick plates, and structural members (I-beams) to be blast cleaned.
Portable Blasters and Blast Pots – Mobile and portable sandblasting equipment are used in sandblasting large surfaces in the field such as the side of a ship, storage tank, truck, railroad car, bridges, buildings, and farm equipment. Smaller portable sandblasters consist of portable blast pots, air hoses, blast hoses, blast guns, and air compressors. Portable sandblasters can be carried to the site.
Walk-Behind and Vertical Blasters – Walk-behind blasters have a blast wheel to clean concrete floors and an integral vacuum to collect spent media and dust. Vertical blasters are designed for cleaning concrete and brick walls in industrial buildings.
Blasting Trailers and Blasting Trucks - Large mobile sandblasting trailers are towed to worksites. Even larger sandblasting trucks are driven to the remote field sites requiring blasting work. Mobile blasting machines often have engine-driven compressors to provide a compressed air supply.
Internal and Pipeline Blasters – Specialized tools or blasting lance are available for blast cleaning and rust removal on the internal surface of pipes. The tools have collars to center the blast nozzle. The tungsten carbide deflecting tip directs the blast against the inner wall of the pipe.
Spin blast units have rotating heads with several nozzles directed at an angle to the pipe surface.
Sandblasting equipment is constructed from a wide variety of parts cabinets, pressure vessels, hoses, guns, nozzles. These individual components are made using sheet metal fabrication, casting, welding, mechanical fastening, machining, and specialized processes.
Blast cabinets and blast rooms essentially start as fabricated metal boxes. They are typically made by cutting, bending, and forming steel sheets, plates, and structural steel into sides, legs, and doors needed to form a box.
With the addition of blast guns, windows, glove ports, doors, turntables, grating or screen, gun or part holders, pneumatic valves, foot pedals, lights, hoses, and reclamation devices, the box is transformed into a powerful tool of industry: a blast cabinet or blast room.
Blast cabinets parts can be welded or fastened together. Fastening allows the parts to be more easily removed for cleaning, repair, and replacement. Welded blast cabinets tend to be more airtight with less leakage of blast media and dust into the shop, but replacement of worn cabinet sides or bottoms is difficult.
The abrasive blast stream wears the bottom and sides of the cabinet over time. The seals and windows on the cabinet will also age, wear and require replacement.
What are the materials of construction used to make sandblasters?
Blast cabinets and blast rooms for dry or air blasting are made of steel with powder coatings, zinc galvanization, or industrial paint. Wet blasting cabinets are made of more corrosion-resistant materials such as stainless steel.
In certain dry blasting applications such as surgical instruments and medical implants, stainless steel construction materials might be used to avoid iron contamination of a surface.
A system for blasting stainless steel parts would typically use stainless steel shot or grit or nonmetal abrasive media as well. Steel parts or steel shot impacting stainless steel parts can transfer metal to the stainless surface, which can alter passivation and lead to rust on the surface.
Wear-resistant steel liners or wear plates are strategically placed within blast chambers to reduce wear of the blast machine. Wear-resistant alloys include manganese steels such as Manganal and nickel and chromium white cast irons such as Ni-Hard alloys.
What are the Parts and Consumables in a Sandblaster?
Sandblasting equipment tends to be self-destructive due to the aggressive blast media. Blaster parts are consumable and will wear out over time as abrasive or media flow over or through these parts.
Of course, the blast media or abrasive grits are consumable as well. Some types of blast media like steel shot, ceramics, and aluminum oxide can be recycled through the blaster a hundred times or more. Soda, dry ice, sand, and coal slag are only used once.
The parts in abrasive blasters, wheel blasters, and shot peeners need to be regularly inspected for wear. When the nozzle's inner diameter changes or the throwing blades change geometry, the efficiency of the blasting process can be compromised.
Sandblaster parts include:
Blast nozzles are made of extremely wear-resistant materials including:
Boron carbide, alumina, pure WC, and silicon carbide ceramics are amongst the most wear-resistant materials.
Depending on the blast media, cemented tungsten carbide and SiAlON nozzles will last 10 to 20 times longer than ceramic or alumina nozzles. Boron carbide is the hardness and the most wear-resistant of the nozzle materials.
Boron carbide typically costs 3 times as much as cemented WC, but boron carbide lasts 3 to 25 times longer than cemented WC or sialon. They do not have the toughness and impact resistance of cemented tungsten carbide. Binderless tungsten carbide (WC) nozzles have double the life boron carbide nozzles.
Steel nozzles are acceptable for air blow guns, washout guns, and blasting of exceptionally soft media such as soda, dry ice, walnut shells, and plastic media. Steel nozzles will not break when dropped. Economy and non-industrial sandblasters for home or DIY use often come with low-cost steel nozzles.
Based solely on wear resistance boron carbide and binderless WC last up to seven-time longer than cemented WC. If you bang a boron carbide or silicon nitride nozzle into a part, grate, or cabinet wall, then the nozzle is more likely to crack compared to a cement tungsten carbide nozzle.
Nozzle service life will depend on the media blasted through the nozzle as well. Sharper angular steel grit will wear nozzles faster than spherical cast shot. Aluminum oxide and silicon carbide will wear out nozzles more quickly compared to garnet or coal slag. Cleaning equipment blasting plastic media, soda, corn cobs, or walnut shell media could last indefinitely.
In addition to consumables and wear components, a variety of sandblasting accessories and ancillary equipment can improve the blasting process:
Sandblasting and shot peening processes also require abrasive blasting personal protective equipment (PPE) for operators:
Sandblasting equipment modifies surfaces of parts or structures in a variety of ways depending on the media type and blasting parameters. Softer media at lower pressure can gently remove coatings. Extremely hard abrasives projected at high pressures can aggressively etch and pattern or carve surfaces. For example:
Some of the end-use or surface modification functions sandblaster can provide to optimize your production operations are:
Cleaning / Stripping – Impact cleaning or mechanical cleaning is the most widespread end-use of sandblasting equipment. Abrasive blasting is highly effective at cleaning surfaces and stripping or removal of rust, oxide scale, mineral deposits, corrosion grease, dirt, coatings, sealants, carbon deposits, and varnish.
Wire brush wheels, abrasive belts, abrasive discs, and other coated abrasive tend to load quickly when removing paints, coatings, grease, and contaminants. The abrasive blasting process removes from the surface contamination and converts it into dust. The dust and media are handled using dust collectors, industrial vacuums, and separators.
The level of cleaning aggressiveness can be broadly adjusted through the selection of blast media, pressure, flow rates, and blast machine type. Abrasive blasters can gently remove graffiti, paints, and coatings without and removal of the base material.
The abrasive blaster can also deeply blast a steel surface to completely remove any rust, scale, or adherents to a NACE/SSPC "white metal" cleanliness grade.
Blending, Smoothing, and Surface Finishing – Removing marks or way lines from machining and grinding processes. Spherical media such as steel shot and glass beads are especially good at blending and refining surface finishes.
The round edges hammer down higher points on the surface producing a brighter, matte finish. Blasting with sharp, angular abrasive produces a duller, satin finish, which has excellent bonding characteristics.
Refining the surface finish or reducing the surface profile can increase fretting fatigue strength from 20% to 200%. A larger diameter or heavier cast shot can be used first to impart a deep residual stress layer. Next, the surface is peened with small spheres or microbeads to refine the surface finish.
If the part has a rough (high roughness average, Ra) surface finish like an as-cast or as-forged surface, then peening can modestly refine the surface finish. If the part has been ground or machined to a smooth or low Ra finish, then shot peening will result in a rougher surface finish.
Deflashing – Flash or excess material forms where the two halves of a mold meet in plastic molding, rubber molding, sand casting, or die casting. The flash on the molded metal, plastic, or rubber parts needs to be removed and then the remaining parting line blended in.
Plastic and rubber parts are cryogenically frozen with liquid nitrogen at -300°F (-184°C). The plastic and rubber flash becomes friable and is easily blasted away.
Deburring – Slivers, attached swarf or metal chips, and sharp overhanging edges can form on parts during sawing, machining, drilling, cutting, shearing, grinding, and other metal removal operations.
Burrs and slivers can easily cut worker‘s or customer‘s hands and represent a handling hazard. Sandblasting can quickly remove burrs from edges even in recesses where mechanical deburring blades and chamfering tools cannot reach.
Demolition / Cutting -Ultrahigh pressure water blasters or water jetters are used to demolish concrete structures, cut rebar, and open pressure vessels for inspection and repairs. An allied process, abrasive water jet cutting can cut intricate 2D patterns in almost any sheet or plate material without the heat damage from plasma or flame cutting.
Drilling / Carving – Micro abrasive blaster can drill small holes in printed circuit boards. The abrasive blaster can carve glass, wood, stone, and other materials to create 3D shapes and 2D patterns.
Patterning / Marking – Abrasive blasting can create patterns or mark surfaces with images, part numbers, and text. Blasting masking tapes, masking films, and masking compounds are used to create the patterns. The mask materials are typically soft or rubbery, which protects the masked areas from the abrasive blast.
Micro-abrasive blasters have a very narrow blast pattern, so they can selectively pattern, deburr, clean, mark, and drill or cut without masking in some applications. Micro-abrasive blasters can cut slots and holes in a semiconductor wafer or mill channels into ring bearings.
Surface engineering entails modifications to the surface of a part to provide unique characteristics enabling or enhancing performance in specific applications.
Peening impacts the surface with spherical steel, stainless steel, glass, or ceramic media to strain harden and impart compressive residual surface stresses on a part. The common media used is cast steel shot with a Rockwell C hardness of 40 to 55.
The compressive residual stress from shot peening can increase the fatigue strength of parts by 30% to 500%. Increasing fatigue strength and resistance to stress-corrosion cracking is important for fastened components, gears, axles, dies, molds, shafts, springs, aircraft landing gear, and other rotating and structural parts.
Etching / Surface Profiling - Surface texturing, roughening, and generating a specific surface profile. Coating, paints, and adhesives adhere better to a rough surface compared to a smooth surface. An abrasive blasted surface creates an anchor profile with undercuts and more surface area for coatings and adhesives to grab onto.
A sandblast roughened surface on a stainless handrail helps people get a better grip too. Etching alters the frictional characteristics of a surface, which can be useful in mechanical power transmission applications.
Surface Preparation – Surface preparation requires a combination of surface cleaning and anchor profile generation or roughness modification. Surfaces are prepared before coating, painting, galvanizing, oiling, welding, brazing, sealing, soldering, adhesive bonding, and rubber to metal bonding.
Paints, coatings, and adhesives will not bond well to greasy, oily, dusty, or dirty surfaces. Surface contamination can act like a mold release agent or non-stick coating. Cleaning is required to promote chemical bonding and assure adhesion.
Rust and corrosion layers need to be removed as well, especially for protective coatings meeting the National Association of Corrosion Engineers (NACE) and Society of Surface Protective Coating (SSPC) standards. Three reasons to remove rust or corrosion with abrasive blasting are:
NACE, SSPC and ISO 8501 classes, grades, or standards provide visual inspection methods for assessing cleanliness or the degree of the rust, mill scales, and other contaminants on a surface. NACE and SSPC released a joint standard for Industrial Blast Cleaning.
From least cleanliness blast cleaned grade surface (Brush Off) to the highest cleanliness blast cleaned grade (White Metal)
Your surface might be clean, but is it "profiled"?
Paints and coatings will not bond well to a low roughness or smooth surface because there are few anchor points to hold the coating. A blast roughened surface provides mechanical interlocking between the coating and substrate.
Should you surface prep for coating with the coarsest and sharpest blast media available?
No, because if a surface is too rough, then thinner protective coatings might not fully cover the surface resulting in pinholes and corrosion of the underlying surface. Shot, bead, and abrasive blasting can reduce some of the high peaks in a surface profile to improve corrosion protective coating performance.
Aggressive coarse grit abrasive blasting is best for bonding thermal spray deposits, high build coatings, and polymeric lining systems. Thinner coatings and paint perform better with a less aggressive profile (fewer high peaks), which can be produced using round steel shot, glass beads, or other spherical media.
Aerospace – Plastic media is used to remove old paint from aluminum aircraft skins without damaging or removing any of the underlying aluminum metal. Blasting is also used during the refurbishment of jet engine parts and NDT inspection aircraft structural components.
Additive Manufacturing / 3D Printing – Abrasive blasting is used to remove support material from 3D prints. Blasting can also smooth surfaces and blend in striation lines generated during 3D printing.
Agriculture – Sandblasting equipment is used to clean, remove rust and dislodge soil on farming machinery such tillers, tractors, cultivators, harvesting machines, reapers, pickers, and pesticide sprayers.
Automotive OEM – Abrasive blasting equipment is used to etch, clean, and prepare surface automotive parts before welding, adhesive bonding, and painting. Many castings, forgings, and machine components are shot peened to improve material properties and extend life.
Automotive Aftermarket – Sandblasters are important tools in auto body shops and automobile repair garages. They are used for auto body rust removal, body and engine repairs, and antique auto restoration.
Adhesive Bonding / Sealant Application – The surface cleaning and anchor profile generation increase the bond strength of adhesives and sealants.
Architectural / Building & Construction - Sandblasting is used to remove paint and rust on steel, concrete, and wood buildings. Soda blasters are increasingly chosen for architectural cleaning applications such as graffiti removal, paint stripping, and cleaning and deodorizing fire, smoke, and mold damage.
Vertical sandblasters are designed for cleaning brick, stone, and concrete walls. Walk-behind sandblasters are wheeled across a surface to clean concrete floors before recoating. Vertical and walk-behind blasters often have an integral vacuum system to collect blast media and dust.
Chemical Plants / Refineries – Corrosion is an ever-present issue in chemical plants and refineries due to acids, salts, and corrosive species in these facilities. Sandblasting is required to remove corrosion from tanks, pipes, valves, and pumps.
Corrosion under insulation (CUI) applications is a common problem in chemical plants and refineries with insulated piping systems. Corrosion under the insulation needs to be removed with sandblasting. A new protective coating is applied, and then the piping is reinsulated.
Coatings on industrial flooring and concrete walls in chemical plants deteriorate or wear out over time. Walk-behind and vertical blasters are used to remove the old coating and prepare concrete floors and walls for new industrial coatings.
Coating and Paint Application – The surface cleaning and anchor profile generation increase the bond strength of paints and protective coatings. Sandblasters are indispensable for preparing or keying surfaces to accept coatings.
Blasting is also important when recoating or repainting a surface. Old damaged coating and rust need to be stripped away with blasted before refurbishment with a new coating.
Corrosion Control Industry – Stripping off damaged coatings and paint layers, rust, corrosion, grease, dirt, adhesives, sealants for recoating or repair. NDT inspection or assessment of corrosion requires precleaning of the surface.
The International Standard Organization (ISO), National Association of Corrosion Engineers (NACE) and Society of Surface Protective Coating (SSPC), and American Society of Testing and Materials (ASTM) have surface preparation standards and cleanliness grades to properly prepare surfaces before protective coatings are applied.
NACE estimates the annual cost of corrosion to be $2.5 trillion!
Sandblasting equipment is one of the most powerful weapons in corrosion engineers‘ arsenal to fight the never-ending war against rust and corrosion.
Bridge & Highway Maintenance – Weathering, erosion, and corrosion deteriorate structures over time. Without proper maintenance, our bridges and other infrastructure will continue to deteriorate leading to catastrophic failures in some cases.
The concrete and steel structural members on bridges, overpasses, and highways require blasting to remove the old protective coating, enable inspection, and allow renewal or reapplication of protective coatings.
Electronics / Electrical – Micro abrasive blasters or micro blasters are a powerful tool for electronics repair. Microblasters can selectively remove solder in applications where reflow desoldering on a printed circuit board (PCB) is not a feasible option. Conformal coatings, which cannot be removed with heat or chemicals, can be stripped away with micro-blasters. Holes or vias can be drilled in PCBs using micro-sandblasters. Soldered and brazed electrical connections can utilize blasting to clean surfaces before bonding. A clean metal surface can be wet more easily by molten solder or braze.
Foundries and Forges – Abrasive blasters such as centrifugal wheel blasters and pressure blasting equipment are essential elements in foundry and forge cleaning rooms. After a shakeout operation, castings are blasted with metal shot or metal grit to remove any remaining mold sand, ceramic investment material, and then cleaned to remove any surface oxide scale on the surface. Forged parts require blasting to remove die lubricant and descale oxide layers.
Glass Fabricators – Glass panes or windows, glass bowls, glass cups, and other decorative glass objects can be frosted or patterned using stencils or masks. Microblasting is another method used to etch or engrave words and graphics onto a glass object.
Sandcarving uses abrasives to deeply etch away glass and create 3D relief patterns or images. Glassware is typically blasted with 180 grit silicon carbide.
Jewelry / Fossils - Micro blasters with soft grits can clean fragile surfaces such as the removal of encrustations on fossils. Micro-blasting with an abrasive lower in hardness than gemstones can clean jewelry without damage to precious stones.
Machine Shops / Manufacturing – Most machine shops, fabricators, and manufacturers have at least one blast cabinet to perform cleaning, degreasing, deburring, and surface preparation of machined or fabricated parts. Dies, molds, drills, end mills, saw blades, and other tools are other blasted to remove burrs and embedded debris stuck on cutting edges or between teeth. Shot peening can increase the fatigue strength and life of machined or ground shafts, tools, and structural parts.
Marine – Sandblasting is important in boat and shipbuilding and maintenance. The decks, hulls, and interior surfaces need to be protected from corrosive attacks of ocean salt sprays and mists.
Fouling on the bottom of ship hulls increases drag resulting in millions of dollars of increased fuel costs for major shipping companies. Ship hull bottoms are blast cleaned to remove algae, barnacles, and marine life fowling before recoating of low drag, ablative bottom coatings.
Medical / Dental – Cleaning, coating preparation, etching, and polishing of medical devices and dental restorations. For example, the investment or mold material on cast crowns or bridges can be gently removed with a small benchtop sandblaster or micro-blaster. Hip, shoulder, dental and other bone, and joint implants are blast cleaned to meet stringent FDA cleanliness requirements.
Mining & Gas & Oil Fields – A wide variety of mining, gas, and oil well equipment requires rust removal and a protective coating. Sour gas contains hydrogen sulfide, a toxic and extremely corrosive chemical.
Monuments / Tombstones – Portable sandblasters can etch or clean stone monuments and tombstones in remote locations such as national parks and graveyards.
Nondestructive Testing (NDT) – Coating, rust, corrosion, grease, and other surface contamination must be removed before structural components can be inspected for surface and subsurface cracks and defects. Ultrasonic, eddy current, penetrant testing, magnetic particle, and visual test methods need a clean surface for evaluations.
Plastic / Rubber Molding – Deflashing molded parts, cleaning excess resin from molds or forms. Dry ice blasting is widely used to clean plastic and rubber molds. Rubber becomes brittle at low temperatures and can be abraded away. Cryogenic blasting is used to deflash rubber and plastic parts chilled to cryogenic temperatures.
Rail / Mass Transit – Railcars, tanker cars, railcar wheels, track mechanisms are cleaned to allow inspection for cracks and corrosion as well as preparing for protective coating application. Blast rooms or portable blast pots are typically used to clean and surface prep rolling stock.
Remanufacturing – Used or damaged engines, blocks, heads, brakes, transmissions are repaired or refurbished by remanufacturers. The engine or automotive components cleaned using sandblasting equipment to remove any rust, grease, gaskets, and coatings on the surfaces. Mating surfaces are ground to remove any warpage. Cylinders are reground or relined. The remanufactured engine is reassembled and returned to service or resold.
Steel / Metal Mills – Sandblasting equipment is used in primary and secondary metal and steel mills for the descaling and cleaning of metal sheet, metal plate, strip, bar stock, rod stock, and other stock shapes. The scale or metal oxide formed during hot rolling, extrusion, drawing, or other thermomechanical processing is removed using a stream of abrasive blasting media. The blast nozzles are placed over the moving metal or steel plates or stock. The metal stock is continuously blasted clean as the alloy moves along the production line.
Thermal Spray Coating – The formation of an anchoring surface profile using abrasive blasting of surfaces on jet engine blades and other critical components is essential attaining thermal spray deposit bond strength. Thermal spray coating will delaminate from smooth, unblasted surfaces.
Welding, Brazing & Soldering – Abrasive blasting is applied before welding, brazing, and soldering to clean surfaces and assure solid joint formation. After joining, slag, rosins, oxide patinas, weld spatter, or splatter is removed using additional blasting before protective coatings are applied.
Woodworking / Cabinetry – Removing paint or wood sap before painting wooden cabinets, furniture, and trim. Wood carving and wood sign etching are also accomplished with sandblasting equipment.
Sand Blasting Advantages
Certain materials such as lead-based paints and heavy metals generate harmful or toxic dust when blasted. In these applications, specialized vacuum blasting systems or systems with high MERV filtration is required to prevent the release of harmful materials.
Operators should use a breathing air supply filter when blasting hazardous materials any material generating fine, respirable dust in a field or open factory environment.
Proper collection, handling, and disposal of the media are required as well. Wet or water blasting systems reduce the dust problem.
Answering these questions will help you in selecting the right blasting system for your surface treatment application.
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