This is a list of common abrasive blasting terms that every sandblasting professional should be familiar with.
Alphabetical Quick Links
(aka media or grit). A granular material used for blasting the surface of an object. Avoid using abrasives that contain silica, as these are a health hazard. Common blasting abrasives include glass beads, crushed glass, steel shot, steel grit, aluminum oxide, garnet, plastic grit, coal slag, walnut shells, corn cobs, silicon carbide, pumice, peach pits, or sodium bicarbonate.
A trap is a screening device installed on the outlet of blasting equipment. An abrasive trap keeps the abrasive media from reaching the outlet valve, thus extending the lifespan of the blasting media. If your abrasive blasting equipment is designed to have an abrasive trap, we advise against running your equipment without the trap in place. This can cause the outlet valve to fail prematurely.
A cutoff is an optional feature on sandblasting machines. These use a button or switch to stop the flow of abrasive, while the flow of compressed air continues. This allows blast machine operators to blow off objects with high velocity compressed air after a blasting job.
An anchor pattern is a measurement of surface roughness, used in painting or coating. The “valley” of the anchor pattern allows the coating to properly bond to the surface. If the surface is not rough enough, the coating may not adhere properly and will fail. If the surface is too rough, covering the surface completely with the coating may be difficult, or require an excessive amount of the coating material.
At a microscopic level, the anchor pattern is the peaks and valleys of the treated surface. Most paint or coatings manufacturers will specify the required anchor pattern profile for optimized adhesion.
An anchor pattern profile is measured in millimeters, microns or mils. Anchor patterns generally range from 3 mils or less (1 mil = 0.001″).
(American National Standards Institute). A private, non-profit organization that focuses on developing and promoting standards that 1) assure the health and safety of consumers and 2) look out for the protection of the environment. The most common applications of ANSI in the blasting industry is the certification of respirator lenses.
A blast nozzle is attached to the end of the blast hose or cabinet suction gun. The purpose of a blast nozzle is to accelerate and shape the stream of propelled abrasive blast media. Blast nozzles must survive the constant bombardment of abrasives, so they are made of hard materials like tungsten-carbide, ceramic, boron-carbide, or SiAION. Usually, blast nozzles are encased in polyurethane, brass, or aluminum. Blast nozzles can be threaded, flanged, or smooth, depending on the type of holder they will fit into.
The internal shape of the nozzle bore determines the way the abrasive stream will perform (for example, venturi, double venturi, or straight bore). Bore size is important in abrasive blasting. A larger bore size will allow a higher flow rate of abrasive, but this will also require a higher CFM (cubic feet per minute) of air to propel it.
Nozzles should be replaced when the bore diameter wears to 1/16 of an inch larger than the original size. Bore size is commonly referred to as a number, which refers to how many sixteenths of an inch (1/16″) wide the bore is. For example, a #3 nozzle would have a bore that is 3/16″ wide.
Below is a chart showing the estimated life cycle of each nozzle material for different abrasive media types.
|Estimated Service Life in Hours|
|Nozzle Material||Steel Shot / Grit||Glass Bead/ Crushed Glass||Aluminum Oxide|
(aka to depressurize). Blow-down is the release of stored compressed air from inside an abrasive blasting cabinet. In pressure release blasting equipment, blow-down takes place whenever the control handle or foot pedal is released. In pressure hold blasting equipment, blow-down must be manually initiated by turning a valve.
An abbreviation for cubic feet per minute, a measure of the volume of air flow. In abrasive blasting, CFM refers the amount of air flow required to effectively propel abrasive media through a blast nozzle. If your air compressor is too small, your CFM will be too low to effectively blast an object. Inadequate CFM can also cause your blasting equipment controls to malfunction. To determine the correct CFM for your blasting equipment and nozzle, please refer to the chart below.
|Siphon Blast Cabinet CFM Consumption|
|Nozzle Size||Air Nozzle Orifice||30 PSI||40 PSI||50 PSI||60 PSI||70 PSI||80 PSI||90 PSI||100 PSI||120 PSI|
|1/4″ (#4), 5/16” (#5)||1/8”||9.8||12.03||14.26||16.39||18.62||20.76||22.99||25||30|
|5/16” (#5), 3/8” (#6)||5/32”||15.31||18.8||22.28||25.61||29.09||32.43||35.92||40||49|
|Direct Pressure Blasting CFM Consumption|
|Nozzle Size||Nozzle Size (Decimal)||20 PSI||30 PSI||40 PSI||50 PSI||60 PSI||70 PSI||80 PSI||90 PSI||100 PSI|
A manually operated ball-valve located on blasting equipment between the pusher line leading to the metering valve, and the split where compressed air enters the pressure vessel. A choke valve is used to clear minor obstructions in metering valves. When the choke valve is closed, higher pressure is achieved above the metering valve, forcing the obstruction through.
IMPORTANT: Choke valves should only be closed for one to two seconds when clearing obstructions. At other times, choke valves must remain completely open, or damage to the metering valve can occur.
Commonly used on pressure release blasters, combination valves are both an inlet valve and an outlet valve in one unit. When actuated, the combination valve pinches down on a hose connected to the blast equipment’s blow-down outlet, simultaneously opening the inlet side of the valve.
A pneumatically or electrically triggered device that can start or stop the flow of compressed air to blasting equipment components. When the deadman switch is activated, it triggers a control valve located on the blasting equipment to start and stop blasting. Multiple control valves are used in systems with an abrasive cutoff option. This allows different valves to be controlled independently. Standard pressure release blasting equipment with pneumatic deadman controls do not require control valves because the deadman handle provides all the necessary control over the blasting equipment systems.
(aka deadman switch, remote control, control handle). The start/stop switch for blasting equipment. Normally, a deadman switch is attached to the blast hose near the nozzle. The deadman starts the operation of blasting equipment when pressed, and automatically stops operation of the blast equipment when released or dropped.
OSHA requires all abrasive blasting equipment (except for some automated blasting machines) to be equipped with remote control systems with deadman safety handles.
A machine used to separate and collect airborne dust caused by abrasive blasting. Particles and dust from the blasted object are thus prevented from escaping into the surrounding work area. Some dust collectors use bag type filters, while others use cartridges.
Two systems for maintaining the filtering ability of dust collection systems exist. The first is called a magnehelic system, which continuously pluses valves which shake or flex the filter elements, removing excess dust. A magnehelic gauge must be read to determine when the filter elements must be replaced. The second type of dust collector is known as a photohelic system. In a photohelic system, the filters are automatically pulsed or shaken only when necessary, thus reducing noise and air consumption.
Flat Style Metering Valve
(aka pancake valve, flat sand valve). A type of metering valve which uses a flat disc with a hole to regulate the flow of abrasive media. The hole can be rotated into the path of the abrasive, using a handle to adjust the flow. Flat style metering valves are typically manual, and used on pressure release systems (like a pressure pot blaster).
Hardness Scale (aka Mohs Hardness)
(Mohs scale of mineral hardness). Created in 1812 by geologist Friedrich Mohs, this scale of hardness measures the ability of comparative minerals to scratch one another. This is a 1 to 10 scale, with talc being a 1, and diamond being a 10. This is sometimes used to measure the hardness of a particular abrasive material.
Here’s the Mohs hardness for several popular abrasives.
|Crushed Glass||5 to 6|
|Glass Beads||5 to 6|
|Garnet||7.5 to 8.5|
|Silicon Carbide||9 to 9.5|
|Plastic Abrasive||3 to 4|
|Staurolite||7 to 7.5|
|Walnut Shell||4 to 5|
|Corn Cob||4 to 4.5|
A pneumatically controlled valve installed on the inlet of some blasting equipment, that opens when blasting begins, and closes during blow-down.
The valve used to adjust the mixture of abrasive with compressed air located under the pressure vessel of abrasive blasting equipment. Common types of metering valves include automatic plunger valves, manual plunger valves, flat style metering valves, automatic pinch metering valves, manual pinch metering valves, and doughnut type metering valves. All metering valves come in contact with abrasive, and are subject to wear and tear. For this reason, metering valves should be serviced, lubricated, and inspected for wear according to the manufacturer’s recommendations (usually every 90 days of use). All makes and types of metering valves that are serviced properly, and have worn components replaced before a failure — these tend to last much longer.
(The National Institute for Occupational Safety and Health). NIOSH is the federal agency responsible for conducting research and making recommendations for the prevention of work-related injuries and illnesses. In the sandblasting industry, NIOSH approves and assigns approval numbers to respirators.
(National Pipe Thread). The United States standard for tapered threads used on threaded pipes and fittings. The taper on NPT threads allows them to form a seal when torqued, as the threads compress against one another. This is opposed to parallel or straight thread fittings, where the threads merely hold the pieces together, and do not provide the seal. NPT piping is notoriously difficult to measure since the OD and ID are not typically representative of the size.
(Occupational Safety and Health Administration). OSHA is part of the United States Department of Labor. Congress created OSHA to assure safe and healthful working conditions by setting and enforcing standards, and by providing training, outreach, education, and assistance.
A pneumatically controlled valve installed on the outlet of some blasting equipment that closes while blasting, and opens during blow-down.
One of two types of blasting cabinets. Pressure cabinets mix compressed air and abrasive outside of the cabinet, then send the mix into the media blasting cabinet through a single piece of blast hose. The way a pressure cabinet works is very similar to the way commercial pot blasting systems work.
(aka guillotine valve). A pinch valve stops flow in a hose by pinching down on it when the valve receives signal pressure. Systems with pinch valves commonly have a backup emergency tank of air, since the pinch valve requires air pressure to remain closed.
A type of metering valve which uses a plunger inside a sleeve with an orifice to regulate the flow of abrasive. Adjustments are made by turning a knob on top of the valve. Automatic plunger valves have the added functionality of being able to completely close the plunger with a pneumatic signal. These are often used on pressure hold systems, and systems with an abrasive cutoff feature. Manual plunger valves are used on pressure release systems.
The part of the abrasive blaster which is forced up and seals the pressure vessel when compressed air is directed into the pressure vessel. When the abrasive blaster is depressurized, the pop-up falls back down, allowing abrasive media to be poured in.
(aka manual blow-down). Any blasting system in which the pressure vessel remains pressurized when the deadman switch is released. In order to make this possible, an automatic metering valve (like an automatic plunger valve) is necessary. This is because both the metering valve and an air valve must close in order to allow pressure to remain in the pressure vessel. Pressure hold systems must be blown-down manually by opening a valve. These systems have several advantages, including faster starts and stops, reduced throbbing of the blast hose at start-up, and they hold up much better when the equipment is used for repeated short intervals of blasting. Most pressure hold systems can be equipped with an optional remote blow-down, mainly for use in blast room configurations with overhead hoppers for automatic re-filling of abrasive material.
(aka automatic blow-down). Any blasting system in which the pressure vessel automatically depressurizes when the deadman switch is released. Since the metering valve remains open, starts and stops are slower than with a pressure hold system. The blast hose will also have a tendency to throb on start-up, due to abrasive media collecting in the hose during blow-down.
Pressure release systems are not optimal to use when repeatedly blasting for short intervals (short cycle). This is because the constant cycle of pressuring up and depressurization will cause premature wear. Pressure release systems are commonly used with overhead media hoppers, as these can be automatically filled when the deadman handle is released.
A length of air hose on abrasive blast machines that supplies compressed air to the metering valve to be mixed with abrasive media.
A piece of blasting equipment that separates used abrasive media that can still be re-used, from the dust created by blasting. The reclaimed abrasive material is then re-used for sandblasting. Reclaimers fall into two categories: centrifugal or gravity-fed airwash. Not every type of abrasive blast media is meant to be re-used.
(aka hood, or helmet). Protective head gear which protects the wearer during blasting. The respirator helps supply fresh air for the blasting operator to breathe. Respirators are necessary to properly protect workers from the hazards of blasting. Filters are used with respirators to ensure the breathing air quality meets minimum standards set by OSHA. In cases where the compressed air source is potentially contaminated with carbon monoxide (for example, when air is fed from a diesel compressor).
A hazardous substance which is contained in many naturally occurring abrasives like beach sand. Dust produced by blasting with abrasives which contain silica will cause severe respiratory disease when inhaled. Never use abrasives which contain silica under any circumstances, even when a respirator is being used.
Sodium bicarbonate or baking soda. Sometimes used as a blast abrasive (aka soda blasting) for one-time applications. The soda is disposed of as soon as it comes off of the parts being blasted. This limits contamination of the abrasive (soda) that can be transferred to the part. Soda may also be used to prevent damage on sensitive materials during cleaning, as this is a very mild abrasive.
One of two types of blast cabinets. Suction cabinets use compressed air fed to a suction gun to pull abrasive through a separate hose (a suction hose), where it is mixed in the suction gun, and forced out through a blast nozzle. The suction gun is able to pull the abrasive through the suction hose by accelerating compressed air through an orifice creating vacuum.
(aka ergoflex). A length of flexible blast hose, (sometimes tan in color), connected at the end of the blast hose run that is easier to manipulate for the person doing the blasting.