Abrasive Blasting / Sandblasting
This article provides a comprehensive overview of abrasive blasting, also known as sandblasting. Read about what sandblasting is, how it is used, what results and effects can be achieved and what is important when using sandblast equipment.
What means sandblasting / abrasive blasting?
Sandblasting is a colloquial term for abrasive blasting and dates back to the days when sand was used as an abrasive. Sandblasting is a surface treatment process that uses various blasting media (e.g., glass beads, quartz sand, chilled cast iron, corundum, or steel grit) as abrasives and compressed air that is directed at the object (surface) to be cleaned through a blasting nozzle at a high rate of pressure and acceleration.
Areas of application for abrasive blasting
The areas of application for blasting are numerous. Typical areas of application are:
• Cleaning of machines, engines, containers (tanks) and structures
• Roughening according to various Ra, Rz, Sa specifications etc.
• Cleaning concrete surfaces
• Cleaning facades and masonry, including graffiti removal
• Rust removal, deburring and paint stripping, e.g. on steel structures or when blasting cars and truck bodies
• Roughening surfaces in preparation for painting
• Optical sandblasting (glossy surface or e.g. jeans)
• Achieving structured surfaces, e.g. when blasting glass
Results and effects of the blasting process
Various results/effects can be achieved with abrasive blasting (sandblasting):
• Blasting with a brush-like cleaning effect
• Surface cleaning with and without high-polish effect
• Cleaning down to a near white metal surface
• Cleaning down to a complete white metal surface
Depending on the blast media used, a dual function can be achieved by abrasive blasting. On the one hand, the blasted surface is cleaned of dirt such as rust, scale or paint and, on the other hand, the surface is roughened for further processing (priming and painting).
Important aspects of sandblasting machines
In order to be able to process a workpiece effectively and safely using sandblasting, a number of components and safety measures must be considered.
A powerful compressor ensures a suitable air supply. This must be adapted to the blasting nozzle size and blasting pressure used and not, as is often assumed, to the size of the blasting pot. Professional blasting guns or sandblasting guns shoot the abrasive precisely onto the surface to be treated. Protective measures such as blasting helmets or sandblasting cabins ensure a safe environment during sandblasting.
Essential requirements for blasting work
As a basic saying, a blasting system is only as strong as its weakest link. Therefore, individual components should not be saved on, as their weakness affects the rest of the system and reduces the performance of the overall system. Key factors for an economical blasting process are:
Compressor: The compressor must supply oil- and water-free air according to DIN 8573-1; 2010, class 6-3-4 to ensure a good flow of abrasive. Oil and water in the blasting system leads to clumping of the abrasive and thus to blockages.
An important question that everyone should ask himself, especially when blasting with the pressure blasting method, is whether the compressor has enough power (m³/min and bar) to operate the blasting pot with the respective nozzle. It is not the volume of the blast pot that matters, but the nozzle diameter used. The larger it is, the higher the air consumption.
Hose dimensions: Is the clear width of the blast hose and air hose sufficient for the system? Blasting hoses that are too small, for example, can lead to a loss of performance due to friction. A rule of thumb is that the blasting hose should be 3 - 4 times as large as the nozzle used. This is particularly important for long blasting hose lengths.
The air hose from the compressor to the blasting pot must also be at least as large as the diameter of the blasting pot piping, preferably larger than the pot piping.
Hose couplings: It is also important to ensure that there are no bottlenecks in hose couplings. Even if this is only a few centimetres between two hoses, this can mean a loss of performance.
Blast pot: Is the blasting pot big enough for your blasting work? The Clemco standard pot has a volume of 200 liters and thus provides the optimum balance between blasting time and mobility. Smaller blast pots, on the other hand, increase mobility, but at the disadvantage of blasting time.
Blasting nozzle: There are different blasting nozzles for different purposes, environments and blasting media. We or our authorized distributors will be pleased to help you choose the right blasting nozzle. However, if you want to process as much surface area as possible, it is important for you to choose a nozzle with a Venturi effect, as this increases the performance of the system enormously.
Water separator: It is a small link in the overall system, but extremely important. The first requirement for a functioning blasting system is clean and dry compressed air. The HMS water separator from Clemco helps to filter out remaining moisture from the compressor and keep the blasting system dry. Without dry compressed air, the abrasive clumps together and can lead to blockages in the system, which can cause the entire system to fail. However, the water separator does not replace the basic requirement that the compressor supplies dry air according to DIN 8573-1; 2010, class 6-3-4.
Safety equipment: Always ensure that you wear adequate protective clothing. This should not only be in the interests of compliance with standards, but also in your own personal interests. Clemco offers various types of blasting hoods (blasting helmets) and blasting suits that provide the best possible protection and allow you to work with confidence.
Abrasive media: Are you using the proper abrasive for the required effect? There are many different types of abrasives with different grain sizes. Each of them fulfills a specific purpose. Ask your blasting abrasive distributor about the suitable blasting abrasive and which one you want/should use. If the abrasive is defined in advance, the blasting system to be used and its individual components can be matched to it and costs can be reduced.
Further information about sandblasting
Do you need more information about sandblasting? In our series of articles on sandblasting you will find further and detailed information on various topics:
- Blasting methods of sandblasting
- Air supply and pressurized air requirements
- The choice of the suitable blasting nozzle
- Blast media recovery and recycling
- Remote control of blast pots
- Choosing the right abrasive metering valve
- Pressure blasting vs. Injector blasting
- Important factors for blast cabinet and blast room
- Costs of sandblasting