Sandblasting is an extremely useful procedure in a broad array of applications and industries. It is useful for cleaning surfaces, deburring, preparing surfaces for power-coating, de-rusting, or removing paint. It is also popular in non-destructive testing / non-destructive examination (NDT / NDE), lining, coating, refurbishing, restoration, architecture and many other purposes.
Sandblasting equipment can be of two types – Portable for use in situ or can be stationary and installed in the workshop.
There are two types of sandblasting – dry sandblasting and wet sandblasting.
Introduction to Dry Sandblasting
In dry sandblasting, abrasive media and compressed air are mixing in a pressurised vessel and the mixture is propelled through a hand-held nozzle onto the projected surface for blasting.
This process utilises abrasives to create a high level of surface cleanliness to allow the maintenance coating to adhere without needing any secondary medium like water.
Dry abrasive sandblasting equipment is relatively cheaper, but the expense of encapsulating the surface and increased consumption of abrasive and media may be disproportionately large. If dry sandblasting is conducted in an open space for large surfaces, containment or encapsulation is necessary to collect used abrasives, dust, and hazardous paint particles.
If conducted in a blast room or blast cabinet, it is possible to confine and recover abrasives and particle debris inside an enclosed vacuum system and recycle the abrasives. The vacuum system’s key benefits are its minimal waste and clean-up costs and is especially beneficial for lead-based paints.
Dry abrasive sandblasting may not remove all soluble salts in extensively corroded surfaces and the surface may need to be tested for residual contaminants.
Figure 1 Dry SandBlasting
Benefits of Dry Sandblasting
Dry sandblasting remains the commonly used blasting procedure for many applications for the following reasons:
- Cheaper Equipment: Dry sandblasting equipment is generally cheaper than wet sandblasting equipment as they use simple technology of mixing abrasive media and air only.
- Recycling Abrasive media: If the blasting process is conducted in a contained chamber and recovery systems installed, the abrasive media can be recycled. Steel grit, and steel shot abrasive media can be used many times over.
- Efficiency: Dry sandblasting is more vigorous and offers a quicker cleaning efficiency rate.
- Flash Rust: As the process is not using water, it reduces the risk of flash rust developing on steel surfaces.
Applications of Dry Sandblasting
Dry blasting is best for components that need a lot of speed, force, and control, such as:
- Removing paint, rust, mill scale, and carbon
- Surface preparation for protective coatings
- Peening and deburring
- Plastic mould de-flashing, cleaning, and retexturing
- Glass etching, decoration, and engraving
Introduction to Wet Sandblasting
Wet Sandblasting is alternatively referred to as wet blasting, vapour abrasive blasting, wet abrasive blasting, vapour blasting, slurry blasting and dustless blasting.
Wet sandblasting is similar to dry blasting but involves an additional element of water along with the abrasive media and air. The abrasive media and chemically processed water (are mixed in to form a slurry that is propelled onto a work piece using high-velocity compressed air.
The pressure in the vessel is roughly the same as the blast hose, and a complete flow valve between the hopper and the mixing chamber controls the abrasive flow.
Vertical wheels, horizontal plane turntables, shuttles with rail or car extensions, chain or belt conveyors, and self-contained turning systems are designed for shafts, tubular sections, and combined tumbling-cabinet machines.
Portable sandblasting machines (called dustless blasting equipment) use one of the two approaches to drive the slurry against a surface:
- By a stream of compressed air that lifts the slurry through a siphoning action into the blast hose and nozzle
- Compressed air pushes a pressurised slurry through the blast hose to the nozzle
A high-pressure centrifugal pump creates the slurry’s requisite projection speed in a wet sandblasting cabinet.
Figure 2 Wet SandBlasting
Benefits of Using Wet Blasting
- Dust-free: The most significant advantage of wet sandblasting is virtually dust-free (>95% dust is encapsulated).
- No friction or static charge: There is a much lower risk of sparking and explosions where flammable gases or materials are present.
- Feathered Effect: Wet sandblasting provides a smooth feathered effect where the new coating blends with an existing coating.
- Versatility: Wet sandblasting can be used on practically any surface, including thin metal and it significantly reduces the risk of warping.
- Cleaning: An additional benefit to wet blasting is that the surface can be rinsed in the same process to completely clean any residual paint or contamination before applying the coating.
- Cost-Effective: Though slightly slower than dry sandblasting, the wet sandblasting process uses less abrasive media and compressed air.
Wet Sandblasting Application
Wet sandblasting equipment and industrial blast components of various shapes and sizes are beneficial for:
- Removing paint, rust, scale, carbon, and other deposits.
- In high pedestrian traffic areas
- Where encapsulation of dust is not feasible
- Preparing, re-painting, and re-coating, the surface before bonding
- Stainless steel and other metals with a satin finish
- Cleaning of moulds and dies
- Cleaning medical aviation components
- Removing small burrs from manufacturing components
Is wet sandblasting better than dry sandblasting?
Over the last few years, the debate between wet and dry sandblasting has gotten greater attention, and a substantial shift has begun with dry sandblasting giving way to wet blasting.
Advantages of Wet Blasting over Dry Blasting?
Wet sandblasting enjoys the following advantages over dry sandblasting.
- A much lower level of dust
- Wet Sandblasting can be done in high pedestrian traffic areas
- Reduced use of abrasive media
- A much lower level of dust
- Lower risk of hearing loss due to low level of noise
- Enhanced visibility
- Better ergonomics and work environment
- Minimal PPE and respiratory gear needed comparing to dry blasting
Finish Quality and Versatility
- Smooth and uniform feathered finish
- The surface can be rinsed to be free of any residual contamination
- Reduced risk of sparks and inflammation
- Versatile on several surfaces, including thin metal
Advantages of Dry Blasting over Wet Blasting
Dry sandblasting enjoys the following advantages over wet sandblasting.
- Cheaper equipment for basic setup
- More widely available
- Dry blasting is quicker than wet blasting as it has a more significant impact without the cushioning of water.
- Higher compressed air results in faster speed
- Abrasive media may be recycled if collected and recovery equipment is used.
- A wider range of abrasive media such as steel grit and steel shot offer increased re-use
- Waste collection of dry used media is quicker and easier to clean up.
In summary, both dry sandblasting and wet sandblasting procedures are helpful to remove contaminants such as rust, paint and to prepare surfaces for coating.
Both sandblasting methods are quicker than water blasting for cleaning a surface. Every job has its own set of requirements that can determine which method is more suitable depending on the material, present surface condition, surface roughness criteria and coating type required.
If you need to protect an open environment or adjacent dust sensitive plant significantly, then wet blasting may be the method for you. However, most other applications where adequate environmental controls, containment and equipment are more than suitable for dry abrasive blasting
With increasing environment protection awareness, lobbying, and concern for operator safety, wet abrasive sandblasting is experiencing greater adoption and popularity.
If you are unsure which approach is best for your project, contact the experts at Quantum Blast. Our experienced team will guide you through the best suggestion you need for your project. With our state of the art, RapidBlast equipment and our in-depth experience in the industry, we are equipped to provide both wet and dry blasting solutions.
Please contact us today at email@example.com and let us help you advise you on the best solution for your surface preparation needs.