1. Busting The Myths of Wet Abrasive Blasting
Bill Eliason, Graco

2. Origins of Wet/ Vapor Abrasive Blasting
Wet Abrasive Blasting was first introduced to counter the dust created by dry blasting.
Water usage in blasting was first tried in 1941
Process was never perfected
Negative perceptions exist

3. What Is Wet Abrasive Blasting?
Water is mixed with abrasive and air and propelled by air pressure

4. What Is Wet Abrasive Blasting?
Abrasive is suspended in a water projected at high velocity by a forceful flow of compressed air

5. Problems With Wet Blasting
Each wet system… although eliminating dust has had many drawbacks and problems
Over time these drawbacks and problems from older wet blast technologies have lead to many myths about anything wet abrasive

6. Improving Wet / Vapor Blasting
New developments in Wet and Vapor Abrasive Blast technologies
Increased production rates to decreased water consumption
Optimized air, water and media ratio for optimal performance
Able to achieve same profile compared to traditional blasting methods
Mixes water with media inside the pot
Adds weight to each particle (weight X speed = momentum)
Reduces friction which causes production to remain high
Makes the transportation of the media more efficient because of the lubrication factor

7. Busting or Confirming the Myths
The New Wet and/or Vapor Abrasive Blast Technology isn’t as fast as Dry Blasting
Fact
These new technologies are comparable to dry abrasive productions rates, and in some cases even faster

8. Myth Busting: Not as fast

9. Myth Busting: Not as fast
That was over 40 mils (1.016 mm) of a thick lining at a waste treatment plant – in real time.
When timed and compared to dry blasting on this job vapor abrasive blasting was 3 x faster

10. Myth Busting: Wet and Messy
The New Wet and/or Vapor Abrasive Blast Technology is too Wet and Messy
Fact
The new Vapor Abrasive Blast technology is using far less water than older systems
Uses 10 to 12 gallons an hour with 80 grit garnet

11. Myth Busting: Wet and Messy
That was inside a home with wood floors
The smoke damage was extensive
The contractor tried multiple types of systems on the market with no success
The New Vapor Abrasive Blast Technology was brought in and in 20 minutes the job was complete without water on the ground

12. Myth Busting: Won’t Meet Specs
Using the New Wet and/or Vapor Abrasive Blast Technology won’t meet SSPC SP10 specification for near white metal
Fact
Does meet spec according to Joint Surface Preparation Standard NACE No. 2/SSPC-SP 10 Near-White Metal Blast Cleaning
Section 5: Blast Cleaning Methods and Operation
Sub Section 5.3

13. Myth Busting: Won’t Meet Specs
Other methods of surface preparation (such as wet abrasive blast cleaning) may be used to achieve a near-white metal blast cleaned surface by mutual agreement between those responsible for establishing the requirements and those responsible for performing the work. Information on the use of inhibitors to prevent the formation of rust immediately after wet abrasive blast cleaning is in Paragraph A5

14. Breaking The Myths Myth # 4
The New Wet and/or Vapor Abrasive Blast Technology won’t cut/remove hard coatings and linings or pitted rust
Fact
Far more efficient at cutting hard coatings and linings as well as mill scale and pitted rust because of the way water and or vapor is utilized in the system.

15. Breaking The Myths

16. Myth Busting: Steel Profile
The New Wet and/or Vapor Abrasive Blast Technology can’t achieve a deep profile on steel substrates
Fact
These new wet technologies can achieve a full range of profiles on carbon steel from .5 to 6.5 based on grit size and hardness

17. Myth Busting: Steel Profile
Additional advantages from Vapor and Wet Blast technologies regarding profiles
The profile has more peaks and valleys per cubic ft. creating better coating adhesion
This is possible because the technology uses smaller grit sizes due to the additional weight (mass) added from water… creating the same effect as if it was larger grit

18. Myth Busting: Steel Profile
Dry Blast Systems use 16~20 grit to achieve deep profiles
16 grit averages inches (1.1mm)
20 grit averages inches (0.94mm)
Wet Abrasive Systems use 80~100 grit for a good profile
80 grit averages inches (0.17mm)
100 grit averages inches (0.12mm)
100 grit is about 1/9 the size of 16 grit

19. Myth Busting: Steel Profile
9x more peaks and valleys in the same area compared to dry blasting!!
Giving greater coating or lining surface adhesion

20. Understanding the Power of Water

21. Why It Works Momentum = Mass x Velocity
Water weighs 8.33 lbs. / gallon
By encapsulating each particle, you are adding from 60 to 120 lbs. to the weight of the media per hour.
Conventional blasters only have the weight of the media. Therefore, they try to blast with larger particles in order to blast more aggressively.
Water assists flow of media through the blast hose, thereby reducing any loss of speed caused by friction (drag). This keeps the momentum factor high.
Water acts to reduce splash-back by trapping the dust caused by both the media and the coating being removed.

22. Water Encapsulated Media
Due to water’s surface tension, the media is encapsulated, which adds weight and “lubricates” each particle.
The added weight increases momentum. The lubrication is one of the reasons why EQ’s hoses and nozzles last 3 to 5 times longer than dry-blasting hoses and nozzles.

23. Media and Water at Point of Impact
When the encapsulated particle hits the surface, the “water-jacket” is shed.
This action traps any dust created by the media and the removed surface material.

24. The Hydraulic Effect
The inertia of the water drives the droplet into the impact area, and the force of the particle hitting the area is made far more effective by this hydraulic reaction.
Water cannot be compressed and will erupt out of the impact area, causing additional removal of the coating being blasted.

25. The “Feathered” Impact Zone
The hydraulic reaction greatly improves efficiency (less media and time required to do the same job).
This aids in producing a “feathered” edge with the desired profile to meet many different types of applications.

26. Questions?