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Blast It Fast: Factors that Contribute to Sandblasting Speed

WEDNESDAY, AUGUST 10, 2016

By Patrick Harmon

As a contractor, the speed at which you can prep a surface or remove contaminants can be critical for your business. The more effective and efficient you are at sandblasting, the faster you can complete a project. In general, sandblasting takes a lot more time than painting, which is why it can be so beneficial to improve your blasting efficiency. To improve blast efficiency, you should consider the following variables:

Variable 1: Sandblast Media and Type

One of the largest contributing factors to the rate at which you can clean a surface is the blast media you use. Certain blast media are harder than others, and in general, the harder a blast media is, the faster it will clean a surface.

Blast media hardness is rated on the Mohs scale, which ranges from 1-10, with 10 indicating the hardest minerals. The downside to harder blast media is they can remove a lot of surface fast, which can be problematic if you're trying to lightly clean a metal surface.

Variable 2: Blasting Pressure

Sandblasting depends on force to remove surface contaminants. Force is determined by mass and acceleration. In sandblasting, the faster we can propel media at the target surface, the faster we will remove contaminants.

Sandblasting
© iStock.com / photosoup

In general, sandblasting takes a lot more time than painting, which is why it can be so beneficial to improve your blasting efficiency.

One factor that will contribute to the speed media is moving is the pressure at which you blast. Higher sandblast pressures will allow you to remove more in a shorter time. However, you always want to verify you do not exceed the pressures your sandblast pot is designed for.

Additionally, you want to verify that you do not create too deep a profile by using too high a pressure. If you verify with a sandblast media or equipment provider the product you’re blasting and your profile goal, they should be able to help you to ensure you do not use too much pressure.

Variable 3: Sandblast Nozzle Type

Sandblasting nozzles come in a variety of styles, including short, long, and venturi or non-venturi nozzles. The fastest media velocities, and as a result the fastest production rates, will come from longer nozzles that have a venturi design. A venturi nozzle can help improve the speed at which you sandblast. In addition, longer venturi nozzles will provide greater acceleration, and as a result greater production, than short venturi nozzles.

Variable 4: The Way You Adjust Your Blast Media Flow

If you use too much sandblast media in your air stream, it will actually cause the speed of your sandblast media to slow down. By keeping sandblast media to an appropriate level, you will achieve higher blast media velocities, and as a result, greater production.

Sandblasting
© iStock.com / photosoup

If you try to blast straight at a product, media hitting the product surface will actually bounce back toward the blast media coming from your hose, which will reduce the speed of the incoming blast media.

When you are going to begin sandblasting, you should start with the media valve closed. You can have an operator in proper safety gear holding the blast hose, and another helper at the sandblast pot. The operator can start the air flowing through the blast hose. The helper at the sandblast pot can then slowly begin opening the blast media valve, when the operator begins to see a slight discoloration in the blast air they can have the helper stop opening the valve or open it ever so slightly further.

If you ever hear a clunking noise, or it seems like media is barely moving out of your blast nozzle, you have most likely put too much blast media into the air stream.

Variable 5: Effective Blast Technique

A final factor that will contribute to the speed at which you sandblast is the way in which you blast. When you sandblast, you actually want media to hit the surface at a slight angle, usually between 15 and 30 degrees. If you try to blast straight at a product, media hitting the product surface will actually bounce back toward the blast media coming from your hose, which will reduce the speed of the incoming blast media.

Conclusion

Ultimately, by managing the flow of blast media, the pressure you use, your technique, and equipment selection, you can ensure optimal efficiency when sandblasting. To know what pressure and media are appropriate, you have to know the profile you need to achieve and the substrate you are blasting. By considering all these factors, you can ensure that you obtain the right blast profile as quickly as possible.

ABOUT THE BLOGGER

Patrick Harmon

Patrick Harmon works with Pittsburgh Spray Equipment Company, a distributor for painting and sandblast equipment to industrial fabricators and manufacturers. There, he helps clients solve problems related to coating application challenges, finish quality problems, production limitations and proper equipment for desired finish end results. Patrick is pursuing his MBA while working in the field with customers and their finishing equipment challenges. Equipment Insights covers the most common questions and considerations encountered when evaluating finishing equipment. Contact Patrick.

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Tagged categories: Abrasive blasting; Abrasives; Blasting; Metal cleaning; Paint and coatings removal; Surface preparation

Comment from Jiyeol Kim, (8/20/2016, 7:58 AM)

Simple article but explain all the factors we should consider.


Comment from Andreas Momber, (12/16/2016, 3:28 AM)

These comments provide a first rough guidance to blasters. The relationships are, however, more complex. A parameter of particular interest, known from shot peening, is the degree of coverage. This parameter governs degree of cleanliness as well as cleaning speed. The complexity of the blast cleaning process is discussed very detailed in the book "Blast Cleaning Technology", Springer, 2008.


Comment from Tom Schwerdt, (1/2/2017, 11:17 AM)

One item which really should be covered is blast nozzle wear. As your nozzle wears out you consume more air (eventually losing pressure) and lose your venturi as it is worn out. Failing to promptly replace worn nozzles can end up being much more expensive due to additional blast time and blast media being used.


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