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When it comes to sandblasting, the blast nozzle you use is critical.
Blast nozzle selection will impact how fast you can blast, how long you can blast before replacing the nozzle, and the volume of air you’ll need to support your blast equipment.
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© iStock.com / alacatr |
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It’s important to know that you’re using the best blast nozzle selection for your application, as a variety of factors in blast nozzle design affect how fast you blast, how long the nozzle lasts, and the volume of air needed for the blast equipment.
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By properly considering the factors discussed in this article, you should be able to make choices that will perform effectively for your application and allow you to achieve maximum production at the most reasonable overall cost.
Factor 1: The Nozzle Material
Blast nozzles are made a variety of materials, each of which presents its own unique benefits and drawbacks.
As a general rule of thumb, the harder the metal a blast nozzle is made from, the longer it will last before excessive wear calls for replacement.
This is why you cannot always look at price alone when selecting a blast nozzle—although the nozzle made from harder material may cost more at the time of purchase, it may also provide twice the useful life before needing to be replaced.
This extended lifespan will often make the more expensive nozzle a cheaper option overall once you consider the extra time you get out of it.
Additionally, certain highly abrasive materials like aluminum oxide will need a nozzle made of hardened metal like boron carbide so that it does not wear excessively fast.
Common blast nozzle materials and their approximate useful life expectancy are as follows.
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Tungsten Carbide: 200-300 hours
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Silicon Carbide: 300 hours
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Boron Carbide: 700-1000 hours
Factor 2: The Nozzle Size
The size of the nozzle will have two significant effects on your blasting.
First, it will dictate the volume of compressed air you will need.
Second, it will impact the level of production you can maintain.
As a general rule of thumb, the larger the blast nozzle opening the more production you can achieve.
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Photos by Patrick Harmon unless otherwise specified |
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The length of the nozzle will affect your productivity—a longer nozzle (left) will provide more room for the media to accelerate, leading to higher production rates, but it could be hard to maneuver inside tight spaces, where a short bore nozzle (right) might be more appropriate.
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The important thing to know about blast nozzle size is that over time the nozzle will wear. This means, when you are selecting a blast nozzle, you should consider that you will need approximately 30 percent more air than the highest volume of air which the nozzle suggests is required. This will ensure you have adequate air supply.
For ease of reference, Clemco Industries Corp. provides here a great chart on compressed air requirements for different nozzle sizes.
Factor 3: The Blast Nozzle Design
The design of the blast nozzle will also be important as it will contribute to your potential production as well as to being able to accommodate any special needs you may have for the blasting application.
Typical design options include straight bore nozzles as well as venturi style nozzles.
Venturi style nozzles have a tapered design the causes media to accelerate at a faster rate than when compared to straight bore nozzles. This extra acceleration results in greater force of impact, which can help yield faster production rates than straight bore nozzles.
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Blast nozzle design can also impact productivity; on as well as to being able to accommodate any special needs you may have for the blasting application. Unlike straight bore nozzles (shown), venturi style nozzles have a tapered design that causes media to accelerate at a faster rate and produce a greater force of impact.
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In addition, the overall length of the nozzle will also contribute to your production ability. A longer nozzle will provide more room for the media to accelerate, which will lead to higher production rates.
However, a long nozzle can be problematic when you need to be able to maneuver your blast nozzle in tight spaces. If this is your situation, you can always consider a short bore nozzle.
Factor 4: Nozzle Jacket Material
A final aspect to consider is the material the casing is made of. Common options for casings include metal or rubber. The purpose of the nozzle casing is to protect the liner from any damage, since the liner is the expensive part of a blast nozzle.
Rubber jacket casings are more forgiving when it comes to drops and provide better overall protection. Metal liners do not protect as well, which can increase the likelihood of the liner cracking if the nozzle is dropped accidentally.
So if you know durability will be important for your blasting, consider a rubber jacket for the blast nozzle.
Ultimately the nozzle you select will impact the rate of production you can achieve and the overall cost of your blasting work. By properly considering the nozzle you will use, you can achieve optimum blasting results.
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| ABOUT THE 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;
Asia Pacific;
EMEA (Europe, Middle East and Africa);
Latin America;
North America;
Paint application;
Paint application equipment;
Quality control;
Quality Control;
Spray equipment;
Blasting;
Blasting nozzles;
Surface preparation;
Surface preparation equipment
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Comment from Andreas Momber, (12/5/2016, 6:17 AM)
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This is very important information and should be considered before starting your blast cleaning job. I may add a reference resource where many of these issues are discussed in deep detail: "Blast Cleaning Technology", Springer Verlag, 2008, 540 pages.
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Comment from Erik Andreassen, (10/3/2017, 9:29 PM)
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I agree that the correct choice of equipment can both improve the quality and performance of the surface preparation, what I don't agree with is the terminology used, i.e. Sandblasting, too often this is used as a general term in specifications. Abrasive blasting covers all types of media, in most of the oiutside World, sand is considered a health hazzard and is therefore a banned product. Some places allow sand to be used to remove the first layers of old coatings, but it must be proven to be chloride free. Then the final surface can be prepared using an abrasive to meet the correct standard and requirements of the specification.
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Comment from Mario Colica, (9/10/2018, 4:08 AM)
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Thanks to Patrick, as usual your article is usefull
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