Having the right blast nozzle that is sized correctly for the blast equipment and application can exponentially increase your blasting productivity and speed.
Blast Pattern Required
The blast pattern is determined by the nozzle’s bore shape.
Straight bore nozzles create a tight blast pattern suitable for spot blasting or blast cabinet uses and are best for parts cleaning, weld seam shaping, stone work, handrails etc.
Venturi bore nozzles create a wide blast pattern and can increase abrasive velocity by as much as 100%. Long venturi nozzles can increase productivity by up to 40% and reduce abrasive consumption as well up to 40% compared to straight bore nozzles.
With a Double Venturi nozzle, atmospheric air is drawn through the holes into low pressure area, expanding the air flow to produce a wider blast pattern.
Blast Nozzle Shape
The shape of the Blast Nozzle determines the blast pattern and effect. A straight bore nozzle produces a narrow, concentrated blast pattern on impact.
A long venturi nozzle produces a large blast pattern and a more uniform particle distribution than a standard bore nozzle.
In a double Venturi nozzle, atmospheric air is drawn through the holes into low pressure area, expanding the air flow to produce a wider blast pattern.
Extra-long nozzles accelerate particles over a longer distance, achieving higher exit velocities, allowing the blaster to stand further back from the surface being blasted, and producing a larger blast pattern and higher production rates.
Blast Nozzle Material
The main factors in selecting the ideal nozzle bore material are durability, the abrasive used, impact resistance, and price.
Aluminium oxide “Alumina” nozzles are cheaper than other materials and can be used where cost is the primary factor and durability is less important.
Tungsten Carbide nozzles are less durable but relatively cheap and resistant to impact.
Silicon Carbide nozzles are less durable but lighter and cause less operator strain.
Boron Carbide nozzles are less impact resistant but extremely hard and durable up to ten times longer than Tungsten Carbide and three times longer than Silicon Carbide.
Blast Nozzle Size
When you double the diameter of the orifice, you quadruple the size of the orifice and the volume of air and abrasive that can pass through the nozzle. If the sand blast nozzle is too large, the velocity of the air and abrasive mixture is too low and ineffective for production blasting. If the sand blast nozzle is too small, it slows down the blasting efficiency.
To find your optimally productive nozzle, determine what nozzle pressure (PSI) you need to maintain for productive blasting, and what volume of air your available compressor can supply per minute (CFM), then consult the chart in the next section to find the nozzle orifice size that meets those parameters.
Lastly, air supply is a critical factor in blasting. The higher the air volume that is compressed, the higher the pressure produced at the nozzle. It increases the velocity of the abrasive particles, allowing the use of a bigger bore nozzle and imparting a deeper anchor pattern One should choose the size and type of nozzle depending on the output of the compressor, the surface characteristics and the specifications of the application. Refer to the table below to choose the right nozzle to maintain the required air pressure at the nozzle based on the air supply available.
However, it is important to find the sweet optimal spot as beyond a certain level, higher level of abrasive does not increase productivity and a bigger size nozzle increases waste.
Ways To Increase Nozzle Service Life
1. Avoid dropping or banging nozzles.
2. Use the selection criteria above to choose the optimal nozzle for your application and abrasive.
3. Inspect and replace, as necessary, the gasket, or washer of the nozzle or nozzle holder to help prevent the nozzle’s entry throat from being blasted away.
4. Inspect and Replace Nozzles. How much wear is too much? Here are three simple tests:
a. Insert a drill bit of a size that matches the original bore of the nozzle. If there’s any slop, it’s time to replace it. Nozzle wear means pressure loss. Pressure loss means lost productivity, there is a 1-1/2% loss of productivity for every pound of air pressure lost.
b. Hold an open nozzle up to the light and look down the bore. Any ripple or orange peel effect inside the carbide liner will create internal turbulence that reduces abrasive velocity. If you notice any uneven wear or pressure drop, it’s time to replace.
c. Check the nozzle’s exterior, too. The materials used to build nozzles are tough, but can be brittle. Nozzle jacketing materials are designed to help protect breakable liners from impact damage. If the jacket is cracked or dented, chances are the liner is also cracked. If the liner is fractured, even with hairline cracks, the nozzle should be replaced immediately. It is not safe to use a cracked nozzle. Remember that all nozzles will eventually wear out. Keep a supply of back-up nozzles on hand to minimize downtime.
Quantum Blast Technologies offers a range of Abrasive Blast Nozzles including Straight Bore, Long Venturi, Double Venturi, Angular, Curved and Wet Spray Nozzles for all your blasting needs. Our blasting nozzle products are available for most suction, abrasive or direct-pressure air blast systems in use today.
Our experts will get you the right blasting nozzle for your application to provide you with the greatest efficiency at the best price.