1- Straight Bore
2- Conventional design long venturi
3- Laminar flow design long venturi
4- Double venturi
5- High pressure
There are four basic questions to answer for optimum cost/performance:
1.) What blast pattern do you want? A nozzle’s bore shape determines its blast pattern. Nozzles generally have either a straight bore or a restricted venturi bore. Straight Bore nozzles (Figure 1, Number 1) create a tight blast pattern for spot blasting or blast cabinet work. These are best for smaller jobs such as parts cleaning, weld seam shaping, cleaning handrails, steps, grillwork, or carving stone, and other materials. Venturi bore nozzles (Figure 1, Numbers 2 and 3) create a wide blast pattern and increase abrasive velocity as much as 100% for a given pressure. Venturi nozzles are the best choice for greater productivity when blasting larger surfaces. Long venturi style nozzles like the BRUISER® blasting nozzles, for example, yield about a 40% increase in productivity compared to straight bore nozzles, while abrasive consumption can be cut approximately 40%. Double venturi and wide throat nozzles are enhanced versions of the long venturi style nozzle. The double venturi style (Figure 1, Number 4) can be thought of as two nozzles in a series with a gap and holes in between to allow the insertion of
atmospheric air into the downstream segment of the nozzle. The exit end is also
wider than a conventional nozzle. Both modifications are made to increase the size
of the blast pattern and minimize the loss of abrasive velocity.
Wide throat nozzles (Figure 1, Number
5) feature a large entry throat and a large,
diverging exit bore. When matched with
the same sized hose they can provide
a 15% increase in productivity over
nozzles with a smaller throat. When
wide throat nozzles also feature a larger
diverging exit bore (e.g., BAZOOKA®
nozzle), they can be used at higher
pressures to yield up to a 60% larger
pattern with lower abrasive use.
It's also a good idea to have angle nozzles
available for tight spots like bridge lattice,
behind flanges, or inside pipes. Many
operators waste abrasive and time waiting
for ricochet to get the job done. The little
time it takes to switch to an angle nozzle is
always quickly recovered and total time on
the job is reduced.
2.) Can your compressed air supply
support the nozzle? As a general rule, the air supply system
should be able to provide at least 50%
more air volume (cfm) than a new nozzle
would need to develop the required
working blasting pressure, whether that
is 100 psi or 140 psi. This ensures a nozzle
can continue to provide good service
even after it is slightly worn. Remember,
though, excessive wear should not be
allowed because productivity decreases
Keep in mind, too, the nozzle entry throat
must match the inside diameter of your air
supply hose. The wrong size combination
can lead to wear points, pressure drop, and
excessive internal turbulence.
3.) What bore size do you need? For maximum productivity, select the nozzle bore size based on the desired blast
pressure and the available air pressure and
flow. For example, assume you are running
a 375 cfm compressor at 80% capacity. In
addition to the blast cleaning nozzle, the
compressor is supplying air to an air helmet
and other components such as air motors
and pneumatic controls, leaving 250 cfm
available for the nozzle. 250 cfm is sufficient for a 7/16" nozzle
operating at 100 psi. A larger nozzle, or a
worn 7/16" nozzle, will require more air
flow to maintain 100 psi. This extra flow
requirement will either overwork your
compressor or decrease productivity. On
the other hand, choosing a nozzle with a
bore smaller than your compressor can
supply will result in less than maximum
productivity from the system.
4.) What are the best nozzle material
choices? Nozzle material selection depends on the
abrasive you choose, how often you blast,
the size of the job and the rigors of the job
site. Here are general application guidelines
for various materials.
Aluminum oxide “alumina” (ceramic)
nozzles offer good service life at a lower
price than other materials discussed here.
They are a good choice in low usage
applications where unit price is a primary
factor and nozzle life is less important.
Tungsten carbide nozzles offer long
life and economy when rough handling
can’t be avoided and mineral or coal
slag abrasives are used. All tungsten
carbide nozzles are not equal. Note that
all our tungsten carbide nozzles
feature top wear grade material and
BP200 SiAION nozzles offer service life
and durability similar to tungsten carbide,
but these nozzles are only about half the
weight of tungsten carbide nozzles. BP200
SiAION nozzles are an excellent choice
when operators are on the job for long
periods and prefer a lightweight nozzle.
Boron carbide nozzles provide long life
with optimum air and abrasive use. Boron
carbide is ideal for aggressive abrasives
such as aluminum oxide and selected
mineral aggregates when rough handling
can be avoided. Boron carbide will
typically outwear tungsten carbide by five
to ten times.
ROCTEC® composite carbide nozzles
provide even longer life than that of
boron carbide nozzles. We currently offer
two grades of this popular "binderless"
tungsten carbide hard material: ROCTEC®
100 and ROCTEC® 500. This nozzle material
is ideal for applications using aggressive
abrasives like aluminum oxide and silicon
carbide. Special angle nozzles, industrial
gun inserts for the polular styles, etching
nozzles, and pencil blast nozzles are a few
of the special types of nozzles currently
available. Not all current nozzle styles
are available in ROCTEC®, however, new
ROCTEC® nozzle styles are being added
every day so check with us when you have
precision requirements in blasting, drilling,
When wet blasting
is a requirement: There are three options when wet
blasting is required or desired.
First is a “water ring” attachment for
standard blast nozzles that forces water
on the blast stream as it exits the nozzle.
While inexpensive, this option uses a
lot of water and reduces the size of the
blast pattern and the energy of the blast
stream, cutting productivity up to 50%.
Second is a water injection system
that uses a high pressure pump to get
water into the abrasive and air stream.
Not only does this type of system add
considerable cost and mechanical
complexity, it slows air stream velocity
and requires as much as six gallons of
water per minute.
The third option is the WIN® water
The WIN® system uses a unique nozzle
configuration that takes advantage of
the venturi principle to draw or induct
water from a low pressure line into the
abrasive and air stream. This method is
much simpler than a water injection
system, effective, and water
consumption is reduced from up to
six gallons per minute to not more
than several quarts...usually less.
By reducing water use you increase
abrasive velocity and work speed.
You enjoy a larger blasting pattern
for greater production rates since WIN®
nozzles incorporate a considerably
larger orifice than conventional nozzles.
You also gain flexibility since the WIN®
system can also operate with air only
for blowdown applications or with an
air/water mix for rinsing applications.