General points

We will present in these pages the accessories concerning only the sand blasters and which can be set on the projection hoses in order to make it possible use them in very specific uses such as:
- wet sandblasting (or without dust),
- the inner tubes treatment.
Other accessories also exist such as : abrasive measure control, lighting torches, etc.
Nevertheless, the main accessory is the nozzle which choice is as important for a sandblasting operator as the hook is for a fisherman.
The working efficiency depends a lot on it and it is however an often careless element. There are several kinds of nozzles and each one is designed for a specific use field. The nozzle has to be considered as a tool which can be adapted to the work to do and the sandblasting operator must have to his disposal more than one kind of nozzle.

The kinds of nozzles

Reminder
The impact intensity, therefore the power and the output of a treatment, are directly linked to the following parameters:
- the projection speed,
- the granulometry and the abrasive outflow,
The result is that the shape of the nozzle is essential.

Evolution
For more than 50 years, the sandblasting nozzles have been made with cylindrical bores which the abrasive projection speed is about:
- 90 m/sec or 324 km/h.
In 1954, in order to optimize the shot power, "venturi" nozzles were created to obtain the more economical and profitable shape. For this kind of nozzle, the outflow speed, to equal pressure, is about:
- 200 m/sec or 720 km/h.
It is more than doubled. It is obtained thanks to a profile with a large entrance opening in a cylindrical shape, which comes out into a nozzle which widens towards the exit.

Advantages
Output:
The output being proportional to the impact speed, the "venturi" type nozzles increase it and the rise ranges between 20 and 70% in comparison with the straight nozzles.
Savings:
Due to the high projection speed, it is possible to obtain a same result with a more reduced measure of the abrasive outflow.
Efficiency:
The widen nozzle makes it possible to obtain a regular distribution of the impacts force in the projection area, unlike the straight nozzles for which a concentration of theis force is located in the middle of the shot.

Features of nozzles

Inner diameter
The nozzle outflow, i.e. the shot power, is directly linked to the air volume conductor of abrasive flowing out of its opening.
It varies roughly as the square of the diameter that is to say on the basis of:
- 100% for a nozzle with a diameter of 6 mm,
- 160% for a nozzle with a diameter of 8 mm,
- 220% for a nozzle with a diameter of 9,5 mm,
- 320% for a nozzle with a diameter of 11 mm.
It leads to an increase in the rate of the work made in the same proportions that is to say for example:
- 10 m2/h for a nozzle with a diameter of 6 mm,
- 22 m2/h for a nozzle with a diameter of 8 mm,
- 40 m2/h for a nozzle with a diameter of 12,5 mm,
These values are given to identical pressure and abrasive.
(see chart air consumptions)

Nozzles lenght
The long nozzles have, for a compressed air consumption lightly lower and for an identical abrasive consumption, higer performances.
Nevertheless, they will be used for hard cleaning work for which the nozzle can function to a distance superior to 40 cm form the part.
The short nozzles are reserved for the current work of surfaces cleaning with an easy access for which they can function to a distance equal or inferior to 30 cm.

Nozzles shape
In order to be able to treat any kind of parts and especially the interiors, the nozzles makers tried to outdo each other in ingenuity by making various and varied shapes such as:
- bent nozzles,
- diverted shot nozzles, with 1 or 2 openings,
- straight shot nozzles, (elliptical opening),
- counter-cone nozzles, (see special nozzles) etc..

Nozzles materials
The constitutive material of a nozzle is essential because it determines its longevity through its resistance to abrasion. The abrasives having different hardnesses, it is essential to adapt the one of the nozzle to the product used.
The materials used currently and their longevity in using them with mineral abrasives are:
- ceramic nozzles, longevity = 1 to 2 hours,
- cast-iron nozzles, longevity = 6 to 8 hours,
- tungsten carbide nozzles, longevity = about 300 hours,
- boron carbide nozzles, longevity = about 750 hours. In case they are used with metallic abrasives, the longevity is doubled.
Knowing that the boron carbide nozzles have a using life twice higher than the ones made of tungsten carbide, they are particularly recommended for the use of aggressive abrasives such as corundum (aluminium oxide).
The choice will be done according to the nozzle longevity. If its life is longer, it will be more economical while using it, even if it is more expensive.
The ceramic or cast-iron nozzles will be reserved for less important work because the fast wear leads to a disruption of the shot repartition and to an increase in the air consumption.