How To Choose A Nozzle For A Sandblaster
Posted: Jul 13, 2017 Clicks: 166
Buy Nozzle for sandblasting machine. How to find the most durable?
Nozzle for sandblasting qualitative surface cleaning of metal surfaces by a concentrated jet of sand is impossible if the nozzle parameters - the outlet part of the device are incorrectly determined. The nozzle for the sandblasting unit is the fastest wearing part, the durability of which, depending on the material and the air-sand mixture, does not exceed 800 ~ 1000 hours, given that it is correctly selected. About the choice, today, and will be discussed in our article.
Type nozzle design
The simplest nozzle for a sandblaster is a hollow tube with a threaded part at one end, which is intended to attach the part to the nozzle holder.
Basic geometric characteristics of replaceable industrial nozzles:
Diameter of the connecting thread (depends on the technical characteristics of the sandblasting machine, but usually a 2" or 1¼" pipe thread is used). It is also possible to connect the nozzle with the nozzle holder using a union nut and a sealing washer. Nozzles made by one's own hands are attached to the hose of the working unit using conventional clamps.
The length of the part, which varies in the range 7 ~ 23 mm (shorter ones are used to clean less polluted surfaces).
The diameter of the inner hole in its minimum cross-section. Replaceable tips with diameters of 6, 8, 10 and 12 mm are available.
The nozzle inlet diameter, determined by the diameter of the connecting hose (it can be 25 or 32 mm).
Sandblasted Boron Carbide Nozzles
The main parameter of the part in question is the profile of the internal hole, which determines the loss of air-sand mixture consumption, its speed at the inlet and outlet of the nozzle, and the value of the total hydraulic resistance, which ultimately determines the life of the nozzle.
The simplest version (suitable for production by one's own hands) is a nozzle with a cylindrical inner hole of constant diameter. But to improve the aerodynamic characteristics on these parts, two conical sections are sometimes made:
The input confuser, the presence of which allows increasing the energy of the flow of the mixture entering the nozzle;
The output diffuser, the presence of which contributes to an increase in the surface area processed simultaneously. The energy of the flow decreases, so if there is a need for better cleaning, the diffuser profile of the end of the nozzle is not always provided.
The most effective profile of the inner hole to ensure minimum loss of flow is the nozzle for a sandblast with a venturi profile.
In this case, the hole consists of three interconnected sections, each of which performs certain functions:
At the inlet of the Venturi nozzle there is a confusional expansion, the angle of which is, however, less than that of a conventional nozzle fusion nozzle (not more than 20 ~ 22º). The confuser part occupies up to 30% of the total length of the part.
Cylindrical part, not more than 15% long
Diffuser part with a sufficiently small expansion angle (7~15º), the length of which is determined by the size of the nozzle itself in the plan.
In order to reduce the hydrodynamic resistance of the working mixture that moves in the nozzle channel, all the transitions from one part to the next are performed with radial rounding, the value of which is taken within the limits r = (0,02 ~ 0,03) d, where d is the average diameter, cylindrical part of the nozzle.
How to choose a nozzle for a sandblaster?
The nozzle with Venturi profile allows to increase the speed of sand-air mixture movement by 2.5~3 times in comparison with the nozzles of a different configuration of the inner hole. A modern nozzle for a sandblaster with a Venturi profile is capable of providing particles at the outlet to 700~720 km / h. At the same time, the cleaning efficiency at the same flow rates of the mixture and pressure increases approximately 2-fold.
Nozzle for sandblasting machine by own hands
Approximately the choice of nozzle parameters can be made by the following criteria:
Performance: At the required capacity of the installation up to 10~12 m3 / h, the internal diameter of the nozzle does not exceed 8 mm, at 12 ~22 m3 / h - 10 mm, at higher capacities the internal channel diameter should be 12 mm;
For the greatest air pressure: If it does not exceed 5 atm, the channel diameter can be taken as 6~8 mm, at pressures up to 7 at – 8~10 mm, at higher pressures - 12 mm;
Depending on the specific consumption of abrasive: If this parameter does not exceed 200~ 250 kg / h, a nozzle with a diameter of 6 mm is suitable, at 350~400 kg / h - 8 mm, at 600~ 900 kg / h - 10 mm, in other cases - 12 mm.
These recommendations apply to nozzles with cylindrical inner holes. To recalculate the given data to the nozzle for a sandblaster with a venturi profile, the data on processing capacity should be increased by 35~50%, by consumption - by 60~75%, and by pressure - by 15 ~ 20%.