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How does a Venturi injector work?

In the world of pressure washers, and more generally, in the field of industrial washing, the Venturi injector is a device which allows to mix water with a chemical solution. These specific injectors exploit the Venturi effect to cause a depression through the line allowing the suction of the chemical. The Venturi effect is a physical principle according to which a fluid flowing through a pipe increases or reduces its pressure depending on its speed.

The injector is made up of a three-way body (water inlet and outlet as well as chemical inlet) usually made of brass or stainless steel. A small nozzle is placed inside the body to narrow the fluid transfer, accelerating it. This causes a pressure gap between the area before the nozzle and the one after it. The pressure is obviously higher at the inlet of the Venturi injector and lower at the outlet. The depression forming inside the body of the Venturi injector creates a “suction effect” enabling the chemical solution to be suctioned through the dedicated inlet. 

It is very important to consider the size of the passage hole of the nozzle placed inside the body when choosing a Venturi injector. This is owing to the fact that the size of this nozzle will vary in function of the variation of the water flow rate, so that there are the appropriate conditions for the functioning of the Venturi injector itself. Another key factor in the choice of the proper injector concerns the regulation of the percentage of the suctioned product. In fact, there are both regulating and steady injectors. The material of the body, which is mostly brass or stainless steel, as well as the seals will affect the price of the Venturi injector, its durability and chemical compatibility with the various solutions that can be used. Lastly, there are injectors which are designed to work at a low pressure (suction) and others to work at a high pressure (delivery).