There is a lower and upper limit where the efficiency of the inductor is at its best. A flow below 100 liters has to low energy in relation to the losses and a flow over 3000 to 4000 liters has a reduced projected surface area relative to the water flow inside the vacuum chamber. After this size, more pipes are added. 2, 3 or 5 in parallel.
The developed design provides maximum suction capacity that ensures that the inductor delivers the foam fluid flow desired by marginally exceeding the value we call switching point. The laws of physics make it possible for water to cavitate at room temperature at 9.5 meters of suction, by keeping the constant foam flow over this point, as well as adapting to the viscosity of various foam liquids. The word Viscosity can´t be used for non-Newtonian fluids without indicating pressure drops and dimensions of the dosing orifice. In order to do this right, non-tested foam fluid must be run in the lab to be compared to water and used as simulated foam in later tests.
Size calculations are based on long experience. There is a minimum pressure on inlet water flow, as recommendation 4 bar. Under this pressure, the energy is so low that non-calculated mounting factors can affect the desired function.
In a test run in the lab, both water flow and foam flow, at 3.5 meters suction height (unless otherwise specified), are checked and the dosing orifice is individually adjusted.
There is a difficulty for the customer to calculate the system as the specified flow values of nozzles is allowed to differ widely due to the current standard. On sprinkler systems, it is less important here, as the nozzle pressure may be low with a high-pressure drop over the inductor.
With monitors or similar arrangements the difficulty is significant as for example a 5% lower flow which gives 10% lower pressure drop over the inductor, then the margins have passed and the function is compromised. If it is the reverse, 5% above the calculated flow then the pressure drop increases by 10% which means 10% lower nozzle pressure than calculated.