Foam GeneratorThe foam gun is a key equipment in the foam system of shield tunneling machines. The foam system mainly includes foam solution tanks, foam solution pumps, water pumps, solution metering and regulating valves, air metering and regulating valves, liquid flowmeters, gas flowmeters, foam generators (foam guns), and connecting pipelines. The foam unit, through the two feed ports of the foam generator (foam gun), simultaneously adds foam solution and air to produce foam, injecting foam into the shield machine's excavation chamber. This is used to improve the soil layer during excavation. The soil, as a supporting medium, is enhanced in its plasticity, fluidity, impermeability, and elasticity after the addition of foam. It improves the soil bag, prevents clay from forming mud cakes, reduces friction, and thereby lessens the driving power required for the shield machine's excavation. Additionally, it serves to reduce the wear on cutting tools by providing lubrication and cooling.