When the pressure water of the water supply pump enters the proportional mixer from the inlet pipe and valve, most of the water enters the main pipe and the proportional mixer throttling device. According to the principle of fluid mechanics, a section of low pressure zone is formed behind the throttling device, and a small part of the water enters the inlet pipe and flows into the storage tank, squeezing the diaphragm. Under the pressure of the pressure water, the extinguishing agent in the bag enters the low pressure zone of the proportional mixer through the outlet pipe and the outlet valve, so that the water and extinguishing agent are automatically mixed in proportion to form a foam mixture, which is sent to the foam generator and the spraying equipment through the pipeline for extinguishing.

In many practical engineering applications, the design requires that electric ball valves should be installed on the water inlet pipe and liquid outlet pipe of the foam tank, and the field control cabinet should be equipped. The control principle is as follows:

Principle of fire automatic control: When the on-site control cabinet is set to automatic mode, when the fire signal arrives, the inlet electric ball valve and outlet electric ball valve (220V) on the storage tank will be automatically opened; When the fire signal disappears, the inlet valve and outlet valve are automatically closed. There is a working status indicator light on the control cabinet (closed/open), and the valve feedback point on the control cabinet is the active point (220V), If passive feedback contacts are required, they should be specified in the procurement requirements.

When manually controlling, the on-site control cabinet must be set to manual mode, and the corresponding valve opening and closing buttons on the control cabinet should sequentially open/close the inlet electric ball valve and the outlet electric ball valve. In case of power shortage in the on-site control cabinet, the valve opening wrench equipped on the electric valve can be used to manually open the electric valve