Flow mirror, also known as flow indicator (flow finder), is a kind of mirror valve category, is a necessary accessory to observe the flow of medium in the pipeline. Flow mirror, also known as flow indicator (fluid indicator), is a kind of mirror valve category, is a necessary accessory to observe the flow of medium in the pipeline. Used in petroleum, chemical industry, chemical fiber, medicine, food and other industrial production equipment, can observe the liquid, gas, steam and other media flow reaction, is to ensure the normal production of indispensable accessories. The connection mode is thread type, welding type and flange type. The water flow indicator can also be used in automatic sprinkler systems. It can be installed on the main water supply pipe or the horizontal pipe to give an electrical signal of water flow in a small area of a subarea. This electrical signal can be sent to the electrical control box and can also be used to start the control switch of the fire pump. It is widely used in blast furnace cooling system, power plant water circulation system, water (oil) pump indicator system and automatic sprinkler system