SP15F-SP45F liquid digital locking balance valve is a kind of regulating valve with special function of digital locking. It adopts DC valve body structure and has better equal percentage flow characteristics. It can reasonably distribute the flow and effectively solve the problem of uneven cooling and heating at room temperature in heating (air conditioning) system. At the same time, it can accurately adjust the pressure drop and flow rate, so as to improve the liquid flow state in the pipe network system and achieve the purpose of liquid balance and energy saving. The valve is equipped with opening indication, opening locking device and small test pressure valve for flow measurement. As long as the balance valve of appropriate specification is installed in each branch and user's inlet, and the special intelligent instrument is used for one-time debugging and locking, the total water volume of the system is controlled within a reasonable range, thus overcoming the unreasonable phenomenon of "large flow, small temperature difference". The product is an ideal product in heating system. The sp45f balance valve can be installed on both the water supply pipe and the return pipe. Generally, we suggest that it should be installed on the return pipe, especially for the high temperature loop. For the convenience of debugging, it should be installed on the return pipe.