Brass valve (reducing valve) is a control valve in the body of the opening of the opening and closing of regulating the flow of medium, the medium pressure is reduced, at the same time with the aid of the role of the valve after pressure adjust the opening of open-close part, keep the valve after pressure within a certain range, under the condition of the inlet pressure changing, keep the outlet pressure within the scope of the set, protection appliances for production from then on.