The Protectoseal 30, Spring Operated Tank Blanketing Valve, is designed to regulate the flow of a blanketing gas (usually Nitrogen) into the vapor space of a flammable liquid storage tank or vessel. The Series No. 30 valve is spring operated. The pressure balanced poppet is held in its closed position by direct spring force. The tank's vapor space pressure is sensed in the diaphragm case and the valve opens to allow a flow of gas into the tank when the pressure drops below its set point. When tank pressure returns to an acceptable level, the flow of gas is stopped.