1. Liquid-pressure style safety valve is a assistant equipment of the breathing valve (moving disc style), the active pressure of aspi-ration and expiration is higher than breathing valve (moving disc style), as upon once the breathing valve does not work in winter, themoving disc will be frozen, the liquid seal of the liquid-pressure style safety valve can be broken for protecting the oil tank. 2. Liquid-pressure safety valve will be installed in top of oil tank and assorted used with breathing valve. 3. The control pressure: +56mm water column to -50mm water column.