Combination valve, group valve of fuel machine, control valve are sealed by steel ball and directly loaded by spring safety valve + control valve. It is adopted to the gas machine and other air compressors with consuming great gas.

The safety valve is a kind of balance structure valve accord the balance theory of air pressure and spring. When the adjust outfit of air compressor are good working, the pressure of vessel P are more than the set pressure Ps, the valve core will open. So the pressure of vessel will open the control valve though leading holes and air compressor will be into the working. When the adjust outfit of air compressor are not working. When the pressure of vessel P is down to the set pressure Pr and the valve core will close, then the control valve will close and the air compressor will restart working.