Fluid flowing from port a to port b passes through throttling orifice c of the first flow-control unit and throttling orifice d of the second unit. Piston 1 is subject below to the action of spring 2, and above to the pressure of the fluid after first flow control. When the pressure in port a exceeds a definite value, piston 1 moves downward and closes throttling orifice c. Since the discharge through throttling orifice d continues, the pressure above piston 1 drops and the piston rises, opening throttling orifice c again. In this way, fluctuations in flow of the fluid passing through the flow-control valve, due to fluctuations in pressure preceding the valve, are reduced.
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