The invention relates to a valve
assembly (1) for controlling the
gas pressure in a gas rail (2) of a fuel
system for supplying an
internal combustion engine with a gaseous fuel, in particular with
natural gas, comprising a first valve (3) for connecting the gas rail (2) to a gas feed (4), a second valve (5) for connecting the gas rail (2) to a gas return (6), and a control
piston (7) for actuating both valves (3, 5), wherein the control
piston (7) delimits a control chamber (8), to which a
hydraulic pressure medium can be applied by a pressure medium feed (9) and which can be depressurized via a pressure medium
discharge (10), and further comprising a sealing element (11) which is designed as a corrugated or folding
bellows and is arranged between a
gas chamber (12) and a pressure mediumchamber (13) for media separation. The valve
assembly is characterized by a pressure differential limiting valve (14) having a reciprocating
piston (15) which, on the one hand, is acted upon by a pressure (p1) prevailing in the
gas chamber (12) and which, on the other hand, is acted upon by a pressure (p2) prevailing in the pressure medium chamber (13), and which opens an additional gas return (16) when a predetermined pressure differential applied to the piston (15) is exceeded. The invention further relates to a fuel
system comprising a valve
assembly (1) according to the invention for controlling the
gas pressure in a gas rail (2).