Method for protecting components of a fuel cell system

1 . A method for protecting components of a fuel cell system ( 1 ), the fuel cell system ( 1 ) having a fuel cell stack ( 101 ), an air path ( 10 ), an off-gas line ( 12 ), and a fuel line ( 20 ) with a recirculation circuit ( 50 ), the method comprising the steps of:

monitoring the air path ( 10 ) for a fault;

closing a first valve ( 61 ) which is situated in the air path ( 10 ) and closing a second valve ( 62 ) which is situated in the off-gas line ( 12 );

blocking a purge valve ( 41 );

reducing a pressure in the air path ( 10 ) upstream of the first valve ( 61 );

if further operation of the fuel cell system ( 1 ) is possible:

increasing the pressure in the air path ( 10 ) upstream of the first valve ( 61 );

unblocking the purge valve ( 41 );

opening the first valve ( 61 ) and the second valve ( 62 );

further operating the fuel cell system ( 1 ),

wherein the pressure in the air path ( 10 ) is stored between the first valve ( 61 ) and the fuel cell stack ( 101 ) at a time of closing the first valve ( 61 ) and the second valve ( 62 ), and the stored pressure is used as a reference value, and

wherein prior to opening the first valve ( 61 ) and second valve ( 62 ), a pressure level of the air path ( 10 ) upstream of the first valve ( 61 ) is adjusted to a pressure level in a blocked region ( 63 ), the blocked region ( 63 ) being situated between the first valve ( 61 ) and the second valve ( 62 ) and surrounding a cathode side ( 105 ) of the fuel cell stack ( 101 ).

2 . The method according to claim 1 ,

wherein a bypass valve ( 65 ) is opened in order to reduce the pressure in the air path ( 10 ), so that air can flow from the air path ( 10 ) into the off-gas line ( 12 ) via a bypass line ( 66 ).

3 . The method according to claim 2 ,

wherein further valves and/or throttle valves and/or a turbine bypass are opened in the air path ( 10 ) and/or in the off-gas line ( 12 ) in order to reduce the pressure in the air path ( 10 ).

4 . The method according to claim 1 ,

wherein in order to reduce the pressure in the air path ( 10 ), a capacity of an air compressor ( 11 ) is reduced or stopped.

5 . The method according to claim 1 ,

wherein the adjustment of the pressure level is accomplished by a clocked opening of the first valve ( 61 ) and/or the second valve ( 62 ).

6 . The method according to claim 1 ,

wherein a reduction of a pressure level in the recirculation circuit ( 50 ) is accomplished by an opening of the purge valve ( 41 ), so that the pressure level in the recirculation circuit ( 50 ) is reduced to a pressure level in the blocked region ( 63 ) plus an offset.

7 . The method according to claim 1 ,

wherein in order to increase the pressure in the air path ( 10 ), a bypass valve ( 65 ) is closed and/or further valves and/or throttle valves and/or a turbine bypass in the air path ( 10 ) and/or an off-gas line ( 12 ) are closed.

8 . The method according to claim 1 ,

wherein, in order to increase the pressure in the air path ( 10 ), a capacity of an air compressor ( 11 ) is increased.