A method of shutting down operation of a fuel cell system is disclosed, comprising a fuel cell stack, the method comprising the sequential steps of: i) ceasing a supply of fuel to the fuel cell stack; ii) closing a shut-off valve on an exhaust line in fluid communication with a cathode system of the fuel cell system, the cathode system comprising a cathode fluid flow path passing through the fuel cell stack; iii) pressurizing the cathode system with an air compressor in fluid communication with a cathode air inlet port in the fuel cell stack; and iv) ejecting water from the cathode flow path.

A relief valve having a crenelated exhaust ring surrounding the poppet. The crenelated exhaust ring comprises a series of alternating crenels and merlons which together define an increasing cross-sectional exhaust area circumferentially about the poppet during cracking (i.e., once the pressure in the inflatable device exceeds the cracking pressure) as the poppet rises in the relief valve in response to increased pressures and, conversely, a decreasing cross-sectional exhaust area about the poppet during closing as the poppet lowers to its re-seated, sealed position. The design of the crenels in the form of a larger upper cross-sectional area to a smaller lower cross-sectional opening, advantageously achieves a reseating pressure that is substantially equal to or slightly less than the cracking pressure while minimizing possible oscillations during re-seating of the poppet. The crenelated exhaust ring surrounding the poppet advantageously results in a relief valve having a higher flow rate at a given back pressure than would be achieved without the crenelated exhaust ring surrounding the poppet.

A bleed valve includes a valve housing defining an inlet and an outlet with a flow path for fluid communication from the inlet to the outlet. A poppet head is connected to the valve housing by a primary spring and a secondary spring. The poppet head is configured for movement relative to the valve housing between: a fully open position in which the poppet head is spaced apart from the inlet to allow flow through the flow path, with the primary spring and secondary spring both expanded; a partially closed position in which the poppet head is spaced apart from the inlet but is closer to the inlet than in the fully open position, with the primary spring compressed; and a fully closed position in which the poppet head seats against the valve housing blocking flow through the flow path, with the primary spring and the secondary spring both compressed.

A bleed valve includes a valve housing defining an inlet and an outlet with a flow path for fluid communication from the inlet to the outlet. A poppet head is connected to the valve housing by a primary spring and a secondary spring. The poppet head is configured for movement relative to the valve housing between: a fully open position in which the poppet head is spaced apart from the inlet to allow flow through the flow path, with the primary spring and secondary spring both expanded; a partially closed position in which the poppet head is spaced apart from the inlet but is closer to the inlet than in the fully open position, with the primary spring compressed; and a fully closed position in which the poppet head seats against the valve housing blocking flow through the flow path, with the primary spring and the secondary spring both compressed.