A pressure relief valve is disclosed with a first stage valve that is in series with a second stage valve, with an enclosed cavity between the first stage valve and the second stage valve. The first stage valve relieves pressure from an enclosure into the enclosed cavity between the stages, when the pressure is above a cracking pressure of the first stage valve. The second stage relieves pressure from the enclosed cavity when the pressure is above the cracking pressure of the second stage valve.

A non-return valve assembly for a high-pressure fuel injection system is disclosed. The valve comprises a valve chamber defined in part by a first body and in part by a second body and defining a valve chamber wall, an inlet passage formed in the first body and opening into the valve chamber at a valve seat defined by the first body, an outlet passage, and a valve ball received within the valve chamber and engageable with the valve seat so as to interrupt fluid flow from the outlet passage to the inlet passage through the valve chamber. The valve chamber wall comprises a plurality of guide portions to guide the valve ball in substantially linear movement within the valve chamber.

A pressure-limiting valve includes a housing and a pressure adjustment device provided therein. The pressure-limiting valve further includes a valve seat arranged in the housing and configured to be closed by a spring-loaded closing element of the pressure adjustment device. The housing is composed of cast iron having spherical graphite. The housing is surface-hardened at least in a region of the valve seat.

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.

A pressure-limiting valve includes a housing and a pressure adjustment device provided therein. The pressure-limiting valve further includes a valve seat arranged in the housing and configured to be closed by a spring-loaded closing element of the pressure adjustment device. The housing is composed of cast iron having spherical graphite. The housing is surface-hardened at least in a region of the valve seat.

In a check valve for a compressor, a valve element includes an abutting surface and an outer circumferential surface. A valve hole includes a large-diameter portion and a small-diameter portion. A communicating window has such a shape that an opening area thereof gradually becomes larger with increasing distance from a valve seat. The check valve has an open state, a fully closed state, and a buffering state. When the abutting surface separates from the large-diameter portion and the outer circumferential surface opens the communicating window, the open state is defined. When the abutting surface closes the large-diameter portion and the outer circumferential surface interrupts communication through the communicating window, the fully closed state is defined. When the abutting surface separates from the large-diameter portion and the outer circumferential surface interrupts communication through the communicating window, the buffering state is defined. The hunting phenomenon is suppressed.

A pressure relief valve for pressure equalization between an essentially closed space and the surrounding atmosphere is disclosed. The pressure relief valve includes a valve housing with: a cylindrical wall defining a flow passage, a valve body arranged to cooperate with a valve seat arranged in the outflow of the valve housing, a stem configured for axial guidance of the valve body, a lifting element or plate arranged further down in the flow passage relative to the valve seat, a flow constriction defining an essentially truncated conically shaped interior and arranged to encircle the lifting element such that a radial passage between the lifting element and flow constriction increase when the lifting element and the valve body is moved from a closed state of the pressure relief valve towards an open state of the pressure relief valve.