The invention relates to a pressure-controlled shut-off valve (1) for temporarily interrupting the air supply to a fuel cell stack in a fuel cell system, comprising a valve piston (3) which can be moved back and forth in a cylindrical housing bore (2) and which is biased in the direction of a seal seat (5) by the spring force of a spring (4), wherein a connection between an air inlet channel (6) and an air outlet channel (7) is produced or interrupted depending on the axial position of the valve piston (3). According to the invention, the valve piston (3) delimits a spring chamber (8), which receives the spring (4) and to which ambient pressure is applied, on one side and a control chamber (9), which is connected to the air inlet channel (7), on the other side within the housing bore (2). The invention additionally relates to a fuel cell system comprising a shut-off valve (1) according to the invention.

A check valve assembly may include a guide for a closure member on an upstream side the closure member and may include guide members disposed on both the upstream and downstream sides of the closure member. The closure member may include a conically shaped head of a poppet, and elongated stems may extend from the head to the upstream and downstream guide members. The guide members may include bores to receive the stems along a longitudinal axis of the check valve assembly on opposite sides of the closure member. This arrangement distributes the wear on a valve seat and the closure member more uniformly and may increase the service life of the check valve assembly. The check valve assembly may operate in surface locations or may be deployed downhole.

A valve assembly includes a valve head. A valve stem extends from the valve head and into a drain bore in a housing. A first guidance retainer ring is mounted around the valve stem at a first axial location on the valve stem. A second guidance retainer ring is mounted around the valve stem at a second axial location on the valve stem spaced apart from the first axial location.

A valve may include a valve body forming a central passage extending from a first side of the valve body to a second side of the valve body. A valve pin may be located within the central passage, where the valve pin includes a sealing head that selectively contacts a valve seat of the valve body to control flow of a fluid through the central passage. A spring may have a first end that is fixed relative to the valve pin. A spring seat may be fixed relative to a second end of the spring, where the spring is fixed relative to a calibration plunger, and where the calibration plunger is secured to a threadless calibration wall of the valve body via an interference fit.

A valve assembly includes a valve head. A valve stem extends from the valve head and into a drain bore in a housing. A first guidance retainer ring is mounted around the valve stem at a first axial location on the valve stem. A second guidance retainer ring is mounted around the valve stem at a second axial location on the valve stem spaced apart from the first axial location.

A valve may include a valve body forming a central passage extending from a first side of the valve body to a second side of the valve body. A valve pin may be located within the central passage, where the valve pin includes a sealing head that selectively contacts a valve seat of the valve body to control flow of a fluid through the central passage. A spring may have a first end that is fixed relative to the valve pin. A spring seat may be fixed relative to a second end of the spring, where the spring is fixed relative to a calibration plunger, and where the calibration plunger is secured to a threadless calibration wall of the valve body via an interference fit.

The present application provides a backflow prevention device, and relates to a backflow prevention technical field. Such a backflow prevention device includes a shell seat, a one-way mechanism and a flow controller. The shell seat is provided with a water channel therein, the one-way mechanism is assembled in the water channel, and the flow controller is assembled in the water channel and located upstream of the one-way mechanism. When the water flows through in a forward direction, the water first passes through the flow controller, and then pushes a movable plug of the one-way mechanism to move forward, so that the water flows forward from a periphery of the movable plug along the water channel and finally passes through a bottom cover of the one-way mechanism.

A pressure relief valve for a two-phase immersion cooling system is configured to support fluid flow rates up to 500 cfm, 550 cfm, 600 cfm, or even 2000 cfm. This, in turn, allows the cooling system to support computing systems with a power density greater than 250 kW. This is accomplished by the valve having a relatively large passage (e.g., 2-6 inch diameter), a relatively large spring (e.g., 1.5-1.7 inch diameter), and a guide rod rigidly coupled to the poppet and slidably coupled to a guide plate. The valve may be used as an outlet valve and coupled to an adsorbent chamber to reduce the loss of coolant from the system as air is vented to an ambient environment. The valve may be used as an inlet valve and coupled to an adsorbent chamber to reduce the intake of water vapor as air from the ambient environment flows into the system.

The invention relates to a mechanical valve assembly used in the control of a fluid (e.g. gas, liquid, etc.) to provide at least one of a check valve control feature and flow range control feature. When unwanted low flows are present, the valve remains closed and jumps open only at higher desired flow rates. The valve then closes when the forces at the input and output equalize and the process repeats. Such allows fluid delivered to a flow meter in larger segregated bursts, rather than steady low flows that cause metering error.

The check valve includes: an inlet pipe body part (23) which includes an inflow port (23b); an outlet pipe body part (25) which includes an outflow port (25b); a mobile body (a reciprocative body (2)). Insides of the inlet pipe body part, the outlet pipe body part, and the valve body (12) are communicated to form a curved flow path from the inflow port toward the outflow port. The reciprocative body includes a valve element (6). The seat (23c) is arranged so as to be capable of supporting the valve element and the inflow port and the seat are arranged parallel to each other. An inner wall surface (23y) on an outside-corner side of the flow path in the inlet pipe body part is formed so as to curve toward a side of the outlet pipe body part as a position gets closer from the inflow port to the seat.