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 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 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 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 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 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 device and method are described for extending the life of check valves. An improved check valve having a double poppet and tapered guides is more robust, and a check valve protection device between the check valve and the environment into which fluid is injected protects the valve from a contaminating or corrosive environment. The check valve and check valve protection device are small and light weight to prevent vibration-induced failures. The check valve protection device preferably has an interior volume that fills quickly by relatively few cycles of the lubricant pump to reduce delay of lubricant to the injection point.

A pressure relief valve (PRV) assembly may include a housing having an opening therein, an interior cavity, a passageway extending between the opening and the interior cavity, and a flange extending within the passageway adjacent the opening. The PRV assembly may also include a first stage valve carried within the interior cavity, and a second stage valve fluidly coupled in series with the first stage valve. The second stage valve may include an enlarged head carried within the opening and a shaft extending from the enlarged head through the passageway to the interior cavity. The shaft may have a proximal end coupled to the enlarged head and an opposing enlarged distal end adjacent the interior cavity. A biasing member may be between the enlarged distal end and the flange. The biasing member may be configured to bias the first and second stage valves to a closed position.

A pulse-width-regulating valve is for the regulation of a fluid flow or a fluid pressure. The pulse-width-regulating valve comprises a cut-off valve connected in series with an inflow valve, at least one of the cut-off valve and the inflow valve being provided with an axially displaceable or rotatable valve element which has an opening position or a closing position at a distance from a starting position of the valve element. A method of operating a pulse-width-regulating valve comprises: regulating a valve gear device by a valve synchronizer, in accordance with at least two displacement curves; and by one or more valve actuators, displacing or rotating corresponding valve elements arranged in the pulse-width-regulating valve.

An apparatus for allowing the repetitive oscillation of pressure in a container or vessel having a finite volume. The apparatus comprises a valve having first opening, a valve enclosure having a second opening, and a first tension device. In some embodiments the apparatus can have a chamber capable of oscillating in volume. The oscillation of the chamber volume causes a decrease in the pressure of the container. As the pressure of the space or container decreases, two openings of the apparatus become more proximate. Eventually the openings partially overlap, allowing a gas, or fluid, to enter the container, increasing pressure of the space or container. As a result of the pressure increase, the first opening and second opening become less proximate by a force of the first tension device. The apparatus can allow the container to approach substantially perfect vacuum and rise toward atmospheric pressure.