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An apparatus for detecting a leak in a conduit line includes a housing in fluid communication with the line, a valve including a valve seat and a valve element movable relative to the seat between opened and closed positions, a bypass line around the valve, a flow detector coupled to the bypass line

An apparatus for detecting a leak in a conduit line includes a housing in fluid communication with the line, a valve including a valve seat and a valve element movable relative to the seat between opened and closed positions, a bypass line around the valve, a flow detector coupled to the bypass line for detecting fluid flow therethrough, and a mechanism configured to urge the valve element toward the closed position and to maintain the valve element in the closed position until a threshold pressure drop is reached. The mechanism may operate on the principle of magnetism.

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1. An apparatus for detecting a leak in a fluid conduit line, comprising: a housing configured to be in fluid communication with the fluid conduit line;a valve including a valve seat coupled to the housing and a valve element movable relative to the valve seat between an opened position wherein flui

1. An apparatus for detecting a leak in a fluid conduit line, comprising: a housing configured to be in fluid communication with the fluid conduit line;a valve including a valve seat coupled to the housing and a valve element movable relative to the valve seat between an opened position wherein fluid is permitted to flow through the valve, and a closed position wherein fluid is prevented from flowing through the valve, the valve seat including a barrel extending along a length and the valve element including a piston configured to slidingly engage the barrel along the length, whereby the valve element remains in the closed position while the piston slidingly engages the barrel for small movements of the valve element until the piston no longer engages the barrel and the valve element reaches the opened position;a bypass line having a first end in fluid communication with a first side of the valve and a second end in fluid communication with a second side of the valve;a fluid flow detector operatively coupled to the bypass line and configured to detect the flow of fluid therethrough; anda mechanism configured to provide a return force on the valve element when the valve element is immersed in the fluid flowing through the fluid conduit line, the return force configured to urge the valve element toward the closed position, wherein the return force decreases as the valve element is moved away from the closed position. 2. The apparatus of claim 1, wherein the mechanism includes a first magnetic member and a second magnetic member, and wherein the return force is a magnetic attraction force between the first magnetic member and the second magnetic member. 3. The apparatus of claim 2, wherein the magnetic attraction force is between approximately 0.0625 lbf and approximately 1.0 lbf in the opened position. 4. The apparatus of claim 2, wherein the mechanism is configured so the magnetic attraction force maintains the valve element in the closed position until a threshold pressure drop across the valve element is reached. 5. The apparatus of claim 4, wherein the first magnetic member is coupled to the valve element and the second magnetic member is coupled to the housing, the first and second magnetic members being in proximity to each other when the valve element is in the closed position. 6. The apparatus of claim 5, wherein each of the first and second magnetic members may be selected from the group consisting of a permanent magnet, an electromagnet, a ferromagnetic material, a ferrimagnetic material, and a paramagnetic material. 7. The apparatus of claim 5, wherein the first magnetic member includes a portion of the valve element formed of a ferromagnetic material, a ferrimagnetic material, or a paramagnetic material, and the second magnetic member includes a permanent magnet. 8. The apparatus of claim 4, wherein the threshold pressure drop for causing the valve element to move away from the closed position is between approximately one-half (0.5) psi and approximately five (5) psi. 9. The apparatus of claim 1, further comprising: a sensor coupled to one of the housing and the valve element configured to detect when the valve element is in the closed position. 10. The apparatus of claim 1, wherein the fluid flow detector includes a thermal flow detector. 11. An apparatus for detecting a leak in a fluid conduit line, comprising: a housing having an inlet, an outlet, and an interior cavity;a valve disposed at least in part in the interior cavity between the inlet and outlet, the valve including a valve seat coupled to the housing and a valve element movable relative to the valve seat between an opened position wherein fluid is permitted to flow through the valve, and a closed position wherein fluid is prevented from flowing through the valve, the valve seat including a barrel extending along a length and the valve element including a piston configured to slidingly engage the barrel along the length, whereby the valve element remains in the closed position while the piston slidingly engages the barrel for small movements of the valve element until the piston no longer engages the barrel and the valve element reaches the opened position;a bypass line having a first end in fluid communication with a first side of the valve and a second end in fluid communication with a second side of the valve;a fluid flow detector operatively coupled to the bypass line and configured to detect the flow of fluid therethrough;a single mechanism configured both to urge the valve element toward the closed position and to maintain the valve element in the closed position until a threshold pressure drop across the valve element is reached, wherein the mechanism comprises a first magnetic member and a second magnetic member and the mechanism is the sole mechanism urging the valve element toward the closed position and maintaining the valve element in the closed position until a threshold pressure drop across the valve element is reached. 12. The apparatus of claim 11, wherein the mechanism is configured to provide a magnetic attraction force on the valve element when the valve element is immersed in the fluid flowing through the fluid conduit line. 13. The apparatus of claim 12, wherein the magnetic attraction force provided by the mechanism is between approximately 0.0625 lbf and approximately 1.0 lbf. 14. The apparatus of claim 11, wherein the first magnetic member is coupled to the valve element and the second magnetic member is coupled to the housing. 15. The apparatus of claim 11, wherein the mechanism provides a variable force on the valve element. 16. The apparatus of claim 15, wherein the mechanism provides a magnetic attraction force on the valve element when in the closed position having a magnitude, the magnitude of the magnetic attraction force decreasing as the valve element moves toward the opened position. 17. The apparatus of claim 15, wherein the magnetic attraction force provided by the mechanism is non-negligible when the valve element is in the opened position. 18. A dispensing system, comprising: a tank for holding a liquid;a dispensing unit for dispensing the liquid;a fluid conduit line providing fluid communication between the tank and the dispensing unit; anda leak detector in fluid communication with the fluid conduit line and configured to detect a leak therein, the leak detector comprising: a housing having an inlet, an outlet, and an interior cavity;a valve disposed at least in part in the interior cavity between the inlet and outlet, the valve including a valve seat operatively coupled to the housing and a valve element movable relative to the valve seat between an opened position wherein liquid is permitted to flow through the valve, and a closed position wherein liquid is prevented from flowing through the valve, the valve seat including a barrel extending along a length and the valve element including a piston configured to slidingly engage the barrel along the length, whereby the valve element remains in the closed position while the piston slidingly engages the barrel for small movements of the valve element until the piston no longer engages the barrel and the valve element reaches the opened position;a bypass line having a first end in fluid communication with a first side of the valve and a second end in fluid communication with a second side of the valve;a fluid flow detector operatively coupled with the bypass line and configured to detect the flow of liquid therethrough;a mechanism configured to provide a return force on the valve element when the valve element is immersed in the fluid flowing through the fluid conduit line, the return force configured to urge the valve element toward the closed position, wherein the return force decreases as the valve element is moved away from the closed position. 19. The dispensing system of claim 18, wherein the mechanism includes a first magnetic member and a second magnetic member. 20. The dispensing system of claim 19, wherein the first magnetic member is coupled to the valve element and the second magnetic member is coupled to the housing, the first and second magnetic members being in proximity to each other when the valve element is in the closed position.