Loading assembly for conveying a pressurized gas stream and a switching system for use in a loading assembly

1. A loading assembly for conveying a pressurized gas stream between a floating structure and another structure that is located adjacent to the floating structure, the loading assembly comprising:

a gas conduit adapted to extend between the floating structure and the other structure, to convey a pressurized gas stream between the two structures;

an emergency disconnection coupler configured in the gas conduit for establishing a selectively connectable and disconnectable gas connection between the floating structure and the other structure through the gas conduit, and wherein the emergency disconnection coupler comprises an actuating coupling that is selectively switchable between a locked position and an unlocked position, whereby in said locked position the gas connection is established and whereby in said unlocked position the gas connection is interrupted whereby the actuating coupling physically disengages when the actuating coupling is in the unlocked position;

a switching system configured to control the switching of the actuating coupling in the emergency disconnection coupler between the locked position and the unlocked position, wherein the switching system is adapted to be responsive to two distinct fail-safe regimes contingent upon an internal gas pressure in the gas connection:

a fail-unlocked regime when the internal gas pressure in the gas connection is below a preselected override threshold value, which sets the switching system to unlock the actuating coupling upon power loss, and

a fail-locked regime which sets the switching system to lock the actuating coupling when the internal gas pressure in the gas connection is at or above the preselected override threshold value,

the switching system comprising:

a selection switch functionally coupled to the actuating coupling to control switching of the actuating coupling between said locked position and unlocked position at least when the switching system is in said fail-unlocked regime; and

an override switch having an override position that is activated by the internal gas pressure, and a release position, wherein the override switch is forced in the override position when the internal gas pressure is at or above the preselected override threshold value, in which case the pressure gate overrides the selection switch whereby, regardless of whether the selection switch is in open state or in closed state, the actuating coupling is instructed to assume the locked position, and wherein movement of the actuating coupling from said locked position to said unlocked position can only proceed when said internal gas pressure is below said preselected override threshold value and the override switch is not activated, wherein the override switch is part of a pressure gate that is driven by the internal gas pressure within the gas connection.

2. The loading assembly of claim 1 , wherein the selection switch has an open state and a closed state whereby upon selecting the open state the actuating coupling is instructed to assume the unlocked position and whereby upon selecting the closed state the actuating coupling is instructed to assume the locked position, wherein the selection switch is a fail-open switch.

3. The loading assembly of claim 1 , wherein the override switch is in fluid communication with the gas connection via a gate line, whereby the override switch is physically forced into the override position by the internal gas pressure in the gas connection, and into the release position by a bias force directed against said internal gas pressure.

4. The loading assembly of claim 1 , wherein the actuating coupling comprises a hydraulically powered actuator powered by a hydraulic fluid that is circulated through a hydraulic circuit by a hydraulic power unit from a pressure source to a tank,

wherein the hydraulically powered actuator comprises a first hydraulic communication port through which the hydraulic fluid can pass and a second hydraulic communication port through which the hydraulic fluid can pass,

wherein a positive pressure differential between the first hydraulic communication port and the second hydraulic communication port causes a driving force on the actuating coupling directed from the unlocked position towards the locked position, and wherein a negative pressure differential between the first hydraulic communication port and the second hydraulic communication port causes an opposite driving force on the actuating coupling directed from the locked position to the unlocked position.

5. The loading assembly of claim 4 , wherein the pressure source comprises a pump and an accumulator, wherein the accumulator is sized to hold a sufficient amount of hydraulic fluid under sufficient pressure to force the actuating coupling from the unlocked into the locked position when the hydraulic fluid is released from the accumulator.

6. The loading assembly of claim 4 , wherein the selection switch comprises a first directional control valve configured in the hydraulic circuit between the first hydraulic communication port and the second hydraulic communication port on one side and the hydraulic power unit on another side, wherein the first directional control valve comprises at least two positions, whereby one of the at least two positions corresponds to the open state and another one of the at least two positions corresponds to the closed state, wherein the first directional control valve is moved into its closed state upon applying actuation power, wherein the first directional control valve is biased to move towards the open state upon loss of actuation power.

7. The loading assembly of claim 6 , wherein the override switch comprises a second directional control valve and a third directional control valve, which second directional control valve and third directional control valve are simultaneously movable, wherein the override switch is biased in a direction against the internal gas pressure.

8. The loading assembly of claim 7 , wherein the override switch comprises a pneumatic actuator that transfers the internal gas pressure into movement of the override switch in an override position when the internal gas pressure is at or above the preselected override threshold value, and wherein the bias imposes movement of the override switch out of the override position.

9. The loading assembly of claim 6 , wherein the loading assembly comprises a backup hydraulic circuit, a backup hydraulic power unit in addition to the hydraulic circuit and the hydraulic power unit, and

wherein the selection switch comprises a backup first directional control valve, and

wherein the override switch comprises a backup second directional control valve and a backup third directional control valve, all in addition to the first directional control valve, the second directional control valve and the third directional control valve, and

wherein the backup hydraulic circuit, the backup first directional control valve, the backup second directional control valve and the backup third directional control valve are configured relative to the backup hydraulic power unit and the actuating coupling, in functionally the same way as the hydraulic circuit, the first directional control valve, the second directional control valve and the third directional control valve are configured relatively to the hydraulic power unit and the actuating coupling, and

wherein the first directional control valve and the first backup directional control valve are mechanically coupled and actuated with the same actuation power as the first directional control valve,

whereby the first directional control valve and the first backup directional control valve are forced to assume mutually the same positions, and

wherein the second directional control valve and the third directional control valve and the backup second directional control valve and the backup third directional control valve are all mechanically coupled to each other whereby they are simultaneously movable, and

wherein the hydraulic circuit comprises at least two rupture protection valves and the backup hydraulic circuit comprises at least two backup rupture protections valves, each rupture protection valve and backup rupture protection valve comprising a snap position valve, configured to snap to close when a pressure differential across the snap position valve exceeds a predetermined safety limit,

wherein in the hydraulic circuit a first of the at least two rupture protection valves is located between the first hydraulic communication port and the first directional control valve, and a second of the at least two rupture protection valves is located between the second hydraulic communication port and the first directional control valve, and

wherein a first of the at least two backup rupture protection valves and a second of the at least two backup rupture protection valves are located in functionally corresponding positions in the backup hydraulic circuit as their first and second rupture valves counterparts.

10. The loading assembly of claim 1 , further comprising a spool-side isolation valve and an arm-side isolation valve, both configured in the gas conduit whereby the gas connection is between the spool-side isolation valve and the arm-side isolation valve.

11. The loading assembly of claim 10 , wherein each of the spool-side isolation valve and the arm-side isolation valve and the blow down valve are biased valves whereby the blow down valve is moved in open position when the blow down valve is unpowered, and the spool-side isolation valve is moved in closed position when the spool-side isolation valve is unpowered and the arm-side isolation valve is moved in closed position when the arm-side isolation valve is unpowered.

12. The loading assembly of claim 10 , further comprising a breakaway weak link located within the gas connection between the spool-side isolation valve and the arm-side isolation valve to ensure the gas connection breaks open at a preconceived location between the spool-side isolation valve and the arm-side isolation valve, in case the mechanical load on the loading arm arrangement, caused by relative movement between the floating structure and the other structure, exceeds a predetermined limit.

13. The loading assembly of claim 10 , further comprising a blow down valve that fluidly communicates with the gas connection via a blow down junction arranged in the gas connection between the spool-side isolation valve and the emergency disconnection coupler.