Emergency release system

The present invention relates to an emergency release system for safely releasing a connection between an end of a fluid transfer hose and a fixed pipe at an elevated position, the fluid transfer hose being a hose via which a fluid is transferred between a first navigation installation and a second navigation installation, at least one of the first and second installation being a fluid carrier vessel carrying the fluid, the emergency release system comprising an emergency release connector which comprises a first end part which is connected to the end of the fluid transfer hose and a second end part which is connected to the fixed pipe and has releasing means for releasing the connection upon receipt of an emergency signal, a wire wound onto a rotatable drum and connected to the emergency release connector, the wire being provided for being unwound from the drum upon release of the emergency release connector so that the emergency release connector falls from the elevated position of the fixed pipe to a lower position.

It is known to use a fluid transfer system to transfer a fluid from one navigation installation to another, whereby the navigation installation may be an onshore or offshore installation.

EP-A-1710206 describes for instance a fluid transfer system for transferring a fluid product between a vessel carrying a fluid and an off-shore fixed installation provided for storing and further handling of the fluid. The transfer system comprises a connection device, which is with one end connectable to a manifold of the vessel, and with another end connectable to a first end of a flexible transfer hose leading to the off-shore installation.

It is further known to provide the fluid transfer

system with an emergency release system (ERS), which is provided for quickly disconnecting one end of the hose in case of emergency, for instance in case of a sudden storm.

In EP-A-1710206 the emergency release system comprises a fall-braking device for braking the fall of the free end of the flexible transfer hose upon release of the connection device in an emergency disconnection. However, the fall-braking device described in EP-A-1710206 is not able to control the speed of the flexible transfer hose throughout its entire fall, nor is it able to ensure that the hose end reaches its lowest position. Controlling the speed of the flexible transfer hose throughout the fall is of particular importance in off-shore ship-to- ship transfers, where weather conditions may vary and, without due control of the falling speed, cause the flexible transfer hose to clash against the vessel upon release of the connection device or throughout its fall down.

It is therefore an object of the present invention to provide an emergency release system which ensures a safe release of the fluid transfer pipe between off-shore as well as on-shore navigation installations. This is achieved according to the present invention with an emergency release system showing the technical features of the first claim.

With the term fluid as used herein is meant any liquid, gas, smoke, aerosol, flowing solid or any mixture thereof or any other flowing medium known to the person skilled in the art. In particular, the fluid can be liquid natural gas.

The first and/or the second navigation installation may be off-shore or on-shore installations. At least one of the first and/or second navigation installations is a vessel carrying the fluid to be transported, hereinafter called the unloading vessel. The other navigation installation may be another vessel, hereinafter called the

receiving vessel, or a fixed installation provided to receive and/or further treat or transport the fluid.

During the unwinding of the wire, the emergency release connector, together with the disconnected end of the hose which is connected to the emergency release connector, falls from an elevated position to a lower position as a result of gravity.

The emergency release system according to the present invention comprises a speed controlling unit associated with the drum and provided for controlling the rotation speed of the drum during unwinding of the wire from the drum. Such a speed controlling unit is needed in order to avoid the disconnected end from clashing against the first or second navigation installation throughout its fall, and at the same time enabling a quick disconnection between the first and second navigation installation if needed. A rotation speed of the drum which is too high usually happens in the beginning of the fall, where the load on the drum is high, causing the drum to rotate fast. A high rotation speed may cause the disconnected end to clash against on of the first and second navigation installations. During the fall, the load on the drum decreases gradually, decreasing the rotation speed of the drum. However, the rotation speed cannot be too low either, because this could cause a slowdown of the unwinding of the wire from the drum, which again could slowdown the complete separation between the two navigation installations. In fact, the decrease of the load on the drum could even result in a stop of the unwinding process before the disconnected end has reached his lower position. This is not desired.

To control the rotation speed of the drum and avoid that it becomes too high or low, the speed controlling unit is designed such that it is capable of limiting the rotation speed of the drum on the one hand, and maintaining rotation of the drum until the disconnected end of the hose has reached its lower position.

The emergency release system has the advantage that it allows a safe and complete disconnection of the fluid transfer hose in off-shore as well as on-shore conditions, by controlling the fall of the disconnected end of the hose throughout its entire fall and ensuring that the lower position is reached in a short period of time.

In a preferred embodiment, the speed controlling unit is a passive unit, meaning that it does not need to be powered or activated for adjusting the speed. This ensures a safe disconnection without damage to one of the installations, even if the speed of the disconnected end should suddenly increase during its fall, for instance as a result of a sudden wind or movement of one of the installations.

Preferably, a predetermined inertia is built into the speed controlling unit by means of a mass of movable material, for initially slowing down the rotation speed and subsequently maintaining a given rotation speed. The mass of movable material can for example be achieved with a liquid circulating in a closed circuit comprising a circulation pump and possibly a flow control system for additional control of the circulation speed through the closed circuit. The mass of movable material can for example also be achieved with a flywheel having a predetermined weight.

Preferably, the speed controlling unit is designed in a way to ensure a more or less constant speed throughout the complete duration of the fall of the hose end. At the end of the fall of the hose, when the hose reaches its lower position, the wire may be completely unwound from the drum or some wire may remain on the drum. Whether or not this is the case, depends for instance on the height of the installation to which the hose is connected to and on the space between the two installations at the time the emergency release connector is activated. In case some wire remains on the drum after the fall, the wire may start

pulling again at changing distance between the two installations, which is not desired. In order to avoid this and allow complete separation of the two navigation installations, the emergency release system preferably comprises a release member associated with the wire and provided to release the wire from the drum when the emergency release connector reaches the lower position.

The invention will be further elucidated by means of the following description and the appended drawings.

Figure 1 shows a schematic view of an emergency release system used during a fluid transfer between two ships in a side-by-side configuration.

Figure 2 shows a schematic view of a preferred embodiment of a speed controlling unit of an emergency release system according to the present invention. Figure 3 shows part of the speed controlling unit of figure 2 integrated into a protection saddle on which a fluid transfer hose is to be placed.

The emergency release system of the present invention is in particular suitable for use in fluid transfer systems in which a fluid is transferred from one ship to another in a side-by-side configuration as is shown in figure 1. During transfer of the fluid, the hoses hang freely between the two ships 4, 5, hereby forming a U.

The fluid transfer system may comprise one fluid hose 1 , with a large diameter, but preferably comprises a number of fluid transfer hoses with smaller diameter because these smaller hoses are easier to handle. The hoses 1 are connected with one end to the supply fluid line of the unloading installation or unloading ship 4 and with the other end to the receiving fluid line of the receiving installation or receiving ship 5 or vice versa. In order to accommodate the use of smaller hoses, the connection of these hoses is usually done with Y- spool pieces or reducers, but any other manifold known to the person

skilled in the art may be used. The hoses are preferably placed with their ends on protection saddles 13 ensuring, on the one hand, a correct positioning of the hoses with respect to the manifold used to connect the hoses to the supply and the receiving fluid line, and, on the other hand, an acceptable 90°- bending radius for the curved part of the hose between horizontal part (part connected to the manifold) and vertical part (part hanging overboard).

As shown in figure 1 , the emergency release system according to the present invention comprises an emergency release connector 6 , a wire 7 and drum 8 and a speed controlling unit 9.

The emergency release connector 6 is, in a non-emergency situation, with a first end part connected to an end 2 of a fluid transfer hose 1 and with a second end part connected to a fixed pipe 3 of the second navigation installation 5, which is for instance the receiving fluid pipe of a receiving ship. The emergency release connector

6 is further connected to a wire 7 which is wound on a drum 8. The wire 7 is with one end connected to the emergency release connector 6 and with another end to the drum 8.

Upon receipt of an emergency signal, the emergency release connector 6 of the fluid transfer pipe 1 is activated and disconnects the hose 1 from the fixed pipe 3 of the second navigation installation 5, enabling the hose 1 to fall down. During the fall, the wire 7 is unwound from the drum 8. The speed controlling unit 9, associated with the drum 8, is provided to control the speed of this unwinding process. As such, the speed controlling unit 9 is able to control the speed of the hose 1 falling down throughout the complete duration of the fall of the hose end 2.

A first embodiment of the speed controlling unit 9 of the ERS according to the present invention is shown in figure 2. The speed controlling unit 9 comprises a hydraulic pump 10, which is connected to the drum 8 with for instance a gear, and works in a closed

circuit. The closed circuit further comprises a flow controller 12, designed to keep the flow in the closed circuit substantially constant. To this end the flow controller 12 controls the diameter of an orifice of a control valve 11 through which a fluid is pushed by the hydraulic pump 10. Upon receipt of an emergency signal, the emergency release connector 6 will disconnect one end 2 of the hose 1 from the second navigation installation 5. In the beginning of the fall of the hose 1 , the weight of the part hanging to the drum 8 is high, resulting in a high flow rate of fluid pushed out of the hydraulic pump 10. As a reaction, the flow controller 12 will narrow the orifice 11 through which the fluid is to be pushed, resulting in a higher resistance and a decrease of the flow rate. During the fall, the load on the drum 8 and speed controlling unit 9 decreases because one end of the hose 1 remains fixed to the ship 4 and the weight of the part hanging to the drum decreases gradually during the fall, resulting in a decrease of the flow rate of fluid pushed out of the hydraulic pump 10. As a reaction, the flow controller 12 will cause the orifice 11 to open, resulting in a low resistance and an increase of the flow rate.

Such a system has the advantage that the rotation speed of the drum 8 is automatically adjusted if necessary, without the need to power the ERS.

Optionally, the ERS further comprises a pressure vessel 15 which is provided to compensate for pressure variations due to thermal expansion of the fluid and/or the hydraulic block. This temperature independency is in particular important in the case liquid natural gas is being transferred.

Optionally, the emergency release system further may comprise a manual valve 14 for roughly manually adjusting the flow. Summarizing, the speed controlling unit 9 ensures a more or less constant speed throughout the complete duration

of the fall by varying the pressure loss in the closed circuit. As a result, it can be avoided that the disconnected hose end 2 clashes against one of the installations during its fall, for instance as a result of a sudden wind storm. In fact, in case the hose end 2 would encounter a sudden wind storm during its fall, causing an increase of the flow rate, the flow controller 12 would immediately narrow the orifice of the control valve 11 , resulting in a decrease of the flow rate and a decrease of the unwinding process. Another advantage is that, because the speed of the disconnected hose end 2 is controlled throughout its complete fall, it can be assured that its fall is not stopped before it reaches its lowest position.

Its lowest position is preferably straight downwards along the side of the first installation 4 between the unloading 4 and the receiving ship 5.

A second embodiment of the speed controlling unit 9 of the ERS comprises a flywheel connected to the drum 8 on which the wire 7 is wound. A flywheel is a wheel with a high weight and thus a high inertia. Because of the high weight, a high force is needed to make the wheel turning. At the same time a high force is needed to slow down the flywheel. In case of emergency the emergency release connector 6 of each hose 1 is activated and disconnects the hose 1 from the second installation 5. As the disconnected end 2 drops, it pulls the wire 7 from the drum 8, making the flywheel turn at a slowly increasing speed. When the disconnected end 2 has dropped over a given distance, the pulling force on the wire 7 becomes too small to further increase the rotation speed of the flywheel. Now, the flywheel starts to drive the drum 8, so that it can be ensured that the disconnected end 2 further drops at a controlled speed until it hangs straight downwards and free.

The emergency release disconnection of the hose 1 preferably results in an automatic closing of the hose 1 and/or the manifold it was connected to. This simultaneous and immediate closing prevents any of the fluid from being spilled. To this end the speed controlling unit 9 is preferably combined with a mechanical interlock that

automatically shuts down the transfer of the fluid between the two installations 4, 5. This is arranged by communicating the emergency release signal to the emergency shut down system on board of the discharging facility. This emergency shut down will then shut down the fluid transfer equipment, such as pumps. In the same time, the manifold valves will be closed by this emergency shut down system. The emergency shut down on the discharging facility should preferably be connected to the emergency shut down system on the receiving facility. An emergency shut down on the discharging facility will in this case also initiate the closing of the manifold valves on the receiving facility. The purpose of this chain of events is to stop adding any fluid into the hose while it is being disconnected and released in a controlled manner. The inventory of the fluid is thus being contained and limited as much as possible to its safest containment system, being the discharging and receiving facility tanks or holds.

In order to avoid that some wire remains on the drum 8 after the fall and would start pulling again, a release member is preferably associated with the wire. The release member may for instance take the form of a clutch which is additionally provided between the drum and the gear. The clutch may be activated manually or remotely. The end of the wire may then be clipped on the drum and be released from the de-clutched drum at the slightest pull as can be seen on figure 1 - step 3.

A preferred embodiment of the ERS is shown in figure 3. In this figure it is shown that the emergency release system

(which is only partly shown) is integrated in the protection saddles 13 onto which the fluid transfer hose 1 is placed. This makes the ERS very compact and easy to install.