JP7825985B2 - Floating structures - Google Patents

Description

This disclosure relates to a floating structure equipped with a liquefied gas tank.

Floating structures that float on water have limited areas for installing equipment, etc., compared to structures on land, and have less freedom in design. Furthermore, if the floating structure is equipped with a liquefied gas tank for storing liquefied flammable gas, design freedom is further reduced from a safety standpoint (see, for example, Patent Document 1 below).

JP 2016-120814 A

The present disclosure aims to provide a floating structure equipped with a liquefied gas tank for storing liquefied flammable gas, which offers a high degree of design freedom.

A floating structure according to one aspect of the present disclosure comprises a liquefied gas tank that stores liquefied flammable gas and is strong enough to eliminate the need for a secondary barrier, a tank cover that covers the liquefied gas tank, and non-explosion-proof electrical equipment located on the surface of the tank cover.

The above configuration provides a floating structure equipped with a liquefied gas tank for storing liquefied flammable gas, allowing for a high degree of design freedom.

FIG. 1 is a schematic side view of a floating structure. FIG. 2 is a schematic plan view of the floating structure.

The floating structure 100 according to the embodiment will now be described. Figure 1 is a schematic side view of the floating structure 100, and Figure 2 is a schematic plan view of the floating structure 100. As shown in Figure 1, the floating structure 100 according to the present embodiment comprises a hull 10, a liquefied gas tank 20, a tank cover 30, a flying passage 40, and a relay device 50. These components will now be described in order.

<Hull>
The floating structure 100 according to this embodiment is a liquefied gas carrier that transports liquefied gas, and is equipped with a navigable hull 10. The concept of direction in the following description corresponds to the concept of direction when viewed in the direction in which passengers on the floating structure 100 are sailing (to the right on the paper in Figures 1 and 2). In the following, the fore-and-aft direction of the hull 10 will be referred to as the "longitudinal direction," the front end portion as the "bow," and the rear end portion as the "stern."

The stern of the hull 10 is located the accommodation area 11 where workers live or work. A control device that controls the floating structure 100 is installed in the accommodation area 11. The control device receives measurement signals from measuring instruments installed in various locations on the hull 10 and transmits control signals to operating instruments installed in various locations on the hull 10. Power supply equipment is also installed in the accommodation area 11. The power supply equipment supplies power to the instruments (including the measuring instruments and operating instruments) installed in various locations on the hull 10. Note that, although the accommodation area 11 is located in the stern of the hull 10 in this embodiment, the location of the accommodation area 11 is not limited to this.

As described above, the floating structure 100 according to this embodiment is a liquefied gas carrier. However, the floating structure 100 is not limited to a liquefied gas carrier, and may also be a floating production storage and offloading unit (FPSO), a floating LNG storage and regasification unit (FSRU), a floating production and offloading unit (FPO), a floating storage and offloading unit (FSO), etc.

<Liquefied gas tank>
The liquefied gas tank 20 is a tank that stores liquefied gas obtained by liquefying flammable gas. Examples of the liquefied gas include liquefied hydrogen, liquefied natural gas (LNG), and liquefied petroleum gas (LPG). The floating structure 100 according to this embodiment includes four liquefied gas tanks 20. The liquefied gas tanks 20 are spherical or ellipsoidal and are aligned in the longitudinal direction. However, the number, shape, and arrangement of the liquefied gas tanks 20 are not limited to those described above.

A dome portion 21 that protrudes upward is formed at the top of the liquefied gas tank 20. Pipes that connect the inside and outside of the liquefied gas tank 20 pass through the dome portion 21. Furthermore, if a sensor is placed inside the liquefied gas tank 20, the wiring extending from the sensor passes through the dome portion 21. In other words, the dome portion 21 functions as a connection point between the liquefied gas tank 20 and other facilities and equipment. For this reason, electrical equipment tends to be concentrated around the dome portion 21.

Here, tanks that store liquefied flammable gas are classified into three types based on their strength. The first type is a tank that requires a secondary barrier that surrounds the entire tank (complete secondary barrier). The "secondary barrier" here refers to a wall that contains liquefied gas that leaks from the tank in the event of a tank rupture. The second type is a tank that is stronger than the first type, but requires a partial secondary barrier (partial secondary barrier). The third type is a tank that is stronger than the second type, but does not require a secondary barrier.

The above-mentioned types 1, 2, and 3 correspond to types A, B, and C, respectively, as defined by the International Maritime Organization (IMO). The liquefied gas tank 20 of this embodiment belongs to the third type of the above-mentioned three types. In other words, the liquefied gas tank 20 of this embodiment is a tank strong enough that a secondary barrier is not required.

<Tank cover>
The tank cover 30 is a member that covers the liquefied gas tank 20. The floating structure 100 according to this embodiment is provided with four tank covers 30. Each tank cover 30 is hemispherical and covers a corresponding liquefied gas tank 20. Strictly speaking, the tank cover 30 covers the liquefied gas tank 20 except for the dome portion 21. The hold space 31 of the hull 10 in which the liquefied gas tank 20 is located is covered by this tank cover 30 and the deck 32. The shape of the tank cover 30 is not limited to that described above.

Here, each area of the floating structure 100 is divided into a hazardous area and a non-hazardous area. A hazardous area is an area where non-explosion-proof electrical equipment cannot be installed, while a non-hazardous area is an area where non-explosion-proof electrical equipment can be installed. As mentioned above, the liquefied gas tank 20 of this embodiment is strong enough that a secondary barrier is not required. Therefore, the surface of the tank cover 30, excluding the area around the dome portion 21, can be considered a non-hazardous area.

As a result, according to this embodiment, electrical equipment that cannot be explosion-proof can be placed on the surface of the tank cover 30, and non-explosion-proof electrical equipment, which is smaller in size than explosion-proof electrical equipment, can be placed on the surface of the tank cover 30. Therefore, according to this embodiment, the degree of freedom in designing the floating structure 100 can be improved. Note that "on the surface of the tank cover 30" includes not only positions that are in contact with the surface of the tank cover 30, but also positions that are close to and above the surface of the tank cover 30.

<Flying Passage>
The flying passage 40 is a passageway that passes over the surfaces of the tank covers 30 and is usable by people. In this embodiment, the flying passage 40 extends horizontally forward from the accommodation area 11 and passes over the surfaces of the four tank covers 30. The tip of the flying passage 40 is connected to a staircase 41 that extends toward the deck 32 in the bow.

Furthermore, electrical wiring 42 is arranged along flying passage 40. In other words, electrical wiring 42 is arranged adjacent to flying passage 40 and extends longitudinally. Within electrical wiring 42, signal cables are housed, such as those for the control device installed in living area 11 to receive signals from each device, those for transmitting signals from the control device to each device, and power cables for supplying power from the power supply equipment installed in living area 11 to each device.

<Relay device>
The relay device 50 is an electrical device located at an intermediate position in a system for transmitting information or energy. The relay device 50 of this embodiment is not explosion-proof and is located on the surface of the tank cover 30. Specifically, the relay device 50 is housed in an electrical device chamber 51 located on the electrical path 42.

Furthermore, the electrical equipment room 51 is located on the electrical circuit 42 adjacent to the flying passage 40. Therefore, the relay device 50 housed in the electrical equipment room 51 is accessible from the flying passage 40. As a result, workers can easily perform maintenance on the relay device 50 from the flying passage 40. Note that the relay device 50 does not have to be housed in the electrical equipment room 51 located on the electrical circuit 42. However, it is desirable that the relay device 50 be located within 1 m of the flying passage 40. By locating the relay device 50 in this manner, the relay device 50 can be accessed from the flying passage 40. However, if the relay device 50 or the electrical equipment room 51 is more than 1 m away from the flying passage 40, an access means such as stairs may be provided in the flying passage 40 to allow workers to access the relay device 50 or the electrical equipment room 51.

The relay device 50 in this embodiment includes a gas sensor, a branch junction box, a remote I/O unit, and a barrier for intrinsically safe explosion-proof equipment.

The above-mentioned gas sensor is a sensor that detects flammable gas from gas collected via a conduit. In this embodiment, gas around the dome section 21 is collected via a conduit, and the gas sensor detects whether the gas contains flammable gas. For example, if the surface of the tank cover 30 is a hazardous area and the gas sensor is located in the living area 11, it would be necessary to run a conduit from around the dome section 21 to the living area 11. In contrast, in this embodiment, because the gas sensor is located on the surface of the tank cover 30, there is no need to run a conduit all the way to the living area 11, and the length of the conduit can be shortened.

The branch junction box described above is a device that includes a power circuit breaker or power switch. The branch junction box has the function of supplying power obtained from one power cable to each electrical device via multiple power cables. For example, if the surface of the tank cover 30 is a hazardous area and the branch junction box is located in the living area 11, it would be necessary to run multiple power cables from each device to the living area 11. In contrast, in this embodiment, because the branch junction box is located on the surface of the tank cover 30, the number of power cables from the branch junction box to the living area 11 can be reduced. As a result, the overall length of the power cables can be shortened.

The remote I/O unit described above is a unit that converts signals received from multiple devices, such as gas sensors, into a single signal and transmits it. For example, if the surface of the tank cover 30 is a hazardous area and the remote I/O unit is located in the living area 11, it would be necessary to run numerous signal cables from each device to the living area 11. In contrast, in this embodiment, because the remote I/O unit is located on the surface of the tank cover 30, the number of signal cables from the remote I/O unit to the living area 11 can be reduced. As a result, the overall length of the signal cables can be shortened.

The above-mentioned intrinsically safe explosion-proof equipment barrier is a device that limits the energy supplied to electrical equipment installed in the danger zone (in this embodiment, the sensor installed around the dome portion 21) and suppresses the generation of sparks that could lead to ignition in the danger zone. For example, if the surface of the tank cover 30 is the danger zone and the intrinsically safe explosion-proof equipment barrier is installed in the accommodation area 11, a cable connecting the sensor to the intrinsically safe explosion-proof equipment barrier would need to be installed from the periphery of the dome portion 21 to the accommodation area 11. In contrast, in this embodiment, because the intrinsically safe explosion-proof equipment barrier is installed on the surface of the tank cover 30, the length of the cable connecting the sensor to the intrinsically safe explosion-proof equipment barrier can be shortened. Furthermore, because the cable connecting the sensor to the intrinsically safe explosion-proof equipment barrier is more expensive than a regular cable, this embodiment reduces the manufacturing costs of the floating structure 100.

In this embodiment, the relay device 50 is located at a position corresponding to the top of the tank cover 30. In other words, the relay device 50 is located at the same longitudinal position as the top of the corresponding tank cover 30. As mentioned above, electrical equipment is concentrated around the dome portion 21, so by locating the relay device 50 at a position corresponding to the top of the tank cover 30, the conduit or cable connected to the relay device 50 can be effectively shortened.

<Modification>
The floating structure 100 according to this embodiment has been described above. In this embodiment, the case where the relay device 50 is located on the surface of the tank cover 30 has been described, but electrical devices other than the relay device 50 may be arranged on the surface of the tank cover 30. For example, a solar power generation system including a solar power generation panel, a power conditioner, and a battery may be arranged on the surface of the tank cover 30.

<Summary>
As described above, the floating structure of this embodiment comprises a liquefied gas tank that stores liquefied flammable gas and is strong enough to not require a secondary barrier, a tank cover that covers the liquefied gas tank, and non-explosion-proof electrical equipment located on the surface of the tank cover.

This configuration allows electrical equipment that cannot be explosion-proof to be placed on the surface of the tank cover, and also allows non-explosion-proof electrical equipment, which is smaller in size than explosion-proof equipment, to be placed on the surface of the tank cover. Therefore, the above configuration increases the degree of freedom in the design of floating structures.

In addition, the floating structure of this embodiment further includes a flying passage that passes over the surface of the tank cover and is accessible to people, and the electrical equipment is located in a position accessible from the flying passage.

With this configuration, the electrical equipment is located in a position that is accessible from the flying passage, allowing workers to easily perform maintenance on the electrical equipment from the flying passage.

In addition, in the floating structure according to this embodiment, the electrical equipment is relay equipment including at least one of a gas sensor that detects flammable gas from the gas collected through a conduit, a branch connection box including a power circuit breaker or power switch, a remote I/O unit that converts signals received from multiple devices into a single signal and transmits it, and a barrier for intrinsically safe explosion-proof equipment.

By positioning the relay device as described above on the surface of the tank cover, the conduit or cable connected to the relay device can be shortened.

Furthermore, in the floating structure according to this embodiment, the relay device is located at a position corresponding to the top of the tank cover.

Electrical equipment tends to be concentrated around the top of the tank cover. Therefore, by positioning the relay device in a position corresponding to the top of the tank cover, the conduit or cable connected to the relay device can be effectively shortened.

Furthermore, in the above-mentioned floating structure, the electrical equipment may be a solar power generation system including a solar power generation panel, a power conditioner, and a battery.

This configuration allows for effective use of the surface of the tank cover.

10 Hull 11 Living quarters 20 Liquefied gas tank 21 Dome section 30 Tank cover 31 Hold space 32 Deck 40 Flying passage 41 Staircase 42 Electrical circuit 50 Relay equipment (electrical equipment)
51 Electrical equipment room 100 Floating structure

Claims (3)

a liquefied gas tank that stores liquefied flammable gas and has strength that does not require a secondary barrier;
a tank cover that covers the liquefied gas tank;
and non-explosion-proof electrical equipment located on the surface of the tank cover ,
The floating structure, wherein the electrical equipment is relay equipment including at least one of a gas sensor that detects flammable gas from gas collected through a conduit, a branch connection box including a power circuit breaker or a power switch, a remote I/O unit that converts signals received from multiple devices into a single signal and transmits it, and a barrier for intrinsically safe explosion-proof equipment . The floating structure according to claim 1 , wherein the relay device is located at a position corresponding to a top of the tank cover. The floating structure is a liquefied gas carrier,
an electric circuit arranged to extend in the longitudinal direction of the hull of the liquefied gas carrier;
The floating structure according to claim 1 or 2, wherein the relay device is accommodated in an electrical equipment room located on the electrical line.