Patent Description:
In conventionally used marine vessels, engines are driven using fuel liquefied from gas (hereinafter, "liquefied gas fuel"), such as LPG. In these types of marine vessels, vent gas vaporized from the residual liquefied gas fuel that has not been used in the engines is discharged from vertically provided vent posts.

In recent years, an example of such marine vessels is a marine vessel with an engine that can selectively use liquefied gas fuel and fuel oil such as heavy oil (e.g., PTL <NUM>). This type of marine vessel comprises, as shown in <FIG>, a tank <NUM> for liquefied gas fuel, a fuel supply system <NUM> that supplies the liquefied gas fuel L from the tank <NUM> to an engine <NUM>, a tank for fuel oil (not shown), and a fuel oil system (not shown) that supplies the fuel oil from the tank to the engine <NUM>. In such a marine vessel, for example, when the fuel used in the engine <NUM> is switched from the liquefied gas fuel L to the fuel oil, it is necessary to vaporize the residual liquefied gas fuel L present in the engine <NUM> and the fuel supply system <NUM>, and discharge it from a vent post <NUM>. For this purpose, a pipeline system <NUM> shown in <FIG> is used.

The pipeline system <NUM> has a drum <NUM>, a fuel pipeline <NUM>, fuel pipeline valves 103A and 103B, a heating means <NUM>, and a gas pipeline <NUM>. In the pipeline system <NUM>, while the fuel pipeline valve 103A is opened, the liquefied gas fuel L present in the fuel supply system <NUM> is guided through the fuel pipeline <NUM> into the drum <NUM>. Further, while the fuel pipeline valve 103B is opened, the liquefied gas fuel L present in the engine <NUM> is guided through the fuel pipeline <NUM> into the drum <NUM>. The heating means <NUM> is to vaporize the liquefied gas fuel L present in the drum <NUM> by heating, and vent gas G vaporized from the liquefied gas fuel L in the drum <NUM> is guided through the gas pipeline <NUM> to the vent post <NUM>, and discharged from the vent 3a of the vent post <NUM> (<FIG> and <FIG>).

In the conventional pipeline system <NUM> shown in <FIG>, the inside of the drum <NUM> is always open to the atmosphere through the gas pipeline <NUM> and the vent post <NUM>. As a result, the air pressure in the drum <NUM> is always about the same as atmospheric pressure; thus, the vent gas G vaporized in the drum <NUM> has a low temperature and a low pressure, and has a low kinetic energy. Therefore, the flow rate of the vent gas G discharged from the vent 3a of the vent post <NUM> is reduced. For this reason, as shown in <FIG>, the vent gas G discharged from the vent 3a may fall around the vent post <NUM>, and as a result, the space around the vent post <NUM> may become an explosive atmosphere.

The present invention was made in view of the above circumstances, and an object thereof is to provide a pipeline system that can discharge vent gas from the vent of a vent post at a high speed, thereby spreading the vent gas far away from the vent post to reduce the amount of the vent gas falling around the vent post; a method for discharging the vent gas using the pipeline system; and a control system that controls a valve provided in the pipeline system.

In order to achieve the above object, the present invention includes a pipeline system according to claim <NUM>, a method according to claim <NUM> and a control system according to claim <NUM>.

According to the present invention, vent gas can be discharged from the vent of a vent post at a high speed, thereby spreading the vent gas far away from the vent post to reduce the amount of the vent gas falling around the vent post.

An embodiment of the present invention is described below with reference to the accompanying drawings. <FIG> is a schematic diagram showing a pipeline system <NUM> according to the embodiment of the present invention. <FIG> is a perspective view showing a marine vessel <NUM> provided with the pipeline system <NUM>.

The pipeline system <NUM> (<FIG>) according to the embodiment of the present invention is provided in the marine vessel <NUM> (<FIG>) that discharges vent gas G vaporized from liquefied gas fuel L from a vent post <NUM>. In the present invention, the liquefied gas fuel L refers to fuel liquefied from gas, and examples of the liquefied gas fuel L include LPG (liquefied petroleum gas), LNG (liquefied natural gas), LAG (liquefied ammonia gas), and the like.

The marine vessel <NUM> (<FIG>) is provided with a tank <NUM> (<FIG>) that stores the liquefied gas fuel L, an engine <NUM> (<FIG>) that can selectively use the liquefied gas fuel L and fuel oil, a fuel supply system <NUM> (<FIG>) that can supply the liquefied gas fuel L from the tank <NUM> to the engine <NUM>, a fuel oil tank (not shown) that stores the fuel oil, and a fuel oil system (not shown) that can supply the fuel oil from the fuel oil tank to the engine <NUM>. In the marine vessel <NUM>, the liquefied gas fuel L or fuel oil is supplied to the engine <NUM>, whereby the engine <NUM> can be driven to navigate.

The fuel supply system <NUM> comprises a pump and a heat exchanger. Due to the pump, the liquefied gas fuel L present in the fuel supply system <NUM> can be supplied to the engine <NUM>, and the liquefied gas fuel L that has not been used in the engine <NUM> can be returned to the fuel supply system <NUM>. The liquefied gas fuel L present in the fuel supply system <NUM> includes the liquefied gas fuel L supplied from the tank <NUM>, and the liquefied gas fuel L returned from the engine <NUM>. Moreover, in the fuel supply system <NUM>, the temperature of the liquefied gas fuel L supplied to the engine <NUM> can be adjusted within a predetermined range by the heat exchanger.

The fuel supply system <NUM> and the engine <NUM> are each provided with a gas injection device (not shown) that injects non-combustible gas, such as nitrogen. Due to the pressure of the non-combustible gas injected from the gas injection device of the fuel supply system <NUM>, the liquefied gas fuel L present in the fuel supply system <NUM> can be pumped to the pipeline system <NUM>. Further, due to the pressure of the non-combustible gas injected from the gas injection device of the engine <NUM>, the liquefied gas fuel L present in the engine <NUM> can be pumped to the pipeline system <NUM>.

The vent post <NUM> is vertically provided on the deck of the marine vessel <NUM>, and a vent 3a for discharging the vent gas G is formed at the upper end of the vent post <NUM>.

The pipeline system <NUM> is used, for example, when the fuel used in the engine <NUM> is switched from the liquefied gas fuel L to fuel oil, to vaporize the residual liquefied gas fuel L present in the engine <NUM> and the fuel supply system <NUM>, and discharge it from the vent 3a of the vent post <NUM>.

As shown in <FIG>, the pipeline system <NUM> comprises a drum <NUM> having an interior 10b surrounded by a wall 10a, a fuel pipeline <NUM> for guiding the liquefied gas fuel L to the interior 10b of the drum <NUM>, a fuel pipeline valve <NUM> opening and closing the fuel pipeline <NUM>, a heating means <NUM> for heating the liquefied gas fuel L guided to the interior 10b of the drum <NUM> to generate vent gas G, a gas pipeline <NUM> for guiding the vent gas G present in the interior 10b of the drum <NUM> to the vent post <NUM>, and a gas pipeline valve <NUM> opening and closing the gas pipeline <NUM>.

The wall 10a of the drum <NUM> is made of carbon steel, and is excellent in pressure resistance.

The fuel pipeline <NUM> configures a system fuel pipeline <NUM> for guiding the liquefied gas fuel L present in the fuel supply system <NUM> to the interior 10b of the drum <NUM>, and an engine fuel pipeline <NUM> for guiding the liquefied gas fuel L present in the engine <NUM> to the interior 10b of the drum <NUM>. A first fuel pipeline valve 12A opening and closing the system fuel pipeline <NUM>, and a second fuel pipeline valve 12B opening and closing the engine fuel pipeline <NUM> are provided as the fuel pipeline valve <NUM>. These fuel pipeline valves 12A and 12B can be valves that can switch opening and closing manually or automatically.

More specifically, the fuel pipeline <NUM> has a first branch pipeline <NUM> having one end 22a connected to the fuel supply system <NUM>, a second branch pipeline <NUM> having one end 23a connected to the engine <NUM>, and a main pipeline <NUM> having one end 24a connected to the other end 22b of the first branch pipeline <NUM> and the other end 23b of the second branch pipeline <NUM>, and the other end 24b connected to the drum <NUM>. The system fuel pipeline <NUM> is composed of the first branch pipeline <NUM> and the main pipeline <NUM>. The engine fuel pipeline <NUM> is composed of the second branch pipeline <NUM> and the main pipeline <NUM>. The first fuel pipeline valve 12A opens and closes the first branch pipeline <NUM>, and the second fuel pipeline valve 12B opens and closes the second branch pipeline <NUM>.

In the illustrated example, the main pipeline <NUM> is used as part of the system fuel pipeline <NUM> and part of the engine fuel pipeline <NUM>; however, the system fuel pipeline <NUM> and the engine fuel pipeline <NUM> may be individually independent pipelines. In this case, a first fuel pipeline valve 12A is provided to open and close the system fuel pipeline <NUM> manually or automatically, and a second fuel pipeline valve 12B is provided to open and close the engine fuel pipeline <NUM> manually or automatically.

The heating means <NUM> is, for example, a heat exchanger that flows high-temperature fluid (high-temperature liquid or high-temperature gas) through the cavity of a tube. In this case, the tube is allowed to penetrate through the wall 10a of the drum <NUM> so that the tube is inserted into the drum <NUM>. Then, by heat exchange with the fluid flowing through the cavity of the tube, the liquefied gas fuel L guided to the interior 10b of the drum <NUM> is heated. As the heating means <NUM>, equipment equipped with a heating element, such as a heating wire, may be used in place of the heat exchanger mentioned above.

One end 14a of the gas pipeline <NUM> is connected to the drum <NUM>, and the other end 14b of the gas pipeline <NUM> is connected to the vent post <NUM>. The gas pipeline valve <NUM> opens and closes the gas pipeline <NUM>. A valve that can switch opening and closing manually or automatically can be used as the gas pipeline valve <NUM>.

According to the pipeline system <NUM>, when one or both of the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L can be pumped through the fuel pipeline <NUM> to the interior 10b of the drum <NUM>.

For example, when the first fuel pipeline valve 12A and the gas pipeline valve <NUM> are opened, and the second fuel pipeline valve 12B is closed, the liquefied gas fuel L present in the fuel supply system <NUM> can be pumped through the system fuel pipeline <NUM> (first branch pipeline <NUM> and main pipeline <NUM>) to the interior 10b of the drum <NUM>, due to the pressure of the non-combustible gas injected from the gas injection device of the fuel supply system <NUM>.

Further, for example, when the second fuel pipeline valve 12B and the gas pipeline valve <NUM> are opened, and the first fuel pipeline valve 12A is closed, the liquefied gas fuel L present in the engine <NUM> can be pumped through the engine fuel pipeline <NUM> (second branch pipeline <NUM> and main pipeline <NUM>) to the interior 10b of the drum <NUM>, due to the pressure of the non-combustible gas injected from the gas injection device of the engine <NUM>.

Moreover, for example, when the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L present in the fuel supply system <NUM> and the liquefied gas fuel L present in the engine <NUM> can be pumped through the fuel pipeline <NUM> to the interior 10b of the drum <NUM>, due to the pressure of the non-combustible gas injected from the gas injection device of the fuel supply system <NUM> and the gas injection device of the engine <NUM>.

According to the pipeline system <NUM>, when the gas pipeline valve <NUM> and the first and second fuel pipeline valves 12A and 12B are closed, the interior 10b of the drum <NUM> can be prevented from communicating with a space where air exists. Therefore, as described above, while the gas pipeline valve <NUM> and the fuel pipeline valves 12A and 12B are closed, when the liquefied gas fuel L guided to the interior 10b of the drum <NUM> is heated by the heating means <NUM> to generate vent gas G, the temperature and pressure of the vent gas G present within the drum <NUM> can be increased to enhance the internal energy. Then, when the gas pipeline valve <NUM> is opened with the internal energy of vent gas G enhanced in this way, the vent gas G converted into a high kinetic energy is guided to the vent post <NUM> through the gas pipeline <NUM>. Therefore, the vent gas G can be discharged from the vent 3a of the vent post <NUM> at a high speed. As a result, the vent gas G can be diffused far away from the vent post <NUM>, and the amount of the vent gas G falling from the vent 3a around the vent post <NUM> can be reduced. Thus, a situation where the space around the vent post <NUM> becomes an explosive atmosphere can be avoided.

Moreover, according to the pipeline system <NUM>, the wall 10a of the drum <NUM> is made of carbon steel that is excellent in pressure resistance, whereby even when the pressure of the vent gas G present within the drum <NUM> is increased, as described above, damage to the wall 10a of the drum <NUM> can be prevented. Therefore, it is possible to stably continue to discharge the vent gas G from the vent 3a at a high speed. It is not essential for the present invention to use carbon steel to form the wall 10a of the drum <NUM>; the wall 10a of the drum <NUM> may be made of a material other than carbon steel.

In addition to the configuration described above, the pipeline system <NUM> shown in <FIG> is provided with, as pipelines connected to the drum <NUM>, a discharge pipeline <NUM> provided with a discharge pipeline valve <NUM>, and a discharge pipeline <NUM> provided with a safety valve <NUM>.

The discharge pipeline <NUM> is provided to discharge lubricating oil mixed in the liquefied gas fuel L within the drum <NUM>, and waste water accumulated in the drum <NUM> during maintenance of the pipeline system <NUM>. The discharge pipeline valve <NUM> is opened when the lubricating oil or waste water is discharged.

The discharge pipeline <NUM> connects the drum <NUM> with the gas pipeline <NUM> in a position on the downstream side of the gas pipeline valve <NUM>, and the safety valve <NUM> is provided on the drum <NUM> side of the discharge pipeline <NUM>. If the internal pressure of the drum <NUM> increases more than expected, for example, due to problems with the gas pipeline valve <NUM> or malfunction of the pipeline system <NUM>, the safety valve <NUM> is automatically activated and opened, so that the vent gas G within the drum <NUM> is guided through the discharge pipeline <NUM> and the gas pipeline <NUM> to the vent post <NUM>, and discharged from the vent 3a. This prevents damage to the drum <NUM>.

The discharge pipeline <NUM>, discharge pipeline valve <NUM>, discharge pipeline <NUM>, and safety valve <NUM> are not necessarily required to vaporize the liquefied gas fuel L present in the engine <NUM> or the fuel supply system <NUM> and discharge it from the vent post <NUM>, and may be omitted from the pipeline system <NUM>.

When the discharge pipeline <NUM>, discharge pipeline valve <NUM>, discharge pipeline <NUM>, and safety valve <NUM> are provided in the pipeline system <NUM>, while the discharge pipeline valve <NUM> and the safety valve <NUM> are closed, the liquefied gas fuel L present in the fuel supply system <NUM> is pumped into the drum <NUM>, the liquefied gas fuel L present in the engine <NUM> is pumped into drum <NUM>, the liquefied gas fuel L guided into the drum <NUM> is heated by the heating means <NUM>, and the vent gas G present in the drum <NUM> is guided to the vent post <NUM> and discharged from the vent 3a.

An example of the method for discharging vent gas G using the pipeline system <NUM> is described below with reference to <FIG>.

The method for discharging vent gas G shown in <FIG> comprises a pumping step and a heating discharge step performed after the pumping step.

In the pumping step, while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L is pumped through the fuel pipeline <NUM> to the interior 10b of the drum <NUM>. Opening the fuel pipeline valve <NUM> includes opening one or both of the first and second fuel pipeline valves 12A and 12B. When the first fuel pipeline valve 12A and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L present in the fuel supply system <NUM> is pumped to the interior 10b of the drum <NUM>. When the second fuel pipeline valve 12B and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L present in the engine <NUM> is pumped to the interior 10b of the drum <NUM>. When the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> are opened, the liquefied gas fuel L present in the fuel supply system <NUM> and the engine <NUM> is pumped to the interior 10b of the drum <NUM>.

The heating discharge step includes a heating step that is performed until the air pressure in the interior 10b of the drum <NUM> is increased to an upper limit value equal to or higher than atmospheric pressure, and a discharge step that is performed until the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to a lower limit value equal to or higher than atmospheric pressure.

In the heating step, until the air pressure in the interior 10b of the drum <NUM> is increased to the upper limit value, while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed, the liquefied gas fuel L present in the interior 10b of the drum <NUM> is heated by the heating means <NUM> to generate vent gas G. Closing the fuel pipeline valve <NUM> includes closing both of the first and second fuel pipeline valves 12A and 12B.

In the discharge step, the gas pipeline valve <NUM> is opened when the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, and the gas pipeline valve <NUM> is closed when the air pressure in the interior 10b of the drum <NUM> is reduced to the lower limit value, whereby during the time in which the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to the lower limit value, the vent gas G present in the interior 10b of the drum <NUM> is guided to the vent post <NUM> and discharged from the vent post <NUM>. When the air pressure in the interior 10b of the drum <NUM> is reduced to the lower limit value, the gas pipeline valve <NUM> is closed, whereby the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> are closed, and the step proceeds to the heating step.

When the above discharge method is performed, the pipeline system <NUM> is provided with a pressure sensor <NUM> (<FIG>) that measures the air pressure in the interior 10b of the drum <NUM>. Based on the measured value of the pressure sensor <NUM>, the time in which the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value or is reduced to the lower limit value is specified.

According to the above discharge method, the gas pipeline valve <NUM> is opened during the time in which the air pressure in the interior 10b of the drum <NUM> is in the range equal to or higher than atmospheric pressure (from the lower limit value to the upper limit value); thus, the vent gas G can be discharged at a high speed from the vent 3a of the vent post <NUM>. Therefore, the vent gas G can be diffused far away from the vent post <NUM>, and the amount of the vent gas G falling around the vent post <NUM> can be reduced; thus, a situation where the space around the vent post <NUM> becomes an explosive atmosphere can be avoided. In order to increase the discharge time of the vent gas G (i.e., the time in which the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to the lower limit value), it is preferable to heat the liquefied gas fuel L present in the interior 10b of the drum <NUM> by the heating means <NUM> to generate the vent gas G, not only in the heating step, but also in the discharge step. Further, when the discharge pipeline <NUM>, discharge pipeline valve <NUM>, discharge pipeline <NUM>, and safety valve <NUM> are provided in the pipeline system <NUM>, the pumping step and the heating discharge step are performed while the discharge pipeline valve <NUM> and the safety valve <NUM> are closed.

Further, in order to automatically open and close the gas pipeline valve <NUM> in the heating discharge step, the marine vessel <NUM> may be provided with a control device <NUM> (<FIG>) that controls the gas pipeline valve <NUM> based on the measured value of the pressure sensor <NUM>, while the fuel pipeline valve <NUM> is closed.

The control device <NUM> has, as means (functional block) for controlling the gas pipeline valve <NUM> while the fuel pipeline valve <NUM> is closed, an upper limit value determining means <NUM>, a lower limit value determining means <NUM>, and a valve control means <NUM> (<FIG>). These means <NUM>, <NUM>, and <NUM> may be realized in a hardware manner; however, these means may also be realized in a software manner in such a manner that the processor of the control device <NUM> reads a program into memory and executes it.

When the means <NUM>, <NUM>, and <NUM> shown in <FIG> are realized in a hardware manner, the control device <NUM> includes, for example, a relay circuit, a pressure switch is used as the pressure sensor <NUM>, and open/close valves with a drive source that utilizes hydraulic pressure or air pressure are used as the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>.

When the means <NUM>, <NUM>, and <NUM> shown in <FIG> are realized in a software manner, for example, the control device <NUM> is a device including a programmable logic controller (PLC), and a pressure transmitter is used as the pressure sensor <NUM>. Alternatively, a computer including CPU, ROM, and RAM is used as the control device <NUM>.

<FIG> is a flowchart of processing performed by the control device <NUM>.

The processing shown in <FIG> is started in response to the closing of the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> after the liquefied gas fuel L is pumped to the interior 10b of the drum <NUM> in the pumping step. Closing the fuel pipeline valve <NUM> means that both of the first and second fuel pipeline valves 12A and 12B are closed. Moreover, until the processing shown in <FIG> is executed, the fuel pipeline valve <NUM> is kept closed, and the liquefied gas fuel L present in the interior 10b of the drum <NUM> is heated by the action of the heating means <NUM> to generate vent gas G.

The upper limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> reaches an upper limit value equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is closed (S101). During the time in which it is not determined that the measured value of the pressure sensor <NUM> reaches the upper limit value (NO in S101), the gas pipeline valve <NUM> is kept closed.

When the upper limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> reaches the upper limit value, while the gas pipeline valve <NUM> is closed (YES in S101), the valve control means <NUM> opens the gas pipeline valve <NUM> (S102).

The lower limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> is reduced to a lower limit value that is lower than the upper limit value and equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is opened (S103).

During the time in which the lower limit value determining means <NUM> does not determine that the measured value of the pressure sensor <NUM> is reduced to the lower limit value, while the gas pipeline valve <NUM> is opened (NO in S103), the gas pipeline valve <NUM> is kept open.

When the lower limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> is reduced to the lower limit value, while the gas pipeline valve <NUM> is opened (YES in S103), the valve control means <NUM> closes the gas pipeline valve <NUM> (S104).

After the valve control means <NUM> closes the gas pipeline valve <NUM> in S104, the processing returns to determination by the upper limit value determining means <NUM> in S101.

According to the processing shown in <FIG>, when determination is made as NO in S101 until the air pressure in the interior 10b of the drum <NUM> is increased to the upper limit value, the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed, and the heating step is performed.

Then, when the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, determination is made as YES in S101, and S102 is performed, thereby opening the gas pipeline valve <NUM> while the fuel pipeline valve <NUM> is closed, and starting the discharge step.

After S102 is performed, determination is made as NO in S103 during the time in which the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to the lower limit value, thereby continuing the discharge step, while the fuel pipeline valve <NUM> is closed and the gas pipeline valve <NUM> is opened.

When the air pressure in the interior 10b of the drum <NUM> is reduced to the lower limit value, determination is made as YES in S103, and S104 is performed, thereby stopping the discharge step, while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed.

Then, the step proceeds to S101 after S104, so that the discharge step proceeds to the heating step.

The present invention is not limited to the above embodiment, and can be modified in various ways.

For example, the method for discharging vent gas G of the present invention can be such that the pumping step is performed until the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> is higher than a first position, the heating discharge step is performed until the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> is lowered to the first position, and the heating discharge step is suspended when the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches the first position. In this way, the heating step is always performed in the presence of the liquefied gas fuel L within the drum <NUM>; thus, it is possible to avoid wasteful heating (heating with no liquid inside) by the heating means <NUM> in the absence of the liquefied gas fuel L within the drum <NUM>. In the above case, the pipeline system is provided with a fuel sensor <NUM> that measures the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM>, and the time in which the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches the first position is specified based on the measured value of the fuel sensor <NUM>. As the fuel sensor <NUM>, for example, an ultrasonic sensor, a radar sensor, a tuning-fork sensor, or a float sensor can be used.

Moreover, when the method for discharging vent gas G of the present invention is as described above, in order to automatically open and close the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>, the marine vessel <NUM> may be provided with a control device <NUM> (<FIG>) that performs processing based on the measured values of the pressure sensor <NUM> and fuel sensor <NUM> provided in the pipeline system <NUM>.

The control device <NUM> (<FIG>) has, as means (functional block) for controlling the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>, a position determining means <NUM> upon reception of a stop signal, a first position determining means <NUM>, an upper limit value determining means <NUM>, a lower limit value determining means <NUM>, and a valve control means <NUM>. These means <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be realized in a hardware manner; however, these means may also be realized in a software manner in such a manner that the processor of the control device <NUM> reads a program into memory and executes it.

When the means <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> shown in <FIG> are realized in a hardware manner, the control device <NUM> includes, for example, a relay circuit, a pressure switch is used as the pressure sensor <NUM>, and open/close valves with a drive source that utilizes hydraulic pressure or air pressure are used as the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>.

When the means <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> shown in <FIG> are realized in a software manner, for example, the control device <NUM> is a device including a programmable logic controller (PLC), and a pressure transmitter is used as the pressure sensor <NUM>. Alternatively, a computer including CPU, ROM, and RAM is used as the control device <NUM>.

<FIG> is a flowchart of processing performed by the control device <NUM>. The processing shown in <FIG> is executed on the condition that the signal transmissions shown in a and b below are performed, or that the signal transmissions shown in c and d below are performed. The time in which the signal transmissions shown in a and b below are performed, and the time in which the signal transmissions shown in c and d below are performed, are set as different times.

Before the processing shown in <FIG> is performed, the fuel pipeline valve <NUM> (first and second fuel pipeline valves 12A and 12B) and the gas pipeline valve <NUM> are closed. The processing of <FIG> is described below.

Upon reception of a fuel pumping start signal by the control device <NUM> from one of the engine <NUM> and the fuel supply system <NUM>, the valve control means <NUM> opens the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> (S201). Opening the fuel pipeline valve <NUM> in S201 means that one of the first and second fuel pipeline valves 12A and 12B is opened. When S201 is performed, a pumping step can be started to pump the liquefied gas fuel L present in one of the engine <NUM> and the fuel supply system <NUM> to the interior 10b of the drum <NUM>.

Then, upon reception of a fuel pumping stop signal by the control device <NUM> from the sender of the fuel pumping start signal, the position determining means <NUM> upon reception of a stop signal determines, based on the measured value of the fuel sensor <NUM>, whether the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum is lower than the first position (S202). Hereinafter, "the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum" is appropriately referred to as "the liquid level position of the liquefied gas fuel L within the drum <NUM>.

When it is not determined in S202 that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (NO in S202), the valve control means <NUM> closes the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> (S204). Closing the fuel pipeline valve <NUM> in S204 means that one of the first and second fuel pipeline valves 12A and 12B that has been opened in S201 is closed.

For example, when the sender of the fuel pumping start signal in S201 and the sender of the fuel pumping stop signal in S202 are the fuel supply system <NUM>, the valve control means <NUM> opens the first fuel pipeline valve 12A and the gas pipeline valve <NUM> in S201, and closes the first fuel pipeline valve 12A and the gas pipeline valve <NUM> in S204.

Moreover, when the sender of the fuel pumping start signal in S201 and the sender of the fuel pumping stop signal in S202 are the engine <NUM>, the valve control means <NUM> opens the second fuel pipeline valve 12B and the gas pipeline valve <NUM> in S201, and closes the second fuel pipeline valve 12B and the gas pipeline valve <NUM> in S204.

Then, S204 is performed, thereby stopping the pumping step of pumping the liquefied gas fuel L present in one of the engine <NUM> and the fuel supply system <NUM> through the fuel pipeline <NUM> to the interior 10b of the drum <NUM>.

The fuel pumping stop signal is transmitted from one of the engine <NUM> and the fuel supply system <NUM> to the control device <NUM> when the liquid level position of the liquefied gas fuel L present in one of the engine <NUM> and the fuel supply system <NUM> (hereinafter, "the liquid level position of the liquefied gas fuel L on the engine <NUM> side") is lowered to a predetermined position. The predetermined position is determined by experience. The determination in S202 is performed based on "the idea that when the liquid level position of the liquefied gas fuel L on the engine <NUM> side is lowered to the predetermined position, the liquid level position of the liquefied gas fuel L within the drum <NUM> should be equal to or higher than the first position.

When it is determined in S202 that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (YES in S202), the position determining means <NUM> upon reception of a stop signal outputs an error signal indicating that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (S205), the valve control means <NUM> closes the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> (S206), and the processing shown in <FIG> is stopped. In this case, the output of the error signal notifies the user that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position, and the user performs, for example, resetting of the predetermined position (i.e., the user rests the liquid level position of the liquefied gas fuel L present in the engine <NUM> or the fuel supply system <NUM> when the engine <NUM> or the fuel supply system <NUM> transmits a fuel pumping stop signal to the control device <NUM>). Closing the fuel pipeline valve <NUM> in S206 means that one of the first and second fuel pipeline valves 12A and 12B that has been opened in S201 is closed.

After determination is made as NO in S202 and S204 is performed, the first position determining means <NUM> determines, based on the measured value of the fuel sensor <NUM>, whether the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (S207).

When the first position determining means <NUM> does not determine that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (NO in S207), the upper limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> reaches an upper limit value equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is closed (S208).

When the upper limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> reaches the upper limit value while the gas pipeline valve <NUM> is closed (YES in S208), the valve control means <NUM> opens the gas pipeline valve <NUM> (S209).

When the upper limit value determining means <NUM> does not determine that the measured value of the pressure sensor <NUM> reaches the upper limit value while the gas pipeline valve <NUM> is closed (NO in S208), the lower limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> is reduced to a lower limit value that is lower than the upper limit value and equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is opened (S210).

By using the opening and closing of the gas pipeline valve <NUM> as the determination condition, the lower limit value determining means <NUM> makes determination separately when the measured value of the pressure sensor <NUM> (air pressure within the drum <NUM>) is increased to the lower limit value while the gas pipeline valve <NUM> is closed, and when the measured value of the pressure sensor <NUM> (air pressure within the drum <NUM>) is reduced to the lower limit value while the gas pipeline valve <NUM> is opened. That is, when the measured value of the pressure sensor <NUM> is increased to the lower limit value (when reaching the lower limit value from a value lower than the lower limit value), the lower limit value determining means <NUM> determines NO in S210 because the gas pipeline valve <NUM> is not opened. Further, when the measured value of the pressure sensor <NUM> is reduced to the lower limit value (when reaching the lower limit value from a value higher than the lower limit value), the lower limit value determining means <NUM> determines YES in S210 because the gas pipeline valve <NUM> is opened.

When the lower limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> is reduced to the lower limit value while the gas pipeline valve <NUM> is opened (YES in S210), the valve control means <NUM> closes the gas pipeline valve <NUM> (S211).

Then, after the valve control means <NUM> opens the gas pipeline valve <NUM> in S209, when the lower limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> is not reduced to the lower limit value in S210 (NO in S210), or after the valve control means <NUM> closes the gas pipeline valve <NUM> in S211, the processing returns to determination by the first position determining means <NUM> in S207.

Then, when the first position determining means <NUM> determines that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position (YES in S207), the valve control means <NUM> closes the gas pipeline valve <NUM> (S212), and the processing of <FIG> is stopped.

According to the processing shown in <FIG>, during the time from the execution of S201 to the execution of S204, the pumping step is performed while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are opened.

Then, S204 is performed, thereby closing the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> for the initial heating step.

Until the liquefied gas fuel L stored in the interior 10b of the drum <NUM> is reduced to the first amount, any of the following processings <NUM>, <NUM>, <NUM>, and <NUM> is performed by the determination as NO in S207. Then, the processing returns to S207.

Processing <NUM> for performing the heating step: determination is made in S207 while the valves <NUM> and <NUM> are closed; NO in S207 → NO in S208 → NO in S210.

Processing <NUM> for starting the discharge step: determination is made in S207 while the valves <NUM> and <NUM> are closed; NO in S207 → YES in S208 → S209.

Processing <NUM> for continuing the discharge step: determination is made in S207 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S207 → NO in S208 → NO in S210.

Processing <NUM> for stopping the discharge step: determination is made in S207 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S207 → NO in S208 → YES in S210 → S211.

Until the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position, and until the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, processing <NUM> (determination is made in S207 while the valves <NUM> and <NUM> are closed; NO in S207 → NO in S208 → NO in S210) is repeated, thereby performing the heating step while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed.

Until the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position, and when the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, processing <NUM> (determination is made in S207 while the valves <NUM> and <NUM> are closed; NO in S207 → YES in S208 → S209) is executed, thereby starting the discharge step while the fuel pipeline valve <NUM> is closed and the gas pipeline valve <NUM> is opened.

Until the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position, and during the time in which the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to the lower limit value, processing <NUM> (determination is made in S207 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S207 → NO in S208 → NO in S210) is repeated, thereby continuing the discharge step while the fuel pipeline valve <NUM> is closed and the gas pipeline valve <NUM> is opened.

Until the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position, and when the air pressure in the interior 10b of the drum <NUM> is reduced to the lower limit value, processing <NUM> (determination is made in S207 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S207 → NO in S208 → YES in S210 → S211) is executed, thereby stopping the discharge step while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed.

Then, during the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is not lowered to the first position, processings <NUM> to <NUM> are repeated, thereby repeating the heating discharge step (<FIG>) in which the discharge step is performed after the heating step.

Then, when the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the first position, determination is made as YES in S207, the gas pipeline valve <NUM> is closed in S212, and the processing shown in <FIG> is stopped. When the control device <NUM> receives a fuel pumping start signal from one of the engine <NUM> and the fuel supply system <NUM>, the processing shown in <FIG> is started again.

The processing shown in <FIG> may be executed on the condition that the signal transmissions shown in e and f below are performed.

When the above e and f are used as the execution condition of the processing of <FIG>, upon reception of a fuel pumping start signal by the control device <NUM> from both of the engine <NUM> and the fuel supply system <NUM>, the valve control means <NUM> opens the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> (S201). Then, upon reception of a fuel pumping stop signal by the control device <NUM> from the sender of the fuel pumping start signal (both of the engine <NUM> and the fuel supply system <NUM>) in S201, the position determining means <NUM> upon reception of a stop signal determines, based on the measured value of the fuel sensor <NUM>, whether the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum is lower than the first position (S202). Then, when determination is made as NO in S202, the valve control means <NUM> closes the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> (S204). Further, when determination is made as YES in S202, the position determining means <NUM> upon reception of a stop signal outputs an error signal indicating that the liquid level position of the liquefied gas fuel L within the drum <NUM> is lower than the first position (S205), and the valve control means <NUM> closes the first and second fuel pipeline valves 12A and 12B, and the gas pipeline valve <NUM> (S206). S207 to S212 are the same processings as those described above.

Moreover, the method for discharging vent gas G of the present invention can be such that a pumping step is performed until the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches a second position, a heating discharge step is performed until the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> is reduced from the second position to a third position, the heating discharge step is suspended when the liquid level position (height) of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches the third position, and the step proceeds to the pumping step. In this way, it is possible to prevent supplying excessive liquefied gas fuel L to the interior 10b of the drum <NUM>, and it is also possible to avoid wasteful heating (heating with no liquid inside) by the heating means <NUM> in the absence of the liquefied gas fuel L in the interior 10b of the drum <NUM>. In the above case, the pipeline system <NUM> is provided with a fuel sensor <NUM> that measures the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum <NUM>. The time in which the amount of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches the second position or the third position is specified based on the measured value of the fuel sensor <NUM>.

When the method for discharging vent gas G of the present invention is as described above, in order to automatically open and close the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>, the marine vessel <NUM> may be provided with a control device <NUM> (<FIG>) that performs processing based on the measured values of the pressure sensor <NUM> and fuel sensor <NUM> provided in the pipeline system <NUM>.

The control device <NUM> has, as means (functional block) for controlling the fuel pipeline valve <NUM> and the gas pipeline valve <NUM>, a second position determining means <NUM>, a third position determining means <NUM>, an upper limit value determining means <NUM>, a lower limit value determining means <NUM>, and a valve control means <NUM> (<FIG>). These means <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be realized in a hardware manner; however, these means may also be realized in a software manner in such a manner that the processor of the control device <NUM> reads a program into memory and executes it.

The processing shown in <FIG> is started in response to the opening of the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> in order to perform the pumping step. Opening the fuel pipeline valve <NUM> means that one or both of the first and second fuel pipeline valves 12A and 12B is opened.

The second position determining means <NUM> determines whether the liquid level position of the liquefied gas fuel L stored in the interior 10b of the drum <NUM> reaches the second position, while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are opened (S301). This processing is performed based on the measured value of the fuel sensor <NUM>. During the time in which it is not determined that the liquid level position of the liquefied gas fuel L within the drum <NUM> reaches the second position (NO in S301), the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are kept open.

When the second position determining means <NUM> determines that the liquid level position of the liquefied gas fuel L within the drum <NUM> reaches the second position (YES in S301), the valve control means <NUM> closes the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> (S302). Closing the fuel pipeline valve <NUM> in S302 means that one or both of the first and second fuel pipeline valves 12A and 12B that has been opened before S302 is closed (when one of the first and second fuel pipeline valves 12A and 12B has been closed before S302, the one of the first and second fuel pipeline valves 12A and 12B is kept closed).

The third position determining means <NUM> determines whether the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the third position, while the fuel pipeline valve <NUM> is closed (S303). This processing is also performed based on the measured value of the fuel sensor <NUM>.

When the third position determining means <NUM> does not determine that the liquid level position of the liquefied gas fuel L within the drum <NUM> is reduced to the third position (NO in S303), the upper limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> reaches an upper limit value equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is closed (S304).

When the upper limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> reaches the upper limit value while the gas pipeline valve <NUM> is closed (YES in S304), the valve control means <NUM> opens the gas pipeline valve <NUM> (S305).

When the upper limit value determining means <NUM> does not determine that the measured value of the pressure sensor <NUM> reaches the upper limit value while the gas pipeline valve <NUM> is closed (NO in S304), the lower limit value determining means <NUM> determines whether the measured value of the pressure sensor <NUM> is reduced to a lower limit value that is lower than the upper limit value and equal to or higher than atmospheric pressure, while the gas pipeline valve <NUM> is opened (S306).

By using the opening and closing of the gas pipeline valve <NUM> as the determination condition, the lower limit value determining means <NUM> makes determination separately when the measured value of the pressure sensor <NUM> (air pressure within the drum <NUM>) is increased to the lower limit value while the gas pipeline valve <NUM> is closed, and when the measured value of the pressure sensor <NUM> (air pressure within the drum <NUM>) is reduced to the lower limit value while the gas pipeline valve <NUM> is opened. That is, when the measured value of the pressure sensor <NUM> is increased to the lower limit value (when reaching the lower limit value from a value lower than the lower limit value), the lower limit value determining means <NUM> determines NO because the gas pipeline valve <NUM> is not opened. Further, when the measured value of the pressure sensor <NUM> is reduced to the lower limit value (when reaching the lower limit value from a value higher than the lower limit value), the lower limit value determining means <NUM> determines YES because the gas pipeline valve <NUM> is opened.

When the lower limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> is reduced to the lower limit value while the gas pipeline valve <NUM> is opened (YES in S306), the valve control means <NUM> closes the gas pipeline valve <NUM> (S307).

Then, after the valve control means <NUM> opens the gas pipeline valve <NUM> in S305, when the lower limit value determining means <NUM> determines that the measured value of the pressure sensor <NUM> is not reduced to the lower limit value in S306 (NO in S306), or after the valve control means <NUM> closes the gas pipeline valve <NUM> in S307, the processing returns to determination by the third position determining means <NUM> in S303.

Then, when the third position determining means <NUM> determines that the liquid level position of the liquefied gas fuel L within the drum <NUM> is reduced to the third position (YES in S303), the valve control means <NUM> opens the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> (S308). Thereafter, the processing returns to determination by the second position determining means <NUM> in S301.

According to the processing shown in <FIG>, determination is made as NO in S301 until the liquid level position of the liquefied gas fuel L within the drum <NUM> reaches the second position, thereby performing the pumping step while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are opened.

Then, when the liquid level position of the liquefied gas fuel L within the drum <NUM> reaches the second position, determination is made as YES in S301, and S302 is performed, thereby closing the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> for the initial heating step.

After S302 is performed, during the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is reduced from the second position to the third position, any of the following processings <NUM>, <NUM>, <NUM>, and <NUM> is performed. Then, the processing returns to S303.

Processing <NUM> for performing the heating step: determination is made in S303 while the valves <NUM> and <NUM> are closed; NO in S303 → NO in S304 → NO in S306.

Processing <NUM> for starting the discharge step: determination is made in S303 while the valves <NUM> and <NUM> are closed; NO in S303 → YES in S304 → S305.

Processing <NUM> for continuing the discharge step: determination is made in S303 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S303 → NO in S304 → NO in S306.

Processing <NUM> for stopping the discharge step: determination is made in S303 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S303 → NO in S304 → YES in S306 → S307.

During the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered from the second position to the third position, and until the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, processing <NUM> (determination is made in S303 while the valves <NUM> and <NUM> are closed; NO in S303 → NO in S304 → NO in S306) is repeated, thereby performing the heating step while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed.

During the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered from the second position to the third position, and when the air pressure in the interior 10b of the drum <NUM> reaches the upper limit value, processing <NUM> (determination is made in S303 while the valves <NUM> and <NUM> are closed; NO in S303 → YES in S304 → S305) is executed, thereby opening the gas pipeline valve <NUM> while the fuel pipeline valve <NUM> is closed, and starting the discharge step.

During the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered from the second position to the third position, and during the time in which the air pressure in the interior 10b of the drum <NUM> is reduced from the upper limit value to the lower limit value, processing <NUM> (determination is made in S303 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S303 → NO in S304 → NO in S306) is repeated, thereby continuing the discharge step, while the fuel pipeline valve <NUM> is closed and the gas pipeline valve <NUM> is opened.

During the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered from the second position to the third position, and when the air pressure in the interior 10b of the drum <NUM> is reduced to the lower limit value, processing <NUM> (determination is made in S303 while the valve <NUM> is closed and the valve <NUM> is opened; NO in S303 → NO in S304 → YES in S306 → S307) is executed, thereby stopping the discharge step, while the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are closed.

Thereafter, processings <NUM> to <NUM> are repeated during the time in which the liquid level position of the liquefied gas fuel L within the drum <NUM> is not lowered to the third position, thereby repeating the heating discharge step (<FIG>) in which the discharge step is performed after the heating step.

Then, when the liquid level position of the liquefied gas fuel L within the drum <NUM> is lowered to the third position, determination is made as YES in S303, the fuel pipeline valve <NUM> and the gas pipeline valve <NUM> are opened in S308, and the processing returns to S301, thereby suspending the heating discharge step and restarting the pumping step.

In the above example, one engine <NUM> is provided in the marine vessel <NUM>; however, two or more engines <NUM> may be provided in the marine vessel <NUM>. In that case, each engine <NUM> may be provided with one fuel supply system <NUM>, or the plural engines <NUM> may be provide with one fuel supply system <NUM>. In the above case, the liquefied gas fuel L present in each engine <NUM> and each fuel supply system <NUM> is guided through the fuel pipeline to the interior 10b of the drum <NUM>, whereby the liquefied gas fuel L present in each engine <NUM> and each fuel supply system <NUM> can be vaporized and discharged from the vent post <NUM> at a high speed.

Claim 1:
A pipeline system (<NUM>) provided in a marine vessel (<NUM>) that discharges vent gas vaporized from liquefied gas fuel from a vent post (<NUM>), the pipeline system comprising:
a drum (<NUM>) having an interior (10b) surrounded by a wall (10a);
a fuel pipeline (<NUM>) for guiding the liquefied gas fuel tc the interior (10b) of the drum;
a fuel pipeline valve (<NUM>, 12A, 12B) opening and closing the fuel pipeline (<NUM>);
a heating means (<NUM>) for heating the liquefied gas fuel guided to the interior (10b) of the drum to thereby generate the vent gas;
a gas pipeline (<NUM>) for guiding the vent gas present in the interior (10b) of the drum to the vent post (<NUM>); and
a gas pipeline valve (<NUM>) opening and closing the gas pipeline (<NUM>).