JP7303945B2 - LNG cargo hold test method and offshore structure applying it and liquefied nitrogen supply system for offshore structure - Google Patents

Description

The present invention relates to an LNG cargo hold test method, a marine structure to which the method is applied, and a liquefied nitrogen supply system for the marine structure.

After the LNG cargo hold of the offshore structure is built, primary integrity tests are performed on the secondary barriers on land. After that, the offshore structure is moved offshore and supplied and demanded through LNG bunkering, or LNG produced directly offshore is injected into the LNG cargo hold to perform cool down work. A secondary integrity test is performed on the secondary barriers of the LNG cargo hold after the cold shock is generated by the cool down operation.

In this way, after conducting the primary integrity test on the secondary barrier on land, the only way to conduct the secondary integrity test on the secondary barrier is to move the offshore structure offshore. .

For example, among offshore structures, in the case of FLNG (Floating Liquefied Natural Gas), which has no self-navigation capability, it is impossible to enter an LNG terminal, so it is difficult to supply and demand LNG. Therefore, LNG is supplied and demanded by LNG bunkering or direct offshore production while FLNG is placed in an offshore FLNG installation area.

However, in order to receive supply and demand of LNG from offshore and to perform LNG cargo hold test work, the work approval procedure is complicated and costs a lot. In addition to this, there is a problem that it is difficult to respond quickly when an emergency situation occurs offshore.

In addition, in the case of a ship with self-propulsion capability among offshore structures, after the first soundness test for the secondary barrier, the LNG terminal is left from the shipyard under construction for the supply and demand of LNG, which is a refrigerant. After entering the port, the LNG cargo hold must be tested again after returning, which takes a lot of time and costs a lot.

Embodiments of the present invention provide an LNG cargo hold test method that can reduce costs and improve work efficiency by performing the LNG cargo hold test process onshore, a marine structure applying the same, and liquefied nitrogen for marine structures. Provide supply system.

According to one aspect of the present invention, the steps of (a) after construction of an LNG cargo hold of a FLNG, subjecting a secondary barrier to said LNG cargo hold to a primary integrity test; (c) performing a secondary integrity test on the secondary barrier of the LNG cargo hold, wherein the steps (a) to (c) are the same as those described above; An LNG cargo hold test method may be provided in which the FLNG is located onshore and the LNG cargo hold of the FLNG is tested, and step (b) is performed using any refrigerant other than LNG. .

According to another aspect of the invention, the steps of (a) after construction of an LNG cargo hold of a ship, subjecting a secondary barrier to said LNG cargo hold to a primary integrity test; (b) said LNG cargo hold. (c) performing a cool-down operation on the interior of said LNG cargo hold; including performing a secondary integrity test on a secondary barrier, wherein steps (a)-(d) are performed on an LNG cargo hold of said vessel with said vessel located onshore; , the steps (b) and (c) may be performed using liquefied nitrogen.

In the step of performing the cool-down operation, while injecting liquefied nitrogen into the LNG cargo hold at room temperature, the internal temperature of the LNG cargo hold is maintained at −158° C.±5° C. for a set time. may include a process of controlling to

After performing the cool-down work, the inside of the LNG cargo hold is filled with liquefied nitrogen onshore, a pumping test is performed on the pump inside the LNG cargo hold, and the inside of the LNG cargo hold using a loading arm of liquefied nitrogen to other vessels.

After the step of performing the second soundness test, the inside of the LNG cargo hold is filled with LNG, a pump inside the LNG cargo hold is subjected to a pumping test, and a loading arm is used to perform a pumping test inside the LNG cargo hold. LNG offloading to other vessels, which may be conducted offshore in the case of the FLNG, or in the case of a self-propelled vessel, located at an onshore terminal. state may be performed.

According to yet another aspect of the present invention, the steps of (a) conducting a primary LNG cargo hold barrier integrity test, (b) conducting a primary LNG cargo hold secondary barrier integrity test. (c) performing a piping cold test on piping connected to said LNG cargo hold; (d) performing a cool-down operation on the interior of said LNG cargo hold; (e) said LNG cargo hold. (f) sending out the fluid inside the LNG cargo hold, injecting dry air into the inside of the LNG cargo hold, and then into the inside of the LNG cargo hold and (g) performing a secondary integrity test on the secondary barriers of said LNG cargo hold, wherein steps (a)-(g) are performed on offshore structures, including vessels. It may be done to the LNG cargo hold of said offshore structure with the goods located onshore.

In the steps (b) and (g), nitrogen gas is filled in the lower heat insulating layer of the secondary barrier and the upper heat insulating layer of the secondary barrier, and different pressures are applied to the lower heat insulating layer and the lower heat insulating layer of the secondary barrier after a predetermined time. The method may comprise measuring a pressure change value between the heat insulating layer and the upper heat insulating layer, and determining whether the secondary barrier is sound based on the measured value.

The step (d) is a process of injecting refrigerant into the LNG cargo hold to control the internal temperature of the LNG cargo hold to maintain −158° C.±5° C. for a preset time. may include

In the primary barrier integrity test, an ammonia reactant is applied to a welded portion of the primary barrier, a space between the primary barrier and the secondary barrier is filled with ammonia gas, and the ammonia reactive material is discolored. The pipe cold test consists of a process of judging whether the primary barrier is sound based on the presence or absence of It may comprise the step of determining whether it falls within the range.

According to still another aspect of the present invention, it is possible to provide an offshore structure to which the LNG cargo hold test method is applied.

According to yet another aspect of the present invention, a buffer tank supplying liquefied nitrogen to said LNG cargo hold and an internal temperature of said LNG cargo hold are set for LNG cargo hold test operations of an offshore structure located onshore. A liquid nitrogen supply system for offshore structures may be provided that includes a controller that regulates the amount of liquid nitrogen injected into the LNG cargo hold to be maintained within a set temperature range for a set period of time.

The apparatus may further include a tank truck supplied with the liquefied nitrogen from the liquefied nitrogen generator, moved to a yard where the buffer tank is provided, and supplying the liquefied nitrogen to the buffer tank.

a liquefied nitrogen injection pipe connecting the buffer tank and the LNG cargo hold; and an injection unit for injecting the liquefied nitrogen supplied through the liquefied nitrogen injection pipe into the LNG cargo hold to cool down the LNG cargo hold. and a control valve disposed in the liquefied nitrogen injection pipe, and a temperature sensor for measuring the temperature inside the LNG cargo hold, wherein the control unit performs the control based on the measured temperature value. The amount of liquefied nitrogen injected into the LNG cargo hold by the injection unit may be adjusted by controlling the degree of opening and closing of the valve.

The control unit may adjust the amount of liquefied nitrogen injected into the LNG cargo hold so that the internal temperature of the LNG cargo hold is maintained at -158°C±5°C.

The LNG cargo hold test method according to the embodiment of the present invention, the offshore structure and the liquefied nitrogen supply system for the offshore structure to which it is applied reduce costs and improve work efficiency by conducting the LNG cargo hold test process onshore. be able to. In particular, by doing onshore large-scale test work that had to be done offshore in the past, it is possible to improve the convenience, stability and efficiency of the work and move up the work schedule.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

FIG. 1 is a flowchart of a LNG cargo hold test process for offshore structures conducted onshore according to an embodiment of the present invention.

FIG. 2 is a flow chart showing the LNG cargo hold test process of offshore structures performed after the LNG cargo hold test of FIG.

FIG. 3 illustrates in block diagram form a liquefied nitrogen supply system according to an embodiment of the invention.

FORM FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The embodiments described below are provided as examples so that the spirit of the present invention can be fully conveyed to those skilled in the art to which the present invention pertains. The present invention is not limited to the examples described below, but may be embodied in other forms. In order to clearly describe the present invention, parts irrelevant to the description are omitted in the drawings, and the widths, lengths, thicknesses, etc. of components in the drawings may be exaggerated for convenience. Like reference numbers refer to like elements throughout the specification.

FIG. 1 is a flowchart of a LNG cargo hold test process for offshore structures conducted onshore according to an embodiment of the present invention.

The LNG cargo hold test process shown in FIG. 1 is performed on an LNG cargo hold of an offshore structure while the offshore structure is located onshore.

Offshore structures according to embodiments of the present invention include FLNG (Floating Liquefied Natural Gas), FSRU (Floating Storage Registration Unit), FSU (Floating Storage Unit), LNG-RV (Re-gasification Vessel), which do not have self-navigation capability. ) such as It may also include vessels such as offshore structures with LNG cargo holds and self-propelled LNG carriers.

The term onshore, as used in the embodiments of the present invention, means land and includes yard, which means shipyard. That is, onshore is used in a broader sense than yards. LNG cargo hold testing at the yard means that the LNG cargo hold testing is done in the shipyard where the offshore structure was built. This includes LNG cargo hold testing not only at the shipyard, but also at other docking locations outside of it.

In the following embodiments of the present invention, the LNG cargo hold test process for offshore structures will be described as being carried out onshore, but it may also be carried out onshore in a yard, that is, in a shipyard.

Referring to FIG. 1, first, a Primary Barrier Global Test (PBGT) of an LNG cargo hold of offshore structures is conducted onshore (S201). In this process (S201), the ammonia reactant is applied to the welding part of the primary barrier, the space between the primary barrier and the secondary barrier is filled with ammonia gas, and the primary It may comprise the process of determining whether the integrity of the barrier is present. For example, if a groove is formed in the welded part of the primary barrier, and the ammonia reactant applied to the welded part of the primary barrier reacts with the ammonia gas filled between the primary barrier and the secondary barrier, causing discoloration. , it can be judged that the primary barrier is defective.

Next, a secondary barrier tightening test (SBTT) of the LNG cargo hold of the offshore structure is conducted onshore (S202). In this process (S202), the lower insulation space (IS) of the secondary barrier and the upper insulation space (IBS) of the secondary barrier are filled with nitrogen gas and different pressures are applied. After a period of time, measure the pressure change value between the lower insulation layer of the secondary barrier and the upper insulation layer of the secondary barrier, and judge whether the secondary barrier is sound based on the measured pressure change value. may comprise the process of At this time, the pressures of the lower heat insulation layer of the secondary barrier and the pressure of the upper heat insulation layer of the secondary barrier may be measured by pressure gauges (not shown) provided in the respective spaces. For example, if the pressures of the lower insulation layer of the secondary barrier and the pressure of the upper insulation layer of the secondary barrier are equal to each other, it can be determined that the secondary barrier is defective.

Next, a pipe cold test is performed on the pipes connected to the LNG cargo hold of the offshore structure for LNG loading or unloading onshore (S203). This process (S203) may include a process of flowing the refrigerant into the pipe and measuring the amount of contraction and expansion displacement of the pipe with a displacement measuring device (not shown). Here, the coolant may contain, for example, liquefied nitrogen. The pipe may be a pipe that is connected to the filling pipe and the discharge pipe of the pump tower for LNG loading or unloading, and the pipe may be installed on the hull deck and subjected to a pipe cold test. good. If the amount of contraction and expansion displacement of the pipe measured by the displacement measuring device is within the allowable range, it can be determined to be normal.

Next, cool-down work is performed on the inside of the LNG cargo hold of the offshore structure (S204). This step (S204) may be performed using a refrigerant other than LNG, and liquefied nitrogen may be used as in the pipe cold test described above. Liquefied nitrogen can vaporize almost immediately upon contact with a room temperature LNG cargo hold and generate a convection phenomenon inside the LNG cargo hold. This step (S204) may include controlling the internal temperature of the LNG cargo hold to maintain −158° C.±5° C. while injecting liquefied nitrogen into the LNG cargo hold at room temperature.

Next, a warm-up operation is performed onshore to raise the internal temperature of the LNG cargo hold of the offshore structure to room temperature (S205). In this process (S205), the temperature inside the LNG cargo hold is raised by the heater (180, see FIG. 3), the fluid inside the LNG cargo hold is heated by the heater (180), and the fluid inside the LNG cargo hold is reintroduced. It may comprise the step of infusing.

Next, after sending out the fluid inside the LNG cargo hold of the offshore structure onshore and injecting dry air into the LNG cargo hold, the inside of the LNG cargo hold is visually inspected (S206 ). When the temperature inside the LNG cargo hold is raised to room temperature by the heater (180) described above, almost only gaseous nitrogen exists inside the LNG cargo hold. Therefore, since the operator must enter the LNG cargo hold for visual inspection, the nitrogen inside the LNG cargo hold is sent out and normal temperature dry air (oxygen concentration 20%) is injected into the LNG cargo hold. It will be.

Next, the secondary secondary barrier integrity test of the LNG cargo hold of the offshore structure is conducted onshore (S207). In this process (S207), nitrogen gas is filled in the lower heat insulation layer of the secondary barrier and the upper heat insulation layer of the secondary barrier, and different pressures are applied to each. The method may comprise measuring a change value and determining whether the secondary barrier is sound based on the measured pressure change value.

If the LNG cargo hold is of the Mark-III type, the secondary barrier is not constructed by welding, unlike the primary barrier, but is constructed by adhesive. As mentioned above, the reason why the secondary barrier integrity test is performed twice for the primary and secondary barriers is that after the primary secondary barrier integrity test at the time of construction of the LNG cargo hold, the LNG When liquefied nitrogen is injected into the cargo hold, the LNG cargo hold undergoes a rapid temperature change (hereinafter referred to as cold shock). At this time, since the secondary barrier material in the LNG cargo hold contracts and relaxes, it is necessary to confirm the integrity of the secondary barrier through the secondary barrier integrity test again.

That is, the above-mentioned primary secondary barrier integrity test process (S202) is performed under the condition that the LNG cargo hold construction process is completed, and the secondary secondary barrier integrity test process (S207) is performed under the condition that the LNG cargo hold is Performed under cold shock conditions. In the embodiment of the present invention, as described above, the inside of the LNG cargo hold is cooled down by liquefied nitrogen injection in the S204 process. A cold shock can be applied while maintaining the temperature at 5°C.

As described above, the LNG cargo hold test process of offshore structures can be performed onshore according to the embodiment of the present invention, thereby reducing costs and improving work efficiency. In particular, by doing onshore large-scale test work that had to be done offshore in the past, it is possible to increase the convenience, stability and efficiency of the work and move up the work schedule.

Also, the LNG cargo hold test process (S201 to S207) of the offshore structure described above may be performed in a yard (shipyard). That is, the above-described processes (S201 to S207) may be performed in the shipyard where the offshore structure is built onshore. efficiency.

After performing test operations onshore on the LNG cargo hold, as illustrated in Figure 1, the non-self-propelled offshore structure (e.g. FLNG) is offshore and the self-propelled offshore structure (e.g. , LNG carrier) may undergo the remaining LNG hold tests at the onshore terminal. In the following description, an FLNG is used as an offshore structure without self-navigation capability, and an LNG carrier as an offshore structure with self-navigation capability.

FIG. 2 is a flow chart showing the LNG cargo hold test process of offshore structures performed after the LNG cargo hold test of FIG.

Referring to FIG. 2, the LNG cargo hold is filled with LNG, and the pump inside the LNG cargo hold is subjected to a pumping test (S208). For example, in the case of FLNG without self-propulsion capability, this process (S208) is performed with the FLNG arranged offshore, and in the case of an LNG carrier with self-propulsion capability, this process is performed with the LNG carrier deployed at a land terminal. (S208) is performed.

In the case of FLNG, after LNG is produced offshore, the produced LNG is filled inside the LNG cargo hold, and a pumping test is immediately conducted on the pump (not shown) installed inside the LNG cargo hold. good too. Also, as another example, the FLNG may perform a pumping test on a pump provided inside the LNG cargo hold after the LNG is supplied and demanded by the LNG bunkering method.

At this time, the above-mentioned pump may be an LNG off-loading pump provided in a pump tower, and the test may be performed in a state where the inside of the LNG cargo hold is filled with LNG.

Next, a test of offloading the LNG inside the LNG cargo hold to another LNG ship using the loading arm is performed (S209). This process (S209) is similarly performed offshore in the case of FLNG, and in the terminal in the case of LNG carriers.

In the LNG cargo hold test process (S208 to S209) of the offshore structure described above, the test was performed using LNG. It is also possible to perform the test using the refrigerant used in S204).

In this case, the above-described cool-down process (S204) may be performed, then the onshore pumping test and loading arm test may be performed, and then the above-described warm-up operation (S205) may be performed. Alternatively, the second secondary barrier integrity test process (S207) may be performed, and then the pumping test and loading arm test may be performed onshore. At this time, the inside of the LNG cargo hold is filled with refrigerant onshore, a pumping test is performed on the pump inside the LNG cargo hold, and the loading arm is used to offload the refrigerant inside the LNG cargo hold to another LNG ship. Do a test to Through this, pumping tests and loading arm tests may be performed onshore without the need to move offshore structures containing FLNG offshore.

FIG. 3 illustrates in block diagram form a liquefied nitrogen supply system according to an embodiment of the invention.

Referring to FIG. 3, a liquefied nitrogen supply system according to an embodiment of the present invention provides onshore liquefied nitrogen for use in LNG cargo hold (101) test operations of the offshore structure (100) of FIG. do.

In such a liquefied nitrogen supply system, liquefied nitrogen is supplied from a liquefied nitrogen production unit (105) that produces liquefied nitrogen, and is moved to a buffer tank (120) to supply liquefied nitrogen to the buffer tank (120). 110), a buffer tank (120) that supplies liquefied nitrogen to the LNG cargo hold (101), and the internal temperature of the LNG cargo hold (101) is maintained within a set temperature range for a set time. It includes a control unit (130) that regulates the amount of liquefied nitrogen injected inside the LNG cargo hold (101).

In addition, the liquefied nitrogen supply system includes a liquefied nitrogen injection pipe (140) that connects the buffer tank (120) and the LNG cargo hold (101), and the liquefied nitrogen supplied through the liquefied nitrogen injection pipe (140) into the LNG cargo hold ( 101), a control valve (160) arranged in the liquefied nitrogen injection pipe (140), and a temperature sensor (170) for measuring the temperature in the LNG cargo hold (101). may include

In addition, the liquid nitrogen supply system includes a safety valve (193, Safety Valve) and a safety device (195, Safety System) prepared for emergency situations and abnormal conditions in the liquid nitrogen injection pipe (140). More than one may be provided.

Each component will be specifically described below.

The liquefied nitrogen producer (105) may be made by a gas specialist. The liquefied nitrogen produced in the liquefied nitrogen production unit (105) is stored in tank trucks (110) and transported to where the onshore offshore structure (100) is located.

The buffer tank (120) may be provided in a movable trailer type, liquefied nitrogen is supplied from the tank truck (110), and the liquefied nitrogen is stably supplied to the LNG cargo hold (101) side of the offshore structure (100). may be supplied. The buffer tank (120), like the tank truck (110), may be transported to where the onshore offshore structure (100) is located. Although not shown, the buffer tank (120) is equipped with facilities such as a cryogenic pump, a vaporizer, and a mixer, so that liquefied nitrogen can be delivered to the LNG cargo hold (101) side.

The controller (130) controls the degree of opening and closing of the control valve (160) based on the temperature value measured by the temperature sensor (170), and the LNG is injected into the cargo hold (101) by the injector (150). Adjust the amount of liquid nitrogen. For example, the control unit (130) may control the degree of opening and closing of the control valve (160) so that the temperature inside the LNG cargo hold (101) is adjusted within the range of -158°C ±5°C. Through this, the internal temperature of the LNG cargo hold (101) may be maintained at approximately the LNG temperature level (approximately −163° C.), and test operations are performed onshore using liquefied nitrogen instead of LNG during LNG cargo hold testing. may be broken. That is, by maintaining the liquefied nitrogen at the LNG temperature level, it is possible to show the same effect as a cargo hold test using LNG.

Specifically, when cooling down the inside of the LNG cargo hold (101), when liquefied nitrogen having about -195 ° C is injected into the LNG cargo hold (101) at room temperature, the LNG cargo hold (101) The temperature is gradually lowered. Liquefied nitrogen, when it comes into contact with the room temperature LNG cargo hold (101), can almost immediately evaporate and generate a convection phenomenon inside the LNG cargo hold (101). At this time, when adjusting the speed of lowering the temperature of the LNG cargo hold (101) according to the amount of liquefied nitrogen injected, if the temperature of the LNG cargo hold (101) drops too rapidly, the configuration of the LNG cargo hold (101) The amount of liquefied nitrogen injected may be adjusted at a preset rate as this may cause severe damage to the elements.

Liquid nitrogen may be converted to a gaseous state as soon as the temperature rises after being injected to the inner wall side of the room temperature LNG cargo hold (101). Continuing the cool-down operation for the inside of the LNG cargo hold (101) will reach about -158°C, and the injection part (150) can stop the injection of liquefied nitrogen from this point. . At this time, the controller (130) closes the control valve (160) based on the temperature value measured by the temperature sensor (170), and the liquid nitrogen injection by the injector (150) may be interrupted. .

Then, the control unit (130) maintains the temperature fluctuation range inside the LNG cargo hold (101) at -158°C ± 5°C for 22 hours according to preset cargo hold cool-down conditions. good too. That is, after the liquefied nitrogen injection to the inside of the LNG cargo hold (101) is interrupted, the temperature inside the LNG cargo hold (101) rises little by little over time. opens the control valve (160) based on the temperature value measured by the temperature sensor (170), and the injection part (150) gradually injects liquefied nitrogen into the LNG cargo hold (101) along the way. The temperature fluctuation range may be maintained at -158°C ± 5°C for 22 hours according to preset cargo hold cool-down conditions.

The liquefied nitrogen injection pipe (140) supplies the liquefied nitrogen supplied from the buffer tank (120) to the LNG cargo hold (101) side, and is provided so as to withstand cryogenic liquefied gas. The liquid nitrogen injection pipe (140) may be transported along with the buffer tank (120) to where the onshore offshore structure (100) is located. Since the tank truck (110), the buffer tank (120) and the liquefied nitrogen injection pipe (140) are movably provided as described above, the LNG cargo hold (101) test operation of the offshore structure (100) can be carried out onshore. , i.e. not only at the shipyard, but also at other docking points outside of this.

The injection part (150) may include a nozzle for injecting liquefied nitrogen supplied through the liquefied nitrogen injection pipe (140) into the LNG cargo hold (101).

A control valve (160) is arranged in the liquefied nitrogen injection pipe (140) to regulate the flow rate of liquefied nitrogen supplied to the LNG cargo hold (101).

A temperature sensor (170) measures the temperature inside the LNG cargo hold (101), which changes due to the injection of liquefied nitrogen into the LNG cargo hold (101).

The safety valve (193) and the safety device (195) protect the equipment against overpressure phenomenon of the supply equipment (liquefied nitrogen supply system) due to interruption of the liquefied nitrogen supply and abnormal conditions due to emergency situations. can protect

One or more of the safety valve (193) and the safety device (195) may be arranged at one or more of the front and rear ends of the control valve (160) of the liquefied nitrogen injection pipe (140).

The safety valve (193) may include, for example, a PRV (Pressure Relief Valve) for equipment overpressure and a PVV (Pressure Vacuum Valve) for low pressure (vacuum).

In addition, the safety device (195) may include one or more of means such as alarm for abnormal situations, automatic supply and interruption.

For example, the equipment overpressure phenomenon described above can be caused by supplying liquefied nitrogen to the cargo hold (ship) using a transfer means such as a pump, while supplying liquefied nitrogen when supply and demand in the cargo hold (ship) is unavailable due to an emergency. It may occur in piping and equipment that In addition, the overpressure phenomenon may be caused by a surge phenomenon caused by sudden valve operation or operation change during normal operation. In addition, the overpressure phenomenon may occur when the cargo hold (ship) is out of supply and demand for a long period of time, and when the liquefied nitrogen in the supply equipment is vaporized, the supply pipe and the equipment are out of the operating range.

In addition, the above-mentioned low pressure (vacuum) phenomenon occurs when the flow rate that can be supplied to the ship from the liquefied nitrogen supply equipment is exceeded, or when the liquefied nitrogen supply equipment is in short supply, the operation of transfer equipment such as pumps may occur. can occur at times.

Embodiments of the present invention can effectively provide for the overpressure and underpressure (vacuum) events described above through safety valve (193) and safety device (195).

Thus, liquid nitrogen is injected into the LNG cargo hold (101) of the offshore structure (100) while being maintained at the LNG temperature level instead of LNG by the liquid nitrogen supply system according to the embodiment of the present invention. and effective onshore test operations for LNG cargo holds of the offshore structure (100).

Specific implementations have been shown and described above. However, the present invention is not limited to the above embodiments, and a person having ordinary knowledge in the technical field to which the invention belongs may deviate from the gist of the technical idea of the invention described in the following claims. You can make as many changes as you like without any hassle.

Claims (14)

(a) after construction of an LNG cargo hold of an FLNG, subjecting a secondary barrier to said LNG cargo hold to a primary integrity test;
(b) performing cool-down operations on the interior of said LNG cargo hold;
(c) subjecting the secondary barriers of the LNG cargo hold to a secondary integrity test;
The steps (a) to (c) are performed on the LNG cargo hold of the FLNG with the FLNG located onshore,
The LNG cargo hold test method, wherein the step (b) is performed using any refrigerant other than LNG. (a) after construction of a ship's LNG cargo hold, subjecting a secondary barrier to said LNG cargo hold to a primary integrity test;
(b) performing a pipe cold test on pipes connected to the LNG cargo hold for LNG loading or unloading;
(c) performing cool-down operations on the interior of said LNG cargo hold;
(d) subjecting the secondary barriers of the LNG cargo hold to a secondary integrity test,
The steps (a)-(d) are performed on an LNG cargo hold of the vessel with the vessel located onshore,
The LNG cargo hold test method, wherein the steps (b) and (c) are performed using liquefied nitrogen. In the step of performing the cool-down operation, liquefied nitrogen is injected into the LNG cargo hold at room temperature, and the internal temperature of the LNG cargo hold is controlled to maintain −158° C.±5° C. for a set time. 3. The LNG cargo hold testing method of claim 1 or claim 2, comprising the step of: After performing the cool-down work, the inside of the LNG cargo hold is filled with liquefied nitrogen onshore, and a pumping test is performed on the pump inside the LNG cargo hold,
3. The LNG cargo hold test method according to claim 1 or 2, further comprising a test step of offloading the liquefied nitrogen inside the LNG cargo hold to another vessel using a loading arm. After the step of performing the second integrity test, filling the inside of the LNG cargo hold with LNG and performing a pumping test on the pump inside the LNG cargo hold;
further comprising a test step of offloading the LNG within said LNG cargo hold to another vessel using a loading arm;
3. The LNG cargo hold test method according to claim 1 or 2, wherein the FLNG is placed offshore, and the self-propelled vessel is placed at a land terminal. . (a) conducting a primary barrier integrity test of the LNG cargo hold;
(b) subjecting a secondary barrier to the LNG cargo hold to a primary integrity test;
(c) performing a piping cold test on piping connected to said LNG cargo hold;
(d) performing cool-down operations on the interior of said LNG cargo hold;
(e) performing a warm-up operation to raise the internal temperature of the LNG cargo hold to normal temperature;
(f) performing a visual inspection of the interior of the LNG cargo hold after the interior of the LNG cargo hold has been evacuated and dry air has been injected into the interior of the LNG cargo hold;
(g) subjecting the secondary barriers of the LNG cargo hold to a secondary integrity test;
The steps (a) to (g) are an LNG cargo hold test method performed on an LNG cargo hold of an offshore structure with the offshore structure including a ship located onshore. The steps (b) and (g) include filling nitrogen gas into the lower heat-insulating layer of the secondary barrier and the upper heat-insulating layer of the secondary barrier and applying different pressures thereto;
measuring the pressure change value between the lower heat-retaining layer and the upper heat-retaining layer after a set time;
7. The LNG cargo hold testing method according to claim 6, comprising the step of determining whether said secondary barrier is sound based on said measured value. The step (d) includes injecting refrigerant into the LNG cargo hold to control the internal temperature of the LNG cargo hold to maintain −158° C.±5° C. for a preset time. ,
The LNG cargo hold test method according to claim 6. In the primary barrier integrity test, an ammonia reactant is applied to a welded portion of the primary barrier, a space between the primary barrier and the secondary barrier is filled with ammonia gas, and discoloration of the ammonia reactive material is checked. determining whether the primary barrier is sound based on the presence or absence thereof;
9. The LNG cargo hold test according to claim 8, wherein the piping cold test comprises a process of flowing the refrigerant through the piping and measuring whether the amount of contraction and expansion displacement of the piping is within an allowable range. Method. A marine structure to which the LNG cargo hold test method according to any one of claims 6 to 9 is applied. a buffer tank for supplying liquefied nitrogen to the LNG cargo hold for LNG cargo hold test operations of an offshore structure located onshore;
a controller that adjusts the amount of liquefied nitrogen injected into the LNG cargo hold such that the temperature inside the LNG cargo hold is maintained within a set temperature range for a set time. Liquid nitrogen supply system for structures. 12. Liquefaction of the offshore structure according to claim 11, further comprising a tank truck supplied with the liquefied nitrogen from a liquefied nitrogen production unit, moved to a yard where the buffer tank is provided, and supplying the liquefied nitrogen to the buffer tank. Nitrogen supply system. a liquefied nitrogen injection pipe connecting the buffer tank and the LNG cargo hold;
an injection unit for cooling down the LNG cargo hold by injecting the liquefied nitrogen supplied through the liquefied nitrogen injection pipe into the LNG cargo hold;
a control valve disposed in the liquefied nitrogen injection pipe;
further comprising a temperature sensor for measuring the temperature inside said LNG cargo hold;
12. The control unit according to claim 11, wherein the control unit controls the degree of opening and closing of the control valve based on the measured temperature value, and adjusts the amount of liquefied nitrogen injected into the LNG cargo hold by the injection unit. A liquefied nitrogen supply system for the marine structure described. 14. The offshore structure according to claim 13, wherein the control unit adjusts the amount of liquefied nitrogen injected into the LNG cargo hold so that the internal temperature of the LNG cargo hold is maintained at -158°C ± 5°C. liquefied nitrogen supply system.

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