JP2002312873A - System for monitoring heat-proof section of lng ship cargo tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more precisely monitor an abnormal state. SOLUTION: A system is provided with a first pressure gauge 23 which measures a primary space pressure of primary spaces 7-1 to 7-5, a second pressure gauge 23 which measures a secondary space pressure of secondary spaces 8-1 to 8-5, a third pressure gauge 23 which measures atmospheric pressure, and a measuring computer 21 which discriminates an abnormal state on the basis of the primary space pressure, the secondary space pressure, atmospheric pressure. The abnormal state is quickly found by the measuring computer 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LNG ship cargo tank thermal compartment monitoring system, and more particularly, to an LNG carrier cargo tank thermal compartment monitoring system used during repair work on a membrane type LNG ship. . It is also used to protect cargo tanks during repairs, monitor tank conditions, and monitor tank controls during repairs.

[0002]

2. Description of the Related Art LNG carriers transport natural gas by liquefying it by cooling it to about -162 ° C. The LNG ship has a plurality of cargo tanks for storing liquefied natural gas (hereinafter abbreviated as “LNG”), and each cargo tank 1
03-i (i = 1, 2, 3,..., N) are, as shown in FIG. 11, heat insulating layers 107-i and 108 having a two-layer structure.
-I. These two heat insulating layers 107-i, 10
A heat insulating material is enclosed in 8-i. The inner membrane, which is the part that contacts LNG, is a primary membrane 111,
The outer membrane of the primary membrane is the secondary membrane 1
Called 12. Two heat insulation layers 107-i and 108-i
Are the primary spaces 107-
i, called secondary space 108-i. As the heat insulating material, a plywood, a pearlite powder material, or the like is used. The membrane used is an extremely thin steel material having an average thickness of 0.7 mm.

[0003] The cargo tank 103-i of the LNG carrier is subject to severe adverse conditions such as dynamic fluid pressure effects due to stormy waves during operation, sloshing phenomena, and fatigue phenomena due to repeated thermal shrinkage at the pressure concentrated portion of the membrane welded portion. And corrosion causes damage to the membranes 111, 112, exemplified by cracks. When the membranes 111 and 112 are damaged, the liquid in the cargo tank 103-i passes through the primary membrane 111 and the primary space 107.
-Penetrates i and evaporates immediately from temperature and pressure differences. Although the structures are completely different between the gas transport method and the technigas method, the heat insulation layers 107-i and 108-i of both methods are filled with nitrogen gas and are maintained in an inactive state.

[0004] A methane gas detector is installed in the heat insulation layers 107-i and 108-i, and LNG is applied to the heat insulation layers 10-i.
If the gas concentration permeates 7-i and 108-i and exceeds a certain level, leakage can be detected. It is mandatory for the crew of an LNG ship to detect and record the gas concentration during operation. When the gas concentration increases during operation, the structure is such that a safe state can be achieved by injecting nitrogen gas into the primary space 107-i and increasing the nitrogen gas concentration. However, if this damage is left for a long time, the extent of the damage is expanded, and only the measures taken by injecting nitrogen gas can cause the cargo tank 103
-I cannot be maintained healthy. Therefore,
Repair work is carried out every five years, and a global test is conducted at this time.

In the global test, during repair work, SO
The presence or absence of leakage of the membrane tank 103-i is measured based on the LAS rules. That is, the membrane 11
It is checked whether 1,112 has a penetration defect. The measuring method is performed by reducing the pressure of the two heat-insulating layers 107-i and 108-i, providing a pressure difference between the primary space and the secondary space, and fixing the pressure at a certain place. After reducing the pressure, close the valve and maintain the pressure. After that, the pressures of the heat insulation layers 107-i and 108-i, the temperature in the cargo tank 103-i, the temperature in the ballast tank 109, the temperature of the outside air, and the outside air pressure are measured for 12 hours or more.
Leaks are determined based on data for 10 hours out of 4 hours.
That is, the two heat insulating layers 107-i, 1
When the pressure of 08-i rises despite a small change in temperature, for example, it is presumed that the membranes 111 and 112 have penetration defects.

[0006] The pressure in the heat insulation sections 107-i and 108-i is monitored by an operator using a mercury column or a submersible pressure gauge, and the temperature and humidity are also monitored by the operator. Such monitoring results in human errors in the measurements and takes time to acquire all the measurements. Furthermore, because it is impossible to measure temperature and pressure at the same time,
There is a problem with the accuracy of the guess.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an LNG carrier cargo tank heat insulation compartment monitoring system for more accurate monitoring. Another object of the present invention is to provide an LNG ship cargo tank thermal insulation section monitoring system that measures temperature and pressure at the same time. Still another object of the present invention is to provide an LNG ship cargo tank thermal insulation section monitoring system that reduces running costs. It is still another object of the present invention to provide an LNG carrier cargo tank thermal compartment monitoring system that prevents membrane destruction. Still another object of the present invention is to provide an LNG carrier cargo tank heat insulation zone monitoring system for more reliably estimating the presence or absence of a membrane penetration defect.

[0008]

Means for solving the problem are described as follows. The technical items appearing in the expression are appended with numbers, symbols, etc. in parentheses (). The numbers, symbols, and the like are technical items that constitute at least one embodiment or a plurality of the embodiments of the present invention, in particular, the embodiments or the examples. Corresponds to the reference numerals, reference symbols, and the like assigned to the technical matters expressed in the drawings corresponding to the above. Such reference numbers and reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments or the examples.

The LNG carrier cargo tank thermal insulation section monitoring system (1) according to the present invention comprises a primary space (7-
A first pressure gauge (23) for measuring a primary space pressure which is a pressure of 1 to 7-5) and a second pressure gauge for measuring a secondary space pressure which is a pressure of a secondary space (8-1 to 8-5). (23), a third pressure gauge (23) for measuring the atmospheric pressure, a primary space pressure,
A measurement computer (21) for determining whether or not an abnormal situation is present based on the secondary space pressure and the atmospheric pressure. The primary space pressure, the secondary space pressure, and the atmospheric pressure can be quickly analyzed by the measurement computer (21). Such a quick measurement can detect an abnormal situation immediately.

It is preferable that a state where the primary space pressure exceeds the atmospheric pressure is determined to be an abnormal situation. It is preferable that a state where the secondary space pressure exceeds the primary space pressure is determined to be an abnormal situation. It is preferable that a state where the amount of change in the primary space pressure per unit time exceeds a predetermined amount of change is determined to be an abnormal situation. It is preferable that a state in which the amount of change in the secondary space pressure per unit time exceeds a predetermined amount of change is determined to be an abnormal situation.

A cargo tank thermometer (5-1 to 5-5) for measuring the temperature of the cargo tank (3-1 to 3-5), which is the temperature inside the cargo tank (3-1 to 3-5), is further provided. The measurement computer (21) is equipped with a cargo tank (3).
-1 to 3-5) When the temperature is equal to or higher than a predetermined temperature, it is preferable to determine that an abnormal situation has occurred.

A ballast tank thermometer (13) for measuring the temperature of the ballast tank (9), which is the temperature inside the ballast tank (9), is further provided.
1) is based on the primary space pressure, the secondary space pressure, the atmospheric pressure, the temperature of the cargo tank (3-1 to 3-5) and the temperature of the ballast tank (9). Space (7-
It is inferred whether the membrane provided between 1 and 7-5) has a penetration defect. The measurement computer (21) calculates the pressure change of the primary space pressure,
It is presumed that a sudden pressure change excluding the pressure change due to the temperature change from the pressure change of the secondary space pressure is caused by the penetration defect. Such a guess is more certain.

[0013] Primary space (7-1 to 7-5)
And valves (15-1 to 15-5) interposed between the secondary space (8-1 to 8-5) and
When the difference between the secondary space pressure and the primary space pressure is smaller than a predetermined pressure difference and the valves are being reversed, the valves (15-1 to 15-5) are connected to the primary space (7-1 to 7-5) and the secondary space. (8-
1 to 8-5), and when the difference is larger than a predetermined pressure difference, the primary space (7-1 to 7-5) and the secondary space (8-1 to 8-5) are closed. The cargo tank (3-1) is controlled by the valves (15-1 to 15-5).
3-5), primary space (7-1 to 7-5)
In addition, the membrane that separates the secondary spaces (8-1 to 8-5) is prevented from being destroyed.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of an NG ship cargo tank thermal insulation section monitoring system will be described. As shown in FIG. 1, the LNG carrier cargo tank thermal insulation section monitoring system 1 is mounted on a membrane type LNG carrier 2. The LNG ship 2 includes a plurality of cargo tanks 3-1 to 3-5. The LNG ship cargo tank thermal insulation section monitoring system 1 includes a center 4, a plurality of temperature / humidity meters 5-1 to 5-5, and an electric wire 6 connecting the center 4 to the plurality of temperature / humidity meters 5-1 to 5-5. -1 to 6
-5. The center 4 is temporarily installed only during a period in which the repair work of the LNG ship 2 is performed. Temperature and humidity meter 5-i
(I = 1,2,3,4,5) are installed inside the cargo tank 3-i, measure the temperature and humidity inside the cargo tank 3-i, and measure the temperature and humidity respectively with the voltage. And output. Such a temperature / humidity meter 5-i is well known and is commercially available. The electric wire 6-i is a thermometer / hygrometer 3-
The voltage output by i is transmitted to the center 4.

FIG. 2 shows the cargo tank 3-i in detail. The cargo tank 3-i has a primary space 7-i on the outside, and further has a secondary space 8-i on the outside. A ballast tank 9 is provided further outside the cargo tank 3-i. The LNG carrier cargo tank thermal insulation section monitoring system 1 further includes an air tube 11-i, an air tube 12-i, and a valve 15-i for each cargo tank 3-i, and a thermometer 13
And an electric wire 14. Air tube 11-i
Connects the primary space 7-i and the center 4 and transmits the pressure of the primary space 7-i to the center 4. The air tube 12-i connects the secondary space 8-i to the center 4 and transmits the pressure of the secondary space 8-i to the center 4.

The valve 15-i is connected to the primary space 7-.
i and the secondary space 8-i, and has two positions, an open position and a closed position. Valve 15-i is
When in the open position, the primary space 7-i and the secondary space 8-i are electrically connected, and when in the closed position, the primary space 7-i and the secondary space 8-i are closed.

The thermometer 13 is installed inside the ballast tank 9, measures the temperature inside the ballast tank 9, converts the temperature and humidity into a voltage, and outputs the voltage. Electric wire 14
Indicates the voltage output from the temperature / humidity meter 3-i at the center 4
To communicate.

When LNG is stored in the cargo tank 3-i, the primary space 7-i and the secondary space 8-i have substantially equal internal pressures and are slightly higher than the atmospheric pressure. During the repair work of the LNG ship 2, the cargo tank 3-i is filled with air and workers enter the cargo tank 3-i, the primary sparse 7-i and the secondary sparse 8-i are separated by a membrane. Inspect for defects. At this time, the cargo tank 3-
The pressure inside i is approximately atmospheric pressure. At this time, the primary space 7-i and the secondary space 8-i are decompressed so that even if an operator gets on the membrane at the bottom of the cargo tank 3-i, the primary space 7-i and the secondary space 8-i are not destroyed.

FIG. 3 shows the center 4 in detail. The center 4 includes a measurement computer 21 and an input / output board 2
2, a plurality of pressure transducers 23, a temperature / humidity meter 24 for measuring the temperature and humidity of the environment, a modem 25, a telephone 26
And a power supply 27. Computer 21 for measurement
Is an information processing device exemplified by a personal computer, and includes an input device, a display device, and a printing device. The temperature / humidity meter 24 is installed outside, and the temperature / humidity meter 5
As in -i, the temperature and humidity of the environment are measured, and the temperature and humidity are converted into voltages and output.

The plurality of pressure transducers 23 are air tubes 11-1 to 11-5, 12-1 to 1 respectively.
The pressure and atmospheric pressure in 2-5 are measured, and the pressure is converted into a voltage and output. As the pressure transducer 23, a capacitance manometer of a single side dual electrode / AC bridge circuit type is exemplified. In general,
Although the pressure transducer has a very small amount due to the coefficient of thermal expansion of the material, a geometrical change occurs and a measurement error occurs. Furthermore, when the pressure transducer is of the type that measures absolute pressure, measurement errors occur because the reference portion is deformed by temperature. From this, in general, to compensate for temperature, a type in which a temperature sensor circuit is provided in the reference portion and the output signal is compared with the temperature change to compensate for the temperature can be considered. In this case, the performance due to the thermal lag is improved. I can only do it. Therefore, by wrapping the entire sensor in an environment where the temperature is controlled, the change in the actual sound felt by the sensor can be suppressed to the minimum.

The input / output board 22 includes temperature / humidity meters 5-1 to 5-1.
5-5, 24, A / D conversion of signals from the thermometer 13 and the pressure transducer 23 into digital signals that can be processed by a computer. The power supply 27 has a temperature / humidity meter 5-1 to
5-5, 24, power for operating the thermometer 13 and the pressure transducer 23 is supplied.

FIG. 4 shows the measuring computer 21 in detail. The measurement computer 21 includes a main program 31, a temperature / humidity measurement program 32, a pressure measurement program 33, a coping program 34, and a data processing program 35. The temperature / humidity measurement program 32 is a subprogram that operates in accordance with another program, and includes a temperature / humidity meter 5-1 to 5-5 and a temperature / humidity meter 2
Temperature and humidity are derived based on the output of the thermometer 1 and the thermometer 1
Then, the temperature is derived based on the output of No. 3. The pressure measurement program 33 is a subprogram that operates according to another program, and derives a pressure based on the output of the pressure transducer 23.

FIG. 5 shows the operation of the measurement computer 21 executed by the main program 31. The main program 31 is started at the time of the global test. That is, first, the secondary spaces 8-1 to 8-8
-5 and the primary sparses 7-1 to 7-5 are decompressed to a negative pressure from the atmospheric pressure. After the pressure is reduced, the primary space 7-i and the secondary space 8-i are in a state where the pressure of the secondary space 8-i is about minus several hundred mb and lower than the pressure of the primary space 7-i. i is closed to the outside and its pressure is maintained. In such a state, the main program 31 starts.

When the main program 31 is started, an initial setting is executed (step S1). Thereafter, a time at which measurement is started and a time at which measurement is ended are input (step S).
2). Here, if the time setting does not exist,
The main program 31 is locked so as not to proceed, and an error is displayed. Further, a file name of a file in which measured values and the like are stored is set. The file name is automatically determined based on the ship name and the measurement time.

When it is time to start the measurement, the pressure, temperature and humidity of the outside air are measured (step S3). Next, the pressures of the primary space 7-i and the secondary space 8-i are measured (Step S4). Further, the temperature and humidity in the cargo tank 3-i and the temperature of the ballast tank 9 are measured (Step S5).

Based on the measurement results of steps S3 to S5, it is determined whether an abnormal situation has occurred (step S6). That is, when the pressure in the primary space 7-i or the pressure in the secondary space 8-i is higher than the outside air pressure, and when the pressure in the secondary space 8-i is higher than the pressure in the primary space 7-i,
The fluctuation of the pressure in the primary space 7-i or the secondary space 8-i is 3 mb / min. When it is larger than or the temperature inside the cargo tank 3-i is 40 ° C
When this occurs, it is determined that an abnormal situation has occurred.

When it is determined that the situation is abnormal (step S6; YES), re-measurement is executed. The re-measurement is performed in the same manner as in steps S3 to S5.
Temperature and humidity are measured. Primary space 7-
i, the pressure in the secondary space 8-i is measured.
The temperature and humidity in the cargo tank 3-i and the temperature of the ballast tank 9 are measured.

Based on the result of the re-measurement, it is determined again whether or not an abnormal situation has occurred (step S8).
When it is determined that the situation is abnormal (step S8; YE
S), the measurement result is printed out by the printing device (step S9). An alarm is sounded and an abnormal situation message is displayed on the screen to notify the operator that an abnormal situation has occurred. If the problem is not solved (step S11; NO), and within 5 minutes from the occurrence of the abnormal situation (step S12; YES), step S10 is executed again. The problem is not solved (step S11; N
O), when five minutes or more have passed since the occurrence of the abnormal situation (step S12; NO), the pager (registered trademark) of the worker or the manager of the LNG ship cargo tank thermal insulation section monitoring system 1 is called (step S13).

When it is determined that there is no abnormal situation (step S6; NO), when it is determined that there is no abnormal situation in re-measurement (step S8; NO), the problem is solved (step S11; YES), or After calling the pager, the measurement result is recorded in the measurement computer 21 (step S14) and displayed on the screen (step S1).
5). If the time to end the measurement has not passed (step S16; NO), the process enters a loop in which step S3 and subsequent steps are executed again. This loop is executed every 12 seconds, and the measurement computer 21 acquires and stores the measured values every 12 seconds. If the time to end the measurement has passed (step S
16; YES), this flow ends.

The main computer 31 allows the measuring computer 21 to operate unattended from start to finish.
For this reason, there is no need for an operator who goes around and measures each measured value, and the running cost can be reduced.

FIG. 6 shows the operation of measuring the atmosphere of the environment in detail. First, an initial setting is executed (step S21), and the temperature of the outside air is measured (step S2).
2). This measurement is performed by the temperature / humidity meter 24, and a voltage corresponding to the temperature of the outside air is output. The input / output board 22 converts the voltage into a digital signal.
The measurement computer 21 has a function for associating the output of the thermo-hygrometer 24 with the temperature in advance, and converts the digital signal into a corresponding temperature unit (step S23).

The humidity of the outside air is measured (step S2).
4). This measurement is performed by the temperature / humidity meter 24, and a voltage corresponding to the humidity of the outside air is output. The input / output board 22 converts the voltage into a digital signal.
The measurement computer 21 has a function for associating the output of the thermometer / humidity meter 24 with the humidity in advance, and converts the digital signal into the corresponding humidity as a unit (step S25).

The pressure of the outside air is measured (step S2)
6). This measurement is performed by the pressure transducer 23. The pressure transducer 23 outputs a voltage corresponding to the atmospheric pressure. The input / output board 22 converts the voltage into a digital signal. The measurement computer 21 has a function for associating the output of the pressure transducer 23 with the pressure in advance, and converts the digital signal into a corresponding pressure unit (step S27).

FIG. 7 shows in detail the operation of measuring the pressure in the primary space 7-i and the secondary space 8-i. First, initial settings are performed (step S31). The pressure in the primary spaces 7-1 to 7-5 is measured by the pressure transducer 23 (Step S32). The pressure transducer 23 outputs a voltage corresponding to the pressure. The measurement computer 21 converts the digital signal into a corresponding pressure (step S33).

The pressure in the secondary spaces 8-1 to 8-5 is measured by the pressure transducer 23 (step S34). The pressure transducer 23 outputs a voltage corresponding to the pressure. The measurement computer 21 converts the digital signal into a corresponding humidity (step S35).

It is determined whether or not an abnormal situation is present based on the measured values. When the current measurement is a re-measurement and the result of the measurement indicates an abnormal situation (step S36; YE
S), it is considered that an abnormal situation has occurred (step S3)
7). If it is not a re-measurement (step S36; NO),
When the pressure in the primary space 7-i is higher than the atmospheric pressure (step S38; YES), it is considered that the first abnormal situation has occurred (step S39). The first abnormal situation is an event indicating that there is a possibility that the situation is abnormal. When the first abnormal situation occurs, step S is performed again.
32 is executed to measure the pressure in the primary space 7-i and the pressure in the secondary space 8-i.

When the pressure in the primary space 7-i is equal to or lower than the atmospheric pressure (step S38; NO), the pressure in the secondary space 8-i is reduced to the primary space 7-i.
-I or more (step S40; YE
S), it is considered that the first abnormal situation has occurred (step S41). Thereafter, step S32 is executed again, and the pressure in the primary space 7-i and the pressure in the secondary space 8-i are measured.

When the pressure in the secondary space 8-i is smaller than the pressure in the primary space 7-i (step S40; NO), the change per minute in the pressure in the primary space 7-i is 3 mb / min. When it is larger (step S42; YES), it is considered that the first abnormal situation has occurred (step S43). The amount of change is derived based on the previously measured pressure of the primary space 7-i and the currently measured pressure of the primary space 7-i. Thereafter, step S32 is performed again.
Is executed, and the pressure in the primary space 7-i and the pressure in the secondary space 8-i are measured.

The change per minute in the pressure of the primary space 7-i is 3 mb / min. If it is below (step S42; NO), the secondary space 8-
i, the change per minute of the pressure is 3 mb / min. When it is larger (step S44; YES), it is considered that the first abnormal situation has occurred (step S45). This change amount is calculated based on the secondary space 8-
pressure i and secondary space 8-i measured this time
And is derived based on the pressure of Thereafter, step S32 is executed again, and the pressure in the primary space 7-i and the pressure in the secondary space 8-i are measured.

The amount of change in the pressure of the secondary space 8-i per minute is 3 mb / min. If the following is true (step S42; NO), this flow ends.

FIG. 8 shows the operation of the measurement computer 21 executed by the coping program 34 in detail. When an abnormal situation occurs (step S37), this flow starts. When the flow starts, a timer starts. The measurement computer 21 displays on the screen that an abnormal situation has occurred (step S51), and sounds an alarm (step S52). When the operator notices the occurrence of an abnormal situation by this screen display or this alarm, the operator deals with the abnormal situation. The operator cancels the display of the screen and the sounding of the alarm when the countermeasure is completed. The timer is within 5 minutes (step S53;
NO), when the display of the screen indicating the abnormal situation and the sounding of the alarm are not canceled (step S54; N)
O), Step S51 is executed again.

When the timer indicates 5 minutes or more (step S53; YES), an external alarm is sounded (step S55), and the pager of the worker or the manager is called (step S56). The called worker or manager deals with the abnormal situation.

After calling the pager (step S
56) or when the display of the screen indicating the abnormal situation and the sounding of the alarm are canceled (step S54;
NO), information on the abnormal situation is printed out (step S57). A log is recorded (step S58).

FIG. 9 shows the operation of the measurement computer 21 by the data processing program 35 in detail. The measured data is represented in a text format in which each measured value every 12 seconds is separated by a tab. First, initialization is performed (step S60). The file selected by the user is read (step S61). The read file data is processed into spreadsheet type data for raw data (step S62). The processed data is divided into data for each cargo tank 5-i (step S63). The divided data is further processed into hourly data (step S6).
4).

If all the measured times are less than 10 hours (step S65; NO), the average of the hourly measured values of the cargo tank pressure is calculated (step S65).
66). If all the measured times are equal to or longer than 10 hours (step S65; YES), only the measured values for 10 hours out of all the measured times are extracted, and the pressure of the cargo tank is measured every hour from the extracted data. An average of the values is calculated (step S67).

A graph is created based on the calculated average of the measured values every hour (step S69). further,
Based on the average, it is estimated whether the membrane has a penetration defect. That is, among the observed pressure changes, a sudden pressure change excluding a pressure change due to a temperature change is determined to be due to a penetration defect. Such estimation makes it possible to distinguish between a pressure change due to a temperature change and a pressure change due to a penetration defect, and is more reliable. When the graph is created, the raw data sheet is deleted (step S70).

Such data processing is performed by the cargo tank 3
-I or a pressure change between the primary space 7-i and the secondary space 8-i due to a temperature change in the ballast tank 9 is not mistaken for a pressure change due to a defect in the membrane, and the accuracy of estimating the presence or absence of a defect in the membrane is improved. .

The valve 15-i is connected to the computer 21 for measurement, and switches between an open position and a closed position according to an instruction from the computer 21 for measurement. FIG. 10 shows an operation timing at which the valve 15-i switches between the open position and the closed position.
In the graph of FIG. 10, the horizontal axis is the primary space 7-i.
And the secondary space 8-i, and the vertical axis indicates the position of the valve 15-i.

That is, the valve 15-i is switched to the closed position when the pressure difference is equal to or greater than the predetermined pressure difference H in the open position. Further, the valve 15-i is switched to the open position when the pressure is equal to or less than the predetermined pressure difference L in the closed position. At this time, the predetermined pressure difference H is larger than the predetermined pressure difference L. By such switching, the cargo tank 3-i, the primary space 7-i and the secondary space 8-i
Can be prevented from being destroyed.

The LNG carrier cargo tank thermal insulation section monitoring system 1 further has piping (not shown). The piping is provided for injecting dry air into the cargo tank 3-i to dry the inside of the cargo tank 3-i.
When the humidity in the cargo tank 3-i exceeds a predetermined humidity by the measuring computer 21, the piping is filled with the cargo tank 3-i by injecting dry air into the cargo tank 3-i.
Dry inside. Such drying is performed in the cargo tank 3-i.
Prevents the corrosion of the inner wall of the membrane.

[0051]

The LNG carrier cargo tank thermal compartment monitoring system according to the present invention is used during repair work on an LNG ship, and can monitor abnormal situations more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an LNG carrier cargo tank thermal insulation section monitoring system according to the present invention.

FIG. 2 is a sectional view showing a cargo tank.

FIG. 3 is a block diagram showing an embodiment of an inspection center.

FIG. 4 is a block diagram showing an embodiment of a computer for measurement.

FIG. 5 is a flowchart showing an operation of a main program.

FIG. 6 is a flowchart illustrating an operation of measuring the atmosphere of the outside air.

FIG. 7 is a flowchart illustrating an operation of measuring pressure.

FIG. 8 is a flowchart illustrating an operation when an abnormal situation occurs.

FIG. 9 is a flowchart illustrating an operation of data processing.

FIG. 10 is a graph showing the timing of the valve operation of the valve.

FIG. 11 is a sectional view showing an embodiment of a known membrane LNG ship.

[Explanation of symbols]

 1 LNG carrier cargo tank heat insulation zone monitoring system 2 LNG carrier 3-1-3-5 Cargo tank 4 Center 5-1-5-5 Temperature / humidity meter 6 Electric wires 7-1-7-5 Primary space 8-1 to 8-5 Secondary space 9 Ballast tank 11-i, 12-i, Air tube 13 Thermometer 14 Electric wire 21 Measurement computer 22 Input / output board 23 Pressure transducer 24 Temperature / humidity meter 25 Modem 26 Telephone 27 Power supply 31 Main program 32 Temperature / humidity measurement program 33 Pressure measurement program 34 Handling program 35 Data processing program

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (8)

[Claims] 1. A first pressure gauge for measuring a primary space pressure which is a pressure of a primary space, a second pressure gauge for measuring a secondary space pressure which is a pressure of a secondary space, and a third pressure gauge for measuring an atmospheric pressure. And a measurement computer that determines whether or not an abnormal situation is present based on the primary space pressure, the secondary space pressure, and the atmospheric pressure.
NG carrier cargo tank thermal compartment monitoring system. 2. The LNG carrier cargo tank heat insulation section monitoring system according to claim 1, wherein the state in which the primary space pressure exceeds the atmospheric pressure is determined to be the abnormal situation. 3. The system according to claim 1, wherein a state in which the secondary space pressure exceeds the primary space pressure is determined as the abnormal state.
NG carrier cargo tank thermal compartment monitoring system. 4. The LNG cargo tank according to claim 1, wherein a state in which the amount of change in the primary space pressure per unit time exceeds a predetermined amount of change is determined to be the abnormal situation. Thermal insulation monitoring system. 5. The LNG cargo tank according to claim 1, wherein a state in which the amount of change in the secondary space pressure per unit time exceeds a predetermined amount of change is determined to be the abnormal situation. Thermal insulation monitoring system. 6. The cargo tank according to claim 1, further comprising: a cargo tank thermometer for measuring a cargo tank temperature, which is a temperature inside the cargo tank, wherein the computer for measuring the temperature change and the pressure. An LNG ship cargo tank heat insulation section monitoring system that recognizes a relationship of change and determines that the cargo tank is abnormal when the cargo tank temperature is equal to or higher than a predetermined temperature. 7. The ballast tank thermometer according to claim 6, further comprising a ballast tank thermometer that measures a ballast tank temperature that is an internal temperature of the ballast tank, wherein the measurement computer is configured to control the primary space pressure, the secondary space pressure, An LNG carrier cargo tank heat insulation section monitoring system for estimating whether a membrane provided between the cargo tank and the primary space has a penetration defect based on atmospheric pressure, the cargo tank temperature, and the ballast tank temperature. 8. The device according to claim 1, further comprising a valve interposed between the primary space and the secondary space, wherein the valve is provided between the secondary space pressure and the primary space. When the difference between the space pressure and the pressure difference is smaller than a predetermined pressure difference and is about to be reversed, the primary space and the secondary space are electrically connected.When the difference is larger than a predetermined pressure difference, the primary space and the secondary space are separated from each other. Close LN
Vessel G cargo tank thermal compartment monitoring system.