A ventilation system for empty spaces in a type B LNG fuel tank

Abstract

This invention discloses a ventilation system for an empty space in a Type B LNG fuel tank, comprising a gas leak detector and a pressure sensor. Both the gas leak detector and pressure sensor are located within the empty space formed between the LNG fuel tank and the outer bulkhead. An exhaust duct, connecting the inner and outer sides of the outer bulkhead, runs through and is sealed to the outer bulkhead. An airtight electric butterfly valve, controlling the passage between the empty space and the outside atmosphere, is installed on the exhaust duct. An explosion-proof exhaust fan is installed on the side of the airtight electric butterfly valve connected to the outside atmosphere. The explosion-proof exhaust fan, airtight electric butterfly valve, gas leak detector, and pressure sensor are all electrically connected to a PLC control module. The ventilation system provided by this invention has a compact structure, is easy to install, and includes a built-in PLC control module. Based on gas detection and pressure sensing in the empty space, the explosion-proof exhaust fan and airtight electric butterfly valve can be automatically adjusted to meet the ventilation requirements of the empty space under different conditions.

Description

Technical Field

[0001] This invention relates to a ventilation system for empty spaces in a Type B LNG fuel tank (Type B tank is a structural type of fuel tank, mainly including three types: A / B / C; LNG fuel tank refers to a tank that carries LNG fuel, and LNG means liquefied natural gas in Chinese), belonging to the field of shipbuilding. Background Technology

[0002] With governments and the International Maritime Organization focusing on CO2 and NOx... X and SO X With increasingly stringent emission requirements, more and more ships are beginning to use more economical and environmentally friendly gaseous fuels. In dual-fuel ships, the space between the insulation structure and the outer bulkhead of the Type B LNG tank is an empty area. This empty space is equipped with a maintenance platform for routine personnel access and maintenance. During navigation, the empty space is filled with inert gas to remove air and moisture, maintaining a dry and pressurized environment. In the event of a leak in the LNG fuel tank or an accident, hazardous gases may be present in the empty space. If the concentration of these hazardous gases reaches a certain level, maintenance personnel attempting to remove them could endanger their health or even lives. In such cases, emergency ventilation is necessary to remove the hazardous gases as quickly as possible.

[0003] Currently, patent CN113443116A discloses a ventilation method for liquefied gas transport ships and their empty cargo holds, which provides ventilation for the empty cargo holds.

[0004] The document "Zhou Zhixian, Yang Lingkang, Wu Hairong. Discussion on the Design of LNG Dual-Fuel Powered Ships. Ship and Ocean Engineering, 2014(4)" published in the China Academic Literature Network Publishing Database focuses on the design points of dual-fuel engine ships, analyzing key technologies in dual-fuel ship design such as the layout of LNG fuel tanks, the selection of storage tanks, the method of fuel refueling, the design of the double-walled pipe ventilation system, and the exhaust system with special requirements. The paper mentions the ventilation system for the engine room and the double-walled pipe.

[0005] The document "Zhao Meng, Guo Dongxue. Analysis of Key Points in the Classification of Hazardous Areas of Dual-Fuel Ro-Ro Passenger Ships. Basic Science and Technology, 2020(11)" published in the China Academic Literature Network Publishing Database focuses on the classification of hazardous areas for dual-fuel ships. It analyzes the definition of hazardous areas, the classification of hazardous areas in fuel tank areas, the classification of hazardous areas in ventilation inlets and outlets, and the classification of hazardous areas in C-type tanks. The paper focuses on the classification of hazardous areas. Regarding ventilation, it only mentions that "LNG-related hazardous areas should be continuously ventilated, and the inlet and outlet of ventilation ducts should be high enough to avoid the installation of shut-off devices required by the Load Line Convention." Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to design a ventilation system suitable for the empty space of a Type B LNG fuel tank under normal working conditions, accident conditions, and personnel maintenance conditions, so as to meet the ventilation requirements under various conditions and ensure the environmental and personnel safety of the empty space.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is to provide a ventilation system for an empty space in a type B LNG fuel tank. The system is characterized by including a gas leak detector and a pressure sensor, both of which are located within the empty space formed between the LNG fuel tank and the outer bulkhead. An exhaust duct is permeated and sealed to the outer bulkhead, connecting the inner and outer sides of the outer bulkhead. An airtight electric butterfly valve is installed on the exhaust duct to open and close the passage between the empty space and the outside atmosphere. An explosion-proof exhaust fan is installed on the side of the airtight electric butterfly valve connected to the outside atmosphere. The explosion-proof exhaust fan, the airtight electric butterfly valve, the gas leak detector, and the pressure sensor are all electrically connected to a PLC control module. The gas leak detector and pressure sensor feed back signals to the PLC control module in real time. The PLC control module determines whether to open or close the airtight electric butterfly valve and the explosion-proof exhaust fan based on the signals fed back by the gas leak detector and pressure sensor.

[0008] Preferably, when the gas leak detector detects that the concentration of the gas to be detected exceeds a set value, an alarm is triggered, and the airtight electric butterfly valve and explosion-proof exhaust fan are activated via the PLC control module; when the pressure measured by the pressure sensor is lower than a set value, an alarm is triggered, and the airtight electric butterfly valve and explosion-proof exhaust fan are activated via the PLC control module; when the pressure measured by the pressure sensor is higher than another set value, an alarm is triggered, and the airtight electric butterfly valve and explosion-proof exhaust fan are activated via the PLC control module; when the signals fed back by the gas leak detector and the pressure sensor are both within the normal set values, the airtight electric butterfly valve and explosion-proof exhaust fan are shut down via the PLC control module.

[0009] Preferably, the exhaust duct includes at least one airtight exhaust duct, one end of each airtight exhaust duct is located in an empty space, the other end of each airtight exhaust duct passes through the outer bulkhead and is sealed to the outer bulkhead, and the discharge end of each airtight exhaust duct is provided with an airtight electric disc valve and an explosion-proof exhaust fan for exhausting air from the empty space.

[0010] Preferably, the exhaust duct further includes multiple exhaust grilles, with multiple exhaust grilles evenly distributed on each airtight exhaust duct; each airtight exhaust duct is connected to an empty space through multiple exhaust grilles.

[0011] Preferably, the airtight electric butterfly valve and the explosion-proof exhaust fan are both located on the outside of the outer bulkhead.

[0012] Preferably, the airtight electric butterfly valve is interlocked with the explosion-proof exhaust fan.

[0013] Preferably, the airtight electric butterfly valve is in an airtight normally closed state, and is controlled to open or close by a PLC control module according to the signals from the gas leak detector and pressure sensor. When it is open, it discharges the air in the empty space to the outside atmosphere. When it is closed, it ensures the airtight state of the empty space and can withstand the charging pressure of inert gas in the airtight state.

[0014] Preferably, a manhole cover is provided on one side of the outer bulkhead; the manhole cover serves as a passage for personnel to enter the empty space for maintenance and also as a ventilation inlet.

[0015] Preferably, the outlet end of the explosion-proof exhaust fan is provided with a ventilation duct.

[0016] Preferably, the explosion-proof exhaust fan, airtight electric butterfly valve, airtight exhaust pipe, exhaust grille, gas leak detector, and pressure sensor are all explosion-proof, spark-free, and low-temperature resistant structures.

[0017] The empty space of the Type B LNG fuel tank operates at a low temperature under normal conditions and is filled with inert gas, requiring a certain degree of pressure resistance and airtightness. In an emergency, it needs emergency ventilation to reduce the concentration of hazardous gases within the space. During maintenance, personnel need to enter, necessitating the removal of inert gases to provide a safe and comfortable environment. Therefore, the ventilation system design of this invention must consider the requirements of each state: ensuring good pressure resistance and airtightness under normal operating conditions, rapidly and effectively removing hazardous gases in an emergency, and rapidly and effectively removing inert gases during maintenance to ensure environmental and personnel safety.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1) The ventilation system of this invention consists of a ventilation duct, an explosion-proof exhaust fan, an airtight electric butterfly valve, an airtight duct, an exhaust grille, a gas leak detector, a pressure sensor, a PLC control module, and a manhole cover. Pipeline connection and installation are convenient. It can automatically control the working state of the ventilation system according to changes in gas concentration and pressure in vacant spaces, meeting the ventilation requirements of vacant spaces under different conditions and ensuring the environmental and personnel safety of vacant spaces.

[0020] 2) The entire ventilation system of the present invention is controlled by PLC, automatically adjusted, and easy to operate. It can be operated according to the different status requirements of the empty space.

[0021] 3) The ventilation system provided by this invention is an independent system, suitable for the structure of a type B LNG fuel tank with a small empty space. The ventilation pipeline is designed to be airtight, which can ensure that the gas does not leak under the pressure inside the tank when the empty space is filled with inert gas.

[0022] The ventilation system provided by this invention has a compact structure and is easy to install. It also comes with a PLC control module, which can automatically adjust the explosion-proof exhaust fan and airtight electric butterfly valve according to the gas detection and pressure sensing of the vacant space, so as to meet the ventilation requirements of the vacant space under different conditions and ensure the environmental and personnel safety of the vacant space. Attached Figure Description

[0023] Figure 1 A schematic diagram of the ventilation system for an empty space in a type B LNG fuel tank;

[0024] Figure 2 This is a schematic diagram of the connection of an airtight exhaust duct. Detailed Implementation

[0025] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0026] This invention provides a ventilation system for empty spaces in a Type B LNG fuel tank, such as... Figure 1 As shown, it includes a ventilation duct 1, an explosion-proof exhaust fan 2, an airtight electric butterfly valve 3, an airtight exhaust pipe 4, an exhaust grille 5, a gas leak detector 6, a pressure sensor 7, a manhole cover 8, and a PLC control module 9. The ventilation duct 1 is located at the outlet of the explosion-proof exhaust fan 2, providing a passage for the exhaust of the explosion-proof exhaust fan 2. The gas leak detector 6 and the pressure sensor 7 are both located in the empty space 12 formed between the LNG fuel tank 10 and the outer bulkhead 11. An exhaust pipe is passed through and sealed to the outer bulkhead 11, connecting the inside and outside of the outer bulkhead 11. The exhaust pipe is equipped with a switch. An airtight electric butterfly valve 3 provides a passage between the storage area 12 and the outside atmosphere. An explosion-proof exhaust fan 2 is installed on the side of the airtight electric butterfly valve 3 that connects to the outside atmosphere. The airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 are interlocked. The airtight electric butterfly valve 3, the gas leak detector 6, and the pressure sensor 7 are electrically connected to the PLC control module 9. The gas leak detector 6 and the pressure sensor 7 feed back signals to the PLC control module 9 in real time. The PLC control module 9 determines whether to open or close the airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 based on the signals fed back by the gas leak detector 6 and the pressure sensor 7.

[0027] The exhaust duct includes an airtight exhaust pipe 4 and an exhaust grille 5 at the end, used for exhaust. The exhaust medium is a hazardous gas or an inert gas. In this embodiment, one end of the airtight exhaust pipe 4 is located in the empty space 12, and the other end of the airtight exhaust pipe 4 passes through the outer bulkhead 11 and is sealed to the outer bulkhead 11. The airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 are both located on the outside of the outer bulkhead 11. Multiple exhaust grilles 5 are evenly distributed on the airtight exhaust pipe 4; the airtight exhaust pipe 4 is connected to the empty space 12 through the multiple exhaust grilles 5.

[0028] An airtight electric disc valve 3 is installed at the discharge end of the airtight exhaust duct 4 to ensure the airtightness of the vacant space 12 and is interlocked with the explosion-proof exhaust fan 2. An explosion-proof exhaust fan 2 is installed at the discharge end of the airtight exhaust duct 4 to exhaust air from the vacant space 12.

[0029] The explosion-proof exhaust fan 2 is interlocked with the airtight electric butterfly valve 3. It starts or stops according to the opening or closing state of the airtight electric butterfly valve 3. When it starts, it exhausts the gas in the empty space 12 to the outside atmosphere.

[0030] The airtight electric butterfly valve 3 is in an airtight and normally closed state, interlocked with the explosion-proof exhaust fan 2, and controlled by the PLC control module 9 according to the signals of the gas leak detector 6 and the pressure sensor 7. When it is open, it exhausts the air in the empty space 12 to the outside atmosphere. When it is closed, it ensures the airtight state of the empty space 12 and can withstand the charging pressure of inert gas in the airtight state.

[0031] Airtight exhaust duct 4: Used to exhaust air from empty space 12, ensuring airtightness under a certain cabin pressure;

[0032] Exhaust grille 5: Exhaust terminal equipment;

[0033] Gas leak detector 6: Used to detect the concentration of hazardous gas in the empty space 12 (gas leak detector 6 is specifically a gas concentration sensor, the hazardous gas is mainly methane, the main component of liquefied natural gas), and feeds the signal back to PLC control module 9. When the concentration exceeds the set value, an alarm is triggered (in this embodiment, an audible and visual alarm can be triggered by outputting an alarm signal) and the airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 are turned on through PLC control module 9.

[0034] Pressure sensor 7: Used to provide feedback on the pressure of the empty space 12. When the pressure is lower than a set value, it sends a signal to the PLC control module 9, triggering an alarm and opening the airtight electric butterfly valve 3 and starting the explosion-proof exhaust fan 2 through the PLC control module 9. When the pressure is higher than another set value, it sends a signal to the PLC control module 9, triggering an alarm (in this embodiment, an audible and visual alarm can be triggered by outputting an alarm signal) and opening the airtight electric butterfly valve 3 and starting the explosion-proof exhaust fan 2 through the PLC control module 9.

[0035] Manhole cover 8: This serves as a personnel access passage and also as a ventilation inlet. When manhole cover 8 is opened, the empty space 12 is in a depressurized state. The pressure sensor 7 is activated, triggering an alarm. The PLC control module 9 then opens the airtight electric butterfly valve 3 and starts the explosion-proof exhaust fan 2 to expel the inert gas from the empty space 12 before personnel enter, ensuring personnel safety.

[0036] PLC control module 9: Based on the signal fed back by pressure sensor 7, determine the state and accordingly open / close airtight electric butterfly valve 3 and open / stop explosion-proof exhaust fan 2.

[0037] When the signal fed back by pressure sensor 7 is within the normal set value or range (some pressure sensors can set a pressure range, while others can only set a pressure value), it indicates that the pressure inside the premises is stable and in normal working condition. At this time, the ventilation system is in an airtight closed state. When the pressure of pressure sensor 7 is higher than the set value and gas leak detector 6 alarms, there is a possibility of gas leakage in LNG fuel tank 10, which is an accident state. The ventilation system is turned on for emergency ventilation. When personnel enter, manhole cover 8 is opened, and the pressure inside the premises is lost. At this time, the pressure of pressure sensor 7 is lower than the set value, and the ventilation system is turned on for ventilation.

[0038] Explosion-proof exhaust fan 2, airtight electric butterfly valve 3, airtight exhaust pipe 4, exhaust grille 5, gas leak detector 6, pressure sensor 7, all must be explosion-proof and non-sparking, and must be resistant to low temperature.

[0039] The connection point of the airtight exhaust duct 4 (this connection point connects the outer bulkhead and the inner exhaust duct; airtightness is required here. The exhaust duct inside the cabin does not need to be airtight; the main requirement is that it passes through the external airtight bulkhead and must ensure airtight integrity) uses a silicone resin mixture and is wrapped with rubber tape. Figure 2 As shown.

[0040] The working principle of this invention is as follows:

[0041] When the empty space 12 is in normal operating condition, it is under positive pressure with inert gas filling, and the ventilation system is kept closed and airtight. In case of an accident, there is a leak of LNG dangerous gas in the empty space 12. At this time, the ventilation system is opened to quickly discharge the leaked dangerous gas. When the empty space 12 is in maintenance condition, personnel need to open the manhole cover 8 to enter. At this time, it is in a depressurized state. The ventilation system is opened to discharge the inert gas in the empty space 12. Through air exchange, the gas in the compartment is quickly restored to the same level as the outside atmosphere, so that personnel can enter safely.

[0042] When the PLC control module 9 opens the airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 for a period of time, and the signals fed back by the gas leak detector 6 and the pressure sensor 7 are all within the normal set values, the PLC control module 9 will automatically control the airtight electric butterfly valve 3 and the explosion-proof exhaust fan 2 to close.

[0043] The ventilation system of the present invention is applicable to the normal working state, accident state, and personnel maintenance state of the empty space in the Type B LNG fuel tank, and can meet the ventilation requirements under various conditions.

[0044] The ventilation system of this invention can ensure the complete airtightness of the empty compartment 12 of the Type B LNG fuel tank 10 under a certain pressure after being filled with inert gas during normal operation. When the LNG fuel tank 10 leaks and is in an accident state, the gas leak detector 6 and pressure sensor 7 can feed back signals to the PLC control module 9, automatically opening the airtight electric butterfly valve 3 and starting the explosion-proof exhaust fan 2 for effective ventilation, quickly expelling hazardous gases, reducing the concentration of hazardous gases in the empty compartment 12, and ensuring the environmental safety requirements of the empty compartment 12 of the LNG fuel tank 10. In the personnel maintenance state, the manhole cover 8 is opened, and the empty compartment 12 is depressurized. The pressure sensor 7 feeds back signals to the PLC control module 9, automatically opening the airtight electric butterfly valve 3 and starting the explosion-proof exhaust fan 2 for effective ventilation, quickly expelling the inert gas in the compartment, providing safe and effective ventilation before personnel enter, and providing a good and safe environment. The switching between various states should be automatically controlled.

Claims

1. A ventilation system for a Type B LNG fuel tank ullage space, characterized in that, The application relates to a gas leakage detection device for an LNG fuel tank, which comprises a gas leakage detector (6) and a pressure sensor (7), wherein the gas leakage detector (6) and the pressure sensor (7) are arranged in a space (12) formed between an LNG fuel tank (10) and an outer tank wall (11), a ventilation pipeline is arranged through and sealingly connected to the outer tank wall (11) and communicates between the inside and outside of the outer tank wall (11), a gas-tight electric butterfly valve (3) is arranged on the ventilation pipeline and is used for opening or closing the passage between the space (12) and the outside atmosphere, an explosion-proof exhaust fan (2) is arranged on the side of the gas-tight electric butterfly valve (3) connected with the outside atmosphere, and the explosion-proof exhaust fan (2), the gas-tight electric butterfly valve (3), the gas leakage detector (6) and the pressure sensor (7) are electrically connected with a PLC control module (9); the gas leakage detector (6) and the pressure sensor (7) feed signals to the PLC control module (9) in real time, and the PLC control module (9) judges whether to open or close the gas-tight electric butterfly valve (3) and the explosion-proof exhaust fan (2) according to the signals fed by the gas leakage detector (6) and the pressure sensor (7). When the signal fed by the pressure sensor (7) is within the normal set value or range, the pressure in the space is stable, and the working state is normal, and at this moment, the ventilation system is in a closed and gas-tight state; the space (12) is in a positive pressure state of inert gas filling when the normal working state of the ship is reached, and the ventilation system is kept closed and gas-tight; when the pressure of the pressure sensor (7) is higher than the set value and the gas leakage detector (6) alarms, the LNG fuel tank (10) may have gas leakage, and the state is an accident state; according to the signals fed by the gas leakage detector (6) and the pressure sensor (7) to the PLC control module (9), the gas-tight electric butterfly valve (3) is automatically opened, and the explosion-proof exhaust fan (2) is started to effectively ventilate, so that the dangerous gas is rapidly discharged, the concentration of the dangerous gas in the space (12) is reduced, and the environmental safety requirement of the space (12) of the LNG fuel tank (10) is ensured. When the space (12) is in a maintenance state, a manhole cover (8) is opened for a person to enter, at this moment, the pressure is lower than the set value, the signal fed by the pressure sensor (7) to the PLC control module (9) is used for automatically opening the gas-tight electric butterfly valve (3) and starting the explosion-proof exhaust fan (2) to effectively ventilate, so that the inert gas in the space (12) is rapidly discharged, the gas in the tank is rapidly recovered to the outside atmosphere through air exchange, and the person can safely enter.

2. A ventilation system for a Type B LNG fuel tank ullage space as claimed in claim 1, characterised in that, When the gas leakage detector (6) detects that the concentration of the gas to be detected exceeds the set value, an alarm is given and the airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are opened by the PLC control module (9); when the pressure measured by the pressure sensor (7) is lower than a set value, an alarm is given and the airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are opened by the PLC control module (9); when the pressure measured by the pressure sensor (7) is higher than another set value, an alarm is given and the airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are opened by the PLC control module (9); when the signals fed back by the gas leakage detector (6) and the pressure sensor (7) are both within the normal set values, the airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are closed by the PLC control module (9).

3. A ventilation system for a Type B LNG fuel tank ullage space as defined in claim 1, wherein The exhaust pipeline comprises at least one airtight exhaust pipe (4), each airtight exhaust pipe (4) being arranged in the air-remaining space (12) at one end, each airtight exhaust pipe (4) penetrating the outer bulkhead (11) and being sealingly connected to the outer bulkhead (11) at the other end, and each airtight exhaust pipe (4) being provided with an airtight electric butterfly valve (3) and an explosion-proof exhaust fan (2) at the exhaust end for exhausting air from the air-remaining space (12).

4. A ventilation system for a Type B LNG fuel tank ullage space as claimed in claim 3, characterised in that, The exhaust pipeline further comprises a plurality of exhaust grilles (5), and each airtight exhaust pipe (4) is provided with a plurality of exhaust grilles (5) arranged thereon; each airtight exhaust pipe (4) is connected to the air-remaining space (12) through the plurality of exhaust grilles (5).

5. A ventilation system for a Type B LNG fuel tank ullage space as claimed in claim 1 or 3, wherein, The airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are arranged outside the outer bulkhead (11).

6. A ventilation system for a Type B LNG fuel tank containment space as defined in claim 1, wherein, The airtight electric butterfly valve (3) and the explosion-proof exhaust fan (2) are interlocked.

7. A ventilation system for a Type B LNG fuel tank ullage space as defined in claim 1, wherein The airtight electric butterfly valve (3) is in an airtight closed state and is opened or closed by the PLC control module (9) according to the signals of the gas leakage detector (6) and the pressure sensor (7); when opened, the airtight electric butterfly valve (3) exhausts air from the air-remaining space (12) to the outside atmosphere; when closed, the airtight electric butterfly valve (3) ensures the airtight state of the air-remaining space (12) and can withstand the filling pressure of the inert gas in the airtight state.

8. A ventilation system for a Type B LNG fuel tank containment space as defined in claim 1, wherein, One side of the outer bulkhead (11) is provided with a manhole cover (8); the manhole cover (8) is a passage for personnel to enter the air-remaining space (12) for maintenance and is also used as an air inlet.

9. A ventilation system for a Type B LNG fuel tank containment space as defined in claim 1, wherein, The air outlet end of the explosion-proof exhaust fan (2) is provided with a ventilation duct (1).

10. A ventilation system for a Type B LNG fuel tank containment space as defined in claim 1, wherein, The explosion-proof exhaust fan (2), the airtight electric butterfly valve (3), the airtight exhaust pipe (4), the exhaust grille (5), the gas leakage detector (6), and the pressure sensor (7) are all explosion-proof and spark-free and can withstand low temperatures.

Images