Method for testing pressure sampling hose during vacuumizing of insulating layer of LNG (Liquefied Natural Gas) ship
By using pressure detection components to detect pressure sampling hoses during the vacuuming process of LNG ship insulation layer, the time-consuming and labor-intensive inspection is solved, and fast and effective hose inspection is achieved, and safety hazards are reduced.
Patent Information
- Application Number
- CN202510403751.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-01
- Publication Date
- 2025-07-08
AI Technical Summary
In the prior art, the detection of the pressure sampling hose of the LNG ship insulation layer is time-consuming and labor-intensive, resulting in a long inspection cycle.
During the vacuuming process, by connecting the pressure detection component to the secondary layer sampling valve, detecting the initial pressure data, stopping the air extraction to the preset value, closing the sampling valve, observing the pressure changes, determining whether the hose is qualified, and gradually detecting other hoses to ensure that the pressure of the main and secondary layers is stable before pumping.
The inspection process of pressure sampling hose is simplified, the detection time is reduced, safety risks are reduced, and the detection efficiency is improved.
Smart Images
Figure CN120274970A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of shipbuilding, and particularly to a method for inspecting a pressure sampling hose during vacuum pumping of an insulation layer of an LNG ship. Background Art
[0002] An LNG (Liquefied Natural Gas carrier) ship is a liquefied natural gas ship, and its main function is to transport liquefied natural gas. This kind of ship is specially designed to load natural gas liquefied at extremely low temperatures (about -162 °C) for transoceanic transportation to the demand market. Among them, the insulation layer is one of the core technologies to ensure the safe transportation of LNG at extremely low temperatures. The sealing performance of the insulation layer is directly related to the construction quality of the LNG ship. Once the insulation layer is damaged, major quality and safety hazards will occur.
[0003] Generally, the LNG in the LNG ship is stored in the cargo hold. To avoid combustion or even explosion when the cargo hold leaks into the air, an insulation layer is also provided outside the cargo hold. The insulation layer has two layers. One layer is used to surround the cargo hold and is called the primary insulation layer (i.e., the main layer), and a secondary insulation layer (i.e., the secondary layer) is also provided outside the main layer. There are sealed spaces between the main layer and the cargo hold, and between the main layer and the secondary layer. These sealed spaces are filled with nitrogen. When the cargo hold leaks, the leaked natural gas will not directly contact the air, further improving safety. Therefore, before filling nitrogen, the spaces in the main layer and the secondary layer need to be evacuated to remove the oxygen in the air.
[0004] The main layer and the secondary layer should maintain certain pressures respectively. Generally, the pressure relationship of each sealed space should satisfy: cargo hold pressure > main layer pressure > secondary layer pressure. The set value of the main layer is 0.4 - 0.6 kPa, and the set value of the secondary layer is 0.2 - 0.4 kPa. When the pressure is higher or lower than this pressure range, corresponding exhaust and air supply operations are required. Therefore, pipelines connected to the main layer and the secondary layer respectively are provided on the ship, and the air supply and exhaust are the same pipeline. The pipeline is also used for vacuum pumping of the insulation layer. Correspondingly, sampling pipes and sampling valves connected to the main layer and the secondary layer respectively are also provided on the ship, and a blind plate is installed behind the sampling valve usually. When corresponding operations need to be performed on the insulation layer, the blind plate is opened.
[0005] During the vacuuming process, it is necessary to pump it to a specific air pressure. Generally, the vacuuming target value for the main layer is -75kpa, and the vacuuming target value for the secondary layer is -78kpa. The lower limit of the range of the pressure sensor for loading is generally -3.5kpa, which is far from the actual pressure. In order to prevent the large negative pressure after vacuuming from damaging the sensor, it is necessary to connect a pressure sampling hose to the sampling port, and connect a U-tube mercury meter or an external pressure sensor that meets the range to the pressure sampling hose. The pressure sampling hose connected to the main layer is recorded as the main layer hose, and the pressure sampling hose connected to the secondary layer is recorded as the secondary layer hose. The pressure sampling hose used is generally stored in the warehouse and will only be connected and used when the insulation layer is vacuumed. Whether the hose is damaged due to changes in environmental temperature and humidity or other factors during storage is generally difficult to judge with the naked eye, so these hoses need to be inspected. However, the vacuuming process involves 4 cargo holds, each of which is divided into a main layer and a secondary layer, that is, 8 hoses are required during the vacuuming cycle. In addition, the sampling points used for monitoring are far apart, and the hoses used are generally several dozen meters long. If the eight hoses are tested individually, it will be time-consuming and labor-intensive, affecting the test operation cycle. Summary of the invention
[0006] In view of this, the present invention provides a method for inspecting a pressure sampling hose when the insulation layer of an LNG ship is vacuumed, so as to solve the problem in the prior art that it is time-consuming and labor-intensive to inspect the pressure sampling hose alone, resulting in a long inspection cycle.
[0007] A method for inspecting a pressure sampling hose when vacuuming an insulating layer of an LNG ship comprises the following steps: firstly, connecting one of a main layer hose or a secondary layer hose to a sampling valve of a secondary insulating layer, and connecting a pressure detection component to the hose; opening the secondary layer sampling valve, detecting initial pressure data, then starting a vacuum pump to vacuum the layer, stopping exhaust when the pressure in the secondary layer reaches a first preset value, and closing the secondary layer sampling valve after the pressure stabilizes. If the pressure in the hose does not change, it is proved that the hose is qualified, and if the pressure changes, the hose is unqualified; then removing the hose and connecting another hose to the secondary layer sampling valve, connecting the pressure detection component, opening the secondary layer sampling valve, and closing the secondary layer sampling valve after the pressure stabilizes. If the pressure detected by the pressure detection component does not change, it is proved that the hose is qualified, and if the pressure changes, the hose is unqualified; after the two hoses are inspected and qualified, the main layer hose and the pressure detection component are respectively connected to the main layer, and the secondary layer hose and the pressure detection component are connected to the secondary layer, and the main layer and the secondary layer are exhausted until they reach their target values respectively.
[0008] Furthermore, when the secondary layer is evacuated, the isolation valves of the primary and secondary insulation layers are closed, and the secondary layer is evacuated alone.
[0009] Further, when the two hoses are qualified and air is extracted from the main layer and the secondary layer, open the isolation valve between the main and secondary insulation layers. When the pressure in the main layer reaches the target value, close the isolation valve between the main and secondary insulation layers, and extract air from the secondary layer alone.
[0010] Further, the pressure detection assembly includes a pressure sensor and a mercury manometer.
[0011] Further, when extracting air, first use one vacuum pump. After the air extraction progress is stable, start another vacuum pump to extract air simultaneously.
[0012] Further, the first preset value is -200 mbr.
[0013] The beneficial effect of the method for inspecting the pressure sampling hose during vacuum pumping of the insulation layer of an LNG ship in the present invention is as follows: In the present invention, one of the hoses that needs to be connected to the main layer hose or the secondary layer hose is connected to the secondary layer sampling valve. After connecting the pressure detection assembly, the pressure of the secondary layer can be detected; by detecting the initial pressure data, the current pressure in the secondary layer can be known, and at the same time, it is also a self-check of the pressure detection assembly; then air is extracted. At this time, the pressure in the secondary layer will gradually decrease. When it reaches the first preset value, stop extracting air and perform pressure detection; when the secondary layer sampling valve is closed, the hose is not in communication with the outside, and the pressure in the hose will be maintained at the first preset value. However, if the hose is damaged and leaks air, the pressure in the hose will increase because air will enter the hose. Therefore, it can be known whether the hose is qualified by observing the pressure in the hose; then the other hose can be detected in the same way; after both hoses are qualified, then extract air, and there will be no change in the pressure in the main layer and the secondary layer due to hose leakage, thereby reducing the risk of potential safety hazards, and further solving the problem in the prior art that it is time-consuming and laborious to separately detect the pressure sampling hose, resulting in a long inspection cycle. Description of the Drawings
[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0015] Figure 1 It is the pipeline connection diagram when using the method for inspecting the pressure sampling hose during vacuum pumping of the insulation layer of an LNG ship in the present invention for inspection.
[0016] The meanings of the reference numerals in the figure are as follows: 1, main layer; 2, secondary layer; 31, pressure sensor; 32, mercury manometer; 41, main layer hose; 42, secondary layer hose; 51, main layer sampling valve; 52, secondary layer sampling valve; 61, main layer air extraction pipeline; 62, secondary layer air extraction pipeline. Detailed implementation mode
[0017] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and do not intend to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.
[0018] The terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit this disclosure. The singular forms "a", "the" and "said" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
[0019] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".
[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.
[0021] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "coupling" should be understood in a broad sense. For example, it may be a mechanical connection or an electrical connection, or it may be the communication inside two elements. It may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms may be understood according to specific circumstances.
[0022] In the following description, suffixes such as "module", "component", or "unit" used to denote elements are only for the convenience of explaining the present invention and have no specific meaning in themselves. Therefore, "module" and "component" can be used interchangeably.
[0023] For a better understanding of the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.
[0024] In Embodiment 1 of the inspection method for the pressure sampling hose during the evacuation of the insulation layer of an LNG ship in the present invention (hereinafter referred to as the hose inspection method):
[0025] The hose inspection method in this embodiment is carried out during the evacuation process. Since there is already a process of waiting to inspect the tightness of the insulation layer during the evacuation, by detecting the tightness of the hose at this stage, it is convenient to save inspection time and inspection procedures. The following will be combined with Figure 1 This hose inspection method will be elaborated:
[0026] Specifically, during the detection process, the following steps need to be followed:
[0027] S1. Check the status of the vacuum pump, the main layer evacuation pipeline 61, and the secondary layer evacuation pipeline 62. Check and confirm the status of the valves related to the evacuation of the insulation layer and the marine instrument switches, and complete the preparation work for evacuation;
[0028] S2. Install the secondary layer hose 42 on the secondary layer sampling valve 52, and connect a pressure detection component to this secondary layer hose 42. Specifically, the pressure detection component includes a pressure sensor 31 and a mercury manometer 32. After the installation is completed and confirmed, close the main and secondary insulation layer isolation valves, and record the initial pressure data once. At this time, it is both a detection of the initial atmospheric pressure and a detection of the pressure sensor 31 and the mercury manometer 32. The pressure gauge and the mercury manometer 32 can confirm each other to avoid being unaware of abnormal readings due to instrument damage.
[0029] S3. The duty officer in the cargo control room remotely controls the start of the No. 1 vacuum pump to evacuate the secondary layer 2. Since it is not allowed for the pressure of the secondary layer to be greater than that of the main layer during use, by evacuating the secondary layer 2, it is convenient to make the pressure of the secondary layer 2 always less than that of the main layer.
[0030] S4. The pressure monitoring personnel report the pressure data of each hold's secondary layer to the cargo control room every 5 minutes and record it in writing. After the evacuation progress is stable, start the No. 2 vacuum pump to work simultaneously. The evacuation efficiency of two vacuum pumps is greater than that of a single vacuum pump. At the same time, in order to avoid too rapid pressure changes, therefore, first start one vacuum pump, and then use two simultaneously after the progress is stable. In this way, the evacuation efficiency can be improved as much as possible under a stable state.
[0031] S5. When the pressure of the secondary layer reaches -200 mbar, stop two vacuum pumps. Let it stand for about 10 minutes. Since the space inside the insulation layer is large and there are irregular areas, there is a certain resistance and lag in the gas flow. By letting it stand, it is convenient for the pressure in the secondary layer 2 to be balanced. After that, if there is no leakage, the reading will not change, which is convenient for subsequent observation. Maintaining the pressure within this value is convenient for generating negative pressure for detection on the one hand, and at the same time, the pressure difference between the inside and outside is not too large. In case of leakage, the operator has enough time for maintenance.
[0032] S6. The pressure monitoring personnel close the sampling valve 52 of the secondary layer and observe while it is standing. At this time, the connection between the secondary layer 2 and the secondary layer hose 42 is disconnected, and the space inside the hose becomes an independent part. If there is no leakage in the hose, the pressure should not change. Use a spray bottle filled with soapy water to check the status of the secondary layer hose 42 and the mercury manometer 32. If it is observed that the pressure reading rises and it is checked that there is a leakage in the pressure hose or the U-shaped tube, it proves that the hose is leaking, and it should be replaced with a spare part as soon as possible.
[0033] S7. After checking and confirming that there is no problem with the secondary layer hose 42, close the sampling valve 52 of the secondary layer and temporarily remove the secondary layer hose 42 to facilitate the detection of other hoses.
[0034] S8. Connect the main layer hose 41 to the sampling valve 52 of the secondary layer, open the sampling valve 52 of the secondary layer, and observe the pressure readings of the main layers of each compartment. At this time, the main layer pressure reading should be the same as the secondary layer pressure reading in step S5. Close the sampling valve 52 of the secondary layer, and use a spray bottle filled with soapy water to check the status of the main layer hose 41 and the mercury manometer 32. If it is observed that the pressure reading rises, or it is checked that there is a leakage in the pressure hose or the U-shaped tube, it should be replaced with a spare part as soon as possible. Of course, in other embodiments, the detection order of the main layer hose 41 and the secondary layer hose 42 can also be changed, that is, first detect the main layer hose 41 and then detect the secondary layer hose 42. If both hoses are normal, the secondary layer hose 42 can be directly retained on the sampling valve 52 of the secondary layer for subsequent inspection steps.
[0035] S9. After checking and confirming that there is no problem with the main and secondary layer hoses 42, the duty personnel in the cargo control room should be notified in time to continue the vacuum pumping. At this time, connect the main layer hose 41 to the sampling valve 51 of the main layer, connect the secondary layer hose 42 to the sampling valve 52 of the secondary layer, and install the pressure detection components on their respective hoses in place.
[0036] S10. After remotely starting the No. 1 vacuum pump, first suck the secondary layer 2. After the pressure is relatively stable, open the isolation valve between the main and secondary insulation layers and suck the main layer 1 and the secondary layer 2 at the same time. Not directly sucking the main layer 1 is to avoid the pressure of the main layer 1 dropping lower than the pressure of the secondary layer 2. After the pressure is relatively stable, start the No. 2 vacuum pump, and the two pumps work at the same time.
[0037] S11. When the pressure of the main layer reaches the target value, the air extraction of the main layer 1 ends, and the isolation valves of the main and secondary layers 2 are closed. When the pressure of the secondary layer reaches about the target value, the air extraction of the secondary layer 2 ends, the vacuum pump is stopped and the inlet valve of the vacuum pump is closed.
[0038] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the scope of protection of the present invention.
Claims
1. A method for inspecting a pressure sampling hose during vacuum pumping of an LNG ship insulation layer, characterized in that: First, connect one of the main layer hoses or secondary layer hoses to the secondary layer sampling valve, and connect a pressure detection component to this hose; open the secondary layer sampling valve, detect the initial pressure data, then start the vacuum pump to evacuate the layer. When the pressure in the secondary layer reaches the first preset value, stop pumping air. After the pressure stabilizes, close the secondary layer sampling valve. If the pressure in this hose does not change, it proves that this hose is qualified; if the pressure changes, this hose is unqualified; then remove this hose and connect the other hose to the secondary layer sampling valve, connect the pressure detection component, open the secondary layer sampling valve, and close the secondary layer sampling valve after the pressure stabilizes. If the pressure detected by the pressure detection component does not change, it proves that this hose is qualified; if the pressure changes, this hose is unqualified; after both hoses are inspected and qualified, connect the main layer hose and the pressure detection component to the main layer respectively, and connect the secondary layer hose and the pressure detection component to the secondary layer, and evacuate the main layer and the secondary layer until they reach their target values respectively.
2. The inspection method of the pressure sampling hose during the evacuation of the insulation layer of an LNG ship according to claim 1, wherein: When evacuating the secondary layer, close the main and secondary insulation layer isolation valve and evacuate the secondary layer alone.
3. The inspection method of the pressure sampling hose during the evacuation of the insulation layer of an LNG ship according to claim 2, wherein: When both hoses are inspected and qualified and evacuating the main layer and the secondary layer, open the main and secondary insulation layer isolation valve. When the pressure in the main layer reaches the target value, close the main and secondary insulation layer isolation valve and evacuate the secondary layer alone.
4. The inspection method for the pressure sampling hose during the evacuation of the insulation layer of an LNG ship according to any one of claims 1-3, characterized in that: The pressure detection component includes a pressure sensor and a mercury manometer.
5. The inspection method for the pressure sampling hose during vacuum pumping of the insulation layer of an LNG ship according to any one of claims 1 to 3, characterized in that: When pumping air, first use one vacuum pump, and start another vacuum pump to pump air simultaneously after the pumping progress stabilizes.
6. The inspection method for the pressure sampling hose during the evacuation of the insulation layer of an LNG ship according to any one of claims 1 to 3, characterized in that: The first preset value is -200 mbr.