Large LNG (Liquefied Natural Gas) storage tank bottom plate welding seam tightness detection equipment

Abstract

The utility model discloses a large-scale LNG storage tank bottom plate welding seam tightness detection device. The device comprises a box-shaped housing. A vacuum box is arranged at the lower end of the shell, a nitrogen detector and a vacuum pump are arranged in the shell, and a nitrogen content display screen and a negative pressure display screen are arranged on the outer wall; the lower end of the vacuum box is provided with an opening corresponding to a to-be-detected weld joint; an air-tight seal is arranged between the periphery of the opening and the bottom plate of the weld; the vacuum pump vacuumizes an airtight space defined by the vacuum box and the bottom plate through the exhaust hose; a nitrogen probe of the nitrogen detector is arranged in the vacuum box and is used for detecting nitrogen in the airtight space; the nitrogen content display screen is used for displaying a result detected by the nitrogen detector; the negative pressure display screen is used for displaying the vacuum degree. According to the utility model, the accuracy of tightness detection of the welding seam of the large LNG storage tank bottom plate is ensured, the efficiency is improved, and the cost is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of LNG storage tank manufacturing, in particular to a large-scale LNG storage tank bottom plate weld tightness detection device. Background Art

[0002] In the prior art, large-scale LNG cryogenic storage tanks are mainly divided into three types: single-capacity tanks, double-capacity tanks, and full-capacity tanks.

[0003] Among them, the full-containment storage tank consists of an inner tank and an outer tank, which together constitute a complete storage tank. The inner tank is a self-supporting steel tank for storing liquid products, while the outer tank is a self-supporting steel or concrete tank with a vault.

[0004] Since the storage temperature of LNG is -163°C, it is necessary to fill the annular space between the outer tank and the inner tank with perlite particles to keep the LNG in the inner tank cold.

[0005] The low-temperature steel inner tank, low-temperature steel outer tank and normal-temperature steel outer tank are designed using the allowable stress method, and the materials of the low-temperature steel inner tank and low-temperature steel outer tank are austenitic stainless steel or 9% Ni steel.

[0006] Currently, single-capacity tanks are mainly composed of a low-temperature steel inner tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling, a normal temperature steel tank top, loose insulation fillers, a normal temperature steel outer tank (cannot contain liquefied natural gas), and a containment dike.

[0007] The double-containment tank consists of a low-temperature steel inner tank, a low-temperature steel outer tank, prestressed concrete, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling (insulation layer), a normal temperature steel tank top, loose insulation fillers, a normal temperature steel outer tank (cannot contain liquefied natural gas), and a top cover (rain shield).

[0008] The full containment tank consists of a low-temperature steel inner tank, a low-temperature steel outer tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling (insulation layer), a normal temperature steel roof, loose insulation filler, a concrete roof, and a prestressed concrete outer tank.

[0009] The membrane tank consists of a low-temperature steel inner tank, a prestressed concrete outer tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling (insulation layer), and an inner insulation layer of the concrete outer tank.

[0010] The existing large-scale LNG storage tanks have many bottom plate welds in a turtle shell shape. The existing technology tank bottom weld tightness test is mainly as follows: Figure 1 The vacuum box experiment shown is roughly as follows:

[0011] First, spray soap liquid on the weld, then cover the vacuum test box on the position where the soap liquid is sprayed, and seal the overlap between the vacuum box and the tank bottom plate with soft sealing materials (polyvinyl chloride mastic, soft mastic, plasticine or other);

[0012] Then use the air compressor to evacuate the inside of the vacuum box, and then observe whether the soap liquid on the weld produces bubbles. If bubbles are produced, it means that there are pores in the weld and the weld needs to be repaired. If no bubbles are produced, it means that the weld at this location is tight.

[0013] After testing one place, the vacuum box is moved until all the welds on the bottom of the tank are tested.

[0014] In the prior art, after the vacuum box is moved, the overlap between the vacuum box and the bottom plate of the large LNG storage tank needs to be re-sealed with soft materials each time, which is labor-intensive and requires two workers to work together.

[0015] Moreover, when there is really a pore at a certain position of the bottom plate weld of a large LNG storage tank, the soapy water applied thereon cannot guarantee 100% generation of bubbles, which makes it impossible to guarantee 100% pass of the airtightness test of the weld position at that position.

[0016] Therefore, how to ensure the accuracy of the tightness detection of the bottom plate weld of large LNG storage tanks, improve efficiency and save investment costs has become a technical problem that technical personnel in this field urgently need to solve. Utility Model Content

[0017] In view of the above-mentioned defects of the prior art, the utility model provides a large-scale LNG storage tank bottom plate weld tightness detection device, the purpose of which is to ensure the accuracy of large-scale LNG storage tank bottom plate weld tightness detection, improve efficiency and save investment costs.

[0018] To achieve the above-mentioned purpose, the utility model discloses a large-scale LNG storage tank bottom plate weld tightness detection device, comprising a box-shaped shell.

[0019] A vacuum box is provided at the lower end of the shell, a nitrogen detector and a vacuum pump are provided inside, and a nitrogen content display screen and a negative pressure display screen are provided on the outer wall;

[0020] The lower end of the vacuum box is provided with an opening corresponding to the position of the weld to be tested;

[0021] An airtight seal is provided between the periphery of the opening and the bottom plate where the weld is located;

[0022] The vacuum pump evacuates the airtight space enclosed by the vacuum box and the bottom plate through a vacuum hose;

[0023] The nitrogen probe of the nitrogen detector is arranged in the vacuum box, and is used to detect the nitrogen in the airtight space;

[0024] The nitrogen content display screen is used to display the results measured by the nitrogen detector;

[0025] The negative pressure display screen is used to display the vacuum degree.

[0026] Preferably, a power switch is provided on the outer wall of the housing;

[0027] The power switch is used to control whether to supply power to the nitrogen detector and the vacuum pump.

[0028] Preferably, a vacuum switch is provided on the outer wall of the housing;

[0029] The vacuum switch is used to control whether the vacuum motor of the vacuum pump is started.

[0030] Preferably, the nitrogen content display screen is connected to the nitrogen detector via a first data line arranged in the housing to obtain data from the nitrogen detector;

[0031] The negative pressure display screen is connected to the electric pressure gauge of the vacuum pump via a second data line arranged in the housing to obtain data of the vacuum pump.

[0032] Preferably, the housing is provided with a weak current switch for controlling low-voltage direct current power supply to the nitrogen content display screen and the negative pressure display screen.

[0033] Preferably, the inner wall of the shell is provided with a support plate;

[0034] The support plate is used to fix the nitrogen detector.

[0035] Preferably, a pair of wheels is provided on one side of the shell near the lower end; and a handrail is provided on the wheels.

[0036] Preferably, the top plate of the vacuum box is made of tempered glass.

[0037] Beneficial effects of the utility model:

[0038] The application of the utility model improves the accuracy of the LNG storage tank bottom plate weld tightness test, shortens the detection cycle, saves costs, and also realizes the mechanized digital integration of large-scale LNG storage tank bottom plate weld tightness detection.

[0039] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram showing the prior art.

[0041] Figure 2 A structural schematic diagram of an embodiment of the utility model is shown. DETAILED DESCRIPTION

[0042] Example

[0043] like Figure 2 As shown, the large-scale LNG storage tank bottom plate weld tightness detection equipment includes a box-shaped shell 7.

[0044] A vacuum box 6 is provided at the lower end of the housing 7, a nitrogen detector 10 and a vacuum pump 18 are provided inside, and a nitrogen content display screen 15 and a negative pressure display screen 16 are provided on the outer wall;

[0045] An opening is provided at the lower end of the vacuum box 6 corresponding to the position of the weld 3 to be inspected;

[0046] An airtight seal 5 is provided between the periphery of the opening and the bottom plate where the weld 3 is located;

[0047] The vacuum pump 18 evacuates the airtight space enclosed by the vacuum box 6 and the bottom plate through the vacuum hose 1;

[0048] The nitrogen probe 2 of the nitrogen detector 10 is arranged in the vacuum box 6 and is used to detect the nitrogen in the airtight space;

[0049] The nitrogen content display screen 15 is used to display the results measured by the nitrogen detector 10;

[0050] The negative pressure display screen 16 is used to display the vacuum degree.

[0051] In some embodiments, a power switch 14 is provided on the outer wall of the housing 7;

[0052] The power switch 14 is used to control whether to supply power to the nitrogen detector 10 and the vacuum pump 18 .

[0053] In some embodiments, the outer wall of the housing 7 is provided with a vacuum switch 13;

[0054] The vacuum switch 13 is used to control whether the vacuum motor 17 of the vacuum pump 18 is started.

[0055] In some embodiments, the nitrogen content display screen 15 is connected to the nitrogen detector 10 via a first data line 9 disposed in the housing 7 to obtain data from the nitrogen detector 10;

[0056] The negative pressure display screen 16 is connected to an electric pressure gauge 20 of the vacuum pump 18 via a second data line 19 disposed in the housing 7 to obtain data of the vacuum pump 18 .

[0057] In some embodiments, the housing 7 is provided with a weak current switch 12 for controlling the low-voltage direct current power supply to the nitrogen content display screen 15 and the negative pressure display screen 16 .

[0058] In some embodiments, the inner wall of the housing 7 is provided with a support plate 11;

[0059] The support plate 11 is used to fix the nitrogen detector 10 .

[0060] In some embodiments, a pair of wheels 4 is provided on one side of the housing 7 near the lower end; and a handrail 8 is provided on the upper side of the wheels 4 .

[0061] In some embodiments, the top plate of the vacuum box 6 is made of tempered glass.

[0062] In practical applications, the top plate of the vacuum box 6 made of tempered glass material can prevent concavity from occurring during vacuuming.

[0063] In practical application, the use process of the utility model is as follows:

[0064] Step 1, move the detection equipment to the position of the weld 3 of the bottom plate;

[0065] Step 2, using wet rubber and plastic to form an airtight seal 5 between the opening of the vacuum box 6 and the bottom plate where the weld 3 is located;

[0066] Step 3, turn on the power supply, start the nitrogen detector 10, the vacuum pump 18, the nitrogen content display screen 15 and the negative pressure display screen 16;

[0067] Step 4, turn on the nitrogen content display screen 15 and the negative pressure display screen 16 to display the readings;

[0068] Step 5: The airtight space enclosed by the vacuum box 6 and the bottom plate is evacuated by the vacuum pump 18 until the negative pressure display screen 16 shows a pressure value below -53 KPa;

[0069] Step 6, observe the reading of the nitrogen content display screen 15; if the reading of the nitrogen content display screen 15 gradually decreases from any value to 0 and does not change, it means that the air tightness at the location of the weld 3 is good; if the reading of the nitrogen content display screen 15 gradually decreases from any value to 0 and then gradually increases, or does not decrease to 0, it means that the air tightness at the location of the weld 3 is unqualified;

[0070] Step 7: After the inspection is completed, move the inspection equipment to the next inspection position, and repeat steps 2 to 6 until the inspection of the bottom plates where all welds 3 are located is completed.

[0071] In step 6, if the air tightness at the location of the weld 3 is unqualified, the corresponding weld 3 needs to be repaired; the repair method is to remove the existing weld 3 by air gouging and then re-weld.

[0072] In actual application, when the reading of the negative pressure display screen 16 is stabilized below -53Kpa, the data of the nitrogen content detection display screen 15 will gradually drop from a certain value to 0, because the nitrogen content before vacuuming accounts for about 78% of the airtight space surrounded by the vacuum box 6 and the bottom plate. As the vacuum pump 18 evacuates the air in the airtight space surrounded by the vacuum box 6 and the bottom plate, the air content inside it drops to 0 and gradually becomes a vacuum state.

[0073] The preferred specific embodiments of the utility model are described in detail above. It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the utility model without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field based on the concept of the utility model through logical analysis, reasoning or limited experiments on the basis of the existing technology should be within the scope of protection determined by the claims.

Claims

1. A large-scale LNG storage tank bottom plate weld tightness detection device, comprising a box-shaped housing (7); characterized in that: A vacuum box (6) is provided at the lower end of the housing (7), a nitrogen detector (10) and a vacuum pump (18) are provided inside the housing, and a nitrogen content display screen (15) and a negative pressure display screen (16) are provided on the outer wall; The lower end of the vacuum box (6) is provided with an opening corresponding to the position of the weld (3) to be inspected; An air seal (5) is provided between the periphery of the opening and the bottom plate where the weld (3) is located; The vacuum pump (18) evacuates the airtight space enclosed by the vacuum box (6) and the bottom plate through the vacuum hose (1); The nitrogen probe (2) of the nitrogen detector (10) is arranged in the vacuum box (6) and is used to detect the nitrogen in the airtight space; The nitrogen content display screen (15) is used to display the results measured by the nitrogen detector (10); The negative pressure display screen (16) is used to display the vacuum degree.

2. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The outer wall of the housing (7) is provided with a power switch (14); The power switch (14) is used to control whether to supply power to the nitrogen detector (10) and the vacuum pump (18).

3. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The outer wall of the housing (7) is provided with a vacuum switch (13); The vacuum switch (13) is used to control whether the vacuum motor (17) of the vacuum pump (18) is started.

4. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The nitrogen content display screen (15) is connected to the nitrogen detector (10) via a first data line (9) arranged in the housing (7) to obtain data from the nitrogen detector (10); The negative pressure display screen (16) is connected to the electric pressure gauge (20) of the vacuum pump (18) via a second data line (19) disposed in the housing (7) to obtain data of the vacuum pump (18).

5. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The housing (7) is provided with a weak current switch (12) for controlling the supply of low-voltage direct current power to the nitrogen content display screen (15) and the negative pressure display screen (16).

6. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The inner wall of the housing (7) is provided with a support plate (11); The support plate (11) is used to fix the nitrogen detector (10).

7. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: A pair of wheels (4) is provided on one side of the housing (7) near the lower end; and a handrail (8) is provided on the wheels (4).

8. The large-scale LNG storage tank bottom plate weld tightness detection equipment according to claim 1 is characterized in that: The top plate of the vacuum box (6) is made of tempered glass.

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