A method for rapid discharge of sewage from a membrane type cargo containment system

Abstract

A method for rapid sewage discharge of a membrane-type cargo containment system, wherein a grille is provided under the insulating plate at the corners of the bottom of the cargo hold, and a sewage discharge channel is provided under the grille. When any deck in the hold leaks, the water can quickly penetrate into the discharge channel through the grille after flowing along the bulkhead to the bottom. The sewage collected in the discharge channel enters the liquid collecting well through the sewage pipe, and is quickly discharged through the sewage pump suction pipeline, which not only avoids the problem of water accumulation on the bottom of the cargo hold, but also speeds up the drainage rate in the hold. The secondary nitrogen main pipe connected to the nitrogen generator is connected to the discharge channel and is connected to the annular secondary nitrogen branch pipe in the discharge channel. The secondary nitrogen branch pipe has multiple openings. When nitrogen is introduced into the pipe, the residual sewage can be purged in all directions in the discharge channel. Since the cabin is under positive pressure, the sewage in the discharge channel is accelerated to flow into the liquid collecting well. The present invention not only avoids the problem of water accumulation on the bottom of the cargo hold, but also speeds up the drainage rate in the hold.

Description

Technical Field

[0001] The invention belongs to the field of design and construction of a MARKⅢ membrane type liquid cargo containment system for marine vessels, and in particular relates to a method for rapid sewage discharge of a membrane type cargo containment system. Background Art

[0002] The MARKⅢ membrane liquid cargo containment system is mainly designed by the French GTT company. It is a system designed for storing and transporting liquefied natural gas and is widely used in liquefied natural gas carriers. Its structure can be roughly divided into a main barrier layer made of stainless steel corrugated plates, a secondary barrier layer to prevent liquid cargo leakage, a main insulation layer and a secondary insulation layer composed of enhanced polyurethane foam. The main and secondary layer structures are bonded to the bottom of the cargo hold by epoxy resin.

[0003] In order to ensure the safety of the ship and its liquid cargo, after the ship is in operation, it is necessary to continuously inject nitrogen into the primary space formed by the primary barrier layer and the secondary barrier layer, and the secondary space formed by the secondary barrier layer and the inner bottom of the hull, so as to timely purge the natural gas that may leak in the primary and secondary spaces and maintain the positive pressure from the outside to the inside of the primary and secondary spaces. In addition, considering that the hull of the hull may crack and break due to fatigue, resulting in water leakage or forming condensed water in the isolated space, one or two drainage holes are set at the bottom of the stern of each cargo hold, and continuous resin strips or distance-keeping flat steel are set on the bottom of the cargo hold to block and guide the sewage to flow to the drainage holes.

[0004] The insulation layer of the film-type cargo containment system is divided into plane area insulation board, dihedral area insulation board and trihedral insulation board according to the different locations. As the name implies, each insulation board is located in the plane area of ​​each deck, the intersection area of ​​two decks and the intersection area of ​​three decks. There is a circle of dihedral insulation boards bonded around the bottom of the liquid cargo tank, such as Figure 1 As shown, the continuous resin strip or the distance-keeping flat steel is arranged between the bottom dihedral corner insulation plate and the plane boundary insulation plate, forming a rectangular ring structure around the bottom of the cargo hold. A liquid collecting well is arranged below the inner bottom of the isolation void compartment, and the drainage hole is connected to the liquid collecting well through a sewage pipe, and the sewage in the liquid collecting well is then discharged by a vacuum pump. The liquid collecting well is also connected to the nitrogen pipeline from the isolation void compartment, and the nitrogen purged from the secondary space enters the secondary insulation space in the reverse direction along the sewage pipe mentioned above.

[0005] Although the current design can achieve the purpose of transporting nitrogen to the secondary insulation space and discharging sewage, when the cracks in the inner shell of the cargo hold expand and cause the holes to enlarge, a large flow of sewage will flow into the secondary space, and after flowing through the gaps between the resin strips at the bottom of the insulation board, it will fill the drainage pipe, and the secondary nitrogen cannot be replenished into the secondary insulation space; when there is leakage or the amount of condensed water formed in the secondary space is small, the nitrogen in the drainage pipe is in the opposite direction of the water flow, and it cannot achieve the purpose of quickly blowing the sewage out of the drainage hole.

[0006] Since the secondary layer is seamlessly fitted to the hull, there is no gap between the secondary insulation board and the hull, and between the secondary insulation board and the secondary screen. Therefore, it is impossible to set a nitrogen pipeline from the top of the cargo tank downward inside the secondary insulation space, and it is impossible to extend the pipeline from the top of the cargo tank downward to fill the secondary insulation space with nitrogen. Nitrogen can only be filled from the bottom of the cargo tank, and the pressure difference of the nitrogen outlet cannot be used to purge the sewage on the bottom of the cargo tank. However, no matter where the nitrogen pipe is connected to the bottom of the cargo tank after coming out of the liquid collection well, and whether the nitrogen pipe and the sewage discharge pipe use the same pipeline, as long as the nitrogen is directly filled from the bottom of the cargo tank, it will encounter the problem of conflict with the sewage, because the sewage will accumulate on the bottom of the cargo tank, and then it will meet with the nitrogen, resulting in the sewage cannot be discharged in time and the nitrogen cannot be filled.

[0007] If sewage cannot be discharged in time, water will remain in the secondary space and ice will form. The expansion force of the ice layer will cause the insulation layer to deform and crack, thus affecting the safety of the entire cargo containment system. At the same time, the ice layer will also destroy the thermal insulation performance of the insulation layer, making the temperature inside the membrane cabin more susceptible to the outside temperature. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a method for rapid discharge of sewage from a film-type cargo containment system, aiming to increase the drainage rate of sewage from the film-type containment system and improve the safety of the cargo containment system. The technical solution adopted is:

[0009] A method for rapid sewage discharge of a membrane-type cargo containment system, wherein an isolation void tank is arranged at one end of a liquid cargo tank, a sunken discharge channel is arranged at the bottom of the interior of the liquid cargo tank and along the circumference of the liquid cargo tank, the discharge channel is connected with a secondary space, a grille is laid above the discharge channel, the grille is located in a non-adhesive area under a dihedral insulating plate, a circle of annular stop iron matching the shape of the grille is welded below an inner bottom plate of the liquid cargo tank in an area where the grille is installed, the grille is aligned and welded and fixed, and after fixation, the top surface of the grille and the inner bottom plate of the liquid cargo tank are located on the same horizontal plane.

[0010] A liquid collecting well is arranged at the bottom of the isolation void compartment, and the liquid collecting well is adjacent to the discharge channel. A sewage outlet is arranged at the bottom of the discharge channel in the stern direction, and the sewage outlet is connected to a sewage pipe, which is connected to the liquid collecting well, and the sewage pump suction pipeline extends into the liquid collecting well.

[0011] A secondary nitrogen main pipe is provided in the isolation cabin, and secondary nitrogen branch pipes are provided inside the discharge channel and along the circumference of the discharge channel. The secondary nitrogen main pipe is connected to the discharge channel from the liquid collecting well and is connected to the secondary nitrogen branch pipe. A plurality of exhaust holes are provided on the secondary nitrogen branch pipe.

[0012] In order to avoid the problem of conflict between nitrogen and sewage, the present invention sets a discharge channel on the bottom of the cargo hold, and sinks the discharge channel and the secondary nitrogen branch pipe, so that the sewage discharge pipeline is separated from the nitrogen filling pipeline, and the nitrogen enters through the secondary nitrogen branch pipe, and the sewage is discharged through the discharge channel and the sewage pipe. The discharge channel and the secondary nitrogen branch pipe are both located below the bottom of the liquid cargo tank, and the horizontal heights of the discharge channel, the secondary nitrogen branch pipe and the bottom of the liquid cargo tank are separated to avoid sewage accumulation on the bottom of the liquid cargo tank, and further avoid nitrogen from meeting the accumulated sewage when filling the liquid cargo tank. This solves the problem that the sewage and nitrogen conflict at the bottom of the liquid cargo tank, resulting in sewage not being discharged and nitrogen not being able to enter.

[0013] The inner surface of the liquid cargo tank is coated with resin strips. For the insulating panels in the flat area, only the upper and lower inclined surfaces are longitudinally coated with resin strips, and the other decks are transversely coated with resin strips; for the insulating panels in the dihedral angle area, only the dihedral angle insulating panels where the upper and lower inclined surfaces intersect with the front and rear decks, and the dihedral angle insulating panels where the left and right decks intersect with the front and rear decks are longitudinally coated with resin strips, and the other dihedral angle insulating panels are transversely coated with resin strips.

[0014] The exhaust holes on the secondary nitrogen branch pipe first purge the discharge channel, so that the sewage in the discharge channel can quickly flow into the sewage outlet, and then continue to move upward, establish positive pressure in the secondary insulation space, and increase the speed of the bottom sewage flowing to the discharge channel. The nitrogen circulation cooperates with the resin strips with different directions to accelerate the discharge of sewage on the surface of the liquid cargo tank.

[0015] In the above-mentioned method for rapid sewage discharge of a film-type cargo containment system, further, the grille length W is less than the distance W1 between the two pads of the dihedral insulating plate, satisfying W1=W+60~80 mm.

[0016] The above-mentioned method for rapid sewage discharge of a membrane-type cargo containment system, further, has the grille having the same thickness and material as the bottom plate of the liquid cargo tank.

[0017] The above-mentioned method for rapid sewage discharge of a membrane type cargo containment system, further, the secondary nitrogen branch pipe is fixed in the discharge channel through a nitrogen branch pipe bracket under the bottom of the liquid cargo tank.

[0018] The above-mentioned method for rapid sewage discharge of a membrane-type cargo containment system further comprises a water inlet monitoring device provided in the discharge channel, and the water inlet monitoring device is connected to a drainage pump.

[0019] In the above-mentioned method for rapid sewage discharge of a membrane-type cargo containment system, further, the generator is connected to the nitrogen main pipe through a valve group.

[0020] In the above-mentioned method for rapid sewage discharge of a film-type cargo containment system, further, the distance H between the edge of the grille and the center point of the nearest resin strip is 15 to 40 mm.

[0021] In order to speed up the discharge of sewage in the secondary space and prevent water accumulation on the bottom of the liquid cargo tank, the present invention is provided with a grid under the insulating plate at the corners of the bottom of the liquid cargo tank, and a sewage discharge channel is provided under the grid. When any deck in the tank leaks, the water can quickly penetrate into the discharge channel through the grid after flowing along the bulkhead to the bottom. The sewage collected in the discharge channel enters the liquid collecting well through the sewage pipe, and is quickly discharged through the sewage pump suction pipeline connected to the sewage pump, which not only avoids the problem of water accumulation on the bottom of the cargo tank, but also speeds up the drainage rate in the tank.

[0022] In addition, while solving the problem of rapid drainage in the cabin, it is also necessary to speed up the discharge speed of residual sewage in the discharge channel. Incompletely drained water will also cause ice to form. Therefore, the secondary nitrogen main pipe connected to the nitrogen generator is connected to the discharge channel and connected to the annular secondary nitrogen branch pipe in the discharge channel. There are multiple openings on the secondary nitrogen branch pipe. When nitrogen is introduced into the pipe, positive pressure is formed in the secondary space and the discharge channel. Under this pressure, the sewage in the secondary space and the discharge channel flows quickly to the sewage outlet, which can sweep the residual sewage in the discharge channel in all directions and speed up the flow of sewage in the discharge channel to the liquid collection well. The setting of the annular secondary nitrogen branch pipe is also conducive to the diffusion of nitrogen in the secondary space, speeding up the replacement rate of gas in the secondary space, and improving the safety of the cargo containment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the schematic diagram of the layout of continuous resin strips or distance-keeping flat steels on the bilge;

[0024] Figure 2 It is the general arrangement diagram of the sewage rapid discharge structure of the membrane type cargo containment system;

[0025] Figure 3 yes Figure 2 Partial section view at AA in the middle;

[0026] Figure 4 Figure 3 A partial enlarged view of point B in the middle;

[0027] Figure 5 It is the schematic diagram of the sub-space nitrogen system;

[0028] Figure 6 It is a schematic diagram of the horizontally coated resin strip and the grid;

[0029] Figure 7 It is a schematic diagram of longitudinally coating resin strips;

[0030] Figure 8 It is a schematic diagram of the resin coating method for the entire cabin;

[0031] Among them, 1-liquid collecting well, 2-discharge channel, 3-isolated empty tank, 4-liquid cargo tank, 5-sub-layer nitrogen main pipe, 6-grid, 7-sewage pump suction pipeline, 8-sewage pipe, 9-sub-layer nitrogen branch pipe, 10-sewage outlet, 11-water inlet monitoring device, 12-resin rubber strip, 13-iron stopper, 14-dihedral angle area insulation board, 15-pad, 16-valve group, 17-nitrogen generator, 18-liquid cargo tank inner bottom plate, 19-nitrogen branch pipe bracket. DETAILED DESCRIPTION

[0032] The present invention will be further described in conjunction with the accompanying drawings.

[0033] like Figure 2 As shown in the figure, a method for rapid sewage discharge of a membrane-type cargo containment system is provided. Since there is a possibility of water flowing around the bulkheads of the liquid cargo tank, a sunken discharge channel is provided around the bottom surface of the liquid cargo tank. A grid for water seepage is provided on the top surface of the discharge channel, and the discharge channel is connected to the secondary space. The grid is installed in the non-adhesive area under the dihedral insulation board, that is, the length of the grid W is less than the spacing W1 between the two pads of the dihedral insulation board, satisfying W1=W+60~80 mm, and the distance between the edge of the grid and the center point of the nearest resin strip H is 15~40 mm, as shown in the figure. Figure 6 This can not only guide the sewage into the discharge channel, but also does not affect the fixation of the dihedral insulation board. Figure 4 As shown in the figure, under the bottom plate of the cargo tank in the grid installation area, a ring of annular stop iron matching the shape of the grid is welded to receive the grid. The thickness and material of the grid are the same as those of the inner bottom plate. After the grid is aligned and fixed by welding, its top surface is flush with the inner bottom surface of the hull.

[0034] like Figure 2 As shown, a liquid collecting well is provided in the isolated empty compartment adjacent to the stern direction of the liquid cargo tank, and the liquid collecting well is adjacent to the discharge channel. A sewage outlet is provided at the bottom of the discharge channel in the stern direction. The sewage pipe connected to the sewage outlet is connected to the liquid collecting well, and the depth of the liquid collecting well is greater than the depth of the discharge channel. A sewage pump suction pipeline connected to the sewage pump is also provided in the liquid collecting well. When there is leakage or condensation water in the cabin, the liquid flows along the bulkhead to the bottom of the cabin and enters the discharge channel through the grille. Due to the stern trim of the ship during operation, the water in the discharge channel flows toward the stern direction of the cabin, and after being collected at the sewage outlet, it flows into the liquid collecting well through the sewage pipe, and then the sewage in the liquid collecting well is discharged by the sewage pump.

[0035] At the same time, in order to speed up the drainage rate in the discharge channel, maintain dryness, and maintain a stable nitrogen input in the secondary space under large-scale drainage conditions, the secondary nitrogen main pipe is connected from the liquid collecting well to the discharge channel in the isolated empty compartment, and is connected to the annular secondary nitrogen branch pipe in the discharge channel. There are multiple exhaust holes along the secondary nitrogen branch pipe, and the secondary nitrogen branch pipe is fixed in the discharge channel through the nitrogen branch pipe bracket under the liquid cargo tank. The nitrogen filling pipeline is separated from the sewage discharge pipeline, and they do not share the same pipe. In addition, a water inlet monitoring device is provided in the discharge channel to monitor the water inlet situation in the discharge channel. Once the warning water level is reached, the drainage pump power is increased to ensure that the liquid level in the discharge channel does not touch the nitrogen branch pipe. Figure 5 As shown, when the ship is in operation, the nitrogen generated by the nitrogen generator enters the nitrogen main pipe through the control of the valve group, and then flows to each liquid cargo tank. Taking a single liquid cargo tank as an example, before entering the liquid cargo tank, the nitrogen main pipe is branched into a secondary nitrogen main pipe and a main nitrogen main pipe. For the secondary space, the nitrogen enters the discharge channel and the cabin through the annular secondary nitrogen branch pipe exhaust hole in the discharge channel after passing through the secondary nitrogen main pipe. Due to the filling of nitrogen in the secondary space, the secondary space and the discharge channel present positive pressure. When there is liquid in the discharge channel, under this pressure, the liquid flows rapidly toward the drain pipe to avoid liquid residue in the discharge channel. The setting of the annular secondary nitrogen branch pipe is also conducive to the diffusion of nitrogen in the secondary space, accelerating the replacement rate of gas in the secondary space, and improving the safety of the cargo containment system.

[0036] A discharge channel is set on the bottom of the cargo hold, and the discharge channel and the secondary nitrogen branch pipe are sunk. The sewage discharge pipe is separated from the nitrogen filling pipe. Nitrogen enters through the secondary nitrogen branch pipe, and sewage is discharged through the discharge channel and the sewage pipe. The discharge channel and the secondary nitrogen branch pipe are both located below the bottom of the liquid cargo tank, and the discharge channel, the secondary nitrogen branch pipe and the bottom of the liquid cargo tank are separated at different levels to avoid sewage accumulation on the bottom of the liquid cargo tank, thereby preventing nitrogen from meeting the accumulated sewage when filling the liquid cargo tank. This solves the problem of sewage and nitrogen conflicting at the bottom of the liquid cargo tank, resulting in sewage not being able to be discharged and nitrogen not being able to enter.

[0037] While accelerating the drainage rate, it is also necessary to improve the fluidity of the liquid at the sewage leakage point or the condensate formation point, so that it can quickly flow to the bottom of the cargo hold, and no water will be left in the gaps between the resin strips under the insulation board. Therefore, it is necessary to define the method of coating the resin under the insulation board in each area. For the dihedral area insulation board and the plane area insulation board, there are usually two coating methods, such as Figure 6 The resin strips are shown horizontally. Figure 7 It is a longitudinally coated resin strip. Figure 8As shown in the figure, since the ship is in a state of stern trim when sailing, in order to ensure the unobstructed water flow channel between the resin strips and ensure that the overall water flow direction is downward and towards the stern, according to the typical insulation arrangement scheme of the MARK type cargo containment system, for the plane area insulation board, only the upper and lower inclined surfaces are required to be coated with resin strips longitudinally, and the other decks are required to be coated with resin strips transversely. For the dihedral area insulation board, only the dihedral insulation board where the upper and lower inclined surfaces intersect with the front and rear decks, and the dihedral insulation board where the left and right decks intersect with the front and rear decks are coated with resin strips longitudinally, and the other dihedral insulation boards are coated with resin strips transversely. When water flows on any deck, the liquid will quickly drain to the bottom of the cabin along the gaps between the resin strips on the bulkhead, and there is no transverse resin strip to block the drainage channel. After the liquid reaches the bottom, it will immediately penetrate into the discharge channel through the grille, and will not cause overflow to the internal area of ​​the bottom. At the same time, it is ensured that there is no water accumulation under the insulation board of each deck.

Claims

1. A method for rapid discharge of sewage from a film-type cargo containment system, characterized in that: An isolation void tank is provided at one end of the liquid cargo tank, a sunken discharge channel (2) is provided at the bottom of the liquid cargo tank and along the circumference of the liquid cargo tank, the discharge channel is communicated with the secondary space, a grille (6) is laid above the discharge channel (2), the grille (6) is located in the non-adhesive area under the dihedral insulating plate, and a circle of annular stop iron (13) matching the shape of the grille (6) is welded below the liquid cargo tank inner bottom plate (18) in the grille installation area, the grille (6) is aligned and fixed by welding, and after fixing, the top surface of the grille (6) and the liquid cargo tank inner bottom plate (18) are located on the same horizontal plane; A liquid collecting well (1) is provided at the bottom of the isolation void compartment (3), the liquid collecting well (1) is adjacent to the discharge channel (2), a sewage outlet (10) is provided at the bottom of the discharge channel (2) in the stern direction, the sewage outlet (10) is connected to a sewage pipe (8), the sewage pipe (8) is connected to the liquid collecting well (1), and a sewage pump suction pipeline (7) extends into the liquid collecting well (1); A secondary nitrogen main pipe (5) is arranged in the isolation air chamber (3), and a secondary nitrogen branch pipe (9) is arranged inside the discharge channel (2) and along the circumference of the discharge channel. The secondary nitrogen main pipe (5) is connected to the discharge channel (2) from the side of the liquid collecting well (1) and is connected to the secondary nitrogen branch pipe (9). A plurality of exhaust holes are provided on the secondary nitrogen branch pipe (9); The inner surface of the cargo tank (4) is coated with a resin strip (12). For the plane area insulation board, only the upper and lower inclined surfaces are longitudinally coated with the resin strip (12), and the other decks are transversely coated with the resin strip (12); for the dihedral angle insulation board (14), only the dihedral angle insulation board where the upper and lower inclined surfaces intersect with the front and rear decks, and the dihedral angle insulation board where the left and right decks intersect with the front and rear decks are longitudinally coated with the resin strip (12), and the other dihedral angle insulation boards are transversely coated with the resin strip (12).

2. A method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: The grid length W is less than the distance W1 between the two pads of the dihedral insulating plate, satisfying W1=W+60~80 mm.

3. The method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: The thickness and material of the grille are the same as those of the cargo tank inner bottom plate (18).

4. The method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: The secondary nitrogen branch pipe (9) is fixed in the discharge channel (2) through a nitrogen branch pipe bracket (19) under the bottom plate (18) in the liquid cargo tank.

5. The method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: A water inlet monitoring device is provided in the discharge channel, and the water inlet monitoring device is connected to the drainage pump.

6. A method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: The nitrogen generator (17) is connected to the nitrogen main pipe through a valve group (16).

7. The method for rapid discharge of sewage from a film-type cargo containment system according to claim 1, characterized in that: The distance H between the edge of the grille and the center point of the nearest resin strip is 15~40mm.

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