KR20120095727A - Bonding method for barrier of lng cargo - Google Patents

Abstract

PURPOSE: A bonding method of a barrier of LNG cargo is provided to prevent adhesion decrease due to thermal impact by having an optimized bonding thickness, and to improve airtightness by obtaining an adhesive strength against repetitive head load. CONSTITUTION: A bonding method of a first metal foil and a second metal foil as a barrier of LNG cargo comprises: a flame surface treatment step(S100) of forming a surface oxide layers on a first metal foil and a second metal foil by a flame surface treatment of the first metal foil and the second metal foil; and an adhesive layer formation step(S110) forming an adhesive layer between the surface oxide layers. In the flame surface treatment step, pure methane or propane gas is used as a flame source for flame surface treatment.

Description

Bonding method of LNG carrier barrier {BONDING METHOD FOR BARRIER OF LNG CARGO}

The present invention relates to a liquefied natural gas cargo hold construction, and more particularly, to a method for bonding a liquefied natural gas cargo hold barrier.

In general, liquefied natural gas (LNG) refers to a colorless transparent cryogenic liquid whose natural gas, which is methane-based, is cooled to -163 degrees Celsius and its volume is reduced to one hundredth.

Such liquefied natural gas carriers for transporting liquefied natural gas, floating offshore structures for producing and storing liquefied natural gas, etc. are provided with a cargo hold capable of storing and storing the liquefied natural gas liquefied in the cryogenic state.

Such LNG carriers generally use corrugated membrane sheets as the primary barrier, and laminates (eg, triplex) or metal foils of metal and glass fibers as secondary barriers.

For example, the triplex used as the secondary barrier is basically formed by adhering a glass fiber sheet to both sides of the aluminum sheet, and the rigidity is different depending on the thickness of the aluminum sheet and the resin used.

These triplexes include Rigid Secondary Barriers (RSBs), Flexible Secondary Barriers (FSBs), and Semi Rigid Triplex (SRTs).

RSB has relatively high rigidity as it is manufactured by impregnating a glass fiber sheet in a semi-cured state into a prepreg state by pressing the thermosetting resin in a semi-cured state before bonding the aluminum sheet and the glass fiber sheet. Therefore, it is also called a rigid triplex.

FSB is ductile, made from fiberglass sheets, adhesives, and relatively thin aluminum sheets, also referred to as supple triplex.

SRT refers to a triplex with a thicker aluminum sheet and less ductility than FSB.

The secondary barrier using such triplex is made by pressing and bonding two triplexes of different stiffness and epoxy adhesives according to the pressure, temperature and time defined in the Bonding Handbook.

However, a composite material such as triplex has a problem of lowering the sealing effect when the viscosity of the adhesive impregnated in triplex is high.

In particular, composite materials such as triplex are subjected to repeated thermal loads, i.e., repeated thermal shocks, resulting in cracks due to the difference in the coefficient of thermal expansion between the internal reinforcing fibers of the fiberglass sheet and the adhesive resin, which may cause gas leakage. It may be.

In addition, before the shipment of liquefied natural gas into the cargo hold or storage tank of the liquefied natural gas carrier, the rapid change of temperature from room temperature to cryogenic temperature causes the triplexes to contract and expand repeatedly, and such triplexes are stored at very low temperatures for a long time. Since it is used, a problem may occur that the adhesion between the triplexes is reduced.

When the adhesive strength between the triplexes is thus weakened, adhesion failure occurs at the interface between them, and there is a possibility that gas leaks through the adhesion failure.

On the other hand, the secondary barrier may be configured using a metal foil as mentioned above.

For example, the insulating structure of the LNG carrier cargo hold according to the prior art is attached to the inner surface of the hull 1 of the LNG carrier by an epoxy mastic 2 and a stud bolt 3, as shown in FIG. A fixed lower insulation panel 4 and an upper insulation panel 5 installed above the lower insulation panel 4 are included.

In addition, the insulating structure of the LNG carrier cargo hold according to the prior art is a glass wool flat joint 6 is inserted into the gap (A) which is a space between the lower insulation panel (4) and to configure a secondary barrier And a first metal foil 7 attached between the upper insulation panel 5 and the lower insulation panel 4.

In addition, the insulating structure of the LNG carrier cargo hold according to the prior art is the adhesive layer 8 formed on the upper surface of the first metal foil 7 around the gap (A), and is located above the gap (A) and the adhesive The second metal foil 9 is attached to the first metal foil 8 using the layer 8.

In addition, the insulating structure of the LNG carrier cargo hold according to the prior art is the top bridge panel 10, the upper insulation panel 5 and the top bridge panel 10 attached to the upper side of the second metal foil (9) It may include a corrugated membrane sheet 11 is installed on the same plane of the top.

However, since the insulating structure of the LNG carrier cargo hold according to the prior art is also a method in which the metal foils are bonded through the adhesive layer, since the adhesive force of the metal foil is affected by the surface treatment conditions and the adhesive thickness of the metal foil, Despite the use of foils to construct secondary barriers, there is a disadvantage that it is very difficult to build confidence in the adhesive strength of metal foils against repeated thermal loads.

The embodiment of the present invention provides a method for treating the surface of the secondary barrier considering the thermal shock, and can solve the problem of reducing the adhesive force due to thermal shock by presenting the optimized adhesive thickness, and ensures the sealing strength by securing the adhesive strength against repeated thermal loads It is intended to provide a method for bonding LNG barriers that can bring about an improvement.

According to an aspect of the present invention, in the method of bonding a first metal foil and a second metal foil as a barrier for liquefied natural gas cargo, the surface treatment of the first metal foil and the second metal foil is carried out to perform a first surface treatment. A flame surface treatment step of forming a surface oxide layer on the metal foil and the second metal foil and removing contaminants such as rolling oil remaining on the surface of the metal foil, and between the surface oxide layer formed on the first metal foil and the second metal foil A method of adhering a liquefied natural gas cargo hold barrier comprising an adhesive layer forming step of forming an adhesive layer may be provided.

In addition, the flame surface treatment step, the flame surface treatment to the first metal foil and the second metal foil for a flame surface treatment time of 5 seconds to 10 seconds, the surface oxide layer on the first metal foil and the second metal foil Can be formed.

In addition, in the flame surface treatment step, pure methane or propane gas may be used as the flame source for the flame surface treatment.

In addition, in the flame surface treatment step, the flame surface treatment temperature may be applied to 800 degrees to 1000 degrees.

In addition, the first metal foil and the second metal foil may be made of aluminum, and the thickness of the first metal foil or the second metal foil may be formed to be 0.2 to 0.4 mm.

In addition, the first metal foil and the second metal foil may be made of a stainless material, and the thickness of the first metal foil or the second metal foil may be formed to be 0.1 to 0.3 mm.

In addition, the thickness of the adhesive layer in the adhesive layer forming step may be formed of 0.1 ~ 0.3 mm.

In addition, in the adhesive layer forming step, the adhesive layer may be formed by applying a liquid adhesive or an adhesive film.

In addition, after the adhesive layer forming step, an adhesive step of adhering the first metal foil and the second metal foil using an adhesive jig may be further performed.

In addition, an inspection step of inspecting and repairing the adhesion site may be further performed after the adhesion step.

Since the embodiment of the present invention does not use a composite material such as triplex, the adhesive force between the triplexes decreases due to prolonged use at an extremely low temperature, or the thermal expansion coefficient difference between the internal reinforcing fibers of the glass fiber sheet and the adhesive resin. There is an advantage that can prevent the problem of cracks and gas leakage due to the source.

In addition, embodiments of the present invention provides a surface treatment method and an adhesive thickness capable of exhibiting the adhesive strength to reliably perform the liquid tight and / or airtight function required by the secondary barrier despite repeated thermal shock, The reliability of the adhesive strength of the metal foil can be improved, and as a result, a reliable secondary barrier in which gas and / or liquid do not leak can be realized.

In addition, the embodiment of the present invention provides the barrier of the LNG cargo hold with excellent airtightness and liquidtightness properties in which the adhesive strength is not drastically reduced or the sealing properties are not rapidly changed despite 300 times of repeated thermal shocks. There are advantages to it. Here, 300 times means the number of thermal shocks that can be applied to the cargo hold when simulated under the conditions that a general liquefied natural gas carrier or a floating offshore structure producing and storing liquefied natural gas is operated for 20 years. can do.

In addition, the embodiment of the present invention can provide an optimized surface treatment condition compared to the economic or mechanical properties compared to the existing surface treatment, there is an advantage that can provide a very reasonable adhesion method in terms of cost or productivity.

In addition, the embodiment of the present invention by optimizing the thickness value for each material of the metal foil which can eliminate the fear of damage in manufacturing and handling, ensure flexibility in the secondary barrier construction, and facilitate the adhesion treatment In addition, there is an effect of ensuring the adhesive construction quality of the secondary barrier while easily handling the metal foil.

1 is a cross-sectional view showing an insulating structure of the LNG carrier cargo hold according to the prior art.
2 is a flow chart of a method for bonding a LNG cargo barrier according to an embodiment of the present invention.
3 is an exploded cross-sectional view of the barrier to which the bonding method of the present invention is applied.
Figure 4 is a graph showing the adhesive strength of each metal foil surface treatment.
5 is a graph showing the adhesive thickness in consideration of the adhesive strength according to the heat load recovery of the metal foil.

Hereinafter, the method of adhering the liquefied natural gas cargo hold barrier according to the embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

The following specific examples are only illustrative of the liquefied natural gas cargo hold barrier adhesion method according to the present invention, and are not intended to limit the scope of the present invention.

Figure 2 is a flow chart of a method for bonding the LNG cargo barrier in accordance with an embodiment of the present invention, Figure 3 is an exploded cross-sectional view of the barrier applied to the bonding method of the present invention.

As shown in FIG. 2, an embodiment of the present invention provides a flame surface treatment step (S100) for a first metal foil and a second metal foil for a LNG cargo barrier, and a first metal foil and a second metal foil. The adhesive layer forming step (S110) between the surface oxide layer of the, and the first metal foil and the second metal foil bonding step (S120) using the adhesive jig, and the inspection step (S130) for inspecting and repairing the adhesive site may be included. have.

2 or 3, the first metal foil 100 and the second metal foil 300 may be formed as a barrier, more specifically, a secondary barrier of the LNG cargo hold.

The surface oxide layer 101 may be formed on the first metal foil 100 by the flame surface treatment step S100.

The surface oxide layer 301 may be formed on the second metal foil 300 by the flame surface treatment step S100.

The first metal foil 100 may be installed and used in the insulation panel 40, and the second metal foil 300 may be attached to the first metal foil 100 with the adhesive layer 200 interposed therebetween. It can be described as.

This embodiment, through the steps (S100 ~ S130), present a specific and reliable surface treatment method or condition, the adhesive layer 200 between the first metal foil 100 and the second metal foil (300) By suggesting the optimum range for the thickness of the, it is possible to ensure the adhesion construction quality of the secondary barrier even in repeated thermal shock.

In general, as the insulation panel 40 has a size of 1m x 3m, the construction and adhesive strength of the insulation panel 40 are generally considered as the second barrier, so that the first metal foil 100 and the second metal foil 300 are The flame surface treatment mentioned was applied.

In other words, the mechanical or chemical treatment method used for general metal surface treatment is actually the entire surface area in a place having a large size, such as the first metal foil 100 and the second metal foil 300 for liquefied natural gas cargo barrier. It can be very difficult to process uniformly.

For example, a chemical surface treatment method, such as sulfuric acid etching, requires an acid bath. A general-scale pickling bath smaller than 1 m x 3 m may be applied to the first metal foil 100 and the second metal foil 300. Since it is difficult to apply, it can be very unreasonable in terms of cost and productivity.

In addition, in the case of grit blasting, which is generally applied among mechanical treatment methods, since the grit is sprayed at a high pressure, the first metal foil 100 or the second metal foil 300 having a large size is easily formed. Deformation or localized surface treatment differences occur, and it is difficult to form a uniform roughness depth (Rz) throughout the surface, and it is difficult to optimize the grit blasting conditions for the first metal foil or the second metal foil. .

Therefore, referring to FIG. 2, in this embodiment, a flame surface treatment step S100 for the first metal foil and the second metal foil, which are very reasonable in terms of cost or productivity, may be provided.

In the flame surface treatment step (S100), a relatively simple equipment configuration and processing may be performed by using a device (eg, a multi-flame gun mounted on a large gantry device) capable of performing flame surface treatment on a metal foil surface. Can be.

At this time, it is necessary to find an optimal time for the surface oxide layer to be produced on the first metal foil and the second metal foil to exhibit an adhesive quality that can withstand repeated thermal shocks according to the flame surface treatment time, or to achieve the optimum carbonization. very important.

To this end, the applicants and inventors of the present application can be applied to the cargo hold when simulated under the condition that the vessel, such as a general LNG carrier, or a floating offshore structure that produces and stores LNG, is operated for 20 years. It was found that the number of times of thermal shocks was about 300 times, and the surface component analysis was performed according to the flame surface treatment time.

As a result, as shown in Table 1 below, the surface components of the first metal foil and the second metal foil for each flame surface treatment time could be analyzed.

In Table 1, the carbon and nitrogen values have a minimum value at 7 seconds, and the adhesive strength (for example, adhesion force) may be maximum.

That is, the flame surface treatment step (S100) is a flame surface treatment of 5 seconds to 10 seconds considering that the carbon and nitrogen values are minimized compared to other flame surface treatment time component values so as to prevent a sudden decrease in the adhesive strength even after repeated thermal shocks. The surface treatment may be performed on the first metal foil and the second metal foil for a time to form a surface oxide layer on the first metal foil and the second metal foil.

Figure 4 is a graph showing the adhesive strength of each metal foil surface treatment.

Referring to FIG. 4, the metal foil may be a graph showing adhesive strength for each surface treatment using any one of the aforementioned first metal foil or second metal foil.

At this time, the flame surface treatment temperature was applied 800 degrees Celsius ~ 1000 degrees.

Here, as a comparative example, the flame surface treatment time for the metal foil is 5 seconds to 10 compared with no surface treatment, wear with sandpaper, grit blasting, sulfuric acid etching, and flame surface treatment of less than 5 seconds (for example, 3 seconds). It can be seen that the optimum adhesive strength is exerted when the second.

Here, the optimized adhesive strength may be one in which the workability is comprehensively considered along with the adhesive strength.

That is, when examining with reference to [Table 1], FIG. 4, and FIG. 5, a sudden decrease in adhesive strength can be prevented even with repeated thermal shocks.

Here, the flame surface treatment time of the minimum carbon and nitrogen values compared to the component values for each flame surface treatment time can be confirmed that the 5 seconds to 10 seconds.

If the flame surface treatment is less than 5 seconds, the adhesive strength may be lowered as a result, and if the flame surface treatment is more than 10 seconds, the carbon and nitrogen values are excessively large, and consequently the adhesive strength may also be lowered. In addition, the value of 5 seconds to 10 seconds corresponds to a critical value that can exert superior mechanical properties compared to general surface treatment or surface treatment time.

In addition, the flame surface treatment temperature of 800 degrees to 1000 degrees may also be understood as a critical value capable of forming a surface oxide layer having optimized carbon and nitrogen values within 5 to 10 seconds.

The first metal foil and the second metal foil may be made of aluminum or stainless material, respectively, and may be manufactured to have a thickness and a material selected within a thickness range for handling during construction and maintaining adhesive quality.

For example, the first metal foil and the second metal foil may be made of aluminum, and the thickness of each of the first metal foil or the second metal foil may be 0.2 to 0.4 mm.

In addition, the first metal foil and the second metal foil is made of a stainless material,

Each of the first metal foil or the second metal foil may have a thickness of 0.1 to 0.3 mm.

Thus, since the thicknesses of the first metal foil and the second metal foil may be minute but different, the flame surface treatment temperature and the flame surface treatment time may be applied to correspond to the difference.

In addition, in order to have optimized carbon and nitrogen values, the flame source for flame surface treatment is also tasteless, odorless and colorless pure methane or propane gas rather than butane, which produces relatively much soot. Preference is given to using.

5 is a graph showing the adhesive thickness in consideration of the adhesive strength according to the heat load recovery of the metal foil.

Referring to FIG. 5, in general, the thicker the adhesive thickness is, the more the adhesive force decreases in relation to the thickness of the adhesive layer between the first metal foil and the second metal foil, so as to be used to attach the first metal foil and the second metal foil. Although there are studies, there is no definition of adhesive thickness considering the reduction of adhesive strength by repeated thermal shock.

Thus, in this example, repeated thermal shock (eg, thermal load) tests are performed to initiate the optimal thickness of the adhesive layer.

Here, thermal shock was simulated by repeatedly applying -196 degrees and room temperature (25 degrees) using liquid nitrogen.

As a result of the thermal shock test, the adhesive layer may have a thickness selected from 0.1 to 0.3 mm, and the experimentally optimized value is 0.15 mm.

That is, when the 0.15mm adhesive thickness, it can be seen that the adhesive strength gradually decreases up to 300 times the thermal shock, but in contrast, when the thickness is thick (for example, 0.5mm or 1.0mm as a comparative example), 30% to 50 by only one thermal shock It can be seen that the adhesion may be reduced by more than%.

At this time, when the adhesive thickness is less than 0.1mm, it may be difficult to uniformly apply the liquid adhesive to the first metal foil or the second metal foil when constructing the liquid adhesive, and when the adhesive thickness is greater than 0.3mm, the adhesive strength may be sharply lowered. As such, the value of 0.1 to 0.3 mm also corresponds to a critical value that can exhibit superior mechanical properties compared to the thickness of the general adhesive layer.

Therefore, referring to FIG. 2 or FIG. 3, in the step of forming an adhesive layer (S110) between the surface oxide layers 101 and 301 of the first metal foil 100 and the second metal foil 300, a liquid adhesive or an adhesive film is formed. The adhesive layer 200 may be formed to have a thickness of the above-mentioned value by applying.

Here, when the adhesive layer 200 is composed of an adhesive film, the adhesive film is attached to the surface oxide layers 101 and 301 of either the first metal foil 100 or the second metal foil 300, and protected. A film (not shown) may be provided on the adhesive film or any one of the surface oxide layers 101 and 301 to prevent adhesion of foreign matter.

In addition, when the adhesive layer is composed of a liquid adhesive, the liquid adhesive is attached to the surface oxide layer of either the first metal foil or the second metal foil, and a protective film (not shown) is formed on the liquid adhesive or the surface oxide layer ( It is installed on any one of the 101, 301 may prevent the adhesion of foreign matter.

Referring to FIG. 2, the bonding of the first metal foil and the second metal foil using the adhesive jig (S120) may be performed.

In the bonding step (S120), the adhesive between the first metal foil and the second metal foil using an adhesive jig including a pressurizing means capable of applying pressure downward to the second metal foil and a heating pad installed under the pressurizing means. As the layer is cured, the first metal foil and the second metal foil may be bonded.

Here, the pressurizing means may include an airbag. The heating pad may be formed by embedding a planar heating element such as a heat transfer coil or a ceramic heater that may have a flexible flat plate shape.

After a certain time has elapsed after applying heat and pressure by the adhesive jig, the adhesive jig can be dismantled.

Such, after the bonding step (S120) may be a test step (S130).

In the inspection step (S130), the bonding site is inspected whether the bonding is completed so that the first metal foil and the second metal foil have any thickness selected from the thickness of the adhesive layer of 0.1 to 0.3 mm, and if an error occurs, repair work may be further performed. Can be completed, and if the adhesive quality is satisfied without error, the bonding operation can be completed.

Adhesion site inspection may be carried out through technical regulations regarding general barrier-related repairs or maintenance.

In the above embodiment of the present invention is applied to the first metal foil and the second metal foil in configuring the secondary barrier of the LNG cargo hold, the surface of each metal foil is applied to the surface treatment of the flame, at this time the flame surface treatment time Optimized from 5 seconds to 10 seconds, the thickness of the adhesive layer used at the time of adhesion is applied at 0.1 mm to 0.3 mm, pure methane or propane gas is used as the flame source for the flame surface treatment, and the flame surface treatment temperature is 800 degrees. ~ 1000 degrees, and when the first metal foil and the second metal foil is made of aluminum for improved handling and workability may have any one selected from the thickness range 0.2 ~ 0.4mm, respectively, the first metal foil and When the second metal foil is made of a stainless material, there is provided a method for bonding a LNG cargo barrier that can each have a thickness selected from the thickness range 0.1 ~ 0.3mm Can.

Such a technical configuration of the present invention will be understood by those skilled in the art that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the scope of the present invention is represented by the following claims rather than the foregoing description, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts are included in the scope of the present invention. Should be interpreted.

100: first metal foil 101, 301: surface oxide layer
200: adhesive layer 300: second metal foil

Claims (10)

In the method of bonding the first metal foil and the second metal foil as a liquefied natural gas cargo barrier,
A flame surface treatment step of forming a surface oxide layer on the first metal foil and the second metal foil by performing a flame surface treatment on the first metal foil and the second metal foil;
And an adhesive layer forming step of forming an adhesive layer between the surface oxide layer formed on the first metal foil and the second metal foil.
Bonding method of LNG cargo barrier.
The method of claim 1,
The flame surface treatment step,
Flame surface treatment is performed on the first metal foil and the second metal foil for a flame surface treatment time of 5 seconds to 10 seconds, thereby forming the surface oxide layer on the first metal foil and the second metal foil.
Bonding method of LNG cargo barrier.
The method of claim 1,
The flame surface treatment step,
It is characterized by using pure methane or propane gas as the flame source for the flame surface treatment
Bonding method of LNG cargo barrier.
The method according to any one of claims 1 to 3,
The flame surface treatment step,
Flame surface treatment temperature 800 degrees to 1000 degrees
Bonding method of LNG cargo barrier.
The method of claim 1,
The first metal foil and the second metal foil are made of an aluminum material, the thickness of the first metal foil or the second metal foil is formed to 0.2 ~ 0.4mm
Bonding method of LNG cargo barrier.
The method of claim 1,
The first metal foil and the second metal foil is made of a stainless material, the thickness of the first metal foil or the second metal foil is formed of 0.1 ~ 0.3mm
Bonding method of LNG cargo barrier.
The method of claim 1,
In the adhesive layer forming step, the thickness of the adhesive layer is formed in 0.1 ~ 0.3 mm
Bonding method of LNG cargo barrier.
The method according to claim 1 or 7,
In the adhesive layer forming step, the adhesive layer is formed by applying a liquid adhesive or an adhesive film.
Bonding method of LNG cargo barrier.
The method of claim 1,
After the adhesive layer forming step, the step of adhering the first metal foil and the second metal foil using an adhesive jig is further characterized in that the progress
Bonding method of LNG cargo barrier. The method of claim 9,
After the adhesion step, the inspection step for inspecting and repairing the adhesion site is further characterized in that
Bonding method of LNG cargo barrier.

Images