KR101935650B1 - Maintenance method of membrane type lng storage tank on ground - Google Patents

Abstract

The present invention relates to an LNG storage tanks, which are installed in a LNG storage tank to be repaired, comprising: installing temporary equipment in the LNG storage tank; repairing and reinforcing the steel roof; and testing whether the steel roof is defective or not. As a method, the present invention opens the LNG storage tank which has been shut down after a certain period of use, so that the LNG can be safely stored again.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an LNG storage tank,

The present invention relates to a method for opening and repairing an LNG storage tank installed on a ground for a long time.

Natural gas is a fossil fuel containing methane as a main component and a small amount of ethane, propane, and the like, and has recently been regarded as a low-pollution energy source in various technical fields.

Natural gas is produced or transported at sea and stored in the LNG storage facility on the ground and supplied to the consumer.

Liquefied natural gas is obtained by cooling natural gas at cryogenic temperatures (below about -162 ° C) and its volume is reduced to about 1/600 of that of natural gas, making it well suited for long distance transport through the sea.

LNG transported onshore is stored in a landfill storage tank. Since liquefied natural gas is about -162 ° C, liquefied natural gas storage tanks are made of materials that can withstand extremely low temperatures such as stainless steel, aluminum steel and 35% nickel steel to safely store liquefied natural gas, It is designed to be resistant to heat shrinkage and to prevent heat penetration.

The storage and handling of LNG should be safe while being a good energy source, so LNG storage tanks are installed on the ground by strict process procedures.

However, in the conventional liquefied natural gas storage tank, there is a construction procedure for each process necessary for the construction. However, the repairing operation of the storage tank is not as difficult as the construction, but the maintenance method for the long- It is not in the state.

The matters described in the background art are intended to aid understanding of the background of the invention and may include matters which are not known to the person of ordinary skill in the art.

It is an object of the present invention to provide a method of repairing an LNG storage tank that has been shut down after a certain period of use by opening the LNG storage tank so that the LNG can be safely stored again.

A method of opening and repairing a ground type membrane-type LNG storage tank according to one aspect of the present invention includes the steps of installing a temporary equipment in a LNG storage tank to be repaired, repairing and reinforcing the steel roof, ≪ / RTI >

The step of testing for the presence or absence of defects in the steel roof is characterized in that at least one of helium test, liquid penetrant test, vacuum box leakage test and air pressure leak test is carried out.

The step of installing the hypothetical equipment includes the steps of injecting a temporary material through a manhole or a gas dome hole of the LNG storage tank, removing the insulation material and the plywood of the upper part of the deck, and checking the iron roof of the LNG storage tank And a step of installing a hypothetical scaffold.

The step of demolishing the insulation and the plywood is characterized in that the plywood is numbered for pre-demolition of the plywood.

In the step of installing the temporary scaffold, a main beam is installed on the upper part of the deck to prevent an excessive load directly from being applied to the upper part of the deck, And is gently installed.

In addition, the step of installing the temporary equipment may further include the step of installing a fall prevention scaffold around the edge of the deck.

The fall prevention scaffold is installed in a main beam of the steel roof.

In addition, the step of installing the hypothetical equipment may further include the step of installing a membrane protection plywood on the bottom edge of the membrane.

In addition, the step of installing the hypothetical equipment may further include a step of installing a bone core on the deck upper insulation.

The step of installing the hypothetical equipment may further include the step of installing a gondola on the edge of the deck to check the membrane wall of the LNG storage tank.

Here, in the step of installing the gondola, in the case of the LNG storage tank in which the gondola monorail is installed in the lower part of the deck, the aluminum sheet on the deck edge (two places) on which the gondola is to be installed is disassembled.

Alternatively, in the step of installing the gondola, in the case of the LNG storage tank provided with the gondola monorail on the deck, the aluminum sheet on the edge of the deck is disassembled in a circumferential direction of a predetermined width or more for installation and operation of the gondola do.

According to the method of opening and repairing the geomembrane-type LNG storage tank of the present invention, it is possible to safely install the temporary facilities before the operation after opening the storage tank to prevent safety accidents, By thoroughly verifying the steel roof, it is possible to ensure the safety of the storage tank to be restarted by securing the airtightness of the steel roof.

FIGS. 1 and 2 relate to a method of installing a temporary equipment in the LNG storage tank of the present invention.
FIG. 3 shows a main beam and a stiffener beam airtight reinforcement welding method of an LNG storage tank according to the present invention.
FIGS. 4 and 5 illustrate the iron roof helium inspection section and the injection method of the LNG storage tank.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In describing the preferred embodiments of the present invention, a description of known or repeated descriptions that may unnecessarily obscure the gist of the present invention will be omitted or omitted.

Install temporary equipment and power equipment at designated locations for steel roof and membrane inspection and repair.

1. Installation of Hypothesis Equipment

A 300 ton crane is used to transport material for tank maintenance, and a 100 ton crane for material handling is transported inside the tank.

Material transport cranes are used to transport the temporary material to the material stack adjacent to the manhole above the storage tank, and then to the inside of the tank through the manhole to transport the material to the inside of the tank.

The gondola, trolley, and frame are transported by manpower through the manhole, the membrane, the protective plywood and the gondola body are made of gas dome hole (gas) dome material hole.

A material winch and fall protection network are installed directly above the top dome of the tank to transport the material to the bottom of the membrane. The 2-ton winch is used to transport the protective plywood and gondola materials to the bottom of the membrane.

Next, remove the insulation and plywood from the top of the deck.

Firstly remove the box-shaped insulation located at the edge of the deck, and remove the 5-meter wide insulation at the edge of the deck to ensure space for operation and passage.

Also, it is desirable to remove the plywood installed at the edge of the deck for gondola movement and nondestructive inspection, and to number the plywood before demolition so that it can be installed at the same position when reinstalling.

2. Installation of protective plywood and core

As shown in FIG. 1, after the deck edge insulator and the plywood are demolished, a fall prevention scaffold 36 is installed using a main beam at the edge of the iron roof to prevent falling and falling objects, In order to prevent falling, the membrane protection plywood (38) is installed on the membrane in the circumferential direction more than 3m from the membrane bottom edge wall.

The protection plywood should be installed so as not to create a gap, and a protection plywood should be installed under the gas dome hole with a size of 10 m (10 m) x 10 m (10 m) or more in order to prevent falling when the material is transported.

When the iron roof is moved, protective plywood is installed in the moving passage (37) to protect the deck AL-sheet. In the un-demolished area outside the moving passage area, a corrugated stone is installed on the upper part of the heat insulating material. Prevent possible sparks.

Next, a hypothetical scaffold is installed to check the iron roof.

The scaffold scaffold is installed sequentially from the edge of the deck to the center, and the edge of the deck is installed stepwise due to the inclination of the iron roof as shown in Fig.

3. Installation of membrane inspection gondola

The installation of the gondola depends on the location of the gondola monorail in the tank.

If the gondola monorail is installed at the bottom of the deck, there is no need to dismantle the AL-sheet separately for gondola operation. However, we disassemble the aluminum sheet at the designated place for gondola installation, and install gondola equipment after installation of scaffolding scaffolding.

If the gondola monorail is installed on the top of the deck, it is necessary to disassemble the aluminum sheet at the edge of the deck in a circumferential direction over a certain width so that the gondola can be operated.

4. Installation of power equipment inside the tank

The electric power maintenance facility for tank internal maintenance is designed to install the panels, transformers, distribution boards, cables, etc. in the tank outside and to supply power to the inside of the tank. After installing the distribution panel at the top of the deck and the bottom of the membrane, do.

The electric power facility uses a lifting wire, a fixing means, etc. through a vacuum vessel line above the tank, and a power cable is installed, and a light is installed on a deck upper installation scaffold and a membrane entrance ladder.

5. In-tank air inlet and exhaust fan installation

When the installation of the above-mentioned hypothetical equipment and electric power equipment is completed, the inside of the tank is undergoing maintenance work. For the work environment of the operator, the air supply equipment (IA) Continuously inject air to maintain a 20% oxygen concentration.

Then, after dismantling 2 places of Vacuum Breaker at the upper part of the tank, exhaust fan is installed to discharge harmful gas and dust generated in the inside of the tank to the outside of the tank.

As described above, when the inspection and preparation before the opening of the tank is completed, the tank is opened to put the actual operator in charge to perform the necessary repair and reinforcement work, and when the repair and reinforcement work is completed, the adequacy of the repair is judged by the test.

Repair and reinforcement work will be carried out after completion of steel roof installation and scaffold installation.

형상(41)의 보강자재를 부착하여 기밀보강용접을 실시하게 된다. 메인 빔 기밀보강용접 연결부는 기밀보강용접 완료 후 공기가압누설시험을 위하여 홀이 가공된 보강자재(40)를 사용한다.That is, the airtightness of the main beam and the stiffener beam of the steel roof and the spaced space between the steel roof and the steel roof are sealed by air tight reinforcement welding to secure the airtightness of the storage tank, As shown in Fig. 3, the main beam is shaped like a letter 39, and the stiffener beam

The reinforcement material of the shape 41 is attached to perform air tight reinforcement welding. The welded joints of the main beam hermetic reinforced weldings are made of reinforced materials (40) with hole machined for air pressure leakage test after completion of airtight reinforcement welding.

This type of reinforced steel roof is to be reinforced and welded, and at the same time, it is checked whether there is a defect in the base metal of the steel roof and the welded part.

1. Visual inspection (VT, Visual test)

Perform a general visual inspection of the inside of the tank (steel roof and membrane), the state of the base material and welds, the corrosion and cracking of the internal structure.

The object to be visually inspected inside the tank is the body, the edge, the base material and the welded part of the internal structure of the steel roof, the base material and the welded part of the membrane.

2. He test

Helium gas (trace gas) is injected into the space between the steel plate at the edge of the steel roof and the concrete roof to locate the defects of the base material and welds.

First, install a pressure gauge inside the tank to measure the pressure at the edge of the iron roof and the inner barrier space (IBS).

Install a pressure gauge (mercury or water U-Tube) in the inlet and outlet lines for helium injection, and remove paint and foreign substances on the surface to be inspected.

For helium inspection at the edge of the steel roof, a helium inlet and a temporary hose are installed in the base material and the IBS outer ring.

As shown in FIG. 4, the helium inlet of the iron roof was drilled to form a total of 26 holes (18 iron roof edges, 3 gas dome holes, and 5 pump nozzle holes) , Helium is injected into the base material and welded part of the edge of the steel roof and the leakage of helium to the steel roof nozzle part and the gas dome welded part.

The helium inlet is used as a helium concentration measuring point for helium entry, and a helium inlet can be additionally installed for smooth helium diffusion at the edge of the iron roof if necessary.

In addition, a water guard is installed at two IBS outer rings to automatically discharge the pressure when an overpressure is generated over the set pressure (0.5 kPa) of the IBS, thereby protecting the IBS.

In the case of steel roof edges, the inspection method shall be changed according to the inspection area.

Figure 5 shows the iron roof edge helium inspection zone, denoted Q, R, S, T, U.

For the Q and R zones of the steel roof edge, helium was injected through the helium inlet provided in the edge of the steel roof edge Q ~ R and the helium gas reference concentration (1.0 × 10 ^-4 mbar, l / sec) Helium test is carried out.

The helium measurement can be an inlet that is not used for the injection of a large number of helium inlets, and the injection is performed sequentially for a number of helium inlets having a specified concentration.

For the S, T, and U zones of the steel roof edge, helium gas is injected directly into the IBS outer ring and the concentration is measured. If more than 5% is confirmed, helium test is performed.

The injection of helium is carried out by selecting two outer rings and maintaining the IBS pressure.

When helium flow diffusion is confirmed in the entire outer ring, helium gas is continuously injected so that the reference concentration of helium can be maintained at 5% or more, and helium test is performed. When the IBS pressure of the outer ring helium gas is higher than 0.5 kPa Do not.

Next, for the gas roof of the steel roof nozzle part and the gas dome welding part, three helium injection holes are provided in the base material around the welded part, one for helium gas injection (injection pressure 5 to 20 kPa) It is used for.

In the iron roof nozzle part, five helium injection holes are installed in the base material around the weld, one helium gas injection (injection pressure 5 ~ 20kPa) and four helium concentration measurement.

The above-mentioned helium injection hole can be inspected after additional installation, if necessary, for a welded area where nondestructive inspection is difficult due to iron roof structure interference.

As described above, it is judged that the repair is completed when the helium is supplied according to the zone, and the result is not higher than the helium concentration value measured in the first atmosphere at the entire edge portion of the steel roof edge inspection.

3. Liquid Penetrant Test (PT)

Repair of iron roof and reinforcement of airtightness, repair of membrane After completion of welding, it is a method to check presence or absence of surface defects in base material and welded part by using penetrating agent and developer.

Liquid penetrant inspection is subject to airtight reinforcement welds, repair welds, base metal parts, and other defects suspected in the steel roof, and the membrane has repair welds, base metal, and other deep defects.

After the pretreatment such as removing the foreign materials of the specimen, the permeate is applied 24 hours after the welding with the minimum penetration time by spraying, brushing, etc.

The shape of the penetration instructions may include independent penetration instructions, line penetration instructions, circular penetration instructions, sequential penetration instructions, and instructions for dispersal penetration, and may thus include cracks, line defects, circular defects or independent defects, .

4. Vacuum Box Test (VBT)

It is a test to find the defective part by applying the foaming liquid to the surface of the test body, attaching the vacuum box, forming the negative pressure, and checking the bubbles generated through the leakage part.

Vacuum box leakage tests include iron roof repair welds, lap joint welds, base metal parts, and other defects suspicions. Membranes include repair welds, base metal, and other deep defects.

The foaming liquid (foam-forming solution) is preferably composed of liquid detergent, glycerin, and water in a ratio of 1: 1: 4.5.

The foam-forming solution forms a film that does not escape from the test surface, and the foam formed should not rapidly disappear by drying or low surface tension of the air.

The size of the vacuum box should be made to fit the type and type of the specimen and the vacuum box should withstand at least 100kPa (1atm, 1bar) external pressure.

The bottom surface of the vacuum box is opened, a sponge-type gasket is attached for sealing, and the upper surface forms an observation window.

The surface temperature of the test section should be in the range of 5 to 50 ° C (40 to 125 ° F) and should be locally heated or cooled if the temperature can not be maintained within the range of 5 to 50 ° C (40 to 125 ° F) do.

The application time of the foaming liquid should not exceed 1 minute and care should be taken not to exceed the maximum allowable temperature. If the temperature is excessively high, there is a possibility that the foamed liquid is dried and evaporated or the boiling point is lowered and bubbles are formed in the foamed liquid.

After the foaming liquid is applied on the test surface, a vacuum box is placed on the test surface. After vacuum is formed at -200 mbar for the first time and -550 mbar for the second time, the test is performed for about 30 seconds. It can be judged that there is no leakage due to the foaming liquid.

5. Air Tightness Test (ATT)

In order to ensure the airtightness of the reinforced welded part of the steel roof, air is supplied to the inside through a hole (40) provided in the reinforcing weld, and the foam test solution is applied to the welded part under pressure to find the leakage position.

The supply of dry air for the test is used through the Instrument Air supply equipment installed on the top of the tank.

Foam test solution shall be 1: 1: 4.5 ratio of semolon, glycerin and water.

The foam test solution should form a film that does not escape from the test surface, and the foam formed should not rapidly disappear by drying or low surface tension of the air.

The surface temperature of the test specimen shall be maintained within the range of 5 to 50 ° C (40 to 125 ° F) during the test period. However, when the surface temperature of the EUT is cooled down to 5 ℃ or less, a certain amount of antifreeze is mixed with the foam test solution, and the application test is carried out on another specimen, and the temperature range can be adjusted according to the result.

After applying the foam test solution using the sprayer on the test surface, it is checked whether the foam is generated and it is proved that the foam is leaked when the foam is generated.

Then, Rust Grip coating is applied to the reinforced steel roof reinforcement inside the tank and the existing steel plate weld to prevent corrosion and ensure airtightness.

Remove foreign matter such as rust, dust and tar on the paint surface and welds, mix paint properly, and paint using brushes, rollers, etc.

Completion of iron roof first painting, complete drying for 24 hours and second painting.

The coating thickness should be more than 80μm to prevent corrosion of steel roof and ensure airtightness.

Lt; / RTI >

Once the final coating on the steel roof has been completed, the temporary equipment and electrical equipment installed to repair the tank will be removed.

In the reverse order of scaffold installation, the scaffold is demolished from the center of the steel roof in the circumferential direction, and the demolished material is loaded on the deck at the edge of the deck and removed to the outside of the tank immediately after demolition.

Then remove the scaffolding to the edge of the iron roof and remove the gondola.

In the case of gondolas, the trolleys are removed from the top of the deck and taken out through the entry manhole, and the gondola cage is disassembled from the bottom of the membrane and taken out through the gas dome hole.

Remove protective plywood and corrugated pavement from the top of the deck, and protective plywood from the edge of the bottom of the membrane, and remove the winch and structure from the top of the tank when the temporary removal of the interior of the membrane is complete.

The top of the tank exhaust fan, the perimeter of the manhole, and various safety facilities are sequentially removed, and the material handling crane is taken out of the liquid detergent by using a crane of 300ton or more from outside the liquid repellent.

Gondolas, trolleys, frames, etc. Once the equipment is demolished, re-install plywood and box-type insulation in the reverse order of removal, and install additional insulation on top of the deck to compensate for thermal effects.

Finally, the electric power facilities such as lighting fixtures and cable ladders installed on the ladder and membrane ladder are removed and the demolition work is finished.

36: Fall prevention scaffold
37:
38: Membrane protection plywood
39: Main beam reinforcement material
40: main beam reinforcing material connection portion
41: stiffener beam reinforcing material

Claims (16)

delete Installing the temporary equipment inside the LNG storage tank opened for maintenance,
The step of installing the hypothetical equipment comprises:
Injecting a temporary material through a manhole or a gas dome hole of the LNG storage tank;
Removing the insulation and plywood from above the deck; And
And installing a hypothetical scaffold for checking the iron roof of the LNG storage tank.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 2,
Wherein the step of demolishing the insulation and the plywood is characterized in that the plywood is numbered for pre-demolition location of the demolishing plywood.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 3,
Wherein the step of installing the hypothetical scaffold is stepwise installed on the edge of the deck.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 4,
The step of installing the hypothetical equipment comprises:
Further comprising the step of installing an anti-fall scaffold along the perimeter of the deck,
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 5,
Characterized in that the fall preventing scaffold is installed in a main beam at the edge of the iron roof.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 5,
The step of installing the hypothetical equipment comprises:
Further comprising the step of providing a membrane protection plywood on the membrane bottom edge.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 5,
The step of installing the hypothetical equipment comprises:
Further comprising the step of installing a protective plywood on a moving path for protecting the deck AL-sheet and installing a core bone on the deck upper insulation when the iron roof is moved.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 5,
The step of installing the hypothetical equipment comprises:
Further comprising installing a gondola at the deck edge to inspect the membrane wall of the LNG storage tank.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 9,
In the step of installing the gondola,
Wherein the gondola monorail is disposed in the lower portion of the deck, and in the case of the LNG storage tank, the aluminum sheet on the deck on which the gondola is to be installed is dismantled.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 9,
In the step of installing the gondola,
Characterized in that in the case of the LNG storage tank in which the gondola monorail is installed on the upper part of the deck, the aluminum sheet on the edge of the deck is disassembled in the circumferential direction of a certain width or more for the operation of the gondola.
A method for opening and repairing a ground type membrane type LNG storage tank. Installing the temporary equipment inside the LNG storage tank opened for maintenance,
The step of installing the hypothetical equipment comprises:
Injecting a temporary material through a manhole or a gas dome hole of the LNG storage tank;
Removing the insulation and plywood from above the deck;
Providing an anti-fall scaffold along the perimeter of the deck;
Providing a membrane protection plywood on the membrane bottom edge;
Installing a core block on the deck upper insulation material;
Installing a hypothetical scaffold for checking the iron roof of the LNG storage tank; And
And installing a gondola on the deck to inspect the membrane wall of the LNG storage tank.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 12,
Wherein the step of installing the hypothetical scaffold is stepwise installed on the edge of the deck.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 12,
Characterized in that the fall preventing scaffold is installed in a main beam of the steel roof edge.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 12,
In the step of installing the gondola,
Wherein the gondola monorail is disposed in the lower portion of the deck, and in the case of the LNG storage tank, the aluminum sheet on the deck on which the gondola is to be installed is dismantled.
A method for opening and repairing a ground type membrane type LNG storage tank. The method of claim 12,
In the step of installing the gondola,
Characterized in that in the case of the LNG storage tank in which the gondola monorail is installed on the upper part of the deck, the aluminum sheet on the edge of the deck is disassembled in the circumferential direction of a certain width or more for the operation of the gondola.
A method for opening and repairing a ground type membrane type LNG storage tank.

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