KR20080047321A - Process and system for thermal insulation of cryogenic containers and tanks - Google Patents

Abstract

An insulation system for cryogenic containers and tanks comprising at least dual layered insulation panels with groove-and-ridge cooperating assembly structures as well as a groove for injecting a fluid insulation material into the panels provides an improvement for insulating such containers and tanks.

Description

PROCESS AND SYSTEM FOR THERMAL INSULATION OF CRYOGENIC CONTAINERS AND TANKS

The present invention relates to methods and systems for the insulation of cryogenic vessels and tanks, as well as to insulation plates suitable for use in such insulation systems and methods.

Most can have a low boiling point and therefore exist in the gaseous state under standard conditions (20 ° C., 760 mmHg), such as liquid gas such as liquid ammonia, helium, hydrogen, oxygen, nitrogen, methane, ethane, propane, etc. When transporting cold boiling fluids, they require a much smaller volume than when the liquids are the same mass in the gaseous state, so that these fluids are cooled to as low a temperature as possible to form liquids, thereby facilitating their mass transport. It is advantageous to. However, the problem with this transport is that if the transport container is not very well insulated, a large amount of fluid may disappear through the so-called "boil-off", so it is very good to insulate such a container and tank very well. very important. The temperature interval for such cryogenic fluids may be at intervals of -50 ° C to -273 ° C, preferably at intervals of -100 ° C to -250 ° C, more preferably -125 ° C to -200 ° C. The transport temperature for the relevant fluid that can be stored in such a tank can be at or below the boiling temperature for such fluid as described above. Insulation materials used for such insulation have very rapid thermal gradients, because on the surface facing the vessel there may be a temperature very close to the boiling point for the relevant fluid and on the surface facing the vessel there may be a temperature very close to the ambient temperature. It must be possible to overcome and endure. In addition, these insulations should exhibit a continuous layer around the vessel that provides some temperature transfer points to and from the perimeter as far as possible.

In addition to the pressure issues, it is advantageous to transport such fluids in spherical vessels as described above due to the most advantageous volume-to-surface ratio (other shapes such as cylindrical, prismatic and spheroidal or even cubic vessels would also be appropriate). And the method and system according to the invention are not necessarily limited to this shape. The problem with this container's geometric design is that the insulation must be applicable to surfaces that are curved in three dimensions (but the sides of the cylinder will be curved in two dimensions and the sides of the cube will be flat). Thus, the thermal insulation system for cryogenic containers as described above must also be applicable to all these types of geometries.

Prior art

Among the related prior arts, liquefaction at temperatures below 0 ° C., with a thermal insulation lining consisting of a matrix of cells made of thermal insulation and also preferably a thermal insulation in the joint between matrix cells such as polyurethane. Storage vessels for storing the purified gas are known from US Pat. No. 3,948,406. Also disclosed are methods for forming such linings. The lining according to this prior art is made by forming a layer by applying a polymerizable or curable polymeric composition under, between and over a block of selected insulation when they are placed at the site where the lining is constructed, Such a polymerizable composition constitutes a kind of mortar which is then polymerized and / or cured in situ.

From US Pat. No. 3,420,396 a thermal insulation tank is known which consists of an insulating block which fits in a manner which abuts into a corrugation directed towards the inside of the outer wall of the container and the corrugated wall.

The Japanese patent discloses an insulating structure for a cylindrical cryogenic tank that reduces the amount of bending moment through the maximum bending moment acting on the stud block located proximate the boundary between the hemispherical portion of the cylindrical tank and the cylindrical body of the tank. The structure is formed by joining sections of insulation that are placed in a laminating manner with a wire mesh in an intermediate position between the apparently laminated layers and having a synthetic foaming resin body as a binder.

Conventionally, it is common to add insulation in the form of a strip that is wound continuously around a spherical vessel, where the joining area between each winding of such strip is at the edge region to ensure that the insulation is continuous at the surface of the vessel. It must be glued or welded so that the ends abut each other (see above).

This is shown in FIG.

Such strips are generally placed on the surface of the container in one monolayer. The material of such insulation is generally polystyrene, which is generally used as a material for insulation because it is light in weight and easy to manufacture. However, the present invention is not limited to this heat insulating material.

In addition, plates of insulation are used in the form of a single plate layer for the insulation of cryogenic containers. The conventional insulation plate solution is shown in FIG. This technique requires significant tolerance requirements (small tolerances) in the manufacture of plates. Plate installation during installation requires the use of a mold and the surface requires post-treatment subsequent to molding / casting.

However, due to stricter regulations regarding the transport of cold boiling fluids, one monolayer of such insulation is no longer considered appropriate. As described above, one single addition of an additional layer of insulation in the form of a strip is not economically feasible, and thus a problem arises with proper insulation of such cryogenic containers and tanks.

The present invention aims to solve this problem in one aspect.

In systems and methods according to the invention for isolating cryogenic containers, although other materials with insulating and / or foam forming properties for producing insulating foam materials are possible, for example foamed or extruded polystyrene (EPS) ) Plate is used. Examples of such materials are foamed polyethylene, expanded polystyrene and foamed polyurethane. These plates are of a size which is applied to the curvature of the surface to be insulated, when they are provided as flat surfaces, since they should not provide a gap on the surface of the cryogenic container larger than 15 mm, preferably flat to the container wall. Can be arranged. These intervals will not all be equally limited because air is a good thermal insulator. Plates can also be made with curvatures applied to the surface on which they are to be mounted, but this is undesirable because it can increase the cost of the plates and make their manufacture more cumbersome. It is then more desirable for the plate to be flat, but with smaller dimensions if the container to be covered also has small dimensions.

The general clear spacing is indicated in Figure 3, which shows an embodiment of the system according to the invention. All figures in the figures are in mm. In addition, the thermal insulation structure of the figure is applicable to any tank radius.

One embodiment of a plate of an insulation system according to the invention is shown in FIGS. 4 to 8. Also shown in these figures are the structures of the insulation system according to the invention, including possible insulation for the spaces between the fixing brackets, the joints, and the insulation panels (this insulation is a foam insulation such as polyurethane which is injected into the space under pressure). Is preferred). As shown, a heat insulation comprising at least two layers of heat insulation plates joined together by the aid of the groove-and-ridge system by means of the heat insulation system according to the invention is obtained.

The number of layers of the insulation plate in such a system may also exceed two layers and may even comprise three, four or five layers but the minimum number of layers is two.

An advantageous and preferred heat insulation plate assembly adapted for use in the heat insulation system and method according to the invention is shown in FIG. Such a plate assembly is shown as comprising three layers of insulation plates (EPS) bonded or welded together in a staggered form to form intermediate grooves / tilts on one side of the plate assembly and protruding ridges on opposite sides of the plate assembly. It is. As also shown in FIGS. 4 and 5, the interlayer of the assembly is even displaced / staggered with respect to two adjacent sides of the lower and upper plates of the assembly, such that the ridge and plate assemblies protrude on two adjacent sides of the plate assembly. Groove-and-ridge systems having grooves on the remaining two adjacent sides of the system are created around all four sides of the assembly plate structure.

As mentioned above, the thermal insulation system according to the invention comprises at least two layers of thermal insulation plates, so that the assembly of the thermal insulation plates can comprise at least two layers of thermal insulation plates. However, the two layers of the insulating plates positioned staggered provide an assembly structure that provides the structure to which the plate assembly is fastened, but will not provide a central groove-and-ridge system as described above for the three layers of structure. Can be. This is because the addition of foam to provide a continuous insulating surface covered around the container (unless a groove is provided cut out in at least one of the plates of the assembly, thereby increasing the manufacturing cost of the associated plate) on the top surface of the structure. This may mean having a result of freely foaming. As a result, it is more preferable to use a three-layer assembly structure for the thermal insulation system according to the invention as described above, but a two-layer system is also undesirable but viable.

As shown in Fig. 9, the three-layer plate assembly also provides a crack barrier of the type described below between at least two, preferably all three, of the insulating plate layers of the plate assembly according to the invention. It may include.

When referring to "adhesive" material and "foam forming insulation" herein, these materials may be different from one another, but may preferably comprise one and the same material. One example of such a material is a foamed polyurethane that has "adhesive" by having good adhesion properties to EPS and also a "foam forming insulation" by having good thermal insulation properties.

As shown in FIG. 5 showing an embodiment of the thermal insulation system according to the invention, not only "cross-glued joints" but also "glasswool joints" are indicated and also used in the thermal insulation system according to the invention. Other materials that may be indicated are indicated. In this embodiment glass wool (or even rockwool or other fibrous inert insulation) can be blown between the plate joints and polyurethane can be injected into the joint / injection groove (see below) as an adhesive material.

When a multilayer (two or more) thermal insulation barriers according to the invention are arranged, this can generally begin by placing the thermal insulation plate (or thermal insulation plate assembly) from the top of the cryogenic vessel (but this is the placement of the thermal insulation plate). Is not necessarily necessary because can be started at any position on the surface of the container). The plate / plate assembly may be nailed / bolt to the container wall at regular intervals to ensure the necessary fastening of the system. These nails / bolts represent in principle possible thermal bridges, but they are particularly insulated through the second layer of the insulating plate (or their location is determined and holes are provided for them in the lower layer of the plate assembly, Whereby they are insulated through the injection of foam forming insulation (polyurethane) into the final insulating structure according to the invention]. In addition, other forms are also possible for fastening these plates, such as, for example, adhesion of the plates to the container walls.

The panels are now continuously hooked to each other by the aid of the groove-and-ridge system of the side edges of the plate / plate assembly. One possible alternative home-and-ridge system may provide a plate with a self-locking "click-system" such as present in the floor panel or floor laminate plate. As shown in Fig. 6, the connection area between the insulating plates has a foam tunnel for connecting / adhesive and insulating polyurethane which is a material injected into the joint after the section of the insulating plate is placed. This thermally insulating and foamed material can be poured under pressure to seal all non-hermetic edge regions between the insulating plates according to the invention.

After the first layer of this insulation plate has been placed, fastened and sealed, on top of this layer, the foundation for the second layer of insulation plate which is cured at the top of the first insulation layer and located on top of the first layer in a similar manner A crack barrier in the form of a mesh, sheet or cloth of a synthetic or natural material which can be impregnated with or can be formed can be arranged. Examples of crack barriers can be sheets or meshes of polyethylene or polystyrene having a mesh size within a 0.01 to 100 mm ² spacing impregnated with polyurethane.

Where the vessel / tank insulation according to the invention is formed from a plate assembly prefabricated as described above, the fixing points in the form of crack barrier (s) for the tank insulation and other structures (eg outlets for bolts / nails) , The formation of a layer comprising grooves (s) for insulating adhesives, etc.) is included in the prefabricated assembly (see, eg, FIG. 9). The crack barrier prevents the thermal insulation layer from breaking apart due to the steep temperature gradient that the thermal insulation system withstands.

7 and 8 an embodiment of the structure of the thermal insulation system according to the invention is shown.

A method for placing a heat insulation plate / assembly according to the invention is also shown in FIGS. 10 to 18.

The manufacturing method for each individual insulating plate according to the invention is particularly shown in FIG. 16. FIG. 18 may also be referred to for stratification of the thermal insulation assembly shown in FIG. 8.

A particular feature of the insulation plates of the invention, which are materials of improved sealing properties through the method of installation / assembly of the total insulation structure according to the invention, is that the polymeric material of the joining edge of the ridge / groove in the form of the groove-and-ridge assembly of the insulation plate. The provision of a foam tunnel 61 for (for example polyurethane) (see Fig. 6). This tunnel 61 is provided in the insulation plate to form a continuous web to be filled with foam insulation / adhesive material. As also shown in Fig. 6, this feature of the groove-and-ridge assembly of the thermal insulation plate according to the invention can accommodate any curvature of the tank below for a flat or semi-flat plate being used in the thermal insulation plate. Can be. Moreover, the section of the ridge or groove portion of the joint between the plates has raised edges 62 which form a sealing / fitting edge for the foam tunnel 61. Since the insulating plate is preferably made of a soft or flexible material (for example foamed polyethylene or foamed polystyrene), the plate can receive a certain stress in the bonding area of the foam tunnel. This semi-elastic effect can ensure a nearly or completely hermetic foam tunnel area for the joint between the insulating plates. In addition, because of the curvature of the surface of the container under the thermal insulation structure, the joining edges around the foam tunnel can be further assured a tight seal of the edges pressed against each other to form the foam tunnel.

Because of the semi-flexible / flexible nature of the insulation of the insulation plate, it may be possible to insert the probe / injection needle into the foam tunnel at regular intervals around the vessel / cryogenic tank, or selected insulation in which the injection port provides access to the foam tunnel. The plates may be provided at specific intervals.

In one embodiment, after assembling the insulation plate as described above, it may be possible to ensure a continuous insulation structure in which the foam (polyurethane) foam is being injected into the foam tunnel 61.

As also shown in Fig. 6, the vertical joining gaps between adjacent insulating plates can be staggered with respect to each other, so that a foam tunnel 61 is provided at both the horizontal and vertical joining edges of the insulating plate. .

Following are various examples of the thermal insulation assembly according to the invention.

Their thermal insulation properties are also indicated.

Introduction

The test was carried out in insulation panels for LNG tanks.

The purpose of the test is to set a value for the thermal conductivity per unit area for insulation panels made of foamed and partially elasticized polystyrene, and at this temperature the test panels are subjected to the tension that may occur in practical cases in the insulation system. To expose it. Thermal conductivity (hereinafter referred to as k _value ) is measured at the hot side temperature of about 20 ° C. and the cold side temperature of about −160 ° C. in the horizontal and vertical positions. The k _value is also measured during five subsequent temperature variations during this time and the temperature at the low temperature side of the test panel varies between -162 ° C and 10 ° C. This temperature fluctuation can create tension inside the test panel as in practice.

Test equipment

The test is carried out in a large protective hot plate apparatus with a test section of 2 × 3 m ² . The arrangement of the hot and cold plates is shown in FIG.

The plywood frame inside the ambient insulation is inserted into the aluminum sides of the hot and cold plates to simulate the tension in the test panel.

Test insulation

Insulated specimens are made of a slab of expanded polystyrene with a zone of flexible material mounted on a 0.005 m aluminum sheet with stud bolts (FIG. 2).

Specimens obtained from Ticon Isolering AS are ready for mounting to the apparatus. Specimen size is 2.0 × 3.0 × 0.265 m ³ .

Installation of test panels in the device

The insulation free ambient insulation of the test apparatus is formed from Styrofoam RM slabs and fiberglass cloth bonded together with an adhesive. The corner sections are made of two-way flexible elastomeric styrofoam.

The test specimen is inserted into the test section and sealed to the surrounding insulation with a polyurethane adhesive obtained from Ticon Isolating Ace.

The ambient insulation is hermetically sealed and firmly bonded to the aluminum test plate of the device by the sealing compound. The cross section of the peripheral insulation is shown in FIG. 3.

equipment

The temperature is measured by copper-contantan thermocouples on the hot and cold plates of the insulation panel and on the hot and cold surfaces.

The temperature on the hot side of the thermal insulation is measured at the aluminum foil vapor barrier and the temperature on the cold side is measured at the aluminum sheet.

Additional thermocouples are mounted inside the insulation panel in eight different zones and four different cross sections (FIG. 19).

All temperatures are recorded in a data acquisition system with 400 channels and transferred to a local computer for processing.

The power input to the three sections of the device's main high temperature plate is measured by a precision resistor and a precision voltmeter and controlled by a precision power meter.

Calculation of the thermal conductivity

The evaluation of heat leakage through the stage flow perimeter insulation is performed in advance by the device at a horizontal stage flow position with a test cavity filled with rock wool having a density of 74 kg / m ³ . The thermal conductivity of this material is measured in a horizontally protected hot plate device. After installation of the test panel, the total heat flow rate is measured with the device in horizontal and vertical positions. The apparent thermal conductivity for the test panel at these two positions is calculated as follows.

k _value = Q _i / (F * T;)

k _value = apparent thermal conductivity per unit area for the test panel (W / m ² K).

Q _i = Heat flow through the test panel (W).

F = area of the test panel in m ² .

T _i = temperature difference (K) over the test panel

Q _i = Q _t -Q _p

Q _i = Total heat flow (W).

Q _p = C _p * T _p

Q _p = Heat flow rate through the ambient insulation (W).

c _p = Thermal conductivity (W / K) of the surrounding insulation as confirmed by the calibration test.

T _p = temperature difference (K) over the surrounding insulation.

The effect of convection is assessed by comparison of the apparent thermal conductivity measured at the horizontal and vertical positions.

The accuracy of the measurement is evaluated to be ± 71% or more of the actual value.

Test result

Thermal conductivity is measured at the horizontal stage flow position after one cooling (test no. 190) and at the vertical position (test no. 191). An increase of about 3% is measured at the K _value when compared to the value measured at the horizontal position calibrated to the same average temperature. This is preferably within the accuracy of the apparatus and most of the differences are usually not due to convection in the test specimen.

Thermal conductivity is also measured after five subsequent cooling in vertical and horizontal positions (test nos. 192 and no. 193). These tests and test no. No significant difference was found between 190 and no 191.

Test results are provided in Table I.

TABLE I

Multiple thermocouples are placed inside the insulation panel for bridge or convective currents (see Table II and FIGS. 20, 21, 22 and 23). Temperature irradiation measured at the hot and cold sides of the test panel is provided in FIGS. 20, 21, 22 and 23. FIG.

Inspection of test panel

The test panel is visually inspected from the hot side at low temperature (-162 ° C.) and in the horizontal position. The test panel is then partially exposed to the tension generated by the low temperature in the cold plate, and it may be easy to observe cracks, damage, openings or channels inside the test panel.

Openings are formed in the test panel to detect internal defects or cracks.

As expected, no damage, defect or defect of the structure is found.

Test specimens having a cold side at -162 ° C are removed from the apparatus and inspected from the cold side. The low temperature aluminum sheet is removed to provide good irradiation at the low temperature side of the thermal insulation, and channels, defects and defects are not detected.

conclusion

A small increase in the apparent thermal conductivity of the test panel structure from the horizontal position to the vertical position indicates that the convective current is usually small or very small inside the test panel. Sufficient inspection after the test indicates good function during panel mounting and no cracks or damage inside the panel.

The test panel structure has a reasonable value for the apparent thermal conductivity at the measured temperature and appears to withstand the tension exposed during this test in a good manner.

TABLE II

Area: See FIGS. 20-23.

Introduction

Testing of Sunpor SE (rigid and flexible polystyrene) is carried out at three temperature levels: 20 ° C, -70 ° C and -153 ° C. A total of eight different tests are run, but not all tests are performed on both materials at three temperature levels.

There is no standard created for testing at low temperatures. As a basis for testing, the actual standard (ISO or ASTM) is used.

For each test, the changes made to the actual standard are described.

Low temperature testing is performed in a cold box cooled by a Philips cryogenic generator. The temperature is measured by thermocouples in the air stream and a diagram of the cold box is shown in FIG.

In some tests, values such as elongation must be recorded during the test of the specimen. This is quite difficult when the test specimen is placed in a cold box.

These types of tests are recorded on video tape, which means that the values are subsequently read out with good accuracy.

Test program

Examination of the test program showing the tests performed at each material and temperature level is shown in Table 2.1 for rigid materials and Table 2.2 for flexible materials. The number of test specimens is determined by the customer.

Table 2.1

Table 2.2

Description of the test method

exam no . 1/2: compression test / E-factor

The test is described in ISO 844-1978: "Compression Test for Rigid Materials".

The test method used was as follows.

The test specimen is bonded between two parts of the plywood. The lower part is fastened to the test frame. On the upper plywood plate, a triangular plywood plate is fastened to the movable metal bar. This triangular plate is connected to the line, which extends on two wheels. The tank is filled with water to pressurize the line to compress the material. The displacement as a function of force is recorded by the dial indicator compression test.

The test specimens used had the following dimensions: 55 × 55 × 44 mm ³ . A total of four test specimens are tested at each temperature level.

The compressive strength σ ₁₀ (kPa) is given by the following equation.

here,

F _m is the maximum force reached in Newtons,

s ₀ is the initial area (mm ² ) of the cross section of the test specimen.

The compressive stress σ ₁₀ (kPa) at 10% relative strain is defined as follows.

here,

F ₁₀ is the force (N) corresponding to a relative deformation of 10%,

s ₀ is the initial area (mm ² ) of the cross section of the specimen.

exam no .3 / 4: maximum tensile stress / E-factor

The test is described in ISO 1926: "Standard Test Methods for Cellular Plastics-Determination of Tensile Properties of Rigid Materials".

The standard defines a total of five pieces of testing. The test pieces used had the following shapes and dimensions.

Specimens are somewhat smaller than those specified in the standard. This is done to make it possible to carry out the test in a cold box.

The test specimen is bonded to two parts of the plywood using standard epoxy adhesive. The lower part is fastened to the bottom of the test frame. In the upper part a line extending over the two wheels is fastened. The tank is fastened to the other end of the line. Filling the tank with water means pressurizing the material. Elongations corresponding to the provided forces are recorded at intervals of 5 kg.

The rate of water filling is adjusted to achieve rupture for 3 to 6 minutes.

The maximum tensile stress (σ _m ) expressed in kilopascals is given by the following equation.

here,

F _m The maximum force (N) applied to the specimen during the test.

l -original width of the parallel length of the narrow section of the specimen in mm.

h -original thickness of the parallel length of the narrow section of the specimen in mm.

E-coefficient is defined as the angle of inclination of the curve of elongation as a function of force.

here,

δ -tensile stress (N / mm ² )

Elongation of the material in Δl - δ

l ₀ -length of the test specimen.

exam no . 5: shear modulus

The test method is described in standard ISO 1922-1981: "Cellular Plastics-Determination of Shear Strength of Rigid Materials".

Four specimens are tested at each temperature level. The standard specifies five specimens.

The standard specifies the following dimensions (length-width-thickness): 250 mm x 50 mm x 25 mm in the test specimen.

Smaller test specimens are used in this test to enable testing in cold boxes. The following dimensions (length-width-thickness), i.e. 100 mm x 40 mm x 25 mm, are used.

Firstly, a somewhat larger test specimen is tested, but due to the very strong material, the size is reduced to reduce the force required to obtain rupture. The test equipment cannot support the weight required to rupture the test specimens used initially.

The test specimen is bonded to two parts of the plywood with epoxy adhesive. One of the plywood parts is fastened to the test frame and the other part is movable. A line extending over the two wheels in the movable portion engages the tank at the other end. Filling this tank with water pressurizes the material and moves the movable plywood portion and test specimen upwards.

In the movable plywood section the lines are drawn at approximately cm intervals. The ruler is fastened to the bottom of the test frame. The chair is not moved during the test. This system makes it possible to recognize the elongation of the material.

The tank is filled with water until a rupture is obtained. The test is recorded on video tape and the elongation is subsequently read.

Test equipment is shown in FIG.

exam no . 6: thermal expansion

The test is described in ISO 4897-1985: "Cellular Plastics-Determination of the Coefficient of Linear Thermal Expansion of Rigid Materials Below Ambient Temperature".

The standard defines a test of a total of five specimens with the following dimensions.

Length: 900 ÷ 0-20 mm

Width: 100 to 300 mm

Thickness: 25-50 mm

The material used for this test has the following dimensions.

Length: 244.5 mm

Width: 43.5 mm

Thickness: 42.0 mm

A total of four specimens of each material are tested.

The test specimen is bonded between two parts of the plywood. The lower part is fastened to the test frame. At the center of the upper plywood plate, stainless steel rods are fastened. The rod is connected to a dial indicator placed outside the cold box. Compression / expansion of the material is recorded at different temperatures during cooling or heating of the material.

Calculation of the average linear expansion coefficient (-63 ° C to 20 ° C)

here,

α -average linear expansion coefficient in units of the inverse of Kelvin,

T ₁ Selected higher temperatures in Kelvin,

ΔL -change in length in millimeters of the test specimen between temperature T ₁ and T ₂ ,

L ₀ - original length in millimeters of the test specimens at 23 ± 2 ℃.

exam no . 7: thermal conductivity

The test is performed according to ASTM Standard C 177-85: "Standard Test Method for Measurement of Heat Transfer Characteristics and Steady-State Heat Flux by Protected Hot Plate Apparatus".

exam no . 8 : Poisson  ratio

No standard describes this test. Poisson's ratio [mu] is defined as the ratio between the stretching and shrinking of the material during the tensile stress action.

here,

Δb -change in width in mm,

b ₀ -original width in mm,

Δl -change in length in mm,

l ₀ -Original length in mm.

Test specimens shall be tested no. 3 and no. With the same shape and dimensions as used in 4, the test is performed in the same way.

Test result

Mean values (x) and standard deviations (s) are provided in the table for each test.

Rigid material

exam no . 1/2 compression test / E-factor

Table 4.1

Four specimens are tested at -70 ° C. One of these is pressurized from the equipment.

*) Without reaching 10% compression, the calculated strength is the maximum compressive stress.

(x) = mean value, (s) = standard deviation

Test results are shown in FIGS. 28 and 29.

exam no . 3/4 maximum tensile stress / E-factor

Table 4.2

Eight specimens were tested at 163 ° C and four at -70 ° C.

Two tests are not readable.

(x) = mean value, (s) = standard deviation

Test results are shown in FIGS. 30 and 31.

exam no . 5 shear modulus

Table 4.3

Eight specimens are tested at each temperature level. One test at -163 ° C is not readable on video tape. For the eighth specimen at 20 ° C, rupture appears in the adhesive and not in the test specimen.

(x) = mean value, (s) = standard deviation

Test results are shown in FIG. 32 and FIG.

exam no . 6 columns  expansion

TABLE 4.4

The test results are shown in FIG.

exam no . 7 columns  conductivity

TABLE 4.5

The test results are shown in FIG.

exam no . 8 Poisson  ratio

TABLE 4.6

Four specimens are tested at -163 ° C. One of these is not readable on the video tape.

(x) = mean value, (s) = standard deviation

Flexibility  material

exam no . 1/2 compression test / E-factor

Table 4.7

*) 10% not reached. The calculated strength is the maximum compressive strength.

Four specimens are tested at each temperature level, but one specimen at each temperature level is pressurized from the instrument.

(x) = mean value, (s) = standard deviation

Test results are shown in FIGS. 36 and 37.

Table 4.8

Four specimens are tested at -70 ° C, but one is pressurized from the instrument.

(x) = mean value, (s) = standard deviation

The test results are shown in FIG. 38 and FIG.

exam no . 314 Maximum Tensile Stress / E-Coefficient

Table 4.9

Four specimens are tested at -70 ° C. One of these is not readable on the video tape.

(x) = mean value, (s) = standard deviation

Test results are shown in FIGS. 40 and 41.

Table 4.10

Eight specimens are tested at -163 ° C. One of these is not readable on the video tape.

(x) = mean value, (s) = standard deviation

Test results are shown in FIG. 42 and FIG.

exam no . 5 shear modulus

Table 4.11

(x) = mean value, (s) = standard deviation

Test results are shown in FIGS. 44 and 45.

Table 4.12

Eight specimens are tested at -163 ° C. One of these is not readable on the video tape.

(x) = mean value, (s) = standard deviation

The test results are shown in FIG. 46 and FIG.

exam no . 6 columns  expansion

Table 4.13

The test results are shown in FIG.

Table 4.14

Psalm no. 3 and no. 4 is tested at an onset temperature of -163 ° C. The temperature is raised to -60 ° C. The hot air is then blown into the cold box. Because of this supply of air, the steel rod leaps from the specimen and the test must be completed. The test results are shown in FIG.

exam no . 7 columns  conductivity

Table 4.2.5

The test results are shown in FIG.

Table 4.16

The test results are shown in FIG.

exam no . 8 Poisson  ratio

Table 4.17

Four specimens are tested at 20 ° C. One of these does not bond well enough so that rupture occurs in the adhesive and not in the test specimen.

(x) = mean value, (s) = standard deviation

Table 4.18

(x) = mean value, (s) = standard deviation

conclusion

A total of eight different tests are performed on rigid expanded polystyrene and flexible expanded polystyrene in two directions at three temperature levels (-163 ° C., −70 ° C. and 20 ° C.).

The actual standard describing the test is modified to make it possible to run the test in a cold box.

As indicated by the curves for the different tests, the deviation of the test results is significant. Especially for rigid materials, the stretching and shrinkage of the material is minimized and it is difficult to record the correct value.

Introduction

The test was carried out in insulation panels for LNG tanks.

The purpose of the test is to establish a value for the thermal conductivity per unit area for a thermal insulation panel made of slab of foamed polyurethane with a strip between the elasticizing material (low temperature side) and polyurethane (high temperature side) and at this temperature Exposing the test panel to tensions that may occur in practice in an adiabatic system. Thermal conductivity (hereinafter referred to as k _value ) is measured at the panel hot side temperature of about 20 ° C. and the cold side temperature of about −162 ° C. in the horizontal and vertical positions. The k _value is also measured after five subsequent temperature variations, during which the temperature on the cold side of the test panel has a stabilization period of 4 hours at the hot and cold ends and varies between -162 ° C and 10 ° C. This temperature deviation can create tension inside the test panel as in practice.

Test equipment

The test is carried out in a large scale protected hot plate apparatus with a test section of 2 × 3 m ² specially formed for this test.

The arrangement of the hot and cold plates is shown in FIG.

The plywood frame inside the surrounding insulation is inserted into the aluminum profile of the hot and cold plates to tension the test panel as in a real installation.

Test insulation

Insulation specimens are made of slabs of foamed polyurethane with strips of low temperature flexible material and strips of high temperature polyurethane between slabs mounted on a sheet of 0.005 m with stud bolts. Specimens obtained from UNIASA, Marine Contracting are ready to be mounted in the device.

Specimen size is about 2.0 × 3.0 × 0.29 m ³ .

Installation of test panels in the device

The perimeter stage insulation of the test apparatus is formed of Styrofoam RM slab and fiberglass cloth bonded together with an adhesive. The corner sections are made of two-way flexible elastomeric styrofoam.

The test specimen is inserted into the test section and sealed to the surrounding insulation with a polyurethane adhesive obtained from Unit A, Marine Contracting.

The ambient insulation is hermetically sealed and firmly bonded to the aluminum test plate of the device by a sealing compound.

A cross section of the peripheral thermal insulation and a portion of the thermal insulation panel are shown in FIG.

equipment

The temperature is measured by copper-contantan thermocouples on the hot and cold plates and hot and cold surfaces of the insulation panels. Thermocouple wires are adjusted to an accuracy of ± 0.3 ° C or better, which is in accordance with international temperature standards (ITS-90), for the temperature range used in the test.

The temperature on the hot side of the thermal insulation is measured at the aluminum foil vapor barrier and the temperature on the cold side is measured at the aluminum sheet.

Additional thermocouples are mounted inside the insulation panel at ten different zones and three different cross sections (FIG. 51) (high temperature side, middle region and low temperature side).

All temperatures are recorded as voltages in a data acquisition system with 400 channels and transferred to a local computer for processing.

The power input to the three sections of the device's main high temperature plate is measured by a precision resistor and a calibrated precision digital voltmeter and controlled by a calibrated precision power meter.

Calculation of the thermal conductivity

The evaluation of heat leakage through the part of the polyurethane adhesive joint and the perimeter flow insulation is preliminarily carried out by the device at a horizontal stage flow location with test cavities filled with rock wool having a density of 70 kg / m ³ . The thermal conductivity of this material is measured in a horizontally protected hot plate device. After installation of the test panel, the total heat flow rate is measured with the device in horizontal and vertical positions. The apparent thermal conductivity for the test panel at these two positions is calculated as follows.

k _value = Q _i / (F * T _i ;)

k _value = apparent thermal conductivity per unit area for the test panel (W / m ² K).

Q _i = Heat flow through the test panel (W).

F = area of the test panel in m ² .

T _i = temperature difference (K) over the test panel.

Q _i = Q _t -Q _p

Q _i = Total heat flow (W).

Q _p = C _p * T _p

Q _p = Heat flow rate through the ambient insulation (W).

c _p = Thermal conductivity (W / K) of the surrounding insulation as confirmed by the calibration test.

T _p = temperature difference (K) over the surrounding insulation.

The effect of convection is assessed by comparison of the apparent thermal conductivity measured at the horizontal and vertical positions.

The accuracy of the measurements is as good as possible in this complex structure, in accordance with the method described in NIST Tech Note 1297 (1993) [(NIST = National Institute of Standards and Technology, Gatherersburg, USA)]. It is evaluated to be 71% or more.

Test result

Thermal conductivity is measured at the horizontal stage flow position after one cooling (test no. 198) and at the vertical position (test no. 199).

Thermal conductivity is also measured after five subsequent temperature cycles in the vertical and horizontal positions (test nos. 200 and no. 201).

An increase of about 5.5% was observed in the horizontal test no. 198 (first H) and vertical test no. Measured at K _value between 199 (first V).

An increase of about 9.5% was achieved by the horizontal test 198 (first H) and vertical test no. Measured at K _value between 200 (second V).

Level test no. 198 (first H) and no. No significant difference was measured between 201 (second H).

This difference is small compared to the accuracy of the measurement method.

The increase in k _value in the vertical position compared to the value in the horizontal position is usually due to the cracks observed at the test panel edges described in Chapter 8: Examination of the Test Panel. This is also due to the vertical test no. 199 (first V) and vertical test no. An increase in k _value between 200 (second V) can be explained.

This crack is only observed at the edges close to the adhesive joint and may not usually occur in actual insulation panels.

Test results are provided in Table 7.1.

TABLE 7.1

Multiple thermocouples are placed inside the thermal insulation panel to provide information about the thermal bridge or convective current (see Table 9.1 and Figures 52, 53, 54 and 55 (unfortunately some of the thermocouples are destroyed during testing)).

Temperature irradiation measured on the hot and cold sides of the test panel is provided in FIGS. 52, 53, 54 and 55. FIG.

Inspection of test panel

Of test panel From the high temperature side  inspection

The test panel is visually inspected from the hot side at low temperature (-162 ° C.) and in the horizontal position. The test panel is then partially exposed to the tension generated by the low temperature in the cold plate, and it may be easy to observe cracks, damage, openings or channels inside the test panel.

The hot side is carefully inspected to see if there are any recesses and channels under the aluminum vapor barrier or under the sealing compound (ERFO GUARD FP-VB) on the polyurethane joints between the polyurethane slabs (see Figure 50).

The sealing compound used between the polyurethane slabs (ERFO GUARD FP-VB) is very carefully examined to observe any damage or channels in the aluminum vapor barrier, especially around the recesses.

No such damage, cracks or channels were found at all, and the bonds and insulation to the aluminum foil are considered to have a very good shape. The sealing compound withstands the test in a good manner.

Inspection from inside the test panel

Openings are formed in the test panel edges to detect internal defects or cracks.

Recesses in the aluminum vapor barrier and sealing compound (ERFO GUARD FP-VB) are carefully inspected from the inside, especially for poor adhesion.

No damage or channel was found at the bottom, so the recesses observed on the aluminum foil surface are usually caused by small compression on the hot side and do not affect the measured values.

The adhesion of the aluminum foil and sealing compound to the bottom of the thermal insulation is considered very good.

Some small cracks are found in the test panel (2.0 x 3.0 m) edge region adjacent to the boundary between the thermal insulation around the test apparatus and the test panel as shown in FIG. This crack is located mainly in the middle of the polyurethane slab adjacent to the joint between the slabs. The crack is not considered to reach the hot side from the cold side at any location.

Closer inspection indicates that the crack is considered to start at the boundary between the test panel edge and the surrounding insulation (adhesive joint), usually due to less flexible zones in this edge region.

The central part of the test panel that most closely simulates the actual service conditions in temperature distribution, stress and strain for the entire panel design shows no signs of such cracks and no other failures are observed.

Based on the above and inspection of the cutout from the test panel after the test proceeds, it is concluded that the crack should usually be caused by an undesirably higher tension close to the limit in the adhesive joint used to install the test panel in the test apparatus. You can get off. In addition, the cracks are small and never interconnected, but this may explain the small rise in measured thermal conductivity.

Of test panel From the low temperature side  inspection

The test panel and ambient insulation having a low temperature side at -162 ° C are then removed from the device tool and inspected from the low temperature side at low temperature conditions.

On the low temperature side the aluminum sheet is removed to provide good irradiation on the low temperature side of the thermal insulation system.

No channels, defects and defects are detected except for cracks in the edge regions described above.

Part of the stud bolt is cut away from the panel and carefully inspected. It is considered that no damage or defect is found in the stud bolts inspected.

conclusion

A small increase in apparent thermal conductivity for the test panel from the horizontal position to the vertical position usually indicates that there must be a very small convection current inside the test panel, usually caused by the observed cracks mentioned in Chapter 8.

The inspection of the temperature inside the test panel shown in FIGS. 51 and 52 to 55 and Table 9.1 is carried out at the low temperature side of the vertical joint between polystyrene-slabs (for example between panels no. II and no. VI of FIG. 57). It is considered that there is a small convection current in the flexible material, but this indicates that it is considered to have a very small influence on the measured value on the thermal conductivity.

Careful inspection after the test shows a good function during panel mounting, there is no damage or defect inside the panel, only the small cracks described above (not caused by the panel structure) are found.

The test panel structure has a suitable value for the apparent thermal conductivity at the measured temperature, which is considered to withstand the tension exposed during the test in a good manner. And usually no cracks or defects may be found if it is possible to control the tension in the edge region.

Table 9.1

Claims (14)

An insulating structure for cryogenic tanks or containers comprising a plate of heat insulating material, The plates have mutually cooperative fastening structures at their side edges through their assemblies to form a predominantly continuous layer of insulation, and the fastening area in the insulation plate is characterized by selective cracking between each insulation plate in the assembly or Insulation structure further comprising at least one groove for the addition of polymeric insulation under pressure to fill gaps and / or openings. The heat insulating structure of claim 1, wherein the heat insulating plate is made of expanded or extruded polystyrene (EPS). The insulating structure according to claim 1 or 2, wherein the polymeric insulating material is a liquid material which is injected into an associated groove in the insulating panel. The heat insulating structure according to claim 3, wherein the heat insulating liquid is polyurethane. The cryogenic tank / vessel according to claim 1, wherein the cryogenic tank / container is -50 ° C to -273 ° C, preferably -100 ° C to -250 ° C, more preferably -125 ° C to -200 ° C. Insulating structure adapted to carry cooling liquid within a temperature interval. At least two insulating panels stacked on each other, the contact surface between the plates comprising a crack barrier in the form of a mesh, sheet or cloth of synthetic or natural material, the liquid foam for the panel assembly on at least one of the edges of the panel assembly; Insulation panel assembly representing a groove for providing a forming insulation. The insulation panel assembly of claim 6, wherein the number of insulation panels is three and at least one of the layers of the assembly is displaced with respect to the position of the panels of the other layers. 8. The thermal insulation panel assembly of claim 7 wherein the middle layer of the assembly is displaced relative to the top and bottom layers to form a ridge-and-groove structure at at least two of the side edges of the assembly. The insulated panel assembly of claim 8, wherein the middle layer is displaced relative to the top and bottom layers to form ridge-and-groove structures at all four side edges of the assembly. Use of an insulating panel assembly according to any of claims 6 to 9 for thermally insulating spherical cryogenic vessels / tanks. A method of adding a heat insulating structure according to any one of claims 1 to 9, A layer of foundation material (SCRIM) is added on the surface of the cryogenic tank, a first insulating layer comprising an adhesive material is added on the material, and the insulating material according to any one of claims 6 to 9. At least one of the panel or insulation panel assembly is added, and the associated injection groove in the insulation panel or insulation panel assembly is added with foam forming and liquid insulation under pressure, the liquid insulation in the associated injection groove to form a continuous insulation layer. Can be cured, and if a thermal insulation panel assembly is not used, a thermal barrier is added to the thermal insulation layer, on which the second layer of the thermal insulation panel mainly corresponds to the first layer, and the layer formation method is optionally optional. Repeated a number of times, and optionally a foil of radiation reflective material is added on the insulating structure. The method of claim 11, wherein the thermal insulation panel comprises a panel of foamed or extruded polystyrene. 13. The method of claim 11 or 12, wherein the thermally insulating, liquid, foam forming material added to the injection groove comprises polyurethane. The method of claim 11, wherein some or all of the insulation panels of the first insulation layer or insulation panel assembly are nailed / bolt to the vessel / tank wall.

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