Flexible high-temperature-resistant heat-shielding sheath and preparation method thereof

Abstract

The present application relates to the field of engineering machinery, and particularly relates to a high-temperature-resistant oil cylinder protection structure and a protection method. Specifically, the present application provides a flexible high-temperature-resistant heat-insulating sheath and a preparation method thereof. The present application is designed as a composite structure with high-temperature-resistant fiber cloth as a soft shell and heat-insulating inorganic fiber and inorganic powder as fillers. The flexible high-temperature-resistant heat-insulating sheath has the structural characteristics of simple production, softness, lightness, easy disassembly, anti-collision, tensile resistance, compression resistance and shock resistance, and the performance characteristics of good heat resistance, low thermal conductivity and excellent heat insulation effect, and can realize omnidirectional high-temperature protection of a working device and components.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery, and in particular to a protective structure and method for high-temperature resistant hydraulic cylinders. Background Technology

[0002] Hydraulic cylinders are energy conversion devices that transform hydraulic energy into mechanical energy and are the actuators of hydraulic transmission systems. Due to their simple structure, high reliability, and smooth transmission, they are widely used in construction machinery. With the continuous development of the construction machinery industry, application scenarios are becoming more diversified, and the applicability of hydraulic cylinders in high-temperature environments is an important research direction. Sometimes, fire trucks need to operate continuously for several hours in a 600℃ high-temperature environment. The cylinder barrel and sealing elements of ordinary hydraulic cylinders cannot withstand such high-temperature conditions, easily leading to seal failure, causing hydraulic system malfunctions, and thus affecting fire rescue operations.

[0003] In existing technologies, high-temperature protection for hydraulic cylinders mainly employs two techniques: cooling and insulation. Cooling techniques include internal cylinder cooling with circulating water, piston rod cooling with circulating water, and external cylinder cooling with copper tubing and circulating water. These measures are effective in reducing cylinder temperature and protecting seals, but they are only suitable for fixed facilities with water sources inside factory buildings, and not for mobile equipment like construction machinery. Insulation techniques include spraying thermal barrier coatings and using multi-layer composite insulation sleeves. Thermal barrier coatings provide short-term insulation, but because the coating is too thin, it cannot provide long-term insulation. The most commonly used multi-layer high-temperature protective sleeve is composed of a steel plate-insulation layer-steel plate composite. Although it can provide some insulation, its structure is complex, difficult to form, and it is difficult to achieve complete coverage, resulting in high manufacturing costs. Summary of the Invention

[0004] To address the problems of poor mobility and flexibility in water-cooled circulation systems and the difficulty in fabricating high-temperature protective structures in existing technologies, this invention provides a flexible high-temperature resistant heat-insulating sleeve and its fabrication method. This flexible high-temperature resistant sleeve uses high-temperature resistant fiber cloth as a flexible outer shell and heat-insulating and heat-resistant inorganic fibers and powders as inner filling, forming a multi-layered composite flexible high-temperature resistant protective structure.

[0005] In one aspect, this application provides a flexible sheath, comprising a flexible outer shell and inorganic fibers and inorganic powder disposed within the shell; the flexible outer shell comprises a surface structure and an inner structure made of fire-resistant cloth; the inorganic fibers are fire-resistant fibers;

[0006] At least one of the inorganic powders contains water of crystallization, and the inorganic powder containing water of crystallization can cool down by losing water of crystallization when heated, and / or, at least one of the inorganic powders can expand when heated and block heat conduction.

[0007] The flexible sheath of this invention has a flexible outer shell made of fire-resistant cloth. In this invention, fire-resistant cloth refers to a special fabric made of fire-resistant fibers, suitable for fire protection and high-temperature environments, including but not limited to glass fiber cloth, ceramic fiber cloth, and aluminosilicate fiber cloth. In some embodiments, the surface and inner layers of the flexible outer shell are respectively composed of one or more of high-silica cloth, aluminosilicate fiber cloth, polycrystalline alumina fiber cloth, and zirconium aluminum ceramic fiber cloth. Composite fire-resistant cloth can be obtained by layering and sewing multiple types of fire-resistant cloth.

[0008] When the surface or inner structure uses fire-resistant fabric made of composite materials, the order of composite bonding will affect the heat insulation performance and user experience of the sheath.

[0009] For the surface structure, if a composite material with high-silica cloth is used, it is preferable to place the high-silica cloth on the outermost side (the side away from the filler), because the surface of the high-silica cloth is smooth and burr-free, and can be touched directly by hand, which is safe and reliable.

[0010] For the inner layer structure, if a composite material with high silica cloth is used, it is preferable to place the high silica cloth on the side in contact with the oil cylinder, while other types of refractory cloth are placed on the side in contact with the filler, because the high silica cloth has a dense texture and can protect inorganic fibers and powder from leakage.

[0011] In some embodiments, the surface structure of the flexible shell is composed of three materials in sequence: high-silica cloth, polycrystalline alumina fiber cloth, and high-silica cloth.

[0012] In some embodiments, the inner layer structure of the flexible shell is composed of a high-silica cloth and a zirconium aluminum ceramic fiber cloth, with the high-silica cloth on the side in contact with the hydraulic cylinder.

[0013] In some embodiments, the surface structure of the flexible shell is composed of three materials in sequence: high silica cloth, polycrystalline alumina fiber cloth, and aluminum silicate fiber cloth, with the high silica cloth on the outermost side.

[0014] In some embodiments, the inner layer structure of the flexible shell is composed of a high-silica cloth and a polycrystalline alumina fiber cloth, with the high-silica cloth on the side in contact with the hydraulic cylinder. The flexible shell made of refractory cloth exhibits good high-temperature scorching resistance and thermal insulation properties. In some embodiments, the permanent linear change of both the surface and inner layers of the flexible shell after heating at 1000℃ for 24 hours is ≤-1.5%. In some embodiments, the average thermal conductivity (600℃) of the surface layer of the flexible shell is 0.105 W / (m·K) to 0.115 W / (m·K) (e.g., 0.110 W / (m·K)). In some embodiments, the average thermal conductivity (600℃) of the inner layer of the flexible shell is 0.110 W / (m·K) to 0.120 W / (m·K) (e.g., 0.115 W / (m·K)).

[0015] In some embodiments, the permanent linear change of the flexible housing after heating at 1000°C for 24 hours is ≤-2%. In some embodiments, the average thermal conductivity (600°C) of the flexible housing is 0.110 W / (m·K) to 0.150 W / (m·K) (e.g., 0.115 W / (m·K), 0.120 W / (m·K), 0.125 W / (m·K), 0.115 W / (m·K)).

[0016] In some embodiments, the outer layer thickness of the flexible outer shell is 1.5 mm to 3.5 mm (e.g., 2 mm, 2.5 mm, or 3 mm). In some embodiments, the inner layer thickness of the flexible outer shell is 1 mm to 3 mm (e.g., 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, or 2.5 mm).

[0017] The flexible sheath of this invention uses inorganic fibers and inorganic powder as fillers. The ratio of the two can be adjusted according to actual needs.

[0018] The inorganic fibers used in this invention are fibrous inorganic refractory materials, including but not limited to fiberglass knitted felt, alumina fibers, silica fibers, glass fibers, ceramic fibers, zirconia fibers, mullite fibers, aluminosilicate fibers, and rock wool fibers. The inorganic fibers used in this invention can be selected from one or more of the above-mentioned fibers. In some embodiments, the inorganic fibers are a combination of alumina fibers, silica fibers, and glass fibers. In some embodiments, the weight ratio of the three fibers is 3-4:2-3:1-2, for example, 3:2:1. In some embodiments, the inorganic fibers are a combination of glass fibers, ceramic fibers, zirconia fibers, and mullite fibers. In some embodiments, the weight ratio of the four fibers is 1-2:3-4:2-3:2-3, for example, 1:3:2:2.

[0019] Inorganic fibers can be combined to obtain the desired high-temperature ignition resistance and thermal insulation properties. In some embodiments, the permanent linear change of the inorganic fibers after heating at 1000°C for 24 hours is ≤-3%. In some embodiments, the permanent linear change of the inorganic fibers after heating at 1000°C for 24 hours is ≤-2%. In some embodiments, the permanent linear change of the inorganic fibers after heating at 1000°C for 24 hours is ≤-1.5%. In some embodiments, the average thermal conductivity (600°C) of the inorganic fiber is 0.100 W / (m·K) to 0.150 W / (m·K) (e.g., 0.105 W / (m·K), 0.110 W / (m·K), 0.115 W / (m·K), 0.120 W / (m·K), 0.125 W / (m·K), 0.130 W / (m·K), 0.135 W / (m·K), 0.140 W / (m·K) or 0.145 W / (m·K)).

[0020] In some embodiments, the length of the inorganic fiber is 10 mm to 200 mm (e.g., 20 mm, 50 mm, 80 mm, 100 mm, 120 mm, 150 mm, or 180 mm). In some embodiments, the diameter of the inorganic fiber is 2 μm to 6 μm (e.g., 3 μm, 4 μm, or 5 μm).

[0021] The inorganic powder used in this invention contains at least one type of water of crystallization, and / or at least one type of inorganic powder capable of expanding at high temperatures. At high temperatures, the inorganic powder containing water of crystallization can cool down by losing its water of crystallization, and the powder capable of expanding at high temperatures can act as a barrier to heat conduction. Optional inorganic powders include, but are not limited to, hydrotalcite, magnesite, dolomite, kaolin, attapulgite, lime powder, vermiculite powder, wollastonite, mica powder, diatomaceous earth, silica, titanium dioxide, aluminum hydroxide, hollow glass microspheres, zeolite, porous silicates, aluminum silicate, beryllium oxide, aluminates, and zinc borate. The inorganic powder used as the filler in the sheath of this invention can be one or more of the above-mentioned inorganic powders. In some embodiments, the inorganic powder is a combination of hydrotalcite, attapulgite, silica, and hollow glass microspheres. In some embodiments, the inorganic powder is a combination of wollastonite, mica powder, diatomaceous earth, silica, and titanium dioxide. In some embodiments, the inorganic powder is formed by mixing the components in equal weight ratios.

[0022] The inorganic powder may have a flake-like or spherical morphology, and the average particle size may be 30 nm to 300 μm (e.g., 50 nm, 100 nm, 500 nm, 1 μm, 10 μm, 20 μm, 30 μm, 50 μm, 100 μm or 200 μm).

[0023] Inorganic powders can be combined to obtain the desired thermal insulation properties. In some embodiments, the average thermal conductivity (600°C) of the inorganic powder is 0.030 W / (m·K) to 0.110 W / (m·K) (e.g., 0.050 W / (m·K), 0.070 W / (m·K), or 0.100 W / (m·K)).

[0024] The ratio of inorganic fibers to inorganic powder can be adjusted to obtain high-temperature ignition resistance and thermal insulation properties. In some embodiments, the weight ratio of inorganic fibers to inorganic powder is 5:1 to 10:1 (e.g., 6:1, 7:1, 8:1 or 9:1).

[0025] In some embodiments, the average thickness of the filled flexible sheath can be 8mm to 10mm (e.g., 8.5mm, 9mm, 9.5mm, or 9.7mm). Of course, depending on the actual situation and needs, the flexible sheath can have other thicknesses in other embodiments of the present invention, and this is not a unique limitation.

[0026] The flexible sheath of the present invention can be used for high-temperature insulation protection of hydraulic cylinders or other mechanical equipment or components, especially irregularly shaped mechanical equipment or components.

[0027] In one aspect, this application provides a method for preparing the above-mentioned flexible sheath, comprising the following steps:

[0028] (1) Cut fire-resistant cloth to the appropriate size according to the size of the mechanical equipment or components to make a flexible shell;

[0029] (2) Take a certain amount of inorganic fiber and inorganic powder and mix them evenly;

[0030] (3) Place the mixture from (2) evenly into the flexible shell described in (1);

[0031] (4) Use fire-resistant sewing thread (e.g., high-silica sewing thread) to fix the edges of the outer shell, and evenly stitch the outer shell at intervals of 20mm to 50mm (e.g., 40mm) in both the horizontal and vertical directions to fix the outer shell into 400mm sections. 2 ~2500mm 2 Square grid;

[0032] (5) Roll the outer casing into a cylindrical sheath and fix it to the mechanical equipment or component using fasteners (such as adhesive snaps, metal clips, shuttle buckles or D-ring metal adjustment buckles).

[0033] Figure 1 This is a simplified structural diagram of the flexible high-temperature resistant heat insulation sleeve of the present invention.

[0034] In one aspect, this application provides the use of the aforementioned flexible sheath for high-temperature protection of mechanical equipment or components (such as hydraulic cylinders or motors).

[0035] Terminology Definition

[0036] In this application, thermal conductivity refers to the amount of heat transferred through a 1-square-meter area within a certain time under steady-state heat transfer conditions, given a temperature difference of 1 degree Celsius (K, °C) between the two surfaces of a 1-meter-thick material. The unit is watts per meter per degree Celsius (W / (m·K)). Thermal conductivity can be used to measure the thermal insulation performance of an object. Thermal conductivity can be determined according to YB / T 4130-2005 Test Method for Thermal Conductivity of Refractory Materials (Water Flow Plate Method).

[0037] In this application, heating linear change refers to the irreversible change in length (expressed as a percentage of the original length) of an unshaped refractory material after heating. Heating linear change can be used to measure the high-temperature ignition performance of an object. The method for determining heating linear change can be based on GB / T 5988-2022, "Test Method for Permanent Linear Change of Refractory Materials under Heating," which involves placing the object to be tested in a muffle furnace and igniting it at 1000℃ for 24 hours, then measuring the dimensional changes before and after ignition.

[0038] In this application, the specific value of high temperature may vary under different circumstances, such as not less than 100℃, not less than 200℃, not less than 600℃, not less than 1000℃, not less than 1580℃, not less than 1770℃, or not less than 2000℃.

[0039] In this application, refractory materials refer to materials whose physical and chemical properties allow them to be used in high-temperature environments. According to the degree of refractoriness, they can be divided into: ordinary refractory materials: 1580℃~1770℃, high-grade refractory materials: 1770℃~2000℃, and special-grade refractory materials: >2000℃.

[0040] Beneficial effects of the invention

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The flexible high-temperature resistant heat insulation sleeve provided by the present invention uses flexible material as the outer shell, and has the characteristics of being soft and lightweight, easy to disassemble and assemble, providing tight protection, preventing bumps and knocks, resisting pressure, resisting tension, and resisting shock.

[0043] 2. The selected protective shell and inorganic fibers have the characteristics of good heat resistance, low thermal conductivity and excellent heat insulation effect, which can achieve all-round protection for mechanical equipment or components.

[0044] 3. The selected inorganic powders have the characteristics of good heat resistance, low thermal conductivity, and excellent heat insulation effect. Some powders contain water of crystallization, which can cool down by losing water of crystallization at high temperatures. Other powders expand when exposed to high temperatures, which can more effectively block heat conduction. At the same time, inorganic powders are widely available and inexpensive.

[0045] 4. The manufacturing process of this flexible high-temperature resistant heat insulation sleeve is simple, and it is flexible and convenient to use. It can be applied to irregular mechanical equipment or components. Attached Figure Description

[0046] Figure 1 This is a simplified structural diagram of the flexible high-temperature resistant thermal insulation sleeve of the present invention. The numerical symbols represent:

[0047] 1—Surface

[0048] 2—Fill layer

[0049] 3—Inner layer

[0050] 4—Inorganic Fibers

[0051] 5—Inorganic particles

[0052] 6—Fixed Grid

[0053] 7—Sutures Detailed Implementation

[0054] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0055] Example 1

[0056] This embodiment provides a flexible high-temperature resistant heat-insulating sleeve and its preparation method, mainly used for high-temperature protection of hydraulic cylinders. The technical features of this embodiment are as follows:

[0057] (1) The surface structure is made of three materials: high silica cloth, polycrystalline alumina fiber cloth and high silica cloth, with a thickness of 2.5 mm. The permanent linear change is -1.5% after heating at 1000℃ for 24 hours. The average thermal conductivity (600℃) is 0.115 W / (m·K).

[0058] (2) The inner layer structure is a high silica cloth + zirconium aluminum ceramic fiber cloth layered and stitched together, with the high silica cloth placed on the side in contact with the oil cylinder; the thickness of the inner layer structure is 1.8 mm, the permanent linear change is -1.5% after heating at 1000℃ for 24 hours, and the average thermal conductivity (600℃) is 0.120 W / (m·K).

[0059] (3) The inorganic fiber is composed of three composites: alumina fiber, silicon dioxide fiber and glass fiber. The ratio of the three fibers is 3:2:1. The fiber length is 20mm and the diameter is 2μm. The permanent linear change after heating at 1000℃ for 24h is -2.0%, and the average thermal conductivity (600℃) is 0.105W / (m·K).

[0060] (4) The inorganic powder is a mixture of hydrotalcite, attapulgite, silica and hollow glass microspheres in a weight ratio of 1:1:1:1, with an average size of 20 μm and an average thermal conductivity (600℃) of 0.030 W / (m·K).

[0061] (5) The preparation steps of this flexible high-temperature resistant sheath are as follows:

[0062] a) Cut the protective sleeve shell according to the cylinder size;

[0063] b) Take the inorganic fiber described in (3) and the inorganic powder described in (4) and place them in a high-speed mixer at a weight ratio of 6:1 and mix them evenly;

[0064] c) Place the mixture from (b) evenly into the flexible shell described in (a);

[0065] d) Use high-silica sewing thread to fix the edges of the outer shell, with even stitches spaced 20mm apart horizontally and vertically to fix the outer shell into 400mm sections. 2 Square grid;

[0066] e) Roll the outer casing into a cylindrical sheath and secure it to the cylinder using adhesive fasteners.

[0067] The average thickness of the aforementioned flexible high-temperature resistant sheath is 8.5 mm.

[0068] Example 2

[0069] (1) The surface structure is made of three materials: high silica cloth, polycrystalline alumina fiber cloth and aluminum silicate fiber cloth, with a thickness of 3.5 mm. The permanent linear change is -1.5% after heating at 1000℃ for 24 hours, and the average thermal conductivity (600℃) is 0.105 W / (m·K).

[0070] (2) The inner layer structure is composed of high silica cloth and polycrystalline alumina fiber cloth. The high silica cloth is placed on the side in contact with the oil cylinder. The thickness of the inner layer structure is 2.3 mm. The permanent linear change after heating at 1000℃ for 24 hours is -1.5%. The average thermal conductivity (600℃) is 0.110 W / (m·K).

[0071] (3) The inorganic fibers are glass fiber, ceramic fiber, zirconia fiber and mullite fiber, which are four composites with a weight ratio of 1:3:2:2. The fiber length is 50mm and the diameter is 4μm. The permanent linear change after heating at 1000℃ for 24h is -1.5%, and the average thermal conductivity (600℃) is 0.105W / (m·K).

[0072] (4) The inorganic powder is a mixture of wollastonite, mica powder, diatomite, silicon dioxide and titanium dioxide in a weight ratio of 1:1:1:1:1, with an average size of 30 μm and an average thermal conductivity (600℃) of 0.030 W / (m·K).

[0073] (5) The preparation steps of this flexible high-temperature resistant sheath are as follows:

[0074] a) Cut the outer casing of the protective sleeve according to the size of the hydraulic cylinder;

[0075] b) Take the inorganic fiber described in (3) and the inorganic powder described in (4) and mix them evenly in a high-speed mixer at a weight ratio of 8:1;

[0076] c) Place the mixture from (b) evenly into the flexible shell described in (a);

[0077] d) Use high-silica sewing thread to fix the edges of the outer shell, with even stitches spaced 40mm apart horizontally and vertically to fix the outer shell into individual 1600mm sections. 2 Square grid;

[0078] e) Roll the outer casing into a cylindrical sheath and secure it to the hydraulic cylinder using metal clips.

[0079] The average thickness of the aforementioned flexible high-temperature resistant sheath is 9.7 mm.

[0080] The present invention evaluated the thermal insulation performance, high-temperature burning performance and high-temperature protection performance of the flexible sheaths prepared in Examples 1 and 2.

[0081] Thermal insulation performance evaluation method: The thermal conductivity value is measured according to the YB / T 4130-2005 Test Method for Thermal Conductivity of Refractory Materials (Water Flow Plate Method).

[0082] High-temperature calcination performance test method: According to GB / T 5988-2022 Test method for permanent linear change of refractory materials under heating, the flexible sheath is placed in a muffle furnace and calcined at 1000℃ for 24 hours, and the dimensional changes before and after calcination are measured.

[0083] High-temperature protection performance test method: After wrapping the oil cylinder with a flexible high-temperature resistant sheath, put it into a muffle furnace for heating. The temperature is set to 1000℃ and the time is 30 minutes. The temperature values ​​inside and outside the sheath are tested using thermocouples.

[0084] The test results are shown in Table 1.

[0085] Table 1 Performance test results of embodiments of the present invention

[0086] Performance parameters unit Example 1 Example 2 thermal conductivity W / (m·K) 0.053 0.039 Heating permanent line change ％ +2.6 +1.8 Internal temperature of the sheath ℃ 79 66

[0087] Comparative experiments show that the flexible sheaths prepared in Examples 1 and 2 both exhibit extremely low thermal conductivity and minimal permanent linear change upon heating, effectively protecting the cylinder temperature below 100°C in high-temperature environments. The flexible high-temperature resistant heat-insulating sheath of this invention is simple to prepare, flexible, and convenient to use, overcoming the shortcomings of existing technologies.

[0088] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and variations can be made to the details based on all the teachings disclosed, and all such changes are within the scope of protection of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. A flexible sheath, comprising a flexible outer shell and inorganic fibers and inorganic powder disposed within the shell; the flexible outer shell comprising a surface structure and an inner structure made of refractory cloth; the inorganic fibers being refractory fibers; At least one of the inorganic powders contains water of crystallization, and the inorganic powder containing water of crystallization can cool down by losing water of crystallization when heated, and / or, at least one of the inorganic powders can expand when heated and block heat conduction; the weight ratio of the inorganic fiber to the inorganic powder is 5:1 to 10:

1. The outer layer of the flexible shell is composed of a composite of three materials: high-silica cloth, polycrystalline alumina fiber cloth, and high-silica cloth. The inner layer of the flexible shell is composed of a composite of high-silica cloth and zirconium alumina ceramic fiber cloth, with the zirconium alumina ceramic fiber cloth disposed on the side in contact with the filler. The inorganic fibers are a combination of alumina fiber, silica fiber, and glass fiber in a weight ratio of 3-4:2-3:1-2. The inorganic powder is a combination of hydrotalcite, attapulgite, silica, and hollow glass microspheres in an equal weight ratio. Alternatively... The outer layer of the flexible shell is composed of a composite of three materials: high-silica cloth, polycrystalline alumina fiber cloth, and aluminosilicate fiber cloth, with the high-silica cloth located on the side away from the filler. The inner layer of the flexible shell is composed of a composite of high-silica cloth and polycrystalline alumina fiber cloth, with the polycrystalline alumina fiber cloth located on the side in contact with the filler. The inorganic fibers are a combination of glass fiber, ceramic fiber, zirconia fiber, and mullite fiber in a weight ratio of 1~2:3~4:2~3:2~3. The inorganic powder is a combination of wollastonite, mica powder, diatomaceous earth, silica, and titanium dioxide in an equal weight ratio.

2. The flexible sheath of claim 1, having one or more of the following features: (1) The permanent linear changes of the surface and inner layers of the flexible shell after heating at 1000℃ for 24 hours are both ≤-1.5%; (2) The surface structure of the flexible shell has an average thermal conductivity of 0.105 W / (m·K) to 0.115 W / (m·K) at 600℃. (3) The average thermal conductivity of the inner layer structure of the flexible shell at 600℃ is 0.110 W / (m·K)~0.120 W / (m·K). (4) The average thermal conductivity of the flexible shell at 600℃ is 0.110 W / (m·K)~0.150 W / (m·K); (5) The permanent linear change of the flexible shell after heating at 1000℃ for 24 hours is ≤-2%; (6) The surface thickness of the flexible shell is 1.5mm~3.5mm; (7) The inner layer thickness of the flexible shell is 1mm~3mm.

3. The flexible sheath of claim 1, having one or more of the following features: (1) The permanent linear change of the inorganic fiber after heating at 1000℃ for 24 hours is ≤-3%; (2) The average thermal conductivity of the inorganic fiber at 600℃ is 0.100W / (m·K)~0.150W / (m·K); (3) The length of the inorganic fiber is 10mm~200mm; (4) The diameter of the inorganic fiber is 2μm~6μm.

4. The flexible sheath according to any one of claims 1-3, having one or more of the following features: (1) The inorganic powder has a microstructure of flakes or spheres; (2) The average particle size of the inorganic powder is 30 nm to 300 μm; (3) The average thermal conductivity of the inorganic powder at 600℃ is 0.030W / (m·K)~0.110W / (m·K).

5. A method for preparing the flexible sheath according to any one of claims 1-4, comprising the following steps: (1) Cut fire-resistant cloth to the appropriate size according to the size of the mechanical equipment or components to make a flexible shell; (2) Take a certain amount of inorganic fiber and inorganic powder and mix them evenly; (3) Place the mixture from (2) evenly into the flexible shell described in (1); (4) Use fire-resistant sewing thread to fix the edges of the outer shell, and evenly place the stitches at 20mm~50mm intervals in both the horizontal and vertical directions to fix the outer shell into 400mm sections. 2 ~2500mm 2 Square grid; (5) Roll the outer shell into a cylindrical sheath and fix it to the mechanical equipment or component using fasteners.

6. The method of claim 5, wherein the fire-resistant sewing thread is a high-silica sewing thread.

7. The method of claim 5 or 6, wherein the fastener is an adhesive buckle, a metal snap fastener, a shuttle buckle, or a D-ring metal adjusting buckle.

8. The use of the flexible sheath according to any one of claims 1-4 for providing thermal insulation protection for mechanical equipment or components.

9. The use of claim 8, wherein the mechanical device or component is a hydraulic cylinder or a motor.

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