A sealing device for a kiln feed screw

Abstract

This utility model belongs to the field of metallurgical and chemical technology, specifically relating to a sealing device for a feed screw of a reduction kiln. The sealing device includes a sealing assembly and a positioning device. The sealing assembly is sleeved on the suspended end of the screw shaft and includes packing and a gas distribution ring arranged axially along the screw shaft. The positioning device is closedly connected to the screw cylinder, and makes sealing contact with both ends and the outer periphery of the sealing assembly. The positioning device also has an injection port communicating with a through hole on the gas distribution ring. This utility model employs two sealing methods with different characteristics to complement each other, thereby extending the service life of the sealing device for the feed screw of the reduction kiln.

Description

Technical Field

[0001] This utility model belongs to the field of metallurgical and chemical technology, and specifically relates to a sealing device for a feed screw of a reduction kiln. Background Technology

[0002] The reduction kiln is a crucial piece of equipment in the process of preparing vanadium trioxide (V₂O₃). Its core function is to heat the rotary kiln shell by burning coke oven gas, and then introduce coke oven gas as a reducing agent into the shell, causing ammonium polyvanadate (APV) to be deammonened and reduced to V₂O₃ at high temperatures. The pressure of the reducing gas inside the kiln needs to be maintained at around 300 Pa to ensure that the reaction proceeds fully.

[0003] In the feeding system, APV material is fed into the kiln head via a cantilevered feeding screw device. This device consists of a screw cylinder, a screw shaft, a drive unit, and screw blades mounted on the screw shaft. The screw cylinder is mounted on a fixed frame. The screw shaft is coaxially mounted within the screw cylinder, with one end suspended and the other end connected to the drive unit, which includes a drive motor and a reducer, allowing it to rotate under the control of the drive unit to convey material to the kiln head. Because the kiln head serves as both a reduction tail gas outlet and an APV feed inlet, the feeding screw device operates in a harsh environment, operating at a high temperature of 300±50℃ for extended periods. The tail gas contains large amounts of coke oven gas, ammonia, V2O3 particles, and water vapor, which are corrosive and toxic. During material conveying, the positive pressure (300Pa) within the kiln causes a significant leakage of material and toxic gases at the screw shaft's seal, resulting in material loss and environmental pollution.

[0004] With the increasing capacity of reduction kilns and the continuously rising requirements for vanadium trioxide yield, it is necessary to correspondingly increase the heating temperature and reducing gas flow rate of the reduction kiln to further enhance capacity. This places higher demands on the sealing of the feed screw conveyor. In the feed screw sealing device, the packing is affected by many adverse factors during the operation of the screw shaft, such as vertical oscillation, radial runout, and axial movement, resulting in poor compensating resilience of the packing seal. At the same time, gaps are created on the sealing surfaces of the packing and the screw shaft due to wear, making it easy for vanadium trioxide powder to accumulate at the packing. When this powder combines with moisture in the exhaust gas, it forms clumps, further aggravating the wear of the packing and the screw shaft, ultimately causing leakage in the sealing device.

[0005] Currently, the sealing of the feed screw conveyor mainly has the following problems:

[0006] (1) Since the spiral shaft is cantilevered, its concentricity cannot be guaranteed during operation. The discharge end generates a downward component force, and the blades become conical after wear, which affects the amount of material fed and cannot guarantee the production capacity of the reduction kiln.

[0007] (2) The contact surface between the spiral shaft and the sealing packing is worn to a certain extent, and the sealing part is uneven. Vanadium trioxide powder tends to accumulate in this part, thereby accelerating the wear of the packing and causing leakage.

[0008] (3) High difficulty and cost of inspection and maintenance. During operation, the temperature inside the kiln and the radiation temperature of related devices are very high. The temperature of the screw bearing can reach about 80℃, resulting in a short service life. Once packing leakage or bearing damage occurs, it is difficult for maintenance personnel to approach for repair. The reduction kiln needs to be cooled down and shut down for a long time, which increases maintenance costs and affects the efficiency of the reduction kiln. It is not conducive to controlling the equipment failure rate.

[0009] In summary, existing technologies rarely address the sealing problem of feed screw devices, and there is an urgent need to develop a sealing device that can extend the service life of feed screw devices. Utility Model Content

[0010] In view of this, the purpose of this utility model is to provide a sealing device for the feed screw of a reduction kiln. This utility model addresses the material jetting leakage caused by the accelerated wear of the packing due to axial, radial, and horizontal movement position errors and harsh working conditions of the screw shaft of the feed screw device during operation. It mainly adopts a method of complementing each other in structure and function with two sealing forms with different characteristics to extend the service life of the feed screw device of the reduction kiln.

[0011] Specifically, the technical solution adopted by this utility model is applied to the feed screw of the reduction kiln. The feed screw of the reduction kiln includes a fixedly installed screw cylinder and a screw shaft installed in the screw cylinder and coaxial with the screw cylinder. The outer circumference of the screw shaft is provided with screw blades. One end of the screw shaft is connected to the drive device, and the other end is suspended and extends out of the screw cylinder.

[0012] A sealing device for a feed screw in a reduction kiln, as disclosed in this application, includes a sealing assembly and a positioning device. The sealing assembly is sleeved on the suspended end of the screw shaft and includes packing and a gas distribution ring that are axially contacted along the screw shaft. The positioning device is closedly connected to the screw cylinder and makes sealing contact with both ends and the outer periphery of the sealing assembly. The positioning device is also provided with an air injection port that communicates with a through hole on the gas distribution ring.

[0013] In some embodiments, the air distribution ring is located on the side of the packing near the spiral barrel.

[0014] In some embodiments, the positioning device includes a sealing cap, a sealing packing box, and two first flanges. The sealing cap is located on the side of the packing away from the auger and abuts against the end face of the packing; the sealing packing box abuts against the end face of the air distribution ring and covers the outer peripheral surface of the air distribution ring and the packing, and the sealing packing box is provided with an air injection port; the two first flanges are respectively connected to the sealing cap and the sealing packing box, and the two first flanges are connected by bolts.

[0015] In some embodiments, the air injection port is inclined, and the end of the air injection port that communicates with the through hole on the air distribution ring is closer to the spiral cylinder than the other end.

[0016] In some embodiments, the air injection port is inclined at 45° to 75° to the axis of the spiral shaft.

[0017] In some embodiments, the sealing device further includes a wear-resistant sleeve, which is fitted onto the suspended end of the spiral shaft by a limiting component, and both the sealing component and the positioning device are disposed on the outer periphery of the wear-resistant sleeve.

[0018] In some embodiments, the inner peripheral wall of the sealing cover is provided with a sealing groove, and a sealing ring is provided in the sealing groove, with the sealing ring in close contact with the wear-resistant sleeve.

[0019] In some embodiments, a limiting ring is also connected to the spiral shaft, and the limiting ring is located at the port of the spiral cylinder; a sealing gasket is provided between the limiting ring and the wear-resistant sleeve.

[0020] In some embodiments, the sealing device further includes a material separator ring, which is fixedly disposed on the outside of the spiral shaft and at the end of the spiral blades on the spiral shaft. The material separator ring extends outward in the radial direction to the inner circumferential wall of the spiral cylinder, and the axial distance between the material separator ring and the limiting stop ring is 2~4mm.

[0021] In some embodiments, the packing is graphite packing woven from reinforcing fibers and metal wires.

[0022] The beneficial effects of this invention include: The sealing device employs a combination of packing and a gas distribution ring. The packing provides the basic mechanical seal, while the gas distribution ring forms an air curtain by injecting inert gas, actively preventing the leakage of harmful gases and cooling high-temperature areas. A positioning device is used to press the sealing components together and integrates a gas channel, enhancing sealing stability. The overall design achieves dual protection through both mechanical and gas seals, effectively solving leakage problems under high temperature (300±50℃), high pressure (300Pa), and corrosive media (coal gas, ammonia, V2O3 particles) conditions, reducing material loss, improving environmental safety, and extending equipment lifespan. This invention provides stable sealing performance, extending the packing replacement cycle to once every four months, effectively solving the problem of material leakage from the feed screw of the reduction kiln, improving equipment production efficiency, reducing equipment failure rate and maintenance costs, and creating conditions for preventative maintenance of the reduction kiln. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of a sealing device for a feed screw in a reduction kiln, provided as an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a sealing device for a feed screw in a reduction kiln, provided as another embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Sealing cap; 2. Sealing ring; 3. Sealing packing box; 4. Packing; 5. Wear-resistant sleeve; 6. Air distribution ring; 7. Limiting key; 8. Sealing gasket; 9. Material separating ring; 10. Spiral shaft; 11. Spiral cylinder; 12. Spiral blade; 13. Round nut; 14. Air injection port; 15. Sealing shell; 16. First flange; 17. Second flange; 18. Limiting retaining ring. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be further described in detail below with reference to specific examples and accompanying drawings.

[0029] It should be noted that all uses of "first" and "second" in the embodiments of this utility model are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of this utility model. Subsequent embodiments will not explain this in detail.

[0030] like Figure 1As shown, the sealing device for the feed screw of a reduction kiln proposed in this utility model is applied to the feed screw of a reduction kiln. The feed screw of the reduction kiln includes a fixedly installed screw cylinder 11 and a screw shaft 10 disposed inside the screw cylinder 11 and coaxial with the screw cylinder 11. The outer periphery of the screw shaft 10 is provided with screw blades 12. One end of the screw shaft 10 is connected to a driving device (not shown in the figure), and the other end is suspended and extends out of the screw cylinder 11. The screw blades 12 are located inside the screw cylinder 11. A material channel is provided inside the screw shaft 10. When the driving device drives the screw shaft 10 to rotate, the material inside the screw cylinder 11 is pushed into the material channel by the screw blades 12, and then discharged from the suspended end of the screw shaft 10 to the kiln head. The sealing device of one embodiment of this application includes a sealing assembly and a positioning device. The sealing assembly is sleeved on the suspended end of the screw shaft 10 and includes a packing 4 and an air distribution ring 6 that are axially contacted along the screw shaft 10. The positioning device is closedly connected to the spiral cylinder 11, and the positioning device is in sealed contact with both ends of the axial direction and the outer periphery of the sealing assembly. The positioning device is provided with an air injection port 14 that communicates with the through hole on the air distribution ring 6.

[0031] This invention's sealing device employs a combination of packing 4 and a gas distribution ring 6. Packing 4 provides the basic mechanical seal, while the gas distribution ring 6 forms an air curtain by injecting inert gas, actively preventing the leakage of harmful gases and cooling high-temperature areas. A positioning device is used to seal the device to the spiral cylinder 11, and the device is also pressed against the sealing assembly and integrates a gas channel, enhancing sealing stability. The overall design achieves dual protection through both mechanical and gas seals, effectively solving leakage problems under high temperature (300±50℃), high pressure (300Pa), and corrosive media (coal gas, ammonia, V2O3 particles) conditions, reducing material loss, improving environmental safety, and extending equipment lifespan.

[0032] In some embodiments, the gas distribution ring 6 is located on the side of the packing 4 near the spiral cylinder 11, and is made of a high-temperature resistant alloy. Its ring body has through holes or gas grooves. This structure injects inert gas (such as nitrogen) from an external gas source to form a positive pressure gas curtain on the sealing surface, achieving three functions: first, it blocks the leakage of high-pressure harmful gases (coal gas, ammonia) and particulate matter (V2O3) from the kiln; second, it cools the high-temperature sealing area (300±50℃) through airflow, protecting the sealing materials such as the packing 4; and third, it uses gas flushing to prevent material accumulation and keep the sealing surface clean. The gas distribution ring 6 and the packing 4 together constitute a dual protection system of "gas seal + mechanical seal," significantly improving the sealing reliability and equipment service life under high-pressure (300Pa) conditions.

[0033] In some embodiments, the positioning device achieves efficient sealing through the synergistic action of the sealing cap 1 and the sealing packing box 3. Specifically, the positioning device includes a sealing cap 1, a sealing packing box 3, and two first flanges 16. The sealing cap 1 is located on the side of the packing 4 away from the spiral cylinder 11 and abuts against the end face of the packing 4. The sealing packing box 3 abuts against the end face of the gas distribution ring 6 and covers the outer peripheral surfaces of the gas distribution ring 6 and the packing 4. The sealing packing box 3 is provided with an injection port 14 to ensure a stable supply of inert gas to the gas distribution ring 6. The two first flanges 16 are respectively connected to the sealing cap 1 and the sealing packing box 3, and the two first flanges 16 are connected by bolts. In addition, a second flange 17 is welded to the outer periphery of the sealing packing box 3, and the second flange 17 is connected to the end face of the spiral cylinder 11 by bolts to prevent gas leakage.

[0034] In some embodiments, the gas injection port 14 is inclined, and the end of the gas injection port 14 that connects to the through hole on the gas distribution ring 6 is closer to the spiral cylinder 11 than the other end. This optimizes the airflow distribution and achieves a triple effect: First, it guides inert gas (such as nitrogen) at an inclined angle towards the sealing area of ​​the spiral shaft 10, forming a more uniform surrounding gas curtain barrier, significantly improving the barrier efficiency against high-pressure gas (300Pa) in the kiln; second, the inclined airflow can form a spiral scouring along the surface of the spiral shaft 10, effectively removing deposited V2O3 particles and preventing wear on the sealing surface; third, through the coordinated design of the airflow direction and the rotation direction of the spiral shaft 10, it reduces gas turbulence loss, making the gas seal pressure more stable, while reducing the amount of inert gas used. This structure is particularly suitable for enhancing the reliability of dynamic seals under high-temperature (300±50℃) conditions.

[0035] In some embodiments, the air injection port 14 is inclined at an angle of 45° to 75° to the axis of the spiral shaft 10. Preferably, the angle between the air injection port 14 and the axis of the spiral shaft 10 is 60° to achieve a better injection effect.

[0036] In some embodiments, the sealing device further includes a wear-resistant sleeve 5, which is fitted onto the suspended end of the spiral shaft 10 via a limiting component. Both the sealing component and the positioning device are located on the outer periphery of the wear-resistant sleeve 5 to protect the spiral shaft 10 from direct wear by high-temperature materials, extending the lifespan of the core components. Furthermore, the wear-resistant sleeve 5 is detachable for easy replacement, reducing maintenance costs. The sealing device securely mounts the wear-resistant sleeve 5 onto the suspended end of the spiral shaft 10 via a limiting component, which consists of a round nut 13 and a limiting key 7. The round nut 13 is threaded to the outer peripheral wall of the spiral shaft 10 and abuts against the end face of the wear-resistant sleeve 5, providing axial fixation. The limiting key 7 is embedded in the keyway between the wear-resistant sleeve 5 and the spiral shaft 10, preventing relative circumferential rotation. The limiting component ensures synchronous rotation of the wear-resistant sleeve 5 and the suspended end of the spiral shaft 10, preventing seal failure due to relative sliding, making it particularly suitable for harsh conditions such as 300°C high temperatures and environments containing V₂O₃ particles.

[0037] In some embodiments, a sealing groove is provided on the inner peripheral wall of the sealing cover 1, and a sealing ring 2 is disposed in the sealing groove, with the sealing ring 2 in close contact with the wear-resistant sleeve 5. Preferably, the sealing ring 2 is made of an elastic high-temperature resistant material (such as fluororubber or graphite composite material), and is embedded in the sealing groove on the inner peripheral wall of the sealing cover 1, forming a tight dynamic contact with the outer surface of the wear-resistant sleeve 5. This application adds an elastic contact seal to the mechanical seal of the packing 4, further blocking the axial leakage path of 300Pa high-pressure kiln gas and V2O3 particles. Moreover, the elastic deformation of the sealing ring 2 can absorb the radial vibration or eccentric movement of the screw shaft 10 during operation, preventing seal failure due to mechanical vibration. The sealing ring 2 and the wear-resistant sleeve 5 form a "soft-hard pair" friction pair, which reduces frictional resistance and reduces wear on the sealing ring 2, and is particularly suitable for long-term operation under high-temperature conditions of 300±50℃. This structure significantly improves the reliability and maintenance cycle of the sealing system.

[0038] In some embodiments, a limiting ring 18 is also connected to the spiral shaft 10, and the limiting ring 18 is located at the port of the spiral cylinder 11. A sealing gasket 8 is provided between the limiting ring 18 and the wear-resistant sleeve 5, which achieves axial sealing reinforcement by elastically compressing and filling the assembly gap between the components, and prevents high-pressure (300Pa) kiln gas from leaking from the mating surface between the limiting ring 18 and the wear-resistant sleeve 5.

[0039] In some embodiments, the sealing device further includes a material separator ring 9, which is fixedly sleeved on the outside of the screw shaft 10 and located at the end of the screw blades 12 on the screw shaft 10. The material separator ring 9 extends radially outward to the inner circumferential wall of the screw cylinder 11, forming a mechanical barrier to concentrate the APV material conveyed by the feed screw into the kiln head, preventing material from splashing into the sealing area. The axial distance between the material separator ring 9 and the limiting ring 18 is 2~4mm, forming a labyrinthine barrier, weakening the direct impact of 300Pa kiln pressure gas on the sealing assembly, and preventing high-temperature V2O3 particles from entering the assembly gap between the limiting ring 18 and the wear-resistant sleeve 5, preventing particle wear on the sealing surface. This design significantly reduces the risk of contamination in the sealing area and extends the service life of the device under corrosive media conditions.

[0040] In some embodiments, such as Figure 2 As shown, a sealing shell 15 is also connected to the spiral cylinder 11, and the sealing shell 15 is located on the outside of the sealing assembly and the positioning device.

[0041] In some embodiments, packing 4 is a graphite packing woven from reinforcing fibers and metal wires. Since the existing technology uses oil-impregnated graphite packing, its fatigue resistance, wear resistance, error compensation, and compression resilience are poor, and it is prone to carbonization failure. This invention selects a reinforced graphite packing composed of a mixture of reinforcing fibers and metal wires. Through the synergistic effect of the fiber reinforcement (such as carbon fiber or ceramic fiber) and the metal wire (such as stainless steel wire), the high-temperature resistance (650℃) and high-pressure load capacity (200kg / cm²) are significantly improved, avoiding the carbonization failure of traditional oil-impregnated graphite packing. The metal wire skeleton enhances fatigue resistance and wear resistance, adapting to high linear speed conditions of 13m / s. The fiber elastic network provides excellent error compensation and compression resilience, ensuring a tight seal against the sealing surface even in corrosive environments with a pH of 0-14, effectively blocking gas leakage at 300Pa kiln pressure. This design completely solves the problem of rapid aging of traditional packing under high temperature, high pressure, and corrosive media in reduction kilns.

[0042] To further understand the sealing device for the feed screw of a reduction kiln according to this utility model, the following is the assembly sequence of the device, including the following steps:

[0043] 1. The material separating ring 9 is welded to the spiral shaft 10 and is 3mm away from the end face of the limiting ring 18. This allows the positive pressure material to change from axial movement to radial movement, thereby reducing the material pressure.

[0044] 2. Fit the wear-resistant sleeve 5 onto the suspended end of the spiral shaft 10 and fix it with the limiting component. Before installing the wear-resistant sleeve 5, fit the sealing gasket 8 onto its front end.

[0045] 3. In sequence, attach the air-closing ring 6 and the packing 4 in four turns around the outer periphery of the wear-resistant sleeve 5.

[0046] 4. Connect the sealing packing box 3 to the end face of the spiral cylinder 11 through the second flange 17, then install the sealing cover 1, and then pre-tighten the sealing cover 1 and the spiral cylinder 11 through the second flange 17 and several bolt assemblies.

[0047] In summary, the sealing device for the feed screw of the reduction kiln of this invention can effectively prevent leakage of positive pressure material from the wear gap of the packing 4 seal, effectively improving the sealing effect and equipment reliability of the sealing device for the feed screw of the reduction kiln. This significantly improves the production efficiency of the reduction kiln and creates favorable conditions for safe and environmentally friendly production. The sealing device for the feed screw of the reduction kiln of this invention is a hybrid sealing structure in which multiple structures cooperate and complement each other. The packing 4 is made of reinforced graphite packing, which has the advantages of self-lubricating properties and excellent high-temperature resistance and leakage control capabilities. This type of packing has high compressibility and can effectively compensate for dimensional errors. Nitrogen gas enters the sealing packing box 3 through the injection port 14 outside the gas distribution ring 6, which not only maintains the sealing packing box 3 at a positive pressure greater than the kiln pressure, but also utilizes the cooling effect generated by the nitrogen flow to reduce the thermal radiation temperature of the screw shaft 10 in the kiln to about 38°C, thus significantly improving the service life of the sealing device for the feed screw of the reduction kiln.

[0048] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A sealing device for a feed screw of a reduction kiln, the feed screw of the reduction kiln comprising a fixedly disposed screw cylinder (11) and a screw shaft (10) disposed inside the screw cylinder (11) and coaxial with the screw cylinder (11), the outer periphery of the screw shaft (10) being provided with screw blades (12); wherein one end of the screw shaft (10) is connected to a driving device, and the other end is suspended and extends out of the screw cylinder (11), characterized in that, The sealing device includes: A sealing assembly, which is sleeved on the suspended end of the spiral shaft (10), includes a packing (4) and an air distribution ring (6) that are axially contacted along the spiral shaft (10). The positioning device is closedly connected to the spiral cylinder (11), and the positioning device is in sealed contact with the axial ends and outer periphery of the sealing assembly. The positioning device is provided with an air injection port (14) that communicates with the through hole on the air distribution ring (6).

2. The sealing device of claim 1, wherein The air distribution ring (6) is located on the side of the packing (4) close to the spiral cylinder (11).

3. The sealing device of claim 2, wherein, The positioning device includes a sealing cover (1), a sealing packing box (3), and two first flanges (16); the sealing cover (1) is located on the side of the packing (4) away from the spiral cylinder (11) and abuts against the end face of the packing (4); the sealing packing box (3) abuts against the end face of the air distribution ring (6) and covers the outer circumference of the air distribution ring (6) and the packing (4), and the sealing packing box (3) is provided with the air injection port (14); the two first flanges (16) are respectively connected to the sealing cover (1) and the sealing packing box (3), and the two first flanges (16) are connected by bolts.

4. The sealing device of claim 3, wherein The air injection port (14) is inclined, and the end of the air injection port (14) that is connected to the through hole on the air distribution ring (6) is closer to the spiral cylinder (11) than the other end.

5. The sealing device of claim 4, wherein, The air inlet (14) is inclined at 45° to 75° to the axis of the spiral shaft (10).

6. The sealed device of claim 1, wherein, It also includes a wear-resistant sleeve (5), which is fitted onto the suspended end of the spiral shaft (10) by a limiting component. The sealing component and the positioning device are both located on the outer periphery of the wear-resistant sleeve (5).

7. The sealing device of claim 6, wherein The inner circumferential wall of the sealing cover (1) is provided with a sealing groove, and a sealing ring (2) is provided in the sealing groove. The sealing ring (2) is in close contact with the wear-resistant sleeve (5).

8. The sealed device of claim 1, wherein, A limiting ring (18) is also connected to the spiral shaft (10), and the limiting ring (18) is located at the port of the spiral cylinder (11); a sealing gasket (8) is provided between the limiting ring (18) and the wear-resistant sleeve (5).

9. The sealing device of claim 8, wherein, It also includes a material separating ring (9), which is fixedly disposed on the outside of the spiral shaft (10) and at the end of the spiral blade (12) on the spiral shaft (10). The material separating ring (9) extends outward in the radial direction to the inner circumferential wall of the spiral cylinder (11). The axial distance between the material separating ring (9) and the limiting stop ring (18) is 2~4mm.

10. The sealed device of claim 1, wherein, The packing (4) is a graphite packing woven from reinforcing fibers and metal wires.

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