CN216200720U

CN216200720U - Small-bore high pressure welding gate valve

Info

Publication number: CN216200720U
Application number: CN202122761026.6U
Authority: CN
Inventors: 程强; 吴尖斌; 甘进宝; 袁永喜; 章庭; 周琦; 吴俐玲
Original assignee: Anhui Tunxi High Pressure Valve Co ltd
Current assignee: Anhui Tunxi High Pressure Valve Co ltd
Priority date: 2021-11-12
Filing date: 2021-11-12
Publication date: 2022-04-05
Anticipated expiration: 2031-11-12

Abstract

The utility model discloses a small-caliber high-pressure welding gate valve, which relates to a gate valve and comprises a valve body, wherein the outer walls of two ends of the valve body are first vertical annular walls, the inner edge of each first vertical annular wall is connected with the outer edge of a first annular inclined wall, which deviates from a valve plate in the valve body, and the outer edge of each first annular inclined wall, which is close to the valve plate in the valve body, is connected with the outer edge of a second vertical annular wall; the valve body is provided with a valve plate, and the valve body is provided with a sealing end which is an integral structure formed by a transverse cylinder and a transverse circular truncated cone; the second vertical annular wall and the corresponding first annular inclined wall enclose an accommodating space for accommodating the corresponding end closure; the butt joint method can effectively realize the butt joint of the gate valve and the small-caliber high-pressure pipe, and improves the butt joint efficiency and the butt joint quality.

Description

Small-bore high pressure welding gate valve

Technical Field

The utility model relates to a gate valve, in particular to a gate valve welded with a small-caliber high-pressure pipe.

Background

The main function of the gate valve is to cut off or connect in the medium in the pipeline. Due to the structural characteristics of the high-pressure gate valve, the sealing performance of the high-pressure gate valve is better on pipelines with higher medium pressure, and the high-pressure gate valve is widely applied to the industries of petrochemical industry, electric power, ships, pharmacy, aerospace and the like. Because the pressure is higher, the valve and the pipeline are connected and often cannot be sealed by flange bolt connection, so the valve and the pipeline are connected by welding. The demand of the gate valve in one set of oil refining device accounts for about 80% of the demand of all valves, wherein the demand of the large-caliber gate valve is not much, and most of the large-caliber gate valves adopt small-caliber welding gate valves. In recent years, with the rapid development of the petrochemical industry, the demand of small-caliber high-pressure gate valves is increasing.

Because the pressure of the pipeline is higher, the wall thickness of the pipeline is thicker, and the corresponding inner hole of the same pipeline is smaller. The inner hole of the valve used on the pipeline is smaller. The valve seat of a welded high pressure gate valve is pressed into the valve body from the end hole by a punch, so that the valve seat cannot be pressed into the valve body when the end hole diameter is small. In general, the end hole of the valve body is turned to be large, then the valve seat is pressed in, the end hole of the valve body is fully welded, and finally the end hole of the valve body is processed to be the same as the inner hole of the pipeline. After welding, the welding groove is subjected to radiographic inspection, so that a plurality of defects such as air holes, slag inclusion and the like can occur, and if the welding groove is not processed, the pipeline has hidden leakage danger. If the treatment is needed to be reworked, the welding part is dug out and welded again, and then the radiographic inspection is carried out. The welding and processing method not only wastes materials, but also has extremely low efficiency and potential safety hazard.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects of the prior art and provides a small-bore high-pressure welding gate valve so as to solve the technical problem that a small-bore pipe and the gate valve are difficult to weld in the prior art.

The utility model is realized by the following technical scheme:

a small-caliber high-pressure welding gate valve comprises a valve body, wherein the side wall of any one end of two ends of the valve body, which is far away from a valve plate in the valve body, is a first vertical annular wall, the inner edge of the first vertical annular wall is connected with the inner wall of the corresponding end part in the valve body, one side of any one end of the two ends of the valve body, which is far away from the valve plate in the valve body, is also provided with a first annular inclined wall and a second vertical annular wall, the inner edge of each first vertical annular wall is connected with the outer edge, which is far away from the valve plate in the valve body, of the corresponding first annular inclined wall, each first annular inclined wall is connected with the outer edge, which is near the valve plate in the valve body, of the corresponding end part in the valve body, the inner edge of the second vertical annular wall is connected with the inner wall of the corresponding end part in the valve body, and the outer diameter, which is far away from the valve plate in the valve body, of the first annular inclined wall, is larger than the outer diameter, which is near the outer edge of the valve plate in the valve body; the end cap is specifically an integrated structure formed by a transverse cylinder and a transverse circular truncated cone, the outer diameter of the transverse cylinder is the same as that of the second vertical annular wall, the transverse circular truncated cone which is coaxially distributed with the transverse cylinder is mounted on the side wall of the transverse cylinder, which is far away from the valve plate in the valve body, the outer diameter of the end part, close to the valve plate in the valve body, of the transverse circular truncated cone is larger than that of the end part, which is far away from the valve plate in the valve body, of the transverse circular truncated cone and is smaller than that of the transverse cylinder, and the length of the end cap in the horizontal axial direction is the same as that of the first annular inclined wall in the horizontal axial direction; the second vertical annular wall and the corresponding first annular inclined wall enclose an accommodating space for accommodating the corresponding end closure; after the valve seat is installed in the valve body, when each sealing end is arranged in the corresponding containing space, the side wall of the transverse cylinder in each sealing end, which is close to the valve plate in the valve body, is tightly attached to the second vertical annular wall in the corresponding containing space.

Furthermore, after the end caps are arranged in the corresponding containing spaces, the space between the side wall of the transverse circular truncated cone and the first annular inclined wall in the corresponding containing space is filled with a compact filling layer through surfacing welding, and the side wall of the compact filling layer, which deviates from the valve plate in the valve body, and the first vertical annular wall are located on the same vertical surface.

Furthermore, a second annular inclined wall is turned outside the whole body formed by the compact filling layer, the end part corresponding to the valve body and the corresponding sealing end, the outer diameter of the outer edge of the second annular inclined wall close to the valve plate in the valve body is larger than the outer diameter of the outer edge of the second annular inclined wall far away from the valve plate in the valve body, and the outer edge of the second annular inclined wall far away from the valve plate in the valve body is intersected with the side wall of the corresponding compact filling layer far away from the valve plate in the valve body; the distance between the outer edge of the second annular inclined wall close to the valve plate in the valve body and the valve plate in the valve body in the horizontal direction is smaller than the distance between the outer edge of the second annular inclined wall close to the valve plate in the valve body and the valve plate in the valve body in the horizontal direction.

Furthermore, the side wall of the whole body formed by the compact filling layer, the end part of the corresponding valve body and the corresponding sealing end and deviating from the valve plate in the valve body is also provided with communicating holes which are coaxially distributed with the side wall and communicated with the inner cavity of the valve body, and the inner diameter of each communicating hole is smaller than the inner diameter of the end part of the valve body and the outer diameter of the outer edge of the second annular inclined wall deviating from the valve plate.

Further, two third annular inclined walls are turned in the two end portions of the valve body, the inner diameter of the outer edge of each third annular inclined wall, which deviates from the valve plate, is larger than the outer diameter of the transverse cylinder, the inner diameter of the outer edge, which is close to the valve plate, of the corresponding valve body is the same as the inner diameter of the end portion of the corresponding valve body, and the outer edge, which deviates from the valve plate, of each third annular inclined wall is located between two vertical surfaces where the two vertical walls of the transverse cylinder are located.

Further, the taper angle of the first annular inclined wall is 60 °.

Further, the taper angle of the transverse truncated cone is 40 degrees.

Further, the width of the transverse cylinder in the horizontal direction is 1.5 mm.

Furthermore, an angle of 0.5mm is formed between the side wall of the transverse cylinder, which is away from the valve plate in the valve body, and the transverse side wall of the transverse cylinder.

Further, the distance between the inner edge and the outer edge of the first vertical annular wall is 0.3-0.5 mm.

Compared with the prior art, the utility model has the following advantages:

the small-caliber high-pressure welding gate valve provided by the utility model can effectively improve the installation efficiency of the valve seat, simultaneously improves the machining efficiency and the machining quality of the end hole of the gate valve, avoids the defect that the traditional welding quality is difficult to control, and is convenient for welding the gate valve and an external pipeline.

Drawings

FIG. 1 is a schematic structural diagram of a small-caliber high-pressure welded gate valve in which a seal end is not placed in a valve body according to an embodiment;

fig. 2 is a schematic structural diagram of an end portion of a valve body when a dense filling layer, a second annular inclined wall, a communication hole, and a third annular inclined wall are sequentially formed after a seal end is placed in the valve body in the small-caliber high-pressure welding gate valve in the embodiment.

In the figure: 1. a valve body; 2. a first vertical annular wall; 3. a first annular sloped wall; 4. a second vertical annular wall; 5. a transverse cylinder; 6. a transverse circular truncated cone; 7. a dense filling layer; 8. a second annular inclined wall; 9. a communicating hole; 10. a third annular sloped wall; 11. a valve body; 12. a valve plate; 13. a valve seat; 14. a valve stem; 15. a stuffing box; 16. a valve cover; 17. a filler layer; 18. a packing gland; 19. a drive member; 20. and (4) a sealing ring.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

With reference to fig. 1 and 2, the present embodiment provides a small-bore high-pressure welded gate valve, which includes a valve body 1, and with reference to fig. 1, the valve body 1 is specifically composed of an integrated valve body 11, a valve plate 12 disposed in the valve body 11, two valve seats 13 disposed in the valve body 11 and located at two sides of the valve plate 12 for sealing, a valve stem 14 connected to the valve plate 12 in a T-shape, a stuffing box 15 disposed outside the valve stem 14 and having a top end located in the valve body 11 and an outer bottom end located in the valve body 11, a valve cap 16 disposed outside the stuffing box 15 and having a bottom end located in the valve body 11 and an inner top end located in the valve body 11, a packing layer 17 disposed in the stuffing box 15, a packing gland 18 disposed on the valve stem 14 and having a bottom end located in the stuffing box 15 and a top end located outside the stuffing box 15, a packing press plate disposed on the valve stem 14 and having two ends tightly abutting against the packing gland 18 and connected to the valve cap 16, and a driving member 19 for driving the valve stem 14, wherein an outer wall of the top end of the valve cap 16 is connected to the valve body 11 in a spot-welded seal manner, and sealing rings 20 are arranged between the bottom end of the valve cover 16 and the inner cavity of the valve body 11 and the outer wall of the stuffing box 15, so that gaps among the valve cover 16, the inner cavity of the valve body 11 and the outer wall of the stuffing box 15 can be effectively sealed.

In order to facilitate the installation of the valve seat 13, in the embodiment, the side wall of the two ends of the valve body 11 away from the valve plate 12 is made to be a first vertical annular wall 2, the side of any end of the valve body 11 away from the inner valve plate 12 is further provided with a first annular inclined wall 3 and a second vertical annular wall 4, the outer edge of the first annular inclined wall 3 away from the valve plate 12 is connected with the inner edge of the first vertical annular wall 2, the outer edge of the first annular inclined wall 3 close to the valve plate 12 is connected with the outer edge of the second vertical annular wall 4, the inner edge of the second vertical annular wall 4 is connected with the inner wall of the end part of the corresponding valve body 11, and the outer diameter of the first annular inclined wall 3 adjacent to the valve plate 12 is greater than the outer diameter thereof facing away from the valve plate 12, a horizontal truncated cone-shaped space with a small inside and a large outside is formed, and the outer end of the valve seat 13 placed in the valve body 11 is conveniently stamped by a punch through enlarging the caliber of the outer sides of the two ends of the valve body 11, so that the valve seat 13 is conveniently installed;

secondly, in order to make the inner diameter of the outer sides of the two ends of the valve body 11 meet the connection requirement, in this embodiment, two end caps are arranged on the outer sides of the two ends of the valve body 11, and each end cap is specifically an integrated structure formed by the transverse cylinder 5 and the transverse truncated cone 6. Wherein, the external diameter of horizontal cylinder 5 is the same with 4 external diameters of the vertical annular wall of second, and the tip external diameter that horizontal round platform 6 closes on valve plate 12 is less than the external diameter of horizontal cylinder 5, and its external diameter that deviates from valve plate 12 is less than its external diameter that closes on valve plate 12, and simultaneously, the length of terminating in the horizontal axis is the same with the ascending length of first annular inclined wall 3 in the horizontal axis to on the one hand can reduce the cost of closing 11 tip of valve shaft, the on the other hand post processing of being convenient for.

After the valve body 1 is installed, when the two ends of the valve body 1 are required to be welded with an external pipeline, each sealing end is firstly placed into a containing space which is surrounded by the first annular inclined wall 3 and the second vertical annular wall 4 in the end part of the corresponding valve body 11, and at the moment, the side wall of the transverse cylinder 5 close to the valve plate 12 in the sealing end is attached to the corresponding second vertical annular wall 4. After the transverse circular truncated cone is placed, the space between the side wall of the transverse circular truncated cone 6 in each end-sealing end and the first annular inclined wall 3 in the corresponding accommodating space is tightly filled by adopting a surfacing technology, a compact filling layer 7 is formed, and in the process, the part exposed outside the transverse circular truncated cone 6 in the transverse cylinder 5 can be melted, so that compact sealing is formed, and the defect of incomplete welding can be avoided.

The side wall of the formed dense filling layer 7, which is away from the valve plate 12, is on the same vertical surface with the corresponding first vertical annular wall 2, so that the later processing is facilitated.

After adopting the closing end to seal the corresponding tip of valve shaft 11, by first annular inclined wall 3, it has second annular inclined wall 8 to correspond the whole external car that 1 tip of valve body and corresponding closing end constitute, the outer fringe external diameter that second annular inclined wall 8 deviates from valve plate 12 is less than its external diameter that closes on valve plate 12, second annular inclined wall 8 intersects with the lateral wall that corresponds the filling layer and deviates from valve plate 12 simultaneously, the distance of the outer fringe that second annular inclined wall 8 closes on valve plate 12 and valve plate 12 on the horizontal direction is less than the outer fringe that first annular inclined wall 3 closes on valve plate 12 and the distance of valve plate 12 on the horizontal direction, thereby can effectively cut tight filling layer 7, detect packing quality.

After the second annular inclined wall 8 is formed, the communicating holes 9 which are coaxially distributed and communicated with the inner cavity of the valve body 1 are turned on the side wall of the whole body formed by the dense filling layer 7, the end part of the corresponding valve body 1 and the corresponding sealing end and are communicated with the inner cavity of the valve body 12, the inner diameter of each communicating hole 9 formed at the moment is smaller than the inner diameter of the end part of the valve body 1 and the outer diameter of the outer edge of the second annular inclined wall 8, which is away from the valve plate 12, so that the connecting requirement can be conveniently met, meanwhile, the valve seat 13 can be effectively installed, the welding defect can be effectively reduced, and the welding quality is improved.

In particular, in this embodiment, in order to facilitate the post-deposition welding, the taper angle of the first annular inclined surface is 60 degrees, and the taper angle of the transverse circular truncated cone 6 is 40 degrees, so that the two angles can effectively guarantee the welding quality and effectively reduce the consumption of welding materials.

In particular, in the present embodiment, in order to completely melt the portion of the transverse cylinder 5 outside the outer edge of the transverse truncated cone 6 adjacent to the valve plate 12 during the overlay welding, the width of the transverse cylinder 5 in the horizontal direction is 1.5 mm.

In particular, in this embodiment, in order to further facilitate the complete melting of the portion of the transverse cylinder 5 located outside the outer edge of the transverse truncated cone 6 adjacent to the valve plate 12 during the overlay welding, an angle of 0.5mm is formed between the lateral wall of the transverse cylinder 5 away from the valve plate 12 in the valve body 1 and the transverse lateral wall thereof, and the distance between the inner edge and the outer edge of the first vertical annular wall 2 is 0.3-0.5 mm.

And then can effectively realize that the welding is sealed, improve welding quality.

Principle of operation

In the process of welding the valve body 1 and an external pipeline, the inner diameters of two ends of the valve body 1 are larger than the inner diameter of the pipeline to be welded under most conditions, which is not beneficial to welding, and meanwhile, if the inner diameters of two ends of the valve body 1 are the same as the inner diameter of the external pipeline, the valve seat 13 is not beneficial to installation, therefore, in the embodiment, the inner diameters of two ends of the valve body 1 are kept in conventional arrangement, the first annular inclined wall 3 and the second vertical annular wall 4 are prefabricated when the valve body 11 is prepared, or the valve body 1 is prepared when being installed, a bell mouth structure is formed, so that the valve seat 13 is convenient to install, namely, the outer wall of the outer end of the valve seat 13 is extruded from the outside to the inside of the corresponding end part in the two ends of the valve body 1 by using a punch to enable the outer wall of the outer end to expand and be connected with the inner cavity of the valve body 1; the inner diameters of two ends of the valve body 1 after the valve seat 13 is installed are still larger than the inner diameter of a target external pipeline, and the inner diameters of the two ends of the valve body 1 need to be reduced, so that the valve body is convenient to install on one hand and weld on the other hand; therefore, in the embodiment, the space enclosed by the first annular inclined wall 3 and the second vertical annular wall 4 is sealed by the sealing end, and surfacing is performed after plugging, so that the space between the outer wall of the sealed end and the first annular inclined wall 3 is filled, and a compact filling layer 7 is formed, thereby on one hand, the quality of the end part of the valve body 1 is convenient to improve, on the other hand, the compact filling layer 7, the sealed end and the end part corresponding to the valve body 1 form an integrated structure after surfacing, and the formed integrated structure is provided with the communicating holes 9 coaxially distributed with the inner cavity of the end part of the valve body 1, thereby being convenient for forming the target communicating hole 9, wherein the aperture of the communicating hole 9 is smaller than that of the inner end of the valve body 1 and is the same as the inner diameter of an external pipeline, thereby facilitating later-stage butt joint and welding; in order to facilitate the welding of the integrated structure and the small-caliber high-pressure external pipeline, in the embodiment, the second annular inclined wall 8 is turned outside the integrated structure, so that the integrated structure becomes a circular truncated cone-shaped structure and is butt-welded with the external pipeline, and the welding quality can be effectively improved.

The size of the transverse cylinder 5, the angle of the transverse truncated cone 6, the angle of the first annular inclined wall 3 and the like are limited, so that the part of the transverse cylinder 5 exposed outside the outer edge of the transverse truncated cone 6 can be effectively melted, the defect of incomplete penetration during surfacing is avoided, meanwhile, the welding amount during surfacing is effectively reduced, and the probability of generating welding defects is low; particularly, after the second annular inclined plane is formed, a third annular inclined wall 10 which is coaxially distributed with the third annular inclined wall can be turned in an inner cavity at the end part of the valve body 1, the outer diameter of the outer edge of the third annular inclined wall 10, which is close to the valve plate 12, is the same as the inner diameter of the corresponding end part, the outer diameter of the end part, which is far away from the valve plate 12, is the same as the outer diameter of the transverse cylinder 5, and the outer edge of the third annular inclined wall 10, which is far away from the valve plate 12, is positioned between vertical surfaces of two vertical walls of the transverse cylinder 5, namely, a part of the transverse cylinder 5 is cut off, so that the part, which is positioned outside the transverse circular truncated cone 6, of the transverse cylinder 5 is prevented from being completely melted, and therefore, on one hand, the inner cavity of the valve body 1 can be smoothly excessive, and on the other hand, the defects can be avoided.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A small-caliber high-pressure welding gate valve comprises a valve body, wherein the side wall of any one of two ends of the valve body, which is far away from a valve plate in the valve body, is a first vertical annular wall, the inner edge of the first vertical annular wall is connected with the inner wall of the corresponding end part in the valve body, it is characterized in that one side of any one end of the two ends of the valve body, which is far away from the valve plate in the valve body, is also provided with a first annular inclined wall and a second vertical annular wall, the inner edge of each first vertical annular wall is connected with the outer edge of the corresponding first annular inclined wall, which is far away from the valve plate in the valve body, the outer edge of each first annular inclined wall, which is close to the valve plate in the valve body, is connected with the outer edge of the corresponding second vertical annular wall, the inner edge of the second vertical annular wall is connected with the inner wall of the corresponding end part in the valve body, and the outer diameter of the outer edge of the first annular inclined wall, which deviates from the valve plate in the valve body, is larger than that of the outer edge of the first annular inclined wall, which is close to the valve plate in the valve body; the end cap is specifically an integrated structure formed by a transverse cylinder and a transverse circular truncated cone, the outer diameter of the transverse cylinder is the same as that of the second vertical annular wall, the transverse circular truncated cone which is coaxially distributed with the transverse cylinder is mounted on the side wall of the transverse cylinder, which is far away from the valve plate in the valve body, the outer diameter of the end part, close to the valve plate in the valve body, of the transverse circular truncated cone is larger than that of the end part, which is far away from the valve plate in the valve body, of the transverse circular truncated cone and is smaller than that of the transverse cylinder, and the length of the end cap in the horizontal axial direction is the same as that of the first annular inclined wall in the horizontal axial direction; the second vertical annular wall and the corresponding first annular inclined wall enclose an accommodating space for accommodating the corresponding end closure; after the valve seat is installed in the valve body, when each sealing end is arranged in the corresponding containing space, the side wall of the transverse cylinder in each sealing end, which is close to the valve plate in the valve body, is tightly attached to the second vertical annular wall in the corresponding containing space.

2. The small-caliber high-pressure welded gate valve according to claim 1, wherein after the end caps are arranged in the corresponding accommodating spaces, the space between the side wall of the transverse truncated cone in each end cap and the first annular inclined wall in the corresponding accommodating space is filled with a dense filling layer through surfacing welding, and the side wall of the dense filling layer, which is away from the valve plate in the valve body, is on the same vertical plane as the first vertical annular wall.

3. The small-caliber high-pressure welding gate valve according to claim 2, wherein the whole body formed by the dense filling layer, the end part of the corresponding valve body and the corresponding end cap is externally lathed with a second annular inclined wall, the outer diameter of the outer edge of the second annular inclined wall close to the valve plate in the valve body is larger than the outer diameter of the outer edge of the second annular inclined wall far away from the valve plate in the valve body, and the outer edge of the second annular inclined wall far away from the valve plate in the valve body is intersected with the side wall of the corresponding dense filling layer far away from the valve plate in the valve body; the distance between the outer edge of the second annular inclined wall close to the valve plate in the valve body and the valve plate in the valve body in the horizontal direction is smaller than the distance between the outer edge of the second annular inclined wall close to the valve plate in the valve body and the valve plate in the valve body in the horizontal direction.

4. A small-caliber high-pressure welding gate valve according to claim 3, characterized in that the side wall of the whole body formed by the compact filling layer, the end part of the corresponding valve body and the corresponding sealing end, which is far away from the valve plate in the valve body, is also provided with communicating holes which are coaxially distributed with the side wall and are communicated with the inner cavity of the valve body, and the inner diameter of each communicating hole is smaller than the inner diameter of the end part of the valve body and the outer diameter of the outer edge of the second annular inclined wall, which is far away from the valve plate.

5. A small-bore high-pressure welded gate valve according to claim 4, characterized in that two third annular inclined walls are further turned in both ends of the valve body, the inner diameter of the outer edge of the third annular inclined wall facing away from the valve plate is larger than the outer diameter of the transverse cylinder, the inner diameter of the outer edge of the third annular inclined wall adjacent to the valve plate is the same as the inner diameter of the end of the corresponding valve body, and the outer edge of the third annular inclined wall facing away from the valve plate is located between two vertical surfaces where the two vertical walls of the transverse cylinder are located.

6. A small bore high pressure welding gate valve according to claim 5, characterized in that the taper angle of said first annular inclined wall is 60 °.

7. A small bore high pressure welded gate valve according to claim 6, characterized in that the taper angle of the transverse truncated cone is 40 degrees.

8. A small bore high pressure welding gate valve according to claim 7, characterized in that the width of the transverse cylinder in the horizontal direction is 1.5 mm.

9. A small bore high pressure welded gate valve according to claim 8, wherein the lateral wall of the transverse cylinder facing away from the valve plate in the valve body is chamfered at an angle of 0.5mm to the lateral wall thereof.

10. A small bore high pressure welded gate valve according to claim 9, wherein the distance between the inner and outer edges of the first vertical annular wall is 0.3-0.5 mm.