JP2018176262A - Manufacturing method of fin tube type heat exchanger and combustion device having fin tube heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a fin tube type heat exchanger which can use a pipe expansion device for a long period of a life, and improves productivity, and a combustion chamber having the fin tube type heat exchanger.SOLUTION: A manufacturing method of a fin tube type heat exchanger (51) includes a pipe expansion process for inserting a pipe expansion device (100) into a heat transmission pipe (21) which is inserted into a pipe penetration hole (20) of a heat transmission fin (2), and expanding the heat transmission pipe (21). The pipe expansion process has a first process for bringing the pipe expansion device (100) into a pipe-expanded state by expanding the heat expansion pipe (21) to a pipe expansion direction in a state that the pipe expansion device is stopped within a prescribed pipe expansion-scheduled range (22) in the heat transmission pipe (21), and makes the pipe expansion-scheduled range (22) adhere to the pipe penetration hole (20), and a second process for releasing the expansion of the pipe expansion device (100) to the pipe expansion direction, and moving the pipe expansion device (100) to a succeeding pipe expansion-scheduled range (22) in the heat transmission pipe (21). The manufacturing method repeatedly and alternately performs the first process and the second process.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method of manufacturing a finned tube heat exchanger and a combustion apparatus provided with the finned tube heat exchanger.

  As heat exchangers incorporated into water heaters, a large number of thin plate shaped heat transfer fins (3) as shown in FIG. 7 are arranged side by side with a predetermined gap, and the pipe is inserted in each heat transfer fin (3) There is a finned-tube heat exchanger which has a heat transfer tube (31) inserted into the hole (30). The peripheral edge of the through hole (30) of the heat transfer fin (3) and the outer peripheral surface of the heat transfer tube (31) are preferably in close contact in order to enhance the thermal efficiency. It is practiced to expand (31).

  For example, Patent Document 1 discloses a method of expanding a metal pipe. In this expansion method, as shown in FIG. 8, an expansion jig (4) in which a spherical main body (40) having a diameter larger than the inner diameter of the metal pipe (31) is provided at the tip of the shaft (41) In this method, the outer diameter is expanded by forcibly inserting the metal tube (31) and pushing it forward. This is a method in which diamond like carbon treatment is applied to the main body (40) of the pipe expansion jig (4), and a lubricating oil is added to force insertion into the metal pipe (31). In this method, the metal pipe (31 ) For copper tubes or aluminum tubes.

JP 2008-93713 A

  However, in the case of the heat transfer tube made of stainless steel, if the main body (40) of the expansion jig (4) is forcedly inserted into the heat transfer tube and pushed in, diamond-like carbon treatment is early even if lubricating oil is used. As a result, a large amount of frictional heat is generated and stainless steel adheres to the surface of the main body (40). If the pipe expansion jig (4) is continued to be used in this state, there is a disadvantage that the heat transfer tube (31) will be scratched, and the load for pushing the main body (40) will increase and the shaft ( 41) may be damaged. Therefore, the frequency of replacement of the pipe expansion jig (4) is high, and the work of drying and removing the lubricating oil in the heat transfer pipe (31) is also required. Therefore, the productivity of the heat exchanger is very low and the cost is also low. It could not be said that the method was high enough to be suitable for mass production.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a finned tube heat exchanger, which can use a pipe expansion device for a long life and can improve productivity. It is an object of the present invention to provide a combustion apparatus comprising a finned tube heat exchanger.

The method for manufacturing a finned tube heat exchanger according to the present invention is
A method of manufacturing a finned tube heat exchanger, comprising: a heat transfer fin; and a heat transfer tube made of aluminum or stainless steel which is inserted into a through hole provided in the heat transfer fin.
Including an expanding step of inserting a pipe expansion device into a heat transfer pipe inserted through the pipe penetration hole to expand the heat transfer pipe;
The pipe expansion step is
The diameter expansion scheduled range is the through hole insertion hole by enlarging the diameter expansion scheduled in the pipe diameter direction of the heat transfer pipe while stopping the pipe expansion device in a predetermined diameter expansion planned range in the heat transfer pipe. A first step of expanding the tube so as to be in close contact with the
A second step of moving the pipe expansion device to a next planned diameter expansion range in the heat transfer pipe in a diameter-reduced state in which the expansion of the pipe expansion device in the pipe radial direction is released;
It is a method of repeatedly and alternately executing the first step and the second step.

In this manufacturing method, the pipe expansion device can not be moved in the heat transfer pipe while maintaining the diameter expansion state. That is, since the outer peripheral surface of the pipe expansion device does not slide on the inner peripheral surface of the heat transfer pipe, stainless steel may be seized and adhered to the surface of the pipe expansion device by frictional heat even with a stainless steel heat transfer pipe. Absent. Therefore, since it is not necessary to replace the pipe expansion device frequently and also the lubricating oil is not required, the process of drying and removing the lubricating oil and the cost become unnecessary.
Further, by repeating the first step and the second step, the outer peripheral surface of the heat transfer tube can be closely adhered to the through hole of the heat transfer fin over substantially the entire length of the heat transfer tube, and brazing of the heat transfer tube and the heat transfer fin Since the rate can be increased, a heat exchanger with high thermal efficiency can be manufactured.

In the method of manufacturing the finned tube heat exchanger, preferably
The pipe expansion device is
A plurality of divided head portions which constitute a cylinder and are divided in the circumferential direction;
A core rod pushed from the end of the heat transfer tube into the open portion of the cylindrical body in the heat transfer tube;
And a conversion mechanism for converting the pushing force in the axial direction of the core rod into the movement of the divided head portion in the expansion direction of the pipe;
When the core rod is pushed in, the divided head portions move in the expanding direction, and the cylinder is expanded in diameter, and when the core rod is pulled out, the divided head portions move in the diameter reducing direction and the cylinder The thing used as a diameter reduction state is used.

  In this structure, the outer diameter of the cylindrical body constituted by the plurality of divided head portions is in the direction of expansion of the plurality of divided head portions constituting the cylindrical body, depending on the outer diameter or pushing amount of the core rod pushed from the open portion. The movement amount of can be adjusted. Thereby, the expanded tube size of the heat transfer tube can be freely adjusted. Further, by changing the shape of the divided head portion, it is possible to cope with the expansion of heat transfer tubes of various outer shapes.

Further, a combustion apparatus provided with a finned tube heat exchanger according to the present invention is
What is claimed is: 1. A combustion apparatus comprising: a finned tube heat exchanger comprising: a heat transfer fin; and a heat transfer tube made of aluminum or stainless steel which is inserted into a through hole provided in the heat transfer fin.
The heat transfer tube inserted into the tube insertion hole is expanded in the radial direction of the heat transfer tube in a state where the expansion device is stopped within a predetermined diameter expansion scheduled range in the heat transfer tube, and the diameter is increased. The pipe is expanded such that the diameter expansion scheduled range is in close contact with the through hole;
The pipe expansion device can move to the next diameter expansion scheduled range in the heat transfer pipe in a diameter-reduced state in which the expansion in the pipe radial direction has been cancelled, and the pipe diameter is again stopped in the next diameter expansion planned range. By expanding in the direction to the diameter expansion state, the next diameter expansion scheduled range is expanded so as to be in close contact with the through hole.

Further, in the combustion apparatus provided with the finned tube heat exchanger,
The pipe expansion device is
A plurality of divided head portions which constitute a cylinder and are divided in the circumferential direction;
A core rod pushed from the end of the heat transfer tube into the open portion of the cylindrical body in the heat transfer tube;
And a conversion mechanism for converting the pushing force in the axial direction of the core rod into the movement of the divided head portion in the expansion direction of the pipe;
By pushing in the core rod, the plurality of divided head parts move in the expansion direction and the cylindrical body is expanded in diameter, and by pulling out the core rod, the plurality of divided head parts move in the diameter decreasing direction It is preferable that the cylinder be in a diameter-reduced state.

  In this case, the heat transfer tube is expanded by the pipe expansion apparatus over substantially the entire length thereof to improve the adhesion between the heat transfer fin and the heat transfer tube, thereby reliably inserting the heat transfer tube through the heat transfer fin Can be fixed by brazing. Therefore, since the brazing ratio is increased, it is possible to provide a combustion apparatus provided with a heat exchanger with high thermal efficiency.

According to the method for manufacturing a finned tube heat exchanger of the present invention, the pipe expansion device can be moved to the next diameter expansion scheduled range in the heat transfer pipe without sliding, so the heat transfer pipe and the pipe expansion device In the meantime, friction heat is not generated, and even in the case of a stainless steel heat transfer tube, stainless steel does not adhere to the surface of the expansion device. Therefore, it is not necessary to replace the pipe expansion device at high frequency, and the life of the pipe expansion device can be extended. In addition, since the pipe expansion apparatus can be moved in the heat transfer pipe without the lubricating oil, the cost can be suppressed, and the process of drying and removing the lubricating oil is not necessary, and the productivity is improved.
According to the combustion apparatus provided with the finned tube heat exchanger of the present invention, the brazing ratio can be increased by improving the adhesion between the heat transfer fins and the heat transfer tubes, so a heat exchanger with high thermal efficiency can be obtained. The provided combustion device can be provided.

It is a perspective view of a heat exchanger. It is a schematic diagram of the water heater provided with the heat exchanger shown in FIG. It is explanatory drawing of the diameter-reduction state of the pipe expansion apparatus employ | adopted as the pipe expansion method of the heat exchanger tube which concerns on embodiment of this invention. It is sectional drawing of the diameter-reduction state of the pipe expansion apparatus employ | adopted as the pipe expansion method of the heat exchanger tube which concerns on embodiment of this invention. It is explanatory drawing of the diameter expansion state of the pipe expansion apparatus employ | adopted to the pipe expansion method of the heat exchanger tube which concerns on embodiment of this invention. It is sectional drawing of the diameter-expanded state of the pipe expansion apparatus employ | adopted as the pipe expansion method of the heat exchanger tube which concerns on embodiment of this invention. It is an explanatory view of a conventional heat transfer fin and a heat transfer pipe. It is explanatory drawing of the conventional pipe expansion apparatus.

The above-described embodiment of the present invention will be described in detail with reference to the attached drawings.
The heat exchanger (51) shown in FIG. 1 has thin plate-like heat transfer fins (2) for heat absorption between opposing front and rear side walls (501) (502) of the case body (5). 501) A large number of parallel arrangements are made parallel to (502).
In this specification, the outer side surface of the front side wall (501) is the front of the heat exchanger (51), and the depth direction when the case body (5) is viewed from the front side is the front and back direction, and the width direction is the left and right direction. The height direction is called the vertical direction.

  This type of heat exchanger (51) is used, for example, in a water heater corresponding to a combustion apparatus as shown in the schematic view of FIG. In this water heater, a body (53) provided with a burner (33) having a downward burning surface (33a) in the upper region, and a mixture of air and fuel gas communicated with this and driven by a motor (M) A fan case (34) provided with a fan (34a) for feeding air to the burner (33) in the housing (53) is provided in the casing (55).

The heat exchanger (51) is a sensible heat recovery type heat exchanger installed in the middle part of the body (53), and the lower heat exchanger (52) is a latent heat recovery type heat exchanger . In this water heater, the water from the water supply pipe (38) connected to the upstream side of the lower heat exchanger (52) is heated by the heat exchanger (52) with the latent heat of the combustion exhaust gas from the burner (33) The hot water heated to a predetermined set temperature is discharged from the hot water discharge pipe (39) which is heated by the sensible heat of the combustion exhaust gas in the upper heat exchanger (51) and continues to the downstream side of the heat exchanger (51). It is configured to be
The case body (5) shown in FIG. 1 constitutes a part of the case (53) and is heated from above by the combustion surface (33a) of the downward burner (33), and the combustion exhaust gas is a case It is configured to flow down from the top of the body (5).

  The heat transfer tube (21) is a stainless steel tube having a cross section of a vertically-long oval shape, and in the space of the lower half region in the case body (5), the upper and lower sides of the upper and lower sides have their centers mutually right and left They are arranged side by side in a so-called staggered fashion in which a half pitch is eccentric in the direction. Further, the heat transfer tube (21) penetrates the front and rear side walls (501) (502), and surrounds the end edges of the heat transfer tube (21) projecting outward in a case body (5). The cover part (5a) is being fixed to the side wall (501) (502) of back and front, respectively. Thus, the fluid flowing through the heat transfer tube (21) flows meandering through the cover portion (5a).

  The heat transfer fin (2) is made of a thin metal plate made of stainless steel, and the through hole (20) for inserting the heat transfer tube (21) is the same as the arrangement of the heat transfer tube (21). And, the centers are opened by burring in a zigzag form in which the lower sides and the upper sides are offset by half a pitch in the left-right direction.

  The tube penetration hole (20) is formed in a vertically-long oval shape having a size that allows the heat transfer tube (21) to be inserted substantially in contact with the heat transfer tube (21). For the improvement, it is desirable that the inner peripheral edge of the through hole (20) and the outer peripheral surface of the heat transfer tube (21) be in close contact. Therefore, the pipe expansion device (100) is inserted into the heat transfer pipe (21) to expand the diameter of the heat transfer pipe (21).

The pipe expansion apparatus (100), as shown in FIG. 3, includes a cylindrical body (1) in which a small diameter cylindrical portion (10) is extended at both ends of an elliptical cylindrical portion (11) which can be accommodated in a heat transfer pipe (21). And a pair of core rods (12) and (13) which are respectively pushed into the cylinder (1) from the open portions (10a) and (10b) of the small diameter cylindrical portions (10). The outer shape of the elliptical cylindrical portion (11) substantially matches the elliptical shape of the heat transfer tube (21).
In addition, let the heat-transfer fin (2) shown to a figure be a rectangular board in which one tube penetration insertion hole (20) was formed for convenience.

  The cylinder (1) comprises divided head portions (1a) (1b) (1c) (1d) divided into four in the circumferential direction of the cylinder (1), and these divided head portions (1a) to (1d) And the O-ring (14) as a binding member is attached to the proximal end of the small diameter cylindrical portion (10) so that the binding state is maintained. The binding member is not limited to the O-ring, but may be an elastic body such as a spring. This state is a diameter reduction state of the cylinder (1), and as shown in FIG. 3, the outer diameter thereof is slightly smaller than the inner diameter of the heat transfer tube (21), and the inside of the heat transfer tube (21) is It can be moved without sliding.

The tip of the core rod (12) (13) is a tapered shaft (12a) (13a) having a circular cross section, and both open portions (10a) (10b) are provided on both sides of the cylinder (1). A tapered surface portion (15a) (15b) having a circular cross-section which is expanded in diameter toward. Both tapered surface portions (15a, 15b) are, as shown in FIG. 4, formed in the central portion of the cylinder (1) and having a larger diameter than the minimum diameter portion of the tapered surface portions (15a, 15b) 16) communicate with each other.
As shown in the figure, at the tip of the tapered shaft portion (13a) of one of the core rods (13), a head larger in diameter than the minimum diameter portion of the tapered surface portion (15b) and smaller in diameter than the space portion (16) A locking member (13b) having a portion (130) is projected. The core rod (13) is positioned such that the head (130) is located in the space (16) of the cylinder (1) and the tapered shaft (13a) is located in the tapered surface (15b) with a gap. ) And the split head parts (1a) to (1d) and bind them with an O-ring (14).

As a first step, the core rod (13) protrudes from one open portion (10b) to the heat transfer pipe (21) assembled to the through hole insertion hole (20) of the heat transfer fin (2) and the diameter is reduced From the other open part (10a) of the cylinder (1) in a state where the cylinder (1) located in the heat transfer tube (21) is set in the predetermined diameter expansion scheduled range (22) of the heat Push the tapered shaft (12a) at the tip of the core rod (12) into the tapered surface (15a) of the cylinder (1). As the tapered shaft (12a) is pushed into the tapered surface (15a) of the cylinder (1), the cylinder (1) is pushed and the tapered shaft (13a) is also forced into the tapered surface (15b). It will be pushed down. As a result, the tapered surface portions (15a, 15b) of the cylindrical body (1) are pressed in the radial direction by the tapered shaft portions (12a, 13a) of the core rods (12, 13). This pushing force is converted to a force for moving the divided head portions (1a) to (1d) in the radial direction away from each other against the elastic return force of the O-ring (14). Thereby, a gap (S) as shown in FIG. 5 is formed between the divided head portions (1a) to (1d), and the outer diameter of the cylindrical body (1) is uniformly enlarged. This state is the diameter expansion state of the cylindrical body (1), and the diameter expansion scheduled range (22) of the heat transfer tube (21) can be expanded.
In the first step, the core rods (12) and (13) are pushed into the open portions (10a) and (10b) on both sides of the cylinder (1). The positional deviation from the planned range (22) can be suppressed.

After the completion of the first step, in the next second step, the core rods (12) and (13) are moved from the cylinder (1) in the pulling direction. Then, the pressing force in the radial direction of the cylindrical body (1) by the tapered shaft portions (12a) and (13a) of the core rods (12) and (13) is released, and the cylindrical body (1) is an O-ring (14). By the elastic return force, it returns to the diameter-reduced state of FIG. 3, FIG. At this time, the core rod (12) is pulled outward from the open portion (10a), but the core rod (13) is the head of the locking member (13b) which is made to project from the tip of the tapered shaft (13a). The core rod (13) is not pulled out from the open portion (10b) because the portion (130) is caught at the boundary between the tapered surface portion (15b) and the space portion (16). In this state, by pulling the core rod (13) in the pulling direction (the direction of the arrow in FIG. 4), the cylindrical body (1) is pulled by the head (130) while being held in the reduced diameter state. , Can be moved to the next diameter expansion scheduled range (22) in the heat transfer tube (21).
The above first step is performed again in a state where it is stopped in the next diameter expansion scheduled range (22). The next diameter expansion scheduled range (22) is a range of unexpanded pipes adjacent to the area expanded in the first step.
As described above, by alternately repeating the first step and the second step described above, the diameter of the heat transfer tube (21) can be increased in order, and the outer peripheral surface of the heat transfer tube (21) It can be closely attached to the through hole (20) of 2).

  According to this manufacturing method, since the expansion device (100) can move the inside of the heat transfer tube (21) with the diameter reduction of the cylinder (1), the cylinder (1) is a heat transfer tube (21) The friction heat caused by sliding inside does not cause the stainless steel on the inner circumferential surface of the stainless steel heat transfer tube (21) to adhere to the outer surface of the cylinder (1). Therefore, it is not necessary to replace | exchange the cylinder (1) of pipe expansion apparatus (100) frequently, and the long-term use of the pipe expansion apparatus (100) is attained. In addition, since no lubricating oil is required when moving the inside of the heat transfer pipe (21), the production cost is low, and no lubricating oil is required, so that the process of drying and removing the same is also unnecessary. Productivity of (51) is improved.

  By using the above-described pipe expansion device (100), the size and shape of the heat transfer tube (21) can be brought into close contact with the through hole (20) of the heat transfer fin (2) without creating a gap. The rate of brazing between the heat pipe (21) and the through hole (20) can be improved, and the heat transfer pipe (21) and the heat transfer fin (2) having high adhesiveness can be By adopting 51), it is possible to provide a heat exchanger (51) excellent in thermal efficiency. And the water heater as a combustion apparatus with high thermal efficiency can be provided by incorporating the said heat exchanger (51).

Moreover, since the cylinder (1) of the pipe expansion device (100) is formed by the plurality of divided head portions (1a) to (1d), the heat transfer tube (21) may be expanded equally even if it is not circular. It is advantageous in that it can be done.
In addition, although the external shape of the cylinder (1) of the pipe expansion apparatus (100) of the said embodiment was made into longitudinally long elliptical shape according to the cross-sectional shape of a heat exchanger tube (21), split head part (1a)-(1d) By changing the shape of, it is possible to correspond to heat transfer tubes having various cross-sectional shapes as well as circular shapes.
In addition, tapered shaft portions (12a) and (13a) and tapered surface portions (15a) and (15b) are provided at the tip of the core rod (12) (13) and at both open portions (10a) (10b) of the cylinder (1). Since it is formed, the degree of diameter expansion can be variously changed depending on the amount of depression of the core rods (12) (13) into the tapered surface portions (15a) (15b). Therefore, the adhesion between the heat transfer tube (21) and the heat transfer fin (2) can be improved.

In the above embodiment, the tapered shaft portions (12a) and (13a) at the ends of the core rods (12) and (13) are inserted into the open portions (10a and 10b) on both sides of the cylinder (1). However, although not shown, one end of the cylinder (1) may be temporarily fixed by a stopper or the like, and the core rod may be pushed in from the other side to expand the diameter.
In addition, although the tapered shaft portions (12a) and (13a) and the tapered surface portions (15a) and (15b) have adopted circular cross sections, this shape can be appropriately selected.
In addition, since the cylindrical body (1) can be moved in the heat transfer tube (21) in a diameter-reduced state, the planned expansion range (22) can be freely set, and the core rod (13) can be used as an axis By moving along the direction, the positional deviation of the cylindrical body (1) in the heat transfer tube (21) can be easily corrected.

  In addition, the heat exchanger (51) is, besides the above-described water heater, a condensing water heater, a heat source device of a hot water storage type hot water supply system, a water heater having a bath tracking function, a water heater having only a hot water supply function, hot water heating The present invention can be applied to heat exchangers incorporated in various combustion devices such as heat source machines and hot water heaters.

(100) .. Pipe expansion device
(20) ..
(21) · · Heat transfer tube
(22) · · Expansion range
(51) .. Heat exchanger

Claims (4)

A method of manufacturing a finned tube heat exchanger, comprising: a heat transfer fin; and a heat transfer tube made of aluminum or stainless steel which is inserted into a through hole provided in the heat transfer fin.
Including an expanding step of inserting a pipe expansion device into a heat transfer pipe inserted through the pipe penetration hole to expand the heat transfer pipe;
The pipe expansion step is
The diameter expansion scheduled range is the through hole insertion hole by enlarging the diameter expansion scheduled in the pipe diameter direction of the heat transfer pipe while stopping the pipe expansion device in a predetermined diameter expansion planned range in the heat transfer pipe. A first step of expanding the tube so as to be in close contact with the
A second step of moving the pipe expansion device to a next planned diameter expansion range in the heat transfer pipe in a diameter-reduced state in which the expansion of the pipe expansion device in the pipe radial direction is released;
A manufacturing method of a finned-tube type heat exchanger characterized by repeating and performing said 1st process and said 2nd process alternately. In the method of manufacturing a finned tube heat exchanger according to claim 1,
The pipe expansion device is
A plurality of divided head portions which constitute a cylinder and are divided in the circumferential direction;
A core rod pushed from the end of the heat transfer tube into the open portion of the cylindrical body in the heat transfer tube;
And a conversion mechanism for converting the pushing force in the axial direction of the core rod into the movement of the divided head portion in the expansion direction of the pipe;
When the core rod is pushed in, the divided head portions move in the expanding direction, and the cylinder is expanded in diameter, and when the core rod is pulled out, the divided head portions move in the diameter reducing direction and the cylinder Is a method of manufacturing a finned tube heat exchanger in which the diameter is reduced. What is claimed is: 1. A combustion apparatus comprising: a finned tube heat exchanger comprising: a heat transfer fin; and a heat transfer tube made of aluminum or stainless steel which is inserted into a through hole provided in the heat transfer fin.
The heat transfer tube inserted into the tube insertion hole is expanded in the radial direction of the heat transfer tube in a state where the expansion device is stopped within a predetermined diameter expansion scheduled range in the heat transfer tube, and the diameter is increased. The pipe is expanded such that the diameter expansion scheduled range is in close contact with the through hole;
The pipe expansion device can move to the next diameter expansion scheduled range in the heat transfer pipe in a diameter-reduced state in which the expansion in the pipe radial direction has been cancelled, and the pipe diameter is again stopped in the next diameter expansion planned range. A combustion apparatus comprising a finned tube heat exchanger having a structure in which the next diameter expansion scheduled range is expanded so as to be in close contact with the through hole by making the diameter expanded to be in the expanded state. A combustion apparatus comprising the finned tube heat exchanger according to claim 3.
The pipe expansion device is
A plurality of divided head portions which constitute a cylinder and are divided in the circumferential direction;
A core rod pushed from the end of the heat transfer tube into the open portion of the cylindrical body in the heat transfer tube;
And a conversion mechanism for converting the pushing force in the axial direction of the core rod into the movement of the divided head portion in the expansion direction of the pipe;
By pushing in the core rod, the plurality of divided head parts move in the expansion direction and the cylindrical body is expanded in diameter, and by pulling out the core rod, the plurality of divided head parts move in the diameter decreasing direction A combustion apparatus provided with a finned-tube heat exchanger in which a cylindrical body is in a diameter-reduced state.

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