JP2948283B2 - Pipe inner surface cleaning device and curved pipe inner surface cleaning method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pipe inner surface cleaning apparatus and a curved pipe inner surface cleaning method.

[Prior art] In order to remove sand, scale, and other deposits adhering to the inner surface of the tube as a base treatment for coating the inner surface of the tube, a cleaning device that sprays an abrasive onto the inner surface of the tube is used. Have been.

[Problems to be Solved by the Invention] With a conventional cleaning device, in the case of a straight pipe, it is possible to remove deposits on the inner surface of the pipe, but in the case of a curved pipe, the inside of the corner portion of the curved pipe is removed. At present, it is not possible to sufficiently remove the deposits on the inner surface, and for this reason, workers are currently using a grinder to clean.

However, in the manual operation by an operator, the polishing becomes uneven and the work efficiency is poor and the cost is increased, and the work environment is deteriorated by noise and dust, which is not preferable in terms of pollution.

In view of the above-mentioned circumstances, the present invention can efficiently and reliably perform internal cleaning of various pipes such as curved pipes, flanged pipes, T-shaped pipes, and cruciform pipes as well as straight pipes. An object of the present invention is to provide a pipe inner surface cleaning apparatus and a curved pipe inner surface cleaning method capable of maintaining an environment.

[Means for Solving the Problems] A first aspect of the present invention is to mount a closed container-like cabinet having an openable door, a swivelable cleaning table stored in the cabinet, and a pipe. A polishing cart that is fixed and moves from the outside of the cabinet to the top of the polishing table,
A gondola arranged on the opposite side of the cabinet so as to be able to approach and separate in the horizontal direction with respect to the cabinet, and a frame suspended from the gondola so as to be movable in a direction perpendicular to the horizontal direction with respect to the moving direction of the gondola, A blast tube attached to the frame so as to be vertically movable and rotatable and having a nozzle attached to a tip toward a cabinet.

According to a second aspect of the present invention, in the method for cleaning the inner surface of a curved pipe by the pipe inner surface cleaning apparatus, a polishing carriage on which a curved pipe is mounted and fixed is moved to an upper surface of a polishing table, and then one end of the curved pipe is cleaned. Aligning the opening with the nozzle for ejecting the abrasive, and inserting the nozzle into the curved pipe from one opening while ejecting the abrasive while rotating the nozzle to perform cleaning of the inner surface of the curved pipe, When the tip reaches the vicinity of the inner surface of the inside of the curved section of the curved pipe, rotate the curved pipe in the direction in which the inner side of the inside of the corner approaches the nozzle tip, and move the nozzle horizontally in the direction of approaching the inner inner surface of the curved pipe, and simultaneously advance When the nozzle arrives at or near the center of the curved pipe corner, the nozzle stops moving forward and horizontally, and stops turning the bent pipe, and then turns the bent pipe in the opposite direction to turn the bent nozzle. Water in the direction that the inner surface of the pipe approaches When the curved tube reaches the first set position by moving it backward, the turning of the curved tube and the horizontal movement of the nozzle are stopped, and when the nozzle comes out of the curved tube, the nozzle is stopped from retreating and the curved tube is turned. The present invention relates to a method for cleaning the inner surface of a curved tube, wherein the opening of the other end of the curved tube is set in the same manner as described above, and the inner surface of the curved tube is cleaned.

[Operation] A blasting truck for fixing a pipe is placed on a lapping table provided rotatably in a closed container-like cabinet having an openable and closable door, and a blast pipe having a nozzle for ejecting blasting material is placed on the blasting pipe. Perform three-dimensional movement to align the nozzle with the pipe,
By ejecting the abrasive material from the nozzle while rotating the blast pipe and inserting it into the pipe, the inner surface of the pipe can be cleaned evenly and pollution such as noise can be prevented.

In addition, while rotating the curved pipe by the cleaning table in the direction in which the inner surface of the inside of the corner of the curved pipe approaches the tip of the curved pipe insertion nozzle, insert the blast pipe horizontally while moving the nozzle in the direction to approach the inner surface of the curved pipe. Since the blasting is performed, the blasting of the inner surface of the inside of the curved pipe corner portion, which has been difficult to perform, can be uniformly performed.

[Example] An example of the present invention will be described with reference to the drawings.

1 and 2 show a pipe inner surface cleaning apparatus according to the present invention. FIG. 1 is a perspective view, and FIG. 2 is a side view showing a configuration procedure. In FIG. It is. The cabinet 1 is provided with a hood 2 on the ceiling, a door which is lifted and lowered by a lifting device 3 on one side and which is opened and closed, and a hopper 4 for collecting abrasives on a lower portion.

A cleaning table 5 is provided in the cabinet 1 so as to be able to be turned by a turning device 6.

On the rear side (opposite the door side) of the cabinet 1, a gantry 7 is installed with its longitudinal end face facing the cabinet 1, and a guide rod 8 is provided on the upper surface of the gantry 7 in the longitudinal direction. The gondola 9 is placed on the gantry 7 in a state of straddling it. Further, a suspending member 10 provided on an upper portion of the gondola 9 is loosely fitted to the guide rod 8, and is attached to the guide rod 8. The gondola 9 is moved by the gondola moving device 11 in the approaching / separating direction (the direction of the arrow a and the direction of the opposite arrow a) with respect to the cabinet 1.

The gondola moving device 11 includes a rack 12 mounted on the ceiling of the gondola 9 coaxially with the guide rod 8, a gear 13 meshing with the rack 12, and a reduction gear installed above the mount 7 and connected to the gear 13. A gear mechanism 14, and an electric motor 15 installed on the upper side of the gantry 7 and connected to the reduction gear mechanism 14,
The driving force of the electric motor 15 is transmitted to the gear 13 via the reduction gear mechanism 14, and the gondola 9 is moved in the direction of arrow a or the direction of arrow a by rotating the gear 13.

An actuator such as a cylinder may be used as the gondola moving device 11 described above.

At four corners of the bottom surface of the gondola 9, support members 16 are provided.
Is held in a direction perpendicular to the horizontal direction with respect to the moving direction.

With the upper part inserted into the gondola 9, the frame 18
The suspension member 20 is attached to the upper frame 19 of the frame body 18, and the suspension member 20 is attached to the rod 17
Frame 18 along the rod 17 and the gondola 9
Is suspended by the gondola 9 so as to be moved by the frame moving device 21 in a direction perpendicular to the horizontal direction (the direction of the arrow b or the direction of the opposite arrow b).

The frame moving device 21 includes a rack 22 mounted coaxially with the rod 17 below the upper frame 19, and the rack 22
And a motor 24 with a reduction gear mechanism that rotates the gear 23. The gear 23 is rotated by the motor 24 with the reduction gear mechanism to move the frame 18 in the direction of the arrow b or the direction of the opposite arrow b. Things that move.

An actuator such as a cylinder may be used as the frame moving device 21 described above.

A blast tube 25 arranged on the frame 18 with the nozzle 26 for ejecting the abrasive material coaxially with the guide rod 8 of the gantry 7 facing the hole 1a on the back of the cabinet 1 is shown in FIG. And an inner pipe 27 for conveying the abrasive material to the nozzle 26 as described above.
An outer tube 28 is rotatably supported concentrically on the inner side by a bearing 29.

The blast tube 25 is provided with a rotating device 30. The rotating device 30 is fitted with a gear 31 provided concentrically on an inner tube 27 of the blast tube 25 as shown in FIG. Gear 32
And a motor 33 with a reduction gear mechanism that rotates the gear 32. The motor 33 with the reduction gear mechanism rotates the gear 32 to rotate the inner tube 27 integrally with the gear 31.

The blast tube 25 as described above is suspended and held on the frame 18 via the vertical movement device 34 so as to move integrally with the frame 18 in the arrow c direction or the counter-arrow c direction as shown in FIG. A shaft 35 rotatably attached to the frame 18 via a bearing 36 in a direction coaxial with the rod 17;
The cams 37, 37 provided integrally with the shaft 35, the cam followers 38, 38 installed above the cams 37, 37, the shaft 39 connecting the cam followers 38, 38 concentrically, and the shaft 39 A holding member 40 for suspending and holding the blast tube 25 over a required length in the axial direction, and a motor 41 with a reduction gear mechanism for rotating the shaft 35
The cam 37, 37 is rotated integrally with the shaft 35 by the motor 41 with the reduction gear mechanism to move the blast tube 25 in the up and down direction (the direction of arrow d or the direction of the opposite arrow d) together with the cam followers 38, 38. It is.

An actuator such as a cylinder may be used as the above-mentioned vertical movement device.

In FIG. 4, reference numeral 42 denotes a telescopic member such as a spring disposed between a beam member 43 provided on the frame 18 and the shaft 39. The telescopic member 42 always applies a downward force to the cam followers 38, 38, and
38 makes it possible to smoothly follow the surfaces of the cams 37, 37.

On the lower side of the frame body 18 holding the blast tube 25, a gantry 44 supported on the floor surface is installed, and two rails 45 are parallel to the blast tube 25 at a required interval on the gantry 44. The push-pull device 46 moves in the same direction as the rail 45 in the direction of approaching or separating from the cabinet 1 (the direction of arrow e or the direction of opposite arrow e).

The push-pull device 46 has upper and lower surfaces of a rail 45 sandwiched between wheels 47, 48, 49 on both side surfaces.
47 is provided with an electric motor for rotating
When the push / pull device 46 is mounted on the rail 45 by rotating the forward / reverse rotation of 47, the push / pull device 46 is moved along the rail 45 in the direction of arrow e or in the opposite direction of arrow e.
It moves in the direction.

The distal end of the push-pull member 50 whose base end is connected to the push-pull device 46 and is arranged on the gantry 44 in parallel with the blast tube 25 is in a state of being inserted into the cabinet 1 from the hole 1b and facing upward. Engagement concave portions 51 are engraved, and are supported by support rollers 52 and 53 provided in the cabinet 1.
The distal end portion of the push / pull member 50 is supported so as to be in a horizontal state, and the push / pull member 50 is pushed / pulled in the arrow e direction or the counter-arrow e direction by the push / pull device 46 in a substantially horizontal state. It has become.

The cleaning table 5 is provided with a rail 54 for movably mounting the cleaning carriage 55, and the lower surface of the cleaning carriage 55 is engaged with the engagement recess 51 of the push-pull member 50. An engaging bar 56 is provided, and the trolley 55 is pushed and pulled by the push / pull member 50 by the engagement between the engaging bar 56 and the engaging concave portion 51.

On the outside of the cabinet 1 on the door side, a gantry 57 is installed, and the reversing table 58 is mounted on the gantry 57 by a reversing device 59 by 180 ° in both forward and reverse directions (arrow f direction or counter arrow f direction).
A rail 60 is provided so as to rotate, and on the upper surface of the reversing table 58, a rail 60 for movably mounting the cleaning carriage 55 is provided at the same height as the rail 54 of the cleaning table 5, and Between the polishing table 5 and the reversing table 58, a rail 61 is provided at the same height as the rail 60, and the trolley 55 is moved through the rail 61.
Can be moved from the cleaning table 5 to the reversing table 58 and vice versa.

On the side of the gantry 7, a tower 62 and a bucket elevator
63, a storage tank 64 is attached to the upper end of the tower 62, and a blast tank 65 is attached to the lower side of the storage tank 64, and one end is attached to the lower end of the blast tank 65 by a blast pipe. The other end of the flexible blast hose 66 connected to the end of the 25 opposite the nozzle 26 via a universal joint 67 is connected to the storage tank
The abrasive material stored in 64 is supplied to the blast tube 25 through the blast tank 65 and the blast hose 66 in order.

The upper end of the bucket elevator 63 has a separator 68
To the storage tank 64 and the bucket elevator 63
Is connected to the lower end of the hopper 4 through a screw conveyor 69, and the abrasive material collected in the hopper 4 is supplied to the bucket elevator 63 by the screw conveyor 69.
Is sent to the storage tank 64 after being separated by the separator 68.

 Hereinafter, the operation will be described.

The push-pull member 50 is pushed out in the direction of arrow e by the push-pull device 46 from the entrance of the cabinet 1 opened by opening the door by the lifting device 3, and the push-pull member 50 is pushed upward between the ends of the rail 60 on the reversing table 58. Is positioned with the engaging concave portion 51 facing upward.

The straight pipe 70 to be polished is appropriately fixed on the upper surface of the grinding cart 55 mounted on the rail 60 on the reversing table 58, and the reversing table 58 is rotated by 180 ° in the direction of arrow f by the reversing device 59. The grinding cart 55 is changed from the position of the solid line in FIG. 1 to the position of the virtual line.

By the 180 ° rotation of the reversing table 58 by the reversing device 59, the engaging bar 56 of the polishing cart 55 is automatically inserted into the engaging recess 51 of the push-pull member 50, and the polishing cart 55 is pushed and pulled. The member 50 is engaged with the tip.

At this time, the rail 54, the rail 61 of the cleaning table 5 and the rail 60 of the reversing table 58 are rails that are linearly connected when viewed from above.

After the trolley 55 is engaged with the push-pull member 50 as described above, the push-pull member 50 is retracted by the push-pull device 46 in the direction indicated by the arrow e to fix the straight pipe 70. 1 and 2, the door is lowered by the elevating device 3 to close the entrance of the cabinet 1, and the inside and outside of the cabinet 1 are closed. Is completely shielded.

Next, the gondola 9 is framed by the gondola moving device 11.
The nozzle 26 of the blast tube 25 is inserted into the cabinet 1 through the insertion hole 1a and moved to the outer edge of the straight tube 70 by moving the nozzle 26 together with the blast tube 25 toward the cabinet 1 together with 18 and the blast tube 25.

Further, the blast tube 25 together with the frame 18 is appropriately moved by the frame moving device 21 in a direction perpendicular to the moving direction of the gondola 9 in the horizontal plane (the direction of the arrow b or the direction of the opposite arrow b). Is moved up and down as appropriate (moving in the direction of arrow d or in the direction of opposite arrow d) so that the axis of the blast tube 25 coincides with the axis of the straight pipe 70.

After adjusting the position of the blast pipe 25 three-dimensionally as described above and aligning the axis of the blast pipe 25 with the axis of the straight pipe 70, the blasting material is blasted from the blast tank 65 through the blast hose 66.
Supply 25.

The rotating device 30 rotates the inner tube 27 of the blast tube 25 integrally with the tip nozzle 26 at a required speed, and ejects the abrasive material from the nozzle 26. In this state, the blast tube 25 is moved integrally with the gondola 9 and the frame 18 in the direction of arrow c by the gondola moving device 11 and inserted at an appropriate speed up to the center of the straight tube 70 to clean the inner surface of the straight tube 70.

When the inner surface of the straight pipe 70 is cleaned as described above, the supply of the abrasive material from the blast tank 65 to the blast tube 25 is stopped to stop the ejection of the abrasive material from the nozzle 26, and the rotating device The rotation of the inner tube 27 of the blast tube 25 by 30 is also stopped. In this state, the nozzle 26 of the blast tube 25 is moved from the straight tube 70 to the nozzle 26 of the blast tube 25 by moving the nozzle 26 of the blast tube 25 integrally with the gondola 9 and the frame 18 by the gondola moving device 11 with respect to the cabinet 1. Pull out. afterwards,
The rotating table 6 is turned by 180 ° in the direction of the arrow g or in the direction of the opposite arrow g by 180 ° to reverse the direction of the straight pipe 70, and the rotation of the inner pipe 27 of the blast pipe 25 and the Abrasive material is ejected, and nozzle 26 of blast tube 25 is straightened.
The inner surface of the straight pipe 70 is cleaned by inserting it at an appropriate speed to the center portion of 70, and after the cleaning, the ejection of the abrasive material from the nozzle 26 of the blast pipe 25 and the rotation of the inner pipe 27 of the blast pipe 25 are stopped. Straight pipe
Withdraw the nozzle 26 of the blast tube 25 from 70.

When the straight pipe 70 is long, the inner surface is cleaned twice as described above, but when the straight pipe 70 is short, the nozzle 26 of the blast pipe 25 is inserted from one end to the other end of the straight pipe 70 to directly clean it. A single sweep is performed over the entire inner surface of the tube 70.

As described above, since the inner surface of the straight pipe 70 is cleaned in the cabinet 1 isolated from the outside, it is possible to prevent the work environment from being polluted due to noise and scattering of the cleaning material, which is useful in pollution control.

Further, during the inner surface cleaning of the straight pipe 70, the straight pipe 70 to be next cleaned is placed and fixed on the spare polishing carriage 55 at the position shown by the solid line in FIG.

After the inner surface of the straight pipe 70 has been cleaned, the door of the cabinet 1 is raised by the lifting device 3 to open the entrance, and the engagement between the polishing cart 55 on the cleaning table 5 and the push-pull member 50 is confirmed. If not performed, the cleaning table 5 is appropriately turned by the turning device 6 to engage the polishing carriage 55 with the push-pull member 50.
Thereafter, the push / pull member 50 is moved by the push / pull device 46 by the arrow e.
The trolley 55 is moved from the inside of the cabinet 1 to the rail 60 of the reversing table 58 via the rail 61 as shown by the imaginary line in FIG. Next, the reversing table 58 is connected to the reversing device 59.
To move the polishing cart 55 at the position indicated by the solid line in FIG. 1 to the position indicated by the phantom line in FIG. The engaging bar 56 is inserted into the engaging concave portion 51 of the push / pull member 50 and positioned in the engaging concave portion 51 to engage the sweeping carriage 55 with the push / pull member 50. Thereafter, the inner surface of the straight pipe 70 is cleaned by the same procedure as described above.

As described above, during the inner surface cleaning of the straight pipe 70, the straight pipe 70 to be cleaned next is mounted on the spare cleaning carriage 55 and fixed, so that the cleaning operation can be continued and the cleaning operation can be performed more efficiently. Can be achieved.

On the other hand, the abrasive material ejected from the nozzle 26 of the blast tube 25 is collected by the hopper 4 on the lower side of the cabinet 1 and sent to the bucket elevator 63 by the screw conveyor 69. The abrasive material sent to the bucket elevator 63 is classified by a separator 68 into foreign matter and scale mixed therein, sent to a storage tank 64 and accumulated, and supplied to the blast tank 65 at the time of the abrasive cleaning.

Next, a case of cleaning the inner surface of the curved tube 71 will be described with reference to FIG.

The polishing cart 55 for mounting and fixing the curved pipe 71 is moved into the cabinet 1 and positioned on the polishing table 5 in the same manner as in the case of the inner surface cleaning of the straight pipe 70, and the nozzle of the blast pipe 25 is 26 is three-dimensionally moved to perform axial alignment with the one end opening 72 of the curved pipe 71, the nozzle 26 of the blast pipe 25 is rotated, and the abrasive material is ejected from the nozzle 26, and the gondola moving device 11
As a result, the nozzle 26 is moved integrally with the gondola 9 and the frame 18 in the direction of arrow c at an appropriate speed and inserted into the curved pipe 71 to a position near the inner surface 73 inside the corner. Next, the turning device 6
As a result, the curved pipe 71 is turned together with the cleaning table 5 and the cleaning carriage 55 at an appropriate speed in a direction in which the inner surface 73 inside the corner portion approaches the nozzle 26 (direction of arrow g). A direction in which the nozzle 26 approaches the inner surface of the curved tube 71 along with the rotation (the direction of the arrow b).
At the same time, the nozzle 26 is horizontally moved at an appropriate speed integrally with the frame 18 by the frame moving device 21, and the nozzle 26 is moved integrally with the gondola 9 and the frame 18 at an appropriate speed by the gondola moving device 11 in the direction of arrow c. To further advance inside the curved tube 71. When the nozzle 26 advances in the curved pipe 71 in this way and reaches the center of the corner of the curved pipe 71 or in the vicinity thereof, the nozzle 26 stops moving forward, moving horizontally and turning the curved pipe 71 (FIG. 5). The state of the virtual line), and the ejection of the abrasive material from the nozzle 26 and the rotation of the nozzle 26 also stop. Thereafter, the curved pipe 71 is swung in the opposite direction (the direction indicated by the arrow g), and the nozzle 26 is bent.
At the same time, the nozzle 26 is moved in the direction opposite to the arrow c to move backward in the direction in which the outer inner surface of the nozzle 71 approaches (the direction of the arrow b). When the curved tube 71 reaches the first set position as shown by the solid line in FIG. 5, the turning of the curved tube 71 and the horizontal movement of the nozzle 26 are stopped, and when the nozzle 26 comes out of the one end opening 72 of the curved tube 71, the nozzle 26 Retreat (movement in the direction of arrow c) is stopped.

Thereafter, the curved pipe 71 is turned integrally with the cleaning carriage 55 at an appropriate speed in the direction of the arrow g (or in the direction opposite to the arrow g) so that the other end opening 74 of the curved pipe 71 faces the nozzle 26 of the blast pipe 25, The nozzle 26 of the blast tube 25 is three-dimensionally moved to align the axis with the other end opening 74 of the curved tube 71, and the inner surface of the curved tube 71 is cleaned in the same procedure as described above.

When the turning of the curved pipe 71 and the horizontal movement of the nozzle 26 of the blast pipe 25 in the direction of the arrow b or the direction of the arrow b are performed as described above, the nozzle 26 of the blast pipe 25
Pipe that was difficult to clean
The inner surface 73 inside the corner portion 71 can be reliably cleaned.

It should be noted that the present invention is not limited to only the illustrated and described embodiments, and includes, for example, pipes other than straight pipes and curved pipes (flanged pipes,
The cleaning of the T-shaped tube, the cross tube, etc.) is optional. Of course, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the pipe inner surface cleaning apparatus of the present invention,
Since the blast tube having the nozzle for ejecting the abrasive material is made three-dimensionally movable and rotatable, it is possible to easily align the axis of the nozzle with various pipes such as straight pipes and curved pipes. The inner surface can be cleaned efficiently and evenly, and the inner surface of the various pipes such as straight pipes and curved pipes can be cleaned because the cleaning is performed using the rotatable cleaning table provided in the cabinet. It is possible to improve the working environment by coping with noise and dust generation, as well as to automate the internal cleaning of pipes. .

Further, according to the curved pipe inner surface cleaning method of the present invention, the curved pipe is turned in the direction in which the inner surface of the corner portion of the curved pipe approaches the insertion nozzle, and the nozzle is horizontally moved in the direction of approaching the inner surface of the curved pipe. In addition, the present invention has an excellent effect that the inner surface inside the curved pipe corner portion, which has been difficult to clean, can be uniformly cleaned.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a pipe inner surface cleaning apparatus of the present invention, FIG. 2 is a side view showing a configuration of the pipe inner surface cleaning apparatus of the present invention, and FIG. 3 is a pipe inner surface cleaning apparatus of the present invention. FIG. 4 is a cutaway side view showing the configuration of the blast tube, FIG. 4 is a schematic view from the cabinet side showing how to attach the blast tube to the frame in the pipe inner surface cleaning apparatus of the present invention, and FIG. It is a top view which shows the curved pipe inner surface cleaning method. In the figure, 1 is a cabinet, 5 is a cleaning table, 6 is a turning device, 7 is a gantry, 9 is a gondola, 11 is a gondola moving device,
18 is a frame, 21 is a frame moving device, 25 is a blast tube, 26 is a nozzle, 30 is a rotating device, 34 is a vertical moving device, 55 is a polishing truck,
Reference numeral 70 denotes a straight pipe, 71 denotes a curved pipe, and 73 denotes an inner surface inside a corner portion of the curved pipe 71.

Continuation of the front page (56) References JP-A-62-241668 (JP, A) JP-A-60-53463 (JP, U) JP-A-3-19568 (JP, U) JP-A-56-171160 (JP) , U) Japanese Utility Model Showa 61-188763 (JP, U) Japanese Patent Publication No. 54-25276 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24C 9/00 B24C 3/16 B08B 9/02

Claims (2)

(57) [Claims] 1. A closed container-like cabinet having an openable and closable door, a swiveling wiping table housed in the cabinet, and a tube placed and fixed to move from the outside of the cabinet to the upper surface of the wiping table. A trolley, a gondola arranged on the opposite side of the cabinet so as to be able to approach and separate from the cabinet in a horizontal direction, and a gondola suspended from the gondola in a direction perpendicular to the moving direction of the gondola. A pipe inner surface cleaning apparatus comprising: a lowered frame; and a blast tube mounted on the frame so as to be vertically movable and rotatable and having a nozzle attached to a tip toward a cabinet. 2. A method for polishing the inner surface of a curved pipe by the apparatus according to claim 1, wherein the trolley on which the curved pipe is mounted and fixed is moved to the upper surface of the lapping table, and then the one end opening of the curved pipe and the lapping table are polished. The center of the curved pipe is inserted into the curved pipe from one opening while ejecting the abrasive while rotating the nozzle, and the inside of the curved pipe is cleaned. When the tube reaches the vicinity of the inner surface of the inside of the corner portion of the pipe, the curved tube is turned in a direction in which the inner surface of the corner portion approaches the nozzle tip, and the nozzle is moved horizontally in the direction of approaching the inner surface of the curved tube, and simultaneously advanced. Stops at the center of or near the center of the curved pipe corner, stops the nozzle from moving forward and horizontally and turning the bent pipe, then turns the bent pipe in the opposite direction, and moves the nozzle outside the bent pipe. Horizontally move in the direction that the inner surface approaches Simultaneously, when the curved tube reaches the first set position, the turning of the curved tube and the horizontal movement of the nozzle are stopped, and when the nozzle comes out of the curved tube, the retraction of the nozzle is stopped, and the curved tube is turned to turn the curved tube. The inner surface of a curved pipe is polished by setting the opening at the other end of the curved pipe as described above.