JPH0119954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning the inner surface of a bent pipe such as a U-shaped pipe.

U-shaped tubes are widely used in heat exchangers, chemical pipelines, etc., but it is extremely difficult to coat the inner surface of the tube or polish the inner surface of the tube by a physical method to remove deposits. Therefore, in the past, chemical treatment agents were exclusively used to polish the inner surface of the U-shaped tube.

As shown in FIG. 2, the applicant has provided a rotating plate 10 between the abrasive grain supply pipe 6 and the injection nozzle 5, and rotates the compressed air containing the abrasive grains to the nozzle 5. We have previously proposed a device that cleans the inner surface of the pipe by force-feeding it into the straight pipe 7 to be treated (Japanese Patent Publication No. 16029/1983).

According to the above device, since the abrasive particles are jetted from the injection nozzle while rotating, the abrasive particles do not pass through even at the entrance of the pipe 7 to be treated, and the advantage is that the abrasive particles can be uniformly polished without unevenness. It was hot.

However, the compressed air flow to which rotational force is applied by the rotating plate 10 is constricted by the nozzle 5, and the moment it is ejected from the nozzle 5, the volume expands to atmospheric pressure and the flow velocity is increased by the expansion factor. Therefore, the rotation pitch of the compressed air ends up being longer than the twist pitch of the rotation plate 10. For example, compressed air is 5 atmospheres, rotating plate 10
If the torsion pitch of the nozzle is 30cm, the swirling pitch of the airflow ejected from the nozzle will extend to 150cm, and the swirling effect will be low. If the pipe 7 to be treated is straight, there is no problem even if the swirling pitch of the compressed air flow containing the abrasive particles is extended.

However, when the above method is applied to polishing a pipe that is bent in the middle, such as the U-shaped pipe shown in FIG. There was a problem in that the collision caused a deep hole in the surface, and if it was a thin-walled pipe, it would break.

On the other hand, since the amount of abrasive particles passing through the surface 71 with a larger curvature on the inner surface of the bent portion becomes incomplete, the inner surface of the bent pipe cannot be treated using a rotating nozzle. Nakatsuta.

In the present invention, the abrasive particles, which are being sped up immediately after being ejected from the nozzle, are rotated in a short rotation pitch and injected onto the pipe to be treated, thereby swirling them along the inner surface of the curved pipe and making the inner surface smooth. , the purpose is to grind without creating excess or deficiency.

The present invention converts the abrasive air flow that is ejected from the injection nozzle 5 and expands to atmospheric pressure into a short swirl flow with a swirl pitch using a swirl plate, thereby swirling the abrasive grains and The abrasive particles flow through the bent portion of the bent pipe almost equally regardless of the inner or outer circumference of the bent portion, and the abrasive grains are thoroughly polished.

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 1 shows a condition in which the pipe 7 to be processed bent into a U-shape can be polished, one end of the pipe 7 to be processed is connected to the abrasive grain supply pipe 6 via the base 2, and the other end is They are each removably connected to the abrasive particle collection housing 8.

The cap 2 is made by connecting two long and short receiving tubes 3 and 4 on the same straight line, and the long receiving tube 3 and the short receiving tube 4
An injection nozzle 5 is provided between the two.

The injection nozzle 5 connects the threaded portion 51 at the base end to the short receiving tube 4.
The nozzle portion at the tip protrudes into the long receiving tube 3.

A stepped support surface 3 is provided at both ends of the inner hole of the mouthpiece 2 to connect the pipe to be treated 7 and the abrasive grain feed pipe 6.
1 and 41 are formed around each support surface 31 and 4.
1 is fitted with packings 32 and 42 that serve as contact surfaces for the feed pipe 6 and the pipe to be treated 7.

Inside the long receiving tube 3 are the tip of the nozzle 5 and the support surface 31.
The rotating plate 1 is press-fitted between the two.

The rotating plate 1 is made of a material with excellent wear resistance such as cemented carbide, has the shape of a belt-shaped plate twisted about two times, and has a total length of about 30 cm.

One end of the pipe to be treated 7 is fitted into the elongated receiving tube 3 of the base 2, and the other end is communicated with the abrasive particle collection casing 8.

The abrasive grain feed pipe 6 is connected to the short receiving pipe 4 of the mouthpiece 2.

In the above state, when compressed air containing abrasive particles is fed from the feed pipe 6 into the nozzle 2, the compressed air is throttled by the nozzle 5 and the air and the abrasive particles are stirred and mixed.

As soon as the abrasive airflow is ejected from the nozzle 5, the mouthpiece 2 is open to atmospheric pressure, so the airflow rapidly expands and increases the flow velocity. is converted into rotational energy of the airflow, resulting in a rotating airflow that rapidly rotates with a turning pitch approximately equal to the twisting pitch of the turning plate (approximately 15 cm), and the straight energy is considerably reduced.

In a U-shaped tube, there is almost no airflow component that travels straight through the center of the tube, and the cleaning airflow is concentrated on the inner peripheral surface of the pipe due to centrifugal force and flows along the inner surface of the pipe by swirling. Even in the curved portion 7a of the pipe to be treated, the abrasive grains do not concentrate and collide with the outer circumference side surface 70 as in the conventional case, and instead of colliding with either the outer circumference side surface 70 or the inner circumference side surface 71. This means that the parts can be polished evenly just like any other straight surface.

Note that if a conventional rotating plate 1 is also provided in the pipe between the feed pipe 6 and the injection nozzle 5, the nozzle 5
A swirling flow of compressed air is injected from the nozzle, and this hits the swirling plate 1 on the downstream side of the nozzle and is forced to rotate again, so a powerful swirling flow is generated and the cleaning effect can be further enhanced. .

Furthermore, the flow velocity of the abrasive particles can be increased by providing a compressed air pipe 9 obliquely in the base 2 as shown by the two-dot chain line in FIG. 1 to supply compressed air.

The compressed air pipe 9 is installed with the outlet 91 tilted toward the tip of the nozzle 5 in the base 2 and facing the connection direction of the base 2 so as not to run against the direction of rotation of the compressed air containing the abrasive particles. Therefore, the flow velocity of the abrasive particles passing through the rotating plate 1 is increased by the compressed air, and the cleaning effect is improved.

In the present invention, as described above, the high-speed abrasive airflow that is ejected from the nozzle and is expanding to atmospheric pressure converts the expansion force into rotational energy by the rotating plate 1, and the straight velocity component can be suppressed to a small value, so that the abrasive particles The rotation pitch of the rotating plate is almost maintained, and the compressed air passes through the pipe 9 to be treated and is evenly applied to the inner and outer peripheral surfaces of the bent pipe due to the centrifugal force caused by the swirling of the pipe. It has an excellent effect of cleaning just the right amount.

It goes without saying that the present invention is not limited to the above configuration, and that various modifications can be made within the technical scope of the claims.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the device, and FIG. 2 is a sectional view of a conventional example. 1... Swivel plate, 2... Base, 5... Spray nozzle.

Claims (1)

[Claims] 1 Connect the abrasive grain feed pipe 6 to the upstream end of the nozzle 5 and the nozzle 2 which has the rotating plate 1 on the downstream side of the nozzle, and apply one end of the curved pipe to be polished to the downstream end of the nozzle 2. , the compressed air stream containing the abrasive particles ejected from the nozzle and expanding to atmospheric pressure is passed through a passage equipped with a rotating plate, converting the expansion force into rotational energy of the air stream and converting the linear velocity component into A small high-speed swirling airflow is created, and this swirling flow is caused to flow into the bent pipe, and the cleaning airflow is passed through the bent pipe while swirling, thereby almost uniformly polishing the inner and outer surfaces of the inner surface of the bent pipe. A method for cleaning a bent pipe, characterized by: