JPH06270065A - Blast method for steel pipe inside surface - Google Patents

Abstract

PURPOSE:To improve blast efficiency by replenishing secondary air while turning it when a scale is removed by blowing an abrasive against a steel pipe inside surface by an action of vacuum suction of a suction beower while supplying the abrasive to an abrasive carrying pipe from a hopper tank. CONSTITUTION:In a pipe inside scale removing device, a suction blower 9 is connected through an air suction pipe 6 to one end of a steel pipe 10 held between the installing parts 4 and 5 as a material to be processed, and an abrasive carrying pipe 3 having a hopper tank 2 through a connecting port 2a is connected to the other end of the steel pipe 10. A fan 13 and an air replenishing pipe 11 are arranged on the other end of this abrasive carrying pipe 3. Since the fan 13 starts to rotate automatically when secondary air is sucked from the air replenising pipe 11 by vacuum suction of a suction blower 9 at grinding time, the secondary air is turned, and an abrasive is also turned thereby similarly, and collision with an inner wall surface of the steel pipe 10 is caused effectively, so that scale on a pipe inside surface can be removed efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blasting the inner surface of a steel pipe.

[0002]

2. Description of the Related Art Descaling of a steel pipe surface is important as one of pretreatments when surface treating a steel pipe. Blasting is commonly used to remove this scale. For example, sand blasting, shot blasting, and grit blasting are the main ones. Sand particles, shots, and grit are sprayed onto the pipe surface by high-pressure air or centrifugal force, respectively, as abrasives. The scale film is removed with high efficiency.

By the way, in order to remove the scale on the inner surface of the steel pipe, a spraying method by sand blast has been the mainstream conventionally, but recently, a negative pressure suction method (for example, Japanese Patent Laid-Open No. 60- No. 263671) has been attracting attention because it is space-saving and has excellent safety and environment. Briefly explaining this negative pressure suction type, as shown in FIG. 2, the pipe inner surface scale removing device has a hopper tank 2 storing a polishing / cleaning material 1, a polishing / cleaning material conveying pipe 3, steel pipe mounting portions 4 and 5, an air suction. A pipe 6, a cyclone separator 7, a filter 8, and a suction blower 9 are connected, and a steel pipe 10 whose inner surface is to be ground and cleaned is connected between the steel pipe mounting portions 4 and 5, and an appropriate amount of the grinding and cleaning material 1 is dropped from the hopper tank 2. While sucking with the suction blower 9.

Then, the abrasive cleaning material 1 passes through the inner surfaces of the abrasive cleaning material conveying tube 3 and the steel pipe 10 together with the secondary air sucked from the air supply pipe 11 provided on the suction side of the abrasive cleaning material conveying pipe 3. The scale on the inner surface of the steel pipe 10 is removed and collected by the cyclone separator 7, and the secondary air is cleaned by the filter 8 and discharged from the suction blower 9 to the outside.

[0005]

However, in the above-described negative pressure suction type pipe inner surface scale removing device, when the length of the steel pipe 10 becomes long, the outlet side end portion (hereinafter, referred to as the bottom portion) C of the steel pipe 10 becomes the inlet side. There is a drawback that the degree of scale removal is lower than that of the end portion (hereinafter referred to as the top portion) A and the central portion (hereinafter referred to as the middle portion) B.

This is because the wind velocity inside the pipe becomes slow near the inner wall surface of the pipe due to friction inside the pipe, and becomes faster at the central portion of the pipe, so that the cleaning and cleaning material 1 gathers in the central portion and is less likely to collide with the inner wall of the pipe. it is conceivable that. Therefore, in order to eliminate such a defect, there is also a method of enhancing the scale peeling effect by inserting the flow straightening plate 12 as shown in FIG. 3 into the bottom side C of the pipe and causing the polishing / cleaning material 1 to fly to the wall surface. ,
There is a problem that the polishing and cleaning material 1 hits the straightening vane 12 itself, resulting in severe wear, which necessitates early replacement and repair.

The present invention has been made in order to solve the above problems of the prior art, and an object of the present invention is to provide a method for blasting the inner surface of a steel pipe having a high scale removing effect on the bottom portion.

[0008]

According to the present invention, one end of a steel pipe is connected to a suction blower via an air suction pipe, and the other end is connected to an air supply pipe via a polishing / cleaning material conveying pipe. In the method of blasting the scale on the inner surface of the steel pipe by replenishing the secondary air from the nozzle by the vacuum suction action of the suction blower while supplying the cleaning medium to the cleaning medium conveying pipe, the secondary air is replenished while swirling. This is a blasting method for the inner surface of a steel pipe.

[0009]

[Operation] According to the present invention, since the secondary air sucked in vacuum from the air supply pipe is swirled more positively, it is possible to easily cause the polishing and cleaning material to collide with the inner wall surface of the pipe.
As a result, the scale on the inner surface of the steel pipe can be effectively and surely removed.

[0010]

EXAMPLE An example of the present invention will be described below with reference to FIG. As shown in the figure, in the pipe inner surface scale removing device of the present invention, one non-driven fan 13 is provided between the connection port 2a of the abrasive cleaning and conveying pipe 3 to the hopper tank 2 and the air supply pipe 11 on the suction side thereof. Installed and configured.

Therefore, when the secondary air is sucked from the air supply pipe 11 by the vacuum suction of the suction blower 9 while dropping an appropriate amount of the polishing / cleaning material 1 from the hopper tank 2, the fan 13 naturally starts to rotate. Then, the secondary air flows while swirling in the abrasive cleaning material conveying pipe 3 and the steel pipe 10. In this way, when the abrasive 1 is swirled and flows in the pipe, the steel pipe 10
It becomes easy to collide with the inner wall surface of, and the scale can be removed efficiently.

When the method of the present invention was applied to the scale removal of a heat-treated 13Cr steel pipe, the scale at the pipe end adhered thicker than at other places, but in a short time, unevenness was observed. No scale removal could be done effectively. Further, since the fan 13 does not come into contact with the abrasive material, it does not wear and therefore maintenance is unnecessary.

Although the fan 13 is used to swirl the secondary air in the above embodiment, the present invention is not limited to this. For example, a spiral guide plate is provided on the inner surface of the air supply pipe 11. Even if it does so, it is possible to obtain the same effect.

[0014]

As described above, according to the present invention,
Since the secondary air is swirled, it is possible to make the polishing and cleaning material collide with the inner wall surface of the pipe easily, and thereby it is possible to effectively remove the scale in a short time.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a main part of an embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a conventional example.

FIG. 3 is a vertical cross-sectional side view showing a main part of another conventional example.

[Explanation of symbols]

 1 Abrasive Cleaning Material 2 Hopper Tank 3 Abrasive Cleaning Material Conveying Pipe 4,5 Steel Pipe Attachment 6 Air Suction Pipe 7 Cyclone Separator 8 Filter 9 Suction Blower 10 Steel Pipe 11 Air Supply Pipe 13 Fan

Claims (1)

[Claims] 1. A steel cleaning pipe is connected to one end of a steel pipe with a suction blower via an air suction pipe, and to the other end of the steel pipe with an air supply pipe via a polishing / cleaning material conveying pipe. In the method of blasting the scale on the inner surface of the steel pipe by replenishing the secondary air from the nozzle by the vacuum suction action by the suction blower, the secondary air is replenished while swirling. Blast method.