JP7158305B2 - Pipe outer surface coating method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pipe outer surface coating method and apparatus for efficiently coating the outer surface of a pipe, for example, a metal pipe such as a ductile cast iron pipe.

Conventionally, the outer surface of a ductile cast iron pipe has been coated for the purpose of anti-corrosion and the like, and for the coating, an air spray, an airless spray, or the like is used. An example of the coating method (apparatus) will be explained with reference to FIG. There is a nozzle tip 1a having an elliptical atomization type discharge pattern P (see FIG. 3) so that the longitudinal direction of the discharge pattern P is the same as the pipe axial direction o of the pipe A. As shown in FIG.
In this coating method, while the tube A is supported by rollers 2 or the like and rotated about the tube axis o, or both ends of the tube A are supported and rotated about the tube axis o, coating is performed by a reciprocating device. The gun 1 is moved one way or reciprocally in the direction of the tube axis o for coating, or the coating gun 1 is fixed and the tube A is moved in the direction of the tube axis o for coating.

In this coating method, when coating is performed from directly above the tube A, the paint particles (hereinafter also simply referred to as "paint") b emitted from the nozzle tip 1a of the coating gun 1 reach the tube A before the tube A rotates. Since the paint particles b have a range (largeness and smallness) in particle diameter due to the air flow generated by the and particles b that do not reach tube A.
Particles b that bounce off or do not reach and adhere to tube A receive the flow of air a due to rotation of the tube and scatter without adhering to the outer surface of tube A. This scattering also deteriorates the coating efficiency.
From the above, conventionally, only about 40 to 80% of the atomized paint particles b adhere to the object (pipe) A to be coated.

The uncoated paint particles b scatter in the air or adhere to surrounding facilities. Its scattering leads to air pollution and water pollution, and its adhesion leads to industrial waste due to the unusability of the adhered substances. That is, it leads to high environmental costs.

Under such circumstances, the applicant of the present application tilted the spraying direction of the paint b from directly above the tube to the front side in the direction of rotation of the tube, and caused the ejected paint particles b to adhere from the front side of the outer surface of the tube directly above, and rotate the tube. We proposed a method in which the paint moves from the outer surface directly above to the front side along the air flow of the air, and the paint is applied by its own weight (gravity) in the meantime without scattering. As a result, the time and distance that the paint particles b face the outer surface of the pipe are increased, and the paint particles b are more likely to adhere to the outer surface of the pipe, improving the coating efficiency (Patent Document 1, claim 1, paragraph 0006, FIG. 1, Figure 2).

In addition, air is blown toward the outer surface of the tube A from the tip of the tube A in the direction of rotation from the spraying position of the paint b. We also proposed a method to prevent As a result, the movement of the paint particles b slows down, the time spent facing the outer surface of the pipe increases, the paint particles b easily adhere to the outer surface of the pipe, and the coating efficiency improves (claim 3 of Patent Document 1, FIG. 3). ~ Figure 5).
Furthermore, a spray gun is provided at the top of the double cone-shaped hood to spray the paint into the inner hood and to send air between the inner and outer hoods to form an air curtain around the sprayed paint. A proposal has also been made to prevent the paint b from scattering by means of an air curtain (Patent Document 2, FIG. 1, etc.).

JP-A-2003-265990 JP-A-51-97643

The method of tilting the spraying direction of the paint b from directly above the pipe to the front side in the pipe rotation direction, or blowing air from the spraying position of the paint to the outer surface of the pipe from the front side of the pipe in the rotation direction, is less effective than the conventional method. Although the adhesion efficiency was improved, the degree of uncoated paint particles b scattering in the air or water or adhering to surrounding facilities was not sufficiently reduced. In addition, it is necessary to adjust the spray angle of the paint b and the air for each change in the diameter of the pipe (for each nominal diameter), which is complicated.

In the case of an air curtain with a hood, the air a is blown against the pipe A from the entire inner surface of the hood, so as shown in FIG. This flow shortens the length of the discharge pattern of the paint b in the tube axial direction, and as shown in FIG. or For this reason, there is a possibility that a desired discharge pattern cannot be obtained and smooth coating cannot be performed.
In addition, when the object to be coated has various diameters, such as the pipe A, the size and shape of the feed must be changed according to the diameter, which lacks versatility.

Under the above circumstances, an object of the present invention is to improve the coating efficiency in coating the outer peripheral surface of a pipe.

In order to achieve the above object, the present invention forms air curtains of air discharged from separate air guns on both sides of the pipe in the paint discharge pattern in the diameter direction.
With this configuration, air curtains are not formed at both ends of the paint discharge pattern in the pipe axis direction, so that when the paint discharge pattern moves in the pipe axis direction, the air curtains do not interfere, and the outer surface of the metal pipe can be coated. can be done efficiently.

Specifically, in the method of coating by spraying paint onto the outer surface of a pipe that rotates about the tube axis, the outer surface of the pipe is configured to provide air curtains of air discharged from separate air guns on both sides of the pipe in the diameter direction of the paint discharge pattern. I adopted the painting method to .
In this configuration, it is preferable that the air discharged from the air gun for forming the air curtain is blown in the tangential direction of the outer periphery of the pipe. At this time, the paint discharge direction is perpendicular to the pipe axis, and the discharge direction of the air discharged from the air gun can be inclined from 0 to 20 degrees toward the pipe axis side with respect to the paint discharge direction.
Further, if the direction of air discharged from the air gun is made variable in the radial direction of the tube with respect to the direction of paint discharge,
It is possible to adapt to changes in the discharge direction of the paint, and by adjusting the discharge direction, it is possible to change the distance between the two air curtains so as to correspond to changes in the diameter of pipes of various diameters.
Further, the paint discharge pattern can be an oblong atomization type elongated in the tube axis direction. This oblong atomization type is effective for coating the outer surface of a straight pipe.

Apparatus for carrying out the above coating method may employ various configurations. For example, a coating gun for spraying coating material onto the outer surface of the rotating tube and air curtains on both sides of the coating material discharge pattern in the diameter direction of the tube may be employed. It can be configured with separate air guns to form. At this time, the air gun can change the discharge direction of the discharged air in the radial direction of the pipe with respect to the paint discharge direction.

Since the present invention is constructed as described above, the air curtain does not interfere when the paint discharge pattern shifts in the axial direction of the pipe, and the outer surface of metal pipes of various diameters such as ductile cast iron pipes can be efficiently coated. It can be carried out.

1 is a schematic front view of an embodiment of the method (apparatus) for coating the outer surface of a pipe according to the present invention; FIG. Schematic left side view of the same embodiment Explanatory drawing of the paint ejection pattern in the same embodiment Relationship chart of transfer efficiency with respect to changes in air angle θ, air pressure, etc. Action diagram of conventional example

An embodiment of the method (apparatus) for coating the outer surface of a pipe according to the present invention is shown in FIGS. is installed through the frame F. The coating gun 1 has a nozzle tip 1a forming an oval atomizing discharge pattern P on the outer surface of a tube A, as shown in FIG. The shape of the ejection pattern P is appropriately changed by changing the shape of the ejection port of the nozzle chip 1a.

The ductile tube A is supported by rollers 2 so that the longitudinal direction of the discharge pattern P is in the same direction as the direction of the tube axis o of the tube A. By rotating one of the rollers 2, the ductile tube A rotates around the tube axis o ( rotate).
As shown in FIGS. 1 and 2, the frame F is positioned above the pipe A so as to be orthogonal to its pipe axis o, and is moved one way or reciprocatingly in the direction of the pipe axis by a reciprocating device (not shown). A paint gun 1 is provided on the frame F via a support rod 4, and a paint pipe 5 is connected to the paint gun 1. - 特許庁The coating gun 1 can change its discharge direction around the axis of the support rod 4 (in the radial direction of the tube A).

The frame F is provided with support pipes 6 in the direction of the tube axis o on both sides of the tube A (on both sides of the tube A in the diametrical direction). set in the direction. Pressurized air (air) a is sent to the support pipe 6 . The distance between the two support pipes 6, 6, the number of the support pipes 6 of the air gun 3 in the longitudinal direction (the direction of the tube axis o), and the shape of the discharge ports are such that the discharged air a is an oblong atomization type discharge pattern in FIG. The air curtain S is appropriately set by experiment or the like so that the air curtain S is formed so as to have a width including the distance L between both ends of P and to sandwich both side edges of the same pattern P on the outer periphery of the pipe A (see FIG. 3). . In this embodiment, four air guns 3 are provided in the pipe axis direction.

The air gun 3 has a variable discharge direction around the axis of the support pipe 6 (in the radial direction of the tube A) (the arrow direction in FIG. 2). The variableness is achieved by making the support pipe 6 freely rotatable and fixed about its axis with respect to the frame F, or by making the attachment portion of the air gun 3 to the support pipe 6 variable by a universal joint or the like.
If the discharge direction of the air gun 3 is made variable in this manner, the width between the discharge direction of the coating gun 1 and the air curtain S, which is the discharge direction of the air gun 3, can be changed, so that pipes A with various diameters can be handled. can. At this time, if the discharge direction of the coating gun 1 is also variable, the position and shape of the paint b applied to the tube A and the position, width and size of the air curtain S can be varied. A can respond more accurately.

The coating apparatus of this embodiment is configured as described above. In a state in which the tube A is supported by the rollers 2 and rotated about the tube axis o, the coating gun 1 discharges the coating material b onto the outer surface of the tube A. , an oblong atomizing discharge pattern P whose long axis is in the direction of the tube axis o is formed, and air curtains S are formed on both sides of the oblong atomizing discharge pattern P by discharging air a from the air guns 3 on both sides thereof. to form That is, the air curtains S are formed only on both sides of the oblong atomization type discharge pattern P, and the air curtains S are not formed on both ends (both ends in the tube axis o direction).

The spraying action of the coating material b from the coating gun 1 is performed by moving the coating gun 1 and the air gun 3 from one end (e.g., socket side) of the tube A to the other end (e.g., insertion side) by a reciprocating device along the tube axis o. The entire outer circumference of the pipe A is coated by moving it one way or reciprocating in the direction. At this time, the paint particles b ejected from the nozzle tip 1a of the paint gun 1 are prevented from deviating from the discharge pattern P by the air curtains S, S on both sides, and bounce off or reach the tube A. Even if it does not, it will be guided into the ejection pattern P by the air curtain S. Therefore, the paint b is not wasted, and efficient painting can be performed.

Even if the diameter of the pipe A differs, if the width of the discharge pattern P does not exceed the diameter of the pipe A, the outer surface of the pipe A can be coated. 3, it is easy to ensure that the discharged air a sandwiches both side edges of the oblong atomizing discharge pattern P on the outer circumference of the tube A. As shown in FIG.

In this embodiment, under the following conditions, the discharge direction of the discharged air a of the air gun 3 is inclined inwardly with respect to the direction perpendicular to the pipe axis o (toward the pipe axis o with respect to the discharge direction of the paint b) at an angle θ (See FIG. 2) Experimental Examples 1 to 6 were performed, and the results are shown in FIG.
Note ・Painting gun 1: Airless spray gun ・Paint b: Water-based emulsion paint (solid content 27%, specific gravity 1.05, viscosity: 10 s (seconds) (viscosity is measured with an Iwata cup viscometer (NK-2)))
・Pipe A: cast iron pipe with a nominal diameter of 150 (outer diameter D: 169 mm)
・Rotating peripheral speed of tube A: 110 m/min (minute)
・Painting speed (moving speed of painting gun 1) V: 21.4 m/min
・Distance between the coating gun 1 and the outer peripheral surface of the tube A: 200 mm (the coating gun 1 is located directly above the tube axis o of the tube A)
・Paint discharge pressure of paint gun 1: 5 to 6 MPa
・ Same nozzle tip 1a: 950067-TC (manufactured by Spraying Systems Japan LLC)
・Same discharge amount Q: 165g/10s
・Number of same passes: 1 time (one way)
・ Air curtain S (air gun 3): Air blaster AB-25P (manufactured by Kyoritsu Gokin Seisakusho Co., Ltd.)
・Air discharge pressure of air gun 3: 0.01 to 0.04 MPa
The air gun 3 (air curtain S) was synchronized with the coating gun (airless spray gun) 1 and moved together (integrally) in the tube axis o direction.
The tangential direction means that the center line c of the width of the air curtain S in FIG. (on the side end face) refers to the direction of the state.

The transfer efficiency (%) was determined by the following procedures (a) to (g).
(a) Before coating the pipe A, the discharge amount (g/10s) of the paint b is measured.
(b) Attach a piece of paper (140 x 120 mm) weighed in advance to tube A.
(c) The coating gun 1 is moved in one direction over the entire length of the pipe A to coat.
(d) Peel off the paper, dry it under the conditions of 120° C. for 1 hour, and measure the weight.
(e) Calculate the difference in weight before and after painting, and calculate the actual coating amount per 1 m ² from the painted area, the solid content of the paint, and the specific gravity of the paint.
(f) Based on the discharge amount before coating and the moving speed of the gun, the theoretical coating amount per ^square meter is calculated using the following formula (1).
Theoretical coating amount = (60/V) x (Q/10) x D x π) (1)
(g) Calculate the ratio of the theoretical coating amount and the actually measured coating amount to calculate the coating efficiency.

According to this experiment, when the air curtain S of Experimental Example 4 was not formed, the coating efficiency was 80%.
On the other hand, when the air a (air curtain S) in Experimental Example 5 is shifted outward from the tangential direction of the outer peripheral surface of the tube A and only one air curtain S is used, the ejection direction of the paint b is on the air curtain S side. The ink was curved, and the ejection pattern P flowed toward the air curtain S, resulting in poor coating efficiency.
When the air a (air curtain S) of Experimental Example 6 was directed inward in the tangential direction of the outer peripheral surface of the tube A, the scattering in the outer peripheral direction of the tube A was reduced, but the scattering in the axial direction increased and the coating was similarly applied. It was inefficient.
When the air a (air curtain S) of Experimental Example 1 is set in the outer tangential direction perpendicular to the tube axis o of the tube A, the layer thickness of the ejection pattern P is reduced as compared with Experimental Examples 2 and 3, and The scattering of the coating material b in the direction (peripheral direction of the tube) was slightly reduced as compared with Experimental Example 4, and the coating efficiency was 84%.
In Experimental Example 2, the air a was discharged inward at 5 degrees (θ = 5 degrees) in contrast to Experimental Example 1, and an upward airflow was generated up to about 50 mm in the tube top direction. Scattering in the circumferential direction was reduced compared to Experimental Example 1, and the transfer efficiency was 85%.
Experimental example 3 is a case where the spraying direction of air a is 20 degrees (θ = 20 degrees) inward compared to experimental example 1, and the upward airflow in the tube top direction is increased compared to experimental example 2, and the paint b Although the scattering in the circumferential direction decreased, the paint mist on the tube A increased, and the coating efficiency was 82%.

From the above experimental examples, the transfer efficiency is the best when the spraying angle θ of the air a is around 5 degrees. It can be understood that the transfer efficiency also decreases. From these, it is preferable that the air a discharged from the air gun 3 is blown in the tangential direction of the outer periphery of the pipe A. The discharge direction of the paint b is set to be perpendicular to the pipe axis o, and the discharged air a from the air gun 3 is directed from the discharge direction. It can be seen that the inward inclination of 0 to 20 degrees is preferable.

In the above embodiment, the coating gun 1 and the air gun 3 are moved in the direction of the tube axis, but it is also possible to fix the coating gun 1 and the air gun 3 and move the tube A in the direction of the tube axis o.
The coating gun 1 and the air gun 3 may not be directly above the pipe A (upper side in the direction perpendicular to the pipe axis), but may be inclined at any position around the pipe axis o as long as there is no problem.
The ejection pattern P may be circular or the like, instead of an oblong atomization type elongated in the direction of the tube axis o.
It goes without saying that the present invention can be applied to coating the outer surface of various pipes other than the ductile cast iron pipe A.
In this way, the embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope of equivalence to the scope of claims.

A Pipe P Paint discharge pattern S Air curtain F Frame a Discharged air (discharged air)
b paint (paint particles)
o Tube shaft 1 Coating gun 1a Nozzle tip of coating gun 2 Tube rotation support roller 3 Air gun 4 Support rod 5 Paint pipe 6 Air gun support pipe

Claims (7)

In the method of coating by spraying the coating material (b) onto the outer surface of the tube (A) rotating about the tube axis (o), separate A method for coating the outer surface of a pipe, characterized in that an air curtain (S) is formed by air (a) discharged from an air gun (3) of (1). 2. To the outer surface of the pipe according to claim 1, characterized in that the discharge direction of the discharged air (a) from the air gun (3) for forming the air curtain (S) is tangential to the outer circumference of the pipe (A). painting method. The discharge direction of the paint (b) is the direction orthogonal to the pipe axis (o), and the discharge direction of the air (a) discharged from the air gun (3) is set so that the discharge direction of the paint (b) is the pipe axis ( The method for coating the outer surface of a pipe according to claim 2, characterized in that the coating is tilted to the o) side by 0 to 20 degrees. 4. The method of coating an outer surface of a pipe according to claim 1, wherein said coating gun (1) and said air gun (3) are synchronously moved together in the direction of the pipe axis (o). 5. A coating apparatus for performing the coating method on the outer surface of a pipe according to any one of claims 1 to 4, comprising: a coating gun (1) for spraying the coating material (a) onto the outer surface of the rotating pipe (A); A coating apparatus consisting of separate air guns (3) forming air curtains (S) on both diametrical sides of the tube (A) of the discharge pattern (P) of the coating material (b). 6. The coating apparatus according to claim 5, wherein the coating gun (1) and the air gun (3) move synchronously together in the direction of the tube axis (o). 7. A coating apparatus according to claim 5 or 6, wherein the air gun (3) has a direction of discharging air (a) that is variable in a radial direction of the pipe (A) with respect to a direction of discharging the coating material (b).

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