JPS6055192B2 - Method for simultaneously coating the inner and outer surfaces of large-diameter metal pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously coating the inner and outer surfaces of a large diameter metal tube.

More specifically, the present invention provides a method for coaxially supporting a preheated metal pipe with pipe fittings provided at or near both ends horizontally within a powder resin fluidized bed by contacting the pipe fittings with a rotating support; Powdered resin is fed together with gas through the rotating support to form a resin coating on the inner surface of the metal tube, and at the same time, the powdered resin is made to flow in a fluidized bed so that the metal tube is immersed, and coated on the outer surface of the metal tube. The present invention also relates to a method for simultaneously coating the inner and outer surfaces of a large-diameter metal tube, which is characterized by forming a resin coating.
Recently, the demand for metal pipes with internal and external coatings has been increasing.

This is because it is suitable, for example, when corrosive substances are passed through the pipe and the installation site is in a corrosive environment for metal pipes. As a method for simultaneously coating the inner and outer surfaces of such a metal tube, the fluidized dipping method has conventionally been the mainstream. but,
Apart from small diameter metal pipes, large diameter metal pipes (e.g. outer diameter 1
When coating the inner and outer surfaces of metal tubes (over 00-φ) by the fluidized dipping method, the typical length is 5.5Trl, so handling the metal tubes requires a lot of effort and the work is dangerous. The current situation is that it has become something that comes with it. For example, to explain the process of the conventional fluidized immersion method with reference to FIG. 1, first, a metal tube 4a is suspended by a suspension conveyor 3a via a hanging piece fixed near the end of the tube, and is suspended from the upper part of the heating furnace 1a. It is then put into the heating furnace 1a (arrow A).

The metal tube heated (preheated) to the required temperature in the heating furnace 1a is horizontally moved to the upper part of the fluidized bed 2a (as indicated by the arrow B).
), and is further moved downward and immersed in the fluidized bed 2a (arrow C). The metal tube whose inner and outer surfaces are coated simultaneously in the fluidized bed undergoes a cooling process, completes its treatment, and is moved to a storage site (arrow DNE). As mentioned above, in the conventional fluidized dipping method, the metal tube is basically in an upright (suspended) state and is moved vertically and horizontally in that state, so when it comes to large diameter metal tubes, the stability during movement is poor. There were many drawbacks and flaws, such as the work being dangerous, the height of the equipment being large, and therefore the building being large, and the processing capacity being limited due to the many steps that required manual labor. The inventors have invented a method of simultaneously coating the inner and outer surfaces of a metal tube while maintaining well-defined lateral support, and have succeeded in eliminating the above-mentioned drawbacks and deficiencies.

The method of this invention is basically a method of simultaneously coating the inner and outer surfaces in separate ways.

That is, the inner surface is coated by feeding powdered resin into a metal tube together with gas, and the outer surface is coated at the same time by fluidized immersion. In the first place, a metal tube with internal and external coatings is required when, for example, a corrosive substance is passed through the metal tube and the environment in which the metal tube is installed is unfavorable to the metal tube.

Therefore, as a condition for the metal tube used, it is necessary to have a coating on the entire inner and outer surfaces of the metal tube, regardless of the shape. However, since the supporting parts of metal pipes cannot be coated, they are usually repaired with paint or the like. When coating the inner and outer surfaces of a metal tube while supporting it laterally, the metal tube is held between rotating supports only at both ends of the tube, and unlike the conventional fluidized dipping method, there is no room to choose where to support the metal tube. This means that we have to worry about this clamping method. The method of the present invention solves this problem as well.

The method of this invention will be explained based on the illustrated embodiment. First, in FIG. 2, the large diameter metal tube 4 on the conveyor 6 is
It enters the heating furnace 5 together with the conveyor 6, is heated to the required temperature while passing through the heating furnace 5, further rolls on the inclined guide plate 7, and is placed stationary on the pedestal 9 in the fluidized tank 8. Ru.

Next, this preheated metal tube is heated from both sides in the longitudinal direction.
Coaxially rotated and held by the rotary support, and then the pedestal 9 is lowered slightly to separate it from the metal tube, and while the metal tube is rotated, the powder resin is fed into the metal tube along with gas (for example, air) through the flow path inside the rotary support. At the same time as forming a film on the surface,
Gas is introduced into the lower chamber 10 of the fluidized bed to fluidize the powder resin (
A film is also formed on the outer surface of the metal tube by fluid immersion. The metal tube used here is a metal tube having a pipe joint (for example, a ring-shaped body such as a collar or flange) at or near the tube end. FIG. 3 is a longitudinal cross-sectional view showing the relationship near the tube end (the left end is omitted because it is symmetrical), and the relationship among the pipe joint, rotating support, and coating will be explained based on this diagram.

A pipe joint wrapped and fixed along the outer periphery of the metal pipe 4 near the pipe end, that is, a collar 11 having a circular cross section, and a rotating support 12
The metal tube 4 is rotatably held in close contact with the metal tube facing inclined surface 13. The rotary support body 12 has powder fluid inlet/outlet ports 1 and 4, a gas flow path 15, a metal tube facing opening 18, and a metal tube facing inclined surface 13 defined in this order on its inner surface, and the inner periphery of the gas flow path 15 is defined as follows. A space is formed between the surface and the outer peripheral surface of the metal tube 4. First, the powdered resin enters the gas flow path 15 along with the gas from the inlet/outlet 14, and most of it enters the metal tube 4 via the gas flow path 15.
Since the inner diameter of the gas flow passage 15 is made larger than the inner diameter of the inlet/outlet 14, some of the powder resin stalls in the gas flow passage 15 and accumulates in the E section of the rotary support 12, and the powder resin is transferred to the rotary support 12. 12
As the powder resin rotates together with the metal tube 4, the powder resin enters the space described above, and a metal tube inner surface coating 16 including the side and outer end surfaces of the metal tube 4 is formed. The end of this metal tube inner surface coating is located on the collar 11 on the rotating support side. On the other hand, the outer surface coating 17 of the metal tube is formed by fluid dipping, and the end thereof is formed by the collar 11.
It is above. In this way, a uniform coating is formed on the outer surface of the metal tube with the boundary between the collar 11 and the rotary support 12 in close contact with each other.

Of course, no coating is formed on the above-mentioned close contact area, but since this metal pipe with a collar is connected by the connection method shown in Figure 4, it can withstand corrosive substances on either the inside or outside. . In other words, referring to FIG. 4, align the collar groove 21 of the split flange 19 with the packing 20 inside the collar 11, tighten the split flange, and then tighten the metal tube 4.
Since the pipes are connected, the liquid in the metal pipe comes into contact with only the coating and the sealing packing, and the parts that are vulnerable to the external environment are housed in the flange, so they are less likely to corrode.

Of course, the portions on which the film is not formed may be repaired as appropriate with resin paint or the like. Next, the case of a large-diameter metal pipe having general-purpose plate flanges at both ends as a pipe joint will be described with reference to FIG.

FIG. 5 is a longitudinal cross-sectional view showing the relationship near the end of the metal tube (the left end is omitted because it is symmetrical). Rotating support 2 from the direction
3 shows the state of coaxial rotational clamping.

Thereafter, a film is formed by a method similar to that shown in FIG. In the rotary support 23 used here, a ring-shaped sealing material 24 is embedded in the side facing the flange 22 and at a location corresponding to the outer periphery of the packing seat P of the flange so that a part of it protrudes. At least two protrusions 25 to be inserted into the bolt holes are provided at locations corresponding to the bolt holes. A fluid inlet/outlet 28 is opened in the rotary support body 23 in the axial direction, and the fluid inlet 28 becomes an enlarged opening 29 toward the flange side. When the metal tube 4 is clamped by the rotating support body 23 by aligning the protrusion 25 with the bolt hole of the flange, the inside and outside of the metal tube 4 are partitioned by the annular sealing material 24, and the weight of the metal tube is supported by the protrusion 25 and the rotation is transmitted. . Therefore, the flange 22 and the annular seal 24
A film is formed on the inner and outer surfaces of the metal tube, bordering on the areas in close contact with the metal tube. The metal tube 4 thus obtained is connected to a metal tube 4'' having the same specifications as shown in FIG. Therefore, it is safe because corrosive substances do not come into direct contact with the contact area with the annular sealing material 24 and the insertion area of the protrusion 25 on which the coating was not formed.Of course, the areas where the coating was not formed are coated with appropriate paint. 35, 36, . . . are washers (backings).Thus, this invention allows the metal tube to be placed horizontally in a stable state, and both ends of the metal tube in the gas flow hole of the rotary support. Furthermore, the inner and outer surfaces of metal tubes, including the outer surfaces of both ends, can be powder-coated uniformly, and the process of heating, moving, and painting metal tubes can be done unattended, especially for large-diameter metal tubes. This is an extremely significant invention that has excellent effects such as good workability and low risk when body painting is performed, and can form different types of coatings on the inner and outer surfaces of metal tubes as desired.

Experimental examples will be given below to illustrate this invention. [Experiment example: 1]...In the case of Figure 3, the length is 5.5m0)SG
At each 19th point from the end of the Pl5OA tube, a diameter 6
A round bar of the frame was attached to the outer periphery of the steel pipe and fixed by welding to form a collar.

When the main dimensions of the gas flow hole are expressed as a ratio to the inner diameter D1 of the inlet 14, D2=1.29D1, D3=1.0
8D1, D4=0.34D1. Nylon 17$ using such a rotating support (60 rotations)
The inner surface of the steel pipe, which had been preheated to approximately 310° C. in a fluidized fluid bath, was powder coated with nylon 121t1 resin for approximately 2 seconds. As a result, a uniform, pinhole-free coating could be simultaneously formed on the inner and outer surfaces of the steel pipe, except for the contact area with the rotating support at the collar. [Experiment example: 2]...In the case of Fig. 5, 200ASGP tube 5.5rr1. 10k9/C on both ends of
Weld the flange of i.

This vibrator was heated to approximately 310°C, and a heat-resistant sealing material (heat-resistant O-ring, trade name: Viton, outer diameter: 276°C) was applied to the rotating support.
3Tfnφ, inner diameter 259.5Tfr1nφ) are attached to both ends. However, D1=155 order φ, D2
=25277!77! φ, D3=276 mφ. This was immersed in a fluidized tank containing nylon 1 resin, and at the same time, nylon 1 resin powder was passed inside to coat the inner surface. The results showed that the inner and outer surfaces of the rotary support were uniformly coated, except for the parts that contacted the sealing material and the protrusions.

[Brief explanation of drawings]

FIG. 1 is a process diagram illustrating a conventional method for simultaneously coating the interior and exterior surfaces of a metal tube, FIG. 2 is a process diagram illustrating an embodiment of the method for simultaneously coating the interior and exterior surfaces of a metal tube according to the present invention, and FIG. is a longitudinal cross-sectional view of the vicinity of the tube end, FIG. 4 is a vertical cross-sectional view of the joint of the obtained tube with simultaneous inner and outer cladding, FIG. 5 is a view corresponding to FIG. 3 explaining another example, and FIG. This is a diagram corresponding to Figure 4. 4...Large diameter metal pipe, 8...Fluidization tank,
11...Baba, 12...Rotating support.

Claims (1)

[Claims] 1. In a method for simultaneously coating the inner and outer surfaces of large-diameter metal pipes, a preheated metal pipe with collar-shaped fittings wrapped around or near both ends is coated with a rotating support in a powder resin fluidized bed. The peripheral edge of the opening on the gas outlet side of the gas flow passage provided in the rotary support is brought into contact with the side edge of the pipe joint to support coaxial rotation horizontally, and the inner peripheral surface of the gas flow passage of the rotary support and the metal A space is formed between the outer circumferential surface of the end of the tube, and powdered resin is fed together with the gas through the gas flow hole of the rotary support to form a resin coating on the inner surface of the metal tube. A resin coating is formed on the outer surface of the metal tube, on both end surfaces of the metal tube in the gas flow path of the rotating support, and on the outer surface of both ends, by flowing the powder resin in a fluidized bed as if immersed. A method for simultaneously coating the inside and outside surfaces of large-diameter metal pipes.