JPS6044552B2 - Corrosion prevention method for steel pipe joints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing corrosion of a complex irregularly shaped portion of a joint of a steel pipe, particularly a joint of a small-diameter steel pipe for burial.

Small-diameter steel pipes for burial are generally coated with synthetic resin to prevent corrosion, but the threaded or flange portions of the ends, elbows of joints, T-shaped Ξ-pipe joints, etc. are not coated with anti-corrosion paint. do not have.

Conventionally, in order to prevent corrosion of complex irregularly shaped joints of steel pipes, anticorrosion tape has been wrapped around the joints of steel pipes, as shown in FIG. In Figure 1, 1 and 2 are steel pipes, and 3 is T-shaped Ξ
Directional pipe joint, 4 is anti-corrosion tape. However, when using the anti-corrosion tape 4, the joint 3 itself has large irregularities, and the difference in level between the steel pipes 1 and 2 (indicated by reference numeral 5 in Fig. 1) is large, and the anti-corrosion tape 4 is applied along these irregularities. Wrap it around the
It takes a considerable amount of skill to make them adhere tightly without any gaps, and sufficient anti-corrosion performance cannot be expected. In addition, in order to ensure the anti-corrosion function, the joint part is covered with a two-part formwork 7 made of vinyl chloride resin, etc., as shown in Fig. 2, and a filler material 6 such as hardening epoxy resin is placed inside it. A method has also been proposed in which a corrosion protection layer is formed by pouring and hardening within the frame 7, but this method increases the manufacturing cost of the form 7, making it a very expensive corrosion protection method.

An object of the present invention is to provide a method for preventing corrosion of a steel pipe joint, which can be easily carried out at a construction site without requiring any skill, and which can provide reliable corrosion protection.

I Corrosion prevention method for steel pipe joints according to the present invention involves applying a plastic mastic to a steel pipe joint to cover the part, spraying a zeta-curing foam resin liquid or a hardening foam resin liquid onto the surface of the mastic layer, and applying the mask layer to the steel pipe joint. The mastic layer is then covered and cured or cured and foamed to form a hard plastic foam layer on the mastic layer. The diameter of the steel pipe that forms the steel pipe joint that is the object of the present invention may be any diameter, but it is particularly buried below 150A, generally 50A.
Effective for joints of A and below steel pipes.

Of course, most of these steel pipes except for the end portions are coated with synthetic resin or the like. Mastic refers to an adhesive substance made by adding a filler to a bituminous substance, and also refers to adhesive substances in general, but in the present invention, a plastic mastic that maintains a certain shape and is plastically deformed by a slight external force is used. Examples of these plastic mastics include synthetic rubbers, such as butyl rubber, and asphalt-based mastics. These plastic mastics are generally commercially available in bulk or in the form of tapes, sheets, or rods. Examples of the method for preventing corrosion of steel pipe joints according to the present invention are shown in FIGS. 3 to 6.

Figure 3 shows a T-shaped three-way pipe joint, Figure 4 shows an elbow, and Figure 5 shows a T-shaped three-way pipe joint.
The figure shows the structure of a joint using a reducing joint, and FIG. 6 a flange joint. To configure the method of the present invention, first, a plastic mastic 8 is applied to a joint portion formed by the ends of the steel pipes 1, 1, 2 and the joint 3 to cover the portion, thereby forming a mastic layer 8.

When the mastic 8 is crimped onto the joint, it deforms plastically in accordance with the uneven shape of the joint, adheres closely to the joint, and forms a corrosion protection layer with excellent performance. The curable foam resin and cured foam resin liquid used in the present invention will be explained.

The former is a resin liquid that is already foamed, that is, contains air bubbles, and hardens with the passage of time, and is in a state similar to so-called shaving foam I. The latter is a resin liquid that foams and hardens over time.
After these are sprayed onto the object to be coated, they are cured or foamed to form a plastic foam layer on the object to be coated. In the present invention, a resin liquid is used that forms a rigid plastic foam, ie, a low-expansion plastic foam. Polyurethane is suitable as these resins, but the resin is not limited thereto. To configure the method of the invention,
A curable foaming resin liquid or a curable foaming resin liquid is sprayed onto the surface of the mastic layer 8 that has been formed in advance.
is covered and cured or cured and foamed to form a hard plastic foam layer 9 on the mastic layer 8.

By using an appropriate foaming state or foaming agent and setting a curing time, the resin liquid is cured to a desired thickness without dripping over the mastic layer 8.

It is appropriate that the curing or foam curing time is 4 to 5 minutes. Moreover, this plastic foam has strong adhesion to the mastic layer and the steel pipe. The hard plastic foam layer 9 protects the anti-corrosion layer 8 of the mastic, and the layer 9 itself has anti-corrosion performance, thereby doubly protecting the joint and ensuring the anti-corrosion effect.

That is, on the one hand, the hard plastic foam layer 9 prevents damage to the anti-corrosion layer 8 of the mastic due to falling earth and sand during burying, and damage caused by shifting of the mastic layer 8 due to earth pressure after burying, uneven thickness, and biting of foreign objects. It serves as a reinforcing exterior material. On the other hand, since the hard plastic foam layer 9 contains closed cells, less water enters into the layer 9, thereby exhibiting a corrosion-preventing effect. Since the method for preventing corrosion of a steel pipe joint according to the present invention is as described above, no matter how uneven the shape of the joint is, it is possible to easily adhere the plastic mastic to the entire joint and form a reliable corrosion protection layer. In addition, since the reinforcing exterior layer is formed on the anti-corrosion layer using a curable foamed resin liquid or a foamed curable resin liquid, the reinforced exterior layer can be easily and reliably formed regardless of the shape of the anti-corrosion layer. be done.

Further, unlike the conventional method, there is no need to use a formwork, and since plastic foam is used for the exterior, the cost of materials is low, and a corrosion-resistant structure can be obtained at low cost.

[Brief explanation of drawings]

1 and 2 are partially cut-away side views showing the conventional corrosion prevention method for steel pipe joints, and FIGS. 3, 4, 5, and 6 show the corrosion prevention method for steel pipe joints according to the present invention. FIG. 2 is a partially cutaway side view showing an example. In the drawings, 1 and 2 are steel pipes, 3 is a joint, 4 is an anticorrosive tape, 5 is a step, 6 is a filler, 7 is a formwork, 8 is a plastic mastic layer, and 9 is a hard plastic foam layer.

Claims (1)

[Scope of Claims] 1 A plastic mastic is attached to a steel pipe joint part to cover the part, and a curable foam resin liquid or a curable foam resin liquid is sprayed onto the surface of the mastic layer to cover the mastic layer, and the mastic layer is cured or hardened. and a method for preventing corrosion of a steel pipe joint by foaming to form a hard plastic foam layer on the mastic layer. 2. The method for preventing corrosion of a steel pipe joint according to claim 1, wherein the hard plastic foam layer is a foam layer containing closed cells. 3. A method for preventing corrosion of a steel pipe joint according to claim 1, wherein the plastic mastic is an adhesive substance made of a bituminous substance and a filler added thereto. 4. The method for preventing corrosion of a steel pipe joint according to claim 1, wherein the plastic mastic is a synthetic rubber-based plastic.