JP6924480B2 - Steel bridge maintenance method - Google Patents

Description

The present invention relates to a method for maintaining steel structures in steel structures such as steel bridges, tunnels, and factory plants.

Conventionally, steel structures such as steel bridges, regardless of whether they are newly installed or existing, are used to prevent the occurrence of rust, or especially for existing steel structures, to renew the coating that has been corroded due to aging. In addition, preventive maintenance is given. In this way, preventive maintenance requires removing rust and the like, and removing old paint film. Therefore, in recent years, rust and paint film are removed by blasting (type 1 keren), and then a new paint film is applied. Is being done.

Usually, as the projection material used for such blasting treatment, Armandite garnet made of natural minerals, steelmaking slag which is a mineral-making mineral, and the like are used. However, when such Armandite garnet or steelmaking slag is used as the projection material, the projection material is crushed during the blasting process, and a huge amount of waste is generated. In particular, when PCB (polychlorinated biphenyl) or lead is used in the old coating film, not only the removed old coating film but also the projection material used for the blasting treatment becomes a specially controlled industrial waste. It costs a lot of processing.

To deal with such a problem, for example, in Patent Document 1, after collecting the projecting material and dust after polishing in a recovery tank, the projecting material and dust and the like are separated and classified in the recovery tank to form dust. And the like are collected, while the structure surface cleaning system that reuses the separated projecting material is disclosed.

Further, apart from the above problem, the strength of the steel structure may be biased at the welded portion. Here, for example, in the case of a steel road bridge, fatigue cracks occur from the welded portion where the strength is biased due to the entire bridge shaking or vibrating when a car passes or a strong wind blows. Causes a problem. For this reason, the actual situation is that repair costs are enormous.

Further, for example, Patent Document 2 discloses a method of preventing the occurrence of cracks by applying a primer to a structural discontinuity caused by a welded joint of a steel structure.

Further, Patent Document 3 discloses a method for improving the fatigue performance of a welded joint in which ultrasonic peening treatment is performed on the end face of the welded joint and the weld toe at the end of the welded joint.

Japanese Unexamined Patent Publication No. 11-207624 Japanese Unexamined Patent Publication No. 2006-102738 Japanese Unexamined Patent Publication No. 2006-142637

However, in the conventional configuration as described above, the amount of dust including the coating film, the projection time, and the projection amount of the projection material are still large, and the cost is naturally enormous.

Therefore, an object of the present invention is to provide a maintenance method for a steel structure capable of dramatically reducing the amount of dust including a coating film, the projection time, and the projection amount of a projection material.

In the present invention, a coating film softening agent is applied to a coating film of a steel structure, and a metal projection material is projected onto the coating film softened by the coating film softening step to obtain the coating film. It is a maintenance method for a steel structure, which comprises a projection material projection step for removing from the steel structure.

Further, a configuration is also proposed in which a hand tool scraping step of scraping the softened coating film with a hand tool is executed between the coating film softening step and the projection material projection step.

Here, as the coating film softening agent, a known release agent can be used. However, it is not possible to completely remove the coating film from the steel structure only by softening the coating film only by executing the coating film softening step by applying the release agent. Even if the hand tool scraping step is additionally executed, it cannot be completely scraped by the hand tool alone, and a coating film containing lead or the like remains on the surface of the steel structure. Therefore, in the present invention, the coating film can be completely removed from the steel structure by executing the projection material projection step at least after the coating film softening step. Moreover, since the coating film is in a softened state due to the coating film softening agent being applied, the coating film can be peeled off from the steel structure extremely easily. In particular, if the hand tool scraping step is executed in advance, it is possible to dramatically reduce the amount of dust including the coating film, the projection time, and the projection amount of the projection material in the projection material projection step. In the present invention, it can be said that the above-mentioned coating film softening agent functions as a dust reducing agent, a dust suppressing agent, or a blast pretreatment agent.

Further, in the coating film softening step, it is desirable that the coating film coated with the coating film softening agent becomes a wet sheet.

In such a configuration, since the coating film to be peeled off can be handled as a lump, there is an advantage that the amount of scattering of the coating film can be further suppressed.

Further, it is preferable that the coating film softening agent contains an aqueous organic solvent as a main component.

With such a configuration, safety can be ensured for workers and the environment.

Further, before the coating film softening step, a scaffolding installation step of installing a scaffolding around the steel structure is executed, and in the coating film softening step, the coating film softening agent is applied to the coating film using the scaffolding. It is applied, and in the hand tool scraping step, the scaffold is continuously used to scrape the coating film with a hand tool, and in the projection material projection step, the scaffold is continuously used to the coating film. A configuration for projecting a projecting material is proposed.

With such a configuration, it is possible to standardize the working environment in executing the coating film softening process, the hand tool scraping process, and the projection material projection process, so that the process can be simplified and simplified. It is possible to improve the efficiency of the maintenance method.

The present invention has an excellent effect that the amount of dust including the coating film, the projection time, and the projection amount of the projection material can be dramatically reduced.

It is a flow chart which shows the maintenance procedure of a steel bridge. It is explanatory drawing which shows the surface of the steel structure when the hand tool scraping process is executed. It is explanatory drawing which shows the surface of the steel structure when the projection material projection process is executed. It is a schematic diagram of a circulation type projection apparatus.

Hereinafter, examples embodying the present invention will be described in detail. The present invention is not limited to the examples shown below, and the design can be changed as appropriate.
As shown in FIG. 1, as a maintenance procedure for the existing steel bridge K (steel structure), first, a temporary curing facility is installed on the steel bridge K to be maintained. Specifically, a scaffold is temporarily installed on the steel bridge K, and a dustproof sheet is installed so that dust does not leak to the outside (scaffold installation process).

In addition, the unpainted portion is cured, and advance preparation (S101) is performed to install a device for projecting a common projection material capable of simultaneously performing blast processing and shot peening processing. In this embodiment, the common projection material is projected, but it is of course possible that the blasting process and the shot peening process are separate steps using different metal-based projection materials. Further, only one of the blasting process and the shot peening process may be executed.

After that, the type and thickness of the old coating film T applied to the steel bridge K, the state of the steel bridge K, and the like are investigated (S102). Then, based on the survey results, the type of projection material (common projection material) to be used, the injection speed, and the like are determined. In addition, the type and coating method of the coating film softening agent described later are determined. Of course, S102 may be performed before S101.

Next, the coating film softening agent is applied to the old coating film T applied to the steel bridge K, and the process waits until a predetermined softening time elapses (S103: coating film softening step). Here, as the coating film softening agent, a known peeling material containing an aqueous organic solvent as a main component is preferably adopted. Specific examples of the aqueous organic solvent include, but are not limited to, alcohol solvents such as methyl alcohol, ethyl alcohol and isopropyl alcohol; and ketone solvents such as acetone and methyl ethyl ketone. Moreover, as a coating method, a spray method, a brush coating method, a roller method and the like are exemplified.

Next, the softened coating film T is scraped off with a hand tool such as a scraper or a leather scraper (S104: hand tool scraping step). In this step, it is desirable to scrape off about 70% or more of the coating film T to be completely removed. Here, the softened coating film T becomes a wet sheet and can be scraped off as a lump. Therefore, workability is extremely good. It should be noted that such a step has an advantage that the amount of dust including the coating film can be reduced, but it can be omitted as long as the projection material projection step described later is executed.

Here, after the hand tool scraping step is executed, as shown in FIG. 2, the coating film T remains in the fine recesses on the surface of the steel bridge K. Therefore, it is effective to further execute the projection material projection step on the steel bridge K.

That is, using the common projection material determined in S102, simultaneous processing of blast processing and shot peening processing is performed next (S105: projection material projection step). Specifically, by projecting the common projection material, the residual coating film T or the like on the steel bridge K is peeled off, and the substrate adjustment (blast treatment) of the portion to be adjusted is performed, and at the same time, the surface of the steel bridge K is formed. Simultaneous processing of applying compressive residual stress to (shot peening processing) is performed. As a result, as shown in FIG. 3, the coating film T remaining in the fine recesses on the surface of the steel bridge K is completely removed.

It should be noted that the projecting material projection step of the present invention is not limited to the simultaneous processing of the blasting process and the shot peening process, and each process may be performed in sequence, or only one of them may be performed. good.

Here, the coating film, rust, etc. peeled off by the simultaneous treatment and the used common projection material are generated as dust, but the amount of dust is extremely small because the hand tool scraping step (S104) is executed in advance. Become. Further, since the dustproof sheet is stretched in S101, the dust does not leak to the outside, and the dust accumulates at the work site.

After that, the bare ground that has undergone simultaneous processing of blast processing and shot peening processing is confirmed (S106). Such confirmation includes not only visual confirmation but also comparison with, for example, ISO8501 blast photo book, roughness confirmation with a surface roughness measuring instrument, and the like. As a result, it is confirmed whether or not the unpeeled coating film remains or whether the roughness of the bare ground is within the standard, and accurate treatment is performed for the insufficient portion. For example, the base material is adjusted by using a hand tool or the like in a part where the blasting process cannot be performed.

In this way, the final finish coating for forming the final coating film is performed on the portion where the bare ground has been confirmed (S107). It should be noted that such coating is generally applied in layers multiple times, such as an undercoat coating as an anticorrosive coating, an intermediate coating for protecting the anticorrosive coating, and a topcoat coating as a final finish coating.

When the painting is completed, the confirmation (S108) is performed. Such confirmation includes not only confirmation of the film thickness after the coating has dried, but also confirmation of the wet film thickness using, for example, a wetness gauge during the coating operation. Further, such confirmation is performed not only after the top coat coating, which is the final finish coating, but also during the undercoat coating and the intermediate coating.

When the painting work is completed by the above confirmation, the site is cleaned up (S109). Specifically, the maintenance is completed by collecting the scaffolding, the dustproof sheet, etc., and withdrawing the projection material injection device.

In addition, the dust recovery step is executed together with the above procedure (S110). Specifically, the used common projection material generated in the projection material projection step (S105) and dust containing exfoliated material, rust, and the like are separated and collected.

The recovered used common projectile material can be reused if it is not crushed by projection. The reusable common projection material can significantly reduce the amount of waste by separating it from the peeled coating film and other foreign substances.

Further, as the common projection material used in the simultaneous treatment, for example, a condition cut wire shot (specified in JIS B2711: 2013) is desirable. Conditioned cut wire shots include so-called round cut wires.

Hereinafter, the circulation type projection device 1 capable of injecting the common projection material and capable of collecting and separating the used common projection material, the peeled coating film, and the like will be described as an example.

As shown in FIG. 4, the circulation type projection device 1 includes a device main body 2 installed adjacent to a work site α of a steel bridge K to be worked. Further, the device main body 2 is provided with a pumping hose 4, and an injector 3 is connected to the tip of the pumping hose 4. A common projection material is ejected from the injector 3. Further, the apparatus main body 2 is provided with a suction hose 5, and the tip of the suction hose 5 is arranged at the work site α. As a result, through the suction hose 5, the used and uncrushed common projecting material generated at the work site α, the crushed material of the common projecting material, and the dust composed of foreign matter including the peeled coating film and rust are removed. Can be aspirated. In order to prevent dust from leaking to the outside, a dustproof sheet (not shown) is stretched at the work site α, and a blower, a dust collector, and the like are appropriately installed.

Further, a common projection material hopper tank 10 is arranged in the device main body 2 of the circulation type projection device 1. More specifically, the common projection material hopper tank 10 has a function of storing the common projection material and the used common projection material. Further, the common projection material hopper tank 10 is connected to a common projection material pressurizing tank 11 for pressure-feeding the common projection material stored in the common projection material hopper tank 10 to the work site α.

Further, the dry compressed air supply means 30 is connected to the common projection material pressurizing tank 11 via the dry compressed air pipe 31. The dry compressed air supply means 30 includes an air compressor and an air dryer for supplying dry compressed air.

Further, the pressure feeding hose 4 is connected to the common projection material pressurizing tank 11. With this configuration, the common projection material is injected from the injector 3 via the pumping hose 4 by the air pressure of the dry compressed air supplied from the dry compressed air supply means 30, and is common to the steel bridge K to be worked. Projection of the projecting material is feasible.

Dust containing foreign matter such as used common projection material, crushed material, and peeled coating film deposited on the work site α is collectively sucked from one end of the suction hose 5. Then, the dust X sucked by the suction hose 5 reaches the inside of the sorting chamber 40 arranged above the common projection material hopper tank 10.

A dust hose 51 is attached to the sorting chamber 40, and a dust collecting unit 50 as a peeling coating film collecting unit is connected to the dust hose 51. Further, an air suction device 60 as a dust suction means is connected to the dust recovery unit 50. Therefore, the dust can be sucked by the air suction force of the air suction device 60.

The design of the above configuration can be changed as appropriate. For example, the injector 3 and the suction hose 5 may be separate or integrated (vacuum blast type). Further, the sorting chamber 40 does not need to be arranged directly above the common projection material hopper tank 10, and the position is not particularly limited. The common projection material hopper tank 10 may be kept airtight while communicating with the common projection material hopper tank 10, or a dedicated tank for temporarily storing the common projection material is arranged, and the common projection material hopper tank 10 is arranged at a desired timing. A common projection material may be supplied to the vehicle. Further, it is desirable to be able to supply a new product when the amount of the common projection material in the circulation type projection device 1 becomes smaller than the specified value. Further, the device main body 2 may be mounted on a vehicle and can be moved, for example.

Further, the blasting treatment is defined in JIS Z 03120: 2004 "General rules for blasting treatment method for substrate adjustment", respectively. Specifically, the blast treatment is "a grinding material having a large kinetic energy is made to collide with the surface of the steel material to be treated, and the surface of the steel material is finely cut and hit to remove oxides or deposits on the surface of the steel material. To clean and roughen the surface. " In addition, in JIS B 2711: 2013 "Spring Shot Peening", shot peening means "improvement of fatigue strength and stress corrosion cracking resistance by striking hard particles close to a sphere against the surface layer of a spring at high speed. Cold working method to achieve. Applying compressive residual stress to the surface and processing and hardening the surface. "

K steel bridge (steel structure)
T coating film

Claims (2)

A coating film softening process that applies a coating film softening agent to the coating film of a steel bridge,
A projection material projection step of projecting a metal projection material onto the coating film softened by the coating film softening step in a softened state and removing the coating film from the steel bridge.
Only including,
Prior to the coating film softening step, a scaffolding installation step of installing a scaffolding around the steel bridge is executed.
In the coating film softening step, the coating film softening agent is applied to the coating film using the scaffolding.
In the projection material projection step, the scaffolding is continuously used to project the projection material onto the coating film.
The used projectile material generated on the scaffold and the dust containing the peeled coating film were collected while being separated.
A steel bridge maintenance method characterized in that uncrushed projection material among the collected used projection materials is reused and projected onto the steel bridge. In the projection material projection step, the projection material is a common projection material, and the common projection material is projected to perform blast processing and shot peening processing at the same time.
The blast treatment adjusts the surface of the steel bridge by projecting the common projection material onto the steel bridge.
The shot peening process applies compressive residual stress to the surface of the steel bridge by projecting the common projection material onto the steel bridge.
The common projection material is
It is a condition cut wire shot specified in JIS B 2711: 2013.
Moreover,
A step of forming a final coating film on the surface of the steel bridge is included after the step of simultaneously performing the blast treatment and the shot peening treatment.
The steel bridge maintenance method according to claim 1.

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