JPS60248888A - Method to prevent rusting of steel pipe interior - Google Patents

Abstract

PURPOSE:To improve the safety of work and to keep a steel pipe from rusting for a long period by tightly sealing the steel pipe after putting ammonium hydrogencarbonate when the steel pipe is sent from a steel pipe maker before use. CONSTITUTION:When a steel pipe and parts of a heat exchanger, a diesel engine, etc. are sent from a steel pipe maker to manufacture a boiler for a power plant, they are tightly sealed after putting ammonium hydrogencarbonate. This gasifiable rust preventive has high vapor pressure, produces an immediate effect, improves the safety of work, and keeps the steel pipe, etc. from rusting for a long period.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for preventing rust on the inner surface of a steel pipe.

Conventional technology As a simple and long-term method to prevent rust on the inner surface of steel pipes, a volatile rust inhibitor [Volatllecorroe] has been used.
ton engineering nhl'bltor (abbreviation v, c, ■,)
] is commonly used. As the volatile rust inhibitor used, dicyclohexylaminium nitride (abbreviated as Daikan) is usually used.

The following is a detailed explanation of rust prevention methods and problems when shipping steel pipes from steel pipe manufacturers to manufacture boilers for power plants.

(b) Inject Daikan powder from one end of the steel pipe, usually by air spray, and stop the injection after confirming that the powder is blown out from the other end. When doing this carefully, blow further from the blowing side, allow it to blow from the other side, and then stop.

(b) Inner cap made of polyethylene resin, etc.
(attached to the inside of the tube).

Treated steel pipes are usually stored indoors, but in exceptional cases they may be stored outdoors under an awning. The storage period is usually 3 to 6 months. When the steel pipes arrive at the factory in this way, the liquid inside is blown out with compressed air just before the pipes are processed. This is to prevent the generation of toxic gas odors due to high temperatures such as welding, cutting, annealing, etc.

When inspecting after removing the internal guican like this,
Rust is often observed, especially at the tube ends and the contact surface with the cap.

The following are examples of problems that arise from the process of inserting the die can into the process of opening it.

(1) The amount of daikan used is excessive.

It is said that it is sufficient to use Daikan 30 times per 1 m3, but the rust prevention effect is usually 5 times less depending on where Daikan exists.
It is considered to be within 0an.

If we consider a steel pipe with an inner diameter of 50 mm and a length of 10 m, the internal volume is approximately 201 mm, so the required amount is 600 mm.
becomes. However, since it is necessary to spread this evenly into the tube, it is inevitably sealed by the above-mentioned spray method, but the reality is that the amount is 50 to 60 times excessive.

(2) Die can blowing work When blowing in powder with a die can, it is generally done by the spray method described above, but the powder from the die can blow out from the end of the tube and fills the work area. Daikan powder is suitable for eyes, nose,
irritates the throat. Also, although it is said to be low, LDW
It has a toxicity of about zooq/kg.

When working with workers, people usually wear dust-proof eyes and masks, but the problem remains and other workers are affected. This is also common to removal work after the product arrives at the factory.

In addition, since Daikan dissolves in alcohol, a supersaturated solution may be made and injected, but although the uniformity of spraying may be improved, overuse cannot be eliminated, and from a safety perspective,
Risk of explosion increases.

(3) Daikan's Rust Prevention Effect Volatile rust inhibitors can prevent rust by evaporating and sublimating the composition and reaching the surface of the object to be rust-protected. The vapor pressure of Daikan is 1/10 that of mercury at room temperature, so it remains effective for a long time, but on the other hand, it is not fast-acting. Therefore, if conditions such as dew condensation or humidity that cause rust occur while the effect takes effect, the expected effect may not be obtained.

In some cases, a few grams of Daikan powder is placed on both ends of a steel pipe and the ends are sealed with caps, but in this case, considering the distance that Daikan can reach, the rust prevention effect toward the center of the pipe is extremely reduced.

The problems of the current state of the method for preventing rust on the inner surface of steel pipes using die cans have been described above, but due to these circumstances, the work of enclosing die cans becomes expensive.

Problems to be Solved by the Invention An object of the present invention is to provide a method for preventing rust on the inner surface of a steel pipe, which can significantly improve cost, safety, workability, and rust prevention over conventional methods.

The present invention relates to a method for preventing rust on the inner surface of a steel pipe, which is characterized by enclosing and sealing ammonium hydrogen carbonate inside the pipe.

Function: The ammonium hydrogen carbonate used in the present invention has a rust-preventing effect that far exceeds that of Daikan in a closed container. In addition, ammonium hydrogen carbonate has a high vapor pressure, excellent fast-acting properties9, and is inexpensive. Furthermore, the work can be simplified and safety is high.

The method of the present invention is effective not only for preventing rust on the inner surface of steel pipes, but also for preventing rust during storage and shipping as parts of heat exchangers (iron-based), diesel engines, and the like.

Examples of the present invention are shown below.

Example boiler, 8TB used as alloy steel pipe for heat exchange
A24 (JIS G5462) grade, outer diameter 4a
6-1 A rust prevention test was conducted on 14 steel pipes with a thickness of 57 mm, an inner diameter of 41.2 mm, and a length of z000 mm.

The contents of the rust prevention test are as shown in Table 1, and the conventionally used Daikan and the ammonium hydrogen carbonate of the present invention were sealed under various conditions, and a blank test was also conducted. . The steel pipes used in the test were selected from those immediately after manufacture and whose interiors were visually observed to be clean. A commonly used polyethylene cap was used as the cap for sealing the tube. A pressure test was conducted on this cap, but even when pressurized to O,' 1 kg/eta, the seal could only be maintained at normal pressure after several minutes.

After being sealed with anti-corrosion agent, the steel pipes were stored in a warehouse for about five months, and then in a ship's hold for a total of 10 days until they arrived at the inspection site.

The measurement results and evaluation are also shown in Table 1, and the superiority and inferiority of the effects are clear. That is, ammonium bicarbonate is
Although it may be used as a powder, it can be molded into tablets and simply placed at either end A or B or both ends of the tube.

When ammonium bicarbonate is sealed with approximately 800 square tablets at one end of the tube, the effect extends to the contact surface of the cap on the other side, but when Daikan was used in powder form, no W! In some cases, some rust occurred on the contact surface of the cap. The distance over which the rust prevention effect of ammonium hydrogen carbonate extends is:
The results of this experiment revealed that the length was more than 7 m.

It is clear that one of the excellent effects of ammonium hydrogen carbonate is its high vapor pressure. Therefore, the sustainability of the effect is sufficiently practical.

In addition, because this test was conducted during the rainy season and high humidity air was enclosed, all of the blank tests were rusted, and the Daikan-filled tubes were also considerably rusted, suggesting that there was condensation inside the tubes. In addition, Daikan has a small amount of volatilization, and absorbs moisture inside the tube, resulting in a slight increase in weight.

Effects of the Invention Based on the above results, the effects of the method for preventing rust on the inner surface of steel pipes using ammonium hydrogen carbonate are as follows.

If ammonium bicarbonate is made into a tablet, one end of the tube will have 1
~2? By leaving it in place and sealing it, you can prevent the steel pipe from rusting for a long time. This eliminates the drawbacks that arise when using Daikan to evenly distribute powder inside the tube. That is, (1
) Excessive use beyond the specified limit can be prevented. (2) It is safe because the powder does not scatter. (3) Strong rust prevention effect.

(4) Because the cost of chemicals is low and the workability is simple,
The cost of the rust prevention work itself is also reduced.

Among the sub-agents: 1) Akira Sub-agent Ryo Hagi Hara -

Claims (1)

[Claims] A method for preventing rust on the inner surface of a steel pipe, which is characterized by filling and sealing ammonium hydrogen carbonate inside the pipe.