JPS60248887A - 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 crabonate 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 carbonate. This gasifiable rust preventive has high vapor pressure, produces an innediate 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 Volatile rust inhibitors [volatile Corros
ion engineering inhibitor (abbreviation v, c, ■,)
] is commonly used. Dicyclohexylammonium nitrite (abbreviated as Daikan) is usually used as a volatile rust preventive.

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 steel pipes arrive at a factory with such a weft, the internal die force is blown out with compressed air immediately before they are subjected to subsequent processing operations.

This is to prevent the generation of toxic gas odors due to high temperatures such as welding, cutting, and annealing.

When inspecting after removing the internal die can in this way,
Rust is often observed, especially at the tube ends and the contact surface with the cap.

The following are some 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 30 ml of Daikan per 1 m3, but the rust prevention effect is usually within 60 cJn from where Daikan is present.

Here, consider a @pipe with an inner diameter of 50 mm and a length of 10 m.
For example, the internal volume is approximately 201, so the required amount is 600.
It becomes 9. However, since it is necessary to spread this evenly within the pipe, it is inevitably sealed using the above-mentioned spray method, but the reality is that the noise is 30 to 60 times louder.

(2) Die-can blowing work When blowing powder into a die-can, it is generally carried out using the Sugerei method described above, but the work area is filled with the powder blown out from the end of the tube. Daikan powder is suitable for eyes, nose,
irritates the throat. Also, although it is said to be low, LD5
It has a toxicity of approximately 200 μ/9 at 0.

Dust-proof glasses and masks are usually worn during this work, but the problem still remains and may affect other workers. 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 standpoint, there are problems such as poisoning, ignition, and
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-prevented. The vapor pressure of Daikan is as low as 1710 of mercury at room temperature, so it maintains its effect 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 will 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 with 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 cost of enclosing the die can is high.

The problem that the invention aims to solve The objectives of the present invention are cost, safety, and workability.

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 rust prevention properties compared to 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 carbonate inside the pipe.

Function: The ammonium carbonate used in the present invention has a rust-preventing effect that far exceeds that of Daikan in a closed container. Also,
Carbon ammonium has high vapor pressure, excellent fast-acting properties, and low cost. 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 5T used as alloy steel pipe for boiler and heat exchange
BA 24 (J-8 G5462) grade, outer diameter 48
．． 6 front, thickness 57 mm, inner diameter 41.2 mm, length 7. OO
Rust prevention tests were conducted on 14 Ota steel pipes.

The contents of the rust prevention test are as shown in Table 1, and the conventionally used Daican and the ammonium 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. Also,
2 A normally used polyethylene camp was used as a tightly sealed tube camp. A pressure test was conducted on this cap, but even with a pressure of α1 kg/1M71p, the seal could only be maintained at normal pressure after a few minutes.

After enclosing anti-rust agent, Steel W was stored in a warehouse for about five months, and was kept in the hold for a total of ten days until it arrived at the inspection site.

The measurement results and evaluation are also shown in Table 1. From the results in Table 1, the superiority and inferiority of the effects are clear. In other words, ammonium carbonate can be used as a powder, but it can be molded into tablets, and the end of the tube is A.

There are only some or both ends of B. With ammonium carbonate, when a tablet of approximately 800 ml is placed at the end of a tube, the effect extends to the contact surface of the cap on the opposite side, but when Daikan is used in powder form, the cap does not come off in any case. Some rust occurred on the contact surface. The results of this experiment revealed that ammonium carbonate has a rust-preventing effect over a distance of 7 meters or more.

In this way, one of the excellent effects of ammonium carbonate is
Although it is clear that the vapor pressure is high, the current cap that has some drawbacks in sealing is used, and the wood still remains after about 6 months, so the durability of the effect is sufficient for practical use. It is.

In addition, because this test was conducted during the rainy season and high humidity air was enclosed, all the tests were rusted, and the pipes containing Daican were also rusted considerably, suggesting that there was condensation inside the pipes. 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 carbonate are as follows.

If ammonium carbonate is made into tablets, 1 to 2 tablets per 10,000 tube ends.
? By leaving it in place and sealing it, you can prevent the steel pipe from rusting for a long time. This f′1. With Daikan, it is possible to eliminate the drawbacks caused by uniformly dispersing the powder inside the tube. That is, (
1) Overuse beyond serious illness can be prevented. (2) It is safe because the powder does not scatter. (3) Strong rust prevention effect. (4) Since the cost of chemicals is low and the production process is simple, the cost of rust prevention work itself is also reduced.

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

Claims (1)

[Claims] A rust prevention method for the inner surface of steel pipes, which is characterized by enclosing ammonium carbonate inside the pipe and sealing it.