Because oil and gas pipelines are buried underground for a long time, they are very prone to corrosion problems due to soil, moisture and other factors. At present, pipeline corrosion in the petrochemical industry is mainly divided into two types:
1) External corrosion, the so-called external corrosion specifically refers to the corrosion caused by the connection between the metal material of the pipeline and the corrosive medium in the external environment.At the same time, since some pipelines have an insulation layer outside, moisture may accumulate under the insulation layer due to other factors (sometimes due to the high temperature of the medium in the pipe, the external moisture may be heated) to cause corrosion.
2) Internal corrosion, the so-called internal corrosion specifically refers to the corrosion of the inner layer of the pipeline. The types of internal corrosion that occur are different depending on the properties of the fluid in the pipeline. Including acid corrosion, corrosion caused by chloride ions, microbial corrosion, stress corrosion, welding corrosion and so on.
Reasons Affecting Oil and Gas Pipeline Corrosion
1. External factors.
Because oil pipelines are generally buried in the natural environment, there are many factors related to the corrosion of oil pipelines, such as environmental temperature, pressure and humidity, and they change due to the seasonal changes of the environment. High temperature, cold and large temperature difference will cause the pipeline to be damaged and corroded. If there is acidic soil in the soil, special microorganisms will cause damage to the oil pipeline.
2. Construction environmental factors
During the construction of oil pipelines, there may be many construction problems. Improper construction will have a certain impact on the later use of oil pipelines. In the construction of oil pipelines, the raw materials of oil pipelines, the construction process of personnel and related construction techniques all affect the anti-corrosion ability of oil pipelines to a large extent. Especially in the construction of oil pipelines, due to the unprofessional construction of the construction personnel and the non-compliance with the construction standards during the construction process, serious safety hazards will be buried in the later use.
Types of Corrosion in Oil and Gas Pipelines
1. Comprehensive corrosion
Uniform corrosion on the right foot. Corrosion is basically the same degree of corrosion that occurs on a larger area of the pipeline. It is the least dangerous form of corrosion.
① In engineering, it is often necessary to give enough corrosion allowance to ensure the mechanical strength and service life of the material.
② Uniform corrosion is usually uated by the corrosion depth of the corrosive medium to the metal material or the reduction of the wall thickness of the metal component (called the corrosion rate) per unit time.
2. Local corrosion
Localized corrosion, also known as non-uniform corrosion, is far more harmful than uniform corrosion, because localized corrosion is difficult to predict and prevent, often causing sudden damage to metal components without warning.
3. Stress Corrosion
The fracture failure of steel pipe materials under the combined action of tensile stress and specific corrosive media is called stress corrosion cracking. Stress corrosion cracks are dendritic and generally develop in the direction perpendicular to the tensile stress. The microscopic morphologies of cracks include transcrystalline, intercrystalline (along-crystalline) and a mixture of both. The main source of stress is the residual stress during welding, cold working and installation.
Anticorrosion technology of oil and gas pipelines
1. Anti-corrosion coating.
The main purpose is to separate the pipeline from the soil by using some materials to further ensure that the pipeline can not be corroded by the soil, which is of great significance for extending the service life of the pipeline in an all-round way. At present, the anti-corrosion layer mainly includes: oil anti-corrosion layer, polyethylene anti-corrosion layer, epoxy anti-corrosion layer and composite anti-corrosion layer.
2. Proper selection of piping materials
There are obvious differences in the corrosion resistance of pipelines of different materials, so it is necessary to strictly check the effective selection of pipeline materials, so that the selected pipeline can reduce the probability of corrosion problems during its use.
3. Anti-corrosion treatment in full immersion area
The full immersion area of the oil pipeline is a key point that needs to be paid great attention. The effective anti-corrosion operation in the full immersion area should focus on strengthening the all-round treatment of the pipeline, so as to make the anti-corrosion operation more reasonable and avoid obvious anti-corrosion loopholes in any link. The full immersion area can be treated with cathodic protection technology and coating protection. It is necessary to focus on some key connection parts that may be involved in the pipeline to avoid the formation of relatively severe corrosive phenomena in this area. At the same time, the welding seam of the pipeline should also be checked.
Note: seamless pipes are mostly used for oil and gas transmission pipelines, because seamless steel pipes have hollow sections and are directly pierced and rolled from round steel without welds.Therefore, seamless pipes are widely used as pipelines for transporting fluids, such as transporting oil, natural gas, gas, water and certain solid materials.
1) External corrosion, the so-called external corrosion specifically refers to the corrosion caused by the connection between the metal material of the pipeline and the corrosive medium in the external environment.At the same time, since some pipelines have an insulation layer outside, moisture may accumulate under the insulation layer due to other factors (sometimes due to the high temperature of the medium in the pipe, the external moisture may be heated) to cause corrosion.
2) Internal corrosion, the so-called internal corrosion specifically refers to the corrosion of the inner layer of the pipeline. The types of internal corrosion that occur are different depending on the properties of the fluid in the pipeline. Including acid corrosion, corrosion caused by chloride ions, microbial corrosion, stress corrosion, welding corrosion and so on.
Reasons Affecting Oil and Gas Pipeline Corrosion
1. External factors.
Because oil pipelines are generally buried in the natural environment, there are many factors related to the corrosion of oil pipelines, such as environmental temperature, pressure and humidity, and they change due to the seasonal changes of the environment. High temperature, cold and large temperature difference will cause the pipeline to be damaged and corroded. If there is acidic soil in the soil, special microorganisms will cause damage to the oil pipeline.
2. Construction environmental factors
During the construction of oil pipelines, there may be many construction problems. Improper construction will have a certain impact on the later use of oil pipelines. In the construction of oil pipelines, the raw materials of oil pipelines, the construction process of personnel and related construction techniques all affect the anti-corrosion ability of oil pipelines to a large extent. Especially in the construction of oil pipelines, due to the unprofessional construction of the construction personnel and the non-compliance with the construction standards during the construction process, serious safety hazards will be buried in the later use.
Types of Corrosion in Oil and Gas Pipelines
1. Comprehensive corrosion
Uniform corrosion on the right foot. Corrosion is basically the same degree of corrosion that occurs on a larger area of the pipeline. It is the least dangerous form of corrosion.
① In engineering, it is often necessary to give enough corrosion allowance to ensure the mechanical strength and service life of the material.
② Uniform corrosion is usually uated by the corrosion depth of the corrosive medium to the metal material or the reduction of the wall thickness of the metal component (called the corrosion rate) per unit time.
2. Local corrosion
Localized corrosion, also known as non-uniform corrosion, is far more harmful than uniform corrosion, because localized corrosion is difficult to predict and prevent, often causing sudden damage to metal components without warning.
3. Stress Corrosion
The fracture failure of steel pipe materials under the combined action of tensile stress and specific corrosive media is called stress corrosion cracking. Stress corrosion cracks are dendritic and generally develop in the direction perpendicular to the tensile stress. The microscopic morphologies of cracks include transcrystalline, intercrystalline (along-crystalline) and a mixture of both. The main source of stress is the residual stress during welding, cold working and installation.
Anticorrosion technology of oil and gas pipelines
1. Anti-corrosion coating.
The main purpose is to separate the pipeline from the soil by using some materials to further ensure that the pipeline can not be corroded by the soil, which is of great significance for extending the service life of the pipeline in an all-round way. At present, the anti-corrosion layer mainly includes: oil anti-corrosion layer, polyethylene anti-corrosion layer, epoxy anti-corrosion layer and composite anti-corrosion layer.
2. Proper selection of piping materials
There are obvious differences in the corrosion resistance of pipelines of different materials, so it is necessary to strictly check the effective selection of pipeline materials, so that the selected pipeline can reduce the probability of corrosion problems during its use.
3. Anti-corrosion treatment in full immersion area
The full immersion area of the oil pipeline is a key point that needs to be paid great attention. The effective anti-corrosion operation in the full immersion area should focus on strengthening the all-round treatment of the pipeline, so as to make the anti-corrosion operation more reasonable and avoid obvious anti-corrosion loopholes in any link. The full immersion area can be treated with cathodic protection technology and coating protection. It is necessary to focus on some key connection parts that may be involved in the pipeline to avoid the formation of relatively severe corrosive phenomena in this area. At the same time, the welding seam of the pipeline should also be checked.
Note: seamless pipes are mostly used for oil and gas transmission pipelines, because seamless steel pipes have hollow sections and are directly pierced and rolled from round steel without welds.Therefore, seamless pipes are widely used as pipelines for transporting fluids, such as transporting oil, natural gas, gas, water and certain solid materials.
