How to extend the service life of ERW pipe?

What is ERW pipe?

ERW pipe (Electric Resistance Welded Pipe) is a welded steel pipe made by high-frequency current heating and pressure welding. It is widely used in oil, natural gas, construction, machinery and other fields.

The core principle of ERW pipe production: 

Cold bend the steel strip (coil) into a tube, use high-frequency current to pass through the edge of the tube blank to instantly heat it to a molten state, and then pressurize and weld it through the extrusion roller. Its weld is formed by melting the steel strip body parent material, which makes its mechanical strength better than that of general welded pipes. No welding wire or filler material is required, which belongs to the solid-state welding process.

However, in actual use, the service life of ERW pipe will be affected by many factors. If it is used improperly or poorly maintained, its performance may decline and premature damage will not only increase the replacement cost, but also affect the normal operation of the entire system. Therefore, it is essential to master the method of extending the service life of ERW pipe.

The factors affecting the life of ERW pipelines are mainly:

1. Internal factors

Raw material quality:
Material is the basis of ERW pipeline quality and directly affects its service life. The chemical composition and microstructure of ERW pipes directly affect their corrosion resistance and mechanical properties. High-quality ERW welded pipe materials usually have better corrosion resistance, wear resistance and strength, thereby extending the service life. Inclusions, pores and other defects in the raw materials will reduce the strength and toughness of the welded pipe, thereby affecting its service life.

ERW pipes made of high-strength materials can withstand greater pressure and external forces. In the long-distance transportation of oil and natural gas, the use of high-strength ERW pipes can effectively resist internal pressure and formation stress. Materials with strong corrosion resistance can remain stable in harsh environments. For example, when transporting corrosive media in chemical pipelines, stainless steel ERW pipes can prevent corrosion.

Design and manufacturing process:
Pipeline design includes design parameters such as pipe diameter, wall thickness, and degree of bending. Unreasonable design will increase the scouring and wear of the fluid on the welded pipe and reduce the service life.

The manufacturing process is also critical. Strictly control the welding process and optimize the high-frequency welding (HFW) process parameters. The welding quality determines the strength and sealing of the weld. High-quality welding can make the weld close to the strength of the parent material and reduce the risk of leakage. The effect of internal burr removal also affects the fluid resistance and corrosion inside the pipeline. Thoroughly removing internal burrs can reduce fluid turbulence and reduce erosion and corrosion of the pipe wall.

2. External factors

Use environment:
The use environment has a significant impact on the life of ERW pipes. In high temperature environments, the strength of the pipe will decrease. For example, in high-temperature steam transmission pipelines, excessively high temperatures may cause ERW pipes to creep and shorten their service life. Humid environments are prone to corrosion, especially when laying ERW water supply and drainage pipes in humid underground areas, anti-corrosion measures must be taken.

Corrosive media:
The corrosiveness of the medium cannot be ignored. Transporting highly corrosive media, such as sulfuric acid, hydrochloric acid or seawater environments, will accelerate the corrosion of the pipeline.

Installation and maintenance:
Installation and maintenance are equally important. Improper installation, such as loose pipe connections and uneven force, will cause local stress concentration and lead to pipe damage. Lack of regular maintenance, failure to promptly detect and deal with pipeline corrosion, wear and other problems will cause small problems to gradually expand, and ultimately affect the service life of the ERW pipe.

Methods to extend the service life of ERW pipes:

To extend the service life of ERW pipes, it is necessary to comprehensively start from material selection and quality control, reasonable design and installation, anti-corrosion treatment, use environment control, regular maintenance and storage, etc.:

1. Material selection and quality control

Select high-quality materials:
Select materials with high strength, corrosion resistance, wear resistance and other excellent properties to make welded pipes, which fundamentally improves their service life.
Pay special attention to the quality of the welding part, select good quality welding materials, improve the quality of the weld, and reduce the risk of leakage and cracking.

Strictly control the production process:
In the production process of ERW welded pipes, the quality of raw materials must be strictly controlled to ensure that the manufacturing process of welded pipes meets relevant standards and requirements. Priority should be given to high-quality steel with low sulfur and low phosphorus (such as API 5L Gr.B, ASTM A53) to reduce the risk of welding defects. Ensure that the edge of the steel strip is clean to avoid oxide inclusions affecting the quality of the weld.

Optimize high-frequency welding parameters, and the current, voltage, and welding speed must be matched to avoid incomplete penetration or overheating embrittlement. Online heat treatment (normalizing or annealing) after welding eliminates residual stress and improves weld toughness. Weld inspection: Ultrasonic flaw detection (UT) and eddy current testing (ET) ensure that there are no defects such as cracks and pores.

Regularly conduct quality inspections on the ERW pipe production line to promptly discover and deal with problems in the production process to ensure the quality of the finished welded pipe.

2. Reasonable design and installation

Optimize pipeline design:
The pipeline design should be reasonable, including pipe diameter, wall thickness, degree of bending, etc., to reduce the scouring and wear of the fluid on the welded pipe.

The pipeline layout should be as simple as possible to avoid too many elbows and joints to reduce fluid resistance and wear.

Correctly install the welded pipe:
The installation of ERW welded pipes should follow relevant standards and specifications to ensure installation quality.
During the installation process, pay attention to protecting the welded pipe to avoid mechanical damage during transportation and installation.

3. Daily maintenance and care

Regular cleaning:
Regularly wipe the outer surface of the welded pipe with a soft cloth, or use a mild detergent for cleaning.
Avoid using strong acids, alkalis or corrosive cleaning agents to avoid damage to ERW welded pipes.

Remove dirt and sediment:
During the fluid transportation process, impurities and scale may be deposited inside the ERW welded pipe, affecting the fluid flow rate and the service life of the welded pipe.
The pipeline should be cleaned and descaled regularly. High-pressure water jet cleaning, chemical cleaning and other methods can be used to effectively remove dirt and sediment in the pipeline.

Lubrication and anti-corrosion treatment:
For key parts of ERW welded pipes, such as valves, lubrication should be carried out regularly to reduce friction and wear.

Anti-corrosion treatment of ERW welded pipes is of utmost importance. Commonly used anti-corrosion methods include coating anti-corrosion and cathodic protection. Coating anti-corrosion is to form a protective layer by coating anti-corrosion coating on the surface of the welded pipe to isolate the ERW pipe from direct contact with the corrosive medium; cathodic protection uses electrochemical principles to make the welded pipe a cathode, thereby slowing down or preventing corrosion.

Appearance and weld inspection:
Periodically inspect the appearance of ERW welded pipes to check for cracks, deformation, rust and other problems.

The weld is the weak link of the welded pipe and the part most prone to problems. Therefore, regular inspection and maintenance of the weld is essential. Visual inspection, ultrasonic flaw detection, X-ray flaw detection and other methods can be used to carefully inspect the weld to ensure the quality of the weld. Once cracks, unfused, slag inclusions and other defects are found in the weld, they should be repaired or replaced in time.

4. Scientific operation and storage

Scientific operation:
During transportation, installation and use, the operating procedures should be followed to avoid mechanical damage and damage caused by improper operation.

Pay attention to the equipment status and temperature, and clear the discharge pipe in time to prevent blockage and water accumulation from causing equipment loss.

Proper storage:
For ERW welded pipes that are not used for a long time, they should be properly stored to avoid moisture, corrosion or mechanical damage.

The storage environment should be kept dry and ventilated, and the storage status of the welded pipe should be checked regularly.

Conclusion:

The life of the ERW pipe can be effectively extended by selecting high-quality materials, reasonable design and installation, daily maintenance and care, anti-corrosion treatment, and scientific operation and storage. The implementation of these measures will not only help reduce maintenance and replacement costs, but also improve the reliability and safety of ERW welded pipes.

Read more: SAW vs ERW and EFW Welded Steel Pipe or Carbon Steel ERW Pipe Specification