Line Pipe


Line Pipe

A line pipe is a steel pipe used for transporting oil, gas, or water over long distances. It is made from high-strength steel that can withstand the high pressures and temperatures involved in transportation. Line pipes must meet strict standards set by organizations like the American Petroleum Institute (API). API 5L is a common standard for this. They are produced in various sizes, from small-diameter pipes used for residential plumbing to large-diameter pipes used for major pipelines. They can be either seamless or welded. A seamless line pipe is made from a single piece of steel, while the second type is made by joining steel plates together. Line pipes have properties like diameter, wall thickness, and steel grade that determine the strength and durability of the line pipe. The most common steel grades used for line pipes are Grades B through X80. Higher grades of steel provide better strength, reliability, and rust resistance but are more expensive.

Why Choose TUSPIPE?


Since 1998, Tianjin United Steel Pipe Co., Ltd (TUSPIPE) has been committed to supplying high-quality line pipes.

The main products are API 5L Line Pipe, API 5CT Casing Pipe, and Tubing. And also, Tianjin United Steel Pipe Co., Ltd supplies slotted liner, compressor tubes, transmission shaft tubes, torque tubes, piling pipes, sprinkler pipes, boiler pipes, roller pipes, etc. Production standards include API SPEC 5CT, API SPEC 5L, JIS G 3444, JIS G 3452, ASTM A53/A53M, ASTM A135, ASTM A252, ASTM A500, ASTM A795, AS/NZS 1163, AS/NZS 1074, AS/NZS 1396, EN 10217, EN 10219, EN 10255, UL 852, FM 1630, GB/T 9711, GB/T 3091, GB/T 13793, GB/T 19830, YB/T 5209, and SY/T 5768.

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Production Standards of Line Pipe

API 5L line steel pipe manufacture certificate

API 5L is the most common specification for line pipes, covering seam steel pipes that are intended for conveying petroleum, H2O, and fuel in the natural gas and petroleum industries. API 5L pipes are manufactured as per specifications established by American Petroleum Institute (API) for standard pipelines. The most common versions of API 5L are API 5L X70 PSL1 & PSL2 and API 5L X65 PSL1 & PSL2. According to international standard ISO 3183 “Petroleum and natural gas industries-Steel Pipe for pipelines-Technical Delivery Conditions,” different grades of line pipes can be supplied: L175 or A25, L210 or A, L290 or X42, L360 or X52, L415 or X60, l450 or X65 GR.B. In addition to the different grades we can supply different steel pipelines: ERW (Electric resistance welded), SSAW (Spiral submerged arc welded) and LSAW (Longitudinal submerged arc welded). According to the requirements of end users, different surface finishes can be.

Types of Line Pipe

Pipelines can be categorized into different types. The following pipelines are classified according to the type of fluids and items transported. It is important to read the following for an understanding of each type.

- Water and Drain Line Pipe

This type is used to carry H2O from one location to another. They are typically made of metal or plastic, and they are usually buried underground. These are typically coated with a material that helps to prevent rusting. In addition, such pipelines may be equipped with fittings that help to connect to other types of pipes or fixtures. They are an essential part of any plumbing system, and they are typically used in residential, commercial, and industrial applications.

- Oil Line Pipe

This type is defined as having the advantage to be used to carry petroleum products such as crude oil and natural gas. They are typically made of steel or iron, which can be susceptible to rusting. To protect the pipes from rusting, a coating is often applied. This coating can be made of various materials, including plastic and resin. Once the petroleum products have been transported through the pipelines, they can then be refined into useful products such as gasoline and diesel fuel.

- Gas Line Pipe

The specification of types of pipelines is that it is used to carry and transport natural gas. It is generally made of steel, which is a strong and durable material. However, over time, steel can start to corrode and weaken. To protect the pipelines from rust, it is often coated with a layer of plastic or other material. Such pipelines are typically buried underground, but they can also be installed above ground. The pipelines must be properly maintained to ensure that it does not leak or burst, which could pose a serious safety hazard.


You can check the size range of tubes in ISO 4200 and ASME B36.10M. These are the standardized values for the specified outside diameters and specified wall thickness of these tubes. ISO 4200 covers plain-end steel tubes, while ASME B36.10M covers seamed and seamless wrought steel pipes. You should refer to these standards when checking these.


Chemical composition of line pipe

- API 5L PSL-1 Chemical Component

Chemical Composition of API 5L PSL-1 Line Pipe

- API 5L PSL-2 Chemical Component

Chemical Composition of API 5L PSL-2 Line Pipe

Line Pipe Coatings

- Fusion Bonded Epoxy (FBE) Coating

Fusion-bonded epoxy (FBE) is a high-grade type of coating that has many benefits, especially in a project that involves pipelines that need to be constructed. It has excellent pressure pipe adhesion and good chemical media corrosion, temperature, cathodic peel, aging, and soil stress resistance, among other properties. This makes it suitable for most soil environments and directional drilling through clay soils because it operates over a wide temperature range (standard FBE operates between -30°C and 100°C). In addition, it is also resistant to UV radiation, making it an ideal choice for exposed pipelines. Fusion-bonded epoxy is a cost-effective solution that provides long-term protection increasing the life of the pipelines.

- Three Layers Polyethylene (3PE) Coating

Three-layer polyethylene (3PE) anticorrosive coating is a kind of high-performance anti-corrosion coating. It combines the advantages of epoxy powder FBE and two-layer PE coating. FBE is the primary anticorrosive agent. PE is good at resisting H2O penetration and is primarily used to protect FBE from mechanical damage. The three-layer polyethylene coating system has superior mechanical properties that match the properties of the coating material, and it can withstand increasing temperatures of up to 50°C (low and medium-density polyethylene) or 70°C (high-density polyethylene). 3PE anticorrosive coatings have been widely used in the fuel pipelines industry because they are resistant to rust and have a low friction coefficient, electrical insulation, and mechanical protection. They are also suitable for buried pipelines in other environments such as urban gas pipelines, H2O supply pipelines, sewerage pipelines, and heating pipelines.

- Three Layers Polypropylene (3PP) Coating

The three-layer polypropylene anticorrosive coating (3PP) is made up of a base layer of epoxy powder, an intermediate layer of binder, and an outer layer of polypropylene (PP) jacket. The 3PP takes all of the benefits of the 3PE and improves its temperature performance operation significantly. 3PP coating is primarily used as an anticorrosive layer for conveying high-temperature mediums and as an anticorrosive layer in desert areas with high surface temperatures and long periods of sunshine. The improved operating temperature performance of the 3PP makes it ideal for use in pipelines carrying hot fluids or in desert climates where the ground surface can reach high temperatures. The 3PP coating has the capability to be resistant to most chemical attacks, making it an ideal choice for use in chemical processing plants or other industrial applications where the ability to endure chemical stress is important.

- Epoxy Coal Pitch Anticorrosion Coating

A silicone erosion-resistant coat is composed of a number of layers, each with its own unique properties that support the overall performance of the coating. The steel sleeve provides a durable base for the coating, while the silicone erosion-resistant coat protects against rust and heat damage. The hard silicon calcium tile insulation layer helps to regulate temperature and prevent heat loss, while the galvanized iron wire reinforcement layer adds strength and stability. Finally, the aluminum silicate fiber cloth waterproof layer protects against moisture damage, while the titanium aluminum alloy ensures durability and resistance to wear and tear. When all of these layers are combined, they create a coating that is able to withstand extreme temperatures and provide superior protection against a variety of environmental hazards.

- Silicone Anticorrosion Coating

Silicone erosion-resistant layer, hard silicon calcium tile insulation layer, galvanized iron wire reinforcement layer, aluminum silicate fiber cloth waterproof layer, steel sleeve, and titanium aluminum alloy and silicone coating surfaces. Silicone resin, ceramic powder, talcum powder, mica powder, aluminum oxide powder, and titanate coating curing are used to create the silicone erosion-resistant\ layer. With erosion-resistant, heat preservation, waterproofing, and external protection capabilities, its silicone erosion-resistant layer can withstand temperatures up to 600°C, making it suitable for transporting 550°C high-temperature medium insulation pipelines.

- Internal Coating

Internal coating for steel pipelines is a method where a paint system is applied to the inner wall of the pipelines. It is important internal steel pipeline coatings protect the steel from rusting. The main purpose of the internal coating is erosion-resistant protection. This involves spraying coating material on the inner surface of the pipes. Steel pipelines are extensively used in a project in industries such as H2O, fuel, & sewage, and chemical plants, as they are resistant to chemicals and high temperatures. The internal coating reduces friction loss and increases the flow of fluid or petroleum inside the pipeline. It also protects the steel from abrasion and rusting and reduces or eliminates build-up on the inner wall of the pipe. Internal pipeline coating is an essential procedure that helps to increase the lifespan of steel pipelines.

What is the Performance of Line Pipe Coating?

- Thickness Requirements for Pipeline Anti-corrosion Coating

Nominal DiameterEpoxy Coating/μmAdhesive Coating/μmMin. Thickness of PE Coating
Common (mm)Enhanced (mm)

- Performance Index of Fused Epoxy Coating

No.ItemPerformance Indicators
1Adhesion, Classification≤2
2Cathode Racking (65℃,48h)/mmRacking Distance ≤8
3Cathode Racking (65℃,30d)/mmRacking Distance ≤15
4Anti-bending (-20℃,2.5°)No Crack

- Performance Index of Two-Layer Structure Adhesive

No.ItemPerformance Indicators
1Density (g/cm²)0.920 – 0.950
2Melt Flow Rate (190℃,2.16kg)(g/10min)≥0.7
3Vicat Softening (℃)≥90
4Brittle Temperature (℃)≤-50
5Oxidation Induction Time (200℃)≥10
6Moisture Content %≤0.1
7Tensile Strength Mpa≥17
8Elongation after Fracture %≥600

- Performance Index of Two-Layer Structure Adhesive

No.ItemPerformance Indicators
1Tensile StrengthAxial Direction, Mpa≥20
Circumferential Direction, Mpa≥20
Deviation, %≤15
2Elongation after Fracture, %≥600
3Indentation Hardness (mm)23℃≤0.2
50℃ or 70℃≤0.3
4Endurably Environmental Stress Cracking (F50),h≥1000

What Tests We Perform on Line Pipes?

Heat Analysis

To perform a heat analysis, the raw material must first be gathered from the coil. The samples shall be sent to our QC department to complete the chemical and physical tests. Then, the engineers will compare the test results and the required parameters. If the raw material meets all requirements, it can be used to manufacture pipelines. Heat analysis is an important standard control step that helps to ensure that the raw material meets all safety and performance standards.

Tensile Test

A tensile test is a common type of mechanical test that measures the strength and ductility of a pipe’s body and weld seam. Welded products are often tested in this way to ensure that it meets the standards. The basic principle of the tensile test is to apply a force to the sample until it breaks. The force is typically applied using a testing machine, and the resulting data is used to calculate the yield strength and elongation of the material. To perform a tensile test on weld tubing, a sample of the body is first cut from the pipe’s body, but it can also be done on the seams. The ends of the sample are then machined to create two smooth, parallel surfaces. Next, the testing machine is used to apply a force to the ends of the sample. As the force is increased, stress builds up in the material until it finally reaches its breaking point. By measuring the amount of force required to break the sample, as well as the elongation of the welded joint, it is possible to determine the yield strength and ductility of weld tubing.

Bend Test

Tubings are joined along its longitudinal seam, which makes it susceptible to weld defects that can lead to leaks or weld failure. One way to test for these defects is to perform a bend test. It is a destructive test method used to evaluate weld tubes. Pipes are first joined together and then placed on a jig that holds them at the desired angle. A load is then applied to the pipes until it reaches the point of failure. The results of the test can then be used to assess the standard of the weld and the overall strength of the pipes. Bend tests are an essential part of quality control, and they help to ensure that the finished product meets all safety and performance standards.

Flattening Test

A weld line pipe is used to transport liquids and petroleum over long distances. The joined seam of can be a source of weakness, and it is important to test this seam to ensure that it can withstand the pressure of the contents. The flattening test is one way to test this seam of a line pipe. To perform the flattening test, the seam is placed under pressure until it breaks. The pressure at which the seam breaks is an indication of its strength. The flattening test is an important part of quality control, and it helps to ensure that the seams can withstand the pressure of the contents.

Hydrostatic Test

A hydrostatic test is a way to ensure that pipes are leak-free and able to withstand the internal pressure they will experience in service. The test involves filling the pipes with H2O and applying pressure until it reaches the specified test pressure. If there are no leaks, the pressure is then released and H2O is drained from the pipes. In addition, hydrostatic testing can also identify potential failure points in the pipe’s body itself. Hydrostatic testing is often used on the installation of pipes, as well as on those that have undergone repairs, such as welding or replacement of a section of the pipes. By subjecting the pipes to pressure, any weak spots will be revealed so that they can be repaired before the pipes go into service.

Metallographic Test

Metallographic testing involves inspecting a seam or weld for flaws at a microscopic level. This type of testing is often used in the quality control of manufacturing. Several steps must be followed to properly perform metallographic testing. First, the seam or weld must be prepared by grinding and polishing it to a mirror-like finish. Next, the seam or weld must be examined under a microscope for any signs of flaws. Finally, the results of the examination must be documented. Metallographic testing is an important step in ensuring the caliber of the line pipe. By carefully examining seams and welds, manufacturers can ensure that their products meet the highest standards.

Visual Inspection

Visual inspection is the most common method used to examine these tubes. This involves looking at the pipe’s body, coating, and surface for any irregularities. The pipes should be free of any dents, gouges, or other damage. The coating should be smooth and evenly applied, with no cracks or bubbles. The surface of the pipes should be free of any rust, scale, or other corrosion. If any of these defects are present, it may be necessary to repair or replace the pipes.

Diameter and Out-of-Roundness Measurements

Diameter and Out-of-Roundness Measurements are critical checks on these tubes. There are various ways to measure these characteristics, but the most common method is with calipers or a micrometer. First, the line pipe must be properly supported so that it is straight and level. Next, the calipers or micrometer site should be at the top of the line pipe and slowly rotated around the circumference. The diameter can then be calculated by taking the average of the measurements. For out-of-roundness measurements, the same process is followed but with the calipers or micrometer placed at different points along the length of the line pipe. By carefully following these steps, accurate diameter and out-of-roundness measurements can be made on a line pipe.

Wall Thickness Measurement

There are two types of wall thickness measurement that can be performed on line pipe, one is the manual method and the other is the electronic method. The manual method is where an inspector uses a ruler or tape measure to physically measure the thickness of the wall of the pipes at various points along the length of the pipes. The electronic method is where an electronic device is used to measure the thickness of the pipe’s wall. This type of measurement is more accurate than the manual method and is generally used when more precise measurements are required. There are several different ways to perform wall thickness measurements on tubes, but the most common and widely used method is the electronic method.

Non-Destructive Inspection

NDT or non-destructive testing is a type of test that is used to assess the properties of a material, component, or system without causing damage. NDT is an important control measure in many industries, including fuel services, where it is essential for ensuring the safety and integrity of pipelines. There are many different NDT methods, but ultrasonic testing (UT) is one of the most common. UT uses high-frequency sound waves to detect defects in materials. The sound waves travel through the material and are reflected when they encounter a defect. By analyzing the reflected waves, it is possible to identify the type and location of the defect. NDT is a vital part of standard-checking in fuel services, and UT is an important NDT method for assessing the condition of pipelines.

What is the Difference between Seamless Line Pipe and Welded Line Pipe?

Line pipes are appropriate for a range of standards. According to consumer needs, production meets the line pipe of various standards. We are usually made according to metallurgical requirements that were developed by the American Petroleum Institute (API). API 5L Specifications cover seamless and welded pipes suitable for use in conveying H2O, fuel, and other liquefied media. It is used in line pipe production worldwide. Pipelines are made in a wide variety, varying in dimensions from 2 to 24 inches. Depending on the customer’s needs, pipeline manufacturers can produce either seamless or welded pipes. The main difference between the two is that the latter has a seam that is created during the manufacturing process, while seamless pipes do not have this seam. Both types of pipes have many uses, and which one is right for a particular project depends on and is limited to several factors such as cost, application, and transportation. Seamless pipes are typically more expensive, but they have superior strength and durability which is preferable for your project. Though the other type is less expensive but may be more prone to leaking. It is also important to note that when choosing, make sure that whatever material you are going to use, is accredited by ASTM. All of these must be considered in accomplishing a CSA. Therefore, it is important to search for consulting services where a trained professional can help you determine which types of pipes are best for your needs.

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