Why is there such a high demand for ASTM A335 pipe in these specific industries? How familiar are you with this type of pipe? What are the most prominent grades within this standard?

The following article will tell you all the things you need to know about this pipe.

Listed topics
What is ASTM A335 pipe
Standard specification
Featured Grades
Referred standards to manufacture this pipe
Raw steel material that used for the production
Tests involved
Things you need to notice when placing an order

What is ASTM A335 pipe?

ASTM A335 pipe, also known as ASME S/A335 Chrome-Moly pipe, is a type of seamless pipe that is specifically designed for high-temperature environments. It can withstand temperatures ranging from 540 to 750 °C.

A335 pipes are commonly referred to as chrome moly pipes due to their high content of Chromium and Molybdenum. The presence of Molybdenum enhances the strength, resistance, elasticity, hardenability, and overall quality of the pipe. It also improves the high temperature resistance and corrosion resistance of the steel. Molybdenum plays a crucial role in preventing softening, limiting grain growth, and reducing the risk of embrittlement.

Key Elements Chromium for this pipe

Chromium is an essential element in the production of stainless steel. When the chromium content exceeds 12%, the material can be classified as stainless steel. Chromium provides excellent resistance to oxidation, even at elevated temperatures. It also improves the hardness, tensile strength, and yield strength of the material at standard temperatures. The composition of chrome-moly pipes makes them ideal for use in power plants, refineries, petrochemical plants, and other oil field services where transportation under high temperatures and pressures is involved.

ASTM A335 Standard Specification and Scope

According to ASTM International, ASTM A335 is the standard specification for seamless Ferritic Alloy-Steel Pipe for High Temperature Service. This specification covers pipes with alloy material, manufactured in seamless form, and with nominal wall and minimum wall thickness. The pipes specified under this standard are suitable for bending, flanging, and other similar processing and formations. Additionally, they are also suitable for fusion welding.

Therefore, ASTM A335 pipe material can also be used in the manufacturing of pipe fittings such as elbows, tees, reducers, and so on.

A335 P5, P9, P11, P22, P91 Pipe Chemical Composition

ASTM A335 Pipe Mechanical Properties

Referred standards ASTM

a. ASTM A999/ A999M, Standard specification for common requirements for stainless and alloy steel pipe
b. ASTM A92, Hardness test methods for steel materials
c. E213, Instructions and practice for ultra sonic testing of steel pipe and tube
d. E309 Eddy-Current Examination methods for steel pipe products
e, E381, Inspection methods for steel bars, beams, profiles, billets and forgings.
f, E527, Numbering metals and alloys practices
g, E570, Instructions for flux leakage examination of ferromagnetic steel pipe products

Nominal Pipe Size

ASME B36.10M dimensions standard for welded and seamless steel pipe

Raw steel material that used for the production

The pipe material can be either hot finished or cold drawn, and the related heat treatment is required for different grades. For Grade P2 and P12, the steel should be manufactured using coarse-grain melting procedures.

Featured Grades P5, P9, P11, P22, P91 pipes

These chrome moly pipes are available in different grades, namely ASTM A335 P9, P11, P22, and P91. In some cases, they may also be referred to as P Grade pipes.

P11, P22, and P91 pipes are commonly used in the power industry and petrochemical plants, while P5 and P9 pipes are typically used in refineries.

ASTM A335 P91 pipes – High Pressure Boiler Pipes

It is important to note that ASTM A335 Grade P91 pipe is a high-grade pipe that is commonly used for high-pressure boilers. P91 pipe is particularly suitable for bending, flanging, and similar operations, including welding. The steel material must adhere to specific chemical composition, tensile properties, and hardness requirements.

There are two variants available: ASTM A335 P91 alloy steel pipe and high-pressure boiler pipes. The range of these pipes is dependent on their size, which is determined by their specific usage. The length of the pipe will be subject to a hydrostatic test, and there will also be a non-destructive examination performed in accordance with the specifications.

As a result, chrome moly pipe is widely used in the power generation and petrochemical industries due to its corrosion resistance, high tensile strength, and ability to withstand high temperatures. This makes it a cost-effective choice for these industries.

Tests involved

Some of the common tests conducted include transverse and longitudinal tension tests, flattening tests, hardness tests, and bend tests. In the case of a material heat test conducted in a blast furnace, it will be performed on 5% of the pipes manufactured from each lot.

If the diameter of the pipe exceeds NPS 25, the diameter to wall thickness ratio should typically be 7.0 or less. For NPS 10 and thicker pipes, the flattening test is only conducted with the approval of the purchaser.

Things you need to notice when placing an order

When sending an inquiry or placing an order for ASTM A335 pipe, the following specifications should be verified:

a. Length per piece and the quantity (Specified in feet, meters or pieces)
b. Material Name (Seamless alloy steel pipe)
c. Grade (P5, P9, P11, P22, P91 pipe etc)
d. Manufacturing types (hot finished seamless or cold drawn seamless)
e. Size to described as below ways:
1. NPS and Schedule Number (According to ASME B36.10, for example NPS 7 inch and Sch 40)
2. OD or ID and nominal or minimum wall thickness (inch or mm)

As we know, line pipe corrosion is an important factor affecting its safety service and service life. It will cause the leakage of oil and gas pipeline, some cases even explosion.
Pipe corrosion has a big threaten to personal safety and environment pollution, so the production of sour service pipe is important. At present, the manufacture inspection standard for acid pipe mainly according to API Spec 5L.

1. Sour Service Pipe Definition

Sour service pipe mainly used in H2S environment. While H2S is a harmful chemicals that mostly easy to generate the corrosion.

According International regulation: When partial pressure of H2S reaches 300 pa, the line pipes used shall have the anti-acid corrosion performance.Sour service pipe includes NACE pipe.

2. How Sour Service Pipe Made

In API Spec 5L, the pipeline steel used for sour service pipe is purity fully-killed steel. (For normal line pipe steel material is grain-killed steel)

It shall be noted that, the high purity of steel can guarantee low S, P and other impurities.

In addition, the standard for the control and inspection of the inclusion shape of pipeline steel for sour service pipe is required. Because the hydrogen induced cracking caused by the inclusion is first determined in its form.

Moreover, As the pipeline steel production generally adopts controlled rolling process. Inclusion occur deformation during the rolling process. It is called linear or long strips in the rolling direction, leading to anisotropy of line pipe steel. Consequently, In order to improve the corrosion resistance of steel line pipe, the slag form should be controlled.

3. Chemical properties of sour service pipe

The content of C, P, S and carbon equivalent in the chemical composition of sour service pipe is relatively low than the normal line pipes, with a strictly control requirements. Especially for the content S, it is extremely harmful element in the corrosion environments, so for sour service pipe should control S maximum 0.002.
API 5L Sour Service pipe Chemical Composition

1). C and carbon equivalent effect to sour pipe

C and carbon equivalent: With the mass fraction of carbon increases, the HIC sensitivity increases. The reduction of carbon and carbon equivalent can improve the H2S corrosion resistance of pipeline steel. And it will generate the harmful martensite formulas, which is very sensitive to H bubbles for the hot rolled steel.

2). P element for sour pipe

The P element is an easy to segregation element, so the increase of phosphorus mass fraction will lead to the increase of banded structure, thus increasing the sensitivity of the steel HIC.

3). S element effect for sour pipe

S element can promote the occurrence of HIC, the higher the sulfur content of the pipe body material, the easier to produce HIC. In addition, the anti – SSC performance of the pipes with high sulfur content is poor.

4). Mn element

In order to ensure the carbon content in high grade pipeline steel, manganese is usually used to improve its strength.  The influence of manganese on HIC resistance of pipeline steel is mainly divided into three kinds:

a. Hot rolled line pipe steel with carbon content of 0.05 % ~ 0. 15 %

When the manganese content is 1. 0 %, the HIC sensitivity will increase abruptly:

b. For the quenched and tempered line pipe steel

When the manganese content reaches 1.6 %, the hic resistance of the steel is not significantly affected by the manganese.

c. In case carbon content is less than 0.02 %

If carbon less 0.02%, even if the manganese content exceeds 2.0%, the pipe still has good HIC resistance.

4. Hardness requirement of sour service pipe

The hardness of the sour service pipe is strict, because the hardness value has a great influence on HIC. The results show that in low and medium strength steels, the higher the material strength, the greater the hardness, the stronger the HIC sensitivity.

5. Corrosion test

In API 5L for sour service pipe, the hardness value of the base metal, weld and hot zone should not exceed 250 HV10. The hardness of the sour service pipe is more strict, because the hardness value has a greater impact on HIC. The research shows that the higher the material strength, the greater the hardness, the stronger the HIC sensitivity in low and medium strength steel.

Mechanical properties of API 5L pipe for sour service

More Technical Articles Related Sour Service Pipe:
PSL1 and PSL2 differences
Nace Pipe
API 5L PSL1 Pipe Specification
Chemical Effects to Pipe

LSAW (Longitudinal double submerge arc welding) carbon steel pipe is a type of SAW pipe made of steel plates that were hot rolled by JCOE or UOE forming technology. JCOE technology represents the shaping and forming processes involved during manufacturing as well as the inner and outer welding and cold expansion carried out after welding.

When compared to UOE LSAW steel pipes, LSAW pipe manufacturers in China can produce more sizes as thus: OD 406 mm – 1620 mm, thickness 6.35 mm – 60 mm, pipe length 2 m – 18 m with the LSAW pipe having superiority.

Octal offers LSAW steel pipe with high quality and competitive prices.

LSAW steel pipe features

Features:

-Large diameter steel pipes
-Thick walls
-High-Pressure resistance
-Low-temperature resistance

Tests:

-Chemical Component Analysis
-Mechanical Properties – Elongation, Yield Strength, Ultimate Tensile Strength
-Technical Properties – DWT Test, Impact Test, Blow Test, Flattening Test
-X-ray Test
-Exterior Size Inspection
-Hydrostatic Test
-UT Test

How to use LSAW welded steel pipe for pipelines

The basic metal and welding metal have been tested according to the specification of the pipe API SPEC 5L, DIN, EN, ASTM, GOST standard and other standards.

Also, LSAW pipe can be welded with flanges, lifting eyes and other parts depending on clients’ requirements.

LSAW pipe are used for conveying fluids like oil, gas and water transportation as well as used for seashore projects and ground constructions. These products are manufactured in China and are exported to other countries like United States of America, Canada, India, Pakistan, Africa, etc.

LSAW steel pipe manufacturing process

The LSAW large diameter steel pipe manufacturing process is explained in the steps below:

1. Plate Probe: This is used for manufacturing the large diameter LSAW joints right after it enters the production line which is the initial full-board ultrasonic testing.
2. Milling: The machine used for milling does this operation through two-edged milling plate to meet the requirements of the plate width and the sides parallel to the shape and degree.
3. Pre-curved side: This side is achieved by using a pre-bending machine on the pre-bending plate edge. The plate edge needs to meet curvature requirement.
4. Forming: After the pre-bending step, in the first half of the JCO molding machine, after stamped steel, it is pressed into a “J” shape while the on the other half of the same steel plate it is bent and pressed into a “C” shape, then the final opening forms an “O” shape.
5. Pre-welding: This is to make a welded pipe steel a straight seam after it has been formed and then use gas welding seam (MAG) for continuous welding.
6. Inside weld: This is done with a tandem multi-wire submerged arc welding (about four wire) on the inner part of the straight seam welded steel pipe.
7. Outside Weld: Outside weld is the tandem multi-wire submerged arc welding on the outer part of the LSAW steel pipe welding.
8. Ultrasonic Testing: Outside and inside of the straight seam welded steel pipe and both sides of the base material are welded with 100% inspection.
9. X-ray inspection: X-ray industrial TV inspection is carried out on the inside and outside using image processing system to make sure there is detection sensitivity.
10. Expansion: This is for accomplishing submerged arc welding and straight seam steel pipe length hole diameter so as to improve the steel tube’s size precision and improve the distribution of stress in the steel tube.
11. Hydraulic test: This is carried out on the hydraulic test machine for steel after expanding by-root test for ensuring the steel pipe meets the standard requirements with the machine having an automatic recording and storage capabilities.
12. Chamfering: This involves the inspection carried out on the steel pipe at the end of the whole process.

Common chemical elements in steel pipes and steel plates

Common chemical elements in steel is C, Mn, S, P, Si, V, Al, Cr, Mo, Ni, B. Considering on different type elements added and percentage properties, steel pipe and steel plate will shows different properties.

Such as for sour service pipe, Nace material pipe and fittings, it has a strict control with C, CEq, P, S, elements content.

Especially for Sulfur (S) content maximum at 0.002 for sour service pipe, but normal pipes S content maximum 0.015. This is a big difference.

The reason that why we need to control S to very less percentage, is S can push HIC happens; More S elements content and it will be more easy to generate HIC, Sulfer is an extremely harmful element.

Effects of each chemical elements on steel

1. Effect of Carbon (C) in steel

What is Carbon (C) effect to steel material?

Carbon is the most important elements found in steel material. Steel material mechanical strength is directly connected with carbon content.

When the carbon element content increased, yield point and tensile strength increased, but the plasticity and impact reduced.

In case carbon content more than 0.23%, steel welding performance will get worse.

So in the low alloy steel structural, to get better welding performances, the carbon content usually less than 0.2%.

Meanwhile, high carbon content also reduces the air corrosion resistance of steel, and the high carbon steel in the open field is easy to rush.

In addition, carbon will increase the cold brittleness and aging sensitivity of steel.

2.Effect of Phosphorus (P) on steel

Effect of phosphorus on steel made various effects in steel pipe and steel plate, in case on different concentrations.

Generally speaking, phosphorus is a harmful element in steel, it will increases the cold brittleness. It makes welding, pending performances get worse, and reduce the plasticity.

Therefore, the content of phosphorus in steel material is usually less than 0.045%, in high-quality steel material grade it is lower.

In higher steel grade, P content is 0.03 to 0.05, if P exceed 0.10 in low alloy high strength steels, it will increase the strength as well as improve the corrosive resistant performances. But the bad part is even the strength increased through P, it becomes brittle, ductility and toughness will reduce.

3.Effect of Sulfur (S) in steel pipe

Effect of Sulfur in steel.

As we know, sulfur is a harmful element. It increase hot brittleness, reduce the ductility and toughness, cause cracks in forging and rolling.

Secondly, Sulfur is bad for welding performance, reduce the corrosion resistance. So it usually requires the sulfur content is less than 0.055%.

For the high-quality of steel, it requires S should be less than 0.04%. By adding 0.08-0.2% sulfur could improve cutting performance, which often called easy cutting steel.

So even S is a harmful element, if content less than 0.05%, it would be accept in general applications.

Semi-metal and metal elements in steel

4.Effect of Silicon (Si) on steel

The effect of silicon (Si) in steel.

Si is used as a reducing agent and deoxidizer in steel making process, and usually contains 0.15-0.30% silicon in the sedative steel.

Silicon can improve the elastic limit of steel, yield point and tensile strength. So it has been widely used for spring steel.

In the quenched and tempered structural steel by adding 1.0-1.2% silicon, the strength will increased by 15-20%.

Silicon combines with molybdenum, tungsten, chromium and other composition, improve the corrosion resistance and anti-oxidation. So this combination of steel fit for producing the electrical heat-resistant steel.

But if increase silicon content the welding performance will reduce.

5.Effect of Manganese (Mn) in steel

Effect of manganese (Mn) on steel. In the steel making process, manganese is a good deoxidizer and desulfurization agent, the general steel containing 0.3-0.35% manganese. When adding more than 0.7% manganese in carbon steel it called manganese steel. Which not only have enough toughness, but also higher strength and hardness.

Manganese can improve the quenching and thermal processing performance of steel, such as 16 Mn alloy steel yield point is 40% more than A3 steel.

In addition, the steel which contains 11-14% manganese have high wear resistance, for the excavator bucket, ball mill liner. With manganese content increasing, corrosion resistance and welding performance reduces.

For example for API STANDARD 650, it requires ASTM A36 carbon (as rolled semi-killed or fully-killed) steel plate of all thickness shall have manganese content of 0.80% – 1.20% by heat analysis.

Alloy Chemical Elements Effects to Steel Performances

Above chemical elements are included in all of the general steel material.

On the other hand, Alloy steel pipe and plate chemical elements not only contains the normal chemicals like C (carbon), Si (silicon), Mn (manganese), P (phosphorus), S. But also with other alloy elements like Cr (chromium), Ni (nickel), Mo (molybdenum), tungsten, V (vanadium), Ti (titanium), Nb (niobium), Zr (zirconium), Co (cobalt), Al (aluminum), Co (copper), B (boron), rare earth and so on. Alloy steel pipe includes many types, commonly divided into low alloy, alloy and high alloy steel pipe, considering on how many types and percentages of the alloy chemical elements.

Effects of chemical elements in alloy steel pipe material.

6.Effect of chromium (Cr) in steel

Effect of chromium (Cr) in steel pipe can improve strength, hardness, corrosive, wear resistance significantly. It is an important alloy element of stainless steel and heat-resistant steel pipe and plate. On the other side, it will reduce the plasticity and toughness.

7.Effect of nickel (Ni) in steel

Effect of Nickel (Ni) in steel pipe can improve strength meanwhile maintaining good plasticity and toughness. It has a high corrosion resistance to acid and alkali, anti-rust and heat resistant. But for it is a scarce resource, we should try to use other alloy elements instead of nickel-chromium steel.

8.Effect of molybdenum (Mo) on steel

Effect of molybdenum (Mo) can make steel grain refinement, improve the harden and thermal ability. It can maintain sufficient strength and creep resistance (deformation occurs under long-term stress at high temperatures calls creep). Adding molybdenum in structural steel can improve mechanical properties. In additional it can inhibit brittleness caused by quenching.

9.Effect of titanium (Ti) on Steel

Effect of titanium (Ti) chemical elements in alloy steel pipe. It is a strong deoxidizer in steel. It can make the internal structure dense, fine grain strength; reduce aging sensitivity and cold brittleness. Moreover, it can improve welding performance. In the chrome 18 nickel 9 austenitic stainless steel, by adding the appropriate titanium could avoid internal grain corrosion.

10. Effect of vanadium (V) in steel

Effect of vanadium (V) chemical elements in alloy steel pipe. It is an excellent deoxidizer for steel. Adding 0.5% V to the steel pipe material can refine the grain and improve the strength and toughness. Carbide forming by vanadium and carbon, in high temperature and high pressure can improve the ability of hydrogen corrosion resistance.

11. Tungsten (W)

Effect of chemical elements tungsten in steel. As tungsten melting point is highest in metal discovered, the proportion is large, it is a kind of precious alloy elements. Tungsten with C together could form tungsten carbide which has a high hardness and wear resistance. By adding tungsten in tool steel will improve the red hardness and thermal strength significantly. This type of material could be used to cut steel and forging mold.

12. Niobium (Nb)

Effect of Nb (niobium) can refine the grain and reduce the steel overheating sensitivity and tempering brittleness, improve strength, but the plasticity and toughness will decrease. Adding niobium to the ordinary low-alloy steel, can improve the anti-atmospheric corrosion and high temperature hydrogen, nitrogen, ammonia corrosion. Furthermore, niobium improves welding performance. By adding niobium to austenitic stainless steel can prevents internal grain corrosion.

13. Cobalt (Co)

Cobalt is a rare precious metal, used for special steel and alloys, such as hot steel and magnetic materials.

14. Copper (Cu)

Effect of Cu chemical elements in alloy steel pipe. Copper can improve strength and toughness, especially anti-atmospheric corrosion performance. The disadvantage is that in the hot processing is easy to produce hot brittle, more than 0.5% copper content will lead to plasticity reduces significantly. When the copper content is less than 0.50% has no effect on the welding performance.

15. Aluminum (Al)

Effect of chemical elements Al (aluminum) is an usual deoxidizer in steel. By adding a little amount of aluminum can refine grain, improve the impact toughness, such as 08Al steel. Aluminum also have anti-oxidation and corrosion resistance. Combined with chromium and silicon can improve the peeling resistance and high temperature resistance of steel. The disadvantages of aluminum is to influence the hot workability of the steel, the welding performance and the cutting performance.

16. Boron (B)

Steel by adding trace amounts of boron can improve the steel’s compactness and hot-rolled properties, improve strength.

17.Rare earth (XT)

These elements are metals, but their oxides are like “soil”, so usually known as rare earth. The addition of rare earth to the steel can change the composition, morphology, distribution and properties of the inclusions in the steel, thereby improving the various properties of the steel, such as toughness, welding performance, and cold processing performance.

Moreover, you must met the situation that from different country different area, some call it pipe where some other call tube, actually for the same thing.

And since they are looks like the same products, round shape, hollow in the middle, material in steel metals. 

So what’s the real differences between pipe and tube?

Now we are going to explain from below aspects:

Standard Scope for Steel Pipe and Steel Tube
Size Differences
Manufacturing Processes
Applications
Sample Descriptions

Pipe and tube standards scope

Steel tubes that manufactured with ANSI (American National Standards Institute) and API standard specifications are called the PIPE, indicated with “nominal diameter” to describe pipe specification. All others that not manufactured with the ANSI sizes standard or API standard, called tube or tubing. And they are usually described with outer diameter.

Size Differences between steel pipe and tube

Pipe is tube which complied with ASNI B 36.10 and B36.19 (for stainless steel). Its diameter represented with NPS which is different from actual diameters.

Pipe wall thickness is indicated by the schedule No. And the same NPS number can have various types of Sch. No. Such as STD, thickened wall thickness (XS) and special thick wall thickness (XXS), and so on.

Tubing refers to finished product meet the standard PG-27.2.1 [Outer diameter D≤5in.(127mm)], and which according calculate formula to select diameter, thickness and according the design.

Piping usually refers to finished product which calculated by PG-27.2.2 formula to select NPS and Sch. No, and follows the design requirements.

Sample of description

Nominal diameter is not the real diameter, real diameter is always larger than the nominal diameter. For example the pipe nominal diameter in 4 inch, wall thickness SCH 40, means the pipe real out diameter is 4 1/2 inch (114.3 mm), real wall thickness 0.237 inch (6.02 mm).

On the contrary, the tube outer diameters described as real OD, for example tube OD 1” means the real diameter is 1 inch.

Meanwhile, the steel pipe applied in the pipeline systems that require large dimensions. Though the pipe size range from 1/2” to 60 inch, in most cases are for the OD above 4 inch. On the other hand, tubes are referred OD below 4 inch, commonly is 1/2 inch, 3/4 inch, 1”, 1 1/2” etc.

Different applications between steel pipe and tube

Pipe has been widely applied in fluids transporting systems, oil and gas industries, thermal and high pressure services.

As pipe emphasize the function of transporting media which under pressure to another place, so pipe always connect with various fittings such as tees, elbows and valves. Such as standards in API 5L, ISO 3183, ASTM A106, ASTM A53, ASTM A333, etc.

Tube is mostly in heat exchanging systems, boiler services, vessels, tube bundle, U tubes, food industries, machinery parts etc. So the tube sizes always in less tolerances than pipe. Tube Standards such as carbon material in ASTM A179, ASTM A192, and stainless steel tube in ASTM A213, ASTM A270 etc.

Manufacturing Processes differences between steel pipe and tube

Due to pipe dimension range and applications, the pipe manufacturing processes include seamless (hot rolled or cold drawn) and welded (ERW, LSAW, SSAW).

Tube manufacturing processes usually is in seamless of cold drawn, and welded in ERW. Since tube always in smaller sizes and usually applied in heat-exchanger and mechanical parts, it requires more processes, treatment, and test procedures than pipes. Because of these factors, tube production period is longer than pipe, and not easy for massive production.

Our Supply Range for API 5L Pipe

Grades: API 5L Grade B, X42, X52, X56, X60, X65, X70, X80
Product Specification Level: PSL1, PSL2, onshore and offshore sour services
Outer Diameter Range: 1/2” to 2”, 3”, 4”, 6”, 8”, 10”, 12”, 16 inches, 18 inches, 20 inches, 24 inches up to 40 inches.
Thickness Schedule: SCH 10. SCH 20, SCH 40, SCH STD, SCH 80, SCH XS, to SCH 160
Manufacturing Types: Seamless (Hot Rolled and Cold Rolled), Welded ERW (Electric resistance welded), SAW (Submerged Arc Welded) in LSAW, DSAW, SSAW, HSAW
Ends Type: Beveled ends, Plain ends
Length Range: SRL (Single Random Length), DRL (Double Random Length), 20 FT (6 meters), 40FT (12 meters) or, customized
Protection Caps in plastic or iron
Surface Treatment: Natural, Varnished, Black Painting, FBE, 3PE (3LPE), 3PP, CWC (Concrete Weight Coated) CRA Clad or Lined

Here we will do a brief introduction of API 5L pipe and related standard specifications with the below aspects:
Standard Scope
Manufacturing types
Different Grades (B, X42, X46, X52, X60, X65, X70)
Delivery condition (R, N, Q, M)
Product Specification Level (PSL1 and PSL2)
Material specifications (Chemical and Mechanical)
Test Methods
Tolerances on pipe diameters, wall thickness, out-of-roundness
Common defects
Line pipe history and milestones
Applications

API 5L Pipe Standard Scope

In API SPEC 5L 46th Edition, the standard scope is defined as: “Requirements for the manufacture of two product specification levels (PSL1 and PSL2) of seamless and welded steel pipes for use in pipeline transportation systems in the petroleum and natural gas industries. This standard does not apply to cast pipe.”

To summarize, API 5L pipe is the carbon steel pipe applied to the oil and gas transmission system. Meanwhile, other fluids such as steam, water, and slurry can also adopt the API 5L standard for their transmission purposes.

Different Manufacturing Types

API 5L specification covers the manufacturing types in welded and seamless.

Welded Type: ERW, SAW, DSAW, LSAW, SSAW, HSAW Pipe

The API 5L welded pipe common types are as follows:

ERW: Electric Resistance Welded, for pipe diameter normally under 24 inches.

DSAW/SAW: Double Submerged Arc Welding / Submerged Arc Welding, a substitute welding method of ERW for larger diameter pipes.

LSAW: Longitudinal SAW, for diameter up to 48 inches. Also called the JCOE manufacturing process.

SSAW/HSAW: Spiral Submerged Arc Welded / Helical SAW, pipe diameters up to 100 inches.

Check here for the differences between the ERW, LSAW, and SSAW pipes.

LSAW Pipe Manufacturing Video

SSAW Manufacturing Video

Seamless Type: Hot Rolled Seamless and Cold Rolled Seamless Pipe

Seamless manufacturing type is usually for small diameter pipes (typically under 24 inches).

(When the pipe diameter is less than 150 mm or 6 inches, the seamless steel pipe is more commonly applied than the welded steel pipe.)

There are also seamless pipes of large diameters. By using hot rolled manufacturing process, we can get seamless pipes with diameters up to almost 20 inches (508 mm). If you need seamless pipes with diameters above 20 inches, we can make them through hot expanding process, with maximum diameters up to 40 inches (1016 mm).

Seamless Pipe Manufacturing Video

API 5L Pipe Manufacturing Development

In the earliest years, besides Seamless and ERW, SAW manufacturing technologies, the API 5L steel pipe also could be produced in furnace lap-welded (deleted in API 5L in 1962).

With the development of pipeline steel plate-making technology, pipe forming and welding technology has also seen significant improvement, so a lot of ERW pipes and SAW pipes have been used in pipeline constructions. When it comes to big-diameter steel pipes, SAW pipe gains a great advantage. With less raw material cost and simplified and uniform production procedures, welded steel pipe has taken the first place in oil and gas line pipe industries.

API 5L covers Grade B, X42, X46, X52, X56, X60, X65, X70, X80

API 5L steel line pipe adopts different steel grades, which are Gr. B, X42, X46, X52, X56, X60, X65, X70, X80. Some manufacturers are capable of manufacturing steel grades up to X100 and X120. As steel line pipes’ grades go higher, they have stricter control on the carbon equivalent control and higher mechanical strength performance.

Moreover, in the same grade, seamless and welded API 5L pipes have different chemical compositions, namely, welded pipes have stricter requirements and lower amounts of carbon and sulfur.

In terms of different delivery conditions, there are also As-rolled, normalizing rolled, thermomechanical rolled, normalizing formed, normalized, normalized and tempered, quenched and tempered.

Delivery Conditions for Each API 5L Grade

more:

For intermediate grades, API 5L pipe grade shall be in one of the following description formats:

a. The letter L followed by the specified minimum yield strength in Mpa. For example, L290 (X42) means the minimum yield strength is 290 Mpa. In the case of PSL2 pipe, Suffix letters (R, N, Q, or M) shall be added to describe the delivery condition;

b. The letter X followed by a two or three digital number equal to the minimum yield strength in 1000 psi rounded down to the nearest integer and, for PSL2 pipe, the letter describing the delivery condition (R, N, Q, or M) consistent with the above formats.

Letter R: As rolled
Letter N: Normalizing rolled, Normalized formed, Normalized
Letter Q: Tempered and quenched
Letter M: Thermomechanical rolled or thermomechanical formed
Letter S: Sour Services, comes with PSL2 pipe for NS, QS, and MS, eg API 5L X52MS, API 5L X65QS.

Product Specification Level (PSL1 and PSL2 in API 5L)

What is PSL

PSL is the abbreviation of product specification level, which includes PSL1 and PSL2. It also could be deemed as quality level.

PSL1 and PSL2 differences

Please click here for the differences between PSL1 and PSL2 pipes.

Requirement

PSL1 and PSL2 have not only different testing requirements but also different chemical composition and mechanical properties.

PSL1 has stricter requirements than PSL2 in terms of chemical composition, tensile properties, impact test, nondestructive testing, and other indicators.

For more details, please click here for Differences between API 5L PSL1 and PSL2.

Impact Test

PSL1 does not require an impact test, while it is required for PSL2 (except X80).

Non-destructive Test

PSL1 does not require a non-destructive test, while it is required for PSL2.

(NDT: Non-destructive inspection and testing uses radiographic, ultrasonic, or other methods (not breaking the material) in API 5L standard, to reveal pipe defects and imperfections.)

API 5L Pipe Data Sheet Specification

API 5L Pipe Data Sheet specification including chemical composition and mechanical properties for PSL1 and PSL2 pipe.

Chemical Composition

Chemical composition for PSL1 line pipe with wall thickness ≤ 25.0 mm (0.984 inches)
API 5L Pipe Datasheet in PDF

API 5L PSL2 Pipe chemical properties:

Chemical Composition for API Sour Pipe

a. If C > 0.12%, CEIIW limits shall be applied; If C ≤ 0.12%, CEPCM shall be applied.
b. For each reduction of 0.01% for maximum C, an increase of 0.05% maximum Mn is permissible, up to a maximum of 0.20%.
c. Al ≤ 0.060%; N ≤ 0.012%; Al/N ≥ 2:1 (titanium-killed or titanium-treated steel not applicable); Cu ≤ 0.35% (Cu ≤ 0.10% if agreed); Ni ≤ 0.30%; Cr ≤ 0.30%; Mo ≤ 0.15%; B ≤ 0.0005%.
d. For seamless and welded pipes, Ca ≤ 0.006%; For welded pipe if Ca is added by intention unless agreed, Ca/S ≥ 1.5 in case S > 0.0015%.
e. For SMLS pipe maximum limit for S could be increased to ≤ 0.008%, and in case welded if agreed to ≤ 0.006%. For higher S content in the welded pipe, lower Ca/S ratios maybe agreed.
f. Nb + V ≤ 0.06%, unless otherwise agreed.
g. Nb + V + Ti ≤ 0.15%.
h. In case seamless pipe, listed CEPCM value could be increased by 0.03.
i. Mo ≤ 0.35% in case agreed.
j. Cr ≤ 0.45% in case agreed.
k. Cr ≤ 0.45% and Ni ≤ 0.50% in case agreed.

Tensile and Yield strength

For intermediate grades, the difference between the specified minimum tensile strength and minimum yield strength for the pipe body shall be as given in the table for the next higher grade. The specified minimum tensile strength for the weld seam shall be the same value as was determined for the pipe body ung footnote a)

a. For intermediate grades, the difference between specified maximum yield strength and minimum YS shall be as given in the table for the next higher grade, and the difference between specified minimum tensile strength and the specified minimum TS shall be as given in the table for the next higher grade. For intermediate grades up to Grade L320 or X46, the tensile strength shall be ≤ 655 MPa (95 000 psi). For intermediate grades greater than Grade L320 or X46 and lower than Grade L555 or X80, the tensile strength shall be ≤ 760 MPa (110 200 psi). For intermediate grades higher than Grade L555 or X80, the maximum permissible tensile strength shall be obtained by interpolation. For SI units, the calculated value shall be rounded to the nearest 5 MPa. For USC units, the calculated value shall be rounded to the nearest 100 psi.
b. For grades > L625 or X90, Rp0,2 applies.
c. Above limit applies for pipe with D > 323,9 mm (12.750 in).
d. For intermediate grades, the specified minimum tensile strength for the weld seam shall be the same value as was determined for the pipe body using footnote a).
e. For pipe requiring longitudinal testing, the maximum yield strength shall be ≤ 495 MPa (71 800 psi).
f. The specified minimum elongation, Af, shall be as determined with following equation:

g. Lower values of Rt0,5/Rm may be specified by agreement.
h. For grades > L625 or X90, Rp0,2 /Rm applies. Lower values of Rp0,2 /Rm may be specified by agreement.

Mechanical Properties for API 5L Sour Service Pipe

The strength value is the same as PSL2.

API 5L Line Pipe Test Methods

Hydrostatic Test

a. Jointers need not be hydrostatically level, provided that the portions of pipe used in making the jointers were successfully hydrostatically tested prior to the joining operation.

b. Except in the previous situation, the pipe shall withstand the hydrostatic test without leakage through the weld seam or the pipe body.

Bend test

Cracks should not occur in any part of the sample and opening of weld shall not occur as well.

Please Note: For all bend tests, the weld extends to 6.4 mm (0.25 in) on each side of fusion line.

Flattening Test

The flattening test method is used to verify the deformation performance of line pipe to the specified size and display its defects. According to the stress and deformation characteristics of the specimen during the flattening process, the flattening test shall show the resistance to longitudinal cracking and circumferential cracking of the pipe and display its internal defects and surface defects.

Other than the above three common tests, there are other tests that are required in each circumstance.
Guided-bend test
CVN impact test for PSL2 pipe (including pipe body tests, pipe weld and HAZ tests)
DWT test for PSL2 welded pipe

Surface Conditions, Imperfections and Defects Appearances

All API 5L pipes shall be free from defects, cracks, sweats and leaks.

More defects as:

Undercuts in SAW and COW pipes.
Arc burns
Laminations
Geometric deviations
Hard spots
Other surface imperfections (Defects depth more than 0.125 thickness or ≤ 0.125 wall thickness refers to Clauses C in API 5L.)

API 5L Pipe Sizes and Tolerances

Tolerances for diameter and out of roundness

Tolerances for wall thickness

Tolerances for pipe lengths

API 5L pipe length tolerances shall be complied as following conditions:
a. Random length shall be delivered as below table 12.
b. Approximate lengths shall be delivered as tolerances of +/- 500 mm.

Order Information for API 5L pipe

a. Quantity in meters or in tons. Total meters or total pieces.
b. PSL1 or PSL2 (N/M/Q/NS/MS/QS), Sour Services, Onshore/Offshore
c. Pipe Types (Seamless or welded, EW, ERW, HFW, SAW, LSAW, HSAW, SSAW)
d. Reference documents to API 5L.
e. Steel Grade
f. OD (Outside diameter) and WT (pipe wall thickness)
g: Length and length type (Double random length / Single random length / Fixed length / Approximate length)
h. Individual annexes applicability of confirmation

Additional Information

The following additional information could also be included in the PO in different situations.
• Pipe designation
• Chemical composition for intermediate grades
• Carbon equivalent limits
• Diameter or round tolerances for special size pipe
• Jointer welds
• Ends type
• Repairs requirements
• CVN impact test
• DWT test
• Hardness test
• Pipe markings and end colors
Etc.

Traceability

For PSL1 pipe, manufacturer shall establish and follow documented procedures to maintain
a. The heat identity until all related chemical tests are performed and complied with the required specifications.
b. Test unit identity until all related mechanical tests are performed and complied with the related specifications.

For PSL2 pipe, besides the above terms, such documents shall provide means for tracing any length of the pipe to the proper test unit, including the related chemical and mechanical test results.

API 5L Line Pipe History and Milestones

Before API 5L pipe standard generated

1834 First cast iron pipe made at US (Millville, NJ)
1856 Converter steel making technology developed
1858 First successful oil well established in Titusville, PA
1863 Screwed couplings used in pipeline connections
1863 Pipe is made in wrought iron with furnace lap-welded seams
1893 First 30-inch diameter pipe made in lap-welded
1899 First large diameter seamless steel pipe in 20 inch is made, thickness at 5/8 inch
1917 11-mile pipeline is using electric metal arc welding
1919 API (American Petroleum Institute) is charted.
1924 Electric resistance welding with direct or low frequency current is invented
1925 Large diameter seamless pipe in 24” diameter is available
1927 Electric flash welded pipe is developed

After API 5L released

1928 First API 5L standard for manufacturing line pipe appears, covers furnace butt-welded pipe, furnace lap-welded pipe, seamless pipe. Minimum YS 172 Mpa 25000 psi, maximum 310 Mpa 45000 psi. Including material for three Grade A25, A, B, minimum yield strength was 172 Mpa, 207 Mpa, and 241 Mpa.
1931 API 5L pipe specification included ERW pipe (electric resistance welded pipe)
1933 Large diameter steel pipe mostly adopted electric arc girth welding
1944 Electric flash-welded pipe added in API 5L
1946 30-inch large diameter single submerged-arc-welding pipe begins
1948 Double submerged-arc-welded pipe (DSAW pipe) appears
1948 Release API 5LX standard, covers minimum yield strength material in 289 Mpa (42000 psi).
1953 API 5L Grade X46 and X52 pipe added
1962 Furnace lap-welded pipe removed from API 5L pipe, basic oxygen steel making processes accepted.
1963 Nondestructive inspection methods start to use in API 5L pipe specification
1966 API 5L Grade X60 pipe appears
1969 Supplemental requirements for toughness test added in API 5L
1973 API 5L Grade X70 steel pipe appears
1983 API 5L and API 5LX combined in API 5L.
1985 Grade X80 pipe appears
2000 Minimum level fracture toughness made mandatory in API 5L

Before 2000, Grade X70 pipe used in pipelines total quantity at 40%, Grade X65 and X60 was at about 30% each, small diameter pipelines also choose to Grade X52 pipe, which mostly at ERW type.

API SPEC 5L and ISO 3183

About API SPEC 5L 2018 – 46th Edition of API Pipe Standard

This version was initiated in April 2018 and effective on 1st, May 2019.

ISO 3183 standard specification for line pipe

In 2007, ISO and API did a joint release for ISO 3183:2007/API SPEC 5L 44th, to complete an international standard worldwide. Until 2012, United States claimed about the intellectual property right, so API terminated the cooperation with ISO, and no longer making standards for ISO. But the latest version of ISO 3183:2012 or API 5L 2012 still a union achievement, except API LOGO and onshore line pipe specification for European, the other content was all the same.

Differences between API 5L 45th edition and previously edition

The main difference between 45th Edition with previously is to add two additional appendixes: European onshore pipeline for PSL2 pipe order specification, (Annex M). And Equations for threaded and coupled pipe and background equations for guided bend and CVN test specimens (Annex P). As for the other content, they only have a slight difference in related standards, manufacturing technology, performances norm, inspection methods, besides adjustment of text expression. The latest version of API 5L 2012 is completer and more scientific.

API 5L Pipe Application

Modern API 5l steel line pipe belongs to low carbon or ultra-low carbon micro alloy steel. It is a high technology and high value-added product.

The steel line pipe production has applied to almost all modern technology achievements in the metallurgy field for nearly 20 years.

At present, the development trend of line pipe engineering is large diameter, high pressure gas transportation, high cold and corrosion service environment, thick wall of submarine pipeline etc.

Therefore, API 5L steel pipe should have high strength, high toughness, and brittle fracture, as well as good welding ability, and suitable for sour services and in H2S environment with anti-corrosion performances.

API 5L pipe length definition

In API 5L standard spec, the steel line pipe shall be delivered in accordance with the random length and approximate length in the order contract.
In API 5L specification 9.11.3.3 specified the tolerance for the the pipe length as belowed:
a. Unless other lengths agreed, (Length with less tolerances), random lengths shall be applied as the table 12.
b. Approximate lengths shall be delivered within a tolerance of +/-500 mm (+/-20 inch).
The common random length of API 5L steel line pipe is designated at 6 m, 8 m, 9 m, 10 m and 12 m. The length also can be customized according to specific requirements.

The tolerances for random length pipe shall be as below table (API SPEC 5L Table 12).

Is it easy to comply the pipe length tolerance

For the welded pipe the raw material is steel coils or steel plates, so it is easy to comply longer length with big diameter. But for seamless steel line pipe, raw material is steel round bar and manufactured by hot rolled processes, so the pipe length is limited by the raw material round bar and how big diameters line pipe required. If required longer length (more than 12 meters or 40 ft) with big diameters (specially OD more than 20” or 508 mm), it is difficult to comply with seamless.

How to handle seamless steel pipe with longer length and big diameters

Normally for Chinese seamless steel pipe manufacturer the maximum original diameter produced by hot rolled process is 16” 406 mm, few manufacturers are capable of produce maximum 18” seamless steel pipe, Octal could supply maximum 20” 508 mm original seamless steel line pipe by hot rolled process.

For the seamless steel line pipe outer diameters more than 508 mm, it shall be manufactured by hot expanding processes. (Octal supply seamless steel pipe maximum to 1200 mm).

Hot expanding process for seamless steel pipe

Hot expanding process is an after-treatment for the original hot rolled seamless steel pipe, it is the process to enlarge the pipe diameters by hot expanding. During the hot expanding process, the heater (normally the heat ring) makes the heat to the pipe body, by the help of the different Dia of hydraulic lever inside the pipe move through the pipe internal, the diameters will be expanded as required size.

So today we are going to explain what is precision pipe from below aspects:

Material Standards
Manufacturing Processes
Size Tolerances
Features
Applications

What is precision pipe

Precision pipe is the carbon, alloy or stainless steel pipe with high precision sizes. Usually it has been made through hot rolling or cold drawn (cold rolling) processes. So precision pipe is a kind of seamless pipe.

It is designed with several advantages:
Inside and outside surface no oxide coating;
It could bear high pressure, no leaking;
Strict less tolerance;
Surface smooth;
No reformation in cold bending, no cracks during flaring test, and flattening test.

With these advantages it is widely used for manufacturing the pneumatic parts and hydraulic components.

Precision steel pipe material standard

International standard for precision pipe is DIN 2391, which is applied with European standard.

As a matter of fact, more steel pipe standard could applied for the precision pipe. Includes DIN2445, EN10305, DIN1630, DIN1629, ASTM A106, ASTM A179, JIS G3445

Materials available with 10#, 20#, 35, 45, 40Cr, 25Mn. 37Mn5, St35(E235), St37.4, St45(E255), St52(E355) and etc.

Size Tolerances

For hot rolling precision steel pipe, tolerance of OD is +/- 0.1%.
For cold drawn precision pipe, tolerance allowed in below conditions:
Diameters 6mm to 10mm, normal tolerance condition +/- 0.2%, premium tolerance condition +/- 0.15%.
10mm to 30mm, normal tolerance condition +/- 0.4%, premium tolerance condition +/- 0.2%.
30mm to 50mm, normal tolerance condition +/- 0.45%, premium tolerance condition +/-0.3%.
For outer diameters above 50mm, normal tolerance condition +/- 0.1%, premium tolerance condition +/- 0.8%.

Key processes in manufacturing the precision steel pipe

During manufacturing processes, the key point is to do the annealing for raw materials.

Precision steel pipe manufacturing flow chart:
Raw Material Inspection – Remove Oxide Layer – Visual Inspection – Heating – Hot Rolling – Pickling and Passivation (Phosphating) – Grinding – Lubrication and Drying – Cold Rolling (Internal and external extraction) – Remove Oil – Ends Cutting – Inspection – Marking – Packing and Storage

As we know, most of precision steel pipe has cold drawn and hot rolled process. On the contrast, cold rolling will be more complicated. Not only the pipe need to be continuous rolled by three roller, but also the test have to be done after extrusion, so to guarantee the quality of the precision pipe materials.

Manufacturing methods of seamless precision pipe includes hot rolling and cold drawn. More over it could be manufactured in welding processes.

Features

a. You can get a smaller diameter with precision steel pipe
b. High precision pipe accept small quantity for MOQ.
c. The pipes with cold drawn processes has high precision and good surface finish.
d. The transverse area of the steel pipe is more complicated.
e. Performance is superior, with higher density.

Application

The internal and external diameter could control within +/- 0.01 mm. In the guarantee of anti-bending strength and torque strength same, the weight of precision pipe is lighter. It can be widely used in manufacturing precision machinery parts and engineering structure, and also commonly used to produce various kinds of conventional weapons, barrel, shells, bearing and so on.

ASTM A270 sanitary (hygienic) stainless steel tubing is the standard specification for the welded seamless, and heavily cold worked welded austenitic and ferritic stainless steel sanitary tubing. It includes the stainless steel tube types in seamless and welded ERW, EFW. ASTM A270 sanitary tubing intended applied in the diary and food industry, bio processing equipment, and having special surface finish.

View here for about information about ASTM A270 Standard Specification.

ASTM A270 stainless steel tube size range

ASTM A270 sanitary stainless pipe usually refers to the small pipe diameters, normally from 1/2” to 2 1/2”, thickness from 0.049 in (1.24mm) to 0.15 in (3.81mm).
The maximum outer diameter of ASTM A270 tubing is 12 inches (304.8 mm).
ASTM A270 tubing using inch-pound as the standard unit of measure.
Wall thickness tolerance shall not vary more than 12.5%.

Referred standard for ASTM A270 sanitary tubing

ASTM A 262: Methods of detecting intergranular corrosion for the magnetization coefficient.
ASTM A 480/A 480 M is the general specifications for flat stainless steel, heat-resistant stainless steel plate, sheet and steel bars.
ASTM A 923 Test methods for detecting detrimental intermetallic phase in duplex austenitic/ferritic stainless steels
ASTM A 967 is the specification of passivation treatment for stainless parts .
ASTM A 1016/1016 M is the general specification for ferritic alloy steel, austenitic alloy steel and stainless steel.
E 527 is the test methods for numbering metal and alloy
ASTM B 46.1 surface structure (surface roughness, waviness and layers).
ASME boiler and pressure vessel’s numbers and other standards.

Stainless tube manufacturing processes

ASTM A270 sanitary stainless steel pipe shall be noted below points during manufacturing processes:

1) Seamless steel pipe should not contains any kind of welding processing.
2) Welded steel pipe applied in automatic welding processing, but should not use metal materials as filler.
3) Heavily cold worked (HCW) tubes shall be manufactured by cold working of not less than 35% reduction of thickness of both wall and weld to a welded pipe prior to the final anneal. Filler materials shall be noted added during welding process. The weld shall be 100% radio graphically inspected in accordance with ASME boiler and pressure vessel standards specification.
4) Sanitary pipe could be furnished with hot finished or cold finished at Manufacture’s option.

Hot-treatment methods for ASTM A270 stainless tube

All materials should supply after hot-treatment. Except the for duplex stainless steel materials S31803, S32003, S320205, S32750, N08926 and N08367, in these cases it shall consist of heating the material to a minimum temperature of 1900 ℉ (1040 ℃) and quenching in water or rapid cooling by other means.

CHEMICAL COMPOSITION

A little part of flat or steel pipe shall be taken for chemical analysis. The composition should meet the ASTM A270 standard table 1.

Table 1:

MECHANICAL TESTS

Mechanical tests includes negative flattening test, hydrostatic or nondestructive electric test. Mechanical strength shall be complied with ASTM A270 standard specification table 2.

Table 2:

TOLERANCES

SURFACE REQUIREMENTS

Surface of rolled products: No need extra polishing or smooth treatment.
Mill Finish— A finish without additional polishing oroperations intended to smooth the surface.

Mechanical polished surface: Purchasers according the same numbering abrasive (grinding stuff)  to polish the products get the required products’ surface:
Finish No. 80 – A ground finish produced by polishing a tube with an abrasive media impregnated with No. 80 grit.
Finish No. 120 – No. 120 grit.
Finish No. 180 – No. 180 grit.
Finish No. 240 – No. 240 grit.
Other mechanically polished finishes may beagreed upon between the purchaser and manufacturer

Electrolytic polishing of the surface: Before this processing, manufacturer could use other ways to polish products.
The maximum average of roughness: Customers could specify the maximum roughness of internal surface, external surface and both surface.
Surface furnishment also could be decided by manufacturer or purchaser.
Normally surface treatment: Internal, External, SF4, SF3, etc.

MARKS

At last, the mark should furnished in accordance with A 1016/A1016M, and specified in the order. Includes the sanitary stainless steel pipe manufactured in Seamless (SML), Welded (WLD) or heavily cold worked (HCW).

PACKAGE

Before delivery, all steel pipes should bundled well, and covered by paper, cloths. Or packed in box by manufacturer.

ADDITIONAL REQUIREMENTS

In case specified in the order, intergranular corrosion tests shall be performed by manufacturer on specimens representative of the as-shipped condition. Sanitary stainless steel pipe and tube shall be capable of passing corrosion tests in the as-shipped condition. For austenite alloy steel should meets the Practice E of the standard A262 , and for duplex alloy steels (S31803, S32205 and A32750) should meets experiment C of Test Methods A 923.

In case the ASTM A270 stainless steel pipe for pharmaceutical quality applications, it is more strict on the chemicals, strengths and size tolerances.

These pipes serve as essential components in heat exchanger tubing, tube bundles, economizers, superheaters, and high-pressure boilers, where stable mechanical properties and resistance to oxidation at elevated temperatures are indispensable. Their design and production must strictly conform to standards such as ASTM, ASME, DIN, and EN specifications to ensure performance in demanding operating conditions. By combining metallurgical quality, dimensional accuracy, and pressure tolerance, boiler steel pipes play a pivotal role in the safety and efficiency of thermal and chemical process industries.

It has been widely used at heat exchanger pipe and tubing services, tube exchanger bundle, high pressure boiler, economizer, super heater, petrochemical industry pipes, etc.

Boiler pipe materials and standards

Standards and material for steel pipe is available at carbon, alloy, and stainless steel material.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6,7 to Gr 9,
Alloy steel: ASTM/ASME A/SA 213 T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92
Stainless Steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S,309S,317,317L,321,321H, and duplex stainless steel material etc.
Common Sizes: OD from 6mm to 1240mm, thickness from 1mm to 50mm
Types: Straight boiler pipe, and U boiler steel pipe for tube exchanger bundle.
These standards specify the classification, size, shape, weight and allowable deviation, technical requirements, inspection and test, packaging, marking and quality certificate of seamless steel tubes for boiler.

Boiler Pipe Size

Boiler pipe size range complied with the different ASTM standard required. Like ASTM A106 or ASTM 179, 192 etc.

But most of the boiler pipe size is small, outer diameter usually less than 1 1/2” (1/4”, 1/2”, 3/4”, 1” and 1 1/2”). Then 2”, 2 1/2”, 3” and maximum to 4”.

Medium and high pressure boiler pipe differences

Based on different working temperature, the medium or high pressure boiler pipe shall be used. Normally classified as below cases:
a. The operation temperature of general boiler pipe is lower than 450℃. The medium pressure boiler pipeline mainly adopts hot rolling process or cold drawing process.
b. High pressure boiler pipes are often used in high temperature and high pressure conditions. Under the action of high temperature flue gas and steam, the pipe will occur oxidation and corrosion. It is required high pressure boiler pipe that has high durable strength, high oxidation corrosion resistance and good tissue stability.

Boiler Pipe Manufacturing methods

The manufacturing method of medium and high pressure boiler steel pipe is same with the seamless steel pipe, but there are some key manufacturing processes shall be noted:
Fine drawing, surface bright, hot rolling, cold drawn, heat expansion

Heat treatment methods applied in the boiler pipes

Heat treatment is a method of changing the physical properties of high pressure boiler pipe by heating and cooling. Heat treatment can improve the microstructure of high pressure boiler pipe, so as to meet the required physical requirements. Toughness, hardness and wear resistance are obtained by heat treatment. In order to obtain these characteristics, it is necessary to adopt quenching, annealing, tempering and surface hardening.

a. Quenching

Hardening, also called quenching, is that high pressure boiler pipe is heated evenly to the appropriate temperature, then quickly immerse in water or oil for rapid cooling, and cooling in the air or in the freezing zone. So that the high pressure boiler pipe can obtain the required hardness.

b. Tempering

High pressure boiler pipe will become brittle after hardening. And the stress caused by quenching can make the high pressure boiler pipe tapped and broken. The tempering method can be used to eliminate brittleness. Although the hardness of high pressure boiler pipe is lighter reduced, its the toughness can be increased to reduce the brittleness.

c. Annealing

Annealing is the method to eliminate the internal stress of high pressure boiler pipe. The annealing method is that the steel parts need to be heated to the critical temperature, then put in dry ash, lime, asbestos or closed in the furnace, then let it cooling slowly.

The basic method of rust removal

a. Cleaning

Using the solvent and emulsion to clean the surface of high pressure boiler pipe, so as to achieve the purpose of removing oil, grease, dust, lubricant and similar organic matter. But it cannot remove the dust, oxide skin, welding medicine and so on. So it is only as a supplementary method in the anti-corrosion production.

b. Tool

Tool rust removal mainly use wire brush and other tools to grind the surface of high pressure boiler pipe. It can remove loose or warping of the oxide skin, rust, welding slag and so on. Manual tool can reach SA2 level, power tool can reach SA3 level. If the iron oxide scale attached to the surface, it cannot reach the anchorage depth required by the anti-corrosion construction.

c. Acid cleaning

High pressure boiler pipe generally adopt chemical and electrolytic methods to do pickling treatment.

d. Spray rust removal

Spray rust removal cannot only remove rust, oxide and dirt completely, but also high pressure boiler pipe can achieve the required uniform roughness under the action of abrasive impact and friction force.

Spay rust removal cannot only expand the physical adsorption on the surface of high pressure boiler pipe, but also enhance the mechanical adhesion between the anti corrosion layer and the pipe surface. So spray rust removal is ideal method of rust removing for pipeline corrosion.

In Summary

The reliability of a boiler system depends heavily on the quality of its tubing. By delivering consistent performance under extreme pressure and temperature fluctuations, boiler steel pipes ensure the stable operation of power plants, refineries, and industrial heat exchangers. Their ability to resist creep, oxidation, and thermal fatigue makes them indispensable for facilities that cannot afford downtime or structural failure.

As a global supplier, Octal Steel provides certified medium-pressure and high-pressure boiler steel pipes manufactured in strict accordance with ASTM, ASME, and EN standards. Each pipe undergoes rigorous quality inspections and is supplied with complete documentation, including mill test certificates (MTC) and traceability reports. For clients across the energy and petrochemical sectors, Octal Steel delivers not only high-quality boiler tubing but also long-term reliability and technical assurance essential for critical operations.