Steel Pipe – Octalsteel

Steel Pipe Third Party Inspection

Lynx Bai — Tue, 10 Mar 2026 08:35:19 +0000

Third Party Inspection Service for Steel Products

Third party inspection (TPI) is an independent verification process used to confirm that steel products, dimensions, materials, markings, testing, and documents comply with the purchase order, project specification, and applicable standards before shipment. In export steel supply, TPI is not just an extra step in the workflow. It is a practical control point that helps buyers reduce mismatch risk between quotation, production, inspection, shipping documents, and final site acceptance.

At Octal Steel, third party inspection support is part of how we execute export steel orders. For many buyers, especially in pipeline, oil and gas, EPC, pressure equipment, and infrastructure projects, the concern is not only whether the goods are produced, but whether they are inspection-ready, document-ready, and shipment-ready. This is where our TPI coordination support becomes important.

How Octal Steel Supports Third Party Inspection

Octal Steel provides third party inspection support for steel products based on client-appointed inspection requirements. Our role is not limited to manufacturing or supply only. We also support the order at the inspection stage by coordinating inspection timing, preparing the required documents, checking product identification and traceability, and making sure the goods are ready for review before shipment.

In practical terms, this means helping align the production status, inspection scope, and shipment schedule. Many inspection delays do not come from the product itself. They come from missing records, incomplete marking, packing not ready for review, or poor coordination between the supplier, inspector, and buyer. Our job is to reduce these gaps so the order can move from “produced” to “approved for shipment” more smoothly.

Inspection Agency / Type	Typical Role in Steel Orders	What Octal Steel Can Support
BV (Bureau Veritas)	Third-party inspection for material verification, dimensional checks, marking review, packing verification, and document review before shipment.	Inspection coordination, product readiness, document preparation, traceability check, packing and marking support.
SGS	Independent inspection for export steel products, including visual inspection, dimensional verification, document review, and shipment release support.	Scheduling support, inspection preparation, identification and marking check, packing review, and document alignment.
TÜV / Other Client-Appointed Agencies	Project-based third-party inspection according to buyer, EPC, or owner requirements.	Coordination based on nominated inspection scope, witness support, document handover, and shipment readiness.
Witness Inspection for Testing	Inspection agency may witness hydrotest, PMI, NDT, coating checks, or other specified tests depending on order requirements.	Arrange witness points, prepare test records, and support inspection during agreed production or pre-shipment stages.
Document Review / Release	Review of MTC, dimensional records, traceability, marking list, packing list, and other project-required inspection documents.	Prepare document package, align product-to-document traceability, and support release before shipment.

Inspection Items Octal Steel Can Support

The inspection scope depends on the product type and project requirement, but in steel supply the mostcommon inspection items are clear. Octal Steel can support third-party inspection for the following areas:

Third Party Inspection for Steel Pipe and Pipeline Projects

For pipeline and line-pipe-related projects, third party inspection usually carries more weight because acceptance is not based on one item alone. The buyer may review the pipe body, pipe ends, welding status where applicable, coating or surface condition, traceability, and test records as part of one release process. In these projects, TPI helps ensure that the supplied materials are not only manufactured to the order, but also documented and prepared in a way that matches project approval procedures.

This is why pipe and pipeline inspection services are a meaningful part of Octal Steel’s support scope. Pipeline buyers are often managing multiple interfaces at the same time: specification review, testing, logistics, document release, and site schedule. A missing marking record or an incomplete packing check can delay the same project as much as a dimensional issue. Good TPI support is about controlling the whole acceptance chain, not just one inspection point.

Agencies and Inspection Coordination

In export steel orders, the inspection body is usually nominated by the client, project owner, EPC contractor, or buyer. Octal Steel works with client-appointed third-party agencies such as BV, SGS, TUV, and other nominated inspectors. Our role is to help the buyer keep the inspection process visible, organized, and ready before the inspector arrives on site.

How Octal Steel Supports the Inspection Process

1. Align inspection scope in advance
We confirm the applicable standard, product specification, inspection points, and document requirements with the client before inspection. This helps reduce delays caused by unclear checkpoints, missing reports, or mismatch between the order and the inspection plan.

2. Share progress updates during production
We can keep the buyer informed with production status, workshop photos, finished product photos, marking details, and packing progress. This gives the client better visibility before the formal inspection date.

3. Prepare documents before the inspector arrives
Relevant records can be organized in advance according to the order requirement, such as MTC, dimension reports, NDT reports, hydrotest records where applicable, coating records, packing lists, and other release documents. Draft copies can also be shared with the client for early review.

4. Support smoother inspection and shipment release
By connecting the inspected goods with marking, lot traceability, and final documentation, we help make site inspection, document approval, and shipment release more efficient, especially for export orders with client-appointed inspection agencies.

Documents and Inspection Records

In steel TPI, documents matter as much as the physical goods. The inspector may review certificates, dimensional records, marking lists, packing lists, and testing records together, because acceptance depends on consistency across these documents. A product can be dimensionally correct and still fail release if the traceability or document mapping is incomplete.

That is why Octal Steel pays attention to the documentation side of inspection support. Depending on the order, the release package may include mill certificates, dimensional inspection records, traceability information, packing details, and related supporting documents. When needed, sample report pages can also be prepared for reference, with sensitive information masked, to show customers the typical structure of inspection records used in export projects.

Why Buyers Use Octal Steel for TPI Support

For many buyers, the value of third party inspection is not just “someone checks the goods.” The real value is that the order moves forward with fewer surprises. In practice, buyers use Octal Steel for TPI support because we understand that inspection is connected to production, packing, documents, and release. If one part is not aligned, the whole shipment can slow down.

This is especially important when the order is time-sensitive, technically controlled, or linked to project approval. By supporting the inspection process as part of the supply workflow, we help buyers reduce mismatch risk and improve confidence before shipment. That is also why many customers see TPI support not as an extra service, but as part of a reliable export steel supply process.

Sample Inspection Files and Previous Support Experience

When appropriate, sample inspection pages or report formats can be shared for reference. In these cases, customer names, project numbers, pricing, and other sensitive details should be masked or watermarked. This helps show the structure of the inspection records without exposing confidential commercial information.

For customer follow-up, this kind of reference material is often useful. It allows the buyer to quickly understand what a steel third party inspection file may include and how the inspection process is typically documented. For Octal Steel, this also supports a clearer discussion with customers who are still deciding whether TPI is needed for their order.

What Third Party Inspection Means in Steel Supply

In steel export projects, third party inspection is commonly used to verify that the supplied goods match the agreed technical and commercial requirements before release. The inspection scope may cover material grade, heat number traceability, dimensional checks, marking, testing records, packing, and related documents. For project buyers, this process provides an independent checkpoint before shipment. For suppliers, it creates a clear release path that links production status with inspection evidence and document closure.

This is particularly important in orders involving steel pipe, plate, fittings, flanges, structural materials, and pipeline-related products. If the products are intended for pressure service, line pipe systems, EPC packages, or export projects with strict approval procedures, buyers often need more than a mill certificate alone. They need confirmation that the goods presented for shipment are the same goods supported by the inspection and document package.

for review, or poor coordination between the supplier, inspector, and buyer. Our job is to reduce these gaps so the order can move from “produced” to “approved for shipment” more smoothly.

Third Party Inspection as Part of Reliable Steel Delivery

A good third party inspection process is not only about passing inspection. It is about aligning the products, records, and shipment release conditions before the goods leave the factory. For export steel projects, that alignment matters. It protects the buyer, supports the supplier, and reduces avoidable problems after shipment.

Octal Steel provides third party inspection service support for steel products as part of this delivery logic. Whether the order involves steel pipe, plate, fittings, flanges, or pipeline materials, the objective is the same: make sure the goods are ready for inspection, ready for documentation review, and ready for shipment with fewer approval risks.

FAQ

Q1. What does third-party inspection cover for steel products?
A1. It usually covers material verification, dimensions, visual condition, marking, selected test records, and document review before shipment release.

Q2. When should third-party inspection be arranged for a steel order?
A2. It is best arranged before shipment, when the goods are ready for inspection and the key records can be checked against the order requirements.

Q3. Can MTC and heat number traceability be checked before shipment?
A3. Yes. The buyer can review MTCs, heat numbers, marking, and related records to confirm the goods remain traceable to the ordered material.

Q4. Can BV, SGS, or other nominated inspectors witness the inspection process?
A4. Yes. Client-appointed inspectors can be coordinated for witness points, record review, and release checks when required by the project or order procedure.

Differences between ASTM A53 B and ASTM A106 B Steel Pipe

Amanda — Fri, 01 Dec 2017 02:55:45 +0000

In the design and procurement of industrial piping systems, carbon steel pipes under ASTM A53 and ASTM A106 standards are often considered side-by-side due to their wide applicability. However, fundamental differences exist in their core design objectives, scope of application, and technical specifications. Misselection can lead to increased project costs or potential safety risks. A precise understanding of their distinctions—not only in chemical composition and mechanical properties but also the intended service conditions (general ambient vs. high-temperature/high-pressure) they are designed for—is a prerequisite for compliant, economical, and safe material selection. This FAQ will provide an in-depth analysis of the key differences between A53 and A106 standards regarding manufacturing processes, chemical composition, mechanical properties, testing requirements, and typical applications, offering a clear guide for specification.

The scope of ASTM A106 and A53

ASTM A53 specification covers the steel pipe manufacturing types in seamless and welded, material in carbon steel, black steel. Surface natural, black, and hot-dipped galvanized, zinc coated steel pipe. Diameters range from NPS 1⁄8 to NPS 26 (10.3mm to 660mm), nominal wall thickness.

ASTM A106 standard specification covers the seamless carbon steel pipe, applied for high-temperature services.

Different types and grades for both standard

ASTM A53 steel pipe types and grades

For ASTM A53 there are ERW and seamless steel pipes Type F, E, S covers Grade A and B.

A53 Type F, furnace butt welded, continuous weld Grade A
A53 Type E, Electric resistance welded (ERW), in Grade A and Grade B.
A53 Type S, Seamless steel pipe, in Grade A and Grade B.

If raw steel material of different grades in process of continuously casting, the transition material result shall be identified. And the manufacturer should remove the transition material with the processes that could separate the grades positively.

In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.

In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.

(Please note the type F is not used for flanging, and if type S or type E is applied for coiling or cold bending, it is recommended to use ASTM A106 Grade A pipe. Although, it is not prohibit to use ASTM A106 Grade B for the cold bending and coiling. According the facility from the manufacturer, type E of ASTM A53 pipe could be supplied non cold expanded or cold expand steel pipe.)

A53 B Chemical and mechanical properties

ASTM A53 Grade B chemical properties content C≤0.30%, Mn≤1.2%, P≤0.05%, S≤0.045%, Cr≤0.40, Cu≤0.40, Ni≤0.40, Mo≤0.40, V≤0.08.
ASTM A53 B mechanical strength is the same with ASTM A106 B steel pipe, Tensile strength maximum 415 Mpa, Yield strength maximum 240 Mpa.
Elongation: For A53 pipe there are 2 methods to calculate elongation.
A: Use equation: e = 625 000 [1940] A^0.2/U^0.9
B: See ASTM A53 elongation value table X4.1 or table X4.2 for different specimen area.

ASTM A106 steel pipe types and grades

For ASTM A106 steel pipe, manufacturing Type only in seamless, processes hot rolled and the cold drawn. Grade in A, B and C.

ASTM A106 Grade A: Maximum Carbon element 0.25%, Mn 0.27-0.93%. Minimum tensile strength 48000 Psi or 330 Mpa, yield strength 30000 Psi or 205 Mpa.
A106 Grade B: Maximum C below 0.30%, Mn 0.29-1.06%. Minimum tensile strength 60000 Psi or 415 Mpa, yield strength 35000 Psi or 240 Mpa.
Grade C: Maximum C 0.35%, Mn 0.29-1.06%. Minimum tensile strength 70000 Psi or 485 Mpa, yield strength 40000 Psi or 275 Mpa.

Differences on mechanical properties

ASTM A53 Grade B mechanical strength is same with ASTM A106 Grade B pipe.

Differences on Chemical properties

From below table listed the differences on chemicals for the three similar pipe:

As ASTM A106 B is the common use, the chemical here we listed is C≤0.3%, Mn 0.29-1.06%, P≤0.035, S≤0.035%, Si>0.1, Cr≤0.40, Cu≤0.40, Ni≤0.40, Mo≤0.40, V≤0.08.

Differently with ASTM A53 B, ASTM A106 B has Si min 0.1%, which A53 B has 0, so A106 B have better heat resistance than A53 B, since Si improve the heat resistance.

A106 Grade B has low sulfur and phosphorus than A53 B, this is better.

Applications for both standards

Both pipes applied for mechanical and pressure systems, transporting steam, water, gas, and etc.

ASTM A53 pipe application

1. Construction, underground transportation, extraction of ground water while building, steam water transportation etc.
2. Bearing sets, machinery parts processing.
3. Electric application: Gas transmission, water power generation fluid pipeline.
4. Wind power plant anti-static tube etc.
5. Pipelines that required zinc coated.

ASTM A106 pipe application

Especially for high temperature services that up to 750°F, and it could substitute ASTM A53 pipe in most of the cases. In some country at least in United States, usually ASTM A53 is for welded pipe while ASTM A106 is for seamless pipe. And if client asked for ASTM A53 they will also offer A106. In China, manufacturer will offer the pipe that comply to three standards ASTM A53 B / ASTM A106 B / API 5L B.

More details about ASTM A53 Grade B
More details for ASTM A106 Grade B
More details about API 5L Pipe.

conclusion

In summary, compared to A53, the ASTM A106 standard defines its suitability for high-temperature, high-pressure services as “power piping” or “process piping” through stricter chemical composition controls, higher mechanical property requirements, and heat treatment regimens that ensure elevated temperature performance. Conversely, ASTM A53 serves as an excellent “general-purpose” pipe for most ambient temperature or low-pressure systems.

Correctly distinguishing and applying these two standards is fundamental to ensuring the safety, reliability, and economy of piping systems. Octal Steel, as a professional carbon steel pipe supplier, provides both seamless and welded pipes conforming to ASTM A53 and A106 standards.

LSAW Pipe and SSAW Pipe Specifications, Differences

Amanda — Wed, 06 Sep 2017 05:46:44 +0000

Difference between LSAW and SSAW Pipes

Pipelines that transport oil, gas, water, or other fluids rely heavily on welded steel pipes, particularly LSAW (Longitudinal Submerged Arc Welding) and SSAW (Spiral Submerged Arc Welding) pipes. Although both utilize submerged arc welding technologies, the distinction in their welding orientations leads to significant differences in mechanical behavior, dimension control, defect propensity, and application scope. Understanding these differences is essential for pipeline engineers, project planners, and procurement specialists who must match materials to service conditions with precision.

LSAW pipes are formed from steel plates bent and welded longitudinally to produce a seam that runs parallel to the pipe’s axis, offering superior straightness, weld uniformity, and controlled mechanical properties. Their design makes them ideal for high-pressure pipelines and critical infrastructure spanning long distances. SSAW pipes, in contrast, are produced by spirally welding a steel strip at a preset helix angle, which allows a single strip width to yield different diameters. This versatility enhances material utilization and cost effectiveness but introduces additional considerations in seam stress behavior and defect control.

This FAQ dives into the key specifications, manufacturing principles, advantages, and limitations of LSAW and SSAW pipes, and guides selection based on field conditions such as pressure class, installation route, defect risk, and regulatory acceptance.

What is LSAW Pipe

LSAW Pipe, or Longitudinal Submerged Arc-Welding Pipe (also known as SAWL pipe), is manufactured using steel plates as the raw material. The plates are shaped using a molding machine and then undergo double-sided submerged arc welding. This process imparts the LSAW steel pipe with superior ductility, weld toughness, uniformity, plasticity, and excellent sealing properties.

Diameters range and performances of LSAW pipe

The diameter range of LSAW pipes is broader than that of ERW pipes, typically spanning from 16 inches to 60 inches (406 mm to 1500 mm). They demonstrate excellent performance in terms of high-pressure resistance and low-temperature corrosion resistance.

Octal has LSAW pipe on sale.

LSAW Pipe/SAWL Pipe (JCOE Pipe) Manufacturing Flow Chart

LSAW Pipe Moulding Machine

LSAW pipe moulding machine

LSAW Pipe Manufacturing Video

Applications of LSAW pipe

LSAW pipes are extensively used in oil and gas pipelines, particularly where large diameter and thick-walled pipes with high strength are required for long-distance transportation. They are also utilized in construction projects that demand robust strength, such as water treatment facilities, thermal industries, and bridge construction. According to API specifications, LSAW pipes (also known as SAWL pipes or JCOE pipes) are specifically designed for large-scale oil and gas transportation, especially in scenarios where pipelines traverse urban areas, cities, and seas. These applications fall under class 1 and class 2 areas.

SSAW Pipe (HSAW Pipe)

SSAW Pipe, or Spiral Submerged Arc-Welding Pipe (also known as HSAW pipe or Helical SAW), features a welding seam that resembles a helix. It employs the same submerged arc welding technology used in LSAW pipes; however, the key difference lies in the welding method. While LSAW pipes are welded longitudinally, SSAW pipes are spiral welded. The manufacturing process involves rolling a steel strip at an angle to the pipe’s centerline, which creates a spiral welding seam during the forming and welding stages.

SSAW Pipe Manufacturing Flow Chart

SSAW Pipe Manufacturing Video

SSAW pipe (HSAW Pipe) Size range and Features

The diameter range of SSAW pipes spans from 20 inches to 100 inches (406 mm to 2540 mm). One of the key advantages is that we can produce various diameters of SSAW pipes using the same size steel strip, allowing for versatile applications of the raw material. Additionally, the welding seam is designed to minimize primary stress, providing good performance under stress conditions.

However, there are some disadvantages, including challenges with physical dimensions. The length of the welding seam is longer than the pipe itself, which can lead to defects such as cracks, air holes, cinder inclusion, partial welding, and issues with welding force during the pulling process.

Applications of SSAW pipe

For oil and gas pipeline systems, the petroleum design specifications restrict the application of SSAW pipes (HSAW pipes) to class 3 and class 4 areas. Additionally, these pipes are used in construction structures, water transportation, sewage treatment, the thermal industry, and various building projects.

LSAW Pipe better than SSAW Pipe

LSAW (Longitudinal Submerged Arc-Welding) pipes are often considered superior to SSAW (Spiral Submerged Arc-Welding) pipes for several reasons:

Welding Quality: LSAW pipes are welded longitudinally, which typically results in a more uniform and consistent weld seam. This can lead to better mechanical properties and reduced risk of defects compared to the spiral welds found in SSAW pipes.
Strength and Durability: The longitudinal weld in LSAW pipes generally provides higher strength and better resistance to internal pressure. This makes them more suitable for high-pressure applications, such as in critical oil and gas pipelines.
Dimensional Accuracy: LSAW pipes tend to have better dimensional accuracy and straightness compared to SSAW pipes. This can facilitate easier installation and alignment in pipeline projects.
Thickness Range: LSAW pipes can be produced in thicker wall sections than SSAW pipes, making them more suitable for applications that require enhanced strength and durability.
Application Versatility: LSAW pipes are often preferred for high-stress applications, including those in urban areas and critical infrastructure, where reliability is paramount.
Regulatory Acceptance: Many regulatory bodies and industry standards favor LSAW pipes for key pipeline projects, leading to broader acceptance in critical applications compared to SSAW pipes.
Reduced Risk of Defects: The manufacturing process of LSAW pipes minimizes the risk of defects such as cracks, air holes, and inclusions, which can be more prevalent in SSAW pipes due to their spiral welding process.

Overall, while both LSAW and SSAW pipes have their applications, LSAW pipes are often favored for their superior mechanical properties, quality, and suitability for high-pressure and critical applications.

Why Choose Octal Pipe

When choosing between LSAW pipe and SSAW pipe, the decision should be based on a comprehensive assessment of pipeline route, pressure rating, defect tolerance, and lifetime performance. For high-pressure trunklines and critical oil & gas transmission projects, LSAW often holds the advantage due to its superior weld uniformity, dimensional accuracy, and lower defect probability. SSAW pipes remain competitive in large-diameter, lower-pressure contexts where material efficiency and cost optimization are prioritized.

Octal Steel provides both LSAW and SSAW pipes manufactured under stringent quality control and in compliance with industry standards. With full traceability, rigorous testing, and expert technical support, Octal Steel ensures that your pipeline design aligns with operational reliability, safety requirements, and cost targets. Choosing the right pipe type is not merely a material decision—it is a strategic foundation for the long-term success of your infrastructure projects.

Differences between ERW and HFW Steel Pipe

Amily Zhang — Thu, 31 Aug 2017 03:12:48 +0000

In welded steel pipe production, ERW (Electric Resistance Welded) pipe and HFW (High-Frequency Welded) pipe are two closely related but distinct concepts. ERW refers broadly to the electric resistance welding process, which may use low, medium, or high-frequency currents to generate heat and form the weld. Within this category, HFW pipe is a specific subset of ERW pipe, produced exclusively by high-frequency induction or contact welding.

The development of HFW technology has significantly improved weld quality, penetration depth, and production efficiency, making it especially suitable for line pipe, structural pipe, and mechanical tubing where higher integrity and tighter dimensional control are required. While ERW can also refer to ordinary low-frequency processes once used for thin-wall or non-critical applications, in modern practice, most ERW steel pipes for oil and gas pipelines are in fact HFW pipes.

What is ERW steel pipe?

ERW steel pipe is manufactured through low or high frequency resistances Electric Resistance. Welding seam is in longitudinal. During the ERW pipe welding processes, the electric current will make the heat when flow through the contact surface of the welding area. It will heat the 2 edges of the steel to a point that the edges can form a bond. Meanwhile with the combined pressure, the edge of the pipe billet steel melted and extruded together.

Usually ERW pipe maximum OD is 24” (609mm), for larger dimensions pipe will be manufactured in SAW.

What kind of pipes (standards) could be made in ERW processes

The answer is there are a lot of pipes (standards) could be manufactured by ERW process. Here below we list for the most common standards in pipelines.

Stainless steel ERW pipe/tube standards and specifications

ASTM A269 stainless tube
ASTM A312 Stainless pipe
ASTM A270 sanitary tubing
ASTM A790 ferritic/austenitic/duplex stainless pipe

Carbon steel pipe in ERW

ASTM A53 Grade B and A (and Galvanized)
ASTM A252 pile pipe
ASTM A500 structural tubing
EN 10219 S275, S355 pipe
ASTM A134 and ASTM A135 pipe

API ERW Line pipe

API 5L B to X70 PSL1 (PSL2 shall be in HFW process)
API 5CT J55/K55, N80 casing and tubing

And etc.

ERW steel pipe application and usage

ERW steel pipe used for transporting gas and liquid objects such as oil and gas, could meet the low and high pressure requirement. In recent years, with the development of ERW technology, more and more ERW steel pipe used in the oil and gas fields, automobile industry and so on.

Advantages of ERW pipe

High efficiency, low cost, material saving, easy automation.

What is HFW steel pipe?

It shall be noted that HFW pipe is a type of ERW pipe.

High frequency welding (HFW) steel pipe is that ERW pipe produced with a welding current frequency equal to or greater than 70 kHZ. Through high-frequency current welding resistance, the heat generated in the contact objects, so the objected surface are heated to the plastic state, then with or without forging to achieve a combination of steels. HFW is a solid resistance heat energy. The high frequency current pass through the metal conductor, will produce two peculiar effects, skin effect and proximity effect. And HFW process is to use the skin effect to concentrated on steel object surface, use proximity effects to control the position and the power of the high-frequency electric current flow path. Since the speed is very high, the contacted plate edge could be heated and melted in shore time, then extruded through docking process.

Advantage of HFW pipe

and In the welding process, HFW steel pipes do not need to add filling meta. So it has fast welding speed and high efficiency in production. HFW pipe is widely used in the fields of oil and gas transportation, oil well pipeline, building structure and various kinds of mechanical pipe. However, HFW steel pipe quality is affected by many factors, such as raw material and process. And the production quality control become difficult. So the yield and welding process still need to be improved continuously.

Differences between ERW and HFW steel pipe

First is to know the differences of the ERW, HFW welding processes.

ERW welding process refers the heat generated by the resistance to current flow that pass through the jointed metals. So a large current is needed to electrify the whole surface of the steel plate or coil to the length of welding. In the ERW welding process, the electric current that pass through the entire conductor is at 50/60 Hz.

HFW welding process is not the same case with the high-frequency process, since it’s only a section of the steel metals is heated by the induction of electric coil. High-frequency is generated by either AC or DC current. In these cases, the constant current welding generator and constant voltage high-frequency welding generator are used.

Constant current welding machine generates power in 100-800 kHz. In the elder processes, the conversion of 60 Hz, AC current to HF was done by using triode and tank circuits. New welding machine uses metal oxide silicon, filed-effect transistors, usually associated with parallel resonant circuit. The constant voltage version generators use insulated gate bipolar transistors designed to power about 2000 kW with frequency rages of 100-600 KHz.

There are two distinct features of HF current than 60 Hz line current:

While the 60 Hz line frequency current flow through the whole conductor but HF current flow only on the surface of the conductor, so it is “skin effect”.
While two conductors carrying HF current are placed close to one another an the current concentrates on the two adjacent surfaces of the conductors, it is “proximity effect”.

HFW current distribution: The current flows in the surface of the metal or the conductor. Both conductors are placed in close proximity with most of the HF current flowing on the adjacent sides of the conductors.

HFW is required in API 5L PSL2 ERW steel pipe

According the API 5L and ISO 3183 specification, for PSL 2 pipes in welded process the HFW welding is a mandatory requirements for ERW steel pipes. As it is an improvement from the inherent problems of hardness, lack of fusion and susceptibility of stress corrosion cracking (SCC).

ERW steel pipe includes HFW steel pipe

ERW is general designation of resistance welded steel pipes. It can be sorted into two types: alternated current welding (AC) and direct current welding (DC). According to different frequency, AC welding can be divided into low frequency welding, intermediate frequency welding, ultra frequency welding and high frequency welding. The high frequency welding (HFW) is mainly used in ordinary or thin wall steel pipe. It includes contact welding and induction welding. Direct current welding is generally used for small caliber steel tubes. In general, HFW is one of ERW production methods, it adopts the high frequency welding process.

To summarize the relationship, all HFW pipes are ERW pipes, but not all ERW pipes are HFW pipes. The distinction lies in the welding frequency and the resulting weld quality. ERW encompasses multiple resistance welding methods, while HFW represents the advanced, high-frequency process used predominantly in modern pipeline and structural applications.

As part of its product range, Octal Steel supplies both ERW and HFW steel pipes, manufactured in compliance with API 5L, ASTM, and EN standards. Each pipe undergoes strict inspection to ensure weld integrity, dimensional accuracy, and mechanical performance. For clients in oil & gas, construction, and mechanical industries, Octal Steel delivers reliable welded pipe solutions with full certification and traceability.

Differences between 3PE (3LPE Coated Pipe) and FBE Epoxy Coating Pipe

Vicky — Wed, 30 Aug 2017 03:57:00 +0000

3LPE (3PE) and FBE (Fusion Bonded Epoxy) are two of the most common epoxy-based corrosion protection options used when steel pipe is specified for buried or submerged service. 3LPE (3PE) coated pipe is a three-layer external coating system—FBE primer + adhesive + polyethylene top layer—built for stronger mechanical protection and a high-performing moisture barrier in aggressive soil or handling conditions. FBE-coated pipe uses fusion bonded epoxy as a thin-film coating that can be applied externally and is also widely used as an internal lining, especially where a thinner epoxy system is acceptable.

Here is the answer briefly:

FBE pipe is coated with fusion bonded epoxy. It can be used for internal and external coating, and is commonly selected for internal lining and as an external epoxy layer where a thinner coating is acceptable.

3LPE (3PE) coated pipe uses a three-layer system: FBE primer + adhesive + polyethylene top layer. It is mainly used for external coating where stronger mechanical protection and moisture barrier performance are required.

3LPE vs FBE (Quick Comparison)

Item	3LPE (3PE / 3LPE coated pipe)	FBE (Fusion Bonded Epoxy)
Coating structure	3 layers: FBE + adhesive + PE	1 layer (common) or 2 layers (dual-layer FBE)
Typical use	External coating for buried/submerged pipelines	Internal lining and external coating (thin epoxy system)
Typical thickness	Multi-layer system (often in the mm range overall)	400–600 μm typical for many FBE applications
Mechanical protection	Strong (PE top layer improves impact/abrasion resistance)	Moderate (epoxy film is hard but can be less forgiving to mechanical damage)
Moisture barrier	Excellent	Good, but humidity and mechanical damage can be limiting factors
Common selection driver	Harsh soil, aggressive environment, higher mechanical risk	Internal corrosion control, thin external epoxy requirement, temperature window, project preference

3LPE/FBE coated pipe application

3PE/3LPE coated pipe and FBE Epoxy coating/coated steel pipe are widely used in pipeline systems for the transmission of oil, gas, water and other fluids. They have highly resistance to corrosive from chemicals, moisture, harmful environment etc.

In practice, 3lpe coated pipes are most often selected for external corrosion + mechanical protection on buried/onshore or sub-sea lines (soil stress, back-fill abrasion, moisture barrier). FBE is frequently used as an internal lining choice for flow efficiency and internal corrosion protection, or as an external coating where mechanical damage risk is controlled by construction method and additional protection.

What kind of pipes could be coated with 3LPE/3PE or FBE

Almost all kinds of steel pipes can be coated with FBE or 3LPE/3PE, including:

Stainless steel pipe
ASTM A312, ASTM A269 stainless pipe

Carbon steel pipe
API 5L line pipe from Grade B to Grade 80, ASTM A53 pipe (Hot dipped galvanized steel pipe), ASTM A106 pipe, ASTM A252 pipe, ASTM A134 and A135, ASTM A333

Alloy steel pipe
ASTM A335

Nickel Alloy pipes

CRA clad or lined pipe

For RFQs of 3lpe coated pipe, it helps to specify: pipe standard/grade, OD/WT, coating application length (full length or cutbacks), and whether the line is buried, directional drilling, offshore/sub-sea, or above-ground—because those conditions typically drive the coating class, thickness, and inspection scope.

What is FBE (Fusion Bonded Epoxy) coating steel pipe?

FBE coating pipe is a fusion bonded epoxy coated steel pipe. It can be applied as an external or internal coating. The coating is typically applied as a dry powder onto a heated pipe surface, forming a continuous epoxy film with strong adhesion. A common thickness range for many FBE applications is 400–600 μm. Once cured, the FBE film forms a hard surface with good chemical resistance and stable adhesion.

FBE Epoxy coated pipe Features

FBE coating is widely used because it offers:

Good high-temperature performance (commonly specified within approximately -40°C to 85°C, depending on project requirements)
High strength and anti-bending performance of the coating film
Strong adhesion and good integrity against soil stress and wear in many buried service conditions

At the same time, FBE can be more vulnerable where mechanical damage and humidity exposure are severe—this is one reason 3LPE systems are often selected for external protection in harsher environments.

How many types for the FBE Epoxy coated pipe?

FBE coating systems are commonly specified as:

• Single-layer FBE (widely used and cost-effective)

• Dual-layer FBE (often used where better impact resistance and flexibility are required, such as tougher offshore or construction environments)

It developed from 1950s, and industrialization in 1960s. FBE pipe have two kinds: One layer and two layers pipe. FBE Dual layers coated pipe is recommended to applied for the offshore pipelines and the pipelines systems that operated in the tough environments, it provides high performances on the impact resistance and flexibility. Offers suitable protection for the coating from the damage during transportation and construction.

While FBE single layer coated pipe is the generally type for the FBE coated pipe. It offers a rough, non-slip surface for a pipeline that need concrete coating. A special fusion bonded epoxy powder mixed with solid epoxy resin and other adhesive material that helped to adhere to pipe surface.

What is 3LPE Coated pipe?

3LPE coated pipe includes three layers: a first epoxy layer (FBE), a middle adhesive layer, and an outer polyethylene (PE) layer. Compared with a single epoxy film, 3LPE coating improves mechanical protection, electrical resistance, waterproofing, wear resistance, and long-term aging performance in buried service.

For engineering documents, 3lpe coating is typically specified as a layer build-up plus a minimum total coating thickness by pipe OD and coating class. When you purchase 3lpe coated pipe, confirm not only “3LPE” wording but also thickness class and test list—this is usually what determines

3LPE coated pipe include 3 layers:

• First layer (FBE): fusion bonded epoxy, typically ≥ 100 μm

• Second layer (adhesive): bonds epoxy and PE, typically 170–250 μm

• Third layer (PE): polyethylene outer layer that provides strong moisture barrier and mechanical protection

Because it combines epoxy adhesion with a PE barrier and toughness, 3LPE coated pipe is widely used for buried pipelines transporting water, gas, and oil.

3LPE coating thickness

In practice, 3LPE coating thickness is specified by the project standard and service environment (soil conditions, backfill quality, handling risk, and expected lifetime). The system thickness is defined by the three layers together rather than a single film.

Typical project specifications define:

• Minimum FBE thickness (as the base anti-corrosion layer)

• Adhesive thickness range (to maintain bonding performance)

• PE thickness (to deliver barrier + impact/abrasion resistance)

Cost-wise, 3LPE coating cost is usually influenced by pipe OD, coating thickness class, surface preparation level, inspection scope, and batch quantity—because these drive material usage, line time, and QA workload.

3LPE Layer	Function	Typical Thickness (Project-Specified)	Common Inspection / Acceptance Point
FBE (Epoxy)	Primary corrosion protection + adhesion to steel	> 100 μm (as specified)	DFT / cure control (per project spec)
Adhesive	Bonding layer between epoxy and PE	170–250 μm (as specified)	Peel adhesion (per project spec)
PE Topcoat	Mechanical protection + moisture barrier	To meet total thickness class (e.g., ~1.8–3.7 mm total, OD/class dependent)	Holiday test / impact / thickness mapping (per project spec)

Note: total 3lpe coating thickness is normally defined by coating class and pipe OD in the project coating standard, so the RFQ should reference the required class and the acceptance test list.

3LPE coating process

A standard 3LPE coating process is designed to ensure adhesion, continuity, and consistent thickness control. While exact parameters vary by project specification, the typical workflow includes:

• surface preparation (cleaning and abrasive blasting to the specified cleanliness/roughness)

• Induction heating (bringing the pipe to the target temperature window)

• FBE application (spray epoxy powder, then gel/cure)

• Adhesive layer application (to bond epoxy and PE)

• PE extrusion/wrapping (outer protective layer)

• Cooling and inspection (visual, thickness checks, holiday detection, and repairs if required)

This is why 3LPE is commonly selected for external pipeline protection where handling, transport, backfill, and long-term soil exposure create higher mechanical risk than a thin epoxy film can comfortably tolerate.

3LPE coating standard and tests

A 3LPE system is only as reliable as its process control and verification. Most projects define the coating requirement through a coating standard/specification and then confirm compliance through routine tests and inspection records.Common checks for

3LPE coating standard compliance typically include:

• Coating thickness measurement (FBE/adhesive/PE and total thickness per the spec)

• Holiday detection (to confirm coating continuity and locate pinholes/defects)

• Adhesion / peel strength testing (to verify bonding performance between layers)

• Impact resistance testing (to validate mechanical robustness during handling/back-fill)

• Bend / flexibility testing (as required by the project standard)

• Cathodic disbondment testing (often required for buried pipeline coatings)

• Visual inspection + repair records (defect repair method and acceptance results)

For procurement and site acceptance, the most valuable outcome is a clear, consistent inspection pack that ties coating results back to pipe identity and heat/lot traceability.

3PE/3LPE coated pipe features and advantages

3LPE coated pipe is commonly used for external corrosion protection against outside environments, while FBE is often selected for internal coating against fluid-side corrosion (for example, in chemical service or potable water applications where a thin internal epoxy lining is required by the project).

Durable lifetime

3LPE coated steel pipe have good stability and anti-aging performances under the normal work temperature and pressure conditions, consequently its lifetime can prolong above 50 years.

Corrosion resistance

Due to PE elements structure stability is very high, it is resistant to corrosion of natural gas, liquefied petroleum gas, artificial gas and other chemical subjects, no need secondary anti-corrosion equipment. The chemical of soil does not produce any effects to the pipe.

Flexibility and handling tolerance

3PE/3LPE is a kind of soft and flexible material, it can prolong 5 times length then break. While it is easily to bend and no damage. 3LPE/3PE coating steel pipe can bypass objects and cut the fees of installation.

Good resistance of impact and earthquake

Polyethylene is not fragile under low temperature, there for, it is safe used in the temperature at the range of -60℃~60℃. So it can adapt to going down of pipeline, Work in winter. Due to good impact performances, PE pipeline won’t easily to break.

Excellent wear resistance

Experiments shows that PE pipe wear resistance is 4 times of pipe. especially in area of transporting mud. Compared to varnished pipe, PE coated pipe have better wear resistance.

3PE/3LPE have smooth surface, its manning coefficient is 0.009. Because of smooth internal surface and non-sticking performance, 3PE/3LPE coated steel pipe shows higher ability for transporting, and reduce the loss of pressure and water transporting. Low water permeation characteristic provides improved isolation from sea water compared to the other coating systems and FBE pipe.

Good environment protection performance

3LPE coated steel pipelines in manufacturing process won’t add heavy metal stabilizer, the PE material have no poison and harm, is a kind of green material, and itself can recycled will not cause pollution to the environment.

Excellent electric resistance, anti-static performances.

These properties make PE pipeline suitable for flammable and explosive conditions.

Safe and reliable connection way

3LPE/3PE coating steel pipe mainly use hot melt and fused connection, keep the interface and pipeline connect as a whole. There is no water and gas leakage.

Light, easily to move, and convenient for construction

3LPE layers weight only account 1/8 for steel pipe, easily to move, bend, welding process is convenient and fast, lower fees for whole project, obvious economic benefits.

Since 3LPE and FBE coating can prolong the lifetime of same steel pipe from several years to decades years, it’s required more than more in recent year pipeline projects.As a result of steel pipe corrosion, the whole world suffers average loss about 3% of global GDP per year, about 2.2 trillion dollars in 2015 according newest data. In which, oil, gas and petroleum industry loss account for 45% about 1 trillion dollars in 2015. According by data, more than 70% oilfield has explored easily to corrupt. For example, The US loss has rise up to 26% of direct economic loss , and China account for 10%.

For specification alignment, 3lpe coating standard and test requirements should be stated in the RFQ/ITP (coating class, total thickness, holiday detection, adhesion/peel, impact, and cutback requirements). For regional projects (including 3lpe coating in uae), the key is to follow the EPC/owner coating class and inspection plan rather than relying on “generic 3LPE” wording.
From a commercial view, 3lpe coating cost is mainly driven by pipe OD/length, coating thickness class, surface preparation level, testing scope, quantity, and delivery schedule—so fixing these inputs upfront is the best way to compare offers on a like-for-like basis.

Octal can provie 3LPE coated pipe or FBE coated pipe with different standard and types, please do not hesitate to contact us for an offer if you have such requirement.

FAQ

Q1: What is the main difference between 3LPE (3PE) coated pipe and FBE coated pipe?
A1: FBE is an epoxy film that can be used for internal or external protection, typically as a thinner coating system. 3LPE (3PE) is a three-layer external coating system (FBE + adhesive + PE) designed to provide stronger moisture barrier performance and mechanical protection for buried or submerged pipelines.

Q2: What is the typical FBE coating thickness for epoxy coated steel pipe?
A2: Many projects specify FBE in the 400–600 μm range, but the final requirement depends on the standard, service conditions, and whether it is internal lining, external coating, or part of a multi-layer system.

Q3: How is 3LPE coating thickness defined and why does it matter?
A3: 3LPE coating thickness is defined by the combined thickness of the FBE layer, adhesive layer, and PE outer layer. Thickness matters because it directly affects corrosion protection at the steel interface, moisture barrier performance, and resistance to impact/abrasion during handling and back-filling.

Q4: What inspection items are commonly included under a 3LPE coating standard?
A4: Typical inspection includes thickness checks by layer, holiday detection for continuity, adhesion/peel strength verification, impact resistance testing, and documentation that links coating results to pipe traceability and repair records where applicable.

API 5L PSL1 and PSL2 Differences for the Steel Line Pipe

Amanda — Mon, 28 Aug 2017 06:11:26 +0000

API 5L line pipe (Seamless and welded pipe) of all grades have PSL1 and PSL2 two product specifications, they are different on chemical composition, manufacturing processes, mechanical strength, heat treatment, test records, traceability etc.

Line pipes in API 5L PSL2 is higher than PSL1

a. PSL is the short name of product standard level. The product standard level of line pipe have PSL1 and PSL2, also we could say the quality standard divided in PSL1 and PSL2. PSL2 is higher than PSL1, not only the inspection standard is different, also the chemical property, mechanical strength standards are different. So when place the order for the API 5L line pipe, there should be stated clearly for the size, grades these general specification, also have to clarify the production standard leve, PSL1 or PSL2.
PSL2 is more strictly than PSL1 on the chemical properties, tensile strength, non-destructive test, and impact test.

Different impact test methods for PSL1 and PSL2

b. API 5L PSL1 steel line pipe not required to do the impact test.
For API 5L PSL2 steel line pipe, except Grade X80, all the other grades of API 5L line pipe required the impact test at temperature of 0℃. The average value of Akv: longitudinal direction≥41J, tranverse direction≥27J.
For API 5L Grade X80 PSL2 line pipe, at 0℃ for all the size, impact test the Akv average value: longitudinal direction≥101J, tranverse direction≥68J.

Different hydraulic test for API 5L line pipe in PSL1 and PSL2

c. For API 5L PSL2 line pipe shall perform the hydraulic test for each single pipe, and in the API standard specification not permit to have Non-destructive test replace the hydraulic test, this also is a big difference between Chinese standard and API 5L standard. For PSL1 not required Non-destructive test, for PSL2 shall do the Non-destructive test for each single pipe.

Different chemical composition for API 5L line pipe in PSL1 and PSL2

d. Chemical composition and mechanical strength is also different between API 5L PSL1 line pipe and API 5L PSL2 line pipe. For the detailed specification as below. API 5L PSL2 have restrictions with the carbon equivalent content, where for the carbon mass fraction greater than 0.12%, and equal or less than 0.12%. Different CEQ shall be applied. For line pipe in PSL2 tensile strength have maximum limits. More info please review API 5L Specification part 9.2 and 9.3.

PSL1 vs PSL2 pipe differences summary

PSL1 vs PS2 summary
API 5L PSL2 Sour Service Pipe Specification
NACE Pipe Specification
API 5L PSL1 Pipe Specification

API 5L PSL2 Pipe material specification

Things you need to know about hot dipped galvanized steel pipe

admin — Sat, 05 Aug 2017 00:44:52 +0000

In the realm of steel protection engineering, Hot-Dipped Galvanizing (HDG) represents a classic, century-proven corrosion control strategy that remains irreplaceable. Its technical essence is far more than a simple surface coating; it is a complex process involving physics, chemistry, and metallurgy. The core principle involves immersing a meticulously prepared steel pipe (after pickling and fluxing) into a molten zinc bath at approximately 450°C. Through thermal diffusion, a gradient zinc-iron alloy layer is formed on the steel substrate, achieving a metallurgical bond. This layer provides a unique dual-protection mechanism: firstly, it acts as a dense physical barrier, isolating the steel from corrosive agents. More critically, due to zinc’s more negative electrochemical potential compared to steel, it functions as a sacrificial anode. When the coating is scratched or damaged, zinc corrodes preferentially, providing cathodic protection to the exposed steel by directing galvanic current through an electrolyte (e.g., moisture). This “self-healing” capability is absent in most coating technologies. Consequently, HDG steel pipes demonstrate exceptional durability and low life-cycle cost in outdoor atmospheres, soils, and specific chemical environments. This section will elaborate on its process details, performance advantages, international standards (e.g., ASTM A123, A53), and critical applications.

What is galvanized steel pipe?

Galvanized steel pipe is the carbon steel pipe that are coated with a protective layer of zinc. The zinc layer served as a sacrificial layer, it will get rust before the carbon steel under neath it. Galvanized steel pipe include Two types: hot dipped galvanized steel pipe and cold galvanized steel pipe. Galvanized layer will strengthen the anti-corrosion performances of steel pipe.

Why use zinc as the coated layer?

Why use zinc? Because of zinc element is active than steel element. On one hand, zinc oxide of galvanized steel pipe surface is compact, it can stop oxidation(corrosion). On the other hand, when electric-chemical corrosion has occurred, the first kind of metal corrupted is zinc rather than steel. The zinc layer effect is stop corrosion speed, and prolong the life of steel pipe.

Galvanized steel pipe application

Galvanized steel pipe mainly used in transmission of coal gas, steam. It was used as water pipe, but after several years past, there were many rust in the pipe, and water get yellow color for carrying iron oxide. The water not only polluted dishes or other sanitary ware, but also carrying bacteria produced in the internal surface which not smooth . As a result of the corrosion, the water contains heavy metal element is too much and is harmful to people’s health. For this reason, developed countries gradually banned it using as water pipe since 1960s.

Galvanized steel pipe types

Galvanized steel pipe include two kinds:
1. Hot dipped galvanized steel pipe.
2. Cold galvanized pipe, also called electric galvanized pipe.

Galvanized steel pipe sizes and specifications

Nominal diameter (inch): 1/2~4
Nominal wall thickness (mm): 2.0~4.5
Test pressure index: Diameter: 10.2~168.3 mm 3 MPa
Diameter: 177.8~323.9 mm 5 MPa

Hot dipped galvanized steel pipe introduction

Hot dipped galvanized steel pipe is in manufacturing process using steel pipes of removed rust dipped into zinc liquid of 500℃ temperatures, and making steel surface attached zinc layer so as to achieve the purpose of anti-corrosion.

Hot galvanizing is a kind of effective anti-corrosive treatment, used in kinds of steel structural products. Since 1836 France used hot galvanizing in industry the first time, it have been more than 180 years. However following by the development of cold rolled steel, it has greatly developed in recent decades. With the high-voltage transmission, transportation, communications, the protection products require higher standards, hot galvanizing demand is also increasing.

The processing of hot galvanizing:

Finished pickling – washing – plating – drying – hanging plating – cooling – medicine – cleaning – grinding – hot galvanized finish.

Zinc thickness for hot galvanized steel pipe

Hot galvanized steel pipe zinc layer thickness is 35μm, and the most thick is up 650μm. Instead cold zinc layer thickness is only 5-15μm. Zinc layer have the effects of anti air corrosion and electric chemical protection.

The theory of hot galvanized steel pipe’s zinc layer effect to anti corrosion

In the processing of hot galvanizing, it will formed a film of zinc-steel alloy layer first, above it is pure zinc layer. When the air corroded the zinc layer, it will form a layer of ZnO, Zn(OH)2 and basic zinc carbonate protection film. Which have the effect of anti air corrosion. When this film was destroyed, a new one will form. When the zinc layer destroyed heavily, zinc start up electric chemical protection. Zinc as the first element dissolved. It’s obviously that hot galvanized steel have better anti corrosive performances than cold galvanizing pipe.

How long of hot galvanized steel pipe lifetime?

Galvanized steel pipe have long lifetime. But in different conditions the lifetime of use are different. Generally speaking, 13 years in heavy industrial district, 50 years for ocean environment, 104 years in suburbs, 30 years in city. In fact galvanizing have played a role of anti- rusty, it is no need other rust treatment.

Hot galvanizing process specially suitable for kinds of strong-acid, alkali fog and other strong corrosive conditions. This kinds of fastener used a lot in outside of steel tower contribution.

Cold galvanized steel pipe introduction

Cold galvanized steel pipe is using electric chemical processing coated zinc layer on steel pipe. The zinc layer usually 20~30μm thick.

Manufacturing process of cold galvanized steel pipe:

Degreasing – electroplating – passivation – drying – packaging

Zinc thickness for cold galvanized steel pipe

Cold galvanized steel pipe zinc thickness is 5-15 μm, the layer is dense, and there is no inclusion with organic matter.

Cold galvanization technology is no longer recommend for pipe products.

For more thinner zinc layer reason, countries of the world have gradually forbidding the cold galvanized steel pipe as water pipe and coal gas pipe. But due to cold galvanizing processing have smooth appearance of surface, it always used in manufacturing small pieces which requiring precise plating. Such as screws, Machinery manufacturing, electronics, precision instruments, chemicals, light industry, transportation, weapons, aerospace, atomic energy, etc., in the national economy has great significance.

In summary, Hot-Dipped Galvanized steel pipe offers a robust and long-lasting solution against corrosion, thanks to its reliable metallurgical bond and dual-protection mechanism. At Octal Steel, we adhere strictly to international standards, implementing full-process control from base pipe quality and galvanizing operations to final inspection, ensuring every pipe delivered possesses superior protective properties and mechanical integrity.

Fire Protection Pipe and Connection Fittings

Amanda — Thu, 27 Jul 2017 06:07:56 +0000

The fire protection pipe and connection fittings are mainly used to connect firefighting equipment, conveying fire fighting water and so on. It is also called fire sprinkler pipe and fittings. Due to the special requirements, the thickness and material of the fire protection pipe and fittings have special requirements. According to the regulations, the fire pipeline need to be sprayed red paint, obviously different with other pipeline. Because the fire protection pipe is often in a static state, so it is required more strict. The fire proof pipe and connection fittings must possess pressure resistance, corrosion resistance and high temperature resistance.
According to material, the fire protection pipe can be divided into ductile iron pipe, copper pipe, stainless steel pipe, alloy pipe and composite pipe, plastic pipe.

1. Installation process flow for fire pipeline system

Installation preparation → dry pipe installation → alarm valve installation → vertical pipe installation → spray layered Sexagenarian cycle pipe, hydrant and branch pipe installation → water flow indicator, fire water pump, high water tank, water pump coupling installation → pipeline trial pressure → pipeline flushing → spray head branch pipe installation ( system comprehensive test pressure and flushing ) → throttle device installation → alarm valve accessories, hydrant accessories, spray head installation → system water test

2. The connection technology of fire protection pipe and fittings

1). General connection fittings for fire pipeline

When the pipeline of fire hydrant water supply system adopts hot dip galvanized steel pipe, welding shall not be used. If the fire protection pipe adopts material that the internal wall don’t carry out anti-corrosive treatment, it can be welded for connection. But the pipeline welding should meet the relevant requirements. Automatic sprinkler system pipe cannot be welded, it should use threaded, flange and other connection.

In hydrant water supply system, hot dipped galvanized steel pipe that the pipe diameter is greater than 100 mm should be connected by flange connection or groove connection.
If the pipe diameter is greater than 100 mm, it is not clearly indicated in automatic sprinkler system, threaded connection cannot be used. It is only required that flange connection or groove connection point shall be arranged at a certain distance on the pipe whose diameter is greater than 100 mm.

When pipeline of the fire hydrant water supply system and automatic sprinkler system adopt flange connection, the threaded flange is recommended. AS the welding flanges are used, the second zinc plating shall be carried out.

If any fire proof pipe section need to change the pipe diameter, the connection pipe fittings that complied to the standard shall be used.

2). Groove (clamp) connection for fire protection pipe and fittings

The groove connection (pipe joint) and fire steel pipe groove depth shall conform to the requirements of the groove type pipe joint. The maximum working pressure of groove pipe joint with nominal diameter of DN250 or less is 2.5 MPa. The maximum working pressure of groove pipe joint with nominal diameter of DN300 or more is 1.6 MPa.

Flexible joints can be used for vibration places and buried fire protection pipe, rigid joint fittings shall be adopted in other places. When the rigid joints fittings are used, a flexible joint shall be arrange for every 4-5 rigid joints.

3). Threaded connection in fire pipeline systems

For fire proof pipe, the hot-dip galvanized welded steel pipe or hot-dip galvanized seamless steel pipe whose inner and outer wall diameter is less 100 mm can use threaded connection. When the hot-dip galvanized ERW steel pipe is adopted in the system, the malleable iron threaded pipe fittings can be used. If the hot-dip galvanized seamless steel pipe is adopted, the forged steel thread pipe fittings can be used.

If the wall thickness of steel pipe is less than the delta < Sch30 (DN≥200mm r) or less than the delta < Sch40 (DN < 200 mm), the threaded connection shall not be used.

When the fire protection pipe adopts 55 °taper pipe threads (Rc or R), the threaded interface can be sealed with PTFE. When the pipeline used 60 °taper pipe threads (NPT), it is appropriate to use the sealant as the sealing of the threaded interface. The sealing strap shall be applied on the male thread.

The fire pipe that diameter is less DN50 shall not use threaded union, the monomer reducing joint shall be used at the variable diameter of pipe.

4). Welded or flange joint connection fittings

According to connection, the flange can be divided into flat welding flange, welded flange and threaded flange, etc. The selection of flange muse comply with steel pipe flanges standard, steel butt welded seamless pipe fitting standard, Teflon coated gaskets for pipe flanges standard.

If the hot-dip galvanized steel pipe adopts flange connection, the threaded flange shall be selected. When the fire pipeline system used the fire proof pipe that the internal wall are not carried out anti-corrosive treatment, the welding connection can be used.

Differences Between Seamless Steel Pipe and Welded Steel Pipe

Amanda — Mon, 03 Jul 2017 19:22:26 +0000

Seamless steel pipe is manufactured by the round steel billet, through hot rolling, cold rolling or cold drawn processes, no seam on the pipe body.
Welded steel pipe is manufactured by flat steel plate, with welding seam on the pipe body. Including ERW pipe, LSAW pipe, SSAW pipe.

Octal tells you the differences between seamless pipe and welded pipe on raw material, manufacturing processes, performances, appearances, sizes, applications, cost prices etc.

How is Seamless steel pipe made.

API 5L and ASTM Seamless steel pipe adopts steel ingot or solid tube as raw material through the perforated tube, then can be formed by hot rolled, cold rolled or cold drawn. Hot rolled seamless steel pipe is formed by billet forging, perforation, rolling, shaping and other processes. For Large diameter pipe, and thick walled seamless pipe usually made in this way. Cold drawn seamless pipe used cold-drawn forming technology. The material strength is relatively low, the appearance and internal control surface is smooth. Small diameter and thin wall seamless pipe usually made in this way. The seamless steel pipes are rolled by carbon structural steel, low alloy structure steel or alloy structure steel and stainless steel. Seamless steel pipes applied in different industries: Line pipe for pipelines, thermal services, mechanical industries, chemicals etc.

How is Welded steel pipe made

API 5L or ASTM welded steel pipe includes LSAW pipe, SSAW pipe, and ERW steel pipe. These pipes are made with steel strip or steel plate. The manufacturing processes first bending the steel plate, then welded into circular, square and other shapes. Welded steel pipe has the characteristics of high production efficiency, low cost and saving material. It has been widely applied to aviation, aerospace, energy, electronics, automobile, light industry and other industries. With strong corrosion resistance in the acidic environment.

Why Should You Prefer To Buy Seamless Steel Pipes?

The reason why most of the people prefer seamless steel pipe over welded steel pipe is that seamless pipes can withstand extremely high pressure without cracking. But the seam or welded pipes cannot do the same as the welded points are vulnerable to cracking up under high pressure. Furthermore, it is very easy to accurately calculate the pressure of seamless pipes. Seamless pipes are also thinner and lighter than welded ones, and they also have uniformity of shape as they are made up of uniform extrusion of an alloy. If you are looking to buy the best quality of seamless steel pipes, you should use Octal Steel API 5L and ASTM seamless steel pipes.

Seamless vs welded steel pipe differences summary

API 5L / ASTM Seamless steel pipe and ERW welded steel pipe have some differences as below:

1. Appearance difference

Seamless steel pipe used steel billet as raw material. The outer surface defects of billet cannot be eliminated by hot rolling process, it is only polished after the product finished. In the process of wall reduction, the defect can only get partially eliminated.

Welded steel pipe made by hot rolled coil as raw material, the surface quality of coil is just the pipe’s surface quality, and easy to control.The surface of hot rolled coil have high quality.

So Welded steel pipe surface quality is much better than seamless steel pipe.

2. Molding process differences

Seamless steel pipe can be formed one time in the rolling process.
Welded steel pipe is manufacturing with steel strip or steel plate, through bending and different welding processes.

3. Performance and Usage

Seamless steel pipe has better pressure capacity, strength is higher than ERW welded steel pipe. So it is widely applied in high pressure equipment, and thermal, boiler industries.
Generally the welding seam of the welded steel pipe is the weak point, the quality affect overall performance.

In general, welded steel pipes can withhold 20% less working pressure than seamless ones. This reliability is the prime factor why people go for seamless steel pipe. As a matter of fact, all the industrial pipelines are done with seamless pipes only because the pipes undergo extreme thermal, chemical and mechanical workloads. Welded pipes are more preferred in aerospace, automobile and electronics industries where the budget is comparatively low, and so is the work pressure put on the pipes.

4. Available Sizes differences

For most of seamless steel pipe manufacturers in China, they produce original seamless pipe sizes maximum OD in 20 inch, 508 mm. Where usually is smaller than 16 inch, 406.4 mm, because of the equipment limits. And if client would like to purchase the seamless steel pipe more than above sizes, then hot expanding machining shall be used. But usually this kind hot expanded seamless steel pipe quality could not compare with the original seamless steel pipe.
On the contrary, welded steel pipe don’t have these limitations, sizes available from 1-1/2 inch 48.3mm to 100 inch 2540 mm.

5. Cost and prices

Usually the seamless steel pipe cost is higher than welded steel pipes, because the raw material, manufacturing equipment and processes. But sometimes by the market pressure, welded pipe is more expensive, so if you met this situation, don’t hesitate to purchase the seamless steel pipe for the same dimensions.

API 5L Welded Steel Pipe

API 5L Seamless Steel Pipe

What is Common Defects for Welded Steel Pipes

Amanda — Sun, 02 Jul 2017 08:39:09 +0000

For welded and seamless steel pipes, no matter how perfectly designed and fabricated they are, would certainly have some defects in some areas. A welded defect is a flaw that inhibits the usefulness of the steel pipe and there is a wide range of these effects with causes.

Testing method for the defects on the steel pipe

Normally, there are various testing methods to ensure the appropriate weld standard has been applied to the steel pipe but during fabrication, probably due to some errors, the pipe ends up getting some defects. We could find these defects by visual inspection, non-destructive inspection, Magnetic inspection, hydrostatic test and etc.

Common defects for welded steel pipe

We will take a look at some common defects that occur on welded steel pipes and they are explained below:
1. Lack of fusion
This is simply the poor adhesion of the weld bead to the base metal. A weld bead that doesn’t begin at the weld groove’s root is known to be incomplete penetration. This incomplete penetration forms cervices and channels in the weld’s root which would lead to various problems in the steel pipe because substances that are corrosive could settle in those places.
Lack of fusion usually occurs whenever there is a lack of adherence to welding procedures with possible causes such as electrode manipulation, electrode angle, arc length and current setting. There are various defects and they are classified as critical and non-critical.
2. Undercut
Undercutting in a steel pipe can reduce its cross-sectional thickness on its base which eventually reduces its weld and workpieces strength. A particular reason for this defect type is excessive current which causes the edges of the joint to melt and drain into the weld which ends up leaving a drain-like impression along the weld’s length. Another cause is that if a poor technique that is used doesn’t deposit sufficient filler metal along edges of the weld. There is another cause which occurs from using a wrong filler metal because a temperature gradient will be created between the center of the weld and the edges.
Other causes of undercutting are slow speed, excessive length of the arc, dampened electrode and electrode angle.
3. Inclusions
This defect is of two types – linear inclusions and rounded inclusions. Linear inclusions come as a result of the presence of flux or slag in the weld. Slag is formed when a flux is used which is why this defect type usually results from welding process that makes use of flux like submerged arc welding, flux-cored arc welding and shielded metal arc, it may also occur in gas metal arc welding.
4. Gas Inclusion
This is a wide variety of defects which include pipes (wormholes), blow holes and porosity. The main cause of this defect is gas entrapment within solidified weld. The formation of gas can be caused by any of the following: excessive moisture from the electrode, the high sulfur content in the electrode or wrong welding current.
5. Cracking
This could be caused by a thermal shrinkage or a combination of strain that accompanies phase change and thermal shrinkage. In a case of welded stiff frames, a combination of following the wrong procedure and poor design might cause cracking and high residual stress.
If steel pipes that have a carbon content more than 0.2% are being welded, then self-cooling might rapidly cause some form of brittleness to occur which eventually make the pipe develop cracks.

Standard criteria for the pipe defects in API 5L

In API specification 5L part 9.10, there are standard criteria for the pipe surface conditions, imperfections and defects.
9.10.1.1 All pipes shall be free from defects in the finished condition
9.10.1.2 All pipes shall be free from cracks, sweats and leaks.
9.10.1.3 The acceptance criteria for imperfections found by non-destructive inspection shall be complied to Annex E.
9.10.2 Undercuts in SAW and COW pipes found by visual inspection shall be investigated, classified and treated as follows.
a. Undercuts that have a depth ≤ 0.4 mm (0.016 in) are acceptable, regardless of length, and shall be treated in accordance with Clause C.1.
b. Undercuts that have a depth >0.4 mm (0.016 in) but ≤ 0.8 mm (0.031 in) are acceptable provided that: Individual lengths are ≤ 0.5 t, and their individual length depths are ≤ 0.1 t, and there are no more than two such undercuts in any 300mm (12.0 in) length of weld, and all such undercuts are treated in accordance with Clause C.2.
c. Undercuts that exceed the limits specification in item b) shall be classified as defects and shall be treated in accordance with Clause C.3.
9.10.3 Arc Burns, Arc burns shall be classified as defects.
9.10.4 Laminations
9.10.5 Geometric deviations
9.10.6 Hard Spots
9.10.7 Other surface imperfections

Repairs for the steel pipes

Since the defects comes with the pipe, we could do some repairs for these defects, which is allowed in the API 5L standard and other ASTM pipe standard. Repair acceptance criteria could be discussed in the contract before the production. For more details please check the API 5L specifications and the related documents.