The Difference Between ERW and EFW Pipe

Two of the most common methods to produce pipe are Electric Resistance Welding (ERW), and Electric Fusion Welding (EFW). Both processes involve a coil of steel being continuously fed through a series of rollers/dies which shape the flat steel into the desired shape of the pipe. 

You can find more information on our web, so please take a look.

How the edges of the steel plate are joined together are what makes the ERW and EFW processes different. 

Over the course of this Blog, we will discuss both processes, the benefits each have, and why you would use ERW or EFW pipe.

DISCOVER MORE ABOUT PIPE 

ERW vs EFW Pipe Forming Process

As stated above, once the flat steel plate has been formed into the pipe shape the two edges need to be joined together.

In an ERW process, a high frequency electrical current is used to heat the edges of the steel plate just before the final shaping rollers/dies join them together to create the circular pipe shape. 

A high frequency Is prevalent in modern piping because the low frequency current had several deformities including: seam corrosion, hook cracks and the seam bonding was inadequate.  

ERW pipe has a weld seam that runs along the length of the pipe. ERW pipe will either clean/trim the weld seam, or just use a roller/die to smooth out the seam to match the outside diameter; leaving a visible weld seam on the inside diameter.

For EFW (also known as electron beam welding), an electron beam (laser) is used to heat the edges prior to the rollers/dies joining them together. 

EFW pipe also has a weld seam that runs along the length of the pipe. This seam is cleaned/trimmed on the outside, and inside, diameter for EFW pipe.

EFW pipe is a cost effective solution for environments that require high pressure and are corrosive. This type of pipe has better strength and durability. This pipe is stronger, denser and more uniform as compared to ERW because of its fusion method.

Finally, the pipe continues to go through another few sets of rollers/dies to ensure its final shape before each section of pipe is cut to length.

Benefits of ERW

The ERW manufacturing process is highly efficient and cost-effective. Machinery required for ERW pipe is very common, and with proper care and maintenance can run for decades. As a result, it is the predominant method for producing pipe in the PVF industry. 

Benefits of EFW

The fusion process in EFW manufacturing produces a much narrower “heat affected zone” in the pipe than the ERW process. This translates to a better uniformity of the metal in the pipe, and a higher pressure rating than ERW. 

Combining the higher pressure, with a still cost-effective end product (the initial tooling investment is greater for EFW pipe), means that EFW pipe can be looked at as a substitute for seamless pipe in certain applications.

What is ERW Pipe Used For?

Just as ERW is the predominant pipe manufacturing process, ERW pipe can be found in just about every industry where fluid/media needs to be moved from one location to another. 

Common industries where you would find ERW pipe include: plumbing, HVAC, fire suppression, commercial, aviation, aerospace, automotive, rail, electronics, energy, oil & gas, and industrial.

What is EFW Pipe Used For?

Being viewed as a cost-effective alternative to seamless pipe means that EFW can be used in higher pressure, more corrosive applications where ERW could not be considered. Industries such as petrochemical, textile, food & processing and chemical processing can utilize EFW in areas of their pipelines.

ERW Pipe Specifications

• ERW pipe sizes range from ½” – 48”
• Manufactured in several schedulesranging from schedule 5 to schedule 160 as well as schedule XXS and XS. The schedule used is dependent upon the application and pressure of the piping system.  
• The most common alloys ERW pipe is manufactured from are stainless steel and carbon steel.  
• Ends: plain, bevelled, threaded
• Industry Standards & Specifications:
• ASTM A178: Standard Specification for Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes

EFW Pipe Specifications

• EFW pipe sizes range from 1/8” through 100”.   The availability of these diameters depends on the ASTM specification.  
• Manufactured in several schedules including schedule 10, schedule 40 and schedule 80, etc. These schedules are used in different applications based on the pressure requirements of the system they will be used in.  
• Available in several alloys such as stainless steel, high nickel alloy and carbon steel. This gives flexibility to those installing piping systems. 
• Surface finishes: HF pickled, matt polish, sandblast
• Ends: plain, bevelled, threaded
• Industry Standards & Specifications:
• ASTM A672: Standard Specification for Electric-Fusion-Welded Steel Pipe for High-Pressure Service at Moderate Temperatures
• ASTM A691: Standard Specification for Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-Pressure Service at High Temperatures

Other pipe standards, such as ASTM A53, ASTM A252, and ASTM A312 would apply to both ERW and EFW pipe.

It is important to understand the differences between ERW and EFW pipe to ensure that you are using the correct pipe for your system’s application. Pressure, corrosive environment and budget are just some of the considerations when determining which type of pipe to use. 

Always consult your project and engineering firm prior to installing any pipe into your system to ensure a safe and proper installation. 

STILL HAVE QUESTIONS?

Author:  Kimberly Wallingford, Director of Marketing - Merit Brass and Marcus Estrella, Director of Product Line Management - Merit Brass

Sources:

https://www.nucorskyline.com/globalnav/products/pipe/erw#:~:text=Electric%20resistance%20welded%20(ERW)%20pipe,are%20limited%20to%%20inches.

SAW vs ERW and EFW Welded Steel Pipe (hu-steel.com)

https://www.oshwin.com/stainless-steel-efw-pipe.html

Related links:
Pros And Cons of All The Different Seam Tracking Solutions (2)
Manual Vibration Suction Metal Electrostatic Powder Spraying ...
Ramen Making Equipment - High- Efficiency Noodle Solutions

Great wall equipment supply professional and honest service.

https://www.husteel.com/news355_146.html#:~:text=EFW%20steel%20pipe%20(Electric%20Fusion,the%20formation%20of%20the%20weld.

Stainless Steel EFW Pipe | SS 304/316 EFW Pipe (oshwin.com)

PHMSA: Stakeholder Communications - Manufacturing Process (dot.gov)

What are the main equipment in the erw pipe production line? (eastern-steels.com)

2/7/ 7:26:08 AM

ERW pipe manufacturing process includes HFW. ERW have low, medium, high frequency welding processes, and HFW is specially for high-frequency electric resistance welding. The differences between ERW and HFW steel pipe, is EFW is a type of ERW process for ordinary and thin-wall thickness steel pipes.
ERW pipe: Electric Resistance Welded Pipe
HFW pipe: High Frequency Welding pipe

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 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 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 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. So, ERW steel pipe includes HFW steel pipe.

Want more information on erw welded pipe equipment factory? Feel free to contact us.