ERW pipe and seamless pipe are both steel pipe, and the difference is how they are made: ERW pipe is formed from steel strip and welded along its length, while seamless pipe is made from a solid billet with no weld at all. Hotline Steel Trading supplies both from Dubai to projects across the UAE, with ERW steel pipe from ½″ to 24″ and seamless pipe from ¼″ to 16″. This guide compares them so you can specify the right pipe and request a quote.
At a glance
- ERW pipe is rolled from steel strip and welded by electric resistance.
- Seamless pipe is pierced and rolled from a solid billet, so there is no weld seam.
- Seamless pipe is the usual choice for high pressure and high temperature lines.
- ERW pipe is cost effective and available in larger diameters and fixed lengths.
- Both are made to standards such as API 5L and ASTM A53.
In this guide
What is ERW pipe?
ERW (electric resistance welded) pipe is made by forming flat steel strip into a tube and joining the edges with a weld created by electric current. The weld runs along the full length of the pipe, and the excess weld metal is trimmed so the surface is smooth.
Because ERW pipe starts as coil, it can be produced in long runs, consistent wall thicknesses and a wide range of diameters at a lower cost than seamless pipe. Hotline Steel Trading supplies ERW pipe with outside diameters from ½″ to 24″ and wall thicknesses from 1.6 mm to 14.2 mm depending on diameter, to API 5L, ASTM A53, DIN, BS and API 5CT. Fixed lengths of 6 m and 12 m are available, as well as single random lengths of 4.8 m to 6.7 m and double random lengths of 10.5 m to 12.5 m. ERW pipe is widely used in construction, water lines, structural work and general industrial piping, as covered in our guide to the top applications of ERW pipes.
What is seamless pipe?
Seamless pipe is made by heating a solid steel billet, piercing it to form a hollow shell and rolling it to the final diameter and wall thickness. There is no welded joint anywhere in the pipe.
Without a seam, the pipe has uniform strength around its circumference, which is why engineers specify seamless pipe for high pressure, high temperature and critical service such as oil and gas, steam and process lines. Hotline Steel Trading supplies seamless pipe from ¼″ to 16″ in schedules SCH 40, SCH 80, XS and STD, to API 5L, ASTM and DIN or JIS standards. It is supplied in single or double random lengths with a lacquer exterior coating, plastic end caps and a Mill Test Certificate complying with API 5L.
ERW vs seamless pipe comparison
The choice between ERW and seamless pipe comes down to pressure, temperature, size and budget. The table compares the two using the ranges Hotline Steel Trading supplies.
| Point | ERW pipe | Seamless pipe |
|---|---|---|
| How it is made | Steel strip formed and resistance welded | Solid billet pierced and rolled |
| Weld seam | One longitudinal weld | None |
| Size range supplied | ½″ to 24″ OD | ¼″ to 16″ |
| Wall or schedule | 1.6 mm to 14.2 mm | SCH 40, 80, XS, STD |
| Standards | API 5L, ASTM A53, DIN, BS, API 5CT | API 5L, ASTM, DIN, JIS |
| Lengths | 6 m and 12 m fixed, SRL, DRL | SRL or DRL |
| Typical use | Construction, water, structural, general piping | High pressure, high temperature, critical lines |
| Relative cost | Lower | Higher |
ERW pipe ½″ to 24″ and seamless pipe ¼″ to 16″, supplied from Dubai.
Which pipe to choose for your application
Seamless pipe is the right choice when the line carries high pressure or high temperature, or when the project specification calls for it. ERW pipe is the practical choice for most other lines, especially where large diameters or long fixed lengths keep installation costs down.
- Oil and gas, steam, hydraulic and process lines: seamless pipe, usually to API 5L or ASTM.
- Water mains, cooling water and general building services: ERW pipe, often joined with grooved pipe fittings on larger sizes.
- Structural uses, piling, fencing and supports: ERW pipe.
- Large diameter lines above 16″: ERW pipe, as seamless is supplied up to 16″.
Whichever pipe you choose, the fittings and flanges need to match its schedule and standard. Pipe is normally ordered with MS butt weld fittings such as elbows, tees and concentric reducers, plus matching pipe flanges.
Where GI pipe fits in
GI pipe is steel pipe coated with zinc by hot-dip galvanizing, which gives it corrosion resistance in wet and outdoor conditions. It is a third option for water supply, plumbing and exposed pipework where uncoated black steel would rust.
The zinc layer corrodes in place of the steel underneath, which extends the service life of the pipe compared with uncoated pipe. Hotline Steel Trading supplies GI pipe from ½″ to 8″, usually joined with threaded GI fittings rather than welding, because welding burns off the zinc at the joint.
What to include in a pipe enquiry
A complete pipe enquiry states the type, standard, size, wall thickness and length, so the supplier can quote without follow-up questions.
- Pipe type: ERW, seamless or GI.
- Standard and grade, for example API 5L or ASTM A53, with Type E or Type S where relevant.
- Nominal size or outside diameter.
- Schedule or wall thickness.
- Length: 6 m, 12 m, single random or double random.
- Quantity in metres or lengths, and any certificate requirements.
Frequently asked questions
Is seamless pipe stronger than ERW pipe?
Seamless pipe has no weld seam, so its strength is uniform around the circumference, which is why it is preferred for high pressure and high temperature service. Modern ERW pipe made to a recognised standard is suitable for a wide range of pressure and structural applications.
Does ASTM A53 cover both ERW and seamless pipe?
Yes. ASTM A53 covers seamless pipe (Type S) and electric resistance welded pipe (Type E), so the type should always be stated on the order alongside the grade.
Does Hotline Steel Trading supply mill test certificates?
Seamless pipe from Hotline Steel Trading is supplied with a Mill Test Certificate complying with API 5L. For ERW pipe, ask for the documents your project needs when you request a quote.
Request a quote for steel pipe
Send the pipe type, standard, sizes and quantities and Hotline Steel Trading will reply with price and availability.
