A: In short, yes—seamless pipe has a better pressure capacity and its overall strength is stronger than ERW.
When you’re sourcing steel pipe for your project you need to determine what kind of steel pipe you need. Whether it’s being used on an oil rig, in a nuclear power plant, or a desalination plant—there’s a different pipe appropriate for each.
You have seamless pipe, forged pipe, and welded pipe. Each one offers specific advantages and depending on the application and environmental conditions. There are many factors to consider when choosing the right pipe for your project.
We understand that engineers will already know what pipe to use, but we still want to do due diligence. Let’s cover the properties and usage of seamless pipe, welded pipe, and forged pipe to determine which scenario they work best in.
First, let’s get familiar with these various forms of steel pipe and what each is best suited for.
Seamless pipe is, as the name implies, a pipe with no seams or welds. It’s one continuous piece that is smooth and strong. As with other steel pipe options, it’s available in different diameters depending on your needs.
How It’s Manufactured & Used
Seamless pipe is made via several manufacturing methods that are dependent on the diameter needed or the diameter to wall thickness ratio required. Generally, the process begins with raw steel being cast into a hot solid billet form. This shape is more conducive to working the pipe into the dimensions and thickness needed.
It’s then stretched out and either pulled or pushed over a form and is moved to an extrusion process. In extrusion, the steel is forced through a die and mandrel system. This increases the internal diameter while reducing the external diameter—creating the pipe.
The most common applications for seamless steel pipe include the transfer of fluids and gases. Substances such as natural gas, water, air, and waste regularly flow through seamless steel pipe. Additionally, it’s used in environments with high-corrosive levels and high-pressure industries like petroleum, power plants, and pharmaceuticals.
Seamless steel pipe is used in these fields due to its specific advantages over other forms of steel pipe.
- Strength— Seamless pipe not having a seam means one less vulnerability. Typically, it can handle up to 20% more constant pressure than welded pipe. This is crucial in high-risk environments such as oil & gas facilities where pressure is consistently high.
- Resistance— Not having a seam also translates to a higher resistance to corrosive materials. With a seam, a lot of impurities and corrosives can get caught up on that seam and begins to corrode the pipe.
- Test Less Work More— This is a pretty obvious advantage, but since there’s no seam there’s no weld integrity test needed. This means more uptime since you don’t have to run a test.
Welded pipe comes in three forms: outside diameter weld, inside diameter weld, and dual-sided welds. The thing they all have in common is that they have a seam of some kind.
How It’s Manufactured & Used
To make welded pipe, manufacturers start with a steel coil. They roll it out to the needed thickness, into a plate or flat strip. Then it’s rolled into the shape of a pipe where the seam is welded securely.
Now, not just any steel is ideal for welding. For example, austenitic steel is the most conducive to welding, generally speaking. Ferritic steel is only weldable in thin sections and duplex steels are also as weldable as austenitic but require more care.
The manufacturing of welded pipe has greatly advanced in the last decade with the most significant being electric resistance welding. ERW, as it’s also abbreviated has significantly improved the corrosion resistance and seam integrity of welded pipe.
While it is true that welded pipe, in theory, is weaker when it is welded. Many advances in the welding process and quality checks have closed the gap. However, technically speaking, seamless pipe is still stronger on paper and in extreme applications.
- Cost— Since the manufacturing process requires less complex methods, welded pipe is the least expensive option of all pipes. It’s also faster to manufacture so it’s usually easier to get ahold of some.
- Consistency— Again, due to the manufacturing process, wall thickness on welded pipe tends to be more uniform and consistent than seamless pipe. Since the process starts with a flat strip or plate of steel, it makes controlling thickness easier.
- Surface quality— Since it’s not made using the extrusion process, welded pipe’s surface is usually far smoother than seamless pipe.
- Speed— Since the manufacturing process is less complex and much faster than seamless pipe, the lead time for procurement is less too.
Forging steel is pretty much what it sounds like. It’s a forging process that shapes the metal using compression, pressure, and extreme heat to create the pipe you need.
How It’s Manufactured & Used
Manufacturing starts with a solid piece of steel, it could be Duplex or Super Duplex, Stainless Steel, 6% moly, or Nickel Alloy. The steel is placed in between a lower die and an upper die. Heat and applied pressure form the steel into the desired dimensions. After this, it gets machined according to the specifications that are requested.
Because the process is more complex, it does result in forged pipe costing more than seamless pipe or welded pipe.
However, that higher cost comes with quite a few advantages across many different applications and a wide array of industries. Sectors such as hydraulic machinery, petroleum, chemical, and agricultural fertilizer benefit from forged steel pipe.
Like seamless pipe, there are no seam or weld points, so it is capable of fully containing corrosives or harmful substances and fumes. This allows it to be used in many industries that deal with hazardous materials.
- Strength— The manufacturing process of forged pipe results in a product that is exceedingly strong and reliable. This is because forging causes the flows of the grains of the steel to align and alter. To put it simply, the steel is refined further and the strength is boosted.
- Longevity— Forging removes the potential for porosity, cavities in the surface, and shrinkage. This results in a pipe that has a long life span and will continue to perform as well as when first manufactured.
- Efficient— In terms of making good use of raw materials, forging is quite efficient and economical as no materials are wasted.
- Flexibility— Forging is a very flexible process and can produce products of various shapes and sizes with ease.
Seamless Pipe, Welded Pipe, or Forged Pipe—TPC Has You Covered
Whatever steel pipe you need whether it’s all seamless, or a complex project with a variety of pipe—we have what you need. Our expansive warehouse keeps a large amount of inventory ready to ship to you fast.
Contact us today and see how we can get you the PVF products you need—FAST!