Stainless steel is widely used throughout engineering, manufacturing and fabrication because of its strength, durability and excellent resistance to corrosion. However, when specifying hollow stainless steel products, one question regularly causes confusion: should you be using stainless steel tube or stainless steel pipe?
At first glance, the two products can appear almost identical. Both are hollow sections available in different diameters, wall thicknesses and stainless steel grades. However, the way they are measured, specified and used can be very different.
Choosing incorrectly can cause problems with dimensions, fabrication, compatibility and overall performance. Understanding these differences is therefore important when specifying materials for engineering, automotive, architectural, marine and industrial projects.
This guide looks at how stainless steel tube and pipe differ and, more importantly, how to determine which option is appropriate for your application.
Stainless Steel Tube and Pipe Are Designed Differently
The easiest way to understand the distinction is to consider what each product is primarily designed to do.
Stainless steel pipe is generally associated with transporting liquids and gases. Consequently, factors such as internal capacity, pressure rating and flow characteristics are particularly important.
Stainless steel tube has a much broader range of mechanical and structural applications. It is commonly selected where the exact outside dimensions, wall thickness, appearance or fabrication characteristics are important.
This is why stainless steel tubing can be found in everything from automotive exhaust systems and machinery to architectural structures, handrails and marine equipment.
UKF Group supplies a wide range of specialist tubing, including stainless steel welded tube for general purpose applications alongside products developed for more specialised environments.
Understanding the Difference in Sizing
One of the most important distinctions between stainless steel tube and pipe is how the products are sized.
How Stainless Steel Pipe Is Sized
Pipe is traditionally specified according to a nominal pipe size and a schedule.
The nominal measurement does not necessarily represent the precise outside or inside diameter of the finished product. Instead, the sizing system has developed around the requirements of pipework systems.
The schedule relates to wall thickness. Two pipes with the same nominal size can therefore have different wall thicknesses and internal diameters.
For applications involving the movement of liquids or gases, this makes sense because flow capacity and pressure requirements are often more important than having a particular external measurement.
How Stainless Steel Tube Is Sized
Tube is normally specified using its actual outside diameter and wall thickness.
For example, an engineer may specify tubing with a particular outside diameter and a defined wall thickness because it needs to fit precisely into another component.
This dimensional accuracy is particularly valuable for fabrication.
Components may need to be:
- Welded together
- Bent or manipulated
- Cut to precise lengths
- Inserted into assemblies
- Connected to other sections
- Positioned within restricted spaces
Knowing the exact dimensions of the tube makes planning and manufacturing these components considerably easier.
Where Is Stainless Steel Tube Used?
Stainless steel tubing is extremely versatile and can be manufactured for a wide variety of industries.
General purpose tubing is commonly used for engineering structures, frames, machinery and fabricated components where corrosion resistance and dependable mechanical performance are required.
Automotive manufacturing is another major application. Stainless steel exhaust tube is designed for exhaust fabrication, where the material needs to cope with heat, moisture, vibration and corrosive exhaust gases.
Specialist applications can require different types of tubing.
For example, stainless steel marine tube is suitable for applications where exposure to moisture and demanding environments makes corrosion resistance particularly important.
Similarly, stainless steel hygienic tube is intended for applications where cleanliness and surface quality are key considerations.
The important point is that there is no single type of stainless steel tubing suitable for every application. The intended environment should always influence the specification.
Where Is Stainless Steel Pipe Used?
Stainless steel pipe is typically chosen for systems designed to carry liquids, gases or other materials.
Typical applications can include industrial processing, water systems, chemical plants, energy infrastructure and other fluid transfer systems.
In these environments, engineers are generally more interested in characteristics such as pressure capacity, flow rate, temperature resistance and compatibility with valves, fittings and other pipework components.
This highlights an important difference in the selection process.
When selecting pipe, the system’s operating requirements often determine the specification. When selecting tube, dimensional accuracy, fabrication requirements, mechanical properties and appearance can have greater influence.
Choosing the Correct Stainless Steel Grade
Whether you are specifying tube or pipe, selecting the appropriate stainless steel grade is another important consideration.
Different stainless steel grades provide different levels of corrosion resistance, mechanical performance and suitability for challenging environments.
For many general engineering applications, common stainless steel grades provide an excellent combination of durability, strength and corrosion resistance. More demanding environments, however, may require a grade capable of handling increased exposure to moisture, chemicals or salts.
Marine environments are a good example. Components installed near seawater can experience much more aggressive corrosion conditions than products used inside a dry manufacturing facility.
Rather than choosing stainless steel purely because it is corrosion resistant, engineers should consider the specific environment in which the finished component will operate.
For a more detailed explanation, read UKF Group’s guide on how to choose the right stainless steel grade for your project.
Wall Thickness Matters Too
Diameter is only part of the specification. Wall thickness can have a major influence on the strength, weight and fabrication characteristics of stainless steel tubing.
A thicker wall can provide additional strength and durability but will also increase weight and material usage.
A thinner wall may be preferable where reducing weight is important, provided the tube still offers sufficient mechanical performance for the application.
The correct choice therefore depends on factors including loading, vibration, bending requirements and the conditions in which the component will operate.
This is particularly important within automotive and performance applications, where engineers may be looking for an effective balance between strength and weight.
Consider How the Material Will Be Fabricated
The final component should always be considered when choosing stainless steel products.
A length of tubing may need to undergo several processes before becoming part of the finished assembly.
UKF Group offers a range of stainless steel fabrication and value added services that can help prepare tubing for specific manufacturing requirements.
Depending on the project, this can include cutting, bending, perforating, polishing, welding and other manufacturing processes.
If tubing needs to be bent, for example, the outside diameter, wall thickness and grade can all influence how the material behaves during manipulation.
Similarly, products intended for visible architectural applications may require a particular surface finish, while internal engineering components may prioritise mechanical performance instead.
Thinking about these requirements at the specification stage can reduce unnecessary processing and help make production more efficient.
Round Tube Is Not the Only Option
When discussing stainless steel tubing, it is easy to assume that all tube is circular. However, structural and fabrication projects can also benefit from other profiles.
Stainless steel square box section is commonly used for frames, supports, structures and fabricated assemblies where a square profile makes construction easier.
Stainless steel rectangular box section provides another option for structural applications where the dimensions or loading requirements favour a rectangular profile.
These products demonstrate why it is often better to think in terms of the finished component rather than simply deciding between “tube” and “pipe”.
Welded or Seamless Tube?
Another consideration when specifying tubing is whether the application requires welded or seamless material.
Welded stainless steel tube is manufactured by forming stainless steel strip and welding the seam. Modern manufacturing methods allow welded tubing to provide excellent dimensional consistency and performance across a wide range of applications.
Seamless tubing is manufactured without a longitudinal welded seam and can be required for certain specialist applications.
The correct option depends on the operating conditions, required standards, cost and manufacturing requirements.
UKF Group provides further guidance in its article explaining the difference between seamless and welded stainless steel tube.
How Do You Decide Between Stainless Steel Tube and Pipe?
Rather than selecting a product based purely on terminology, start with the requirements of the finished application.
Consider:
- Is the product primarily transporting liquid or gas?
- Is pressure containment an important requirement?
- Does the outside diameter need to be precise?
- Will the material form part of a mechanical or structural assembly?
- Will it need bending, cutting or welding?
- What level of corrosion resistance is required?
- Does the surface finish matter?
- What stainless steel grade is appropriate?
- Is weight an important consideration?
- Does the application require a specialist tube?
If fluid transportation and pressure are the primary considerations, pipe may be appropriate.
If dimensional accuracy, structural performance, fabrication or appearance are more important, stainless steel tube is often the better choice.
Finding the Right Stainless Steel Product
Although stainless steel tube and pipe can look very similar, they are specified with different priorities in mind. Pipe is generally centred around flow and pressure requirements, while tube provides the dimensional control and versatility required by a wide range of engineering and fabrication applications.
The right choice also goes beyond simply deciding between tube and pipe. Diameter, wall thickness, stainless steel grade, surface finish, manufacturing method and the intended environment all need to be considered.
UKF Group supplies an extensive range of stainless steel tubing and associated products for automotive, engineering, marine, architectural and industrial applications, supported by specialist manufacturing and fabrication capabilities.
By considering how the material will ultimately be used and processed, engineers and fabricators can specify stainless steel products that provide the right combination of strength, corrosion resistance, accuracy and long-term performance.