7 Differences Stainless Steel Pipe Vs Stainless Steel Tube

When discussing stainless steel tubular products, we often hear the terms “tube” and “pipe.” While the terms are often used interchangeably, there are clear and crucial differences between them. This article will delve into the differences between tube and stainless steel pipe from multiple perspectives and guide you on how to make the best choice.

Stainless Steel Tubes Vs. Stainless Steel Pipes

Main Applications

Stainless Steel Pipes:

Core Function: Transporting media.

Typical Applications: Oil and gas pipelines, municipal water supply systems, chemical process piping, fire sprinkler systems, refrigerant transport in HVAC systems, and fluid conveying lines in food and beverage plants.

Stainless Steel Tubes:

Core Function: Structural support, heat transfer, and precision machining.

Typical Applications: Guardrails and roof supports for building structures, medical devices (such as needles and endoscope components), automotive exhaust pipes, heat exchanger tubes, boiler tubes, bicycle and motorcycle frames, and furniture manufacturing.

Dimensions And Definitions

Stainless steel pipes are sized by their nominal pipe size (NPS), a dimensionless, standardized measurement that represents the pipe’s capacity rather than its exact physical dimensions. For example, an NPS 2 pipe has a fixed outside diameter (e.g., 60.3 mm), but its wall thickness varies according to the schedule. Pipe dimensions are typically expressed as: NPS × Schedule (e.g., NPS 2 Schedule 40).

Stainless steel tubes are sized by their precise outside diameter (OD) and/or inside diameter (ID), as well as their wall thickness, typically in millimeters or inches. This reflects the stringent requirements for dimensional accuracy. Specifications are typically expressed as: OD × Wall Thickness (e.g., 25.4 mm × 1.2 mm).

Tolerance Requirements

Stainless steel pipes: Tolerance requirements are relatively loose, focusing more on pressure-bearing performance and flow capacity rather than precise geometric dimensions. Wall thickness and ovality tolerances are wide.

Stainless steel pipes: Tolerance requirements are extremely stringent. Whether it’s outer diameter, wall thickness, ovality, or straightness, they must all be controlled within very tight tolerances. This is crucial for assembly, interchangeability, and structural stability.

Mechanical Properties

Stainless steel pipes: Performance evaluation focuses on compressive strength, pressure rating, and toughness to ensure they can safely transport media under pressure without rupture.

Stainless steel pipes: Performance evaluation focuses on mechanical strength, hardness, and flexural strength to ensure they can withstand loads as structural components. Pipes are typically subjected to tests such as tensile testing, flattening, and flaring.

Surface Finish

Stainless steel pipes: Surface finish requirements are generally low, unless used in sanitary or high-purity applications (such as the food and pharmaceutical industries), polishing is required.

Stainless steel pipes: Surface finish requirements are generally higher, especially in applications such as medical devices, furniture, and architectural exteriors. Common surface treatments include bright annealing (BA), mechanical polishing (e.g., 180 Grit, 400 Grit), and electrochemical polishing.

Forming And Joining Methods

Stainless steel pipes: Connections are primarily made by welding (butt welding, socket welding) and threading. Connection methods are designed to ensure the system’s tightness and robustness.

Stainless steel tubing (Tubes): Connection methods are more diverse, including precision welding, brazing, flaring, crimping, and the use of clamps or flanges. In structural applications, direct bolting or welding is also common.

Shape And Material

Shape:

Pipes: Almost always round to evenly distribute internal pressure.

Tubes: They come in a wide variety of shapes, including round, square, rectangular, and oval, to accommodate various design and structural requirements.

Material: Both can utilize the same stainless steel grades, such as the most common 304/L and 316/L. However, due to differing application priorities, specialized high-performance or functional alloys are more commonly used for pipes.

How To Choose The Right Tube Or Stainless Steel Pipe?

To select the appropriate type, follow these steps:

Identify the application purpose:

Transporting fluids/gases? -> Prioritize pipes.

Structural support, mechanical components, heat transfer? -> Prioritize tubes.

Determine key parameters:

For pipes: Determine the required NPS size and Schedule (e.g., Schedule 40, Schedule 80) based on the pressure, temperature, and corrosiveness of the transported media.

For tubing: Determine the precise outer diameter, inner diameter, wall thickness, and shape (round/square/rectangular) based on the design drawings and assembly requirements.

Evaluate performance requirements:

Strength and pressure: Pipes must meet the pressure rating; tubing must meet structural load requirements.

Corrosion resistance: Select the appropriate stainless steel grade (e.g., 304, 316, 316L) based on the environment (e.g., coastal areas, chemical plants).

Precision and appearance: If tight dimensional tolerances and a beautiful appearance are required, tubing is the only choice.

Consider budget and process:

Generally speaking, for equivalent specifications, tubes cost more than pipes due to the more complex manufacturing process and tighter tolerances.

Confirming which connection capabilities your fabrication shop has (welding, threading, crimping) will also influence your final choice.

FAQ

Are Square Or Rectangular Stainless Steel Pipes Tubes Or Pipes?

By definition, they are tubes. “Pipe” specifically refers to products with a circular cross-section used for transportation. Square and rectangular tubes are widely used in construction and mechanical framing due to their superior structural properties (high flexural modulus).

Are Tubes More Expensive Than Pipes?

Generally, yes. This is mainly because steel has higher requirements for raw materials, production processes (such as cold rolling), dimensional tolerances, and surface finish, resulting in its production cost being generally higher than pipes.

Can Stainless Steel Pipes Be Used In High-Temperature Applications?

Yes. Stainless steel (particularly grades like 310S and 321) has excellent high-temperature strength and oxidation resistance, making it an ideal choice for high-temperature applications.

What Is The Difference Between Welded And Seamless Stainless Steel Pipes?

Seamless pipe: Formed in a single process from a perforated solid steel billet, without welds. It offers uniform mechanical properties and greater pressure resistance, making it suitable for critical applications involving high pressure and high stress.

Welded pipe: Made by welding stainless steel sheet/strip after coiling. It offers lower cost, a wide range of sizes, and superior surface quality. For many low- and medium-pressure applications, welded pipe is perfectly adequate. The properties of the weld zone may differ slightly from those of the parent material.

Are Stainless Steel Pipes For Home Renovation Used As Tubes Or Pipes?

It depends on the specific use:

Pipes that carry water or gas are classified as pipes.

Stair railings, door and window frames, and furniture frames are classified as tubes.

Conclusion

Although stainless steel tubes and pipes are both hollow, long products, their design philosophies, applications, and technical specifications differ fundamentally.

Stainless steel pipes are about “flow,” with standards centered around flow and pressure. Pipes, on the other hand, are about “structure” and “precision,” with their value reflected in size, shape, and mechanical properties.