Seamless Pipe Wall Thickness Selection: Thin-Walled vs. Thick-Walled

Seamless Pipe Wall Thickness Selection: Thin Wall vs. Thick Wall

The selection of wall thickness for seamless steel pipes is a critical design decision, directly impacting safety, economy, process feasibility, and final performance. Thin-walled and thick-walled steel pipes are not absolute concepts, but are usually classified relatively by the ratio of outer diameter to wall thickness. Multi-objective optimization is required during selection.

Core Concepts and Definitions:

Thin-walled steel pipes: Typically refer to steel pipes with an outer diameter/wall thickness ≥ 20. They are characterized by lightweight, material savings, and good flexibility, but are sensitive to defects and have limited pressure-bearing capacity.

Thick-walled steel pipes: Typically refer to steel pipes with an outer diameter/wall thickness < 20. They are characterized by high strength, high rigidity, and strong pressure-bearing capacity, but are heavier, more expensive, and more difficult to process.

Five Major Factors Affecting Seamless Pipe Wall Thickness Selection:

1. Mechanical Properties and Safety

Scenarios where thin-walled pipes are preferred:
Bearing low to medium internal or external pressure.
Primarily bearing tensile or small bending moment loads.
Weight-sensitive moving parts.

Scenarios where thick-walled tubes are preferred:
To withstand high and ultra-high pressure (e.g., hydraulic systems, boilers).
To withstand complex stresses such as large bending moments, torsion, and compression.
For applications requiring fatigue resistance, impact resistance, or wear resistance.
For applications with extremely high safety requirements.

2. Process and Manufacturing

Scenarios where thin-walled tubes are preferred:
Requires secondary forming processes such as cold bending and rolling.
Requires high surface finish on the inner surface (easy polishing and honing).
Connection methods are mainly welding and flanges, with low requirements for beveling.

Scenarios where thick-walled tubes are preferred:
Requires thread machining (to ensure thread strength).
As mechanical structural components, they need to withstand assembly stresses (e.g., interference fits).
As cylinder barrels and bushings, they require sufficient guiding length and wear-resistant layers.

3. Economic Efficiency

Scenarios where thin-walled tubes are preferred:
To achieve the lowest material cost.
For media such as ordinary water and air, without stringent corrosion requirements.
For one-time or short-term projects.

Scenarios where thick-walled pipes are preferred:
For handling expensive and hazardous media, where leakage costs far exceed the pipe's own structural integrity.
For applications requiring long service life and low maintenance costs (thick walls offer greater resistance to corrosion and wear).
For applications with high installation costs (e.g., deep sea, high altitude) where extremely high reliability is required.

4. Fluid Properties

Scenarios where thin-walled pipes are preferred:
For transporting ordinary liquids and gases where pressure drop is not a critical factor.
For applications requiring high flow rates and large flow volumes (larger inner diameter for the same outer diameter).

Scenarios where thick-walled pipes are preferred:
For transporting high-pressure, high-temperature, toxic, flammable, and explosive media.
For applications with transient loads such as water hammer and pressure pulsations.
For corrosive media requiring a "corrosion margin".

5. Standards and Specifications

Scenarios where thin-walled pipes are preferred:
For applications conforming to ASME B36.10M, EN 10216, etc., Schedule 5S, 10S, or similar series.
For low-pressure instrumentation pipes and general heat transfer pipes.

Scenarios where thick-walled pipes are preferred:
Following ASME B36.10M Schedule 80, 160, XXS or API 5L high-strength thick-walled series.
Used in pressure vessels, boilers, and high-pressure process piping, where regulations mandate it.

The selection of wall thickness for seamless steel pipes is a systems engineering decision that seeks the optimal balance between strength, weight, cost, process considerations, and safety. For critical applications, detailed calculations and reviews by qualified engineers are essential.

Read more: Schedule 40 Seamless Steel Pipe or ERW Pipe Thickness Chart