Designing Tube and Pipe Wall Thickness for Heat Exchangers

Selecting the wall thickness of pipes and tubes is a central engineering decision that affects safety, service life, pressure resistance, weight, operating costs, and manufacturability. In process industries—such as chemicals, pharmaceuticals, food and beverage, energy, fertilizers, and thermal systems—choosing the correct wall thickness is essential for the proper design of heat exchangers, piping systems, pressure vessels, structural components, and related equipment.

This guide summarizes, in a structured and clear manner, the key principles, considerations, and relevant standards for selecting a pipe or tube according to the required wall thickness.

1. What Is Wall Thickness and What Does It Mean?

Wall thickness is the distance between the outer and inner diameter of a pipe. It is a critical parameter that determines:

• Resistance to internal or external pressure

• Mechanical durability against loads, vibration, and cyclic stresses

• Long-term corrosion resistance

• Heat-transfer efficiency (especially in heat exchangers)

• Overall system weight

• Material and manufacturing cost

When designing tubes for heat exchangers, wall thickness must also take into account flow-induced vibration, erosion potential, and localized stresses caused by thermal expansion.

2. Standards Governing Wall Thickness Selection

Engineers typically rely on international standards that define strength requirements precisely:

• ASME Section VIII Div. 1 – Design of pressure vessels

• ASME B31.3 – Design of industrial process piping

• EN 13480 / EN 13445 – European standards for piping and pressure vessels

• TEMA – Standards for shell-and-tube heat exchangers

• API 660 / API 661 – Heat exchangers in the oil and gas industry

These standards specify formulas for calculating the minimum allowable wall thickness while considering design pressure, temperature, welds, stresses, and safety margins.

3. Calculating Wall Thickness According to Pressure

The main design parameter is the maximum design pressure.

The basic calculation includes:

• Design pressure (P)

• Outer or inner diameter (Do / Di)

• Allowable stress (S) according to material and temperature

• Weld efficiency (E), if welding seams exist

• Corrosion allowance (C)

Example ASME formula:

t=P⋅D2(SE+P)+Ct = \frac{P \cdot D}{2(SE + P)} + Ct=2(SE+P)P⋅D​+C

This yields the minimum permissible thickness.
In practice, an additional safety margin is added based on flow conditions, erosion, thermal expansion, and vibration.

4. Influence of Material Type on Wall Thickness Selection

Each material has different strength properties that influence the required wall thickness:

Carbon Steel

• Good strength for low to medium pressures

• Moderate corrosion resistance

• Low cost

• Typically requires a higher corrosion allowance

Stainless Steel (SS304 / SS316)

• Good high-temperature strength

• Excellent corrosion resistance

• Allows the use of thinner walls compared with carbon steel

Hastelloy / Titanium

• Exceptional corrosion resistance

• Suitable for very thin walls (0.5–1.2 mm) in heat-exchanger tubes

• High cost—making excessive thickness economically inefficient

Duplex / Super Duplex

• Very high mechanical strength

• Allows reduced wall thickness

• Suitable for high-pressure + corrosive environments

5. Selecting Wall Thickness in Heat Exchangers (Tubes)

Heat-exchanger tubes require unique considerations:

• TEMA requirements: usually 0.7–2.0 mm

• Flow-induced vibration: thin tubes may wear or crack

• Type of fluid: corrosive, viscous, or high-temperature

• Flow velocity: higher velocity → increased erosion

• Baffle spacing: affects tube stability

• Tube-sheet expansion: tubes that are too thin may tear during expansion

Practical ranges:

• Stainless steel → 0.9–1.65 mm

• Hastelloy → 0.7–1.25 mm

• Carbon steel → 1.2–2.0 mm

• Titanium → 0.5–0.9 mm

6. Selecting Wall Thickness in Industrial Piping

In piping systems, wall thickness selection depends on:

Pressure and Operating Conditions

Higher pressure → thicker wall.

Temperature

At high temperatures, material strength decreases → requires a thicker wall.

Internal or External Corrosion

Typical corrosion allowance values:

• 1–3 mm for carbon steel

• Almost zero for stainless steel

Welds

Welded pipes require weld efficiency E < 1, which increases calculated wall thickness.

Mechanical Requirements

• Resistance to mechanical impact

• Dynamic loads

• Vibration from rotating equipment

7. Example Table of Typical Wall Thicknesses (General Only)

This table is not a design recommendation, but a technical reference of commonly available standard wall thicknesses:

8. Common Mistakes in Wall Thickness Selection

• Selecting based on habit or past experience instead of standard-based calculation

• Oversizing the wall thickness → excessive cost and unnecessary weight

• Undersizing the wall → dangerous, especially in heat exchangers

• Ignoring corrosion allowance → premature failure

• Using a material with insufficient strength for the required loads

• Importing manufacturer data that is unsuitable for real site conditions

9. How to Select Wall Thickness Correctly — A Structured Method

Step 1 – Collect All Required Design Data

• Design pressure

• Design temperature

• Fluid properties

• Pipe diameter

• Applicable standard

• Vibration, erosion, thermal expansion

Step 2 – Select Material

Based on corrosion, cleanliness, budget, and weight considerations.

Step 3 – Calculate Wall Thickness per the Appropriate Standard

Step 4 – Adjust for Special Stresses

• Vibration

• Erosion

• Connection stresses

Step 5 – Verify Manufacturability

Very thin titanium tubes, for example, may tear during tube expansion.

Step 6 – Check Market Availability

Only certain thicknesses exist in practice:

• 0.5 / 0.7 / 0.9 / 1.2 / 1.65 mm

• Schedule 10 / 40 / 80 (piping)

• DIN / EN commercial tube sizes

10. Summary

Selecting the correct wall thickness for pipes and tubes is an engineering process that balances strength, pressure, temperature, corrosion resistance, thermal performance, cost, and manufacturability. Using calculations based on recognized standards—combined with practical engineering judgment—helps achieve a safe, economical, and long-lasting solution.

For complex applications or extreme operating conditions, it is essential to perform full code-based calculations and consult an experienced mechanical engineer.