How to Choose the Wall Thickness of an Extruded Acrylic Tube (PMMA) for Pressure? A Practical Guide

Selecting the correct extruded acrylic tube (PMMA, EXTRUDED) for a pressure installation is a critical step that ensures safety, durability and cost optimisation for the project. In this article we explain in straightforward terms how to select the wall thickness of an extruded acrylic tube so that it meets the technical requirements and is safe for long-term use.

What Is an Extruded Acrylic Tube?

An extruded acrylic tube is produced by the process of extrusion – heated PMMA granulate is forced through a forming die. Unlike cast tubes (CAST), extruded tubes are characterised by:

higher dimensional accuracy,
lower price per linear metre,
excellent optical clarity and aesthetics,
lower chemical resistance compared with CAST tubes.

This makes them well suited to low-pressure, display and lighting applications as well as light technical structures.

Why Is Selecting the Wall Thickness of an Acrylic Tube So Important?

A wall that is too thin on a PMMA tube can lead to:

material deformation under load,
cracking under pressure,
shortened service life of the installation.

Conversely, a tube that is too thick means unnecessarily higher costs and larger structural dimensions. Finding the optimal balance between safety and economy is therefore essential.

What Determines the Strength of an Extruded Acrylic Tube?

The pressure resistance of a PMMA tube depends on several parameters:

the inner diameter (D'),
the outer diameter (D⁰),
the wall thickness (S),
the operating pressure (P₁),
the operating temperature and environmental conditions.

Formula for the Permissible Pressure of an Extruded Acrylic Tube

P₁ = (50 · S) / D'

Condition of applicability: D⁰ / D' ≤ 1.2

Symbols

P₁ – internal pressure [bar]
S – wall thickness [mm]
D' – inner diameter [mm]
D⁰ – outer diameter [mm]

Step-by-Step: Selecting the Wall Thickness of an Extruded Acrylic Tube

To calculate the minimum wall thickness, rearrange the formula:

S = (P₁ · D') / 50

Determine the maximum operating pressure of the installation (bar).
Select the appropriate tube diameter – both inner and outer.
Calculate the minimum wall thickness in accordance with the formula.
Check the design condition D⁰ / D' ≤ 1.2.
Add a safety margin based on operating conditions and tolerances.

Calculation Example – Extruded Acrylic Tube at 4 bar Pressure

Assumptions:

Operating pressure: 4 bar
Inner diameter: 80 mm

Calculation: S = (4 · 80) / 50 = 6.4 mm

Practical recommendation: In engineering practice, a tube with a wall thickness of at least 7–8 mm should be used. This margin accounts for production tolerances, installation micro-damage and the reduction in strength at elevated temperatures.

Production Tolerances for Extruded Acrylic Tubes

Parameter	Tolerance
Outer diameter	±1% to ±2%
Inner diameter	±1.5% to ±2.5%
Wall thickness	±5% to ±15%

This means that the actual wall thickness may be smaller than the nominal value – which is why an appropriate safety margin must always be included, particularly in pressure applications.

Best Design Practices for Extruded Acrylic Tubes

Apply a safety factor of at least 1.5–2.
Do not design the installation "to the limit" – always leave a reserve.
Account for the operating temperature – calculated values refer to 20 °C.
Check environmental conditions – UV radiation, chemical agents, vibration.
Pay attention to the installation method – incorrect installation stresses significantly reduce the strength of a PMMA tube.

Extruded Acrylic Tube vs. Cast Acrylic Tube – Which to Choose?

Extruded tube (EXTRUDED) – recommended for low-pressure, display applications and wherever dimensional accuracy and an attractive price are the priorities.
Cast tube (CAST) – chosen for applications with higher mechanical, chemical and pressure requirements.

If in doubt, it is always worth consulting an Erson technical advisor – we will help match the type and wall thickness of the tube to your application.

FAQ – Frequently Asked Questions about Extruded Acrylic Tubes

Are extruded acrylic tubes suitable for pressure installations?

Yes, provided the wall thickness is selected correctly and the operating conditions are taken into account. For applications with elevated requirements, cast tubes (CAST) may be a better choice.

Can one formula be used for all plastic tubes?

No. Each material has its own strength – a different formula is used for acrylic tubes (divisor 50) and for polycarbonate tubes (divisor 100). In addition, the type of tube (extruded or cast) and the production tolerances must be taken into account.

How can I increase the safety of an installation with an acrylic tube?

By using a greater wall thickness, applying a safety factor of 1.5–2 and carrying out regular inspection of the tube during service.

What is the maximum operating temperature of an extruded acrylic tube?

In typical applications, PMMA operates stably up to approximately 60–70 °C. Above this temperature, mechanical strength drops rapidly.

Are extruded acrylic tubes resistant to UV radiation?

Yes. PMMA is one of the most UV-resistant plastics, which means that acrylic tubes also perform well in outdoor applications.

Summary

Selecting the wall thickness of an extruded acrylic tube is a critical stage in designing a safe installation. By applying the simple formula S = (P₁ · D') / 50, accounting for production tolerances and an appropriate safety factor, you can ensure safe and durable system operation for many years.

Looking for help selecting extruded acrylic tubes? Contact Erson – we will advise you on the best solution for your application and propose a tube that is optimal in terms of both price and technical performance.