Small-diameter tubes are used in many types of equipment, but the material depends on what the tube needs to carry and how the equipment operates.
A PFA tube is commonly used for chemical and high-purity fluid transfer, while a PU tube is more often used for compressed air, pneumatic control and moving equipment.
For equipment designers, the choice usually comes down to four points: media, temperature, pressure and tube size.
What Are Small-Diameter PFA Tubes Used For?
PFA is mainly selected when the tube needs to handle chemicals, high temperatures or clean fluid transfer.
Chemical Dosing Equipment
In a chemical dosing system, a small PFA tube can connect a dosing pump, valve and process point.
The tube carries a controlled amount of chemical from the pump to the equipment. The required tube size depends on the chemical, flow rate, pressure and temperature.
Typical equipment includes:
- Chemical dosing units
- Laboratory dosing equipment
- Chemical analysis instruments
- Pump and valve assemblies
Laboratory and Analytical Equipment
Small PFA tubes are also used in laboratory equipment for transferring reagents, samples, solvents and other liquids.
The small internal passage allows the tube to fit into compact equipment where standard-size hoses may take up too much space.
For these applications, engineers normally consider:
- Chemical compatibility
- Internal diameter
- Required flow
- Temperature
- Connection size
Semiconductor Fluid Systems
In semiconductor equipment, PFA is used for chemical and high-purity fluid lines.
Small PFA tubes can be used between pumps, valves and process components where the fluid path needs to remain compact.
Common applications include:
- Chemical delivery
- High-purity fluid transfer
- Ultrapure water lines
- Chemical dosing
- Wet-process equipment
The exact tube specification depends on the chemical, temperature, pressure and cleanliness requirements of the system.
Which Industries Rely on Small PU Tubing?
PU is used differently from PFA.
Instead of chemical resistance being the main requirement, PU tubing is commonly selected for flexible air lines and pneumatic equipment.
Pneumatic Control Systems
A small PU tube can connect valves, sensors and pneumatic components inside an automated machine.
For example, a tube can run from a solenoid valve to a pneumatic actuator to supply compressed air for movement.
Typical equipment includes:
- Pneumatic control panels
- Solenoid valve systems
- Pneumatic grippers
- Automation equipment
- Air control circuits
Robot Arms and Moving Equipment
When a tube moves together with a robot arm or another mechanical component, flexibility becomes important.
A PU pneumatic tube can be routed around moving parts and connected to pneumatic tools or grippers.
The tube size needs to match the required airflow and fitting size.
Compact Automation Equipment
Modern automation equipment often contains many pneumatic lines in a small space.
Small-diameter PU tubes can be routed between valves, sensors, grippers and other components without taking up the space required by larger hoses.
This is common in:
- Pick-and-place machines
- Assembly equipment
- Pneumatic grippers
- Small robotic systems
- Automated production equipment
PFA or PU: Which One Should You Use?
The easiest way to start is to look at what the tube carries.
| Application | Tube to Consider | Main Reason |
|---|---|---|
| Chemical transfer | PFA tube | Chemical resistance |
| Laboratory fluid transfer | PFA tube | Chemical compatibility |
| High-purity fluid | PFA tube | Clean fluid path |
| Chemical dosing | PFA tube | Suitable for many chemical media |
| Compressed air | PU tube | Flexibility |
| Pneumatic control | PU tube | Flexible installation |
| Robot pneumatic lines | PU tube | Repeated movement |
| Compact automation | PU tube | Small and flexible routing |
This does not mean that every chemical system requires PFA or every pneumatic system requires PU. The actual material should be selected according to the working medium and operating conditions.
Why Does Small-Bore Tubes ID Matter?
The inner diameter (ID) determines the size of the flow passage inside the tube.
Liquid Flow Resistance: A smaller inner diameter increases fluid drag, restricting volume output and altering downstream flow rates.
Pneumatic Delivery: Inner diameter determines airflow capacity and directly impacts response speed in connected pneumatic components.
Sizing Principle: Outer diameter alone is insufficient for tube selection; inner diameter must be evaluated to ensure proper flow performance.
When ordering a precision tube, it is useful to specify:
- Inner diameter
- Outer diameter
- Wall thickness
- Length
- Working pressure
- Working temperature
- Fluid or gas
What Is the Difference Between a Capillary Tube and a Standard Tube?
A capillary tube generally has a much smaller internal passage than a standard industrial tube.
The term capillary tube is often used for small-diameter tubes used for controlled fluid or gas flow.
Depending on the application, customers may also describe the product as:
- Small-bore tube
- Small-diameter tube
- Fine-bore tube
- Precision tube
- Micro-bore tube
The actual specification is more important than the name. The required ID, OD, wall thickness and material should be confirmed before production.
How Do You Choose the Right Small-Bore Tubes?
Start with the equipment rather than the tube name.
Chemical Compatibility: Verify the tube material against the fluid composition if transporting chemicals.
Pneumatic Parameters: Confirm operating pressure, airflow rate, flexibility, and fitting size for compressed air lines.
Dynamic Motion: Assess bending performance, movement frequency, and minimum bend radius for continuous motion applications.
Spatial Constraints: Measure available installation space and outer diameter requirements within compact equipment.
Precision Flow: Prioritize inner diameter (ID) accuracy and dimensional tolerance for exact fluid delivery systems.
This approach helps avoid selecting a tube only because its material or outside diameter looks suitable.
PFA and PU Small-Bore Tubes from LANGCHI
LANGCHI manufactures PFA tubes, PU tubes and other thermoplastic tubing for fluid transfer, pneumatic systems and industrial automation.
For small-diameter applications, tube specifications can be customized according to:
- Material
- Inner diameter
- Outer diameter
- Wall thickness
- Hardness
- Color
- Length
- Packaging
- Printing
- Customer drawings
The same equipment may require different tube materials for different sections of the system. For example, a machine may use PFA tubing for chemical transfer and PU tubing for pneumatic control.
Providing the application, medium, temperature, pressure and required dimensions allows the tube specification to be determined more accurately.
Quick Selection Guide
Chemical or high-purity fluid → PFA
Compressed air or pneumatic control → PU Small-Bore Tubes
Moving pneumatic equipment → PU
Laboratory chemical transfer → PFA
Compact fluid or air routing → Select according to medium and flow requirement
The right small-diameter tube is determined by the equipment and working conditions, not simply by the tube material or name.
