PTFE tubing size is defined by its inside diameter, outside diameter, and wall thickness. Inside diameter controls the flow passage, outside diameter determines fitting and installation compatibility, and wall thickness influences pressure capability, flexibility, kink resistance, and dimensional stability.
Correct selection requires more than choosing the nearest catalogue size. Fluid properties, pressure, temperature, vacuum, bend radius, tolerance, connection method, and cleaning requirements should be reviewed together. This guide explains how to specify PTFE tubing sizes for industrial fluid handling, laboratory equipment, electrical insulation, and custom assemblies.
PTFE Tubing ID, OD, and Wall Thickness Explained
Three dimensions describe the basic tube geometry:
- Inside diameter (ID) is the diameter of the bore through which fluid, gas, wire, or another component passes.
- Outside diameter (OD) is the overall external diameter and is usually the controlling dimension for compression fittings, clamps, guides, and panel openings.
- Wall thickness is the radial distance between the inside and outside surfaces.
When ID and OD are specified, nominal wall thickness is calculated with the following formula:
Wall thickness = (OD − ID) ÷ 2
For example, a tube with a 6 mm ID and an 8 mm OD has a nominal wall thickness of 1 mm. Production tolerances mean the measured wall may vary within the agreed specification, so the calculation should not be treated as an inspection limit.
Reference PTFE Tube Sizes
The following metric combinations illustrate how ID, OD, and nominal wall relate. These are dimensional examples, not a complete stock list or a pressure guarantee. Availability, tolerances, coil length, and performance data should be confirmed for the required grade and production route.
| Inside Diameter | Outside Diameter | Nominal Wall Thickness | Selection Context |
|---|---|---|---|
| 2 mm | 4 mm | 1 mm | Compact fluid lines, instruments, and small fittings |
| 4 mm | 6 mm | 1 mm | Laboratory equipment and general chemical transfer |
| 6 mm | 8 mm | 1 mm | Moderate flow in metric connection systems |
| 8 mm | 10 mm | 1 mm | Larger flow passage with controlled routing |
| 10 mm | 12 mm | 1 mm | Process lines where pressure drop needs attention |
| 12 mm | 14 mm | 1 mm | Higher-volume transfer with suitable support |
Fractional-inch sizes are also common, particularly in North American equipment. Drawings should state the actual dimensions and units because 1/4 inch equals 6.35 mm, not 6 mm. Treating a fractional size as its nearest metric value can cause fitting leakage or assembly problems.
How to Choose the Inside Diameter
ID selection begins with the required function. Fluid systems need enough bore area to achieve the target flow without excessive velocity or pressure loss. Sleeving applications need clearance for the wire, sensor, cable, or component passing through the tube.
Smaller PTFE tubing ID reduces internal hold-up volume, which can benefit sampling, dosing, and analytical systems. The same reduction increases resistance to flow and makes the line more sensitive to particles, crystallisation, or residue. Larger ID can lower pressure drop but increases contained volume and may require a larger fitting or wider routing space.
Flow calculations should use the minimum permitted ID when performance is critical. Nominal dimensions may not represent the smallest bore allowed by the tolerance.
How to Match the Outside Diameter to Fittings
Tube fittings commonly seal and grip around the OD. Reliable assembly therefore depends on the actual outside diameter, tolerance, ovality, surface condition, wall support, and compatibility with the ferrule or collet design.
Check the fitting supplier’s requirements for:
- Permitted tube material and hardness
- Nominal OD and acceptable tolerance
- Minimum wall thickness
- Required tube insert or support sleeve
- Ferrule material and assembly torque
- Pressure, vacuum, and temperature limits
Soft fluoropolymer tubing may deform when a fitting is overtightened. Excessive compression can narrow the bore, damage the wall, or create a stress concentration. Connection trials under the real pressure and temperature cycle are advisable when leakage would affect safety, purity, or production uptime.
Choosing PTFE Tube Wall Thickness
PTFE tube wall thickness affects pressure resistance, vacuum stability, bend behaviour, permeation, weight, and fitting support. Increasing wall thickness generally improves resistance to internal pressure and external collapse when the material grade, OD, temperature, and other conditions remain comparable.
Thicker walls also reduce flexibility and leave less flow area when OD remains fixed. Thinner walls improve flexibility and reduce material volume but are more vulnerable to kinking, flattening, accidental damage, and vacuum collapse.
| Construction | Potential Advantage | Points to Verify |
|---|---|---|
| Thin-wall PTFE tubing | More flexible, compact, and responsive to heat transfer | Kink resistance, vacuum stability, handling damage, fitting compression |
| Standard-wall PTFE tubing | Balanced flow passage, routing, and mechanical support | Pressure derating, bend radius, fitting compatibility |
| Heavy-wall PTFE tubing | Better resistance to deformation and physical handling | Reduced flexibility, smaller ID for a fixed OD, larger bend radius |
Wall choice should follow the operating envelope rather than a simple “thicker is better” rule. Space, flow, connection geometry, thermal cycling, movement, and service access can make an unnecessarily heavy wall less practical.
PTFE Tubing Pressure Rating
PTFE tubing pressure rating depends on tube dimensions, resin grade, temperature, chemical exposure, manufacturing quality, fittings, pressure cycling, and the selected safety factor. Values published at room temperature cannot be applied unchanged to a heated process.
JIAFUXIN’s current PTFE tube page provides dimensional pressure references at 20°C and clearly identifies them as reference data rather than design guarantees. For example, its listed working-pressure values decrease as tube size increases when nominal wall thickness remains 1 mm. The complete system still needs to be reviewed for temperature, fluid, fittings, installation, and expected life.
Pressure assessment should include:
- Normal operating pressure
- Start-up and shutdown conditions
- Pump pulsation and valve-induced surges
- Blocked-line or fault conditions
- Continuous temperature and short thermal excursions
- Chemical ageing or permeation
- Connection pull-out and sealing performance
System qualification should use the lowest acceptable pressure capability among the tube, fittings, valves, instruments, and other components.
Temperature Changes the Practical Size Requirement
PTFE retains useful properties across a broad temperature range, but it becomes softer and more susceptible to deformation as temperature rises. Higher temperature can reduce working pressure, increase creep at clamped points, and change the support required near fittings.
The PTFE tubing temperature rating should be tied to a specific grade, wall, pressure, exposure time, and application. Continuous service temperature, intermittent cleaning temperature, ambient heat, and fluid temperature should be listed separately in the specification.
Cold service also needs review. Thermal contraction can load fittings, reduce slack, or change routing. Equipment designs should allow predictable movement rather than holding the tube rigidly between fixed connections.
Bend Radius, Kinking, and Installation Space
Flexible PTFE tubing still has a minimum practical bend radius. Sharp bends can flatten the bore, increase pressure drop, concentrate stress, and weaken the line near a fitting. Bend capability changes with OD, wall thickness, temperature, grade, and whether the tube is supported.
Routing plans should provide gradual bends and prevent contact with sharp edges. Clamps should support long horizontal runs without crushing the tube. Moving assemblies need a separate review of repeated flexing, abrasion, torsion, and fatigue because ordinary static tubing is not automatically suitable for continuous dynamic motion.
Tolerances, Ovality, and Concentricity
PTFE tubing dimensions should include measurable tolerances wherever fit, flow, or assembly depends on them. ID and OD values alone do not define allowable ovality, wall variation, or concentricity.
Critical specifications may include:
- ID and OD with separate tolerances
- Minimum wall thickness rather than nominal wall only
- Maximum ovality
- Wall concentricity
- Cut length and squareness
- Surface marks and permissible appearance variation
- Cleanliness and packaging method
- Inspection method and sampling level
Measurement equipment should apply minimal force because soft tubing can deform under calipers or contact gauges. Optical methods, pin gauges, bore gauges, or controlled low-force measurement may be more appropriate for small or tightly toleranced tubing.
PTFE Capillary Tubing and Small-Bore Sizes
PTFE capillary tubing is used when systems need low internal volume, precise fluid delivery, compact routing, or electrical insulation around small components. Bore size, concentricity, cleanliness, and cut quality become increasingly important as dimensions decrease.
Small-bore tubing can create substantial pressure drop and is more easily blocked by particles or dried process residue. Buyers should specify the fluid, required flow, line length, cleaning method, and acceptable internal volume. JIAFUXIN’s PTFE capillary tube page covers the dedicated product option for precision micro-tubing requirements.
Extruded PTFE Tubing vs Machined PTFE Tube
Extruded PTFE tubing is commonly used for continuous lengths and repeatable fluid-transfer or sleeving applications. Machined tube can be produced from molded stock when the part requires a rigid hollow profile, thicker section, stepped geometry, threads, grooves, shoulders, or other drawing-defined features.
Neither route is universally preferable. Extrusion suits continuous profiles and coils, while machining supports complex geometry and lower-volume precision components. Surface finish, tolerance, length, material grade, quantity, and cost target determine the practical process.
PTFE Tubing vs PFA and FEP Tubing
Material selection should consider more than chemical resistance. PTFE, PFA, and FEP differ in clarity, melt processability, weldability, flexibility, temperature capability, and fabrication options.
| Selection Factor | PTFE Tubing | PFA Tubing | FEP Tubing |
|---|---|---|---|
| Appearance | Usually natural white and translucent to opaque | Translucent to relatively clear, depending on grade and wall | Often selected when visual flow inspection is important |
| Processing | Specialised extrusion, molding, sintering, and machining routes | Melt-processable and suitable for extrusion and welding | Melt-processable and suitable for flexible clear tubing |
| Common selection driver | Chemical resistance, low friction, insulation, and broad stock-form availability | High-purity fluid handling and demanding thermal service | Clarity, flexibility, and chemical transfer |
| Size specification | ID, OD, wall, tolerance, and length | ID, OD, wall, tolerance, and connection method | ID, OD, wall, tolerance, bend radius, and fitting |
Review the dedicated PFA tube and FEP tube pages when clarity, weldability, or high-purity processing changes the material decision.
Typical Applications and Their Size Priorities
Different applications place different demands on PTFE tube dimensions:
- Chemical transfer: ID for flow, wall for pressure and permeation, OD for fitting compatibility, and material grade for the fluid and temperature.
- Laboratory and analytical equipment: low hold-up volume, controlled bore, cleanliness, cut quality, and connection repeatability.
- Electrical sleeving: ID clearance, dielectric requirements, wall thickness, routing space, and resistance to installation damage.
- Semiconductor equipment: purity, dimensional control, packaging, traceability, particle requirements, and compatibility with the complete fluid path.
- Machined hollow components: concentricity, rigid dimensions, surface finish, threads, grooves, and drawing tolerances.
Application-specific information is available for chemical processing, laboratory and pharmaceutical equipment, electronics and electrical systems, and semiconductor manufacturing.
Straight Lengths, Coils, and Custom PTFE Tubing
Supply format affects installation and production efficiency. Coiled tubing reduces joints in long runs and supports automated cutting, but retained curvature may be undesirable in instrument panels. Straight lengths simplify alignment and rigid routing. Cut pieces can reduce in-house labour when length tolerance, end condition, cleanliness, and packaging are controlled.
Custom PTFE tubing enquiries should include annual demand, order quantity, required dimensions, tolerances, lengths, packaging, marking, and inspection records. Special dimensions may require tooling or a production minimum, so qualification should begin before the equipment drawing is frozen.
PTFE Tubing Specification Checklist
Provide the following information when requesting a technical review or quotation:
- PTFE grade and any purity or filler requirement
- Inside diameter, outside diameter, and wall thickness
- Dimensional tolerances and critical inspection points
- Metric or fractional-inch unit system
- Fluid or gas, concentration, and exposure duration
- Normal and maximum temperature
- Normal pressure, peak pressure, vacuum, and cycling
- Fitting type, brand, and connection size
- Minimum bend radius and available routing space
- Coil, straight length, or custom-cut format
- Cleaning, packaging, traceability, and documentation
- Prototype quantity and expected repeat volume
Visit the PTFE tube product page for JIAFUXIN’s available grades, manufacturing routes, and dimensional reference data. The broader fluoroplastic tubing range provides alternatives when the application requires a different balance of clarity, stiffness, purity, or fabrication method.
Frequently Asked Questions
How are PTFE tubing sizes written?
PTFE tubing is commonly specified as ID × OD, OD × ID, or OD × wall thickness. Purchase documents should label each value clearly and state whether dimensions are metric or fractional-inch.
How do I calculate PTFE tube wall thickness?
Subtract ID from OD and divide the result by two. Tubing with an 8 mm OD and a 6 mm ID therefore has a nominal 1 mm wall. Tolerance limits must still be taken from the agreed drawing or specification.
Which dimension controls fitting compatibility?
OD is usually the main dimension for compression and push-to-connect fittings. Wall thickness, tube hardness, ovality, ferrule design, and the need for an internal support should also be checked.
Does a thicker PTFE tube wall increase pressure capability?
Greater wall thickness generally increases pressure capability when OD, material, temperature, and other conditions remain comparable. Final ratings still depend on the fitting, chemical, temperature, pressure cycle, and safety factor.
Can PTFE tubing be used under vacuum?
Vacuum suitability depends on tube OD, wall thickness, temperature, bend radius, support spacing, and external pressure. Thin-wall constructions may flatten or collapse and should be tested in the actual installation.
What is the difference between PTFE tube and PTFE hose?
Tube or tubing usually refers to an unreinforced product controlled by ID, OD, and wall thickness. Hose may include reinforcement, braid, an outer cover, or end fittings for higher pressure and more demanding handling.
Are Teflon tubing sizes the same as PTFE tubing sizes?
Teflon™ is a brand name associated with several fluoropolymers, while PTFE is a specific polymer. Buyers searching for Teflon tubing sizes should confirm that the required material is PTFE and specify the exact ID, OD, wall, grade, and service conditions.
Can PTFE tubing be supplied to custom dimensions?
Custom ID, OD, wall thickness, tolerance, length, colour, and packaging may be available within manufacturing and order-volume limits. Drawings and operating data help determine the suitable production route.
Should ID or OD tolerance be prioritised?
The critical dimension depends on the application. OD normally controls fitting compatibility, while ID controls flow, clearance, and internal volume. Both should be toleranced when the assembly depends on both functions.
Discuss Your PTFE Tubing Requirements
Reliable tube selection starts with the actual operating conditions and connection design. Send your dimensions, tolerances, fluid, pressure, temperature, fitting details, length, quantity, and packaging requirements through the JIAFUXIN contact page for a specification review.
