Every process piping system expands and contracts as temperatures change. Every pump and compressor transmits vibration into the connected pipework. Without a flexible element at critical points in the system, these forces cause pipe joint failures, flange leaks, equipment nozzle cracking, and eventual catastrophic failure. In systems handling corrosive chemicals where no metallic material is safe, PTFE bellows and expansion joints are the engineered solution — providing the flexible, chemically inert connection that absorbs movement and vibration while maintaining an impermeable, totally corrosion-resistant flow path.
What Are PTFE Bellows?
A PTFE bellow is a flexible, convoluted tube of PTFE — shaped into a series of annular convolutions (corrugations) that allow the bellow to compress, extend, and deflect laterally while maintaining a continuous, leak-free internal surface. They are manufactured from thick-walled PTFE tube that is heated and hydraulically or mechanically formed into the convolution profile, then assembled with end flanges (PTFE stub-ends, carbon steel backing flanges, or custom end fittings) ready for installation in the piping system.
Types of PTFE Bellows and Expansion Joints
Single Arch Bellow
Single convolution; compact; absorbs limited axial and angular movement. Used where space is restricted and movement requirement is small. Most economical type.
Multi-Convolution Bellow
3, 5, or 7 convolutions; absorbs larger axial movement, lateral offset, and angular deflection. Standard for most chemical plant pump and agitator connections.
PTFE-Lined Rubber Expansion Joint
Rubber body with PTFE inner liner — combines rubber's high-movement capability and vibration absorption with PTFE's chemical resistance. For high-movement, high-vibration applications (centrifugal pumps).
Gimbal Bellow
With external gimbal ring constraining movement to one plane. Absorbs angular deflection in complex piping geometries requiring controlled movement direction.
Tied Bellow
With external tie rods limiting axial movement and transferring pressure thrust to the rods — allowing adjacent pipe supports and anchors to be designed without taking full pressure thrust load.
PTFE Hose / Corrugated Tubing
Flexible corrugated PTFE tube with wire braid reinforcement for pressure containment. For connections requiring high flexibility and pressure resistance — instrument lines, sampling connections.
Technical Specifications
| Parameter | Typical Range |
|---|---|
| Size range (bore) | ½" NPS to 12" NPS (15 mm to 300 mm); larger on request |
| Pressure rating | Full vacuum to 10 bar (standard); up to 16 bar with reinforced design |
| Temperature range | –200°C to +260°C (PTFE limits) |
| Axial movement (per convolution) | ±5 mm to ±15 mm depending on convolution geometry |
| Lateral offset | Up to 10 mm (multi-convolution) |
| Angular deflection | Up to 5° per convolution |
| End connections | PTFE stub-end + CS/SS backing flange; welded flanges; triclover; custom |
| PTFE wall thickness | 3 mm – 6 mm (grade and pressure dependent) |
Where PTFE Bellows are Used
The primary applications for PTFE bellows are wherever a flexible joint is needed in a chemically aggressive or ultra-pure piping system:
- Pump connections — between the pump nozzle and the connecting pipe on corrosive chemical transfer pumps. Absorbs pump vibration, thermal expansion of the pump body, and misalignment between pump and pipe centrelines.
- Agitator bottom nozzles — on reactor vessels and tanks with bottom-entering agitators, where the agitator shaft creates vibration that must not be transmitted rigidly into the vessel nozzle.
- Thermal expansion loops — at intervals in long runs of PTFE-lined pipe operating at elevated temperature, to absorb the axial thermal expansion of the line.
- Compressor suction and discharge connections — to isolate compressor vibration from downstream piping in corrosive gas systems.
- Glass-lined vessel nozzle connections — PTFE bellows are essential at glass-lined vessel nozzles to prevent stress transmission to the fragile glass lining from piping thermal movement.
- Vacuum service connections — PTFE bellows rated for full vacuum are used in vacuum evaporators and distillation equipment handling aggressive chemicals.
How to Specify a PTFE Bellow
When ordering PTFE bellows, provide the following information:
- Pipe bore size (NPS or DN) and pipe schedule
- Flange standard (ASME B16.5, BS 4504, DIN EN 1092, etc.) and pressure class
- Process chemical and concentration
- Operating temperature and pressure (including vacuum, if applicable)
- Required movement: axial compression/extension, lateral offset, angular
- Number of convolutions or overall face-to-face length required
- Backing flange material (CS, SS 304, SS 316, etc.)
Frequently Asked Questions
Can PTFE bellows handle hydrofluoric acid (HF)?
Yes — this is one of PTFE's key advantages over metal bellows. Virgin PTFE resists HF at concentrations up to approximately 60% at temperatures up to 60°C. At higher concentrations or temperatures, consult our engineers for specific service conditions. Note that no metal bellow — not even Hastelloy C-276 — provides long-term resistance to concentrated HF; PTFE is the standard choice.
What is the typical service life of PTFE bellows?
In properly designed installations with movement within the rated range and temperature within limits, PTFE bellows have service lives of 8–15 years. The main failure modes are fatigue cracking at the convolution roots from cyclic flexing beyond rated movement, and creep/thinning from sustained overpressure. Replacing bellows at planned maintenance shutdowns (typically every 5 years) is good practice for critical services.
Do you supply PTFE bellows with external reinforcement or wire braid?
Yes — for higher pressure ratings, PTFE bellows can be supplied with an external SS wire braid or external restraining rings that increase the pressure rating without significantly reducing flexibility. External braided PTFE bellows are typically rated to 25–40 bar depending on size and braid specification. Contact us with your pressure requirement for a specific quote.
PTFE Bellows & Expansion Joints — Standard & Custom
All sizes ½" to 12" NPS. Single and multi-convolution. PTFE-lined rubber type. Full vacuum to 16 bar pressure. Manufactured to your specifications.
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