PTFE gaskets for flanges are available in standard nominal pressure ratings (PN) including PN2.5, PN6, PN10, PN16, PN40, PN63, and PN100. These ratings indicate the maximum pressure the gasket can handle under standardized conditions. While PTFE offers excellent chemical resistance and a wide temperature range (-200°C to 260°C), its mechanical properties like creep and cold flow limit its effectiveness in high-pressure applications unless reinforced. The gaskets are rigid and non-reusable, requiring careful selection based on system pressure, temperature, and chemical exposure to ensure long-term sealing integrity.
Key Points Explained:
1. Standard Nominal Pressure Ratings (PN)
PTFE gaskets for flanges adhere to the following pressure classes:
- PN2.5: Low-pressure applications (2.5 bar)
- PN6: 6 bar
- PN10: 10 bar
- PN16: 16 bar
- PN40: 40 bar
- PN63: 63 bar
- PN100: High-pressure scenarios (100 bar)
These ratings align with international flange standards (e.g., DIN, ANSI) and must match the flange’s PN rating for compatibility.
2. Size Compatibility (DN Ranges)
PTFE gaskets are manufactured for flange sizes from DN15 to DN2000, covering common pipeline diameters. Key sizes include:
- Small-bore (DN15–DN50)
- Mid-range (DN65–DN300)
- Large-diameter (DN350–DN2000)
The DN (Diameter Nominal) must correspond to the flange size to ensure proper fit and sealing.
3. Material Limitations and Considerations
- Creep and Cold Flow: Pure PTFE deforms under sustained pressure, leading to seal failure. Reinforced PTFE (e.g., with glass or graphite) improves performance for higher PN ratings.
- Non-Reusability: Once compressed, PTFE gaskets lose their sealing ability if disassembled.
- Temperature Resilience: Ideal for extreme temperatures (-200°C to 260°C), but thermal cycling may accelerate creep.
4. Selection Guidelines
- Low-Pressure Systems (PN2.5–PN16): Pure PTFE suffices for corrosive/thermal applications.
- High-Pressure (PN40–PN100): Opt for reinforced PTFE or hybrid designs (e.g., PTFE envelopes with filler materials).
- Chemical Exposure: PTFE’s inertness makes it suitable for aggressive media, but mechanical reinforcement may be needed for acidic/alkaline environments.
5. Industry Applications
Common in:
- Chemical processing (reactors, acid lines)
- Pharmaceuticals (sterile systems)
- Energy (steam/pipeline systems)
Always verify PN/DN compatibility with flange standards (e.g., ASME B16.21 for ANSI flanges).
6. Installation Tips
- Use uniform bolt torque to prevent uneven compression.
- Avoid over-tightening, which exacerbates cold flow.
- Replace gaskets after disassembly—never reuse.
By balancing PN ratings with PTFE’s material behavior, engineers can optimize gasket performance for specific operational demands.
Summary Table:
| Pressure Rating (PN) | Max Pressure (bar) | Typical Applications |
|---|---|---|
| PN2.5 | 2.5 | Low-pressure systems |
| PN6 | 6 | General industrial use |
| PN10 | 10 | Moderate-pressure pipelines |
| PN16 | 16 | Chemical processing |
| PN40 | 40 | High-pressure systems |
| PN63 | 63 | Energy and steam applications |
| PN100 | 100 | Extreme-pressure environments |
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