The torque requirements for PTFE gaskets according to EN 1591-1 depend on the type of PTFE material used (virgin vs. structured/expanded) and its Pressure Qualification Ratio (PQR). Virgin PTFE typically requires higher torque due to its lower PQR, while structured or expanded PTFE allows for a broader torque range, offering more flexibility in achieving flange tightness. The standard provides both minimum and maximum torque values to ensure proper sealing without damaging the gasket or flange.
Key Points Explained:
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EN 1591-1 Torque Calculation Framework
- The standard specifies methods to calculate minimum and maximum torque values for bolted flange connections to achieve leak-tight joints.
- Torque requirements are influenced by gasket material properties, flange design, and operating conditions.
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Virgin PTFE Gaskets
- Higher torque requirements due to low Pressure Qualification Ratio (PQR).
- PQR reflects the gasket's ability to maintain sealing under pressure—virgin PTFE has lower resilience, necessitating tighter bolt loads.
- Example: A typical virgin ptfe gaskets for flanges may require torque values at the upper end of the EN 1591-1 range to compensate for material creep.
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Structured/Expanded PTFE Gaskets
- Wider torque range permissible due to improved PQR from microstructural modifications (e.g., porosity or filler reinforcement).
- These variants exhibit better stress retention and flexibility, allowing lower minimum torque while maintaining seal integrity.
- Example: Expanded PTFE gaskets might achieve tightness at 60–80% of the torque required for virgin PTFE.
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Practical Implications for Purchasers
- Material selection: Structured/expanded PTFE is often preferred for applications where flange loading variability or vibration is a concern.
- Installation guidelines: Follow EN 1591-1 torque tables and consider gasket-specific manufacturer data (e.g., for multi-layer or reinforced PTFE).
- Cost vs. performance: While virgin PTFE is cheaper, structured PTFE may reduce long-term maintenance costs due to lower bolt load sensitivity.
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Compliance and Safety
- Always verify torque values against the latest EN 1591-1 revisions and project-specific flange design criteria.
- Under-torquing risks leaks; over-torquing can crush PTFE, leading to cold flow and joint failure.
Have you evaluated how gasket thickness and flange surface finish might further influence these torque requirements? These factors, though secondary to PQR, can fine-tune the optimal torque range for your specific application.
Summary Table:
| PTFE Type | Torque Requirement | Key Consideration |
|---|---|---|
| Virgin PTFE | Higher torque | Lower Pressure Qualification Ratio (PQR) |
| Structured/Expanded PTFE | Wider torque range permitted | Improved PQR due to microstructural modifications |
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