Flange Installation Best Practices: Bolt Torque, Gasket Selection, Leak Prevention
Flange Installation Best Practices
Published: April 10, 2026 | Category: Technical Guide
Introduction
60-70% of flange leaks are caused by improper installation, not manufacturing defects.
Pre-Installation Inspection
- Flanges: No cracks, smooth surface
- Gaskets: Correct material and size
- Bolts: Correct grade, no damage
- Piping: Proper alignment
Gasket Selection
Non-Metallic: NAF, PTFE, Graphite
Semi-Metallic: Spiral Wound, Camprofile
Metallic: Ring Joint (RTJ)
Bolt Torque Sequence
Pass 1: 30% (snug) → Pass 2: 60% → Pass 3: 100% (star pattern) → Pass 4: 100% (circular)
Common Mistakes
- Wrong gasket material
- Reusing old gaskets
- Over/under-torquing
- Uneven torque
- Dirty flange faces
Recommended Torque (A193 B7)
| Size | Class | Torque (ft-lbs) |
|---|---|---|
| 2″ | 150# | 95 |
| 4″ | 300# | 165 |
| 6″ | 300# | 260 |
| 12″ | 300# | 570 |
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