Threaded Flange Overview
A Threaded Flange connects to pipes using internal threads, eliminating the need for welding. This makes threaded flanges ideal for applications where welding is impractical or where quick installation and disassembly are required.
Design Characteristics
- Internal threads match pipe external threads (NPT or BSP)
- No welding required for installation
- Tapered threads create metal-to-metal seal
- Often used with sealant tape or compound
Main Advantages
- No Welding: Perfect for hazardous areas where welding is restricted
- Quick Installation: Simple screw-on assembly
- Easy Maintenance: Can be unscrewed for inspection or replacement
- Cost-Effective: Lower labor costs, no welding equipment needed
- Versatile: Suitable for various pipe materials
Limitations
- Not suitable for high-pressure applications
- Thread corrosion can cause leakage
- Limited to smaller pipe sizes (typically NPS 4 and below)
- Not recommended for systems with thermal cycling
Common Applications
- Low-pressure water and air systems
- Fire protection sprinkler systems
- Instrument and gauge connections
- Temporary piping installations
- Hazardous locations (no hot work permit required)
- Compressed air distribution
Thread Standards
| Standard | Description |
|---|---|
| NPT | American National Pipe Tapered (ASME B1.20.1) |
| BSP | British Standard Pipe (parallel or tapered) |
| PT | Japanese tapered pipe thread |
Pressure Ratings
- Class 150: Up to 285 psi at ambient temperature
- Class 300: Up to 740 psi at ambient temperature
- Class 600: Up to 1480 psi at ambient temperature
Installation Best Practices
- Clean threads on both flange and pipe
- Apply appropriate thread sealant (PTFE tape or compound)
- Hand-tighten first, then use wrench for final tightening
- Do not overtighten – can damage threads
- Leave 1-2 threads exposed for proper engagement
Threaded flanges provide a practical, weld-free solution for low-pressure piping systems where quick installation and maintenance access are priorities.
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