In the design and maintenance of a 2-inch piping system, one of the most common debates is whether to use a 2" Threaded Pipe Flange or a 2" Slip-On Flange. While both are widely used in ASME B16.5 Class 150 applications, the choice between a threaded (NPT) connection and a welded connection can significantly impact your installation time, budget, and system safety.
What is a 2" Threaded Pipe Flange?
A 2 inch NPT flange features internal tapered threads that match the external threads of a pipe. It creates a mechanical seal without the need for welding.
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Key Advantage: Rapid installation in "Hot Work" restricted areas where welding is prohibited.
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Best For: Low-pressure, non-cyclic services, and systems that require frequent disassembly.
What is a 2" Slip-On Flange?
A Slip-On (SO) flange is designed to slide over the end of the pipe and is secured with two fillet welds (one inside and one outside).
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Key Advantage: Slightly better resistance to internal pressure and vibration compared to threaded joints.
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Best For: Systems where a permanent, leak-proof welded seal is preferred and welding equipment is readily available.
Direct Comparison: 2" Threaded vs. Slip-On
| Feature | 2" Threaded Pipe Flange (NPT) | 2" Slip-On Flange (Welded) |
| Welding Required | No | Yes (Double Fillet Weld) |
| Installation Speed | Fast (Manual or Tool Tightening) | Slower (Requires Weld & Cool Time) |
| Ease of Removal | Very Easy | Difficult (Must be cut) |
| Initial Cost | Moderate | Lower (But adds labor cost) |
| Seal Integrity | Dependent on Thread Sealant | Permanent Weld Seal |
Why Choose the 2" NPT Standard Flange for Your Project?
For many contractors, the 2" A105 carbon steel threaded flange is the preferred choice for several practical reasons:
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Safety in Volatile Environments: In refineries or chemical plants, "no-spark" zones make the threaded connection the only viable option.
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Ease of Repair: If a section of pipe is damaged, a 2" threaded flange can be unscrewed and replaced in minutes, reducing costly downtime.
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No Post-Weld Heat Treatment: For thicker materials, welding might require heat treatment; threaded flanges bypass this technical complication entirely.
Conclusion
While Slip-On flanges have their place in heavy-duty applications, the 2" Threaded Pipe Flange offers unparalleled flexibility and ease of use for Class 150 systems. By selecting a high-quality A105 forged steel product, you ensure a robust and compliant connection for your industrial needs.
Looking for specifications for other sizes? Check out our [1 1/2" Threaded Flange Guide]
