As a technical consultant with over 20 years of experience in piping systems, I am frequently asked by distributors and engineers in the oil, gas, and water treatment sectors: "For a mid-sized 2-inch piping system, should I go with a 2" slip on flange or a 2 inch threaded flange?"
While both comply with ASME B16.5 standards and are widely used in Class 150 flange connection setups, they offer fundamentally different advantages in installation logic, cost structure, and application suitability. From a professional engineering perspective, here is the breakdown of why the threaded option remains an indispensable choice for specific environments.
Why Threaded Connections? (The Convenience Factor)
In a 2-inch piping system, threaded pipe flange selection is primarily driven by its unique joining method.
Threaded flanges are designed with internal threads that match the external threads on the pipe. This process requires absolutely no welding. For A105 forged steel flanges, precision in thread machining is the cornerstone of a leak-free seal. ASME B16.5 dictates strict requirements for thread taper, form, and finish.
In contrast, a 2" slip on flange requires the pipe to be inserted into the flange bore and then fillet welded on both the inside and outside. The primary convenience of the threaded connection lies in its "plug-and-play" nature, making it ideal for tight spaces or sites where professional welding equipment is unavailable.
Cost Analysis: Welding vs. Threading
From a Total Cost of Ownership (TCO) perspective, choosing a 2 inch threaded flange often yields significant budget savings:
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Labor Costs: Slip-on flanges require certified welders and a two-step welding process, often followed by non-destructive testing (NDT). Threaded connections can be completed by basic pipefitters, drastically reducing man-hours per joint.
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Equipment Overhead: Welding requires power sources, shielding gases, and hot-work permits. Threading requires only sealant tape or compound and a pipe wrench.
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Maintenance Flexibility: Threaded flanges offer superior reusability during system maintenance or pipe replacement, allowing for quick disassembly without cutting the pipe.
However, it is crucial to note that these cost benefits are most effective in low-to-medium pressure environments like a Class 150 flange connection. Because A105 forged steel possesses excellent mechanical properties, it ensures the 2-inch threaded joint maintains structural integrity over long-term operation.
When to Choose the 2" Threaded Flange?
While slip-on flanges have their place in high-pressure or extreme vibration services, the 2 inch threaded flange is the industry standard for these three scenarios:
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Explosive Environments (Non-Hot Work): In refinery retrofits or gas stations where welding sparks pose an extreme safety risk, threaded flanges allow for safe installation without "hot work."
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Low-Pressure Utility Lines: For water treatment, HVAC loops, or compressed air lines, Class 150 threaded flanges provide a robust seal with much faster installation times than welding.
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Temporary Piping & Test Rigs: For systems that require frequent path adjustments or short-term usage, threaded connections offer unmatched ease of disassembly.
Conclusion
When selecting a 2-inch flange, engineers must balance safety, compliance, and economics. While slip-on flanges are versatile, the 2 inch threaded flange is the most cost-effective and efficient solution for low-pressure, non-welding environments.
If you are planning your next piping project and looking for high-quality connection solutions, understanding the physical limits and standard compliance of your products is key.
Check our [2 Inch Threaded Flange - ASME B16.5 Class 150 A105] specifications and A105 material certifications to ensure your system has the most reliable connection.
