MPS Global recently completed a comprehensive destructive testing program on 16-inch mechanical interference fit (MIF) connections, demonstrating that this weld-free technology significantly surpasses industry design standards for carbon steel flowlines. The testing program evaluated four full-scale joints fabricated from API 5L carbon steel against ASME B31.4/B31.8 criteria through bending tests, internal pressure tests, cyclic pressure-fatigue testing (100,000 cycles), and axial tension tests. Results showed the MIF connection exceeded code-based minimum requirements across all performance categories, with failures occurring outside the interference zone and confirming stable structural engagement.
While axial tension emerged as the governing limit state for MIF systems, the measured capacity still surpassed allowable longitudinal stress limits established for welded joints. The MIF technology continued to exceed all design requirements even after applying a conservative 20% reduction in allowable longitudinal stress to account for the unique load-transfer behavior of interference-fit connections. Finite-element analysis validated test results and helped quantify contact pressure, axial load transfer, and stress distribution patterns specific to MIF systems.
This study represents the first code-referenced structural evaluation of a full-scale 16-inch MIF connection and identifies how MIF connections can be used with existing designs. The testing confirms that MIF connections provide a reliable, high-performance alternative for flowline construction while highlighting the need for design criteria that reflect the distinct mechanical behavior of interference-fit technology. These findings establish a technical foundation for future standardization efforts and broader adoption of MIF connections in carbon steel flowline applications.
For more information about MIF technology and MPS Global’s testing capabilities, visit www.mpsglobal.com.