Failure Mechanism and Modification Strategy of the Four-Way Pipe Fitting in CHMFL’s Cooling Water System

Abstract The Chinese High Magnetic Field Laboratory (CHMFL) operates globally unique high-steady magnetic field facilities that support research in cutting-edge scientific domains. As for cooling the magnet, the flow rate of water reaches <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="1,200 normal m cubed divided by normal h" display="inline" overflow="scroll"> <mml:mn>1,200</mml:mn> <mml:mtext> </mml:mtext> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">/</mml:mo> <mml:mi mathvariant="normal">h</mml:mi> </mml:math> through stainless steel pipe subjected to 3 MPa operational pressure, resulting in recurrent structural failures at four-way pipe fittings. The finite-element analysis was adopted to systematically examine failure mechanisms. Computational results demonstrate that stress concentrations at the shoulder transition zones and abdominal sections of the four-way connectors exceed the material’s ultimate tensile strength, correlating with observed fracture patterns in operational components. Parametric studies reveal that a smaller pipe diameter and larger main-branch intersection angle result in lower stress of four-way fittings. Through comprehensive evaluation of hydraulic performance and economic flow parameters, the DN400 configuration with 60° angular geometry emerges as an optimized solution, achieving maximum von Mises stress of 351.63 MPa. Alternative implementations utilizing dual reverse tee fittings (DN500 specification) demonstrate superior mechanical performance with peak stress reduction to 174.63 MPa, while maintaining full magnet operational compatibility. These findings establish novel methodologies for fluid conveyance system optimization in large-scale scientific infrastructure.