Working Safety Analysis of Iron Roughneck Arm Used in Seabed Drilling

As the exploration and exploitation of petroleum gradually shift from land to ocean, from shallow sea to deep sea and then to ultra-deep sea, the conventional onshore iron roughnecks are unable to work directly on deepwater offshore platforms. To address this issue, a new type of iron roughneck arm structure supporting the seabed drilling system was proposed. The numerical simulation method was used for safety analysis on the strength, fatigue strength, stiffness, stability and vibration resistance of the iron roughneck arm structure. According to the research results, when the structure of the iron roughneck arm used in seabed drilling is in a dangerous posture(extending 1.8 m), the maximum von Mises stress is 195.45 MPa(less than the allowable stress [σ]=320 MPa), and the fatigue strength safety factor n=4.63(greater than the allowable safety factor [n]=2.0). The total flexural rigidity and the flexural rigidity in the x, y, and z directions of the iron roughneck arm structure are 1.11×10¹⁰, 1.62×10¹², 2.43×10¹³ and 7.34×10¹⁰ N·m², respectively, meeting the rigidity requirements of the iron roughneck arm structure. The critical buckling load of the iron roughneck arm structure P_cr=915.80 kN, which is 45.79 times the actual load, meeting the stability requirements of the structure. There is a 68.23% probability that the maximum von Mises stress of the iron roughneck arm structure does not exceed 179.77 MPa under random vibration excitation, meeting the material strength safety requirements. The research results have verified the safety and reliability of the designed structure of the new type of iron roughneck arm used in seabed drilling, and provide some reference for the structural design of it.