TRIBOLOGICAL ANALYSIS AND ANTI-GALLING DESIGN OF OCEAN-FLOOR PILE REFORMATION TOOL

A tribological analysis was performed on the sliding interfaces and lu brication system for a high capacity, underwater pile reformation tool . The 56 000 kg tool has a maximum wedging load of 5.0x10(4) kN and mu st operate at a water depth of 100-250 m. No previous application or d ata could be found for similar high contact stresses and low sliding s peeds, although sliding bridge bearing pads and airframe bearings gave some direction. The 5 degrees C salt water environment, however, impo sed the additional factor of corrosion, and it complicated grease sele ction since both water resistance and pumpability were competing requi rements. Based on the analysis, material selection and design modifica tions were proposed. Using a high-capacity, flat-on-flat friction test rig, laboratory tests were performed to obtain both sliding friction and wear data at contact stresses up to 690 MPa. The results were used to validate the effectiveness of the recommendations and to compute w ear coefficients from which service lifetime was predicted. Aluminum b ronze plates were retrofit to the cast stainless steel segments; a bak ed, porous phosphate and PTFE coating was applied to the carbon steel wedge; grease channel geometry was modified; and heavy duty, MoS2 fort ified grease was used.