Automated bolting and head handling for multi-flange pressure-vessel closures: a simulation-based design evaluation with a delayed-coking case study

Abstract

Large bolted closures on process vessels are still assembled largely by hand, often in hazardous areas, using multipass tightening sequences whose duration and preload outcome are rarely quantified. An automated architecture for such closures is evaluated in this paper: orbital pneumatic torque runners on the flange, a bolt-management carousel, a counterbalanced head manipulator and an interlocking sequence controller, applied to a 92-bolt, three-flange delayed-coking drum. A Monte Carlo model built on the actual star-pattern tool travel shows that one torque head per flange needs a median of 8.0 h to unbolt and rebolt the drum and, within the investigated parameter bounds, cannot meet a 2.5 h target. Removing bottlenecks in turn gives 2.3 h with four synchronized heads and 1.8 h with a bolt-transfer channel per head, the preferred simulated configuration, which meets 2.5 h in 98% of samples; one fewer star pass would give 1.6 h but requires qualification. This ranking held across all 20,000 simulated samples under uniform, triangular and correlated input models. An exactly optimized tool path adds little, and the complete operation remains at approximately 3.4 h, governed by head handling and leak testing. Specifying the ±2% torque accuracy barely affects the preload scatter; under an assumed 3% angle-based preload-estimate uncertainty, the torque–angle retorque cuts the bolts outside ±10% of the target from 32% to 5%. Exhaustive verification revealed no safety violation but exposed deadlocks after interrupted sequences, which a resume rule removed. All the results are predictions; an experimental falsification plan is given.