The B-52H is a bit different than most commercial aircraft in that it has two engines mounted to each underwing pylon rather than just one. In both cases the engines are attached to the pylon with "fuse pins". When an engine experiences something like a "blade-off" failure that produces a significant dynamic imbalance vibration condition which can cause structural failure of the wing, the fuse pins are designed to shear and allow the engine to drop away from the pylon, limiting structural damage to the wing.