EE WAS REPAIRING A BROKEN HYDRAULIC HOSE ON THE LOWER PORTION OF DREDGE CLAMSHELL BUCKET RAM. HE WRAPPED A CHAIN COME-ALONG AROUND THE SHAFT OF THE RAM TO MOVE THE RAM BACK FOR ACCESS TO THE HOSE FITTINGS. AFTER TENSION WAS APPLIED TO THE COME-ALONG, THE EE REACHED BEHIND THE RAM TO REMOVE THE BROKEN HOSE & THE HOSE FITTING. THE CHAIN ATTACHED TO THE RAM SLIPPED & ARM WAS CAUGHT.