The above video is of the RivTow vessel Hercules, a self loading, self dumping log barge. Captain Don Rose tells us how the barge operates under normal operations:
On arrival at destination, a small tug will come alongside the Rivtow Capt. Bob and pick up the Mate and a Seaman and take them back to the barge. When the crew members are on the barge the small tug will put its towline on the barges stern to assist holding it in position while the pre-flooding and dumping proce- dures take place.
On the barge the crew will service the generating machinery and check that the cranes are locked in place. Confident that everything is secure the sea-chest will be opened along with a series of other valves to pre-flood ballast and tip- ping tanks with sea water. (Pre-flooding
and ballast transfer are done by gravity.)
With the pre-flooding completed, the barge in the right position on the com- mand of the Tug Master the timber dumping procedure will start. Because the RivTow Hercules discharges its load from the port side, ballast water is first transferred from the starboard side to the port side tipping tanks.
It is common that after all the ballast water is transferred to the port side of the barge, it has not dumped. With the ballast water transferred the sea-chest is opened to allow more water into the tipping tanks.
With the sea-chest open and water flowing into the tipping tanks the barge will continue to heal over. It is common for the barge to dump at 26 to 30 degrees of heal. Dumping time from arrival to departure usually takes from two to three hours.
When the barge dumps, it actually moves rapidly out from under the load. The load does not move until the barge has left it.
When the barge starts moving out from under the load it moves sideways to starboard at a rapidly increasing rate of speed for a considerable distance. At this time the small tug connected to the stern of the barge disconnects itself completely. The towing tug slips out its winch line so it will not be pulled over by the force of the barge moving sideways.
When the barge has settled down from its sideways run the Mate and Seaman close up the barge, leaving the sea-chest and tipping tank valves open to allow the forces of gravity to drain the water from it. The assist tug will then bring them back to the Rivtow Capt. Bob and another trip to load logs will begin. In about an hour she will level off.