Nibulon launched its second harbor pusher tug last week, part of plan to build four over two years. Equipped with powerful Scania engines, the 80-ton tugs are used for mooring and pushing 3,000 dead weight ton barges through shallow waters. The Nibulon shipyard also is making smaller tugs and river barges. Nibulon has a fleet of 77 vessels, almost all for river work.