a molded plastic vessel is provided with a fitting or other attachment after molding and before winding of the vessel . the fitting is provided with a plastic insert . the insert and a wall of the vessel are heated and welded together to hold the fitting on the vessel . the tank is filament wound for reinforcement , and the filaments capture the fitting to hold the fitting on the wall . the wall is opened to provide a passage through the fitting into the vessel . an apparatus is provided that carries and moves the fitting , insert , and a heater to install the fitting on the vessel .