General Description of the Machinist Floating Dry-Dock
Robert Heger presented the Machinist floating dry-dock at the International Dry Dock Conference in Houston, Texas, in May 2017. This substantial marine structure includes the following specifications: Length Overall: 833 ft.
- Width Overall: 176 ft.
- Pontoon Deck Length: 772 ft.
- Clear Interior Width: 144 ft.
- Depth of Pontoon at Center Line: 17.7 ft.
- Total Depth to Top of Deck: 68.7 ft.
- Design Capacity: 30,000 LT Buoyant
- Capacity per Foot: 55 LT/FT
About Heger Dry Dock, Inc.
Robert Heger, President and Chief Engineer of Heger Dry Dock, Inc., specializes in the design and inspection of floating dry docks and marine railways. He provides consultation on all types of dry-docking-related problems and is recognized as a legendary pioneer in the field. Heger is also the primary lecturer for Dockmaster’s Training Seminars, which teach dockmasters, naval architects, and marine engineers the basic principles of ship docking.
Heger’s Presentation: Salvage and Renovation of the Machinist AFDB-8
During the conference, Robert Heger delivered a two-part presentation on the Machinist AFDB-8 floating dry-dock.
A typhoon in Apra Harbor, Guam, resulted in the sinking of the Machinist. Heger was assigned the technical task of refloating the dry-dock. He executed systematic closure of hull apertures, dewatering of pontoons and wing walls, and integrated hydrostatic drafts, deflection data, water temperature readings, and engineered ballast calculations into his precision docking controls.
Part Two: Renovation and Transport
After being salvaged, the floating dry dock required renovation to increase its lift capacity and meet NAVSEA 1625-D certification requirements. The renovation was to be conducted in China due to more affordable costs. However, the dry-dock could not be towed in its current condition, and its length prevented it from being loaded onto a heavy-lift ship.
Solution: Sectioning and Transporting the Dry-Dock
Heger’s solution was to cut the dry-dock into sections while afloat at its berth. The two sections would then be loaded onto a single heavy-lift vessel, with their longitudinal axes aligned at 90 degrees to the vessel’s axis.
He planned the separation of the dry-dock as close to amidships as practicable to minimize structural movement during the cutting operation. The team systematically adjusted ballast in both sections before and during cutting to replicate the draft conditions for each hull segment post-separation.
Process Development
To achieve this, Heger developed two processes:
- Preparation and Control: The process consisted of several steps. First, weight surveys and draft readings were completed. Next, dock displacement was calculated and compared to weight estimates. Deflection readings were then performed, followed by consideration of weather conditions and water temperature. For controls, shear beams were installed, gap monitors were set up, exposed non-watertight bulkheads were made watertight, and a temporary ballast system was installed.
- The team began the cutting process by first working on the longitudinal members. Next, they cut the pontoon sides, then the deck, and finally the bottom plate. Afterward, they cut the wing walls, safety deck, and mid deck. The process concluded with the final cut at the wing shells; no movement was detected during separation. Both sections were perfectly ballasted and ready for transport.
Outcome and Innovations
Heger’s concept led to the development of a safe method for sectioning a floating dry-dock. The team integrated docking principles into production work, adjusting ballast during cutting and removal. They established a six-step cutting plan, conducted weight surveys, and recorded draft and deflection readings. The team employed temporary pumps, gap readers, shear beams, and wire ropes to control ballast and assist with the cutting. They closely monitored the dock’s longitudinal deflection, gap measurements, drafts, and weather throughout. The team completed the project safely, with no issues arising during separation.