Benny Cenac: Towing on the History of Dry Docking

Posted to Maritime Reporter (by on March 3, 2020

Benny Cenac of Houma knows that dry docking a vessel every 1-5 years will maintain its best fuel efficiency and structure.

  • Personnel at Benny Cenac’s Houma business, Main Iron Works, clean the hull of the boat with high-powered washers.

  • With workers able to access all surfaces on the exterior, the dry dock allows for hull painting and its initial requiring washing and blasting activities to proceed, explains Benny Cenac of Houma.

Benny Cenac’s towing expertise has a long history. From the time it was founded in 1948, Main Iron Works has grown in step with the Gulf of Mexico’s oil and gas industry. First located near the site of Terrebonne General Medical Center on Bayou Terrebonne, the company was initially concerned with refurbishing oyster luggers to meet the needs of the industry, which required vessels capable of traveling sometimes treacherous shallows to haul equipment and workers.

Founder Horace “Jack” Guidry and his first employee Lawrence Mazerac transformed the business of converting wooden boats for the oilfield to constructing their own durable steel-hulled vessels, moving for a time to Bayou LaCarpe and then to the current Main Iron Works site on the Gulf of Mexico Intracoastal Waterway at Mile Marker 50; it is reached by land on Old Ferry Road off of Bayou Blue Road.

The leaders of the company knew that, in addition to building boats, they would need to service them, and their original dry dock was used for that purpose. Demand from other marine service operators to have their own boats serviced and checked resulted in greater growth, and by the time Main Iron Works was producing steel-hulled vessels, all manner of industrial boats were checked, serviced, patched and otherwise repaired. In the early days, a traditional method of hauling boats up by use of winches and a railway-like set of tracks to keep them in place was mostly employed.
Among the clients of Main Iron Works was the Cenac Towing Company, owned by Arlen “Benny” Cenac Jr., continuing the tradition of a relationship with the company. Benny Cenac, a third-generation owner of the company, acquired Main Ironworks in 2015. The Cenac fleet of tugs and barges were then serviced at the Old Ferry Road site, and the company continued welcoming vessels for service from all over the oilfield. Stressing safety and reliability above everything else, the good name of Main Iron Works was kept.

Unlike the old days of winches, chains and tracks, Main Iron Works today employs a system of what are called “floating docks.” When Benny Cenac acquired Main Iron Works in 2015, the company had three serviceable floating docks. Since then the company has added another. The biggest of these has a 4,500-ton capacity. As the Occupational Safety and Health Administration explains, the most dangerous time in drydocking occurs when support for the ship is changing from water buoyancy to dry dock blocks. If the strength of the blocks is insufficient, they can be crushed and overturn the ship.

The system itself consists, then, of four sets of chambers with U-shaped walls surrounding each. When a chamber is to be used it is filled up with water through a pipe and valve system. The system’s floor or deck is overcome by the water, purposely. With the dock submerged, the vessel needing work done above it is moved inside the chamber over water. Over an average of approximately two hours, the water is pumped from the dry-dock. The water is then pumped out of the chambers, allowing the dry dock to rise, thereby, lifting the ship out of the water. Main Iron Works’ lock and place systems are positioned on the bottom of the dock once it’s dry – or perhaps more descriptively a “damp dock”. Anchors and cables are then inspected and measured to determine the quality and condition, and parts deemed defective are repaired or replaced.

Vessels are drydocked every 12 months to five years, as there could be machinery and systems that cannot be stopped while the ship is in use; these are all serviced, repaired or replaced at the same time. The normal steps for dry docking are as follows: the hull is cleaned of marine growth; the outside is blasted with anti-corrosive and anti-fouling paints; the hull and tail shaft bearing is inspected and repaired; shipside gratings are cleaned and repaired; and the tanks, rudder, propeller, shaftings, and carrier ring are surveyed and cleaned. Locking devices clearances and all overboard and sea suction valves are examined during the dry docking process. Once the vessels are put back into service, they are more eco-friendly and fuel-efficient—otherwise strengthening Benny Cenac of Houma’s commitment to conservation and environmental matters.

The Dry Docking Process at Benny Cenac’s Houma Main Iron Works

Multiple types and sizes of vessels can be accommodated at dry docks, such as those at Main Iron Works. Dimensions on the different components can be varied. This flexibility provides a maximum of stability for the docked vessels, and therefore, safety for the structures and the individuals working tirelessly on them.

With workers able to access all surfaces on the exterior, the dry dock allows hull painting, itself a multi-layered process requiring washing and blasting prior to paint even being applied. The hull painting consists of washing, blasting and painting of the vessel and is one of the main reasons for dry-docking, as it ensures efficient vessel operations for the next five years. The underwater side is painted with anti-fouling paint to prevent marine growth and ensures the vessel operates close to its original design speed and fuel consumption. After months or years of sailing and service, it is likely that marine growth such as algae or slime will build up on the sides of the vessel. But those types of build-ups can hamper the speed of a vessel and leads to higher fuel consumption, and in some cases, damage its ability to properly function altogether. High-pressure washers are used for this phase; the blasting is done to remove rust, barnacles, or bad paint.

Main Iron Works personnel use high-pressure washers of fresh water to remove marine growth and chlorides from the ship side. Blasting removes rust or defective paint from the ship side. Depending on the need of each vessel, blasting is either localized or carried out along the entire side of the vessel. In the blasting process, old paint in the defective areas is removed entirely to expose the bare steel. Upon basting completion, the entire vessel is cleaned and painted to protect the integrity of the steel and limit future corrosion. The sea chest is a recess in the hull of the ship that provides intake of sea water for the ship’s fire pump systems in the engine room. Main Iron Works employees open the sea-chest area during the dry-docking process for cleaning, inspecting and painting, concurrent to the valve inspection and overhauls.

After the dry docking work has been completed, the dock is flooded and prepared for the vessel’s departure. The vessel is towed out of the dry-dock by shift tugs and Main Iron Works shipyard personnel. The vessel is taken to a safe anchorage area and another round of sea trials are carried out to confirm repairs and machinery are working as expected. If the sea trials are successful, the vessel – now more clean, efficient, and otherwise improved from before – can be commissioned back into service.

Tags: Dry Docking Towing

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