Steel Replacement Mapping for T/B ROCKLANDApr 21, 2008 12:00 AM The Reinauer Transportation Companies (RTC) tank barge ROCKLAND underwent a scheduled ABS survey and gauging. ROCKLAND is a 67,000-barrel, ABS classed tank barge. The gauging survey identified a significant number of areas of steel requiring replacement. These included side shell and bottom stiffeners and a considerable portion of the main deck. It was difficult to interpret the 200-plus page gauging report and devise the most efficient plan for steel replacement without a visual “map” of the corrosion.
RTC requested JMS analyze the gauging report and convert the data into an easy to read, color-coded format. The visual format would allow RTC and the shipyard to clearly see the sections of vessel plating and associated stiffeners that required cropping and renewal. This allowed for a quick determination of the scope of work and efficient planning and budgeting by the shipyard.
ABS requirements state that all steel that has been gauged at or below 75% of the rule required thickness must be renewed at the rule thickness. ABS defines substantial corrosion as steel that is gauged between 75% and 81.25% of the required rule thickness but replacement of steel in such areas is not required. However, if not replaced, ABS requires these areas to be gauged annually, which requires the vessel to be removed from service.
JMS developed an excel spreadsheet that used Visual Basic programming to read the gauging report. The JMS spreadsheet arranged the width and height of the columns and rows to visually represent the plating as well as the web and flange of the associated stiffeners. The values from the gauging report were placed into the corresponding locations and each cell was color-coded based on the value of the gauging.
All areas that were gauged less than 75% of the required thickness were colored red and areas of substantial corrosion were colored blue. RTC was also interested in a prediction of the hull condition at the next scheduled survey in five years. JMS highlighted structural members that gauged between 81.25% and 83.25% of required thickness in green. This corresponds to a 2% corrosion rate over five years. If gaugings within this range were located adjacent to sections that are to be removed during the current steel replacement, it would be cost efficient to also remove the extra steel now rather than wait until the next scheduled survey.
Dry Dock Ballast System for Pacific Shipyards International
JMS was selected to design the piping, pumping, and power system to control ballasting and de-watering operations for new dry dock extensions being built for Pacific Shipyards International (PSI) in Hawaii. Heger Dry Dock of Holliston, MA provided the structural design and contracted JMS to provide the detailed systems design. PSI will have the extensions built in China and towed to Honolulu where they will mate them to their existing 53-meter floating dry dock.
Each extension will be 39 meters wide, 13 meters deep, and 20 meters long, significantly increasing lift capacity. The JMS design objective was to produce a system with flooding and pumping characteristics similar to the existing center dock but operating independently of the old ballasting system.
The existing dock pumping system dictated flooding and pumping rates for the new system. Original drawings guided the design of the extension system including the ability to “power flood”, pumping water during ballasting operations to augment the gravity flow. The extensions will have their own machinery rooms in the wing walls for the electric control valve actuators and power distribution equipment. Ballasting/de-watering operations will be controlled from the existing central control room.
JMS recommended the use of submersible pumps to eliminate the need for long pump drive shafts that require bearings, pump room deck stuffing box seals, and alignment considerations. Specifications for pump and valve equipment had to account for equipment suppliers in China where the dock extensions are to be built. Actuators, control, and monitoring functions are to be outfitted with U.S. equipment after delivery to PSI in Honolulu.
JMS supplied general arrangement and one-line drawings for piping, pumps and valves; conducted an electrical load analysis; developed electrical system drawings showing power and control for the system; and provided a detailed specification list of all equipment to be used.