Starboard List During Umbilical-Reel Loading
At 04:20, a 150-ft deck barge is loading 18 umbilical reels for a subsea job. The barge has four ballast tanks; No. 2 port is pressed full, No. 2 starboard is half full, and No. 1 tanks are empty. The barge has developed a 3° starboard list. The load plan calls for 12 more reels, and the deck crew has placed the last four reels 6 ft to starboard of the centerline because the crane reach is shorter there. The barge master's load sheet shows a calculated list of 1.5° before the last four reels. The forecast is 25 kt of wind from starboard with 2-ft chop. The supervisor says, "The list helps the deck drain; keep loading and we will pump the port tank later." A sounding shows No. 2 starboard tank has 4 ft of free surface and No. 2 port is full. The tide is falling, and the barge is already at its calculated draft mark. No one has recalculated stability since the reels were shifted.
1. What stability and loading concerns does this situation present? Explain the effects of the list, free surface, wind, and off-center reels.
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The 3° list is already double the calculated 1.5°, and the last four reels were shifted 6 ft to starboard, so the actual heeling moment is worse than the load sheet. No. 2 starboard is half full, creating free surface that reduces effective GM and lets the barge roll more; the port tank is full, so "pump the port tank later" is not a simple correction. Wind from starboard adds a steady heeling moment and the 2-ft chop adds dynamic roll. Falling tide and already being at the draft mark reduce underkeel clearance and reserve buoyancy. Adding 12 more reels adds weight and VCG; the barge could exceed draft/load line or lose stability.
2. What immediate actions should the barge master and supervisor take before any more reels are loaded?
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Stop loading. Sound all tanks, read drafts fore/aft/port/starboard, verify the actual reel weights and positions, and calculate weight, LCG, VCG, free surface, and GM with the current condition. Do not press up or transfer ballast until the competent stability authority approves a plan; avoid partial tanks and keep free surface to a minimum. Correct the list deliberately, then check the load line/draft and underkeel clearance. Restrict personnel from the low side and secure the deck. Notify the barge master and marine assurance; do not resume until the calculated list is within the approved limit and the wind/sea limit is acceptable.
3. If the job must continue, outline the load and ballast plan you would require, including who must approve it.
Read the worked answer
Require a revised load plan that keeps reels centered or symmetrically placed, sequences lifts so list is checked after each reel, and uses a ballast plan with tanks either full or empty. Set a maximum list (for example, 1° or the barge's approved limit), a wind/sea limit, and a draft/load-line limit. The plan must be approved by the barge master and a competent stability authority (naval architect/marine warranty surveyor as required). Monitor drafts and list after each lift; stop if the list grows or free surface increases. If the plan cannot be approved before the tide, delay loading rather than "pump later."