Question 1

At sea in the North Atlantic in Force 8, your bulkcarrier's hold bilge alarm activates for No. 3 cargo hold. As Master, describe your response.

Accepted Answer

BULK CARRIER HOLD FLOODING — EMERGENCY RESPONSE: CONTEXT — WHY BULK CARRIERS ARE PARTICULARLY VULNERABLE: bulk carriers have: (a) Large, single-skin side shell plating; (b) Hatch covers that are critical weathertight barriers; (c) Limited flooding margins if a hold floods in heavy weather; (d) History of catastrophic casualties from hold flooding (MV Derbyshire 1980 — 44 crew lost; MV Flare 1998; MV Stellar Daisy 2017). IMMEDIATE ACTIONS: (1) CALL MASTER: hold bilge alarm in Force 8 = emergency call immediately; (2) CONFIRM THE ALARM: send an officer to the forecastle area to observe. Is the bilge level genuinely rising? Is there water visible on the cargo surface?; (3) ASSESS RATE OF FLOODING: how quickly is the bilge level rising? What is the volume of the hold? Time to flood = volume / rate of ingress. This gives time available; (4) IDENTIFY THE SOURCE: (a) Hatch cover leakage (most likely in Force 8 — green water on deck forces water past seals); (b) Shell plating damage (grounding, collision); (c) Side shell corrosion (known risk in older bulkers); (5) REDUCE SPEED: immediately. Reduce ship speed to reduce: (a) Green water on deck (less pressure on hatch covers); (b) Structural loading; (c) Rate of water forcing past seals; (6) ALTER HEADING: consider altering to reduce sea impact on the forward section if the water ingress appears to be from sea over the bow; (7) BILGE PUMPING: start bilge pumps for No.3 hold. Can pumping keep pace with ingress?; (8) MAYDAY: if flooding rate exceeds pumping capacity and the hold will flood — MAYDAY immediately. Bulk carriers can capsize rapidly when a hold floods; (9) PREPARE TO ABANDON: immersion suits, lifeboats ready, account for all crew. MV Derbyshire — the defining bulk carrier casualty: the MV Derbyshire (1980) was a 169,000-tonne bulk carrier lost in Typhoon Orchid with 44 crew and no survivors. The MAIB/DfT formal investigation concluded that progressive structural failure of the fore hatch covers allowed flooding of the forward holds, leading to rapid loss of buoyancy and sinking within minutes. This casualty drove the enhanced bulk carrier structural requirements in SOLAS XII and the mandatory bilge alarm systems. The lesson: hold flooding in heavy weather can develop into catastrophic flooding in MINUTES. Early response is critical. Force 8 + hold bilge alarm = emergency response, not "wait and see." Speed in heavy weather (option D): increasing speed in Force 8 conditions with a suspected hold flooding creates: (a) MORE green water on forward hatches (higher bow wave); (b) Greater structural loading on already-stressed plating; (c) Higher rate of water ingress past any damaged or leaking seals. Speed MUST be reduced. Rate of flooding assessment: the key decision is whether pumps can keep pace with ingress. If the bilge level is rising faster than the pump can lower it — the hold will fill eventually. At that point — the vessel's reserve buoyancy is consumed in the flooded hold. For a large bulk carrier, flooding of one hold may not be immediately catastrophic — but flooding of two adjacent holds (progressive flooding) typically is. MAYDAY timing is therefore critical — better too early than too late.

Question 2

Before departure from Durban, your stability program shows the vessel meets 5 of the 6 IS Code criteria but the righting lever arm at 30° (GZ at 30°) is 0.18m against the required minimum of 0.20m. What do you do?

Accepted Answer

IS CODE CRITERIA — GZ AT 30° DEFICIENCY: THE SIX IS CODE CRITERIA (MSC.267(85) — IS Code 2008): the International Stability Code mandates SIX stability criteria that ALL must be satisfied: (1) Area under GZ curve from 0° to 30° ≥ 0.055 m·rad; (2) Area under GZ curve from 0° to 40° ≥ 0.090 m·rad; (3) Area under GZ curve from 30° to 40° ≥ 0.030 m·rad; (4) GZ AT 30° ≥ 0.200m; (5) MAXIMUM GZ at angle ≥ 25°; (6) GM₀ ≥ 0.150m. FAILING ONE CRITERION MEANS FAILURE: all six criteria must be satisfied simultaneously. A GZ at 30° of 0.18m (vs required 0.20m) is a FAILURE — the vessel does NOT meet IS Code intact stability criteria. THE VESSEL CANNOT DEPART: it would be UNSEAWORTHY for the intended sea voyage. REMEDIES — HOW TO CORRECT THE DEFICIENCY: (1) REDUCE CARGO: if cargo is high in the vessel, shifting weight lower increases the GZ at 30°; (2) LOWER THE G: reduce KG by: (a) Adding low ballast (double bottom tanks); (b) Removing top-heavy weights; (c) Shifting cargo lower; (3) INCREASE BEAM LOADING: for certain hull forms, a different loading pattern affects the GZ curve shape; (4) REDUCE FREE SURFACE: if slack tanks are contributing to reduced GM — fill or empty tanks to remove free surface effect; DOCUMENTATION: the master must not sail with a stability calculation showing non-compliance. This is ISM non-conformity — notify DPA. LEGAL: departure with known stability non-compliance = MSA 1995 Section 58 offence (taking an unseaworthy ship to sea). IS Code — mandatory treaty obligation: the International Stability Code (IS Code 2008, MSC.267(85)) is mandatory under SOLAS Regulation II-1/5-1. It is not guidance — it is a mandatory standard with which ALL ships must comply. Failing ONE criterion fails ALL six — they are not averaged. "Close enough" margin (option B): there is no concept of "within tolerance" for IS Code criteria. The 0.20m GZ at 30° is a minimum — not an average. A calculated value of 0.18m is non-compliant. Stability programs have their own accuracy considerations — but if the calculation shows 0.18m, the vessel is non-compliant and must be remedied before departure. Charterer responsibility (option C): the charterer prescribes the cargo but the MASTER is responsible for the stability of the loaded vessel. The master must assess the proposed loading plan and refuse to sail if the result is non-compliant. The master can agree with the charterer to adjust the loading to achieve compliance (different stowage, reduced quantity, added ballast) — but the master cannot blame the charterer for a stability failure. IS Code as guideline (option D): this is completely incorrect. The IS Code is cited in SOLAS and is a mandatory instrument for all flag states that have ratified SOLAS. It is enforced by flag state surveyors, classification societies, and PSC inspectors. A vessel that departs without meeting IS Code criteria is unseaworthy in law and the master faces criminal liability under MSA 1995 Section 58. What "GZ at 30° ≥ 0.20m" means physically: GZ is the righting lever — the horizontal distance between the line of action of buoyancy and gravity at a given angle of heel. A GZ of 0.20m at 30° means the restoring couple (GZ × displacement) is providing a meaningful self-righting force at that angle. Below 0.20m, the vessel has reduced ability to recover from a 30° heel — which in heavy weather could develop into capsize.

Question 3

Your vessel is listing to starboard at a steady angle of approximately 8°. The deck officer believes this is a list due to off-centre cargo but the second officer suspects angle of loll. How do you distinguish, and what are the correct actions?

Accepted Answer

ANGLE OF LOLL vs LIST — IDENTIFICATION AND RESPONSE: DISTINGUISHING FEATURES: (1) LIST (caused by off-centre weight): (a) The vessel rests to one side; (b) GM is POSITIVE; (c) The GZ curve is displaced sideways but still positive; (d) Filling a tank on the high side (away from the list) will CORRECT the list; (e) The vessel has a definite "preferred" upright position but is offset by the asymmetric loading; (2) ANGLE OF LOLL (caused by NEGATIVE GM): (a) The vessel has ZERO or NEGATIVE GM; (b) The GZ at zero degrees is ZERO; (c) The vessel has no stable upright position — it lolls to one side where the GZ curve has positive values; (d) The vessel may flop between loll to port and loll to starboard; (e) IDENTIFYING CHARACTERISTIC: if you forcibly push the vessel further to the loll side — it continues to heel further. If you push a listed vessel — it resists and returns; HOW TO DISTINGUISH ON THE VESSEL: (1) Look at the GZ curve from the loading computer: is GM positive (list) or zero/negative (loll)?; (2) Apply a small external force: does the vessel resist (list) or comply (loll)?; CORRECT ACTION FOR LOLL: (1) DO NOT FILL HIGH-SIDE DOUBLE BOTTOM TANKS FIRST: the counter-intuitive nature of loll. Adding ballast on the high side RAISES the centre of gravity FURTHER — makes GM MORE negative — the loll worsens. The vessel may VIOLENTLY FLOP to the opposite side; (2) CORRECT ACTION: add ballast SYMMETRICALLY to the LOWEST point first. Fill lowest double bottom tanks evenly port and starboard to lower G and raise GM above zero; (3) NOTIFY DPA: this is a serious stability situation. Why high-side ballasting is FATAL in angle of loll: this is the most counter-intuitive and critical point in the angle of loll topic. At angle of loll with negative GM: (a) Adding ballast to the high side raises G because the ballast centre is higher than the vessel's current G; (b) This makes GM MORE negative; (c) The loll worsens; (d) Suddenly adding water to a high-side tank when GM is negative can cause the vessel to VIOLENTLY FLOP to the other side through the unstable upright position; (e) The violent flop has caused capsizes and cargo losses in practice. The asymmetric ballast (option D): cross-flooding from the loll side to the high side raises G on both sides. If the cross-flooding ALSO raises G (because the tanks are above the existing G) — it makes things worse. The principle remains: lower double bottom tanks first, symmetrically. The violent flop: at an angle of loll, the vessel is in stable equilibrium AT the loll angle. As you correct the negative GM (by adding weight low down), there is a brief period where the vessel passes through UNSTABLE equilibrium at the upright position before developing positive stability. During this passage through zero stability, ANY external force (wave, wind) can cause a rapid angle change. The vessel may flop to the other loll angle. Crew and cargo must be secured during the corrective process. 8° list is acceptable (option C): a static 8° list at sea is NOT acceptable and is not normal. It indicates either asymmetric loading (which should be corrected) or reduced stability (angle of loll — which is dangerous). Any unexpected and persistent list requires investigation and correction.