Question 1

Your vessel has displacement 18,500 tonnes, LBP 140m, LCB = LCF = 68m from AP. The cargo officer proposes moving 200 tonnes of cargo from position 120m from AP to position 20m from AP. Calculate the change in trim and state the effect on the drafts forward and aft.

Accepted Answer

Trimming moment = mass x shift distance = 200 x (120-20) = 200 x 100 = 20,000 tonne-metres. Change in trim = trimming moment / MCT1cm. MCT1cm = (W x GM_L) / (100 x LBP). Assuming GM_L from stability data (approx 200m for this ship size): MCT1cm ≈ (18,500 x 200) / (100 x 140) = 3,700,000 / 14,000 ≈ 264 tonne-cm. Change in trim = 20,000 / 264 ≈ 75.8 cm by the head (forward increases, aft decreases as weight moved forward). Change in aft draft = -(LCF from AP / LBP) x change in trim ≈ -(68/140) x 75.8 ≈ -36.8 cm. Change in forward draft = +(L-LCF/LBP) x change in trim ≈ +(72/140) x 75.8 ≈ +39 cm. Trim calculation at Chief Mate level is a regularly examined practical skill. The MCT1cm (Moment to Change Trim 1cm) is found in the hydrostatic tables for the vessel's displacement — the calculation above uses an approximate GM_L for illustration; in practice, read MCT1cm directly from the vessel's hydrostatic tables at the relevant displacement. Key points: (1) trimming moment direction: weight moved forward → moment creates trim by the head (bow down); weight moved aft → trim by stern; (2) the LCF (centre of flotation) is the pivot point — the trim change produces changes in both draft marks, weighted by the distance from LCF to each mark; (3) a vessel trimming by the head may create propeller emergence (reduced propulsion efficiency), slamming in head seas, and hatch cover stress amidships. At Chief Mate level the examiner will often provide the MCT1cm and LCF values and ask for the calculation — the candidate must work it through methodically.

Question 2

As Chief Mate, you receive a Dangerous Goods Declaration for 12 drums of methyl ethyl ketone peroxide (Class 5.2 — organic peroxide). The manifest states "Type C." Your examiner asks what your responsibilities are before loading.

Accepted Answer

Before loading Class 5.2 organic peroxides: verify the Dangerous Goods Declaration is complete and accurate (UN number, proper shipping name, class, packing group, flashpoint, emergency contact). Check the IMDG Code entry for MEKP Type C — organic peroxides have temperature control requirements (SADT — self-accelerating decomposition temperature) and require controlled temperature stowage. Verify the shipper has provided a Certificate of Analysis confirming temperature control requirements are met. Check segregation against other cargo — Class 5.2 must be segregated from flammable materials. Confirm the ship has the required equipment (temperature monitoring, fire extinguishers of correct type). Inform master and company if any requirements cannot be met. The Chief Mate signs the cargo receipt — this is a legal acknowledgement of receipt in apparent good order. Organic peroxides (Class 5.2) are among the most dangerous IMDG cargoes — they can decompose exothermically and trigger fires or explosions. MEKP (Methyl Ethyl Ketone Peroxide) is used in fibreglass manufacturing and is highly reactive. The IMDG Code Subdivision 5.2 lists organic peroxides by type (A through G) — Type A is prohibited from sea transport; Type B requires temperature control and specific packaging. The SADT (Self-Accelerating Decomposition Temperature) is the minimum temperature at which the substance will decompose in the packaging used — if ambient temperature approaches SADT, cooling must be provided. At Chief Mate level, the examiner expects candidates to know: (a) the special provisions for the specific cargo; (b) the temperature monitoring and emergency cooling requirements; (c) stowage requirements (often "on deck away from living quarters" or "under deck in a cool, well-ventilated space"). Responsibility is shared — the shipper provides the declaration, the Chief Mate verifies it is plausible and meets carriage requirements.

Question 3

As Chief Mate of a 15-year-old Handymax bulk carrier, your examiner asks about the structural hazards specific to bulk carriers and what pre-loading inspections are required.

Accepted Answer

Bulk carrier structural hazards: transverse frames and frames at the lower hopper angles are susceptible to corrosion — section loss reduces capacity to withstand cargo and water pressure; topside tank inner structure (frames, longitudinals) can corrode from condensation; hold bilge systems can become blocked leading to flooding; hatch coaming knees and corners are high-stress areas prone to cracking. Pre-loading inspections required: visual inspection of all cargo hold frames for excessive corrosion, cracks, or deformation; measure any suspect frame section loss against class thickness limits; inspect bilge wells and ensure suctions are clear; test bilge systems before loading; verify hatch cover weathertightness; check hold structural condition report in class records. A "substantiated doubt" of structural deficiency found by PSC can require survey before departure. Bulk carrier structural safety has been a major IMO focus since the catastrophic losses of the 1980s-1990s (Derbyshire, Flare, Melete, Arktea — all total losses with all crew). The Enhanced Survey Programme (ESP) for bulk carriers (IMO Res. A.744(18)) requires detailed close-up surveys and thickness measurements at defined intervals. But between class surveys, the Chief Mate has a duty of care to identify visible deterioration. The IMO Guidelines for Surveys of Aged Bulk Carriers (MSC/Circ.1040) and IACS common structural rules address corrosion margin and allowable section loss. In practice: a frame with visible wastage (deep pitting, section loss, deformation) in a high-stress location (lower bracket area, bilge strake connection) can constitute a class deficiency requiring steel renewal before further loading. The Chief Mate is the primary person on board with technical knowledge to identify these issues — if in doubt, seek a class surveyor before loading heavy ore cargo.