Question 1

Your vessel has a main engine failure at sea in the English Channel. A tug is en route. As Chief Mate, how do you prepare the vessel to receive a tow?

Accepted Answer

RECEIVING A TOW — CHIEF MATE'S PREPARATION: GENERAL: towing at sea requires careful preparation of both vessels. The chief mate manages the preparations on the disabled vessel. BEFORE THE TUG ARRIVES: (1) STABILITY AND TRIM: assess current stability. Ensure adequate stability for the towing operation. If possible, optimise trim for towing (usually even keel or slight stern trim); (2) ANCHOR READINESS: if the vessel is drifting toward danger — anchoring may be the immediate priority before the tug arrives; (3) CONNECT TOWLINE AT THE BOW: prepare the forecastle for towline reception: (a) check anchors are properly secured (not at risk of dropping accidentally); (b) identify the best fairlead for the towline (bow roller or forward hawse pipe); (c) rig a handling line (heaving line or messenger) to receive the tug's towline; (4) TOWING HOOK/BOLLARD: identify the strongest attachment point on the vessel. Towing bollards rated to vessel's displacement × 0.15 (rule of thumb). Towing off anchor cables (if towing hook not rated) — connect towline to the anchor cable and range cable on deck; (5) CHAFE PROTECTION: fit chafing gear (canvas, hose) where the towline passes over fairleads or rails; (6) COMMUNICATIONS: establish VHF communication plan with the tug. Agree channel, hand signals; (7) EMERGENCY RELEASE: agree a release method for the towline in emergency. Can the vessel cut the towline? Capstan to release?; (8) STEERING: if available — maintain ability to steer (any power steering or hand steering available?); (9) ENGINE ROOM STANDBY: monitor towing stresses on hull structure. Towing bollard rating: the towing bollard or bitt must be rated to withstand the towing forces. In heavy weather towing, dynamic loads on the towline can be significantly higher than static towline tension. Towing off the anchor cable: anchors and their cables are designed for high tensile forces — the anchor cable of a large vessel can withstand tensions in the hundreds of tonnes. Connecting the towline to the anchor cable (with the anchor board and cable ranged on deck) provides a very high-rated towing attachment. This is the preferred method on vessels without a purpose-built towing hook. Chafe protection: towline failure at a chafe point is the most common cause of failed tow operations. The towline must be protected wherever it contacts the ship's structure. Heavy canvas wrapped and secured, old rubber hose, or purpose-made chafing gear should be rigged before the towline is tightened. English Channel considerations: the English Channel is a heavily trafficked TSS area. A disabled vessel drifting in the English Channel creates a navigation hazard. Early notification to Dover Coastguard CNIS (VHF 11) of the vessel's situation and position is essential — CNIS can broadcast a MAYDAY relay or a NAVtex broadcast warning other traffic. MAYDAY vs PAN PAN: engine failure at sea in the English Channel — is it a MAYDAY? A MAYDAY requires imminent danger to life. An engine failure with a tug en route and adequate sea room — PAN PAN (urgency) is appropriate. MAYDAY only if imminent danger of grounding or if persons are at risk.

Question 2

As Chief Mate on a chemical tanker, you are planning to load benzene (UN 1114, Class 3, PG I) after carrying methanol. What segregation, tank preparation, and safety measures apply?

Accepted Answer

BENZENE LOADING AFTER METHANOL — CHIEF MATE's PLANNING: CARGO COMPATIBILITY CHECK: (1) Are methanol and benzene compatible for sequence loading? Methanol (Class 3/6.1) and benzene (Class 3) are both flammable — BUT they are not compatible in the sense that residual methanol in a benzene cargo = CONTAMINATION. Check the IBC Code compatibility matrix and the charterer's cargo compatibility requirements; (2) TANK WASHING: tanks previously carrying methanol must be thoroughly washed before benzene loading. Methanol is water-soluble and miscible — water washing followed by recirculation is appropriate. Complete drying is required as water in benzene cargo = haze/contamination; (3) BENZENE PROPERTIES (UN 1114): (a) Class 3, Packing Group I (very high flammability); (b) Boiling point 80°C, flashpoint -11°C (extremely flammable); (c) TOXIC: a human carcinogen (Group 1 IARC). Vapour exposure risk — PPE: SCBA and full chemical protection suit for all operations; (d) Vapour density 2.7 (heavier than air — accumulates in low areas); (4) MARPOL ANNEX II: benzene is Annex II Category X substance (most hazardous). Pre-washing before any discharge — MANDATORY; (5) IBC CODE SPECIAL REQUIREMENTS: benzene requires closed loading, vapour return line (vapour recovery or destruction), enclosed gauging (no open ullaging), and restricted access during loading; (6) SAFETY ZONE: 3-metre exclusion zone around manifold during loading operations. No ignition sources within 30m. IGS may not be required (benzene is non-reactive to inert gas atmospheres) but nitrogen blanket may be required; (7) EMERGENCY: EmS F-E (flammable liquids fire) and S-E (spillage). Benzene as a carcinogen: benzene is classified as a Group 1 carcinogen by IARC (International Agency for Research on Cancer). The IMDG Code and IBC Code impose additional health protection requirements beyond standard Class 3 liquid handling. Exposure limits: the UK COSHH regulations specify a Workplace Exposure Limit (WEL) for benzene of 1 ppm (8-hour TWA). This is extremely low — the vapour pressure of benzene at ambient temperature means significant benzene vapour can be present at open ullage points, manifold areas, and any open sampling. ALL operations involving benzene cargo must use SCBA and appropriate chemical protection. IBC Code Chapter 15 special requirements: Chapter 15 of the IBC Code specifies additional cargo-specific requirements for each chemical. For benzene — these include: (a) vapour emission control; (b) closed operations; (c) emergency shutdown system; (d) health monitoring for crew. MARPOL Annex II Category X: benzene is among the most strictly regulated liquid cargoes under MARPOL Annex II. Discharge into the sea of any benzene-contaminated washwater is absolutely prohibited unless processed through a compliant retention/disposal system. Pre-wash is mandatory before ANY discharge of residues in any sea area. Cross-contamination (option B): loading benzene into a tank with methanol residue creates a contaminated benzene cargo. Methanol is infinitely miscible with benzene — even small traces will reduce benzene purity below specification. Additionally, water from tank washing that is not completely dried creates a benzene/water haze that similarly renders the cargo off-specification.

Question 3

In port, a cargo hold is opened and a strong smell of chlorine is detected. The manifest shows UN 1017 (Chlorine, Class 2.3 Toxic Gas) in the lower hold. Crew members are near the hold. As Chief Mate, what do you do?

Accepted Answer

CHLORINE GAS RELEASE — EMERGENCY RESPONSE: UN 1017, CHLORINE, CLASS 2.3: (a) Extremely toxic gas — IDLH (Immediately Dangerous to Life and Health) 10 ppm; (b) Heavier than air (vapour density 2.5) — accumulates at low levels in holds; (c) Bleach-like odour detectable at 0.5 ppm — if crew can smell it, concentrations may already be dangerous. IMMEDIATE ACTIONS — FIRST 60 SECONDS: (1) SHOUT AND CLEAR: warn all crew in the vicinity to MOVE AWAY UPWIND. Do not send crew into the hold without SCBA; (2) WIND AWARENESS: position crew UPWIND of the hold opening. Chlorine disperses downwind; (3) NO IGNITION SOURCES: chlorine in combination with hydrogen (from bilge gas) could explode — no smoking, no naked flames. However, chlorine itself is not flammable; (4) CALL THE MASTER: immediate notification; (5) SOUND GENERAL ALARM: if the release is significant or risk of spread to accommodation; (6) CLOSE THE HOLD: if it can be done safely from outside without entering — secure the hold to contain the release; (7) EMERGENCY SERVICES: contact port authority and emergency services (shore fire brigade with HazMat team); (8) IMDG EmS: EmS code for UN 1017 is F-C (non-flammable gas fire) and S-U (toxic gas spillage). S-U: keep people away from damaged area. Contact 24-hour emergency advice centre; (9) EMERGENCY CONTACT: the DG manifest must show a 24/7 emergency contact. Call them immediately; (10) DO NOT VENTILATE BY BLOWING AIR INTO HOLD: this could disperse chlorine gas to adjacent areas. Chlorine toxicology: chlorine is one of the most dangerous gases that can be encountered on a cargo vessel. WWI chlorine gas attacks used concentrations above 1,000 ppm — but even at 30 ppm, severe chest pain, vomiting and pulmonary oedema occur. At 430 ppm — death within 30 minutes. Critically: chlorine is HEAVIER than air — it accumulates at the lowest point (bottom of the hold). Crew near the open hatch may not immediately appreciate the concentration at lower levels in the hold. IMDG EmS S-U: the Spillage Schedule for toxic gases (S-U) specifies: "ELIMINATE all ignition sources. STOP leakage only if safe to do so. Move people from danger area upwind. Advise competent authority of potential hazard. Contact chemical experts." "Rag over the face" approach (option C): chlorine at dangerous concentrations is immediately incapacitating. A crew member who enters a hold with chlorine vapour above IDLH using a rag as protection will quickly become incapacitated. This would turn a dangerous goods incident into a rescue situation requiring entry into a toxic atmosphere — putting additional lives at risk. The USCG and MAIB have investigated several cargo incidents where rescue attempts without SCBA resulted in rescuers also becoming casualties. Ventilation with fans (option B): ventilating by blowing air INTO the hold could spread chlorine gas to adjacent spaces, including engine room intakes and accommodation. The correct approach is to CLOSE the hold and control the release, allowing emergency services with HazMat equipment to handle decontamination. Detection threshold vs danger threshold: the detection odour threshold for chlorine is 0.5 ppm. This is BELOW occupational exposure limits (1 ppm ceiling under COSHH). Detection does not mean safe — it means dangerous concentrations may be nearby.