Ship Structure - Bulkheads & Tanks — Most Asked Questions
39 questions asked about ship structure - bulkheads & tanks across the General and Fn 3 papers, heaviest first.
Learn the system first
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1 Collision bulkhead regulations
Also asked: “Corrugated bulkhead regulation”, “Collision bk regulation”
Answer
The collision bulkhead is the foremost watertight wall: far enough aft to survive a bow impact, far enough forward to keep flooding small.
- Position per SOLAS: not less than 1/20 of ship length or 10 m from the fore perpendicular, whichever is less — and not more than 0.08L or the greater formula limit aft.
- No doors, manholes, ventilation ducts or access openings in it — only tightly controlled pipe penetrations with screw-down valves operable from deck.
- Watertight from keel to the required deck, so a crushed bow floods one compartment, not the ship.
- Too far forward and any impact breaches it at once; too far aft and the flooded bow trims her by the head beyond recovery.
Surveyor follow-up: a spool piece through the collision bulkhead with valves both sides — allowed or not?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
2 Class A division Bulkhead as per SOLAS
Answer
Class A is steel that holds smoke and flame a full hour with insulation keeping the cold side cool.
- Built of steel or equivalent, stiffened and made continuous with shell, decks and structural bulkheads.
- Stops smoke and flame through the one-hour standard fire test.
- Insulated with approved non-combustible material so the unexposed face rises under 140 degrees average.
- Graded A-60 down to A-0 by insulation minutes — 60, 30, 15 or none — structure still holds the hour.
Surveyor follow-up: engine-room casing door wedged open — which division has just been defeated?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
3 Short notes on class A, B , C bulkheads. Regulation regarding them
Also asked: “Short notes on class A, B and C bulk heads. Regulation regarding bulk head”
Answer
A holds an hour in steel, B holds half an hour in non-combustible board, C just stops flame — insulation decides the grade.
- Class A: steel, smoke-and-flame tight for one hour, insulated A-60 to A-0 against heat passage.
- Class B: non-combustible board stopping flame for 30 minutes with limited heat rise — veneers allowed if they pass.
- Class C: approved non-combustible material stopping flame with no insulation rating.
- Fit follows the fire plan: machinery casings and stair trunks in A, cabin panels in B, furniture and fittings in C.
Surveyor follow-up: cabin lining marked B-15 — where may it go, and where is it forbidden?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
4 Why cargo hold ventilation is required
Answer
Hold ventilation fights sweat, gas, smell and heat: dry air in, moist poisoned air out, by the dew-point rule.
- Ship sweat condenses on cold steel when warm moist hold air meets cold structure on a hot-to-cold passage.
- Cargo sweat wets the stow itself as hygroscopic goods breathe moisture and heat — ventilation breaks the cycle.
- Fresh air clears poisonous gases, old-cargo smells and heat given off by plant products and chemicals.
- Ventilate by dew point: compare inside and outside air, open up only when outside air dries the hold, not wets it.
Surveyor follow-up: steel sweat dripping over bagged grain on a northbound leg — ventilate or shut down, and what reading decides?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
5 Class B division Bulkhead as per SOLAS ‘‘B'' class divisions are those divisions formed by bulkheads, decks, ceilings or linings which comply with the following criteria
Also asked: “Class B division Bulkhead as per SOLAS ‘‘B’’ class divisions are those divisions formed by bulkheads, decks, ceilings or linings which comply with the following criteria”
Answer
Class B stops flame half an hour in non-combustible board with graded insulation: B-15 holds heat 15 minutes, B-0 none.
- Built of approved non-combustible board stopping flame through the 30-minute standard test.
- Cold-face rise capped near 140 average and 225 spot within the graded minutes.
- Grades B-15 for fifteen insulated minutes and B-0 for flame only; veneers allowed if they pass.
- Cabins, corridors and linings live in B; machinery casings and stairs demand A above it.
Surveyor follow-up: cabin lining marked B-15 — where may it go, and where is it forbidden?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
6 Detector in cargo hold
Answer
Hold detectors watch smoke where crew rarely go: smoke cover in service-adjacent spaces with bridge alarms that name the zone.
- Smoke detection across service spaces, control stations and accommodation including corridors, stairs and escapes.
- Cabins alarm inside the cabin as well as at the panel; bathrooms, galleys and void risks stay exempt by rule.
- Alarms sound distinct in tone and light from every non-fire system on the bridge and with the duty engineer.
- Unmanned bridge repeats where a responsible crew member keeps watch — silence is never the design.
Surveyor follow-up: detector in the galley store alarming on toast — relocate, replace type or accept, and why?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
7 ISM Fire in cargo hold?
Answer
Fight a hold fire contained, not entered: raise, restrict, cool boundaries and extinguish from outside the zone.
- Raise the alarm and muster with the hold sealed — never assume cooking smoke over cargo smoulder.
- Restrict on six sides including above and below before committing a team to the door.
- Boundary-cool with skilful venting onto cool air so entry, if ordered, rides a safe stream.
- All hands know the appliances from realistic light-and-dark drills — the muster list runs the fight.
Surveyor follow-up: smoke from a sealed hold with Boundary cooling on — open up or hold shut, and who decides?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
8 Collission bulkhead position and its purpose
Answer
The collision bulkhead seals the bow: not too far forward to crush at once, not too far aft to flood deep.
- Foremost bulkhead in the ship bounding the forepeak against bow damage.
- Positioned by rule between minimum and maximum distances from the forward perpendicular by length.
- No doors, manholes, ducts or openings pierce it except tightly controlled piped penetrations.
- Purpose is one flooded bow compartment, never progressive flooding aft — trim survivable, stability held.
Surveyor follow-up: pipe through the collision bulkhead with valves both sides — allowed or not?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
9 Corrugated bulkhead increases which strength specifically of b/h
Answer
Corrugations replace stiffeners with folded plate strength: deep folds carry vertical load and share hull-girder stress.
- Deep corrugations serve as built-in stiffeners, shedding brackets and saving framing weight.
- Vertical folds on transverse bulkheads support bottom structure and shed cargo cleanly.
- Horizontal folds on longitudinal bulkheads join hull-girder bending where vertical folds would waste plate.
- Fracture watch sits on horizontal transverse corrugations — equalise segment moments with spaced girders.
Surveyor follow-up: vertical or horizontal corrugations on a transverse bulkhead — which one, and why?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
10 Roro ship bulkhead system
Answer
Ro-ro subdivision trades bulkheads for decks: long clear lanes with moveable ramps under damage-stability index control.
- Degree of subdivision set by the required index R from length and persons aboard.
- Cargo ships over 80–100 m and all passenger ships prove damage stability by calculation, not blanket rules.
- Ramps, doors and moveable decks count as boundaries with weathertight and fire discipline to match.
- Administrations accept equivalents only at equal safety with particulars filed to the organisation.
Surveyor follow-up: stern door left open in port with the ship upright — subdivision intact or defeated?
Full theory: SOLAS Chapter II-1 — Construction: Subdivision, Stability, Machinery & Electrical -
11 When sump tank is empty, interior cleaned and examined
Also asked: “Clean the interior of the sump tank and carefully examine”
Answer
Empty sumps get cleaned and read like survey spaces: sludge out, steel read, suction proved before refilling.
- Drain and ventilate with gas checks before entry — sludge gas kills faster than rust.
- Clean baffles, suctions and strums with scale and sediment landed, not pumped overboard.
- Read plating, welds and coatings for pitting, cracking and wastage with sounding backup.
- Prove bilge suctions and alarms on refill — a clean sump with dead suctions still floods.
Surveyor follow-up: sump clean but sounding shows water where sludge stood — leak, condensation or wash-down, and what proves it?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
12 Bulkhead a60 what does it means
Answer
A-60 is a steel fire division holding one hour: no smoke or flame passage with the cold face kept below 140°C average.
- Steel or equivalent stiffened division blocking smoke and flame for the full 60 minutes.
- Approved non-combustible insulation limits the unexposed face to 140°C average and 180°C at any joint.
- Siblings derate by time: A-30 holds 30 minutes, A-15 holds 15, A-0 blocks flame with no insulation rating.
- Penetrations, dampers and doors inherit the rating — one uninsulated trunk through it fails the whole bulkhead.
Surveyor follow-up: A-60 bulkhead with a new cable transit unsealed and a vent damper pinned open — still A-60 or failed?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
13 Cargo hold fire detection system detecting system?
Answer
Holds earn sample-extraction smoke detection: accumulators overhead every 12 metres, tested without renewing parts, on standby power.
- At least one smoke accumulator per enclosed hold, spaced so no overhead deck point sits beyond 12 metres horizontally.
- Fans draw air continuously to the detector cabinet with alarms before smoke stratifies out of reach.
- Built against false trips from voltage swings, humidity, vibration and corrosion with flammable-mixture ignition excluded.
- Testable to normal surveillance without part renewal, with alternative power when mains fail.
Surveyor follow-up: one accumulator isolated for a reefer parcel with the rest live — compliant isolation or impaired system?
Full theory: Ship Fire Detectors: Heat, Smoke & Flame Types -
14 Type of tank
Answer
Name tanks by place and duty: double-bottom, wing, deep, peak and service tanks each earn their fittings.
- Double-bottom tanks ride the tank top for ballast, fuel or fresh water with sounding and air pipes paired.
- Wing and side tanks use the shell frame space for ballast with topside and hopper slopes in bulk carriers.
- Deep tanks rise through decks for part cargoes or bunkers with full panting and wash arrangements.
- Peaks close the ends — forepeak for collision and ballast, aftpeak round the stern gear — plus service, settling and sludge tanks in the engine room.
Surveyor follow-up: fuel found in a tank marked ballast with fittings unchanged — sounding, venting or pollution risk fails first?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
15 Types of Bulkhead?
Answer
Bulkheads divide by plane and build: transverse or longitudinal, flat stiffened or corrugated without stiffeners.
- Transverse bulkheads split holds and tanks across the ship; longitudinal ones run fore-aft sharing hull-girder stress.
- Flat plating needs stiffeners and deep bracketed webs to carry pressure and buckling.
- Corrugated swedged plating carries stiffness in its folds — no ordinary stiffeners, occasional deep webs across.
- Corrugation direction matters: transverse bulkheads take vertical or horizontal folds, longitudinal ones only horizontal for girder strength.
Surveyor follow-up: longitudinal corrugated bulkhead with vertical folds in a tanker — stiff, compliant or wrong direction?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
16 Avoid reaching over the spinning chuck. For filing operations, hold the tang end of the file
Answer
Hands stay away from the work: never over a spinning chuck, and when filing, hold the tang and pull towards you.
- Never reach over a rotating chuck, drill or workpiece — a glove, sleeve or loose cuff is enough to take a hand in.
- For filing, hold the tang end with one hand and push the file away from you, so a slip throws it away from the body.
- Chuck keys are removed immediately after use; a key left in the chuck becomes a projectile the moment the machine runs.
- And loose clothing, rings and watches come off before the guard goes back — the machine is not the problem, the rotation is.
Surveyor follow-up: hand filing a curved plate at the deckhead with no goggles — what are the two findings, and which hurts?
Full theory: Shipbuilding Materials, Welding and Weld Defects -
17 Cargo hold bottom plate regulation and class
Answer
The hold bottom is classed structure: scantlings from the rules, then measured and gauged on the ILLC survey like any other plating.
- Hold bottom plating follows the class scantlings for the ship’s type, strengthened in the pounding region forward.
- ILLC requires thickness measurement of each bottom plate with transverse sections, and the results recorded.
- Wastage, pitting, deformation and coating breakdown are all findings, and the plate is renewed or accepted with a stated margin.
- Where a cargo causes damage, the class accepts the strength calculation on the remaining thickness, not on the original.
Surveyor follow-up: hold bottom at minimum allowable thickness with pitting spreading — accept, renew, or restrict the cargo?
Full theory: Ship Classification, Surveys and Drydocking -
18 Cargo hold fire safety and which detector is used in cargo hold
Answer
Holds are watched by smoke detection and, where required, water-level alarms — a fire in a hold is found by the detectors, not the eye.
- Sample-extraction smoke detection with accumulators overhead, spaced so no deck area is more than 12 m from one.
- Rate-of-rise and fixed-temperature heat detectors cover holds where the fire is fast and the smoke layer sits high.
- Bulk carriers add water-level detectors aft in every hold with two-stage audible and visual alarms.
- Each hold also has the fixed system and the boundary ready — detection finds it, the system puts it out.
Surveyor follow-up: hold with a smoke accumulator beyond 12 m of any overhead deck point — does that pass or fail?
Full theory: Ship Fire Detectors: Heat, Smoke & Flame Types -
19 Cargo hold regulation
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20 Changing light of imdg cargo hold
Answer
You change the lighting of a dangerous-goods hold by proving the space and switching to the safe circuit, never by a torch alone.
- IMDG cargo creates a hazardous atmosphere, so only equipment certified for the zone may be used inside the hold.
- Switching on or changing the lighting is a hot job: isolate, prove gas-free, and use flameproof or intrinsically safe apparatus.
- Any change of lighting arrangement is recorded, and the circuit is proved before cargo is stowed under it.
- The real question is the equipment: a torch or a non-certified lamp in an IMDG hold is the breach, not the change.
Surveyor follow-up: hold lighting changed with a hand torch used inside — is the torch, the zone or the permit the finding?
Full theory: SOLAS Chapter VII — Carriage of Dangerous Goods & IMDG Code -
21 Co2 release in cargo hold and detection in container.vessel?
Answer
In a container ship, detection is in the bay and the hold; the fixed system is a deluge or high-pressure water mist, and CO₂ is not the answer.
- Smoke detection in the bay and hold finds the fire, with detectors positioned to the smoke layer and the cargo.
- A container fire is fought with water — a high-pressure deluge or mist — because the cargo will not let a gas blanket build.
- CO₂ and clean agent systems are not fitted for container holds for exactly that reason: the hold is not gas-tight.
- The arrangement is detect, alarm, isolate the bay, seal the holds and deluge — with the boundary cooling the accommodation.
Surveyor follow-up: bay fire with the holds sealed and the deluge not started — what is the first action, and who starts it?
Full theory: Ship Fire Detectors: Heat, Smoke & Flame Types -
22 Coffer dam regulation
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23 Collison bulkhead regulation
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24 Criteria of speed of resque boat Article 2 of MLC Difference between clean blallast tank and segregated ballast tank ISPS
Answer
Two rules at once: the rescue boat speed criterion, and the difference between clean and segregated ballast.
- A rescue boat must manoeuvre at at least 6 knots and hold that speed for at least 4 hours, towing a raft at 2 knots.
- Clean ballast is ballast so cleaned since oil was last carried that it would leave no visible trace on calm water.
- Where the discharge goes through an approved monitoring and control system, 15 ppm is determinative even with visible traces.
- Segregated ballast is carried in tanks separate from the oil tanks, so the two cannot be contaminated by contact at all.
Surveyor follow-up: 15 ppm proved on a tank that shares a pipeline with the oil tanks — is it clean or segregated?
Full theory: MARPOL Annex I — Prevention of Pollution by Oil -
25 Diff between fo tank vent and ballast tank vent
Answer
The difference is what the vent has to contain: a fuel oil vent must not let vapour out, a ballast vent only must not let water in.
- A fuel oil tank vent is flameproof, screened and led to a safe height, because the vapour leaving it is flammable.
- It also carries a P/V valve, and for oil tanks the vent is led to open deck where a leak endangers nobody.
- A ballast tank vent is a plain air pipe with a hood — the only hazard there is water getting back in.
- So the answer is vapour containment against water containment — and that is why the two are never the same fitting.
Surveyor follow-up: fuel oil tank vent found with an open mushroom like a ballast vent — which hazard is now unguarded?
Full theory: Ship Pipelines — Seawater, Bilge, Ballast & Fuel Systems -
26 Ff system in cargo hold
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27 Forward collision bulkhead requirement
Answer
The collision bulkhead is a strong watertight forward boundary, set by rule between minimum and maximum distances aft of the stem.
- It is the foremost bulkhead, and its scantlings are heavier than ordinary bulkheads because the forepeak may flood underway.
- Positioned by rule: for ships under 200 m, 5% to 8% of length aft of the forward perpendicular; above 200 m, not less than 10 m and not more than 5%.
- It must be watertight and strong enough to withstand the impact of proceeding with the forepeak flooded.
- Only limited pipes pass through it, each with a valve operable from above the bulkhead deck — which is the rule the surveyor quotes.
Surveyor follow-up: collision bulkhead found with three pipes below deck and no valves — which regulation is broken, and how?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
28 How ur going to know temp in hold
Answer
Hold temperature is read, not assumed: remote sensors in the cargo with a read-out, and a hand check on entry.
- Bulk cargo tanks usually have provision for temperature control of the cargo, which starts with a thermometer in the tank.
- Sensors are placed in the cargo at several levels and positions, wired to a read-out the officer can check from the deck.
- On entry the temperature is confirmed by a hand thermometer at the working level, because a remote sensor can have drifted.
- Log it each watch — the temperature record is the evidence that the cargo was carried in condition.
Surveyor follow-up: hold logged at 4°C with the sensor reading 9°C — the instrument, the cargo or the record?
Full theory: SOLAS Chapter XII — Additional Safety Measures for Bulk Carriers -
29 Lng tank material
Also asked: “Tanker ship tank material”
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30 Oil in cascade tank. Action to be taken
Also asked: “Oil in boiler cascade tank.Action to be taken”
Answer
Oil in the cascade tank means the purifier is overflowing: find the cause, stop the overflow, and get the oil out of the tank.
- Check the parameters that cause an overflow — the gravity disc size, the throughput, and the oil temperature.
- Check the operating water level in the tank, and whether sealing water is present in the purifier.
- Check the bowl is closed properly and the seal ring is not damaged, since both pass oil to the wrong place.
- Then drain the cascade tank to a suitable receptacle, restore the seal, and restart on a reduced feed until it is proved.
Surveyor follow-up: cascade tank with oil in it and the disc proven correct — is it the seal ring, the throughput or the feed temperature?
Full theory: Purifier Maintenance: Cleaning, Inspection & Overhaul -
31 Req of collision bulkhead
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32 Safeties of tank cleaning room
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33 Tank material and speciality about this material?
Answer
Tanks are mild or higher-tensile steel for strength, stainless for corrosive cargoes — and the material chosen sets the whole coating system.
- Mild steel Grade B, D and E is used for the heavier plating of main hull strength members where the stresses are greatest.
- Grade E is required over the midship region of very large ships and is associated with the crack-arrester strake.
- Higher tensile steels are used on decks and bottom plating to cut weight where high strength is needed in thinner plate.
- Stainless grades, especially the 316 and low-carbon 3XXL types, resist sulphurous acid, flowing sea water and corrosive cargoes.
Surveyor follow-up: cargo tank specified in 304 stainless for sulphuric cargo — is the grade right, and what welds will it need?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire -
34 Tank structure and how is it different from others?
Answer
Tank structure depends on what the tank carries: prismatic for ordinary cargo, corrugated or membrane type for gas and low temperature.
- Tank structure may be of prismatic form or of corrugated construction, depending on the cargo and the temperature.
- Prismatic tanks are ordinary welded steel boxes carrying liquid cargo at ambient temperature.
- Corrugated or independent type tanks are used for gas carriers, where the design keeps the low-temperature liquid or vapour off the steel.
- That last point is the whole difference: cryogenic cargo can make steel brittle and fracture, so a secondary barrier is designed in.
Surveyor follow-up: gas carrier tank described as a plain prismatic box — what is missing, and what happens to the steel?
Full theory: Ship Types, Hull Form and the Parts of a Ship -
35 Tell me about speciality of vlec ( i answered tank structure gtt membrane type
Answer
A VLCC is specialised by its size: the largest tanks, the largest foam and fire main, and an inert gas system for the cargo spaces.
- Tank structure is prismatic with a corrugated bulkhead arrangement and heavy scantlings for the size and the draft.
- The cargo system is built around the inert gas plant, deck foam, and the largest fire main and hydrant layout afloat.
- Loading is by shore loading arms or hoses at manifold, with the oil heating, stripping and tank cleaning the operation that defines her.
- The speciality is the scale: everything — tank size, foam, pumps, mooring and the structural strength — is sized for 200 000 dwt and beyond.
Surveyor follow-up: VLCC described with a membrane-type tank — is that a gas carrier structure, and what fails first?
Full theory: Ship Types, Hull Form and the Parts of a Ship -
36 Temperature sensor how many and where in tank
Answer
Sensors are placed in the cargo, not on the tank: several levels and positions, with a read-out the officer can check.
- A temperature element in the cargo at several heights gives the profile, not just a surface reading.
- One near the top and one near the bottom is the minimum that catches a hot layer over a cool one.
- Where the cargo permits, sensors are placed away from the tank wall and away from the heating or cooling coils.
- The readings are logged each watch, and a hand thermometer confirms the remote reading on entry.
Surveyor follow-up: hold sensor reading steady while a hand check 5°C different — which is the one the surveyor trusts?
Full theory: SOLAS Chapter XII — Additional Safety Measures for Bulk Carriers -
37 What procedure u will follow before entering fuel tank (proper procedure
Answer
Fuel tanks are entered like any enclosed space, and worse: gas-free, certified, permitted, ventilated and attended.
- Gas freeing is essential before entering an empty tank — a gas free certificate and a tank entry permit are the first two documents.
- Manhole doors are opened for at least 24 hours before entry, then forced ventilation is run through the manhole by blower fan.
- Test the atmosphere with a Davy safety lamp — a clear flame means no explosive or fatal gas — and again with instruments.
- Enter with continuous ventilation, a competent person watching at the entrance, and a spark-proof torch; naked light and smoking are banned.
Surveyor follow-up: fuel tank opened for 2 hours with a permit signed — which of the 24 hours, the test or the attendant is missing?
Full theory: Permits to Work: Enclosed Space Entry Criteria & Precautions -
38 Why header tank
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39 what is collision bulkhead
Answer
The collision bulkhead closes the bow: watertight, strongly built, and positioned so a forward impact floods only the forepeak.
- It separates the forepeak from the rest of the ship so bow damage does not flood compartments behind it.
- Positioned by rule between set limits aft of the forward perpendicular, set by ship length.
- Scantlings are heavier than ordinary bulkheads because the forepeak may flood with the ship still underway.
- Only a limited number of pipes pass through it below the bulkhead deck, each with a valve operable from above.
Surveyor follow-up: collision bulkhead found with three pipes passing below deck — which rule, and what closes the third?
Full theory: Ship Bulkheads: Watertight, Corrugated and Fire
Source: 123 written papers and surveyor oral banks, 24,613 entries, merged into 17,210 topics. Ticks are stored on this device only.