Ships are classed by cargo: the three big groups are container ships, bulk carriers and tankers, subdivided into oil, gas, chemical and product tankers, plus passenger, ro-ro and offshore types. Three main categories: container ships, bulk carriers (grain, ore) and tankers, with multi-purpose ships covering mixed trades. Tanker subdivisions: oil, gas carriers built for LPG/LNG/liquefied chemical gases in bulk, chemical and product carriers, plus juice, wine and integrated-tug-barge types. Dry side: container, bulk carrier, passenger, ro-ro and offshore ships, each with its own structural subdivision. Say it as: what she carries decides her subdivision, midship section, freeboard and fire protection — type first, details after. Surveyor follow-up: what makes a gas carrier different from an oil tanker in construction?

deck fire fighting system on chemical tankers?

Chemical tankers carry a fixed deck foam system sized well above crude-oil practice because chemical fires are hotter and harder to kill. Chemical tankers: foam capacity the largest of entire cargo deck at 2.0 litre/m2/min, or 20 litre/m2/min over the single largest tank. Oil tankers for comparison: 0.6 litre/m2/min over the whole deck or 6.0 litre/m2/min over the largest tank — roughly a third of chemical-tanker figures. System parts: seawater supply pumps, foam-liquid storage, proportioning device and deck distribution with monitors and applicators. It must knock down spill fires, stop unignited spill igniting, and fight fires in ruptured tanks. Surveyor follow-up: why does a chemical tanker need three times the foam rate of a crude carrier?

Boiler water is tested to catch seawater contamination, wrong alkalinity, dissolved oxygen and hardness before they scale, pit or corrode the boiler. pH test: 7.5–14.0 for boiler water, 6.5–10.0 for condensate — warns of acidity/alkalinity drift and sets boiler-compound dosage. Aim boiler pH 10–11. Chloride test: warns of seawater contamination of the feed system and sets blowdown; act if chlorides exceed about 300 ppm. Hydrazine (Amerzine) test: dissolved-oxygen scavenger reserve — prevents oxygen pitting in boiler, steam and condensate lines. Phosphate test: keep 40–60 ppm reserve so any hardness salts entering are neutralised instead of scaling tubes. Surveyor follow-up: chlorides are climbing — what two actions do you take?

Bottom end bearing clearance?

Bottom-end clearance is taken with the crank at BDC: feeler gauge for a quick check, lead wire or plastigauge for an accurate one, against the maker’s limit. Feeler method: turn crank to BDC, insert the feeler between the lower half and the crankpin. Lead-wire method: lay wires circumferentially in the bottom half at three places, torque the cap to full tightening torque, open up and measure the flattened wires. Main bearings are done the same way after removing the upper half, using a bridge gauge with feelers; micrometer beats feeler for accuracy. Excessive clearance means low lube-oil pressure, lost load-carrying capacity, pounding and hammering of the crankshaft — renew shells or reset shims. Surveyor follow-up: lube-oil pressure has fallen on one unit with no leak — which clearance do you suspect and how do you prove it?

Effects of free surface effect?

A slack tank’s liquid runs to the low side as the ship rolls, acting as a virtual rise of G: GM and GZ fall and the roll grows. Mechanism: liquid in a partly-full tank moves across with each heel, so the ship behaves as if her GM were reduced — a virtual (imaginary) loss of GM. Consequences: centre of gravity effectively shifts, metacentric height and righting lever shrink, angle of heel grows, ship can go unstable. Size depends on the free-surface dimensions and the ship’s displacement — wide shallow tanks are the worst. Cures: press tanks full, keep slack tanks to a minimum, subdivide wide tanks; near 90% full, pocketing shrinks the effect. Surveyor follow-up: would you press up a high slack tank or a double-bottom tank first — and why?

Ocean-going ships use slow-speed two-stroke crosshead engines for propulsion and medium-speed four-stroke trunk-piston engines for auxiliaries and smaller vessels. Main propulsion: large slow-speed two-stroke crosshead engines — Sulzer, MAN B&W, Mitsubishi. Auxiliary and medium power: four-stroke trunk-piston engines — Wartsila, Pielstick, Sulzer, MAK. Crosshead engines make much higher power at lower rpm because the crosshead bearing has more room than a gudgeon-pin assembly; trunk engines are shorter, cheaper and suit mass production. Two-stroke piston: crosshead type with piston rod and guides, compression-type rings, more headroom; four-stroke: trunk type with skirt-driven gudgeon pin. Surveyor follow-up: why can’t a trunk-piston engine match a crosshead engine’s power at the same low rpm?

How will you take tappet clearance?

Bar the engine until the roller sits on the cam base circle, feeler-gauge the gap, and reset it with the tappet screw. Rotate the engine until the respective roller is on the base circle of the cam, then measure with a feeler between valve stem and tappet — or between roller and cam after pushing the pushrod up by hand. Exhaust clearance is set slightly larger than inlet because the exhaust valve runs hotter and expands more. Adjust with the threaded tappet on the rocker arm, turning the screw until the specified clearance is obtained. Cross-check: at firing TDC both pushrods are loose (both valves shut); fuel-pump marks coinciding also marks injection beginning. Surveyor follow-up: you set the clearance with the roller on the cam flank instead of the base circle — what happens when she runs?

A gear-pump overhaul is a clearance job: open up, measure casing-to-gear clearance and backlash, renew worn parts and prove the relief valve. Check clearance between casing and gear teeth with a feeler — as it grows, liquid slips back and discharge falls. Check backlash for heat expansion with lead wire or feelers; no backlash means damaged teeth and an overloaded motor. Meshing gear teeth wear with time and fluid abrasiveness, losing efficiency and pumping ability — renew them on condition, not on hope. Remove and pop-test the relief valve at every overhaul; inspect bushes, shafts and seals while open. Surveyor follow-up: discharge pressure is normal but flow has fallen — clearance or relief valve, and how do you decide in five minutes?

Shell expansion plan?

A shell-expansion plan flattens the ship’s 3-D shell plating into one 2-D drawing, measured around the girth so side and bottom appear as a continuous whole. It is the arrangement of the shell plating taken from a 3-D model and drawn in 2-D, with vertical dimensions taken around the girth rather than as direct vertical projection. Side and bottom plating show as one continuous sheet, with plate numbering and strake lettering for reference — strakes lettered outward from the keel, starting at the garboard strake. It also carries openings in shell, deck edges, stringers, girders, bulkheads, stem and stern details, bossings and frame lines. Use it for: finding any plate by number, planning steel renewals, and answering where shell thickness increases (deck, bottom, and midship shear regions). Surveyor follow-up: point at the drawing and name the first strake out from the keel — then the one at the turn of bilge.

General - Construction & Stability | Most Asked Questions

Q: Enclosed space entry?

No one enters until the space is isolated, ventilated, atmosphere-tested and covered by a permit, with an attendant at the entrance and rescue gear ready. Pre-entry: blank off and isolate all connected lines, secure valves against accidental opening, ventilate thoroughly, then test the atmosphere — oxygen about 20.9%, hydrocarbon below 1% LFL, toxics within limit (CO below 25 ppm). Keep continuous ventilation and frequent atmosphere checks running the whole time men are inside, with adequate lighting and rescue/resuscitation gear at the entrance. Team leader confirms hazards, agreed communications, reporting interval and emergency/evacuation drill before anyone goes in. A trained attendant stays at the entrance the whole time and never enters — not even for a rescue — until the responsible officer is told and a relief attendant is posted. Surveyor follow-up: the attendant sees a man collapse inside — what is his exact first action?

General - Construction & Stability — Most Asked Questions