Engine Room - General — Most Asked Questions
57 questions asked about engine room - general across the Fn 4b and Fn 6 papers, heaviest first.
Learn the system first
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1 how remove broken stud
Also asked: “How to remove a broken bolt or stud from a given location”, “How to remove a broken stud, which is stuck inside?”
Answer
Broken studs come out by grip, drill or weld: extractor first, left-hand tap second, welded nut when nothing else bites.
- Soak with penetrating oil and heat the surround, never the stud alone, then try the extractor.
- Drill true down the centre and cut a left-hand thread with an anticlockwise tap that tightens itself out.
- With no purchase left, weld a nut or bar onto the stump and turn it out with a spanner.
- Last resort is metal disintegration or drilling oversize and re-tapping — measure twice, drill once.
Surveyor follow-up: extractor snaps inside the stud — drill through it or spark-erode it, and why?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
2 what overhauling u have done onboard ??
Also asked: “What overhaul u have done onboard,”, “What major overhaul u did onboard”, “What all major repairs you have done on board”
Answer
Answer overhauls as job cards: what, why, readings, parts and tests — surveyors promote stories with numbers.
- Name the machine and the trigger: hours, survey, breakdown or parameter drift.
- Quote readings before and after — clearances, pressures, temperatures and timing.
- List parts renewed, clearances set and torques used, with maker limits beside each.
- Close with tests run and results: trial readings, alarms proved and log entries made.
Surveyor follow-up: pick your biggest overhaul and give me three numbers from it.
Full theory: Engine Watchkeeping — Handover, Rounds & Work Safety -
3 Types of scavenging?
Answer
Scavenging sweeps exhaust with fresh air three ways: loop over the crown, cross under the cover, uniflow straight up.
- Loop: air loops over the piston crown and out ports on the same liner side above the scavenge ports.
- Cross: air rises one side, sweeps under the cover and falls out ports on the far side.
- Uniflow: air drives straight up the bore and out through head ports or valves — the modern large-engine choice.
- Sketch all three with arrows: ports, cover and valves decide which type the engine breathes.
Surveyor follow-up: your engine loop, cross or uniflow — point at the ports and prove it.
Full theory: Marine Turbochargers: Aerodynamics, Bearings, Washing & Surge Mitigation -
4 gauge glass blowdown
Also asked: “boiler guage glass blowdown”
Answer
Blow the glass to prove both legs: steam jet first, water jet second, then refill and watch the level settle true.
- Shut steam and water cocks, open the drain, then crack steam — a strong jet proves the steam leg clear.
- Shut steam, open water — a strong jet proves the water leg clear.
- Shut water and drain, reopen water so the glass fills high, then open steam and let the level settle.
- No water after blowing means no water in the boiler: shut down at once, ease pressure, never feed a hot empty boiler.
Surveyor follow-up: level sits high and lazy after blow-through — which leg is choked?
Full theory: Normal Operation, Load Control, and Watchkeeping -
5 why hp cut out
Answer
High-pressure cutout guards the compressor: over-pressure on discharge trips it, hand reset restarts it.
- Bellows between discharge and condenser feel the pressure against a spring set by the adjusting screw.
- Past the set discharge pressure the switch arm drops and stops the compressor before joints part.
- Low-pressure and oil-differential switches back it up — LP near 1 bar, oil differential near 1.2 bar, both hand reset.
- After any trip find the cause — fouled condenser, overcharge, blocked water — then reset deliberately.
Surveyor follow-up: HP trips repeatedly with the condenser clean — overcharge, air or water flow, and what gauge proves it?
Full theory: Marine Central Cooling Water System (HT / LT / SW) -
6 for each of the following describe the effect of dirty or restricted
Answer
Dirt throttles every circuit the same way: pressure drops, temperatures climb, protection trips — name the medium, then the effect.
- Dirty air filters drop suction pressure and delivery temperature with cooler manifold air, not hotter.
- Restricted cooling cuts flow and lifts outlet temperatures until high-temperature alarms and trips act.
- Choked fuel filters starve injection with falling pressure, smoke and lost power.
- Fouled lube strainers drop bearing pressure toward the trip while temperatures climb together.
Surveyor follow-up: delivery pressure down with suction pressure also down — filter, cooler or pump, and what proves it?
Full theory: Bilge, Ballast & Fire Main System — Interactive One-Line Diagram -
7 Air, pressure low on
Also asked: “Air pressure low &.so compression pressure low am i”
Answer
Low air with low compression means the cylinders starve together: turbocharger, rings, liner and cooler in that order.
- Fouled turbocharger and clogged scavenge ports cut delivery pressure to every unit at once.
- Broken rings leaking past compression bleed charge mass and pressure together.
- Worn liners and leaking coolers join the same story with rising exhaust and falling power.
- Prove with scavenge pressure against trial figures, then compression diagrams per unit before opening.
Surveyor follow-up: one unit low with the rest normal — common air or that cylinder, and what diagram proves it?
Full theory: Starting the Engine — Air Start Valve, Distributor and the Four Interlocks -
8 How the indicator power of an engine can be measured using indicator instrument, give the procedure with simple sketch of instrument used
Answer
Indicate power by diagram area: blow through the cock, hook the drum, draw power, compression and draw cards, planimeter the area.
- Prove the instrument first — piston drop-tested, drum free, pencil light, cock blown clear two or three firing strokes.
- Fit the rated spring for expected peak pressure and draw power cards per cylinder without overheating the instrument.
- Cut fuel for the compression line on a clear drum spot, then draw, compression and light-spring cards complete the set.
- Measure area by planimeter for indicated power per unit; clean, grease hot and log every card.
Surveyor follow-up: power card area small with compression normal — fuel, timing or load, and what proves it?
Full theory: Indicator Diagrams, Power Balancing & Engine Performance -
9 Open the indicator cock
Answer
Open indicator cocks to blow soot before diagrams and to vent before starting: two or three firing strokes clear, then shut for the card.
- Before diagrams blow each cock firing strokes to clear soot and oil that would choke the pencil.
- Before starting crack cocks to prove turning ease and vent water that would hydraulic-lock the head.
- Leaking cocks bleed compression — tighten and reseat at the first hiss with the unit running.
- Shut fully for power cards; a half-open cock draws a lying diagram.
Surveyor follow-up: one cock blows water on turning gear — rain, jacket leak or cooler leak, and do you start?
Full theory: Indicator Diagrams, Power Balancing & Engine Performance -
10 Since corrosion may happen on the part above the upper bearing
Answer
The shaft above the top bush corrodes where seals weep and air meets oil: bronze liners, glands and drains guard it.
- Shrunk bronze liners with rubber seals stand between steel shaft and seawater at the sternbush.
- Worn bearings vibrate and whirl, rewooded late with sediment and damaged propellers shortening life to months.
- Radial face seals back the liner with drain cocks proving leaks — water out means seals failing inward.
- Pressurise past outside head on light drafts to watch for oil globes betraying the outer seal.
Surveyor follow-up: drain cock runs water with oil pressure normal — seals, liner or bearing, and what first?
Full theory: Engine Bearings — Renewal, Crosshead to Thrust Block -
11 What is meant by waste heat recovery for diesel plant? How the total efficiency can be increased?
Answer
Waste heat already paid for works twice: turbochargers eat exhaust energy while boilers and economisers bank the rest.
- Turbocharger turbines recover exhaust heat for scavenge air — the engine breathes on its own waste.
- Exhaust boilers and economisers raise steam from gas that would otherwise leave the funnel.
- Sharper turbo efficiency cuts fuel directly and lets later exhaust valves harvest longer expansion.
- Roughly half the fuel’s energy leaves as heat — every recovered point trims specific consumption.
Surveyor follow-up: fuel unchanged with new turbochargers — where did the efficiency go, and what number proves it?
Full theory: Steam and Condensate System — Interactive One-Line Diagram -
12 show the safeties incorporated in starting the slow speed engine aided by a sketch and brief explanation of safety elements
Answer
Sketch receiver to cylinder valves with every guard on the path: non-returns, discs, traps, reliefs, drains and interlocks.
- Non-return valves stop explosions travelling back to receivers; bursting discs burst past set pressure.
- Flame traps quench blowback from leaking cylinder valves; relief valves lift on the manifold and heads.
- Automatic drains and thermal bands watch moisture and heat on branch pipes.
- Interlocks gate the start: telegraph, low oil pressure and turning-gear engagement all proved before air admits.
Surveyor follow-up: draw the air path and point at the first guard a blowback meets — trap, disc or non-return?
Full theory: Marine Compressed Air & Main Engine Starting Air System -
13 How to extract broken bolts
Also asked: “How to remove broken bolt?”, “Broken bolt how to take out”
Answer
Broken bolts come out by grip, drill or weld: left-hand extractor first, welded nut when nothing bites.
- Soak with penetrating oil and heat the surround, never the stud alone, then try the extractor.
- Drill true down the centre and cut left-hand thread with an anticlockwise tap that walks itself out.
- With no purchase left, weld a nut or bar onto the stump and turn it out with a spanner.
- Last resort is disintegration or oversize drilling with re-tap — measure twice, drill once.
Surveyor follow-up: extractor snaps inside the stud — drill through it or spark-erode it, and why?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
14 IHP and BHP?
Answer
Indicated power is born in the cylinder, brake power reaches the shaft — friction eats the difference.
- IHP from diagram area times speed and cylinder constant, torsionmeter-free.
- BHP from shaft torque times speed with the torsionmeter on the line.
- Friction power is the gap between them — rings, bearings, pumps and blowers all dine on it.
- Brake specific consumption always exceeds indicated, widening as load falls toward idle.
Surveyor follow-up: BHP steady with IHP climbing — friction, load or measurement, and what proves it?
Full theory: Indicator Diagrams, Power Balancing & Engine Performance -
15 Power card and draw card details
Answer
Power cards phase with firing for mean pressure; draw cards shift 90 degrees to expose injection and compression.
- Power cards plot pressure against volume in phase — planimeter area gives mean indicated pressure and afterburning shows.
- Draw cards rotate the drum 90 degrees out so injection point, cut-off and compression pressure stand clear.
- Compression cards draw the no-fuel line for timing checks on the same paper.
- Take all three without overheating the instrument, then clean, grease hot and log every card.
Surveyor follow-up: power area small with draw card normal — fuel, timing or load, and what proves it?
Full theory: Indicator Diagrams, Power Balancing & Engine Performance -
16 Types of corrosion
Also asked: “Different types of corrosion? Caustic embrittlement?”
Answer
Corrosion splits galvanic, pitting, crevice and caustic: dissimilar metals, chloride pits, hidden gaps and hot alkali each eat steel.
- Galvanic where unlike metals meet salt water — the less noble wastes faster with distance in the series.
- Pitting drives deep local holes in hull, tanks and ballast spaces under deposits.
- Crevice attacks hidden laps and joints where oxygen starves beside open steel.
- Caustic embrittlement cracks stressed boiler steel in hot alkali — treatment and blowdown guard it.
Surveyor follow-up: pits under intact paint with anodes wasted — galvanic, pitting or crevice, and what do you renew?
Full theory: Marine Materials, Metallurgy & Mechanical Testing -
17 What is scavenge efficiency
Also asked: “Scavenge efficiency? Wat is efficiency? Wat is output and input efficiency?”
Answer
Scavenge efficiency is fresh air kept over air delivered: retained charge divided by swept-plus-delivered air at the ports.
- Delivered air leaves the blower; retained air stays trapped after ports close — the ratio is the efficiency.
- Port timing, cooler density and exhaust back-pressure set how much fresh charge survives.
- Low efficiency shows as hot exhaust, smoke and lost power on the same fuel.
- Prove by scavenge pressure and temperature against trials before blaming fuel or timing.
Surveyor follow-up: efficiency down with delivery pressure normal — ports, timing or back-pressure, and what proves it?
Full theory: Marine Turbochargers: Aerodynamics, Bearings, Washing & Surge Mitigation -
18 ref hp cutout reason
Also asked: “Reefer hp cutout reasons”, “Refer HP cutout reasons”
Answer
Refer HP cutout trips on high discharge pressure and stays tripped: overcharge, air, fouled condenser or dead water flow.
- Discharge past the set limit opens the bellows switch and stops the compressor without auto reset.
- Common drivers are overcharge, non-condensables, scaled condenser and failed cooling water.
- Low-pressure and oil-differential switches back it up near 1 bar and 1.2 bar differential, both hand reset.
- Find the cause on gauges before resetting — a reset without a cause buys a second trip.
Surveyor follow-up: HP trips with the condenser clean and charge correct — air, water or switch, and what gauge proves it?
Full theory: The Refrigeration Compressor -
19 Magnetic Particle testing
Also asked: “Magnetic particle testingMagnetic particle testing is a method used to”
Answer
Magnetic-particle testing finds surface cracks in steel: magnetise, dust with iron, and read the powder lines.
- Pass current through the plate so the steel magnetises and flaws form pole pairs at the crack.
- Dust dry or fluorescent particles that pile along the leakage field marking length and direction.
- Highly directional — magnetise across the suspected crack, then repeat at right angles to catch the shy ones.
- Prove bedplate welds, girder joints and bearing-pocket radii where cracking starts under overload and loose bolts.
Surveyor follow-up: indication on a transverse girder weld with the flux along the weld — crack or missed direction, and what next?
Full theory: Marine Materials, Metallurgy & Mechanical Testing -
20 Open crankcase door
Answer
Crankcase doors stay shut on hot oil mist: stop, cool, ventilate and wait twenty minutes before the first bolt moves.
- Stop the engine, stop the auxiliary blower, and vent skylights so vapour escapes instead of banking.
- Stand clear of relief valves with turning gear ready and fire measures manned — a rich mist above its limit still kills on air entry.
- Wait the twenty minutes for cooling with naked lights and smoking banned throughout.
- Open only cool with oil-mist readings normal, then inspect with flameproof light and subdivision doors proved.
Surveyor follow-up: hotspot alarm with the mist detector pegged high — open now, cool down or flood with air first?
Full theory: Safety — Crankcase Explosion, Scavenge Fire and Starting Air Line Explosion -
21 non destructive tests? Where they are done?
Answer
NDT proves steel without cutting it: dye for surfaces, magnetic for steel cracks, ultrasonic for thickness, radiography for weld roots.
- Dye penetrant marks surface flaws in non-magnetic alloys, stainless and aluminium with developer lines.
- Magnetic particle reads surface cracks in steel plate, welds and highly stressed superstructure breaks.
- Ultrasonic replaces radiography for welds, castings and forgings while also gauging plate thickness and laminations.
- Radiograph only the critical few — gas containment and submersible shells — with lube, water and leak tests alongside.
Surveyor follow-up: suspect crack in an aluminium house front — magnetic, dye or ultrasonic first, and why?
Full theory: Marine Materials, Metallurgy & Mechanical Testing -
22 purpose of hot well??
Answer
The hotwell is the feed buffer: it collects hot condensate, steadies level, vents air and feeds the boiler by gravity head.
- Catches condenser and makeup returns warm, holding a surge volume against load swings.
- Lets dissolved air flash off before the feed pump so oxygen never reaches the drum.
- Supplies steady suction head to feed pumps with level control calling up makeup on low.
- Warmed feed near 80°C through the heat exchanger lifts plant efficiency before the economiser.
Surveyor follow-up: hotwell level hunting with feed pumps cavitating — makeup, air ingress or condenser level first?
Full theory: Boiler Plant Working Flow -
23 Broken stud removal procedure and what is the tool used
Also asked: “How to use stud extractor in taking out broken stud”
Answer
Broken studs come out by drilling and backing out: centre-drill, left-hand tap or extractor, then wind it free.
- File the stump flat and centre-punch dead centre so the drill never wanders into the threads.
- Drill the stud and cut a left-hand thread inside it — tightening the tap anticlockwise backs the stud out.
- Use a proper stud extractor where the stump allows, or weld a nut on for spanner purchase.
- Dress the parent threads with tap and spray before the new stud goes in torqued to figures.
Surveyor follow-up: extractor snapped inside the drilled stud with threads intact — drill bigger, spark-erode or condemn the hole?
Full theory: Maintenance, Overhaul, Inspection and Repair -
24 Describe the action you as watch keeper would take and outline possible reasons for failure in both the following cases
Answer
An auxiliary that will not turn wants air and freedom; one that turns but will not fire wants fuel and timing.
- Fails to turn: bar the engine for seizure, prove starting-air valve open with receiver pressure up, and recheck work just done.
- Jammed engine, shut air valve or flat bottles each stop the crank — open, charge and retry in that order.
- Turns but will not fire: prove fuel to the pumps, air to the cylinders and injection timing alive.
- Log every attempt with pressures and inform the bridge before load transfers — silent retrying strands the board.
Surveyor follow-up: AE turns briskly on air but never fires with fuel proved at the rail — air, timing or compression first?
Full theory: Starting the Engine — Air Start Valve, Distributor and the Four Interlocks -
25 Draw crank case explosion relief door and name the parts. State pressure setting of the door
Answer
Draw the crankcase door with its spring relief: seat ring, base, flame trap, plate valve, spring, test nut and tool.
- Seat ring welded on the door carries the base with the plate valve and packing ring sprung shut.
- Laminated flame-trap plates sit in the gas path to quench flame front on lift.
- Spring force holds the plate closed against normal mist pressure and lifts fast on explosion pressure.
- Test nut and tool prove free lift on schedule; vacuum relief and subdivision doors complete the sketch.
Surveyor follow-up: relief valve painted shut with the test tool missing — protection or ornament, and what proves it?
Full theory: Safety — Crankcase Explosion, Scavenge Fire and Starting Air Line Explosion -
26 Refer LO charging
Answer
Charge lube oil clean and slow: filter the fill, sound the sump, fill to marks and prove flow before turning.
- Fill through filter nets or fine strainers so rags, scale and grit never reach the sump.
- Sound before and after with the ship upright, charging to maker dip marks — never to the coaming.
- Sample the old oil on renewal for emulsification and metals before topping the study file.
- Prove pumps, pressures and sight flows on turning gear before the first start on fresh oil.
Surveyor follow-up: sump overfilled past marks with the purifier running — drain, run on or transfer first, and what foams next?
Full theory: Cooling, Lubrication and Fuel — Systems and the Tanks Checked Before Starting -
27 what is steam trap and its use? Wr it fitted?
Also asked: “What is steam trap?”
Answer
A steam trap is an automatic condensate gate: it holds steam back for its latent heat and passes water out.
- Mechanical float traps lift needle valves on condensate level; thermostatic traps close on steam heat.
- Thermodynamic traps pulse on flash-steam pressure; vacuum traps double as condensate pumps.
- Fitted on heating lines, mains drainage pockets, heaters and traced lines — wherever steam must stay and water must go.
- A blowing trap wastes fuel and starves heat; a choked trap waterlogs and hammers — prove by sight glass and temperature.
Surveyor follow-up: heater cold with steam proved at the trap inlet and the outlet hot — trap, strainer or air binding first?
Full theory: Steam and Condensate System — Interactive One-Line Diagram -
28 Air removal from refr system
Also asked: “Air removal from Refer system”
Answer
Air in a refrigeration system is removed by pumping down and purging: it will not condense, so it sits on top and must be let out.
- Close the receiver outlet and pump the charge down, repeating until the low-pressure cut-out trips, then waiting to settle.
- Air stays at the top of the condenser above the liquefied refrigerant, keeping pressure higher than it should be.
- Slacken the purge valve to expel it, then reopen the valves, restart and top up the charge as needed.
- Most air enters during maintenance or charging — evacuate with a vacuum pump before charging to keep it out.
Surveyor follow-up: high head pressure with no water in sight and the purge left closed — purge, re-evacuate or add charge?
Full theory: Refrigeration Principles and the Vapour Compression Cycle -
29 BROKEN STUD REMOVAL
Answer
A broken stud comes out backwards: centre-drill, cut a left-hand thread inside it, and the stud walks itself out.
- File the stump flat and centre-punch dead centre so the drill never wanders into the remaining thread.
- Drill the broken stud and cut an anticlockwise internal thread — tightening the tap winds the stud out.
- A proper stud extractor is quicker where the stump allows; welding a nut on gives spanner purchase.
- Dress the parent threads with a tap and cutting spray before the new stud goes in, torqued to figures.
Surveyor follow-up: extractor snapped inside the drilled stud with the parent threads clean — drill larger or spark-erode?
Full theory: Maintenance, Overhaul, Inspection and Repair -
30 COMPRESSOR VALVES LEAKING
Answer
Compressor valve leakage shows as lost efficiency and heat: a leaking first-stage suction unloads the set entirely.
- First-stage suction leakage cuts air delivery, lengthens running time and drops pressure into the second stage.
- First-stage delivery leakage sends high-pressure air back into the cylinder, where it heats and fouls the oil.
- Dirty or carbon-coated seats, distorted valves and damaged springs are the usual causes; light springs give slow closing.
- Strip, decarbonise, lap the valve to its seat, check springs and renew anything past its limit, then bench test.
Surveyor follow-up: compressor tripping on high discharge with valves lapped and springs renewed — air in oil, cooling or unload control?
Full theory: Air Compressor Maintenance — Lapping, Clearances & Overhaul -
31 Check guides and guide shoes >
Answer
Crosshead checks are three clearances and the oil wedges: guide plate to rail, rail to shoe, and shoe to pin.
- Turn the piston 90° before bottom dead centre, then feel the three clearances at three positions with the gauge.
- Guide plate to guide rail port-starboard is the side clearance, keeping the shoe from coming out of its plate.
- Rail to shoe in the axial direction sets the guiding length, and shoe to pin checks the crosshead bearing fit.
- Check the oil wedges provided in the guide shoes and the faces for smearing or wear-out before any clearance is blamed.
Surveyor follow-up: shoes sound but a tight side clearance with visible smearing on the rail — shoe, rail or crosshead alignment first?
Full theory: The Moving Parts — Liner, Piston, Gudgeon Pin and Connecting Rod Wear -
32 Check spring on scavenge space relief device, if the device was near the set offire
Answer
Relief devices near a fire are the first casualties: springs weaken, seats leak, and a relief that will not hold is a relief that will not save you.
- Check the spring for heat weakening and set, and the seat for leakage — both are destroyed first by a scavenge fire.
- Pressure-test on a bench rig with a compressor, pressure control valve and calibrated gauges until the valve lifts.
- Bolting the relief valve to the test rig flange and raising pressure gradually proves the lift without risking the engine.
- A device near a fire that has not been proved afterwards is decoration — re-test and renew the spring and seat.
Surveyor follow-up: relief spring heat-blued with the last test two years old — re-test, renew spring, or re-design the location?
Full theory: Scavenge Fires, Trunk Safety & Relief Devices -
33 Chloride test how will you do?
Answer
The chloride test is a titration: potassium chromate plus silver nitrate, read at the first permanent brown end-point.
- Take the cooled boiler sample and add potassium chromate reagent to the same sample used for the alkalinity test.
- Titrate with silver nitrate of known strength — silver chloride precipitates the chloride out of the sample first.
- When all the chloride has gone, the silver reacts with the chromate and the colour turns brown — that is the end-point.
- Calculate the ppm from the volume used, or read it from the chart supplied with the kit, and set the blowdown from the result.
Surveyor follow-up: chloride climbing with the sample drawn hot and unrepresentative — sampling, cooling or treatment first?
Full theory: Boiler Water Treatment, Testing, and Blowdown -
34 Difference b/w Megger nd multimeter
Also asked: “Difference between megger and multimeter”
Answer
A megger stresses insulation with hundreds of volts; a multimeter reads volts and amps — one finds faults, the other measures.
- Megger test voltage runs from 500 V upward, high enough to expose insulation faults a low-range instrument cannot see.
- A multimeter measures volts, amps, ohms and continuity at low voltage — for circuits, not for insulation health.
- A megger is never applied to a live circuit: disconnect and discharge first, or the instrument becomes the fault.
- The megger result is a trend — a falling reading between tests is the warning that a single snapshot never gives.
Surveyor follow-up: megger reading low with the circuit live and the breaker closed — isolate first, or is the reading valid?
Full theory: Marine High Voltage (HV) Installations — 3.3 kV, 6.6 kV & 11 kV Switchgear and Safety -
35 Difference between 2stroje and 4 stroke lub oil
Also asked: “Difference between 2 stroke and 4 stroke engine crankcase oil”
Answer
Two-strokes oil once and lose it; four-strokes keep it circulating — the systems are designed around that difference.
- In the two-stroke crosshead engine the piston has no oil scraper ring, and cylinder oil is not recycled — it is effectively lost.
- Cylinder oil is therefore dosed by a separate external lubricating device through quills in the liner, and the feed rate is critical.
- There is no connection between the piston underside space and the bedplate oil pan, so the two systems never mix.
- Four-strokes lubricate by crankcase splashing and ring return; the oil goes round and round rather than being injected and burnt.
Surveyor follow-up: two-stroke with a heavy exhaust smoke and rising oil consumption — feed rate, ring blow-by or injector first?
Full theory: Two-Stroke Structure — Frame, Tie Rods, Liner, Piston & Crosshead -
36 Dirty or choked filter (
Also asked: “Suction air filter is dirty or choke”
Answer
A choked filter is a pressure drop: less air or water through, more work upstream and hotter downstream, and the fault shows on the gauges.
- On the air side a clogged intake filter drops suction pressure below atmospheric and reduces delivery pressure and temperature.
- On the water side a fouled strainer cuts flow, so the cooler loses duty and the engine heats for the same load.
- Rising temperature on an otherwise normal load is the first sign, with the differential across the filter confirming it.
- Clean or renew the element, log the pressures either side, and never run a choking filter to prove the engine will still run.
Surveyor follow-up: coolant temperature climbing with the strainer clean and the pump proved — valve, fouling or thermostat first?
Full theory: Cooling, Lubrication and Fuel — Systems and the Tanks Checked Before Starting -
37 Exhaust gas temperature
Answer
Exhaust gas temperature is the engine’s own diagnosis: it climbs on the unit with the fault and splits across the bed when all is well.
- Record the exhaust temperature of every unit at a fixed load and compare — a rising unit points at its injector, valve or rings.
- Exhaust temperature after turbocharger also measures the gas side, showing fouling, fouled cooler or blocked air path.
- A spread across the bed at constant load means uneven fuel, air or resistance on one side of the engine.
- Trend it every watch: a slow climb on one unit is the earliest warning a surveyor will later confirm with a borescope.
Surveyor follow-up: one unit 60 degrees hotter with uniform fuel delivery — injector, cylinder or air supply first?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
38 HOW IS IT DONE?
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39 How to charge oil in refer crankcase?
Answer
Compressor oil is charged by pressure or vacuum — either pumps it up against suction pressure or draws it in under a pump-down vacuum.
- Pressure method: stop the compressor, raise the oil pressure above suction so oil flows into the crankcase.
- Purge the connection line first and connect only when lube oil is already flowing, or you charge air instead.
- Vacuum method: pump the system down so the crankcase sits under vacuum and the oil is drawn in.
- Charge to the maker’s quantity and level, then run the compressor and check level again once the oil has circulated.
Surveyor follow-up: crankcase charged by vacuum and level low after the first run — undercharge, separator or leak?
Full theory: The Refrigeration Compressor -
40 Indicator Card Diagrams
Answer
The indicator card is the engine’s combustion portrait: pressures against piston position, read for compression, peak and timing.
- Take it on the same load each watch with the indicator cock and drum ready, marking the position on the chart.
- Compression pressure shows the state of the cylinder; the peak and the angle of pressure rise show the firing.
- Compare cards to spot late injection, over-early exhaust valve opening and rising blow-by before the engine complains.
- The card tells you which fault to chase — it never diagnoses by itself, but it points the overhaul at one cylinder.
Surveyor follow-up: peak pressure down on one card with the same fuel and load — injector, compression or cylinder cleanliness?
Full theory: Marine Fuel Testing, ISO 8217 & Combustion Analysis -
41 Lantern ring .. purpose
Answer
The lantern ring feeds sealing oil to the stern tube seal: it is the oil ring inside the seal assembly, not decoration.
- Fitted at the stern tube seal, it carries and distributes sealing oil around the lip seal assembly.
- It sets the oil pressure at the seal and lets the oil drain back to the header tank rather than into the sea.
- Without it the seal runs dry, the lip wears and the shaft starts passing water into the ship.
- Check the ring turns freely, the oil is present and circulating, and the gland seals do not weep into the boat.
Surveyor follow-up: seal dry with the header tank full and the ring seized — ring, oil line or seal first?
Full theory: Stern Tube Seals — Lip, Floating Ring and Radial Face -
42 Light spring diagram
Also asked: “Light spring diagram is taken if necessary”
Answer
Cylinder and exhaust valve springs run in pairs, series or parallel — and the weak spring is what lets gas past a closed valve.
- Valve springs are hardened steel, and two are commonly used so one acts as a backup if the other fails.
- A failed spring can drop onto the piston, so concentric or paired arrangements are preferred in the space available.
- Two springs of different vibration characteristics also prevent surging when the natural frequency matches camshaft speed.
- A spring weakened in service loses tension, the valve closes late and gas burns past the face — the classic exhaust-valve fault.
Surveyor follow-up: valve closing late on one cylinder with springs matched and new — seating, guide or cam lift first?
Full theory: The Valve Gear and Fuel Injection — Valves, Camshaft Drive, Pumps and Injectors -
43 Loosen the lock nut of the rocker arm
Answer
Rocker arms are adjusted by their adjuster, never by the lock nut: slacken the lock, turn the adjuster, then lock again.
- Slacken the lock nut only enough to free the adjuster — turning the lock nut itself changes the setting.
- Turn the adjuster to move the tappet toward or away from the valve, checking with a feeler against maker figures.
- Re-lock the nut firmly after setting, because a slack lock nut lets the setting walk under the spring’s push.
- Prove the result visually with the engine running — the surest check when the feeler reading is in doubt.
Surveyor follow-up: valve clearance drifting weekly with the adjuster locked — lock nut, tappet face or stem first?
Full theory: The Valve Gear and Fuel Injection — Valves, Camshaft Drive, Pumps and Injectors -
44 MEO-IV (MEP)-September 2022
Also asked: “MEO-IV (SSEP}-September 2022”
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45 Make sure the engine has cooled down
Answer
Cooling first is the rule before any hot work: an engine at temperature holds stored energy that will expand, burst or burn you.
- Shut down, isolate fuel and oil, and let the engine cool naturally — never quench a hot engine with cold water.
- Turn the engine on turning gear with indicator cocks open so hot parts do not seize as they cool.
- Confirm the temperature has fallen by gauge and by hand test, and keep clear of the relief valves and crankcase doors throughout.
- Only once genuinely cool is it safe to open the crankcase, drain it or put a man inside it.
Surveyor follow-up: crankcase opened for a seized follower twenty minutes after shutdown and still warm — the rule first, or the work?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
46 PUT “MEN AT WORK” TAG
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47 Poor quality fuel
Also asked: “Improper fuel quality”
Answer
Bad fuel burns badly: less power, smoke, deposits and heat — and the engine tells you which cylinder first.
- Incomplete combustion cuts the power developed and raises fuel consumption, with heavy smoke from the funnel.
- Thermal cracking of the fuel lays carbon on heating surfaces, reducing heat transfer and steaming capacity.
- Deposits foul exhaust valves, block scavenge ports and cool the liner badly enough to start lacquer and ring sticking.
- Fix it at source: purge and purify, blend to specification, restore the temperature and clean the engine after the bad parcel.
Surveyor follow-up: one cylinder hot with fuel proved to spec on all units — injector, cylinder cleanliness or air supply?
Full theory: Cooling, Lubrication and Fuel — Systems and the Tanks Checked Before Starting -
48 Pull the fuel rack to zero
Answer
Fuel rack to zero is the emergency stop: it cuts the fuel where every unit still has a little left.
- Pulling the rack to zero stops fuel admission to all cylinders without shutting a separate fuel valve.
- It is a hold-and-run control — pulling the emergency fuel lever shuts the fuel and it stays shut until reset.
- Use it when a unit must be stopped quickly or a runaway must be cut, keeping the mechanical fuel valve for isolation.
- After any rack operation, vent the fuel line before opening a fuel oil filter or the last air bubble keeps the engine running.
Surveyor follow-up: rack pulled but one unit still running on trapped air — vent, isolate, or restart and pull again?
Full theory: Two-Stroke Main Engine Standby & Start Preparation: Preheating, Turning Gear, Blow-Through & Bridge Control Changeover -
49 Read the manual and have a toll box meeting with everyone involved in the job. Discuss the procedure
Answer
Before non-routine work: read the maker’s manual, hold a toolbox talk with everyone involved, and agree the procedure before starting.
- The manual gives the maker’s limits, sequence and cautions — the first reading, not a fallback after failure.
- The toolbox talk covers who does what, the isolation, the permits, the tools and what stops the job.
- Everyone involved speaks, including the person who will actually do the work and the one who can call it off.
- Agree the emergency arrangements and the abort criteria at the talk, then record the procedure and the attendance.
Surveyor follow-up: a non-routine job started with no toolbox talk and one man injured — which of the two steps was skipped?
Full theory: SOLAS Chapter IX — ISM Code & Safety Management Systems -
50 Scavenging types and uniflow benefits
Answer
Three scavenge layouts, rising efficiency: crossflow about 0.75–0.80, loop 0.80–0.90, and uniflow above 0.90.
- Crossflow puts inlet and exhaust ports opposite each other at the same end of the liner, with a swirling inlet.
- Loop scavenging places the exhaust ports above the inlet ports at the same end, giving 0.80–0.90 efficiency.
- Uniflow puts inlet ports and exhaust valves or ports at opposite ends of the liner, so fresh air never meets exhaust gas.
- Uniflow gives the highest efficiency, cleaner gas paths and better heat transfer, and supports turbocharging of large outputs.
Surveyor follow-up: uniflow engine scavenging falling toward loop figures with boost normal — air filter, cooler or ports?
Full theory: Two-Stroke Structure — Frame, Tie Rods, Liner, Piston & Crosshead -
51 Shell and tube leaking , how u will find out
Answer
Find a cooler leak dry-side: clean the sea side, pressurise the shell side, and watch the dry tubes for the weep.
- After cleaning the sea-water side, remove the end covers, dry the tubes, then circulate the fresh or oil side through the shell.
- Leakage in the tubes or at the tube-plate junction shows at once on the dry outside surface as a wet patch.
- Soap solution on the tubes under about 1 bar raises a bubble at the leak, or run the sea side and look for air in the water.
- Plug or retube the offender, then re-drain, re-fill and pressure-test the whole cooler before it goes back in service.
Surveyor follow-up: no bubbles on the sea-side test but coolant losing level — gasket, tube-end or the gauge first?
Full theory: Plate Heat Exchangers: Working, Operation, Maintenance & Troubleshooting -
52 Steam trap functions
Answer
A steam trap holds the steam and passes the water: steam stays in the line to give up its latent heat, condensate leaves automatically.
- A special automatic valve that prevents the passage of steam while allowing condensate through.
- Used on heating lines, mains drainage points, heaters and traced lines wherever steam must stay and water must go.
- Three main types: mechanical float traps, thermostatic traps and thermodynamic traps, plus vacuum traps or pump traps.
- A blowing trap wastes fuel and starves heat; a choked trap waterlogs the line and hammers it — prove by sight glass and temperature.
Surveyor follow-up: heater cold with steam proved at the trap inlet and the outlet blowing — trap, strainer or pressure?
Full theory: Steam and Condensate System — Interactive One-Line Diagram -
53 T/C surging? Reasons?
Answer
Surging is the compressor stalling and banging: any change in air mass flow unbalances the wheel — fouling, load swings, starvation.
- Any factor changing air mass flow: fouled air filter, compressor or turbine wheel, blades, nozzle ring or economiser.
- Sudden load changes in manoeuvring, rough seas, overload and crash astern disturb the balance.
- Engine rpm changes vibrate the flow, and fuel starvation from dirty filters or wrong timing starves the turbine.
- Cure by reducing speed to drop scavenge pressure, then cleaning the path and steadying load before winding back up.
Surveyor follow-up: surging only at full load with clean filters — load change, fouling or fuel pressure first?
Full theory: Marine Turbochargers: Aerodynamics, Bearings, Washing & Surge Mitigation -
54 T/C turbine side washing
Answer
The turbine side is cleaned hot with chemicals or granules, from outside the engine room, on a slow controlled run.
- Water washing suits the blower side; the turbine side is cleaned with about 1.5–2 kg of granules blown by compressed air.
- Granules of 1.2–2.0 mm size strip deposits from the nozzle ring and blades where water alone will not.
- Chemical cleaning is used where deposits are sulphurous, because water interacts with them and causes corrosive attack.
- Drop the load slowly over at least 30 minutes to get the turbine inlet to its working temperature, or quenching cracks the blades.
Surveyor follow-up: turbine wash ordered on a cooling engine — warm through, wash, or wait for the next port?
Full theory: Marine Turbochargers: Aerodynamics, Bearings, Washing & Surge Mitigation -
55 Under cooling of parts within the cylider
Also asked: “Under cooling of parts within the cylinder”
Answer
Undercooling shocks the cylinder: uneven expansion, lacquer, brittle rings and cracks where heat alone would only wear.
- Too little jacket or piston cooling gives non-uniform heating and thermal stress across the cylinder wall.
- Overheated piston and liner evaporate and burn the cylinder oil, depositing lacquer and carbon on the surfaces.
- Those deposits destroy ring elasticity, causing sticking, scoring and eventually a stuck piston.
- Keep the coolant up to maker minimums, warm through gradually on start, and never cool a hot engine suddenly.
Surveyor follow-up: liner cracked after a cold start with valves and gauges proved correct — cooling, handling or assembly?
Full theory: Cylinder Liner Wear, Calibration & Cold Corrosion -
56 What is electrochemical corrosion
Also asked: “what is galvanic corrosion”
Answer
Electrochemical corrosion is metal dissolving because it is the anodic half of a cell — the electrolyte carries the current away from it.
- Every corrosion reaction moves electrons through a solution where ions conduct, and that solution is the electrolyte.
- Sea water is a good electrolyte, so it makes ship corrosion electrical as well as chemical.
- Galvanic corrosion is the case where two metals of different potential are coupled, and the less noble one corrodes.
- Name anode, cathode and electrolyte, then the protection: coating, sacrificial anodes or the impressed-current system.
Surveyor follow-up: bronze propeller with steel shaft in sea water and anodes not fitted — which metal corrodes, and how fast?
Full theory: Marine Materials, Metallurgy & Mechanical Testing -
57 refer oil charging procedure
Also asked: “Procedure for ref oil charging”
Answer
Reefer oil is charged stopped, or under vacuum, and always through a purged connection so you charge oil and not air.
- Pressure method: stop the compressor and raise the oil pressure above suction so oil flows into the crankcase.
- Purge the connection line first and connect only when oil is already flowing, or air is charged instead of oil.
- Vacuum method: pump the system down so the crankcase is under vacuum, and let the oil be drawn in.
- Charge to the maker’s quantity and level, run the compressor, then recheck the level once the oil has circulated.
Surveyor follow-up: compressor runs hot after an oil charge with the level correct — overcharge, wrong grade or air in the oil?
Full theory: The Refrigeration Compressor
Source: 123 written papers and surveyor oral banks, 24,613 entries, merged into 17,210 topics. Ticks are stored on this device only.