Auxiliary Machinery - ER — Most Asked Questions
20 questions asked about auxiliary machinery - er across the General and Fn 6 and Fn 3 and Fn 4b papers, heaviest first. 1 of them are must-master.
Learn the system first
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1 Bilge pump not taking suction?
Also asked: “bilge pump not taking suction...how to detect fault”, “Bilge pump is not taking suction(foot valve, stainer, valves everything is in good condition but still it is not taking suction”, “Bilge pump is not taking suction. Reasons”
Answer
A bilge pump that turns but lifts nothing is starved, choked or breathing air — work from strum box to overboard valve in order.
- Suction side first: fouled strum box and blocked suction filter are the classic answers; add leaking foot valve, suction lift too high, air leak in suction piping and undersized suction pipe.
- Pump side: worn impeller or wear rings, relief valve passing, pump unprimed or air-bound, wrong rotation after maintenance.
- Discharge side: closed or stuck overboard/bilge injection valves, high backpressure, collapsed hose or blocked line.
- Prove air ingress by holding suction under vacuum and watching the gauge fall, then joint-by-joint from pump toward strum; prove chokes by comparing suction vacuum against normal.
Surveyor follow-up: suction vacuum is high and discharge pressure low — blockage or air leak, and where exactly?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
2 Starting air line safeties
Answer
The starting-air line stands between a hot cylinder and a steel manifold — non-return, flame trap, bursting disc and relief valve in that order.
- Non-return valve between bottle and manifold stops any explosion travelling back toward the air receivers.
- Flame trap of brass or alloy with bored passages sits before each start valve, quenching flame from a leaking cylinder valve.
- Bursting disc of copper with tell-tale bursts on over-pressure to save the manifold; relief valve on the common line lifts first.
- Manifold extras: vent, drain, thermal patch and its own bursting disc — drain moisture daily or the first start hammers wet.
Surveyor follow-up: bursting disc ruptured with relief valve intact — slow over-pressure or sudden backfire, and which part proves it?
Full theory: Starting Air System Physics, Explosions & Air Distributor -
3 EMERGENCY BILGE SUCTION
Answer
The emergency bilge suction is the flooding weapon: a direct open pipe to the biggest seawater pump, with no strainer to choke.
- It leads straight to the main cooling seawater pump suction — no mud or strum box to block it.
- Normal bilge suctions carry screw-down valves with mud boxes at platform level; the emergency leg stays direct and labelled.
- At sea use direct bilge and injection only in dangerous flooding; in port pump to the bilge tank or ashore.
- Pumps must be self-priming or quick to prime, with a direct suction on each side of the machinery space.
Surveyor follow-up: water over the floor plates with both bilge pumps running — what suction change do you order next?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
4 How vaccum in fwg
Also asked: “How vacuum is generated in fwg”
Answer
Fresh-water generators boil seawater in vacuum: ejector pumps pull the vacuum, jacket heat boils near 40 degrees, vapour condenses to distillate.
- Ejector pump on seawater drive evacuates the evaporator toward 69 mm of mercury.
- Jacket cooling water heats the evaporator near 70 degrees shell with feed cracked in and bypass trimmed.
- Vapour rises through baffles and demister, condenses on tubes and collects below the condenser.
- Salinometer proves under 2 ppm before the discharge valve opens to the collection tank.
Surveyor follow-up: vacuum weak with the pump running — nozzle, gaskets or breaker, and what proves it?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
5 What type of valve is present in bilge pump system and why?
Also asked: “What valve used in bilge pump”
Answer
Bilge suctions carry screw-down non-returns: shut tight against backflow with mud boxes guarding the seat.
- Screw-down non-return on every suction stops bilge water returning when the pump stops.
- Emergency direct suctions to the biggest seawater pump stay valved and labelled for flooding use.
- Mud and strum boxes at platform level guard seats from rags and sludge.
- Pumps self-prime or prime fast with every valve proved operable from above the floor plates.
Surveyor follow-up: bilge back-flooding with the pump stopped — valve, seat or strainer, and what first?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
6 Ballast pump casing crack?
Answer
A cracked ballast casing gets surveyed honesty: prove the crack, dress pits, weld or stitch by procedure, renew when condemned.
- Open with marks punched and the line isolated; map cracks, pits and cavitation before deciding weld or renew.
- Putty and Devcon only for pits inside limits — pressure casings earn approved welding with survey agreement.
- Survey history decides: scantlings, thickness reports and heated-cargo records follow the casing file.
- Pressure-test before return with glands, wear rings and alignment proved — a weeping casing fails the ballast drill.
Surveyor follow-up: crack filled with putty on the pressure volute with thickness reports missing — temporary or failure?
Full theory: Centrifugal Pump Construction -
7 Reduction in vacuum in the suction lines of bilge pump system due to ingress of air, has been experienced JaList the causes leading to this problem
Answer
Bilge suction loses vacuum where air gets in or strainers choke: joints leak, boxes foul, lift climbs too high.
- Fouled strum boxes and blocked suction filters starve the pump before vacuum can build.
- Leaking joints, glands and foot valves bleed air into suction lines that should run tight.
- Excess lift, small-bore or elbow-choked suction piping drops inlet pressure into cavitation.
- Prove by filter inspection, joint sounding, gauge reading and proper priming before condemning the pump.
Surveyor follow-up: vacuum low with filters clean and joints tight but lift at maximum — piping, pump or tide first?
Full theory: The Bilge System the Separator Serves -
8 fwg vaccum dropping, y?
Also asked: “Why vaccum drop in fwg”
Answer
FWG vacuum drops when air enters or the ejector weakens: seals leak, pump falters, overboard shut, brine floods.
- Prove the brine ejector and overboard valves fully open with motive flow steady — a lazy pump kills vacuum first.
- Hunt air leaks at joints, glands and the vacuum breaker left cracked after maintenance.
- Flooding from failed extraction or rising salinity collapses vacuum the same way a leak does.
- Recover by ejector proving, leak sounding and level correction in that order — then watch salinity fall.
Surveyor follow-up: vacuum low with the ejector roaring and overboard wide open — air leak, flooding or instrument first?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
9 A) describe the constitutional features of plate type fresh water generator and its operational procedures for fresh water generation
Answer
A plate FWG condenses steam on a bank of gasketed plates, with a demister on the vapour side and a coil for the feed heating.
- The shell is fabricated steel coated with rolled sheet rubber, and the condenser is a plate-type pack, not a tube nest.
- A knitted monel wire demister scrubs the vapour and knocks out entrained brine before the distillate leaves.
- Operation is vacuum boiling: keep the ejector running, hold the feed level, and take distillate at the rated rate.
- Watch the salinometer and condenser temperature — the salinity is what decides whether the water goes to the tank or the drain.
Surveyor follow-up: distillate salinity rising with feed temperature and ejector proved — is the demister, the feed or the vacuum?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
10 Ballast pump looses suction during deballast, actions ? And indications ?
Answer
Losing suction mid-deballast is air or cavitation: the tell is noise, vibration and falling delivery pressure.
- Cavitation appears when the pump suction contains air or the pump runs faster than its design speed.
- Low pressure regions vapourise the liquid, bubbles expand and then collapse at high pressure — and that collapse is the hammer.
- Indications are pitting, noise, vibration and falling pump efficiency, with the suction gauge unsteady.
- Actions: check the foot valve and strainer, look for a suction air leak, never throttle the suction, and prime the pump again.
Surveyor follow-up: pump cavitating at the end of deballasting with the strainer clean — is the foot valve, the lift or the speed?
Full theory: Centrifugal Pump Construction -
11 Bilge pump questions
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12 Bilge pumping arrangement in cargo hold
Answer
Cargo holds are pumped from the bilge main: fire and bilge pump, general service pump and auxiliary bilge pump, each with direct suctions.
- The bilge main has suctions from the engine room port and starboard sides, from the tunnel well and from the different cargo holds.
- Three pumps connect to it: the fire and bilge pump, the general service pump and the auxiliary bilge pump.
- Each pump also has a direct bilge suction — engine room sides and tunnel well — so pumping survives a main failure.
- Non-return valves stop a flooded hold emptying back, and a bilge level alarm in the hold and engine room gives the warning.
Surveyor follow-up: hold flooded with the main suction valve shut and no direct suction open — how is it emptied?
Full theory: The Bilge System the Separator Serves -
13 C. CONTROL AIR VALVES FAULTY OR LESS
Answer
Control air is a three-way set — service, start and stop — and each one failing takes the engine a different way.
- A small valve admitting air operates the puncture valves to admit fuel; a leak there gives an engine that will not stop.
- A faulty stop valve leaves the engine running when the fuel lever is put to stop, which is the classic non-stopping fault.
- A weak start valve gives slow or late starts, and air in the control line shows as an engine that hunts or will not hold speed.
- Prove all three on the standing schedule — the fuel lever must stop the engine even with the start valve jammed.
Surveyor follow-up: engine will not stop with the fuel lever at stop and the stop valve proved — is the start valve, the line or the stop valve?
Full theory: Maintenance and Troubleshooting — Overhauls, Tappet Clearance and Reading a Fault -
14 Fwg efficiency low why
Answer
A weak fresh water generator is a vacuum problem: air in, leaks, a tired ejector, or a flooded condenser.
- Air in-leakage or a leaking ejector drops the vacuum, and with vacuum gone the boiling temperature rises and output falls.
- Fouled condenser tubes or a scaled evaporator transfer less heat, so the same firing makes less distillate.
- A feed level too high floods the vapour side and the demister cannot separate the water from the brine.
- Check vacuum first, then feed temperature, feed rate and salinity — the four together tell you which it is.
Surveyor follow-up: output down with vacuum held and feed at temperature — is the evaporator, the condenser or the feed rate?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
15 Fwg..Location of salinometer y temperature compensator
Answer
The salinometer goes on the distillate line so every drop of potable water is measured, and its reading is corrected for temperature.
- The cell sits in the distillate line between the condenser and the storage tank, with bypasses either side.
- A fixed sample stream keeps the cell wetted, and the indicator is placed where the watch can read it easily.
- The temperature compensator corrects the reading to a standard temperature so the reading is comparable watch to watch.
- With it, the ejector, the feed and the tank levels are controlled against one number — the salinity of what is being made.
Surveyor follow-up: salinity reading low with clean samples tested ashore — is the cell, the bypass or the compensator?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
16 How fresh water generator works?
Answer
A fresh water generator boils seawater under vacuum and condenses the vapour: heat, vacuum, condensation, and a salinity check.
- Seawater feed is heated by exhaust gas or steam coils, and the ejector holds the evaporator below atmospheric pressure.
- At that reduced pressure the water boils well below 100°C, so the exhaust gas supplies the latent heat cheaply.
- The vapour rises through a demister that knocks out entrained brine, and the clean vapour condenses on the plates or tubes.
- Distillate flows to the tank only when the salinometer is satisfied; otherwise it goes to the drain and the overboard.
Surveyor follow-up: distillate salinity high with vacuum and feed temperature normal — is the demister, a tube leak or the feed?
Full theory: Fresh Water Generator — Vacuum Boiling, Operation & Faults -
17 If ballast pump has stopped taking suction or if the tank level has dropped, how will you come to know and what will be your actions
Answer
You find it by the level and the pressure, not by the noise: falling tank level, low suction pressure and cavitation on the pump.
- The tank level dropping without the pump discharging, or the suction gauge low with the pump running, shows the loss of suction.
- Causes are a leaking foot valve, an air leak in the suction line, a blocked strainer, or excessive suction lift.
- Actions: stop the pump before it runs dry, then check the strainer, the foot valve and every suction joint for air.
- Prime and restart, and log the level readings so the rate of loss tells you whether it is a leak or a valve passing.
Surveyor follow-up: ballast pump running dry with a clean strainer — foot valve, suction air leak or the level itself?
Full theory: Centrifugal Pump Construction -
18 Shut starting air valve for main engine
Answer
Shut it to make the engine safe to work on — the valve is locked, tagged and the air proven dead at the distributor.
- Closing the main start air valve at the stop position isolates the whole distributor from the receiver.
- Vent the line after closing and prove it dead at the distributor before any work starts on the starting system.
- Lock and tag the valve, and open the air receiver isolating valves to the compressor and start valves so it cannot refill.
- The pneumatic stop or puncture valve is a fuel control, not an isolation — the air valve is the safe one for overhaul.
Surveyor follow-up: overhaul started with the start valve closed but the air receiver still charged — what is still live?
Full theory: Two-Stroke Main Engine Standby & Start Preparation: Preheating, Turning Gear, Blow-Through & Bridge Control Changeover -
19 Starting airline explosion
Answer
A starting air line explodes when a leaking or jammed air valve lets hot gas into a manifold already filmed with oil mist.
- Compressor oil leaves a thin moist film inside the starting air pipes that is not itself combustible.
- A leaking or jammed-open starting air valve lets hot gas or flame into the manifold and vaporises that film.
- The mist and greasy deposits ignite — and it usually happens on the first start for a manoeuvring, at high delivery.
- Prevent it by keeping valves and gaskets sound, draining the receiver and traps, and never leaving a valve open.
Surveyor follow-up: air valve weeping on the first start after a month alongside — start the engine or strip the valve first?
Full theory: Safety — Crankcase Explosion, Scavenge Fire and Starting Air Line Explosion -
20 Without seeing the connection how to distinguish the discharge nd suction line of bilge pump from pressure guage
Answer
Identify them by the gauge: the discharge gauge sits on the pump delivery with the pump shut, and the suction reads vacuum.
- With the pump stopped and the line dead, the gauge on the delivery holds pressure, and the suction gauge reads vacuum or zero.
- Start the pump: the discharge gauge rises to working pressure, and the suction gauge drops below atmospheric.
- A gauge that reads vacuum on discharge, or working pressure on suction, means the valves are on the wrong branch.
- Then trace it by hand from the gauge to the pump casing, and confirm with the flanged joint labelling on the drawing.
Surveyor follow-up: two gauges reading the same at the manifold — is it a crossed line or a failed gauge?
Full theory: The Bilge System the Separator Serves
Source: 123 written papers and surveyor oral banks, 24,613 entries, merged into 17,210 topics. Ticks are stored on this device only.