CHAPTER No 3
CARGO HOLD EQUIPMENTS
A bulk carrier exists to carry cargo, and is expected to do safely, efficiently and without loss.
To achieve this the ship equipment must all be in good working order.
This can only be achieved by regular maintenance, and by methodical proving of all the systems every voyage.
These, tests and inspections must be carried out before cargo is loaded, – as required by the BLU Code, Section 2.2. BIMCO Denmark, Confidential reports, 1997.
Some items, must be tested / inspected before the commencement of each discharge.
Only mini bulkers performing one or more voyages a week most items still be checked each voyage, but some can be left for regular but less frequent inspection.
The hold ventilators must be in good working order to fulfil two functions,
(1) they must provide adequate ventilation to the hold if required.
(2) they must be capable of being completely sealed to prevent the entry of water in adverse weather conditions, and the entry of air if a fire occurs which must be smothered.
Hold ventilators and the process of ventilation.
(A) Ventilators which are closed by doors should be checked to ensure that
(1) the rubber seals have not been covered with paint, become permanently indented or cracked and brittle (εύθραυστο) with age,
(2) confirm that door closes properly,
(3) the sealing bar meets the center of the door rubber,
(4) the hinges (μεντεσέδες) should be undamaged and they should move freely,
(5) the butterfly nuts should move freely,
(6) Located somewhere in the trunk (κορμός) of each ventilator, or at the point when it enters the hold, is a light metal grille (γρίλια) which prevents sparks, insects, and rats from entering.
This can normally be reached by way of an inspection panel, set somewhere in the ventilation trunk. The grill must be renewed if it is damaged or wasted, and loose rubbish and scale must be removed from it.
(B) Mushroom ventilators are usually closed by turning the wheel which is set on top.
This brings a damper plate inside the mushroom cowl (καλύπτρα) into contact with the lip (χείλος) of the ventilator trunk.
A rubber (neoprene) seal is set into the damper plate, and it must be in good condition to ensure a watertight fit.
The seal can be inspected when the ventilator is open by looking upwards into the ventilator cowl from a position on deck beside the ventilator.
The grille in a mushroom ventilator is usually fitted in several parts, located in the position illustrated, and must be renewed if damaged.
The shaft of the wheel must be greased and working freely. If the shaft is coated with grease and the grease has become contaminated with dust and grit (βρωμιά) from the cargo the shaft is likely to jam. Before the ventilator is opened, the contaminated grease should be removed from the shaft.
Then the treated part should be wiped with a rag soaked in paraffin before the ventilator is opened and closed and the shaft greased.
The wheel must be clearly marked with the OPEN and CLOSE directions, and the marks should be checked to be sure that they have not been reversed – mistakes can easily occur on older ships when the original plates have wasted, and been replaced by painted signs.
All ventilators should be correctly labelled to show the compartment which they serve. Most bulk carriers built since 2000 are provided with cargo hold ventilators set into the forward end of the Hatch Covers and a similar pair of ventilators set into the after end of the hatch covers.
Ventilators set into the hatch panels usually consists of rectangular (ορθογωνιο) openings closed by steel doors with neoprene seals.
The seals must be in good condition the hinges and butterfly nuts be free and greased and the grille must be intact.
These are easy to open or close, easy to clean to fit and maintain but are more exposed to sea water and spray on deck than are mushroom ventilators, and therefore require more attention. Ventilators of this type usually do not contain fans. The arrangements within the hatch cover depend upon whether the hatch panels are single or double skinned.
If fixed fans are provided in the ventilator trunks for Mechanical ventilation of the holds they should be tested whilst the holds are empty.
First they should be checked electrically to confirm that they are in good condition, and inspected by eye to ensure that nothing is lying on the fan blades.
When ready to run all the options should be tested , including running fans in both directions where that is possible, and running them at full and at half speed.
The fan trips and / or emergency stops should also be tested regularly.
Natural ventilation can occur as a result of a wind blowing the ship’s motion, or the circulation of air resulting from temperature differences Ventilation assisted by fans is known as mechanical or forced draught ventilation, whilst ventilation which occurs as a result of natural movement of air is called natural ventilation.
On ships employed in areas where bad weather is common, such as North – West Europe, ventilators are normally kept permanently closed and sealed to prevent the entry of the water. Despite this, it is still essential that all working parts should be kept in good operating condition by following the procedures described above.
It is only in this way that ventilators which work correctly can be guaranteed for the occasional voyage where ventilation is essential.
Older bulk carrier ventilation are more likely to be provided with two or four ventilation trunks per hold, with one or two situated at the fore end of the hold, and one or two at the after end. To avoid passing through the top side tanks these ventilator trunks are situated close to the ship’s center line. Within the hold each such trunk often terminates in a simple square, round or rectangular opening in the deck head. .
Alternatively trunking may continue down the bulkhead, with slots at intervals to admit air to the hold at various levels. Portable plates can be put in place to close the lower slots, when ventilation at lower levels in the cargo is not wanted.
Above deck the ventilation trunk stand alone, each fitted with a mushroom cowl which gives some protection form spray and from the direct force of an wind.
Every ventilator must be provided with a means of closing so that all ventilation can be stopped in the event of fire.
The means of closing may be in the form of a ventilation flap or damper set within the vent tank and operated by external lever, or a watertight door or may consist of a cowl which can be screwed down into a closed position by the operation of a valve wheel.
Some bulk carriers are provided with ventilators fans set in the trunks of ventilators.
When fans are provided they are normally fitted in the ventilator or ventilators at one end of the hold. Ventilator fans can usually be run in both directions so that they can be used either to deliver air to the hold and to draw air from the hold.
It may be possible to vary the speed of the fans, selecting full speed or half or a larger range of options.
Ventilator trunks are liable to heavy corrosion in some trades, and sheets of loose scale can develop within them.
From time to time the opportunity should be taken to remove scale from the trunks.
When a hold is loaded with a bulk cargo the ventilation provided is usually surface ventilation, with air flowing over the surface of the cargo from ventilators (situated) (1) at the after end of the hold to ventilators at the fore end of the hold or in newer ships, (2) from ventilators (situated) in the after end of the hatch covers to similar ventilators in the fore end of the hatch covers. (3) Ventilators situated at the hold ends can provide surface ventilation only for the nearly hold ends when the cargo is a low density one topped up in the hatch square and preventing a flow of air from one end of the hold to the other. When the hold is filled the hatch square requires separate ventilation (Fig.15.6).
Through ventilation of a bulk cargo, when air is forced into the body of the cargo, is not normally required and is difficult to achieve.
Some through ventilation can be provided aboard ships in which ventilator trunks extend the bottom of the hold bulkheads.
The capacity of a ship’s hold ventilation fans is normally expressed in the number of air changes that can be achieved in an empty hold per hour.
When a cargo is carried the number of air changes per hour will be increased, because the quantity of air which the hold contains is reduced.
TANK AIR PIPES
The air pipes (goosenecks) for ballast, fuel and freshwater tanks must be kept in good order so that tanks can be filled and emptied without problem, and the entry of the sea water can be prevented.
Air pipes must be correctly labelled to show the tank that they serve.
Their non-return system, allowing liquids out of the air-pipe but not in, must be working properly.
When the system uses a float It must be visually and manually inspected for damage, and to ensure that it seals the air pipe properly.
A hand finger can usually be inserted inside the air pipe to lift the float and ensure that it is free.
Damaged floats must be renewed, and on older ships it is prudent to carry a few spares.
SAVEALLS are provided around all fuel tank air pipes.
SAVEALLS must be clean and dry with the drain plugs free and greased. The height of the save-all must be less than the height of the air pipe.
Ballast tanks must not be over – pressurized.
The ballasting pressure will be too high and damage will occur if tanks are filled faster than the water can overflow from the air pipes when the tank is full.
Such damage can occur if two pumps are used to fill a single ballast tank or if ballast tank air pipes are damaged or blocked.
Ballast tanks must not be under – pressurized.
If tanks or ballast holds are emptied with air pipes and ventilators closed the resulting vacuum (κενό αέρος) can cause severe damage to the deck structure, and hatch covers in the case of ballast holds. Before de-ballasting can commence, the ballast tank air pipes must be open.
Aboard modern bulk carriers the air pipes usually designed to be always open, but in older vessels the air pipe cowls may need to be raised, or opened, to admit air into tank.
If this is forgotten the ballast pumps will begin to labor as they try to remove water from a sealed tank, or the structure of the tank may be damaged as a vacuum is created within it.
When pumping ballast tanks full or empty in freezing conditions it is important to ensure that the air pipes are clear and that air is flowing through them.
Ballast tanks have been ruptured (ρηξη / διαρηξη) when pumped at a time when their air pipes were locked with ice.
(1) Hold bilge wells must be thoroughly cleaned after every cargo, and all cargo, and all cargo sweepings must be removed.
(2) Bilge sounding pipes can be proved free by running water down them into the bilge, and
(3) Bilge suctions can be tested by pumping the bilge well dry. The end of the bilge suction line is normally provided with a (4) strum box, which prevents rubbish from entering the line. Tis must be clean.
(5) Non-return valve fitted in the bilge line to ensure that water cannot enter the hold through the bilge line, must be tested.
The easiest way to test the non-return valve is to stop the pump and allow water to flood back into the bilge line.
If it flows through into the hold bilge the non-return valve, normally situated in the stool space or the duct keel, is not working properly and must be opened up and cleaned.
In any event all the non-return valves should be cleaned at regular intervals.
On completion of inspections the bilge wells must be correctly closed, and their perforated (διατρητα) (6) cover plates must be covered with (7) burlap. (8) High level bilge alarms when fitted, should be tested by raising the float towards the top of the bilge and confirming that the alarm sounds on the bridge and / or in the engine room.
WATER INGRESS DETECTORS
Introduced in accordance with IMO regulations (WIDS) are now fitted in the holds of all bulk carriers and also in the ballast, dry and void spaces forward of their collision bulkheads.
They are designed to give early warning of flooding and to provide an indication of the speed of flooding of a compartment.
Flooding is one of the most serious hazards to which bulk carriers are exposed and there are situations in which a flooding bulk carrier can sink within minutes. The detectors in the hold should be tested before each cargo is loaded.
(1) Moisture sensitive type they can be tested by applying a wet cloth to sensor head.
(2) Pressure activated water ingress detectors can, in some cases, be tested, by temporary fitting of a pipe which is filled with water to the required level. In addition processes such as the cleaning of filters over pressure detectors, the inspection of cables, sensor glands (υποφυση) and mounting flange bolts and the calibration of sensors should be carried out at the intervals specified by the manufacturers.
The function test of audio and visual alarms must be carried out daily.
• Water can leak into holds,
• through the hatch covers,
• through leaks in the deck,
• through leaks in ship’s sides,
• through ballast tanks,
• through ventilators,
• through damaged air pipes
• through uncapped bilge soundings pipes,
• through bilge suction, bilge educator and ballast lines.
Leakage can only occur when the ship or her fittings are defective or misused. Leakage into holds can damage cargoes and even to the sinking of ships.
Leakage can usually be detected by a rise in the ships soundings or by the setting off of high level bilge alarm, when fitted.
The Water Ingress Detectors are fitted to detect serious leakage and will activated if flood reaches 0,5 meters.
When holds are empty leaks into hold can be seen, provided they are below the sea surface.
Leakage is prevented by ensuring that the ship’s structure is sound and undamaged and that her all fittings are properly maintained, regularly tested and correctly used.
The most reliable soundings of tanks and bilges are obtained with (1) sounding rod (ράβδος) and (2) line when the depth is small, for (3) sounding tape with water finding paste when depths are large. These methods, of course rely upon the sounding pipe being clear.
A sounding pipe can become blocked with cargo residues which can float into a hold bilge sounding pipes when there is water in the bilge, or with cargo of rubbish which can fall into it if the sounding pipe cap is left off.
Loose rust and parts of old sounding rods and lines can also block sounding pipes.
As noted above, sounding pipes can be proved clear by :
(1) running water down them into the bilge or the ballast tank.
(2) They can also be checked by viewing, from a position at the base of the sounding pipe, the arrival of the sounding rod in the bilge well or in ballast tank.
(3) A table of tank and bilge ullages (the distance from striking plate to top of sounding pipe), prepared from careful direct measurements and checked against the ship plans can also be used to check if sounding pipe are clear.
(4) Another quick and simple check is to compare the ullages found for similar soundings.
The sounding rod should reach the same depth on the port side as on the starboard side.
Similarly, aboard a large bulker the No.3 bilge or double bottom tank sounding will, for example, probably be same depth as the equivalent No.4 soundings,
If the depths are found to be different, it Is likely that a false sounding is being obtained in the pipe which appears to be sorter, and the cause of this must be investigated and removed.
A blocked sounding pipe must be cleared as soon as possible, and various ingenious methods can be used to remove the obstruction and return the pipe to its former sound condition,
Every sounding pipe should be provided with a cap which fits well, opens and closely freely, and has a watertight rubber seal in place.
To prevent water or rubbish from entering the pipe the cap should be fitted at all times except when the sounding pipe is used or the bilge is being pumped.
The accuracy of the remote reading systems for ballast tank soundings should be checked by comparison with actual soundings obtained with sounding rod.
Before each cargo is loaded a remote reading system for soundings, when fitted, should be given routine maintenance in accordance with the manufacturer’s handbook.
The air pressure used by the system should be set to the correct value, according to the manufacturer’s handbook.
All empty compartments, including void spaces, bilges and dry tanks should be sounded and / or inspected to confirm that they are empty.
Importance of soundings:
Throughout the loaded voyage, as at all other times, soundings of cargo spaces, ballast tanks, void spaces and bunker tanks should be taken and recorded by the same competent person. The readings obtained should be inspected carefully for any unexplained increases or decreases in the values observed. When the sounding positions are located on the open main deck and when the vessel is in adverse weather with a low freeboard, it is often unsafe to obtain soundings on the ship’s weather side or even on both sides.
This is unfortunate, though unavoidable once the ship’s design has been finalized.
In these circumstances the chief mate should be alert for any opportunity occurring when in the lee of land or because of an improvement in the weather to obtain a set of soundings.
Failing this the hold bilges should be pumped daily until suction is lost.
Reasons for any failure to obtain soundings should be logged.
During the 1980s and 1990s there were numerous indications that aboard badly-run bulk carriers a full set of soundings was sometimes not obtained for days or weeks on end,
It is true that in almost every case soundings when taken only confirm what the chief mate already knows – namely, that the ship is not leaking. But is only when soundings are obtained daily, at the very least, that there is a reasonable chance that any damage or oversight will be detected promptly when it occurs. Water ingress detectors if working properly, should defect serious flooding in forepeak and cargo holds at an early stage but will not detect water at tank top level.
Such water would seriously damage or even destroy a variety of cargoes and in addition would give warning that something was wrong.
The safe delivery of cargoes can depend upon this seamanlike precaution and the daily taking of soundings should never be neglected.
High soundings in “empty” tanks:
Warning of a leak is provided by increased soundings in ballast tanks and void spaces and must be investigated promptly.
First it may be necessary to pump out the compartment.
Provided that the flooding is not too rapid such investigation will normally involve entering the compartment – taking all the proper precautions when entering an enclosed space and searching for the source of the leak.
When the leak has been found, the problem can be assessed and the correct action chosen.
Interpretation of High soundings in a cargo space:
When increased soundings are found in a cargo space loaded with bulk cargo there are a number of possible explanations and each should be considered.
The water may have:
(1) drained from the cargo,
(2) leaked through the hatch covers,.
(3) entered through an un-battened access hatch,
(4) an uncapped sounding pipe,
(5) a fracture in the deck,
(6) a damage ventilator.
It is regrettable that officers of many ships have no accurate idea of the capacity of the hold bilge wells.
This means they cannot say whether an increase sounding of 0,5 meters represents 1 ton of water or 10 tons of water.
That makes more difficult to assess the significance of any increase in hold bilge sounding.
The solution to this is simple.
Measurements should be taken when the holds are empty to prepare simple calibration.
Of greatest value are the sounding of the bilge when full and the appropriate tonnage of water contained by the bilge when full.
When preparing calibrations for the hold bilge wells two important points must be remembered. If the sounding pipe does not run vertically the actual full sounding will be greater than the vertical depth of the bilge well.
It is the actual full sounding which is required since that is what the sounding rod measures. On some ships a number of bilge wells may have exactly the same dimensions, but everyone must be inspected in case the arrangements inside any are different.
Details of design near the engine room or in ballast hold, for example sometimes require one or two bilge wells to be of different shape and size to the others or to have the sounding pipe positioned different and soundings will be very misleading unless this is known.
High soundings caused by drainage of cargo:
Aboard a ship which is well operated and well maintained he most likely reason for an increased hold bilge soundings is that water has drained from the cargo into the bilge.
If there has been a similar increase in most or all of the bilge soundings this suspicion will be a virtual certainly particularly if the cargo is known to be self-draining.
Water is reported to drain from most mineral and coal cargoes during the course of a long voyage with consequent weight losses of 1 per cent total weight of cargo or more.
In a Cape-sized carrying about 22.000 tons of iron ore per hold the water draining from the cargo in one hold would average 5 tons / day during a 40 day voyage if 1 per cent figure was found to apply.
Water will also drain from a grain cargo which has been sprayed with a fumigant during loading.
When water does drain from the cargo there are two important requirements:
(1) The water must be pumped out of the bilge and not allowed to flood the hold, and
(2) “the tonnage of water removed must be recorded”.
The reason for removing the water is to prevent damage to the cargo and increased (1) corrosion of the tanks top and reduce (2) difficulties for the trimmers when discharging.
It must also be remembered that once that the water has filled the bilge well and flooded back over the tank top, it is much more difficult to be sure how much water the hold contains. Flooding of the hold from a leak would then become more difficult to detect.
For all these reasons the bilges must be jumped as frequently as is necessary to maintain them in a safe level – no more than half full.
It is advisable to keep record of tonnage of water discharged from the hold bilges, as recommended by the UN Draught Survey Code and in some trades it is a charter party requirement.
This can be done by taking soundings before and after each pumping of the bilges if calibration table for the bilge wells are available or by pumping all the contents of the hold bilge wells into a holding tank where they can be sounded before being pumped overboard.
Such a record, if kept in a seamanlike and professional manner and signed by the Master or senior officer, will be evidence of the tonnage of water discharged and will explain apparent loss of cargo weight / shortage.
High soundings due to leakage into hold:
When one or several soundings found to be rising for no obvious reason a problem must be suspected and the hold must be investigated for a leak.
Whether the hold can be entered will depend upon the amount of space occupied by the cargo and the safety of the operation from the point of view of speed of flooding, shifting cargo and hazardous gases. If the hold can be safely entered, taking all the precautions required for entry into a confined space, it may be possible to find an explanation for the flooding.
Evidence of water flowing into the hold may be detectable in the cargo beneath hatch covers or ventilators or below a fracture in the steelwork of deck, coamings or ship’s sides.
If the hold cannot be entered, a thorough external inspection should be made of the boundaries of the compartment in search for any fitting which is improperly closed or damaged.
If the sounding is found to increase whenever the vessel ships water on deck, a leak at deck level should be suspected.
If the flooding continues at the same rate or an increasing rate, at all times it suggests that the damage is below water level.
By using all the information available the most likely explanation for the flooding can be found and appropriate action can be taken.
High level bilge alarms:
When high level bilge alarms are fitted and working as intended they provide a useful service to back-up the daily soundings and to provide for occasions when adverse weather prevents the taking of soundings. High level alarms will give prompt warning if flood holding starts suddenly and proceeds rapidly, However, high level alarms may not fitted or may be out of order. Each high level bilge alarm should contain a delay circuit which prevents the alarm from sounding continually when the water level is low but the hip is rolling heavily.
If no delay is fitted the alarm will sound continually during heavy weather and is likely to be switched off. If it is switched off for this reason the sounding must be regularly checked by other means.
High soundings detected by hull stress monitors:
It is claimed that hull stress monitors will detect flooding of a bulk carrier because flooding will cause a change in ship’s average level of longitudinal stresses.
When an observer at sea notes that the vessel is becoming more heavily loaded there is only one likely explanation: flooding is occurring.
High soundings detected by draught gauges (μετράω):
In at least one instance hold flooding a forward hold has been confirmed by a high reading on the forward draught gauge. Readings from draught gauges, list indicators and any other devices which indicate a change in the vessel’s condition should be promptly and thoroughly investigated,
Testing of bilge water for acidity
Cargoes such as sulfur coals, iron ore, sulfur and salt produce corrosive liquids when wet and can do heavy damage to the fabric of the hold.
When cargoes which may be corrosive are being carried the hold bilges should be tested regularly for PH (acidity).
HOLD TEMPERATURE SYSTEMS
Cargo temperatures may be measured by gauge via
(1) gas / sampling points or
(2) bimetal sensors embedded (εμφυτευω) in the cargo, in which cases the necessary equipment must be checked and ready for use when required.
Alternatively temperatures may be read from (3) sounding pipes,
but are sometimes read from (4) separate pipes, similar to sounding pipes, positioned at the forward and aft ends of each hold.
Ensure that temperature pipes are correctly labelled.
Their positions against the corrugated transverse bulkhead can mean that No.4 forward is forward of No.3 aft.
The caps of temperature pipes must fit well, have watertight seals and be kept in position except when pipe is in use.
The base of the pipe must be checked to ensure that it is free of water and that the opening in the base is clear, and guarded with light metal gauze (γάζα) or a similar product.
Water standing in the pipe would produce water vapor, and might depress the temperature readings. Any damage to the pipes, sustained when discharging previous cargoes, should have been found and repaired.
Thermometers should be inspected for any apparent faults, such as breaks in the mercury or alcohol. They should be compared with the temperature gauge used for calibration or with other temperatures in use around the ship for example in the refrigerators, storerooms, engine room and on the bridge to confirm that their readings agree.
The lines used to lower the thermometers into the pipes should be in good condition, and of the correct length to reach the depth required.
Usually the thermometers are left permanently hung in the temperature pipes, so that a set of temperatures can be taken quickly when required.
The line can be fastened to the underside of the pipe cap, or attached to a plug (πώμα-τάπα) placed in the top of the sounding pipe, provided that a watertight seal can be maintained.
Some ships prefer not to leave the thermometers suspended in the temperature pipes. To obtain an accurate temperature reading one man installs the thermometers into the temperature pipe ( όλα τα θερμόμετρα σε ένα σωλήνα) and waits one hour for the thermometers to register reading. Then he completes a round on deck taking the temperatures , removing the thermometers and re-securing the top to the temperature pipe. Although this is time consuming it is suggested that this way water-tightness is better ensured and the thermometers suffer less damage.
When carrying some cargoes such as coal and grain the temperature of the cargo should be obtained regularly to detect signs of heating.
Temperatures are usually obtained from thermometers lowered into the sounding pipes on the port and starboard sides at the after end of each hold.
An additional temperature pipe may be sited beside the hold ladder at the fore end of the hold.
The most accurate and reliable readings will be obtained by making sure that the thermometers are lowered to level which is well below the surface of the cargo and that they are left in position for several minutes.
Where possible there should be a thermometer for each position and thermometers should be left in place permanently and withdrawn rapidly when readings are required.
Mercury thermometers are considered to be less satisfactory for taking cargo temperatures unless fitted with a maximum temperature indicator and reset before the taking of each reading, and one authority recommends the use of suitably calibrated pyrometers.
When carrying coal it is necessary to test the air in the holds for hazardous gases.
All deck and hold lighting should be switched on for inspection before the loading port is reached, and bulbs and tubes should be replaced as required.
If the cargo is hazardous the hold and hold access lighting, if not of a certified safe type, must be isolated before the commencement of loading, and the circuit fuses should be removed to a safe place in the care of a responsible officer.
All lights should be maintained on a regular basis, such maintenance to include the greasing of moving parts, freeing of securing dogs, checking and renewal of glass covers and rubber seals as required, and inspection of wiring and conducts.
Cable conducts (σωλήνας-αγωγός) in the holds should have already been checked for physical damage which may have occurred during the last discharge.
Following rough weather, cable conducts on deck, if damaged, may contain water which should be drained.
The electrician or a member of the engineering staff should regularly test the cables for “earths”. Portable, deck and hold lighting is required in any port where the shore lighting is inadequate, and also for security purposes.
A ship committed to worldwide trading should hold a minimum of four (4) portable floodlights or clusters for each hold, two (2) to light the hold and two (2) to shine over the ship’s side to illuminate the jetty or craft alongside.
Ships engaged in regular trading between well equipped ports are unlikely to need so many portable lights, but should carry extra lights for security and anti – piracy purposes.
Before reaching each port the portable lights should be tested, bulbs should be replaced and repairs should be made as necessary.
The cables should inspected for damage.
Rope lanyards should be long enough to hang the lights in the correct position.
A portable light should never be hung by its electrical cable, Light bulbs must always be protected by a wire cage or screen.
FIRE SMOOTHERING SYSTEMS
The basic components of fire smothering system are
(1) the battery of gas bottles in the bottle room,
(2) the mechanical control system for selecting the compartment to be smothered and for controlling the number of bottles released, the gas pipes which carry the gas to the compartment, and the nozzles which emit (βγάζω) the gas.
On modern ships the nozzles, four (4) in numbers, are usually set in the hatch coamings, so that no pipe work is within the holds. – Double skinned bulkers.
On older ships gas pipes often enter the hold and lead to nozzles located under the deck-head.
If smoke detecting system is also provided, as is often the case on handy size and smaller bulkers, a fan will be used to draw air samples continuously from each compartment through the gas lines to detecting cabinet, usually placed on the bridge, where a photoelectric cell will detect smoke and cause an alarm sound.
Problems and their prevention:
A number of problems can and do occur with these systems.
The pipes which carry the CO2 from the bottle room to the hold, the gas lines, can fill with water from condensation (υγροποίηση) or can be blocked by cargo residues when cargo such as grain is loaded up to coaming level.
In the case of the ballast hold the lines can also be flooded with ballast water, while the gas lines within the holds of older ships can be damaged by cargo operations.
When the lines air blocked with water or residues, the smoke detecting system cannot work, and the CO2 smothering may be ineffective.
To prevent or correct some of these problems the manufactures may include a variety of fittings in the system.
HATCH COAMING DRAINS
If the hatch coaming drains are blocked with cargo, as happens easily and frequently, the danger of leakage of water into the holds is increased.
It is essential to ensure that the drains are checked and cleared, and that their non-return valves – often containing a floating ball – are free before loading of each cargo, and again after loading, and before battering down the hatches.
Compressed air directed upwards from the bottom of the drain is a quick and effective method of clearing a blocked drain.
If this doesn’t work, the non-return valves must be dismantled and cleaned, and any blocked drain pipe must be cleared with a stiff road, or even by the use of a drill if badly blocked.
To prevent the hatch drains becoming filled with debris when loading a dusty or fine cargo, some ships temporarily fit half a broom pole into the top of each drain at the start of loading.
This prevents the fine grains of cargo entering the drain and causing a blockage.
The broom pole is usually painted a bright color to prevent any careless hatch closure before it has been removed.
On long voyages, and in cold weather, the rubber ball of the non-return valve may stick.
A quick poke (μπήγω-χώνω) with a rod or screw driver will free it. Hatch coaming non return drain valves often get washed away or damaged during cargo operations.
It is in ship’s interest to ensure sufficient spares are kept onboard.
If no spares are available, a temporarily solution is to attach a rubber tube to the drain hole and turn this back on itself to form a U bend, ensuring the end is below the coaming drain.
To prevent or correct some of these problems the manufactures may include a variety of fittings in the system.
Gas sampling points set into the hatch covers or coamings should be provided with screwed caps to maintain the water-tightness of the hatches. These should be greased, the rubber seal inside the screw cap should be in good condition and the cap should fit correctly and be watertight.
Cement / grain loading ports. Round bolted covers set into the tops of the hatch panels with one centrally placed for loading and a second perhaps in a corner, for the exhaust air, may be provided allow cement to be loaded with the hatches closed Other possible reasons for the provision of bolted covers are to allow the fitting of portable cowls for the ventilation of the hatch square or to insert butter worth machines for washing the hold. These ports should be provided with a gasket (φλαντζα) in good condition and great care should be taken when closing them after use to ensure that the joint is free of any dirt or particles and that the bolts are well tightened to achieve a watertight seal.
Hatch cover securing or locking devices are provided to ensure that, when hatches are opened the panels are prevented from moving if the ship rolls or develops a list. They should be distinctively painted, kept in good working order and used whenever the hatches are open.
Deck machinery on a bulk carrier includes the windlass, mooring winches, capstans and hatch-opening motors.
It also includes air motors used on deck, and cargo-handling gear, such as cranes or derricks and their winches, if fitted.
Before arrival in port, deck machinery should be tested in good time to ensure that it is operational.
An exception must be made, of course, in cases where the vessel enters port directly from a bad-weather passage.
In these circumstances the best that can be done is to inspect and test deck machinery as soon as possible after reaching sheltered waters.
Motors in exposed positions, control pedestals (βάθρο) for deck machinery, and emergency stop buttons can usefully be provided with canvas or waterproof covers to protect them from heavy spray or rain, and these should normally be fitted at sea.
They can be temporarily removed in hot dry weather to give covers and equipment an airing.
Hatch opening chains and wires should be inspected for defects and regularly greased or coated as per the manufacturers’ guidelines.
The hydraulic systems for operating the hatch covers and the deck machinery depend upon an adequate supply of hydraulic oil.
When the deck machinery and services are switched on, the decks should be checked for hydraulic and pneumatic leaks, which sometimes develop as a result of the ship working in a seaway or vibration during the passage.
Any leaks which are found should be promptly repaired, and any leakage of oil cleaned up to prevent a pollution incident.