Ventilation, airpipes, hold bilges, soundings, hold temperature systems, deck ami hold lighting, fire smothering systems, hatchcoaming drains, deck machinery, derricks and cranes
A BULK CARRIER exists to carry cargo, and is expected to do so safely, efficiently and without loss.
To achieve this the ship's equipment must all be in good working order. This can only be achieved by regular maintenance, described in Chapter 23, and by methodical proving of all the systems every voyage.
This chapter is devoted to the routines, tests and inspections which must be carried out regularly to ensure that everything is in good order before a cargo is loaded, and at other stages in the voyage.
In general, every item listed in this chapter should be inspected or tested before each cargo is loaded and the hatches are battened down. This is particularly true for larger bulk carriers completing only six or eight loaded voyages a year. Some items, it will be obvious, must also be dealt with before the commence- ment of each discharge. On mini-bulkers performing one or more voyages a week most items must still be checked each voyage, but some can be left for regular but less frequent inspection.
Hold ventilation
The hold ventilators must be in good working order to fulfil two functions. First, they must provide adequate ventilation to the hold if required. Second, they must be capable of being completely sealed to prevent the entry of water in adverse weather condi- tions , and the entry of air if a fire occurs which must be smothered.
The variety of designs of hold ventilators are described in Chapter 15. Vents which are closed by doors (Fig.6.1) should be checked to ensure that the rubber seals have not been covered with paint, become permanently indented or cracked and brittle with age.
Confirm also that the door closes properly, and that the sealing bar meets the centre of the door rubber.
The hinges should be undamaged, and they and the butterfly nuts should move freely.
Located somewhere in the trunking of each ventilator, or at the point when it enters the hold, is a light metal grille which prevents sparks, insects and rats from entering. This can normally be reached by way of an inspection panel, set somewhere in the ventilator trunking. The grille must be renewed if it is damaged or wasted, and loose rubbish and scale must be removed from it.
Mushroom ventilators (Fig.6.2) are usually closed by turning the wheel which is set on top. This brings a damper plate inside the mushroom cowl into
contact with the lip of the vent trunking. 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 vent is open by looking upwards into the vent 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 from the cargo the shaft is likely to jam. Before the vent is opened, the contaminated grease should be removed from the shaft. Then the threaded part should be wiped with a rag soaked in paraffin before the venti- lator is opened and closed, and the shaft is regreased.
The wheel must be clearly marked with the 'Open' and the 'Close' directions, and the marks should be checked to be sure that they have not been reversed—
FIG. 6.1
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mistakes can easily occur on older ships when the original plates have wasted, and been replaced by painted signs.
Ventilators which end in mushroom cowls at the heads of samson posts (Fig.6.3) are provided with ventilator flaps set in the trunking. When the lever is operated these flaps should move freely between the 'Open' and the 'Closed' positions, which must be clearly marked. The flaps should be inspected to confirm that the open and closed positions are correctly marked, and to ensure that the ventilator flap does turn with the shaft to which it is supposed to be attached. On some ships the flap is fastened to the shaft with bolted collars. Wastage can allow the fastenings to become loose. Such ventilator flaps are not always easily accessible but they and the grille can usually be inspected by torch from an access panel somewhere in
the ventilator trunk.
FIG 6.3
All ventilators should be correctly labelled to show the compartment which they serve. Ventilators set into the hatch coamings usually consist of rectangular openings closed by steel doors with neoprene seals.
The seals must be in good condition, the hinges and butterfly nuts must be free and greased, and the grille must be intact.
Some vessels are provided with portable mushroom ventilators for bolting to the hatch covers when venti- lation of the hatch square is required, as may be the case when coal or grain cargoes are carried. Before the start of a voyage for which they are required such ventilators should be unshipped from their stowage positions, cleaned and freed as necessary to ensure that they are in good operating condition, and ready for fitting immediately when required. The bolted plates set into the hatch covers must also be freed, ready to receive the cowls.
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.
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 water. Despite this, it is still essential that all the 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 occa- sional voyage where ventilation is essential.
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.
Tank airpipes
The airpipes (goosenecks) for ballast, fuel and fresh- water tanks must be kept in good order so that tanks can be filled and emptied without problem, and the entry of sea water can be prevented. Airpipes must be correctly labelled to show the tank that they serve.
Their non-return system, allowing liquids out of the airpipe but not in, must be working properly. When the system uses a float (Fig.6.4) it must be visually inspected for damage, and to ensure that it seals the airpipe properly. Damaged floats must be renewed, and on older ships it is prudent to carry a few spares.
Hold bilges
The hold bilge wells must be thoroughly cleaned after every cargo, and all cargo sweepings must be removed. The bilge sounding pipes can be proved free by running water down them into the bilge, and the bilge suctions can be tested by pumping the bilge well dry.
The end of the bilge suction line is normally provided with a strum box, or grille, which prevents rubbish from entering the line. This must be clean.
The 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, 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 grilles must be covered with burlap. 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 engineroom. (These matters are described more fully in Chapter 5.)
Soundings
The most reliable soundings of tanks and bilges are obtained with sounding rod and line, or sounding
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tape, in the sounding pipe, provided that the sounding pipe is clear. A sounding pipe can become blocked with cargo residues which can float into a hold bilge sounding pipe when there is water in the bilge, or with cargo or 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 running water down them into the bilge or the ballast tank. 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 the ballast tank. A table of tank and bilge ullages (i.e.
distance from striking plate to top of sounding pipe), prepared from careful direct measurements and checked against the ship's plans, can also be used to check if sounding pipes are clear.
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 the 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 shorter, 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 being used.
The accuracy of 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 manufac- turer's handbook. All empty compartments, including void spaces, bilges and dry tanks should be sounded and/or inspected to confirm that they are empty.
Hold temperature systems
Cargo temperatures may be taken from sounding pipes, but are often read from separate pipes, similar to sounding pipes, positioned at the forward and after ends of each hold. Ensure that temperature pipes are correctly labelled. Their positions against the corru- gated transverse bulkhead can mean that No.4 for'd is forward of No.3 aft, for example (Fig.6.5). The caps of temperature pipes must fit well, have watertight seals and be kept in position except when the 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 or a similar product. Water standing in the pipe would produce water vapour, 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, and compared with other thermometers in use around the ship—for example, in the refrigerators, storerooms, engineroom 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. If possible the thermometers should be 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 placed in the top of the sounding pipe, provided that a watertight seal can be maintained (Fig.6.6).
Lighting
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 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 conduits. Cable conduits in the holds should have already been checked for physical damage which may have occurred during the last discharge. Following rough weather, cable conduits on deck, if damaged, may contain water which should be drained.
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 portable floodlights or 'clusters' for each hold, two to light the hold and two 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 be 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 smothering systems
The basic components of the fire smothering system are the battery of gas bottles in the bottle room, the mechanical control system for selecting the compart- ment 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 the gas.
On modern ships the nozzles, four in number, are usually set in the hatch coamings, so that no pipework is within the holds. On older ships the gas pipes often enter the hold and lead to nozzles located under the deckhead (Fig.6.7).
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If a 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 a detecting cabinet, usually placed on the bridge, where a photo- electric cell will detect smoke and cause an alarm to 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, 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 are 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 manufacturers may include a variety of fittings in the system:
• Each gas line may be fitted with an individual drain valve for the removal of water.
• Each GO2 nozzle may be provided with a spring-loaded shutter which must be shut by hand when grain or similar cargo is carried, and opened after the cargo has been discharged.
• Each GO2 nozzle may be provided with a removable dust cap which will be blown off if the CO2 is released.
• Each gas line serving a ballast hold may be provided with an isolating valve, to be dosed when ballast is carried and opened when cargo is carried.
• Each gas line serving a ballast hold may have a 'spade', or 'spectacle', piece (i.e., a blank) which can be used to seal the line in the same way that an isolating valve does.
• Each gas line serving a ballast hold may be provided with
a non-return valve which will admit COj gas to the hold, but will exclude ballast water from the gas lines.
• 'U' bends, placed in the gas lines at positions higher than the coaming top, may be used to prevent ballast water from entering the lines.
Shutters when fitted are spring loaded, and will be forced open by a gas pressure of more than 1.5kg/cm2. If the gas lines can be shut by a valve, there is often a bypass line fitted with a pressure dix, for each valve. The pressure disc will burst to admit the CO2 gas into the hold in the event that smothering is required when the valve has been left shirt, by mistake. Unfortunately, the pressure created by ballast water, pressed up or sloshing in the ballast hold, can also burst the disc and allow ballast water into the gas lines.
From the foregoing it will be clear that the CO2
system must be properly understood, and correctly set for ballast or cargo. At the ballast hold the gas lines must be closed when the hold is ballasted and open when cargo is carried. At all holds it may be necessary to close the shutters or fit the dust caps over the nozzles to keep out dust or light cargo, and to open the shutters for other cargoes.
Routine testing—the gas lines: These problems, and the varied methods provided for their solution, make it easy for the gas lines to be blocked by waste matter, or by a shutter, valve or blank wrongly set.
The most important rule, therefore, is to make absolutely sure before each cargo is loaded that the gas lines are not blocked or closed. This should be done by blowing through each line in turn with compressed air.
Most systems have a compressed air connection in, or near to, the CO2 bottle room, so that compressed air can be blown into each compartment by operation of the appropriate valves. Often there are two blanks to be changed before the compressed air test is made:
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