Hipótesis específica 3

4.2.1. Introduction

The carbon dioxide system is efficient and has certain advantages when extinguishing fire onboard ships. It is installed in places where fire may commonly occur and is readily available for use when necessary and does not need a deployment of fire fighting groups. It is also advantageous because its use does not leave residue to be cleaned off and does not damage cargo and equipment. It is especially efficient against fires involving flammable liquids. It is common to many ships to have their cargo spaces and engine room protected by this system (Nazzaro, 1989). This Chapter deals with the emergency response involving fire in cargo spaces and engine room.

4.2.2. Fire in a cargo hold

4.2.2.1. Introduction

Fighting a fire located in a cargo hold may not be effective if using only hose lines because of the high probability of the spreading of the fire. This system is only possible when the fire is limited and well located and identified. However, the most effective means to fight the fire is to use the carbone dioxyde system through which the fire is smothered, i.e. the oxygen is removed from the cargo hold. Moreover, it has also a second effect, which is to cool the hold involved in the fire. This system prevents the spreading of the fire and extinguishes it completely, if properly used. The emergency response comprises different steps starting from the hearing of the alarm to the extinguishing of the fire.

4.2.2.2. On hearing the alarm

As noted earlier, when an alarm is sounded or heard, it is the responsibility of the OOW to find out what is happening. The identification of the exact location of the fire can be observed from the bridge if the ship is equipped with detector alarms, which is a regulatory requirement for most ships. Although, it is vital to verify that the detector indication is correct, it must be assumed that the fire is affecting the entire cargo in the involved hold. For this reason, an attempt to fight the fire by portable extinguishers or hose lines should not be conducted. Once, the involved hold is located, the OOW can undertake the next step.

4.2.2.3. Confining the fire

One of the immediate responses that have to be conducted when the fire is located is to confine it in the involved space. In any circumstance for safety reasons, the cargo hold should not be opened while at sea (Lygate, 1998). Therefore, the hatch cover will already be closed. However, if the ventilation is operating, it has to be shut off. Moreover, the vent openings have to be covered, and flaps and any route leading to the hold closed. If it is observed that smoke can escape from the hold therefore any suitable material should be used to prevent it. Furthermore, it is still possible that the fire may spread to other holds therefore a careful watch should be kept on the alarm, to monitor adjoining holds (Nazzaro, 1980).

4.2.2.4. Release of CO2

lowest involved space, then into the next higher space and so on (Nazzaro, 1980). It is also the responsibility of the officer to determine the number of gas cylinders to be discharged into the involved cargo hold or to protect adjoining holds.

4.2.2.5. Cooling the surrounding area

Heated decks, hatch covers and bulkheads take a long time to cool down because of the low cooling effect of CO2. After releasing the CO2, the responsible officer should check if heat is felt on the open deck or the hatch cover of the involved hold. If so, the affected areas should be well hosed with water to assist in cooling to prevent spreading of the fire. The use of hoselines is required for this purpose. If it is possible to establish that the adjoining holds are not affected but the bulkheads separating the holds are heated, it is vital to cool them down (Lygate, 1998). However, using water in holds may affect the stability of the ship therefore a light spray of water should be used to cool heated surfaces. Nevertheless, if the involved cargo hold adjoins the engine room, it may be crucial to cool the separating bulkhead to protect the engine room.

4.2.2.6. Precautionary measures

Precautions are to be observed in relation to the number of gas cylinders available on board. It may be necessary to discharge CO2 in adjoining holds if they are likely to be threatened. Moreover, the maker’s instructions on the use of the system using ` topping up ´ requires an additional use of the CO2 in the involved hold. Should the ship run out of CO2, it might be necessary to use the CO2 installed for engine room protection on the involved hold. However, the quantity of gas onboard is limited. Therefore, it is advisable to consider factors such as the distance of the ship from land where supply of CO2 can be obtained and the important threats observed onboard, after the first necessary release

of CO2 in the hold is made. In the author’s opinion, the CO2 intended for the protection of the engine room can also be used but only as a last resort.

4.2.3. Fire in the engine room

4.2.3.1. Introduction

A fire in the engine room may be small or very threatening. If it is small, it can be fought with portable extinguishers or by using hose lines. But, in case of a big fire, more efficient means are necessary. In either case, when an engine room fire is discovered the normal routine responses are followed. If these responses are not successful, a more effective response is the use of the CO2 system, which is described below.

4.2.3.2. Evacuation

If the fire cannot be tackled by means of hoselines, the engine room has to be evacuated immediately with the intention of using the CO2 system. During the attempt to fight the fire with hoselines, the group assigned to this task should always be prepared to leave the engine room once it is deemed necessary. However, the chief engineer has the ultimate decision to do so. CO2 is hazardous to humans because if inhaled it raises the acidic level in the blood and leads to respiratory arrest (Nazzaro, 1980). In any circumstance, since a total flooding of CO2 system is to be used in the engine room, evacuation is imperative before any release.

4.2.3.3. Confinement

As in cargo spaces, fires in the engine room also have to be confined properly to prevent spreading. After the engine room is evacuated, the attack team together with the engine room team conduct an external inspection to ensure that doors, skylights, funnel flaps and other openings are properly closed. All ventilation systems must also be shut off to permit a proper confinement of the engine room. However, most ships should now have an automatic shut off ventilation as required by SOLAS Convention. If this task is not properly conducted, using CO2 system may be in vain.

4.2.3.4. Cooling and internal inspection

Cooling the heated areas is necessary to protect them from overheating, which may lead to their deformation or, even worse an explosion (Lygate, 1998). Two or three hours after the release of CO2, it is important to check if the fire is extinguished. An internal inspection can be made by engineers wearing breathing apparatus. Hoselines should be ready to respond in case the fire has persisted. However, the door should only be opened wide enough for the hoselines. Otherwise, there is a risk that the fire will start again because the CO2 may be replaced by entering oxygen. If the fire is out, ventilation of the engine room should be put on to draw out the smoke (Nazzaro, 1980). Due to the fact that it is difficult to find out whether the fire is extinguished or not when entering a smoke-filled engine room, the ventilation can wait until it is really safe to use it. The failure to observe this remark may result in the rekindling of the fire due to the presence of oxygen from air.