Q. Mandatory requirement for monitoring water ingress in cargo holds – bulk carriers potential problem
Bulk carriers potential hazards
Ingress of sea water into cargo holds poses significant threat to bulk carriers while on sea passage and in harbour. Effective means of monitoring hold bilges for presence of water are traditional practice. However New regulations now become part of the Safety of Life At Sea (SOLAS) convention and came into force on 1 July 2004. According to this regulation bulk carriers are now required to carry equipment that will give early warning of water ingress to the hull.
Introduction of Water Ingress Monitoring
Water Ingress Monitoring (WIM) is not a new concept. Masters will recognize that daily monitoring of bilges and tanks has been a feature of prudent seamanship since antiquity. However, this method of monitoring does not provide continuous information. Furthermore, when weather deteriorates the manual process is usually suspended because of the dangers to crew members taking the soundings. In such conditions the risk of flooding in the ship is increased and therefore some method of continuous monitoring should be introduced. The concept now adopted for bulk carriers by IMO monitors not only for the presence of water, but also, in the cargo hold spaces, the speed of ingress. To achieve this a two stage alarm is used, one at a low level in the hold, the second a short distance above it.
Methods of detection may vary. Some manufacturers use simple float switches, others may have other methods of detecting water. It is even permissible to install alarm points at the levels prescribed in the regulation in remote tank sounding systems.
The following guideline describe an example WIM system in more detail and how the provision should be used within the ship’s Safety Management System. There are many variations in bulk carrier design. Each must be addressed individually. For example some ships do not have lower stools in which detection equipment can be positioned and thereby be well protected. In such cases WIM can be installed in protective tubes alongside existing sounding pipe arrangements.
Details of equipment for monitoring water ingress problem
Equipment designed for the purpose of monitoring water ingress to the hull of a bulk carrier must conform to a performance standard. Different manufacturers may design their equipment with variations in layout but all must be provided with certain minimum indicators and alarms.
All audible alarms should be connected to a mute button. This is to prevent interference with communication caused by loud alarms during the investigation process. The mute button cannot extinguish the indicator lamp, which must remain lit until the condition causing its activation is no longer present. An exception to this rule is in the case of spaces in which ballast is carried. The monitors for these spaces may be fitted with interlocks that disable the alarms and indicators but this interlock must be arranged so that when the (ballast) water level falls below the lowest alarm the monitor returns to the active condition.
The systems must be provided with internal monitoring arrangements aimed at detecting faults. The two principal types are open and short circuit and these should be detectable on each branch of the system so that ¬ for example ¬ an open circuit detected on a monitoring sensor in a hold is clearly identified in that part of the system. Furthermore the existence of such a fault should not affect the operation of the remainder of the system that serves other spaces.
Finding the reason of flooding
It is important that investigation is carried out responsibly and that the process does not endanger lives. Seafarers have been swept overboard in heavy weather conditions when they have ventured on deck to investigate a known ingress of water. Adverse weather conditions may make such operations extremely dangerous and masters should not commit crew members to open decks unless there is no alternative. In making such a decision masters should consider the value of such action. The purpose of WIM is to make it possible to know the condition in each hold without having to locally investigate.If an alarm is activated, the master should ¬ without delay – seek to verify the condition by reference to other indicators:
i) Is the vessel taking a list?
ii) Is the vessel trimming excessively
iii) Is anything visible on deck such as dislodged hatch covers and water emerging from spaces that would otherwise be dry?
These indicators may be provided by such systems as heel indicators, trim indicators and draft gauges. It should be remembered that the purpose of the investigation is to determine first, that a real alarm situation exists and second the extent to which the situation has progressed. The WIM may overtake this activity. For example, if an alarm has activated in one space and this is followed by another alarm, either in the same space or, more onerously in an adjacent space, it is reasonable to conclude that the situation is real. In the case of a bulk carrier, if two holds are flooding the ship almost certainly cannot remain afloat.
The master should act swiftly to protect the lives of those on board. Unless the vessel is in such shoal waters that grounding will occur before immersion of the hull, the crew should be prepared for abandoning the vessel without delay. Abandoning ship should only done after the verbal order from master . And master should consider it only as a last resort.
Precautions against ingress of water
Some key actions should be considered essential in the event of any activation of WIM. Vessel’s crews should:
In the event of activation of a “pre-alarm”, go to emergency stations. This should include :
i)preparation of life-saving appliances in readiness for evacuation but the craft should not be lowered or boarded.
ii) Alert shore rescue co-ordination stations using Urgency or if rapid sinking is detected early, Distress ;
iii) In the event of a main alarm, muster (all personnel) at abandon ship stations with the exception of those crew members engaged in investigation of the alarm and/or keeping systems running.
iv) Upgrade any urgency signal to one of Distress;
v) In the event of a second space alarm activation ¬ either Pre-alarm or Main alarm ¬ ensure all personnel are recalled from investigation and other duties and sent to abandon ship stations. This should include any crew remaining in the engine room or other spaces;
vi)Boats, Liferafts or Other Life saving craft must not be launched unless the specific order to do so has been given by the master.
The master should only order abandonship:
i) If the vessel is truly sinking. Checks of other indicators should be made quickly e.g. draft gauges, heel indicators,
ii) rapid air expulsion from vents serving spaces suspected of flooding, dislodgement of hatch covers, water emerging from spaces where it should not be expected;
iii) The depth of water is greater than the depth of the hull (a beached ship should not be abandoned);
iv) The speed of sinking is such that launching of life-saving craft must begin immediately in order to reach the water
