The Hazards and Procedure for Entry into Enclosed Spaces on an Oil Tanker - Essay Example

The Hazards and Procedure for Entry into Enclosed Spaces on an Oil Tanker Introduction An enclosed space is defined as one with restricted access, without exposure to continued ventilation, “and in which the atmosphere may be hazardous due to the presence of hydrocarbon gas, toxic gases, inert gas or oxygen deficiency” (ISGOTT, 1996: 130). In any enclosed space such as a cargo tank, cofferdam, or double-bottomed tank, is present the potential risk of hazards. Hence, it is the responsibility of the ship’s master or competent person to identify such spaces and establish procedures for safe entry. The responsible officer determines whether entry into such enclosed spaces is safe, before issuing an entry permit to the personnel (IMO, 2006). Thesis Statement: The purpose of this paper is to investigate the hazards that may be faced on entry into enclosed spaces on an oil tanker, and to outline the appropriate procedure to be followed for entry into an enclosed space. Discussion An enclosed or confined space in an oil tanker may have limited openings for entry and exit, unfavourable natural ventilation, and may not be designed for continuous worker occupancy. IMO (2006) states that these enclosed spaces include cargo tanks, fuel tanks, ballast tanks, cofferdams, slop tanks, inter-barrier spaces, void spaces and trunkings, pipelines or fittings connected to any of these (Figure 1). According to ISGOTT (1996: 130), “Confined spaces also include inert gas scrubbers and water seals, and any other items of machinery that are not routinely ventilated and entered such as boilers and main engine crank cases”. Fig. 1. Examples of Confined Spaces (IACS, 2007: 11) For personnel’s entry into confined spaces, it is the duty of the responsible officer to determine the atmosphere in the compartment, ventilate the space, and ensure that appropriate procedures are followed for the safety of the personnel concerned. He is authorized to issue an entry permit only when all the requirements are met (IMO, 2006). Hazards that may Arise from Entry into Enclosed Spaces on an Oil Tanker Respiratory Hazards There are several sources of respiratory hazards in enclosed spaces, such as contaminants in the form of organic vapours including aromatic hydrocarbons, benzene, toluene, etc; gases such as hydrogen sulphide, residues from inert gas and particulates such as those from welding operations, paint mists and asbestos. Respiratory hazards may be in the form of oxygen deficiency due to oxidation or rusting of bare steel surfaces, microbial activity or inert gas present in the enclosed space (ISGOTT, 1996). Hydrocarbon vapours are likely to be present in the enclosed spaces since cargo may have leaked into compartments, such as pump rooms, cofferdams, and tanks in proximity to those that have carried cargo. Cargo residues may have remained on the internal surfaces of tanks, even after cleaning and ventilation. Moreover, sludge and scale in a tank which has been tested and found gas free, may release further hydrocarbon vapour if disturbed or subjected to a rise in temperature (ISGOTT, 1996). Oxygen deficiency should be suspected in all enclosed spaces, specifically if they have contained water, have undergone damp or humid conditions, have contained inert gas or have been in close proximity to other inerted tanks (ISGOTT, 1996). Other atmospheric hazards that can impact closed spaces are toxic contaminants such as benzene or hydrogen sulphide which could remain in the space as residues from previous cargoes (ISGOTT, 1996). General Hazards Work undertaken in confined and enclosed spaces has greater potential of causing fatalities, severe injuries and illness than any other type of work conducted in shipyards or onboard ships. The main hazards related to confined spaces are: serious risk of fire or explosion, loss of consciousness from asphyxiation caused by gas, fumes, vapour or lack of oxygen; drowning as a result of increased water level; loss of consciousness brought about by increase in body temperature, suffocation caused by free flowing solid, inability to reach a breathable atmosphere due to entrapment. Confined and restrictive spaces which surveyors enter have narrow openings. Personnel suffering from claustophobia or those who are susceptible to panic attacks should not undertake work inside enclosed spaces that are cramped or difficult to access (IACS, 2007). Fire and Explosion Hazards Figure 2. shows how the flammable atmosphere is built up in a confined space, as a result of oxygen, heat and fuel in the form of gas, vapor or dust. Fig. 2. Flammable Atmosphere (IACS, 2007: 13) Electrostatic ignition can cause fire and explosions on tank vessels carrying petroleum products. According to the NFPA 77 (1988), static electrification and the numerous outcomes from positive and negative charges so formed may constitute a fire or explosive hazard. The generation of static electricity cannot be completely prevented, because it is inherently present at every interface. Static electricity is created when liquids move in contact with other materials, as when passing through pipes, or being mixed, poured, pumped, filtered, or otherwise agitated. Other reasons are the settling of solids or immiscible liquid in a liquid, The ejection of particles or droplets through a nozzle, and the splashing of a liquid against a solid surface. Static may accumulate in the liquid under particular circumstances such as in liquid hydrocarbons, resulting in the danger of subsequent sparking in a flammable vapour-air mixture (NFPA 77, 1988). Procedure to be Followed for Entry into an Enclosed Space Cargo tank atmosphere control needs to be undertaken by: inerting of empty tanks, loading cargo or ballast into tanks in an inert condition, conducting simultaneous cargo-ballast operations, maintaining a loaded passage, ballast passage, static electricity precautions, tank washing including crude oil washing, purging, gas freeing and preparation for tank entry (ISGOTT, 1996). Fig. 3. Gases that may be Found at Various Levels in a Confined Space (IACS, 2007: 17) In preparation for tank entry or before entering an empty enclosed space, it is necessary to take precautions. An entry permit has to be issued by a responsible officer to the personnel. Suitable notices should be placed for warning the personnel to take precautions for before entering the enclosed space. Immediately before entry and before providing the entry permit, the responsible officer has to ensure that the atmosphere inside the empty space is safe for entry in all respects (ISGOTT, 1996). Appropriate atmosphere checks should be carried out, for oxygen 21% by volume, hydrocarbon vapour concentration is not more than 1% LFL, and no toxic or other contaminants are present. Effective ventilation needs to be maintained continuously while the space is being occupied. Lifelines and harnesses need to be ready near the entrance to the confined space. Approved breathing apparatus and resuscitation equipment should also be readily available near the entrance. If possible, an alternative means of escape should be provided for an emergency. In direct contact with the responsible officer, and outside the enclosed space, a member of the crew should be in constant attendance. The lines of communication for dealing with emergencies should be clearly established and understood by all the concerned individuals (ISGOTT, 1996). Atmosphere checks should be carried out all the time the employee is in the enclosed space, and a full range of tests should be conducted before re-entry after a break. The use of personal detectors and carrying emergency escape breathing apparatus are recommended. If any of the conditions stated on the entry permit change, and the atmosphere in the confined space becomes unsafe, the personnel should be ordered to leave the space immediately. He should be allowed to re-enter only after the atmospheric check is done thoroughly, and safety is ensured (ISGOTT, 1996). Entering any space that has not been proved to be safe for entry, should be considered only in an emergency. In this highly hazardous situation the personnel involved should be well trained in the use of breathing apparatus, and should be aware of the dangers of removing their face masks while in the hostile atmosphere. As seen in Figure 3. some gases or vapours that are heavier than air will settle at the bottom of the confined space, while gases lighter than air will be found at the top of the confined space. Hence it is necessary to test all areas of a confined space, top, middle and bottom with properly calibrated testing instruments to determine the gases that are present. Atmospheres may be different in individual bays of the same tank. If testing reveals oxygen deficiency, flammable atmosphere or toxic gases or vapours, the space must be ventilated and re-tested before entering. Comparison of the properties of the possible gas with the molecular weight of air which is 28.8 mol, will help to determine whether the gas to be measured is lighter or heavier than air. It is essential that ventilation has been provided (IACS, 2007). Fig.4. Schematic Principles for Ventilation (AICS, 2007: 18) Figure 4. shows the scheme for ventilation. The air intake should be placed in an area that will draw in fresh air only. As far as possible, ventilation should be conducted continuously, because in many confined spaces the hazardous atmosphere will form again when the flow of air is stopped. All openings for ventilation and emergency exits should be kept open (IACS, 2007). To eliminate or minimize the hazard of static charge generation, certain precautions need to be applied. Restrict initial loading rates when splashing and surface turbulence appear. Keep water and other impurities out of the incoming cargo stream as much as possible. Degassing or inerting a ship’s tank removes loading rate restrictions due to static electricity. Clearing of cargo piping prevents cargo contamination and requires care. Steam cleaning should be avoided as far as possible because of cargoes in tanks. Various other precautions need to be taken: use of dry crude oil for washing, for overall loading, air injection precaution: minimizing the amount of air blown into the bottom of tank, and precaution for combination carriers: the holds should be pressed full to avoid the sloshing of a slack tank that would give rise to electrostatically charged mists. Further, preventive measures for charge accumulation should be adopted (Dyer, 2001). Specific guidelines are available to prevent hazards related to particular types of cargo carried by oil tankers which include: dangerous goods in packaged form, bulk liquid, solid bulk, and oxygen-depleting cargoes and materials (IMO, 2006a: 50). Conclusion This paper has highlighted the hazards that may arise when entering enclosed spaces on oil tankers, and has outlined the procedures to be followed for entry into an enclosed space. The levels of risk involved in the shipping of oil, especially while working in the enclosed spaces, are considered to be high due to the reasons found above. It is vital that the rules for safe entry into enclosed spaces should be thoroughly followed by all the personnel involved in the work, including the responsible officer. References Dyer, M.G. (2001). Static electric discharge hazard on bulk oil tank vessels. Phase I Report. Cambridge, Massachusetts. Retrieved on 27th March, 2009 from: http://www.enautica.pt/publico/Professores/Baptista/NT_I/Static_electric.pdf IACS (International Association of Classification Societies). (2007). Confined space safe practice. Retrieved on 27th March, 2009 from: http://www.iacs.org.uk/document/public/Publications/Guidelines_and_recommendations/PDF/REC_72_pdf212.pdf IMO (International Maritime Organization). (2006). Specialized training for oil tankers. Edition 2. London: International Maritime Organization. IMO (International Maritime Organization). (2006a). IMO Guidelines on ship recycling. London: International Maritime Organization Publications. ISGOTT. (1996). International Safety Guide for Oil Tankers and Terminals. 4th Edition. The International Chamber of Shipping (ICS), The Oil Companies International Marine Forum (OCIMF), and The International Association of Ports and Harbours. England: Witherby & Company Limited. NFPA 77 (National Fire Protection Association). (1988). Recommended practice on static electricity. Retrieved on 27th March, 2009 from: http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=77&cookie_test=1 Read More