Enclosed Space entry procedures described in Company SMS and differ from company to company.
Below are common key points:
- The space should be thoroughly ventilated throughout.
- An ‘Enclosed Space Entry Permit’ must be issued before entry.
- Risk Assessment must be conducted and all risks and hazards identified and controlled down to the acceptable maximum.
- Toolbox meeting must be conducted to familiarize all participants with the task.
- Entry List should be filled in and placed at the tank/space entrance
- The space should be tested for sufficient oxygen, that it is free of hydrocarbons and toxic vapors.
- Entry team must carry portable gas analyzer to constantly monitor the atmosphere in the space
- The officers on watch, on the deck, in the engine room, or the cargo control room should be informed, as necessary, of any space that is to be entered so that they do not, for example, stop fans, start equipment or open valves by remote control, close escape doors or pump cargo or ballast into the space and appropriate warning notices should be placed on the relevant controls or equipment. Where necessary pumping operations or cargo movements should be suspended when entry is being made into a dangerous space.
- All necessary safety equipment should be readily available. BA, safety lines etc.
- At least one man should be standing by at the top of the tank during entry.
- Ventilation must be maintained at all times with personnel inside the space.
When opening the entrance to a dangerous space care should be taken to avoid the effects of a possible release of pressure or vapor from the space.
Space should be isolated and secured against the ingress of dangerous substances by blanking off pipelines or other openings or by closing valves or by removing and blanking off a section of pipe. Valves should then be tied or some other means used to indicate that they are not to be opened.
If necessary, space should be cleaned or washed out to remove as far as practicable any sludge or other deposit liable to give off dangerous fumes.
Space should be thoroughly ventilated by either natural or mechanical means to ensure (by testing) that all harmful gases are removed and no pockets of oxygen deficient atmosphere remain.
Compressed oxygen should not be used to ventilate any space.
Testing of a space should be carried out only by persons trained in the use of the equipment.
Testing should be carried out before entry and at regular intervals thereafter. If possible the testing of the atmosphere before entry should be made by remote means and the testing carried out at different levels.
Identifying Potential Hazards
Oxygen Deficiency
If an empty tank or other confined space has been closed for a time the oxygen content may have been reduced due to the oxygen combining with steel in the process of rusting.
Lack of oxygen may occur in boilers or other pressure vessels particularly where oxygen absorbing chemicals have been used to prevent rusting.
Depletion of oxygen may occur in cargo spaces when oxygen absorbing cargoes, are or have been carried.
Oxygen deficiency can also occur in cargo holds e.g. when carrying ore concentrates even though the hatch covers have been removed and the discharge of cargo has commenced.
After discharge of volatile cargoes, sufficient vapors may remain in tanks to cause oxygen deficiency.
Hydrogen may occur in a cathodically-protected cargo tank used for ballast. Pockets of hydrogen may exist in the upper parts of the compartment, displacing the oxygen (as well as creating a possible explosion hazard).
If carbon dioxide, steam or other fire extinguishing chemical has been discharged to extinguish or prevent a fire, the oxygen content of the space would be reduced.
The use of inert gas in the cargo tanks of tankers and gas carriers or in the inter-barrier spaces of gas carriers results in only minimal amounts of oxygen being present.
Toxicity Of Oil Cargoes
Hydrocarbon gases are flammable as well as toxic and may be present in fuel or cargo tanks which have contained crude oil or its product.
Hydrocarbon gases or vapors may also be present in pump rooms and cofferdams, duct keels or other spaces adjacent to cargo tanks due to the leakage of cargo.
The components in the vapor of some oil cargoes, such as benzene and hydrogen sulfide are very toxic.
Toxicity Of Other Substances
Cargoes carried in chemical tankers or gas carriers may be toxic.
There is the possibility of risk of leakage from drums of chemicals or other packages of dangerous goods where there has been mishandling or incorrect stowage or damage due to heavy weather.
The trace components in the inert gas such as carbon monoxide, sulfur dioxide, nitric oxide and nitrogen dioxide are very toxic.
The interaction of vegetables or animal oils or sewage with sea water may lead to the release of hydrogen sulfide which is very toxic.
Hydrogen sulfide or other toxic gases may be generated where the residue of grain or similar cargoes permeates into or chokes bilge pumping systems.
The chemical cleaning, painting or the repair of tank coatings may involve the release of solvent vapors.
Procedures And Arrangements Before Entry
Access to and within the space should be adequate and well illuminated.
No matches, welding or flame cutting equipment, electrical equipment or other sources of ignition should be taken or put into the space unless the master or responsible officer is satisfied that it is safe to do so.
In all cases, rescue and available resuscitation equipment should be positioned ready for use at the entrance to the space. Rescue equipment means breathing apparatus together with fully charged spare cylinders of air, lifelines and rescue harnesses and torches or lamps, approved for use in the flammable atmosphere, if appropriate. A means of hoisting an incapacitated person from the confined space should also be readily available when appropriate.
The number of persons entering the space should be limited to those who actually need to work in the space and who could be rescued should an emergency occur.
At least one attendant should be detailed to remain at the entrance to the space whilst it is occupied.
A system of communication should be agreed and tested by all involved to ensure that any person entering the space can keep in touch with the person stationed at the entrance. The communication between the link person at the space entrance and the party inside the space must be tested on a regular basis.
A system of communication should be established between the attendant at the entrance to the space and the officer on watch.
The extent to which the use of breathing apparatus or life or rescue harnesses would cause any difficulty of movement within any part of the space, or would cause problems for any incapacitated person who had to be removed from the space, should also be examined.
Lifelines of rescue harnesses should be long enough for the purpose and be easily detachable by the wearer should they become entangled, but should not otherwise come away from the rescue harnesses.
A "Block and tackle" should be mounted adjacent to the space entrance, to be used in the removal of a casualty, in the event of an accident.
Procedures And Arrangements During Entry
Ventilation should continue during the period that the space is occupied and during temporary breaks. In the event of a failure of the ventilation system any persons in the space should leave immediately.
The atmosphere should be tested periodically whilst the space is occupied and persons should be instructed to leave the space should there be any deterioration in the conditions.
If unforeseen difficulties or hazards develop, the work in the space should be stopped and the space evacuated so that the situation can be reassessed.
If a person in a space feels in any way adversely affected he should give the pre-arranged signal to the attendant standing by the entrance and immediately leave the space.
When available a rescue harness should be worn to facilitate recovery in the event of an accident.
Should an emergency occur the general (or crew) alarm should be sounded so that the back-up is immediately available to the rescue team.
Additional Requirements For Entry Into A Space Where The Atmosphere Is Suspect Or Known To Be Unsafe
If the atmosphere is considered to be suspect or unsafe to enter without breathing apparatus, then the space should only be entered if it is essential for testing purposes, the working of the ship, for the safety of life or for the safety of the ship. The number of persons entering the space should be the minimum compatible with the work to be performed.
Breathing apparatus should always be worn. Respirators cannot be used.
Where remote testing of the space is not reasonably practicable, or where a brief inspection only is required, a single air supply may be acceptable provided a prolonged presence in the space is not required and the wearer of the breathing apparatus is so situated that he can be hauled out immediately in case of emergency.
Rescue harnesses should be worn. Wherever practicable lifelines should be used. Lifelines should be attended by a person stationed at the entrance who has been trained how to pull an unconscious person from a dangerous space. Where the dangerous space to be entered requires the possible use of hoisting equipment to effect rescue, arrangements should be made to ensure that persons would be available to operate it as soon as necessary.
When appropriate, portable lights and other electrical equipment should be of a type approved for use in a flammable atmosphere.
Should there be any hazard due to chemicals, whether in liquid, gaseous or vapour form, coming into contact with the skin and/or eyes then protective clothing should be worn.
