The following are the general myths and misconceptions of Enclosed space entry : –
(1) Personal multigas meter can be used for testing of tank atmosphere, in absence of Portable multigas meter or in case the portable meter is non operational.
(2) In absence of sampling hose, the meter itself can be lowered into the tank to know the readings of various gases.
(3) It is OK to not know the permissible exposure limits of toxic gases like carbon monoxide and Hydrogen Suplhide. These gases are not there on my ship.
(4) Ballast tanks and fresh water tanks become safe for entry by taking in and pumping out water. No ventilation is required for such tanks.
(5) Manual Tank cleaning/sludge removal of crude oil cargo tank or fuel oil tank can be safely done if the oxygen content is satisfactory.
(6) Safety railing around the Ballast tank or crude oil cargo tank manhole is more of a hindrance and additional job.
(7) Measurements of Scrubber tower or Deck seal has to be done by putting the face inside.
(8) Entry into an air bottle, Aux. Boiler, EGB, Incinerator, Rudder trunk space, is always safe. No ventilation is required.
All of the above are myths and misconceptions. Some of the above are very basic and appears unbelievable, but they have been compiled on the basis of interaction with the personnel on board our ships.
The following are the clarifications and correct procedures : –
(1) Personal gas meters have no suction pump or limited capacity pump for taking in the air sample. It gives instantaneous values and there is no way to get the values at the bottom of the tank, because by the time it comes out of the tank it is already measuring the gas content of the external air. Sampling hose may be used, but then the aspirator bulb has to be used a number of times, as per maker’s instruction, to get the sample from the bottom of the tank. The number of aspirations are dependent on the depth of the tank.
(2) The permissible exposure limits are written on the enclosed space entry permit form and it is advisable to know the same for gases like H2S and CO. The enclosed space entry permit form gives details of the toxic gases and their PEL.
(3) Ballast tanks and FW tanks do not become safe for entry, just be ballasting/deballasting. There remains a possibility of unventilated areas, oxygen deficient pockets due to rusting of steel, that may be hazardous for entry.
(4) Absence of safety railing around the ballast tank, cargo tank manhole, provides a potential source of imminent fall into the tank, while working around, or during entry exit. The provision of the safety railing prevents such accidents.
(5) Scrubber tower and Deck seal are very hazardous in terms of leaking deck valves causing accumulation of cargo vapours/inert gas. This may also be caused by inadequate isolation, leaking non return flap valve. The face must be kept away while testing the atmosphere of the deck seal and scrubber.
(6) Air bottle, Aux. Boiler, EGB, Incinerator, Rudder trunk space have equal potential for human injury due to lack of oxygen, if adequate gas measurement is not done. Air bottle, Aux boiler, Incinerator may have flammable mixtures and toxic gases also. These spaces must be treated with equal importance and potential for affecting humans.
All of you are hereby advised to ensure compliance with the requirements of SOLAS w.r.t RESCUE DRILL from ENCLOSED SPACES. It was very disheartening to note that one vessel was doing this drill from non-enclosed spaces. Also, one vessel was using personal gas meter to test the tank atmosphere, without any sampling hose, by lowering it into the tank and expecting it to give the reading at the bottom of the enclosed space, when it is pulled out.
If you have any additional inputs on the subject matter, please feel free to communicate. The knowledge and awareness is the most primitive and basic step towards preventing accidents/incidents. The next step is the utility of the knowledge and application to the day-to-day activities.