TT Talk - Enclosed Spaces on ships - identify, test & monitor
No one involved in working on board an oil, gas or chemical tanker at sea or in port would remotely consider entering a tank on board without all the appropriate precautions being taken before and during entry, often also associated with a "Gas-Free Certificate" and a "Permit to Work" (or Enter). It would seem that the same safety awareness and the need to take appropriate precautions, amongst both shipboard and shore side personnel, is far less on general cargo, bulk and container ships.Many spaces on cargo ships are readily considered to be "enclosed", such as ballast tanks, void spaces, cofferdams, double bottoms and fuel tanks; suitable precautions are generally therefore taken.
"Contrarily, cargo holds themselves may tend not to be considered as enclosed or confined spaces"
Contrarily, cargo holds themselves may tend not to be considered as enclosed or confined spaces. Nevertheless, many sorts of cargo can emit hazardous vapours and fumes and others can deplete the oxygen content in the hold or space, below or above concentrations that are required to sustain life. Additionally, the trunkways and accesses to them, when not properly ventilated and checked for suitable atmospheres, have resulted in fatal incidents.
The impact of oxygen deficiency
In early 2017, the Hong Kong Marine Department issued an information note reminding personnel involved of the dangers, and steps to take before entry, following a multiple fatality related to a ship discharging "semi-coke". Two stevedores and a bulldozer driver died in the access trunkway to the cargo hold. Investigations established that the trunkway had not been ventilated sufficiently or the atmospheric conditions tested prior to entry, and the space was oxygen deficient.
This cargo is not the only one that can deplete the oxygen, and worse, replace it with denser than air vapours that sit at the bottom of such spaces. Coal and its derivatives, scrap metal, timber (especially with bark on, such as logs), fishmeal, grains, DRI and bio-mass all potentially have such properties. Many bulk and other cargoes are also fumigated.
In the Hong Kong incident, the access way was also marked with signage saying, "Ventilation Before Entry" and "O2 Depletion", but the warnings had been ignored by the stevedores before they climbed down the ladder. This might also indicate that appropriate training of all involved is insufficient.Ready informationThis is not a new problem; there have been many similar incidents, with single or multiple casualties involved so why are we not learning the lesson? It is certainly not for lack of information, UKP&I Club published its "Risk Focus: Enclosed Spaces", which includes a useful BowTie risk assessment and ICS published a document entitled "Guidance on Enclosed Space Entry and Rescue" some time ago. TT Club collaborated with ICHCA to produce pithy risk guidance and other organisations have done likewise.Ships comprise a shared workspace; all entities involved must share information and establish who is in control. Key elements for any risk assessment prior to activities that might affect the health and safety of personnel should include:
- Is it safe to enter the enclosed space?
- Who declares it safe?
- Who is charged with ensuring that it continues to be safe?
Normally it would be for someone with responsibility on board the ship to declare the space safe to enter. Be careful though; such a declaration was made a few years ago on a ship loading bio-mass in South America. Operations were suspended whilst the ship went back out to anchor. When it re-berthed a day later, the first stevedore down the ladder was asphyxiated.
passed in 2011
which sets out the precautions to be taken and contains a broad definition of what might constitute an "enclosed space":
"2.1 Enclosed Space means a space which has any of the following characteristics:1 limited openings for entry and exit;2 inadequate ventilation; and3 is not designed for continuous worker occupancy"
Continuing incidents led to further representation and deliberation at the IMO, where it was finally agreed that all ships should carry calibrated testing equipment to establish oxygen levels and detect the presence of hydrocarbons, for example (already applicable to tankers and similar ships).
"all ships should carry calibrated testing equipment to establish oxygen levels and detect [other gases]"
Similarly, the recently revised ILO Code of Practice for Safety and Health in Ports includes section 6.25 "Confined Spaces", going into considerable detail and supplementing the IMO guidance, which is aimed at the shipboard community. Furthermore, it should also be borne in mind that much larger "open" cargo spaces, such as ro-ro decks, can present a hazard from vehicle emissions; the ILO Code of Practice covers the salient points in section 9.1.7 "Emissions".
Take actionSo, ALL ships must carry suitable and calibrated testing equipment. However, any prudent shore based company should have its own equipment, properly and regularly calibrated and in order to perform checks before entering such a space. It should also be considered that conditions can change during a ship's stay in port and a risk assessment should determine whether periodic or continuous monitoring is necessary. "Wearable" monitoring devices are now easily available at relatively low cost.
"any prudent shore based company should have its own equipment, properly and regularly calibrated and in order to perform checks before entering [an enclosed] space"
The importance of repeated monitoring is represented by the example mentioned earlier, where a previously ventilated hold was temporarily closed as well as the possibility that a container might be leaking inside the hold. Containers themselves can also be considered to be "enclosed spaces" but that is considered in a parallel article [link].
We gratefully acknowledge the assistance in the preparation of this article of Capt Richard Brough OBE, Technical Advisor, ICHCA International.